Ocean Habitats and their Biota

Ocean Habitats and their Biota

13-1. Biology of the Continental Shelf

A. The waters of the neritic zone (over the continental shelf) are fertile and support a rich community of organisms.

1. The plankton are floaters and weak swimmers which are helplessly transported by ocean currents.

a. Phytoplankton: photosynthetic

b. Zooplankton: not photosynthetic

c. Sorted by size: pico, micro, etc… KNOW THESE

2. Nekton have the ability to swim against currents and actively search for a more hospitable environment.

B. Because the water column is shallow in the sublittoral zone (intertidal), physical factors regulate the number, type, and distribution of benthic (bottom dwellers) organisms.

1. Bottom energy is a function of wave energy and tidal currents and these vary inversely with depth.

2. The sea floor can be divided into two areas based upon the energy of the environment: High energy environments and Low energy environments.

3. Bottom energy affects organisms by: moving sediment about and creating an unstable substrate, controlling sediment size.

4. Bottom sediment strongly influences the feeding mode of benthic communities.

5. The two major benthic communities based upon substrate are: Hard-bottom community and Soft-bottom community

13-2. Biology of the Open Ocean and the Deep Sea

C. The open ocean (pelagic zone) is the largest habitat on Earth, but life is sparse because of low nutrient concentration and great depth (lack of light).

1. In the open ocean, diversity is high but the number of individuals per species is low.

2. The only seaweed in the open ocean sea is sargassum gulfweed. It floats.

3. The major phytoplankton are diatoms, dinoflagellates and coccolithophores and the major zooplankton are foraminifera and radiolaria.

a. Diatoms dominate the shallow coasts, but decrease in abundance seaward.

4. Top predators are mackerel, squid, jellyfish, tuna, porpoise, shark, and man.

5. In the dysphotic zone (partial light), seasonal heating is minimal and conditions tend to be uniform most of the year.

6. The aphotic zone is an area of permanent darkness and cold.

D. The biomass on the sea floor tends to decrease with depth faster than it does with distance from shore.

1. The benthic food chains largely depend upon food from the surface that reaches the bottom.

2. Characteristics of the benthic organisms include: year-round reproduction, smaller broods, slow growth, and longer life.

3. Diversity of the benthos is greater than expected because the high predation rate prevents any group from dominating through competitive exclusion (when one group out-competes most others and drives them to extinction).

4. Four traits common to all abyssal depths are: perpetual darkness, low temperature, high hydrostatic pressure, and sparse food supply.

5. Rate of bacterial decay is greatly reduced under high hydrostatic pressure.

a. This means that organic material that settles onto the sea floor remains for a long time before it decays and is thus more likely to be consumed.

E. Abundant communities form around volcanic vents on the crest of mid-ocean ridges, such as the Galapagos Ridge.

1. Water heated by magma flows through a fracture, and leeches metals from the basalts. Later, when the water cools, it precipitates sulfide and sulfate minerals, forming chimneys.

2. Bacteria from the vents perform chemosynthesis, oxidizing hydrogen sulfide to synthesize food.

3.Filter-feeding invertebrates around the vent depend on chemosynthetic bacteria for food.

The Planet Oceanus

2-1. The Earth’s Structure

A. The compositional layers of the Earth are the Crust, the Mantle, and the Core. The Core is subdivided into a molten outer core and solid inner core. KNOW THE THICKNESSES.

B. Physical state is determined by the combined effects of pressure and temperature.

1. Increasing pressure raises the melting point of a material.

2. Increasing temperature provides additional energy to the atoms and molecules of matter allowing them to move farther apart, causing the material to melt.

3. Both pressure and temperature increase toward the center of the Earth, but at different rates.

4. Divisions of the Earth based upon physical state are the Lithosphere, The Asthenosphere, the Mesosphere, the Outer core, and the Inner core (NEED TO KNOW CHARACTERISTICS AND THICKNESS OF EACH)

D. Three fluid spheres surround the rocky portion of the Earth.

1. Hydrosphere includes all of the "free" water of the Earth contained in the ocean, lakes, rivers, snow, ice, water vapor, and groundwater. 97% saltwater, 2% frozen in ice caps, 1% free freshwater

2. Atmosphere surrounds the Earth and is mainly a mixture of nitrogen and oxygen.

3. Biosphere refers to all living and non-living organic matter.

2-2. The Physiography of the Ocean Floor

E. Physiography and bathymetry (submarine landscape) allow the sea floor to be subdivided into three distinct provinces: continental margins, deep ocean basins and midoceanic ridges.

1. Continental margins are the submerged edges of the continents and consist of massive wedges of sediment eroded from the land and deposited along the continental edge. The continental margin is divided into three parts: the Continental shelf, the Continental slope, and the Continental rise.

2. Deep Ocean Province is between the continental margins and the midoceanic ridge and includes a variety of features from mountainous to flat plains: Abyssal plains, Abyssal hills, Seamounts, and Deep-sea trenches

3. Midoceanic Ridge Province consists of a continuous submarine mountain range that covers about one third of the ocean floor and extends for about 60,000 km/36,000miles around the Earth.

2-3. Geologic Differences between Continents and Ocean Basins

F. Continents and ocean basins differ in composition, elevation, and physiographic features.

1. Elevation of Earth’s surface displays a bimodal distribution with about 29% (not 30%) above sea level and much of the remainder at a depth of 4 to 5 kilometers below sea level. Very little in the productive region of shallow depths where light is.

2. Continental crust is mainly composed of granite, a light colored, lower density (2.7 gm/cm3) igneous rock rich in aluminum, silicon and oxygen.

3. Oceanic crust is composed of basalt, a dark colored, higher density (2.9 gm/cm3) volcanic rock rich in silicon, oxygen and magnesium.

4. The Moho is the boundary between rocks of the crust and the denser (3.3 gm/cm3) rocks of the mantle.

G. Isostasy refers to the balance of an object "floating" upon a fluid medium. Height of the mass above and below the surface of the medium is controlled by the thickness of the mass and its density (similar to ice floating in water).

1. Greater the density of the mass, the lower it will sink in the medium.

2. Greater the thickness of the mass, the higher a portion of it will rise above the medium.

3. Continents are thick (30 to 40 km), have low density, and rise high above the supporting mantle rocks (aethenosphere)

4. Sea floor is thin (4 to 10 km), has greater density and does not rise as high above the mantle.

PLATE MOVMENTS

3-1. Continental Drift

A. Based upon the fit of continental outlines and fossil and geologic evidence, Alfred Wegner proposed his hypothesis of continental drift. According to Wegner, the continents are sections of a past super continent called Pangea, which broke apart and the fragments plowed through the oceanic crust,.to their present locations. KNOW THE OTHER PLAYERS IN THE MOVEMENT OF CONTINENTS.

3-2. Sea-Floor Spreading: Divergent plates

B. Sea floor spreading demonstrates that the sea floor moves apart at the oceanic ridges and new oceanic crust is added to the edges.

1. Rift valleys along oceanic ridge crests indicate tension, are bounded by normal faults, and are floored by recently-erupted basaltic lava flows.

2. Axis of the oceanic ridge is offset by transform (strike-slip) faults which produce lateral displacement.

3. Whereas oceanic ridges indicate tension (pulling), continental mountains indicate compressional forces are squeezing the land together (pushing).

C. The geomagnetic field is the magnetic field of the Earth.

1. Magnetometers detect and measure Earth’s magnetic field.

2. Moving across the ocean floor perpendicularly to the oceanic ridges, magnetometers alternately record stronger (positive) and weaker (negative) magnetic fields (called magnetic anomalies) in response to the influence of the sea floor rocks.

3. Magnetic anomalies and the rocks causing them form parallel bands arranged symmetrically about the axis of the oceanic ridge.

4. As basaltic rocks crystallize, some minerals align themselves with Earth’s magnetic field, as it exists at that time, imparting a permanent magnetic field, called paleomagnetism, to the rock.

5. Periodically Earth’s magnetic field polarity (direction) reverses poles. HOW OFTEN.

D. Because of their paleomagnetism, rocks of the sea floor influence the magnetic field recorded by magnetometers.

1. Rocks on the sea floor with normal polarity paleomagnetism locally reinforce Earth’s magnetic field making it stronger and producing a positive anomaly.

2. Rocks on the sea floor with reverse paleomagnetism locally weaken Earth’s magnetic field, producing a negative anomaly.

3. Rocks forming at the ridge crest record the magnetism existing at the time they solidify.

4. Sea floor increases in age away from the ridge and is more deeply buried by sediment because sediments have had a longer time to collect.

5. Rates of sea-floor spreading vary from 1 to 10 cm per year for each side of the ridge and can be determined by dating the sea floor and measuring its distance from the ridge crest.

6. Continents are moved by the expanding sea floor.

3-3. Global Plate Tectonics

E. Because Earth’s size is constant, expansion of the crust in one area requires destruction of the crust elsewhere.

1. Currently, the Pacific Ocean basin is shrinking as other ocean basins expand.

2. Destruction of sea floor occurs in subduction zones.

3. Seismicity is the frequency, magnitude, and distribution of earthquakes. Earthquakes are concentrated along oceanic ridges, transform faults, trenches and island arcs.

