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UMass Amherst GEO-SCI 103 - Pelagic and Benthic Ecosystems

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GEO-SCI 103 Lecture 17Outline of Current Lecture: Pelagic and Benthic Ecosystems pages (192-195, 198-205)I. Benthic Life Along the CoastA. Low Energy EnvironmentsB. High Energy ShorelinesC. Salt Marshes and Mud FlatsD. Mangrove SwampsE. BeachesII. Open Ocean (“Blue Water”) Ecosystems A. Open Ocean has lower productivity than Coastal Environments B.Primary ProductivityC.Animals Below Photic ZoneD.Pelagic Life in the Open OceanIII.Benthic Life in Deep seasA.Least known part of the earthB.Low biomass communitiesC.High biomass communitiesIV.Fishing and OverfishingA.Advances in TechnologyB.Bottom TrawlingC.BycatchD.Solutions to OverfishingV.Fisheries and AquacultureA.AquacultureCurrent LectureI. Benthic Life along the CoastRocky shore environments are highly zoned with respect high and low tides, and are dominated by epifaunal organisms. Sandy shores show much less prominent biological zonation and contain more infauna. A. Low Energy Environmentsa) Usually protected from direct action of wind wavesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.b) Tidal changes help in distribution of nutrients and oxygen and also cleanse waste materials from environmentc) Organisms that live in these conditions must be tolerant of sediment that accumulates (salt, clay, organic matter, short supply of oxygen)B. High Energy Shorelinesa) Receive direct force of waves from ocean b) Salinity and oxygen are readily available, but organisms must adapt to constant pounding of surfC. Salt Marshes and Mud Flatsa) Low energy fertile oases where abundant nutrients permit vital communities to thrive b) Presence of abundant sea grasses such as eel grass and turtle grassc) Rich food web and also provide physical protection for an array of animals that live among themd) Animals that live there remain buried and survive by deposit feeding or filter feeding D. Mangrove Swampsa) Specific variety of low energy coastal environment that is restricted to tropical latitudesb) Trees that have adapted to life in brackish and saline waterc) Red mangrovemultiple legs that allow the tide to wash through and around itd) Black mangrove sends out shoots above water line that allow it to obtain oxygen more easilyE. Rocky Shoresa) Example of high energy environment where exposed bedrock is pounded by surfb) Animals attached to rocks and seaweedc) Epifauna that have developed mechanisms to hang on to their positionsdespite rough conditions d) Examples: Periwinkle snails, barnacles, mussels, attached algaeF. Beachesa) High energy environment that is dominated by soft and mobile sedimentb) Numerous infaunal organisms such as clams, crabs, wormsc) Also various examples of epifaunal organisms such as snails, sea stars II. Open Ocean (Blue Water) EcosystemsA. Open Ocean has lower productivity than Coastal Environments a) Distribution of life in open ocean is controlled by the availability of an energy source (solar radiation or chemical energy) and nutrientsb) Greatest concentration is in sunlit watersc) Many animals live close to their food source in the upper water columnd) Phytoplanktonzooplankton (grazers and predators)nekton (fish)bigger nektonB. Primary Productivitya) Supported by external supply of nutrients such as river borne nutrients in coastal waters or upwelled nutrients in open ocean divergencesb) Characterized by regenerated production which refers to productivity sustained in an internal supply of recycled nutrients released by bacterial degradation within the photic zonec) Blue water ecosystems=no turbidity, scarce nutrients, low phytoplankton biomass1. Cannot sustain large communities of animal zooplankton and fish due to scarce nutrient supply C. Animals below Photic zonea) Below the depths of living phytoplanktonb) Depend on various forms of detritus (dead and decaying aggregates of organic matter and fecal material raining down from above)c) These are particles known as marine snow because of how they appear when viewed by submersibles under artificial lightd) Include plant material from land and coastal waters is transported from shallower waters to deep parts of the ocean by turbidity currentsD. Pelagic life in the open ocean Photosynthetic plankton and cyanobacteria, limited only by the availability of nutrients and solar radiation, support life at all levels in the pelagic zone of the open ocean via the rain of organic matter into deeper waters. (examples: diatoms, squid, epipelagic fishes, sharks, dolphins, large whales)a) Subtropical gyres are vast regions with low nutrient levels in contrast to the high productivity of the continental margins and divergent upwellingb) Below the photic zone the size of the biomass is controlled by the downward flux of organic matterc) This is the marine nutrient cycle or the biological pumpd) Photic zone is the region where there is enough solar radiation to power photosynthesis 1. grazing food chain in photic zone: phytoplanktonzooplanktonnektonbigger nekton2. In low nutrient waters, the base of food chain consists of cyanobacteria, the higher nutrient level waters contain more diatoms and dinoflagellatese) The dysphotic and aphotic zones have very low solar radiation and no photosynthesis1. Detritusnektonbigger nekton2. Low biomass3. Many organisms have bioluminescence which allows them to find other of their kind in low light environment or to lure preyIII. Benthic Life in Deep SeaA. Least known part of Eartha) Great depthsb) Eternal darknessc) Low temperaturesd) Lack of availability of foode) Detritusscavengers and deposit feedersnektonB. Low Biomass communitiesa) Found on abyssal plain where food is scarce b) High diversity of animals, protists and bacteriac) Stable over long time: specialized in portioning the limited recourses available to them C. High Biomass communitiesa) Suboceanic environment b) Under areas of high surface water productivity (regions of equatorial upwelling)c) Hydrothermal vent communities’base of food chain is chemosynthetic bacteria. Abundant food with locally high biomassIV. Fishing Technology and OverfishingA. Advance of fishing technologya) Technology advancements and ruthless efficiency and demand for fish as food recourse has increasedb) Many species showing declinec) Maximum sustainable yieldamount that can be safely harvested without destroying an entire species. If this is


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UMass Amherst GEO-SCI 103 - Pelagic and Benthic Ecosystems

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