The Structure of Aquatic The Structure of Aquatic EcosystemsEcosystems

Created by Dave WernerCreated by Dave Werner

MATESMATES

5 Major Elements of Lake Structure5 Major Elements of Lake Structure

1. Morphometry1. Morphometry 2. Physical2. Physical 3. Chemical3. Chemical 4. Biological4. Biological 5. Watershed & Airshed5. Watershed & Airshed

LakesLakes

1. Morphometry1. Morphometry = function of underwater contour = function of underwater contour lines, the shape of the lake, & its geologic origin.lines, the shape of the lake, & its geologic origin.

Lake’s Morphometry is basic to its structureLake’s Morphometry is basic to its structure For example, when we know the shape and For example, when we know the shape and

structure of a lake basin, we can sometimes structure of a lake basin, we can sometimes predict how weather conditions or human-induced predict how weather conditions or human-induced events may affect water levels in that system.events may affect water levels in that system.

Still lakes = Still lakes = lentic lentic environmentsenvironments Flowing = Flowing = loticlotic systems, streams systems, streams

2. Light & Temperature2. Light & Temperature 2 major zones:2 major zones:

– LittoralLittoral– Pelagic or limneticPelagic or limnetic

Light & TemperatureLight & Temperature

Light ZonationLight Zonation– Photic/Euphotic ZonePhotic/Euphotic Zone– Aphotic Zone/ProfundalAphotic Zone/Profundal

Sublittoral Zone = The Sublittoral Zone = The deepest area of plant deepest area of plant growth.growth.

Temperature ZonationTemperature Zonation

As light energy is absorbed by water, it is converted to As light energy is absorbed by water, it is converted to heat energy, which results in the warming of the lake-heat energy, which results in the warming of the lake-surface water. surface water.

During summer, thermally During summer, thermally stratifiedstratified lakes are warmer at lakes are warmer at the top and cooler at the bottom. the top and cooler at the bottom.

The warm surface layer is called the The warm surface layer is called the epilimnionepilimnion, and , and the cooler bottom layer the the cooler bottom layer the hypolimnionhypolimnion..

The zone of rapid temperature decline in the water The zone of rapid temperature decline in the water column from shallow to deep water is called the column from shallow to deep water is called the thermoclinethermocline or the or the metalimnionmetalimnion..

Lines of equivalent temperature (or concentration) = Lines of equivalent temperature (or concentration) = Isopleths Isopleths (Fig. 2.7a (Fig. 2.7a

Fig. 2.8-2.11 (pp.41-43)Fig. 2.8-2.11 (pp.41-43)

Factors Affecting Thermal Factors Affecting Thermal StratificationStratification

Time of YearTime of Year Lake DepthLake Depth Wind FetchWind Fetch TopographyTopography SolutesSolutes

Annual Mixing PatternsAnnual Mixing Patterns

AmicticAmictic - never mixing, usually ice covered year around, in the polar - never mixing, usually ice covered year around, in the polar regions. regions.

MeromicticMeromictic - lakes that may mix once or more annually, but do not mix - lakes that may mix once or more annually, but do not mix completely. completely.

PolymicticPolymictic - these lakes have many periods of mixing annually, even ap- - these lakes have many periods of mixing annually, even ap- proaching continuous mixing and are influenced more by daily proaching continuous mixing and are influenced more by daily temperature changes than seasonal. temperature changes than seasonal.

MonomicticMonomictic - one period of mixing annually, the cold monomictic lakes - one period of mixing annually, the cold monomictic lakes are ice covered most of the year and mix during a brief summer, while the are ice covered most of the year and mix during a brief summer, while the warm monomictic lakes are the opposite with a brief ice-free winter warm monomictic lakes are the opposite with a brief ice-free winter period of mixing. period of mixing.

DimicticDimictic - lakes that usually mix twice annually in the spring and in the - lakes that usually mix twice annually in the spring and in the fall. This category covers the lakes in the temperate zones of our globe fall. This category covers the lakes in the temperate zones of our globe and includes the majority of our lakes. and includes the majority of our lakes.

3. Chemical Factors3. Chemical Factors The depth at which rapid change in a The depth at which rapid change in a

substance occurs.substance occurs. The Berkeley Pit is a chemically layered The Berkeley Pit is a chemically layered

system, which means that the chemistry system, which means that the chemistry of the water changes with depth. The of the water changes with depth. The brownish-red water at the surface is brownish-red water at the surface is actually the least contaminated water in actually the least contaminated water in the pit, and the deeper it gets, the worse the pit, and the deeper it gets, the worse the water quality. The color changes as the water quality. The color changes as well, going from brownish-red on top to well, going from brownish-red on top to bluish green at the bottom.bluish green at the bottom.