4. Tectonism refers to the deformation of Earth’s crust.

5. Benioff Zone is an area of increasingly deeper seismic activity, inclined from the trench downward in the direction of the island arc.

d. Subduction is the process at a trench whereby one part of the sea floor plunges below another and down into the asthenosphere (crust is melted).

F. Earth’s crust is composed of a series of lithospheric plates.

1. Plate edges are trenches, oceanic ridges, and transform faults.

2. Seismicity and volcanism are concentrated along plate boundaries.

3. Movement of plates is caused by thermal convection of the "plastic" rocks of the asthenosphere which drag along the overlying lithospheric plates.

4. Mantle plumes originate deep within the asthenosphere as molten rock which rises and melts through the lithospheric plate forming a large volcanic mass at a "hot spot." (Island arcs: Hawaii)

G. Wilson Cycle refers to the sequence of events leading to the formation, expansion, contracting and eventual elimination of ocean basins.

- Stages in basin history are:

1. Embryonic—rift valley forms as continent begins to split.

2. Juvenile—sea floor basalts begin forming as continental sections diverge.

3. Mature—broad ocean basin widens, trenches develop, and subduction begins.

4. Declining—subduction eliminates much of sea floor and oceanic ridge.

5. Terminal—last of the sea floor is eliminated and continents collide forming a continental mountain chain.

4-1. Sediment in the Sea

A. Size classification divides sediments by grain size into gravel, sand, and clay (largest to smallest).

1. Mud is a mixture of silt and clay.

2. Origin classification divides sediment into five categories: Terrigenous sediments, Biogenous sediments, Hydrogenous sediments, Volcanogenic sediments, and Cosmogenic sediments.

B. Factors that control sedimentation include particle size and the turbulence of the deposition environment.

1. Terrigenous sediments strongly reflect their source and are transported to the sea by wind, rivers, and glaciers.

2. Rate of erosion is important in determining nature of sediments.

3. Average grain size reflects the energy of the depositional environment.

4. Hjulstrom’s Diagram graphs the relationship between particle size and energy for erosion, transportation, and deposition.

4-2. Sedimentation in the Ocean

A. Based upon water depth, the ocean environment can be divided into the shelf, which is shallow and near a terrigenous source, and the deep ocean basin, which is deep and far from a terrigenous source.

B. Shelf sedimentation is strongly controlled by tides, waves and currents, but their influence decreases with depth.

1. Shoreline turbulence prevents small particles from settling and transports them seaward where they are deposited in deeper water.

2. Particle size decreases seaward for recent sediments.

3. Past fluctuations of sea level has stranded coarse sediment (relict sediment) across the shelf including most areas where only fine sediments are deposited today as the oceans expand in size.

C. Worldwide distribution of recent shelf sediments by composition is strongly related to latitude and climate.

1. Calcareous biogenous sediments dominate tropical shelves.

2. River-supplied sands and muds dominate temperate shelves.

3. Glacial till and ice-rafted sediments dominate polar shelves.

D. Geologic controls of continental shelf sedimentation must be considered in terms of a time frame.

1. For a time frame up to 1000 years, waves, currents, and tides control sedimentation.

2. For a time frame up to 1,000,000 years, sea level lowered by glaciation controlled sedimentation and caused rivers to deposit their sediments at the shelf edge and onto the upper continental slope.

3. For a time frame up to 100,000,000 years, plate tectonics have determined the type of margin that developed and controlled sedimentation.

E. If influx of terrigenous sediment is low and the water is warm, carbonate sediments will dominate.

F. Deep-sea Sedimentation has two main sources for sediment: terrigenous material from the land and biogenous and hydrogenous from the sea.

1. Major sedimentary processes in the deep-sea include:, Bulk emplacement, Debris flows, Turbidity currents

2. Major pelagic sediments are red clay and biogenous oozes (silaceous and calcareous).

3. Hydrogenous deposits are chemical and biochemical precipitates that form on the sea floor and include ferromanganese nodules and phosphorite.

G. The distribution of sediments in the deep ocean varies greatly, but is strongly controlled by the compensation depth.

1. Surface Deposits are the sediments found exposed on the sea floor.

2. Deep-sea stratigraphy refers to the broad-scale layering of the sediments of the sea floors.

5-1. Basic Chemical Notions

A. Atoms are the smallest unit which display all of the properties of the material.

1. Electrically stable atoms have the same number of electrons as protons.

2. Ions are atoms with either more or less electrons than protons and are therefore electrically charged.

3. Isotopes are atoms containing the same number of protons, but different numbers of neutrons and therefore have different weights.

5-2. Basic Physical Notions

B. Heat results from the vibrations of atoms (kinetic energy) and can be measured with a thermometer.

1. In solids, the atoms or molecules vibrate weakly and are rigidly held in place.

2. In liquids, the atoms or molecules vibrate more rapidly, move farther apart, and are free to move relative to each other.

3. In gases, the atoms or molecules are highly energetic, move far apart, and are largely independent.

4. Melting is the transition from solid to liquid; freezing is the reverse.

5. Evaporation (vaporization) is the transition from liquid to gas; condensation is the reverse.

6. Temperature controls density. As temperature increases, atoms or molecules move farther apart and density (mass/volume) decreases because there is less mass (fewer atoms) in the same volume.

Water is most dense at 4C or Sea water at 2C

5-3. The Water Molecule

C. The water molecule is unique in structure and properties.

1. H2O is the chemical formula for water.

2. Unique properties of water include:

a. Higher melting and boiling point than other hydrogen compounds (hydrogen bonding)

b. High heat capacity (specific heat), amount of heat needed to raise the temperature of one gram of water 1oC. This limits the changes in temperature of the water compared to air and land and explains why the air over the ocean heats up more slowly than the air over land thus Raleigh is warmer in the summer than Wilmington and yet it is colder than Wilmington in the winter.

c. Greater solvent power than other substances due to its small size and polarity.

3. Water molecules are asymmetrical is shape with the two hydrogen molecules at one end, separated by 105o when in the gaseous or liquid phase and 109.5o when ice.

4. Asymmetry of a water molecule and distribution of electrons result in a dipole structure with the oxygen end of the molecule negatively charged and the hydrogen end of the molecule positively charged.

5. Dipole structure of water molecule produces an electrostatic bond (hydrogen bond) between water molecules which cluster together in a hexagonal (six-sided) pattern.

6. Ice floats in water because all of the molecules in ice are held in hexagons and the center of the hexagon is open space, making ice 8% less dense than water.

7. Water reaches its maximum density at 3.98oC. (Sea water 2 C)

a. Below this temperature increasing numbers of water molecules form hexagonal polymers (lattice structure of ice) and decrease the density of the water.

b. Above this temperature water molecules are increasingly energetic and move farther apart, thereby decreasing density.

8. Hydrogen bonding is responsible for many of the unique properties of water because more energy is required to break the hydrogen bonds and separate the water molecules.

9. Water dissolves salts by surrounding the atoms in the salt molecule and neutralizing the ionic bond holding the molecule together. Dissolved salts form cations (positively charged ions) and anions (negatively charged ions).

a. The process of water surrounding an ion is called hydration.

D. Seawater consists of water with various materials dissolved within it.

1. The solvent is the material doing the dissolving and in seawater it is the water.

2. The solute is the material being dissolved.

3. Salinity is the total amount of salts dissolved in the water.

a. It is measured in parts of salt per thousand parts of salt water and is expressed as ppt (parts per thousand) or abbreviated 0/00.

4. Average salinity of the ocean is about 35 0/00. Brackish water is about 15 ppt.

E. 99% of all the salt ions in the sea are sodium (Na+), chlorine (Cl-), sulfate (SO4-2), Magnesium (Mg+2), calcium (Ca+2) and potassium (K+).

1. Sodium and chlorine alone comprise about 86% of the salt in the sea.

2. The major constituents of salinity display little variation over time and are a conservative property of seawater. (Law of Constant Proportions)

F. Nutrients are chemicals essential for life.

1. Major nutrients in the sea are compounds of nitrogen, phosphorus, and silicon.

2. Because of usage, nutrients are scarce at the surface and their concentrations are measured in parts per million (ppm). Limiting factor for primary production in the open ocean along with light.

3. Concentration of nutrients varies greatly over time and because of this they are considered a nonconservative property of the sea.

G. In order of decreasing abundance the major gases in the sea are nitrogen, oxygen, carbon dioxide and the noble gases, argon (Ar), neon (Ne) and helium (He).

H. Trace elements occur in minute quantities and are measured in parts per million (ppm) or parts per billion (ppb), but even in small quantities they are important in either promoting life or killing it. Fe is needed in hemoglobin, Mg is needed in chlorophyll. Cu is in Hemocyanin.

5-4. Salinity

A. Salinity is the total mass, expressed in grams, of all substances dissolved in one kilogram of seawater when all carbonate has been converted to oxide, all bromine and iodine has been replaced by chlorine and all organic compounds have been oxidized at a temperature of 480oC.

1. Principle of constant proportion states that the absolute amount of salt in seawater varies, but the relative proportions of the ions are constant.

a. Because of this principle, it is necessary to test for only one salt ion, usually chlorine, to determine the total amount of salt present.

