Chapter 7

Chapter 7Long long long long Pelagic Ecosystems

ReviewPelagic?Largely open, unbounded environmentLarge range of freedom to move in three dimensionsLargest habitat on earthExtremely variable in temperature, salinity, turbidity, biomass, etc.Human effectsGlobal climate change90% of stocks of large pelagic fish (tuna) removed by fishingZooplankton communities shift in spatial distributionMicroscopic plastic fragments widespread and cause a variety of problems Regime shiftsecological step-changesMore Zone ReviewPelagic zonesea surface to just above the seabed99.5% of the earths habitable space Made up of the neritic and oceanic zonesNeriticMakes up 8% of the earths total sea areaLimited by the 200m depth contour (isobath)Oceanic92% total sea area65% earths surfaceCharacterized by Case 1 and Case 2 watersBenthic zone

Case 1 and 2 watersCase 1ocean color is determined by algal pigmentsExample of ocean coloring?Case 2ocean color is due to reflections from particulate matterDifference in particulate loading can lead to differences in underwater light climateHave led to varying photosynthetic processes in neritic and oceanic phytoplanktonEuropean flying squid and diatomshttp://www.youtube.com/watch?v=dwYr1TJbue0

More zones yayNeustic zoneupper surface of the oceanHarsh envionment due to high levels of ultraviolet radiationOrganisms are typically blue because protective pigments in the color reflect the damageOzone hole in earths atmosphere may cause UV damage to multiple creatures, including Antarctic krillPhotic zoneupper layer of the water column into which light penetratestop 200 metersEpipelagic zoneAlso upper 200 meters of the water columnRed light doesnt penetrate far in this zoneMany organisms have some sort of red coloring to protect against predatorsChanges with depthOrganisms are faced with increasing pressureHow much at 2 meters?Oxygen minimal layersdue to bacteria breaking down marine snowTotal mass of biota per unite volume of seawater decreasesBecause biological processes are fueled by photosyntetically generated organic matter from the surfacehttp://www.youtube.com/watch?v=vsLBOkYLLeIFood availability decreasesmore distanceEnergy efficiency become more importantBiological pump - http://www.youtube.com/watch?v=nM4SjToMgkMPelagic inhabitantsPlankton cant move horizontally, but they can move verticallyDVMdiel vertical migrationDriven primarily by escape from predators and search for foodAlso known as?Holoplanktonspend their entire life as planktonMeroplanktononly spend part of their life as planktonPlanktotrophic larvaehave an extended planktic phasehave a higher mortality rate than lecithotrophic larvaeWill have a larger genetic dispersal thoughPelagic inhabitants cont.Smaller organisms tend to be plankton, not nektonExceptionlions mane jellyfishOccurs usually because of the interaction between size and viscosityMore energy is required for them to keep movingMicrobial loopfuels the pelagic food chain, especially in oligotrophic watershttp://www.youtube.com/watch?v=qybUFnY7Y8w - cascades

Temporal and spatial variabilityVariability due to interactions between physical and biological processesGraphed using the Stommel diagramShows variations between the interplay of these two factorsSpace vs. time

Physical processesWhat causes changes inLight?Mixing?Temperature?Density?Nutrient and gas concentration?Langmuir circulationsmall scale upwellinghttp://faculty.gvsu.edu/videticp/langmuir.htmCause near-surface vortexesAlternating lines of upward divergance and downward convergence developCan lead to the accumulation of zooplankton and flotsamEkman stuffCoriolis effectforce of the earth spinningcauses water blown by the wind to move 90 to the windRight of the wind in northern hemisphere, left in southern hemisphereEkman transportmovement of the water pushed by the wind left or right depending on the hemisphereFronthorizontal boundary between water masses with different physical proptertiesmeanders in fronts core ringsimportant for transoceanic mixingUmmocean stuff(How productivity is affected)Mixed-layer depththe depth to which water-column mixing occursProblematic for phytoplankton because they may be carried below the compensation depth, where they cant get lightMay eventually inhibit phytoplankton growth though if vertical stratification prevents mixing for too longUpwelling regionsNutrients not normally limited annual primary production is highException: El Ninohttp://www.esrl.noaa.gov/psd/map/clim/sst_olr/sst_anim.shtml

Other regions and Sucky stuffHNLChigh nutrient, low chlorophyllSouthern Ocean and equatorial PacificDue to grazing pressure and absence of trance elements, especially iron (Iron Hypothesis)Since 1999, global ocean primary productivity has fallen 0.19 Pg C per yearPg C=petagram=1015 grams=1 billion metric tonsMostly occurring in low-latitude oceans (45N to 45S)Due to strengthening stratification limiting nutrientsIncreasing gin mixing and nutrient replenishment in the polar regions are unlikely to counteract middle-latitude productionSmetaceks theorythat whales are keystone species in southern oceansKrill capture ironWhales eat krill, keeping iron from sinking below useWhales return iron to the environment, and phytoplankton use it for the krill to eat