At a certain depth, the chemistry of the At a certain depth, the chemistry of the water changes so rapidly that it forms a water changes so rapidly that it forms a chemical boundary scientists refer to as chemical boundary scientists refer to as the the chemoclinechemocline (see illustration and (see illustration and graphs). Water above the chemocline is graphs). Water above the chemocline is chemically lighter (i.e., less dense) than chemically lighter (i.e., less dense) than the water below. The layering of the two the water below. The layering of the two waters is like oil floating on water. The waters is like oil floating on water. The water above the line is also less acidic water above the line is also less acidic (higher pH), with lower concentrations of (higher pH), with lower concentrations of metals. The two layers of water (above metals. The two layers of water (above and below the chemocline) act like fresh and below the chemocline) act like fresh water floating on salt water, never mixing water floating on salt water, never mixing unless stirred.unless stirred.

4. Biological Zonation4. Biological Zonation

PlanktonPlankton NektonNekton NeustonNeuston - surface - surface

– PleustonPleuston – Large floating assemblages – Large floating assemblages Attached AlgaeAttached Algae – Littoral Zone – Littoral Zone Aquatic MacrophytesAquatic Macrophytes – Higher plants, likely to dominate – Higher plants, likely to dominate

sandy or muddy littoral zonessandy or muddy littoral zones AufwuchsAufwuchs - the small animals and plants that encrust hard - the small animals and plants that encrust hard

substrates, such as rocks, in aquatic environments. Ex: substrates, such as rocks, in aquatic environments. Ex: Algae, fungi, bacteria, protozoa.Algae, fungi, bacteria, protozoa.

Benthic/BenthosBenthic/Benthos– EpifaunalEpifaunal– InfaunalInfaunal

5. Watershed & Airshed5. Watershed & Airshed

The size, slope, geologic composition, & The size, slope, geologic composition, & climate of the lake’s drainage basin climate of the lake’s drainage basin influence the identity & quantity of minerals influence the identity & quantity of minerals suspended or dissolved in the lake or suspended or dissolved in the lake or deposited in the sediment.deposited in the sediment.

Ponds vs. LakesPonds vs. Lakes

Pond – generally smaller Pond – generally smaller than a lake.than a lake.

Lake – A large inland body Lake – A large inland body of water, fresh or salt.of water, fresh or salt.– The Manahawkin Lake can The Manahawkin Lake can

be found on the West Creek be found on the West Creek USGS quad topo map. USGS quad topo map. Manahawkin Lake is a Manahawkin Lake is a reservoir in Ocean County in reservoir in Ocean County in the state of New Jersey. The the state of New Jersey. The latitude and longitude latitude and longitude coordinates for this reservoir coordinates for this reservoir are 39.6965, -74.2601 and are 39.6965, -74.2601 and the altitude is 23 feet (7 the altitude is 23 feet (7 meters).meters).

Streams & RiversStreams & Rivers

River – larger & fast moving, often warmer.River – larger & fast moving, often warmer. Stream – smaller, usually lead to larger Stream – smaller, usually lead to larger

rivers.rivers. These are These are LoticLotic systems – defined by water systems – defined by water

flow. flow. – DischargeDischarge (volume per time) (volume per time)– CurrentCurrent (distance per time) (distance per time)

MeanderingMeandering

ExampleExample

http://www.classzone.com/books/earth_science/terc/content/visualizations/es1306/es1306page01.cfm?chapter_no=visualization

Biological Structure of StreamsBiological Structure of Streams

DriftDrift – Living benthic – Living benthic invertebrates& algae that invertebrates& algae that have released or lost have released or lost their attachment to their attachment to substrate. Optimum substrate. Optimum food supply for fish & food supply for fish & inverts.inverts.

DetritusDetritus – dead organic – dead organic fragments coated w/ fragments coated w/ bacteria, fungi, & small bacteria, fungi, & small protozoans. protozoans.

EstuariesEstuaries

Where the river meets the sea.Where the river meets the sea. Structure is modified by:Structure is modified by:

– MorphometryMorphometry– TideTide– Inflowing FWInflowing FW

Salt WedgeSalt Wedge

Salt WedgeSalt Wedge

Salt Wedge Animation

WetlandsWetlands

Marshes, swamps, or Marshes, swamps, or bogsbogs

Vegetation = most Vegetation = most important structural important structural elements (emergent elements (emergent macrophytes, trees, & macrophytes, trees, & Sphagnum Sphagnum moss).moss).