2. Chlorinity is the amount of halogens (chlorinity, bromine, iodine, and fluorine) in the seawater and is expressed as grams/kilogram or 0/00.

3. Salinity is equal to 1.8065 times chlorinity.

4. Salinometers determine salinity from the electrical conductivity produced by the dissolved salts.

B. Salinity in the ocean is in a steady-state condition because the amount of salt added to the ocean (input from source) equals the amount removed (output into sinks).

1. Salt sources include weathering of rocks on land and the reaction of lava with seawater.

a. Weathering mainly involves the chemical reaction between rock and acidic rainwater, produced by the interaction of carbon dioxide and rainwater forming carbonic acid.

2. Salt sinks include the following:

a. Evaporation removes only water molecules.

i. Remaining water becomes increasingly saline, eventually producing a brine.

ii. If enough water evaporates, the brine becomes supersaturate and salt deposits begin to precipitate forming evaporite minerals.

b. Wind-blown spray carries minute droplets of saltwater inland.

c. Adsorption of ions onto clays and some authigenic minerals.

d. Shell formation by organisms.

3. Lack of similarity between relative composition of river water and the ocean is explained by residence time, average length of time that an ion remains in solution in the ocean. KNOW RESIDENCE TIMES OF WATER AND MAJOR IONS

a. Ions with long residence times tend to accumulate in the sea, whereas those with short residence times are removed.

b. Rapid mixing and long residence times explain constant composition of seawater.

C. Addition of salt modifies the properties of water.

1. Pure water freezes at 0oC. Adding salt increasingly lowers the freezing point because salt ions interfere with the formation of the hexagonal structure of ice. Freezing point of seawater is –2C.

2. Density of water increases as salinity increases. Salt water is easier to float in.

3. Vapor pressure is the pressure exerted by the gaseous phase on the liquid phase of a material. It is proportional to the amount of material in the gaseous phase.

a. Vapor pressure decreases as salinity increases so salt ions reduce the evaporation of water molecules.

5-5. Chemical and Physical Structure of the Oceans

A. Ocean surface temperature strongly correlates with latitude because insolation, the amount of sunlight striking Earth’s surface, is directly related to latitude.

1. Ocean isotherms, lines of equal temperature, generally trend east-west except where deflected by currents.

a. Ocean currents carry warm water poleward on the western side of ocean basins warm water currents and cooler water equatorward on the eastern side of the ocean (cold water currents.

2. Insolation and ocean-surface water temperature vary with the season.

3. Ocean temperature is highest in the tropics (25oC) and decreases poleward.

4. Tropical and subtropical oceans are permanently layered with warm, less dense surface water separated from the cold dense deep water originating at the poles by a thermocline, a layer in which water temperature and density change rapidly.

a. Tropical oceans have a constant thermocline, temperate regions have a seasonal thermocline, and polar regions have none.

B. Salinity displays a latitudinal relationship related to precipitation and evaporation.

1. Highest ocean salinity is between 20-30o north and south or the equator.

2. Low salinity at the equator and poleward of 30o results because evaporation decreases and precipitation increases.

3. In some places surface water and deep water are separated by a halocline, a zone of rapid change in salinity.

4. Water stratification (layering) within the ocean is more pronounced between 40oN and 40oS.

C. Density of seawater is a function of temperature, salinity and pressure.

1. Density increases as temperature decreases and salinity increases as pressure increases.

2. Pressure increases regularly with depth, but temperature and salinity are more variable.

3. Higher salinity water can rest above lower salinity water if the higher salinity water is sufficiently warm and the lower salinity water sufficiently cold.

4. Pycnocline is a layer within the water column where water density changes rapidly with depth.

D. The water column in the ocean can be divided into the surface layer, pycnocline and deep layer.

1. The surface layer is about 100m thick, comprises about 2% of the ocean volume, and is the most variable part of the ocean because it is in contact with the atmosphere.

a. The surface layer is less dense because of lower salinity or higher temperature.

2. The pycnocline is transitional between the surface and deep layers and comprises 18% of the ocean basin.

a. In the low latitudes, the pycnocline coincides with the thermocline, but in the mid-latitudes it is the halocline.

3. The deep layer represents 80% of the ocean volume.

a. Water in the deep layer originates at the surface in high latitudes where it cools, becomes dense, sinks (convects) to the sea floor and flows outward (advects) across the ocean basin.

5-6. Gases in Seawater

A. The solubility and saturation value for gases in seawater increase as temperature and salinity decrease and as pressure increases (Henry’s Law)

1. Solubility is the ability of something to be dissolved and go into solution.

2. Saturation value is the equilibrium amount of gas dissolved in water at an existing temperature, salinity, and pressure.

a. Water is undersaturated when it has the capacity to dissolve more gas.

b. Water is saturated when under existing conditions it contains as much dissolved gas as it can hold in equilibrium. Gas content is at saturation value.

c. Water is supersaturated when under existing conditions it contains more dissolved gas than it can hold in equilibrium. Gas content is above saturation value and excess gas will come out of solution.

3. The surface layer is usually saturated in atmospheric gases because of direct exchange with the atmosphere.

4. Below the surface layer, gas content reflects relative importance of respiration, photosynthesis, decay, and gases released from volcanic vents.

B. Oxygen tends to be abundant in the surface layer and deep layer bottom, but lowest in the pycnocline.

1. Surface layer is rich in oxygen because of photosynthesis and contact with the atmosphere.

2. Oxygen minimum layer occurs at about 150 to 1500m below the surface and coincides with the pycnocline.

a. Sinking food particles settle into this layer and become suspended in place because of the greater density of the water below.

b. The food draws large numbers of organisms which respire, consuming oxygen.

c. Decay of uneaten material consumes additional oxygen.

d. Density difference prevents mixing downward of oxygen-rich water from the surface or upwards from the deep layer.

3. The deep layer is rich in oxygen because its water is derived from the cold surface waters which sank (convect) to the bottom. Consumption is low because there are fewer organisms and less decay consuming oxygen.

4. Anoxic waters contain no oxygen and are inhabited by anaerobic organisms (bacteria).

C. Carbon dioxide is of major importance in controlling acidity in the seawater.

1. Major sources of carbon dioxide are respiration and decay.

2. Major sinks are photosynthesis and construction of carbonate shells.

3. Carbon dioxide controls the acidity of seawater.

a. A solution is acid if it has excess H+ (hydrogen) ions and is a base if it has excess OH- (hydroxyl) ions.

b. pH is related to the amount of CO2 dissolved in water because it combines with the water to produce carbonic acid which releases H+ ions.

CO2 + H2 -> H2CO3 -> H+ + HCO3 -> H+ + CO3-2

c. H2CO3 is carbonic acid, HCO3- is a bicarbonate ion, and CO3-2 is the carbonate ion.

d. Changing the amount of CO2 shifts the reaction to either the right or left of the equation.

i. Adding CO2 shifts the reaction to the right and produces more H+ ions making the water more acid.

ii. Removing CO2 shifts the reaction to the left, combining H+ ions with carbonate and bicarbonate ions reducing the acidity.

e. Dissolved CO2 in water (bicarbonate ions often play this part) acts as a buffer, a substance that prevents large shifts in pH.

f. Dissolution of carbonate shells in deep water results because cold water under great pressure has a high saturation value for CO2 and the additional CO2 releases more H+ ions making the water acid.

g. Warm, shallow water is under low pressure, contains less dissolved CO2 and is less acidic. Carbonate sediments are stable and do not dissolve. Average pH of ocean water is around 8.

5-7. The Ocean as a Physical System

A. Water is recycled from the ocean to the land and returned to the sea.

1. The reservoirs of water include:

a. Oceans— cover 60% of the Northern Hemisphere and 80% of the Southern Hemisphere (71% overall) and contains 97% of Earth’s water.

b. Rivers, lakes and glaciers (includes ice caps)

c. Groundwater—contains a larger volume of water than all of the water in lakes and rivers.

2. The hydrologic cycle describes the exchange of water between ocean, land, and atmosphere.

a. On land precipitation exceeds evaporation.

b. In the ocean evaporation exceeds precipitation.

3. The ocean is part of a biogeochemical system in which land undergoes weathering and weathered products are transported to the sea where they may be deposited directly or used by organisms and later deposited as organic remains or organic wastes. Deposits are buried, lithified, and recycled by plate tectonics into new land which is weathered and the cycle repeats.

The Ocean Sciences: Chemical Techniques

A. Water samples must be collected in inert containers and isolated as they are recovered so as to prevent contamination.

1. The Nansen bottle has valves at each end which are automatically closed when a weight, called a messenger, is sent down the cable and causes the bottle to flip over and seal itself.

2. Sample depth can be determined from cable inclination and length or with a pulsating sound source.

3. Reversing thermometers automatically record the temperature of the water from which the sample is taken. As the sample bottle and thermometer turn over, a gap forms at the base of the mercury column, which prevents the temperature reading from changing. Temperature can also be determined electronically.

The Ocean Sciences: Desalinization

B. Desalinization is the process of producing potable (drinkable) water from seawater using one of the following methods.