BiomesBiomethe largest coherent community unit that is convenient to recognize (lazy scientists)Categorized into four different groups characterized by the mechanisms driving their mixed layer depthWesterlies biomelocal winds and irradiance force the mixed layer depthTrades biomemixed layer depth is influenced by large-scale ocean circulation processesPolar biomebuoyant fresh water from ice melt in spring constrains the layerCoastal biomediverse procecsses like upwelling (Provincesallow regional differences in physical oceanography that help make predictions and gain understanding)Primary production to nektonGLOBECglobal research effort to understand interactions between primary consumers, higher trophic levels, and fisheriesDirect linear relationship between the magnitude of annual primary production and nekton productionMany zooplankton populations are bottom-up controlledZooplankton blooms cant occur unless phytoplankton biomass and production is sufficientTemperate waterszooplankton spike in spring and autumnHigh latitudeslimited to spring/summer peak and stay dormant in diapauseSpatial segregation allows higher overall biomass to be maintained, versus homogenous phytoplankton and grazers everywhere

Sampling the open oceanExtreme horizontal, vertical, temporal patchiness, and huge siz-erange of organisms makes it difficult to get quantitative samplesEarly studies used mostly fishing nets Presently, nets have depth, temperature, salinity and other sensors that can convey where the area of interest is back to the shipOPCsused instead of nets to obtain espimates of zooplankton numerical densityCan also use echo-sounders to detect and quantify abundance zooplankton and fishLarger organisms that come to the sea surface can be counted by observersOther methodsSampling platforms with moored instrumentsAUVsGlidersVertically-profiling floatsEarth-orbiting satellitesGive almost weekly information on sea surface temperature, chlorophyll concentration, and front positionCan also track the movements of larger animalsCan be used to reduce bycatch

Pelagic fisheriesAmount the most sustainable and least damaging to the environmentRates of bycatch are minor compared to other kinds of fisheriesMostly going after shoaling speciesAtlantic mackerelNorth Sea herringLantern fish (Myctophids)and planktivorous forage fishSardine and anchovyCreate wasp-waist ecosystemsone or a couple species of small planktivorous fish dominate their trophic level

Controversy over pelagic fishingAnalyses of long-line data suggests that 90% of large pelagic fish may have been removed before management procedures developedPeople argue the limits for fisheries are incredibly low because they represent already-depleted stock levelsMakes restoration of stocks difficultWe dont know what the pre-exploitation biomass wasCant calculate when restoration is completedLong-line fishing is the major factor in substantial declines in albatross populationsTake the baited hooks when thrown from the ship and drown as they sink

Fishing squidAlso called jiggingJighooked coloed lures with extremely bright lightsLights can be so bright that satellites can detect themmay help to monitor and manage open-ocean squid fisheriesWhy do we care?Squid respond rapidly to changing oceanographic conditionsMay help predict interannual variations in recruitment

Regime shiftTypically take less than one year to occurmay last for decadesDriven by:Climatic changes fishing pressureOr bothPresent major challenges for scientists attempting to manage fisheriesCan be measured using CPRs(Continuous Plankton Recorder)Example of regime shiftinflux in the population of plankton in the North Sea due to an increase in nutrient-rich Atlantic waterSuspected regime shiftsIncrease in jellyfish population in many pelagic marine ecosystems Possibly in response to climate and fishing effectsHow could that be?Hint: turtlesCorrelation between abundance in jellyfish and NAOI (North Atlantic Oscillation)Also compete with herring(overfished) for zooplankton foodJelly-fish dominated pelagic communities may be one consequence of overexploitation of fish stocksScientists have detected more regime shifts since the 1990sIncidence of regime shifts may be increasing orWe may just be able to detect more changesFuture of pelagic ecosystemsDown the food webas traditional fish species are removed, fishing effort turns to smaller speciesever-increasing human population and demand for food proteinFisheries have gradually been moving farther and farther from shoreWe still suck:Removing biomass through fishingIncidence of waste is increasing and pushing species beyond their usual rangeAlien species have devastating effects on pelagic ecosystemsEx: ctenophorenative of eastern USA, led to the collapse of the Black Sea anchovy fishery because it preys on fish eggs

We suck so bad Could dump CO2 out at sea to reduce further increasing in atmospheric concentrationsOcean soundLow-frequency noise from shipping oil-exploitation, and military activities may significantly impact cetacean communication and foraging by masking their soundsKiller Whales have increased the length of their calls by about 15%, probably attempting to overcome noise generated by boats Sound underwater and ocean acidificationPropagation of underwater sound in the range of frequencies used for cetacean communications will increase as the ocean becomes more acidicChanges in ocean acidity could enable sounds to travel up to 70% fartherWill increase the levels of background noise and may affect marine mammal behavior

Climate changeThe likely state of aquatic ecosystems in 2025 will be due singularly to climate warmingHave already had impacts on sea-ice extent and zooplankton distributionCould result in multiple extinctions before the end of the centuryLargest threat: increased warming and consequent freshening of the Artic may switch off the North Atlantic Current (NAC) and damage global ocean circulationCould reduce north Atlantic plankton biomass by more than halfCould reduce global export production by more than 20%http://www.youtube.com/watch?v=kxPwbhFeZSw

YAY ITS THE END!!!:D

Good (sort of) Videos to watchhttp://www.youtube.com/watch?v=TgNeL7igtnwhttp://www.youtube.com/watch?v=8101vCjM7nYhttp://www.youtube.com/watch?v=5cqCvcX7buo&list=PLE5E6A5688B2CB642