1. Distillation is the evaporation of seawater and the condensation of the vapor.

2. Freezing can produce salt-free ice which can be melted for water (salt exclusion).

3. Reverse osmosis is placing seawater under pressure and forcing water molecules through a semi-permeable membrane leaving a brine behind.

4. Electrodialysis is using electrically charged surfaces to attract cations and anions leaving a fresh water mass between them.

5. Salt absorption is using resins and charcoal to absorb ions from seawater.

The Ocean Sciences: Other Physical Properties of Water

C. Sea ice is ice that forms by the freezing of seawater; icebergs are detached parts of glaciers.

1. As seawater freezes, needles of ice form and grow into platelets that gradually produce a slush at the sea surface.

2. As ice forms, the salt remains in solution, increasing salinity and further lowering the freezing point of the water.

3. Depending upon how quickly the ice freezes, some salt may be trapped within the ice mass, but it gradually is released.

4. Pancake ice is rounded sheets of sea ice that become abraded along the edges as ice masses collide.

5. Pressure ridges are the buckled edges of sea ice masses that have collided.

6. Sea ice thickens with time from snow added above and water freezing below.

7. Sheets of ice are broken by waves, currents, and wind into irregular, mobile masses, called ice floes.

D. Amount of light entering the ocean depends upon the height of the sun above the horizon and the smoothness of sea surface.

1. 65% of light entering the ocean is absorbed within the first meter and converted into heat. Only 1% of light entering the ocean reaches 100m.

2. Water displays the selective absorption of light with long wavelengths absorbed first and short wavelengths absorbed last (red light travels the least distance through water, so red algae that reflects red light can grow in deeper regions as it is relying on the shorter wavelengths.)

3. In the open ocean, blue light penetrates the deepest.

4. In turbid coastal waters light rarely penetrates deeper than 20m. The water appears yellow to green because particles reflect these wavelengths.

5. The photic zone is the part of the water column penetrated by sunlight.

6. The aphotic zone is the part of the water column below light penetration and permanently dark

7. The dysphotic zone is in between the aphotic and photic zone.

E. The speed of sound in water increases as salinity, temperature and pressure increase, but in the ocean, the speed of sound is mainly a function of temperature and pressure.

1. Above the pycnocline increasing pressure with depth increases the speed of sound despite the gradual decrease in temperature.

2. Within the pycnocline, the speed of sound decreases rapidly because of the rapid decrease in temperature and only slight increase in pressure.

3. Below the pycnocline the speed of sound gradually increases because pressure continues to increase, but temperature only declines slightly.

4. SOFAR Channel is located where sound speed is at a minimum. Refraction of sound waves within the channel prevents dispersion of the sound energy and sound waves travel for 1000’s of kilometers within the channel. (Within the pycnocline around 1000m)

The Ocean Sciences: Sea Surface Microlayer

F. The sea surface microlayer is the water surface to a depth of a few hundred micrometers. It is critical for the exchange between the atmosphere and the ocean.

1. Neuston layer is the habitat of the sea surface microlayer and is inhabited by the neuston, all organisms of the microlayer.

2. Processes that transport matter to the surface layer from below are:

a. Diffusion— random movement of molecules.

b. Convection— vertical circulation resulting in the transfer of heat and matter.

c. Bubbles— the most important process because bubbles absorb material and inject it into the air as they burst.

6-1. Atmospheric Processes

A. Density of air is controlled by temperature, pressure, and moisture content.

1. Warm air is less dense than cold air and moist air is less dense than dry air.

2. Air pressure is the weight of the air from Earth’s surface to the top of the atmosphere and equals 1.04kg/cm2 (standard air pressure, one atmosphere) at sea level.

3. Low-pressure zone is where air density is lower than in surrounding areas because the air is warmer or has a higher moisture content.

4. High-pressure zone is where air pressure is higher than in surrounding area because of cooling or lower moisture content.

5. Fluids (air and water) flow from areas of high pressure to areas of low pressure.

7. Change in pressure across a horizontal distance is a pressure gradient.

a. Greater the difference in pressure and the shorter the distance between them, the steeper the pressure gradient and the stronger the wind.

8. Movement of air across a pressure gradient parallel to Earth’s surface is called a wind and winds are named for the direction from which they come. In contrast, ocean currents are named for the direction towards which they travel.

B. Rotation of the Earth strongly influences winds.

1. Global winds blow in response to variation in pressure related to uneven solar heating (insolation) of Earth’s surface.

2. Coriolis deflection is the apparent deflection of objects moving across Earth’s surface to the right of direction of travel in the Northern Hemisphere and to the left of direction of travel in the Southern Hemisphere.

C. Three major convection cells are present in each hemisphere.

1. The Hadley cell extends from the Equator to about 30o latitude.

2. The Ferrel Cell extends from 30 o to about 60o latitude.

3.The Polar Cell extends from 90 o to about 60o latitude.

4. Duldroms: area around equator with little wind

5. Horse latitudes: area around the 30degree latitude with little wind (back when they sailed, they had to eat the horses if they got caught here.)

6-2. Surface Ocean Currents

D. Wind-driven currents are produced by the interaction between the wind and the water.

1. As wind moves across the water, collision of air molecules with water molecules inefficiently transfers energy from the air to the water.

- Water moves at about 3–4% of the wind speed.

2. Zonal wind flow is wind moving nearly parallel to latitude as a result of Coriolis deflection.

3. Westerly-driven ocean currents in the trade winds. Easterly-driven ocean currents (polar regions), the Westerlies, and the deflection of the ocean currents by the continents results in a circular current, called a gyre, which occupies most of the ocean basin in each hemisphere.

E. Pressure gradients develop in the ocean because the sea surface is warped into broad mounds and depressions with a relief of about one meter.

1. Mounds are caused by convergences, places where water flows together and sinks.

2. Depressions are caused by divergences, places from where water rises to the surface and flows outward.

3. Water flowing down pressure gradients on the ocean’s irregular surface is deflected by Coriolis and the amount of deflection is a function of location and speed.

F. With time, wind-driven surface water motion extends downward into the water column, but speed decreases and direction changes because of Coriolis deflection.

1. Ekman Spiral is the spiraling pattern described by changes in water direction and speed with depth.

2. Eckman transport is the net transport of water by wind-induced motion.

a. Net transport of the water in an Eckman spiral has a Coriolis deflection of 90o to the direction of the wind. This deflection is to the right in the N. hemisphere and left in the S. Hemisphere.

3. Along coastal areas Eckman transport can induce downwelling or upwelling by driving water towards or away from the coast, respectively.

G. Langmuir circulation is a complex horizontal helical (spiral) motion that extends parallel to the wind.

1. Adjacent helices rotate in opposite directions creating alternating zones of convergence and divergence.

2. Material floating on the surface becomes concentrated in the zones of convergence and form sea stripes which parallel the wind direction.

H. Geostrophic flow allows currents to flow long distances with no apparent Coriolis deflection.

1. Coriolis deflects water into the center of the gyres, forming a low mound.

2. As height of the mound increases, the pressure gradient steepens pushing the water outward in an attempt to level the mound.

3. When the pressure gradient equals Coriolis deflection, the current flows parallel to the wind around the mound as a geostrophic current and this is called geostrophic flow.

4. Gyres in the Northern Hemisphere rotate clockwise and in the southern hemispheres counterclockwise.

5. The current flow pattern in gyres is asymmetrical with narrow, deep and swift currents along the basin’s western edge and broad, shallow slower currents along the basin’s eastern edge.

6. The geostrophic mound is deflected to the western part of the ocean basin because of the eastward rotation of the Earth on its axis.

7. The Sargasso Sea is a large area of warm water encircled by the North Atlantic gyre and separated from cold waters below by a strong thermocline.

8. Western boundary currents, such as the Gulf Stream, form a meandering boundary separating coastal waters from warmer waters in the gyre’s center. Western boundary current means that is the western part of the ocean and is off the east coast of the continent. In the Northern Hemisphere these currents are warm and move Northward and in the Southern Hemsisphere these currents are warm and move Southward.

6-3. Deep Ocean Circulation

I. Thermohaline circulation is a density driven flow of water generated by differences in salinity or temperature.

1. Water at the surface is exposed to more rapid changes in salinity through evaporation or precipitation and in temperature through cooling or heating. (More variability than deep water)

2. Once water is isolated from the atmospheric influences, salinity and temperature are largely set for an extended period of time.

3. Based upon depth, surface water masses can be broadly classified as Central waters or the Mixed Layer (from 0 to 1 km), Intermediate waters (from 1 to 2 km), and Deep and bottom waters (greater than 2 km).

4. Most deep and bottom water originated at the surface in polar regions where cooling and increased salinity raised their density until they sank.

5. Ocean basins interconnect and exchange water with each other and with the surface. Inter-ocean basin circulation and exchange between surface and deep water appears largely driven by waters of the North Atlantic.

J. The major thermohaline currents appear to flow mainly equatorward, but this is because they originate in the polar regions and their outward flow is confined between the continents.

1. Warmer water (>10oC) is confined between 45o north and south latitude.

2. Poleward of 45o, density of water increases because of declining temperature and increased salinity because of evaporation or ice formation.

3. The water sinks to a density-appropriate level and then slowly flows outward in all directions across the basin until they are blocked by a continent.

4. Deep water gradually mixes with other water masses and eventually rises to the surface.

5. The Atlantic Ocean has the most complex ocean stratification containing the following layers: Antarctic Bottom Water, Antarctic Deep Water, North Atlantic Deep Water, Arctic Intermediate Water, and Mediterranean Intermediate Water

6. The Pacific Ocean has a less complex stratification, is weakly layered, displays sluggish circulation and is remarkably uniform below 2000m.

7. The Indian Ocean has the simplest stratification consisting of Common Water, Antarctic Intermediate Water, and Red Sea Intermediate Water.

8. Climate change affects thermohaline circulation; Increased freshwater influx to the North Atlantic from melting polar ice reduces salinity and density of surface water, and could shut down NADW downwelling, changing weather patterns in Europe and North America.

6-4. Water Flow in Semi-enclosed Seaways

K. Most seas are indentations into continents, partially isolated from the ocean and strongly influenced by continental climate and river drainage.

1. As Atlantic Ocean water flows through the Straits of Gibraltar into the Mediterranean Sea at the surface, warm, highly saline Mediterranean Sea water flows out through the Straits at the bottom.

2. In the Black Sea the surface water is brackish because of excess precipitation and river inflow.

Waves in the Ocean

7-1. Properties of Ocean Waves

A. Waves are the undulatory motion of a water surface.

1. Parts of a wave are, Wave crest, Wave trough, Wave height (H), Wave Amplitude, Wavelength (L),and Wave period (T).

2. Wave period provides a basis for the wave classifications: Capillary waves, Chop, Swell, Tsunamis, Seiches.

B. Most of the waves present on the ocean’s surface are wind-generated waves.

1. Size and type of wind-generated waves are controlled by: Wind velocity, Wind duration, Fetch, and Original state of sea surface.

2. As wind velocity increases wavelength, period and height increase, but only if wind duration and fetch are sufficient.

3. Fully developed sea is when the waves generated by the wind are as large as they can be under current conditions of wind velocity and fetch.

4. Significant wave height is the average wave height of the highest 1/3 of the waves present and is a good indicator of potential for wave damage.

7-2. Wave Motions

C. Progressive waves are waves that move forward across the surface.

1. As waves pass, wave form and wave energy move rapidly forward, not the water.

2. Water molecules move in an orbital motion as the wave passes.

3. Diameter of orbit increases with increasing wave size and decreases with decreasing water depth.

4. Wave base is the depth to which a wave can move water.

5. If the water is deeper than wave base, orbits are circular and there is no interaction between the bottom and the wave, but if the water is shallower than wave base, orbits are elliptical and become increasingly flattened towards the bottom.

6. There are three types of waves defined by water depth: Deep-water wave, Intermediate-water wave, and Shallow-water wave.

7. Celerity is the velocity of the wave form, not the water.

8. The celerity of a group of waves all traveling at the same speed in the same direction is less than the speed of the waves within the group.

7-3. Life History of Ocean Waves

D. Fetch is the area of contact between the wind and the water and is where wind-generated waves begin.

1. Seas is the term applied when the fetch has a chaotic jumble of new waves.

2. Waves continue to grow until the sea is fully developed or becomes limited by fetch restriction or wind duration.

3. Wave interference is the momentary interaction between waves as they pass through each other. Wave interference can be constructive or destructive.

4. Because celerity increases as wavelength increases, longer waves travel faster than short waves.

E. The shallower the water, the greater the interaction between the wave and the bottom alters the wave properties, eventually causing the wave to collapse.

1. Celerity decreases as depth decreases.

2. Wavelength decreases as depth decreases.

3. Wave height increases as depth decreases.

4. Troughs become flattened and wave profile becomes extremely asymmetrical.

5. Period remains unchanged. Period is a fundamental property of a wave

6. Refraction is the bending of a wave into an area where it travels more slowly.

F. Wave steepness (stability) is a ratio of wave height divided by wavelength (= H/L).

1. In shallow water, wave height increases and wavelength decreases.

2. When H/L is larger than or equals 1/7 (H/L ³ 1/7), the wave becomes unstable (breaks)

3. There are three types of breakers:, Spilling breakers (beaches with a slight slope), Plunging breakers (beaches with a medium slope), and Surging breakers (beaches with a very steep slope).

G. Storm surge is the rise in sea level resulting from low atmospheric pressure associated with storms and the accumulation of water driven shoreward by the winds.

1. Water is deeper at the shore area, allowing waves to progress farther inland.

2. Storm surge is especially severe when superimposed upon a high tide.

7-4. Standing Waves

H. Standing waves or seiches consist of a water surface "seesawing" back and forth.

1. A node is an imaginary line across the surface which experiences no change in elevation as the standing wave oscillates. It is the line about which the surface oscillates.

2. Antinodes are where there is the maximum displacement of the surface as it oscillates and are usually located at the edge of the basin.

3. Geometry of the basin controls the period of the standing wave. A basin can be closed or open.

4. Standing waves can be generated by storm surges and tidal bulges as seen in the Bay of Fundy.

5. Resonance amplifies the displacement at the nodes and occurs when the period of the basin is similar to the period of the force producing the standing wave.

7-5. Other Types of Progressive Waves

I. Internal waves form within the water column on the pycnocline.

1. Because of the small density difference between the water masses above and below the pycnocline, wave properties are different compared to surface waves.

2. Internal waves display all the properties of surface progressive waves including reflection, refraction, interference, breaking, etc.

3. Any disturbance to the pycnocline can generate internal waves, including: Flow of water related to the tides., Flow of water masses past each other, Storms, or Submarine landslides/ turbidity currents.

J. Tsunamis were previously called tidal waves, but are unrelated to tides.

1. Tsunamis consist of a series of long-period waves characterized by very long wavelength (up to 100 km) and high speed (up to 760 km/hr) in the deep ocean.

2. Because of their large wavelength, tsunamis are shallow-water to intermediate-water waves as they travel across the ocean basin.

3. They only become a danger when reaching coastal areas where wave height can reach 10 m.

4. Tsunamis originate from earthquakes, volcanic explosions, or submarine landslides.

Tides

8-1. Tidal Characteristics

A. Tides have a wave form, but differ from other waves because they are caused by the interactions between the ocean, Sun and Moon.

1. Crest of the wave form is high tide and trough is low tide.

2. The vertical difference between high tide and low tide is the tidal range.

3. Tidal period is the time between consecutive high or low tides and varies between 12 hrs 25 min (semidiurnal tides) to 24 hrs 50 min (diurnal tides).

4. There are three basic types of daily tides defined by their period and regularity: Diurnal tides, Semidiurnal tides, and Mixed tides.

5. Over a month the daily tidal ranges vary systematically with the cycle of the Moon.

6. Tidal range is also altered by the shape of a basin and sea floor configuration.

7-2. Origin of the Tides

B. Tides result from gravitational attraction and centrifugal effect.

1. Gravity varies directly with mass, but inversely with distance.

2. Although much smaller, the Moon exerts twice the gravitational attraction and tide-generating force as the Sun because the Moon is closer.

3. Gravitational attraction pulls the ocean towards the Moon and Sun, creating two gravitational tidal bulges in the ocean (high tides).

4. Centrifugal effect is the push outward from the center of rotation.

5. Latitude of the tidal bulges is determined by the declination, the angle between Earth’s axis and the lunar and solar orbital plane.

6. Spring tides occur when Earth, Moon and Sun are aligned in a straight line and the tidal bulges display constructive interference, producing very high, high tides and very low, low tides.

a. Spring tides coincide with the new and full moon.

7. Neap tides occur when the Earth, Moon, and Sun are aligned forming a right angle and tidal bulges displaying destructive interference, producing low high tides and high low tides.

a. Neap tides coincide with the first quarter (waxing) and last quarter (waning) moon.

8. Earth on its axis and the Moon in its orbit both revolve eastward and this causes the tides to occur 50 minutes later each day thus the 24 hours and 50 minutes for the tidal cycle.

C. Movement of tides across ocean basins is deflected by Coriolis, blocked by continental landmasses and forms a rotary wave, which each day completes two cycles around the basin if the tide is semidiurnal or one cycle if it is diurnal.

1. High tide at the ocean basin’s western edge creates a pressure gradient sloping downward towards the east.

2. As water flows down the gradient, Coriolis deflects water towards the equator, where it accumulates and establishes a pressure gradient sloping downward towards the pole.

3. Water flowing down this gradient is deflected eastward, forming a pressure gradient sloping downward to the west.

4. Westward flow along this gradient is diverted poleward forming a pressure gradient sloping downward toward the equator.

5. Finally, the flow toward the equator is deflected westward, completing the cycle.

D. A rotary wave is part of an amphidromic system (rotary standing wave) in which the wave progresses about a node (no vertical displacement) with the antinode (maximum vertical displacement) rotating about the basin’s edges.

1. Cotidal lines connect points on the rotary wave that experience high tide at the same time.

a. Cotidal lines are not evenly spaced because tides are shallow water waves and their celerity depends upon water depth.

2. Corange circles are lines connecting points which experience the same tidal range.

a. The lines form irregular circles that are concentric about the node.

b. Tidal range increases outward from the node.

3. Amphidromic systems rotate clockwise in the Southern Hemisphere and counterclockwise in the Northern Hemisphere because of the difference in the direction of Coriolis deflection. Amphidromic points are the nodes where there is no influence of tides on the water levels.

4. Irregular coastlines distort the rotary motion.

5. Actual tide expressed at any location is a composite of 65 different tidal components.

8-3. Tides in Small and Elongated Basins

E. In long and narrow basins, tides can not rotate.

1. Currents in these basins simply reverse direction between high and low tide, flowing in with the high tide and out with the low tide.

2. Cotidal and corange lines are nearly parallel to each other.

3. Tidal ranges increase if a bay tapers landward because water is funneled towards the basin’s narrow end.

4.Tidal resonance occurs if the period of the basin is similar to the tidal period.

a. Resonance can greatly enhance the tidal range.

5. A tidal bore is a wall of water that surges upriver with the advancing high tide. (ex. Bay of Fundy)

8-4. Tidal Currents

F. The movement of water towards and away from land with the high and low tides, respectively, generates tidal currents.

1. Flood current is the flow of water towards the land with the approaching high tide.

2. Ebb current is the flow of water away from the land with the approaching low tide.

3. Far off shore the tidal currents inscribe a circular path over a complete tidal cycle.

4. Near shore the tidal currents produce simple landward and then seaward currents.

8-5. Power from Tides

G. Electricity can be generated from tidal currents if the tidal range is greater than 5 m in a large bay connected to the ocean by a narrow opening.

1. A dam is constructed across the opening and water is allowed to flow into and out of the bay when sufficient hydraulic head exist to drive turbines and generate power.

Marine Ecology

9-1. Ocean Habitats

A. There are two major marine provinces: the benthic (bottom) and the pelagic (water column).

1. The benthic environment is divided by depth into the: Intertidal zone (littoral zone), Sublittoral zone, Bathyal zone, Abyssal zone, and the Hadal zone

2. The pelagic environment is divided into the Neritic Zone and the Oceanic Zone

B. The ocean can also be divided into zones based upon depth of light penetration.

1. The photic zone is the depth where light is sufficient for photosynthesis.

2. The dysphotic zone is where illumination is too weak for photosynthesis.

3. The aphotic zone receives no light from the surface because it is all absorbed by the water above.

9-2. Classification of Organisms

D. In 1735, Linnaeus developed the taxonomic classification used in zoology.

1. The categories are from largest to smallest: Kingdom, Phylum, Class, Order, Family, Genus and Species.

2. The name of a species consists of the genus name combined with a trivial name.

a. The genus name begins with a capital.

E. The five major kingdoms in the ocean are: Monera, Protista, Chromista, Fungi, and Metazoa.

1. Monera are the bacteria and blue-green algae (cyanobacteria).

2. Protista are single-celled organisms with a nucleus. (algae and protozoans)

3. Chromista are marine plants, either floating or attached to the seafloor.

4. Fungi are abundant in the intertidal zone and are important in decomposition.

5. Animals: Metazoa include all multicellular animals in the ocean.

9-3. Classification by Lifestyle

F. Marine organisms can also be classified by lifestyle.

1. Plankton are the organisms which float in the water and have no ability to propel themselves against a current.

a. They can be divided into phytoplankton (plants) and zooplankton (animals).

2. Nekton are active swimmers and include marine fish, reptiles, mammals, birds and others.

3. Benthos are the organisms which live on the bottom (epifauna) or within the bottom sediments (infauna).

4. Some organisms cross from one lifestyle to another during their life, being pelagic early in life and benthic later.

9-4. Basic Ecology

G. Environmental factors in the marine environment include: temperature, salinity, pressure, nutrients, dissolved gases, currents, light, suspended sediments, substrate (bottom material), river inflow, tides and waves.

1. Ecosystem is the total environment including the biota (all living organisms) and non-living physical and chemical aspects.

2. Temperature can control distribution, degree of activity and reproduction of an organism.

3. Salinity can control the distribution of organisms and force them to migrate in response to changes in salinity.

4. Hydrostatic pressure is the pressures exerted by a column of water surrounding an organism.

9-5. Selective Adaptive Strategies

H. More than 90% of marine plants are algae and most are unicellular and microscopic.

1. To photosynthesize (produce organic material from inorganic matter and sunlight) plants must remain within the photic zone.

2. Diatoms are single cells enclosed in a siliceous frustrule (shell) that is shaped as a pillbox.

3. Dinoflagellates are single cells with two whip-like tails (flagella).

I. Zooplankton include the copepods and foraminifera.

1. Copepods are small herbivores (plant-eating organisms) that filter diatoms from the water.

2. Foraminifera are single-celled, microscopic organisms which build shells of calcium carbonate.

J. The morphology of fish has evolved to allow them to move through the water easily.

1.The fish’s body must overcome three types of drag (resistance): Surface drag, Form drag, and Turbulent drag.

2. Speed is dependent upon body length, beat frequency, and the aspect ratio of the caudal fin.

3. Aspect ratio is the ratio of the square of the caudal fin height to caudal fin area: AR = (Caudal Fin Height)2/Caudal Fin Area

4. There are three basic body forms, each adapted to a different life style.

5. There is a strong correlation between predation success and body form.

K. Intertidal benthic communities generally display vertical zonation that parallels sea level.

1. Zonation reflects the amount of time the area is submerged and the ability of the organism to survive the stress of exposure.

2. Benthic communities also vary in response to substrate (bottom material).

Lecture Outline for Chapter 10

10-1. Food Webs and Trophic Dynamics

A. An ecosystem is the totality of the environment encompassing all chemical, physical, geological and biological parts.

1. Ecosystems function by the exchange of matter and energy.

2. Plants use chlorophyll in photosynthesis to convert inorganic material into organic compounds and to store energy for growth and reproduction.

a. Plants are autotrophs and the primary producers in most ecosystems.

3. All other organisms are heterotrophs, the consumers and decomposers in ecosystems.

4. Herbivores eat plants and release the stored energy.

5. Material is constantly recycled in the ecosystem, but energy gradually dissipates as heat and is lost.

B. The word "trophic" refers to nutrition.

1. Trophic dynamics is the study of the nutritional interconnections among organisms within an ecosystem.

2. Trophic level is the position of an organism within the trophic dynamics.

a. Autotrophs form the first trophic level.

b. Herbivores are the second trophic level.

c. Carnivores occupy the third and higher trophic levels.

d. Decomposers form the terminal level.

3. A food chain is the succession of organisms within an ecosystem based upon trophic dynamics. (Who is eaten by whom.)

4. An energy pyramid is the graphic representation of a food chain in terms of the energy contained at each trophic level.

a. The size of each successive level is controlled by the size of the level immediately below.

C. As the primary producers, plants require sunlight, nutrients, water, and carbon dioxide for photosynthesis.

1. Sunlight and nutrients are commonly the limiting factor.

2. The formula for photosynthesis is:

Sunlight + 6 CO2 + 6 H2O --> C6H12O6 (sugar) + 6 O2.

3. Phytoplankton blooms are the rapid expansion of a phytoplankton population because light and nutrients are abundant.

D. Animals must consume pre-existing organic material to survive.

1. Animals break down the organic compounds into their inorganic components to obtain the stored energy.

2. The chemical formula for respiration is:

C6H12O6 (sugar) + 6 O2 --> 6 CO2 + 6 H2O + Energy.

3. The recovered energy is used for movement, reproduction, and growth.

4. The food consumed by most organisms is proportional to their body size.

a. Generally, smaller animals eat smaller food and larger animals eat larger food, although exceptions occur.

5. The basic feeding style of animals are: Grazers, Predators, Scavengers, Filter feeders, and Deposit feeders.

6. Population size is dependent upon food supply.

E. Bacteria are the decomposers; they break down organic material and release nutrients for recycling.

1. Few bacteria are capable of completely degrading organic material into its inorganic components. Most operate in succession with other bacteria to decompose material in a series of stages.

2. Bacteria also serve as food for other organisms either directly or indirectly.

3. Two basic types of bacteria are Aerobic bacteria and Anaerobic bacteria.

4. Most bacteria are heterotrophs, but two types are autotrophs: Cyanobacteria (blue-green algae) and Chemosynthetic bacteria.

F. Food chains transfer energy from one trophic level to another.

1. Biomass is the quantity of living matter per volume of water.

2. With each higher trophic level, the size of organisms generally increases, but their reproductive rate, number, and the total biomass decrease.

3. The two major food chains in the ocean are the Grazing food chain and the Detritus food chain - non-living wastes form the base of the food chain.

4. Only about 10-20% of energy is transferred between trophic levels and this produces a rapid decline in biomass at each successive trophic level.

10-2. General Marine Productivity

G. Primary production is the total amount of carbon (C) in grams converted into organic material per square meter of sea surface per year (gm C/m2/yr).

1. Factors that limit plant growth and reduce primary production include solar radiation and nutrients as major factors and upwelling, turbulence, grazing intensity and turbidity as secondary factors.

2. Only .1 to .2% of the solar radiation is employed for photosynthesis and its energy stored in organic compounds.

3. Macronutrients and Micronutrients are chemicals needed for survival, growth, and reproduction.

4. Upwelling and turbulence can return nutrients to the surface.

5. Over-grazing of autotrophs can deplete the population and lead to a decline in productivity.

6. Turbidity reduces the depth of light penetration and restricts productivity even if nutrients are abundant.

H. Productivity varies greatly in different parts of the ocean in response to the availability of nutrients and sunlight.

1. In the tropics and subtropics sunlight is abundant, but it generates a strong thermocline that restricts upwelling of nutrients and results in lower productivity.

a. High productivity locally can occur in areas of coastal upwelling, in the tropical waters between the gyres and at coral reefs.

2. In temperate regions productivity is distinctly seasonal.

3. Polar waters are nutrient-rich all year but productivity is only high in the summer when light is abundant.

10-3. Global Patterns of Productivity

I. Primary productivity varies from 25 to 1250 gm C/m2/yr in the marine environment and is highest in estuaries and lowest in the open ocean.

1. In the open ocean productivity distribution resembles a "bull’s eye " pattern with lowest productivity in the center and highest at the edge of the basin.

a. Water in the center of the ocean is a clear blue because it is an area of downwelling, above a strong thermocline and is almost devoid of biological activity.

2. Continental shelves display moderate productivity between 50 and 200 gm C/m2/yr because nutrients wash in from the land and tide- and wave- generated turbulence recycle nutrients from the bottom water.

3. Polar areas have high productivity because there is no pycnocline to inhibit mixing.

4. Equatorial waters have high productivity because of upwelling.

J. It is possible to estimate plant and fish productivity in the ocean.

1. The size of the plankton biomass is a good indicator of the biomass of the remainder of the food web.

2. Annual primary production (APP) is equal to primary production rate (PPR) times the area for which the rate is applicable.

APP = PPR x Area (to which applicable )

3. Transfer efficiency (TE) is a measure of the amount of carbon that is passed between trophic levels and is used for growth.

a. Transfer efficiency varies from 10 to 20% in most food chains.

4. Potential production (PP) at any trophic level is equal to the annual primary production (APP) times the transfer efficiency (TE) for each step in the food chain to the trophic level of the organism under consideration.

PP = APP x TE (for each step)

5. Although rate of productivity is very low for the open ocean compared to areas of upwelling, the open ocean has the greatest biomass productivity because of its enormous size.

6. In the open ocean the food chains are longer and energy transfer is low, so fish populations are small.

a. Most fish production is equally divided between area of upwelling and coastal waters.

7. Calculations suggest that the annual fish production is about 240 million tons/yr.

8. Over-fishing is removing fish from the ocean faster than they are replaced by reproduction and this can eventually lead to the collapse of the fish population.

10-4. Biological Productivity of Upwelling Water

K. Upwelling of deep, nutrient-rich water supports large populations of phytoplankton and fish.

1. The waters off the coast of Peru normally are an area of upwelling, and support one of the world’s largest fisheries.

2. Every three to seven years, warm surface waters in the Pacific displace the cold, nutrient-rich water on Peru’s shelf in a phenomenon called El Niño.

3. El Niño results in a major change in fauna on the shelf and a great reduction in fishes.

a. This can lead to mass starvation of organisms dependent upon the fish as their major food source.

The Dynamic Shoreline

11-1. Coastal Water Movement

A. Breaking waves provide the energy that changes the shape and texture of the beach deposits.

1. As waves shoal (touch bottom) in shallow water celerity decreases, wavelength decreases, wave height increases, waves become less stable and refraction occurs.

a. Refraction is the bending of waves towards shallower water so that they break almost parallel to the shore.

2. Waves become unstable and break in very shallow water.

3. The beach is the part of the land that touches the sea. It can be divided into the: offshore, nearshore (breaker zone, surf zone, swash zone), and the backshore

4. Position of the divisions of the beach varies with the tides, advancing landward with high tide and retreating seaward with low tide.

B. Waves generate longshore currents that flow parallel to the beach and rip currents that flow perpendicularly to the beach.

1. Angle of wave approach is the acute angle (less than 90o) between the wave crest and the beach.

2. The direction of longshore current varies with the direction of wave approach.

3. Longshore currents can also be generated by wave set-up.

4. Where two opposing longshore currents collide, they form a swift, narrow, seaward rip current.

11-2. Beaches

C. Beach sediments are moved by currents and waves, especially breakers.

1. A beach profile is a cross section of the beach along a line that is perpendicular to the shoreline.

2. A swell profile is concave upward with a wide, broad berm (relatively flat backshore) and steep intertidal beach face.

3. A storm profile displays erosion of the berm and a broad flat intertidal beach face.

4. A sand budget is the balance between sediment added to and sediment eroded from the beach.

5. A coastal cell occurs when sand is transported from its source, down the beach, and is lost in a submarine canyon.

11-3. Coastal Dunes

D. Sand dunes are formed by winds blowing sand landward from the dry part of the beach.

1. Well-developed dunes typically have a sinusoidal profile with the primary dune at the landward edge of the beach and possible secondary dunes located farther inland.

2. Vegetation on the dunes traps windblown sand on their downwind side and promotes dune growth and stability.

3. Blowouts are wind-scoured breaks in the dune or depressions in the dune ridge and commonly occur if vegetation is destroyed.

4. Dunes are best developed if sand is abundant, onshore winds are moderately strong and persistent, the tidal range is large and the beach is wide and gently sloping.

5. Sand saltates (bounces) up the windward side of the dune, collects in the wind-shadow at the top and periodically slides down the leeward face of the dune when the accumulation of sand becomes over-steepened—resulting in dune migration.

6. Wave erosion of sand dunes transports sand offshore and creates a steep scarp at the base of the dune.

7. Dunes act as a natural barrier and prevent inland flooding.

8. Human activity that damages vegetation leads to dune destruction by blowouts and washover by storm waves.

11-4. Barrier Islands

E. Barrier islands are islands composed of sediment that parallel the coast and form where sand supply is abundant and a broad sea floor slopes gently seaward.

1. The islands are separated from the mainland by shallow bodies of water which are connected to the ocean through tidal inlets.

2. A series of distinct environments develop across the island parallel the beach and include the nearshore zone, dune field, back-island flats and salt marshes.

3. Barrier islands are created in many ways including: sand ridges isolated by rising sea level, Sand spits breached during a storm, vertical growth and emergence of longshore sand bars.

4. As sea level rises, barrier islands migrate landward as washover transports sediments from the seaward side of the island to the landward side.

F. Storm surge is the high water created by the accumulation of wind-blown water against the shore and the mound of water generated by the low atmospheric pressure of the storm.

1. The elevated water level allows waves to reach much farther inland than usual, especially if the storm surge coincides with a high tide.

2. Waves more easily breach the island and wash over lower areas.

3. New tidal channels may form during a storm surge.

11-5. Cliffed Coasts

G. A sea cliff is an abrupt rise of the land from sea level.

1. A sea cliff is most vulnerable to erosion at its base because waves that slam against the cliff compress air inside cracks which expands violently, sediment is hurled against the cliff by the waves, and sea water dissolve some rock types.

2. When sufficient rock at the base of the cliff has been removed, the upper part of the cliff collapses.

3. Collapsed material protects the base of the sea cliff from additional erosion until it is destroyed and removed.

4. Rate at which the cliff recedes is dependent upon:

a. Composition and durability of cliff material.

b. Joints, fractures, faults and other weaknesses in the cliff material.

c. Amount of precipitation.

d. Steepness of the cliff.

11-6. Deltas

H. A delta is an emergent accumulation of sediment deposited at the mouth of a river as it flows into a standing body of water.

1. Deltas were named after the Greek letter delta D .

2. The three major areas of a delta are delta plain ,delta front and prodelta.

3. Shape of the delta can be altered by tides, waves, and river deposition.

4. Reduction in the supply of sediment to a delta results in delta erosion and subsidence as the sediments of the delta compact.

11-7. Impact of People on the Coastline

I. Coastlines are desirable areas for human habitation, but human activity conflicts with the dynamic state of coastal systems.

1. Humans try to stabilize the coastline in two ways: by interfering with longshore sand transport, and by redirecting wave energy to prevent erosion.

2. Preventing of sand drift involves jetties and groins.

3. Redirecting wave energy involves breakwaters and seawalls.

4. Beach nourishment with sand is expensive and temporary.

5. An increase in sea level from global warming will cause more land to be flooded and threaten more coastal buildings.

Coastal Habitats

A. The term coast has a much broader meaning than shoreline and includes many other habitats and ecosystems associated with terrestrial and marine processes.

1. The six major coastal settings are: estuary, lagoon, salt marsh, mangrove swamp, and coral reef.

2. Shorelines are one of the most productive ecosystems and because they are shallow, they strongly respond to the effects of waves, tides, and weather.

12-1. Estuaries

B. Estuaries are semi-enclosed bodies of water where fresh water from the land mixes with seawater.

1. Estuaries originate as: drowned river valleys, fjords, bar-built estuaries, and tectonic estuaries.

2. Salinity typically grades from normal marine salinity at the tidal inlet to fresh water at the mouth of the river.

C. Estuaries can be subdivided into three types based upon the relative importance of river inflow and tidal mixing.

1. Salt-wedge estuaries are dominated by the outflow from rivers.

2. Partially-mixed estuaries are dominated by neither river inflow nor tidal mixing.

3. In well-mixed estuaries tidal turbulence destroys the halocline and water stratification.

4. Because river discharge and tidal flow vary, conditions within an estuary can also change, being well-mixed when river flow decreases relative to tidal mixing, to becoming a salt-wedge estuary at times of maximum river discharge.

D. The widely fluctuating environmental conditions in estuaries make life stressful for organisms.

1. Estuaries are extremely fertile because nutrients are brought in by rivers and recycled from the bottom because of the turbulence.

2. Stressful conditions and abundant nutrients result in low species diversity, but great abundance of the species present.

3. Despite abundance of nutrients, phytoplankton blooms are irregular and the base of the food chain is detritus washed in from adjacent salt marshes.

4. The benthonic fauna strongly reflects the nature of the substrate and most fishes are juvenile forms living within the estuary until they mature and migrate to the ocean.

12-2. Lagoons

E. Lagoons are isolated to semi-enclosed, shallow, coastal bodies of water that receive little if any fresh water inflow.

1. Lagoons can occur at any latitude and their salinities vary from brackish to hypersaline depending upon climate and local hydrology.

2. Bottom sediments are usually sand or mud eroded which was from the shoreline or swept in through the tidal inlet.

3. In the tropics, the water column is typically isothermal.

4. In the subtropics, salinity generally increases away from the inlet and the lagoon may display inverse flow.

12-3. Salt Marshes

F. Salt marshes are intertidal flats covered by grassy vegetation.

1. Marshes are most commonly found in protected areas with a moderate tidal range, such as the landward side of barrier islands.

2. Marshes flood daily at high tide and then drain through a series of channels with the ebb tide.

3. They are one of the most productive environments.

4. Marshes can be divided into two parts: Low salt marshes and High salt marshes.

5. Distribution and density of organisms in salt marshes strongly reflects availability of food, need for protection, and frequency of flooding.

12-4. Mangrove Swamps

G. Mangroves are large woody trees with a dense, complex root system that grows downward from the branches.

1. Mangroves are the dominant plant of the tropical and subtropical intertidal area.

2. Distribution of the trees is largely controlled by air temperature, exposure to wave and current attack, tidal range, substrate, and seawater chemistry.

3. Detritus from the mangrove forms the base of the food chain.

12-5. Coral Reefs

H. A coral reef is an organically constructed, wave-resistant, rock-like structure created by carbonate-secreting organisms.

1. Most of the reef is composed of loose to well-cemented organic debris of carbonate shells and skeletons.

2. The living part of the reef is just a thin veneer on the surface.

3. Corals belong to the Cnidara.

a. The animal is the coral polyp.

b. The corallite is the exoskeleton formed by the polyp.

4. Corals share a mutualistic relationship (mutually beneficial) with the algae zooxanthallae, which lives within the skin of the polyp and can comprise up to 75% of the polyp’s body weight.

5. Corals can be either solitary or colonial.

6. Corals can not survive in fresh, brackish water or highly turbid water.

7. Corals do best in nutrient poor water because they are easily out-competed by benthonic filter feeders in nutrient-rich water where phytoplankton are abundant.

I. Coral reefs consist of several distinct parts developed in response to their exposure to waves.

1. The algal ridge occurs on the windward side of the reef and endures the pounding waves.

2. The buttress zone is the reef slope extending down from the algal ridge.

3. The reef face extends downward from the buttress zone and usually is devoid of living colonial corals because insufficient light reaches this depth.

4. The reef terrace is landward of the algal ridge and lies at mean water level.

5. The shape of the colonial coral masses reflects the environment in which they live.

J. As a result of corals growing continuously upward towards the sunlight as sea level rises and/or land subsides and, coral reefs pass through three stages of development.

1. Fringe reefs form limestone shorelines around islands or along continents and are the earliest stage of reef development.

2. As the land is progressively submerged and the coral grows upward, an expanding shallow lagoon begins to separate the fringe reef from the shoreline and the reef is called a barrier reef.

3. In the final stage the land vanishes below the sea and the reef forms a ring of islands, called an atoll, around a shallow lagoon.

14-1. Law of the Sea

A. Several treaties regarding ownership and exploitation of the marine resources have been ratified in the last fifty years.

1. President Truman extended U.S. control of the marine resources from the shoreline to a depth of 100 fathoms (183 m).

2. The 1958 and 1960 Geneva Conventions on the Law of the Sea resulted in a treaty that placed the control of the sea bed, sea bed resources and water of the continental shelf under the country that owns the nearest land.

3. The 1982 United Nations’ Draft Convention on the Law of the Sea established Territorial waters and An Exclusive Economic Zone (EEZ) that extends for 200 nautical miles offshore or to the edge of the continental shelf, if that is farther.

4. Exclusive economic zones contain about 40% of the ocean and the high seas represent the remaining 60%.

14-2. Mineral Resources

B. Petroleum, oil, and gas are hydrocarbons derived from sedimentary rocks which were deposited in quiet, productive regions with anoxic bottom waters in which the remains of phytoplankton accumulated.

1. Deep burial resulting in high temperature and pressure converted the organic remains into hydrocarbons.

a. Initially oil, but at higher temperatures and pressures, methane (CH4) natural gas were generated.

2. Pressure forced the oil and gas from the source rock into water-filled porous and permeable strata above.

3. Because oil and gas are less dense than water, they migrated upwards until their path was blocked by an impermeable layer.

4. Oil and gas accumulated, forming a large deposit within the pores of the rock, usually sandstone.

5. Location of possible accumulations of oil and gas can be determined using seismic reflection and refraction methods to determine the configuration of rock layers.

a. These methods only indicate if the configuration of rock layers have the potential to trap oil and gas. They do not indicate if oil and gas are present.

C. Gas Hydrates refer to the unusual hydrocarbon deposits that consist of frozen water molecules entrapping a single molecule of methane (natural gas).

1. Gas hydrates occur in polar sediments and in deposits of the continental slope between the depths of 300 and 500 m where cold water is in contact with the sea floor.

2. These deposits contain incredibly large amounts of gas, but currently there is no economical method for its recovery.

D. Sand and gravel are natural aggregates of unconsolidated sediment with grain size greater than 0.0625 mm in diameter.

1. Sand and gravel accumulate in high energy environments where strong currents and/or waves currently prevail and occur as relict sediments across the continental shelf from when sea level was lower.

2. These materials are used for construction of roads and buildings and to replenish beaches which are undergoing erosion.

3. Mining sand and gravel deposits from the shelf threatens both the benthic and pelagic communities and introduces large amounts of material into suspension.

E. Manganese nodules are composed of about 20-30% manganese, 10-20% iron oxide, 1.5% nickel and less than 1% cobalt, copper, zinc and lead.

1. Locally, the nodules can be very abundant, as on the subtropical sea floor of the Pacific Ocean, where billions of kilograms occur.

2. Currently, there is no economical method of recovering the nodules from the deep sea.

F. The sides of many seamounts and islands are enriched in cobalt between the depths of 1 and 2.5 km.

1. Cobalt is a strategic metal used in making jet engines and the U.S. can not produce sufficient cobalt to meet its needs.

G. Phosphorus is required for growth by all organisms.

1. Phosphate deposits generally form on submarine terraces where coastal upwelling generates high productivity.

2. Organic wastes and remains accumulate in the sediment and as they decay, they release phosphorus compounds which precipitate as phosphate nodules.

3. Nodules grow at the rate of about 1–10mm/1000 years.

4. World consumption of phosphate is about 150 million tons per year and known supplies should last until 2050.

14-3. Living Resources

H. Marine finfish can be divided into the pelagic fish which live in the water column and groundfish which live on the sea floor.

1. Most of the ocean is sparsely populated because of low nutrient availability.

2. Area of major fish production are the coastal waters and regions of upwelling.

3. Because they are economic to capture, major commercial fishes are those which form large schools.

4. The fishing industry uses sonar, scouting vessels, airplanes and satellites to locate schools and then deploy the fishing fleets to those areas.

5. Drift nets are controversial because they capture everything too large to pass through the mesh of the net and needlessly kill many organisms.

a. The 1989 United Nations’ Convention for the Prohibition of Long Drift Nets prohibited drift nets longer than 2.5 km, but compliance is largely voluntary and impossible to enforce on the open sea.

6. World ocean fish production appears to have leveled at between 80 and 90 million tons annually.

7. Currently, the expense incurred in fishing exceeds the profit from the sale of the fish and fishing industries only survive through government subsidy.

I. Mariculture is marine agriculture or fish farming of finfish, shellfish, and algae.

1. Mariculture requires raising the organisms under favorable conditions until they are large enough to be harvested for food.

2. Currently, about one out of every four fish consumed spent part of its life in mariculture and for some organisms the percentage supplied by mariculture is even larger.

3. For mariculture to be economically viable the species must be:

a. Marketable.

b. Inexpensive to grow.

c. Trophically efficient.

d. At marketable size within 1 to 2 years.

e. Disease resistant.

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