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The Shallow Ocean

The Shallow Ocean. Factors and processes in the shallow ocean Habitats: estuaries tidal flats littoral zone continental shelf. Benthic effect. “Benthic Effect” Ocean: independent of ocean floor; vertical zones Coastal zone: Sediment, water column coupled

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The Shallow Ocean

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  1. The Shallow Ocean Factors and processes in the shallow ocean Habitats: estuaries tidal flats littoral zone continental shelf

  2. Benthic effect “Benthic Effect” Ocean: independent of ocean floor; vertical zones Coastal zone: Sediment, water column coupled Water oxygenated: algae, microbial loop Top sed oxygenated: algae, microbial loop Beneath: dysoxic to anoxic

  3. Environmental Variability Daily variability: T, salinity, tides, wind strength etc. Annual variability: Seasonality, storms Sediment input, freshwater 10’s – 1000’s yrs: Sea level change, climate change MY’s: Plate tectonics, conveyer circulation Nutrients, oxygen, carbon dioxide: daily through MY’s

  4. Estuaries Estuary: where freshwater (i.e., river) meets the ocean Requirements to be an estuary: 1. FW input 2. Open connection to ocean 3. Area of FW/SW interaction 3 zones: Tidal river zone; mixing zone; nearshore turbid zone

  5. Estuaries: Ecology Very productive and very sensitive habitat High biomass: plants, microbes Large nutrient, sediment flux Fish nurseries Depth, salinity, T vary w/ seasonality, tides, FW Qin Can have FW top, SW benthos Seasonal variations Pollutant filter

  6. Example: Laguna Madre Shallow: most <1m deep with 0.5m tidal range Tides 2X day Inlets on each end of barrier island Reversed salt wedge Hypersaline, high evaporation TX weather: varies between arid and monsoonal storms

  7. Example: Laguna Madre Sea grass behind barrier island Invertebrates: oysters, clams, polychaetes, crabs; fish Sand and euryhaline succulents on barrier island Sea birds, feral cats, rattlesnakes, rodents, insects Barrier island stabilized, not allowed to migrate

  8. Example: Chesapeake Bay Drowned river valley since LGM Major fishery: oysters, crabs, fish Oysters where FW, SW meet and mix 1900: enough oysters to recycle H2O in 3 days now: 1.5 years

  9. Example: Chesapeake Bay Seasonal stratification, anoxia Spring: a lot of FW: strong pycno- and halocline Stratification: anoxia on bottom Seasonal variations in biomass, communities

  10. Mangroves Tropical estuary Trees instead of marsh Important nursery habitat, local fishery Clear cut for development, aquaculture

  11. Littoral Zone Within tidal range Effected by beach processes, sediments Rocky or sandy High energy environment Organisms: Infauna common: polychaetes, molluscs Mussels, limpets, chitons, arthropods Communities: Algae gardens, sea grass beds, infauna patches, hard surfaces

  12. Example: Bathtub RockLa Jolla, CA West coast: erosional: hard surfaces Uneven sour --> pools of water, rough sides “Bathtub” on top

  13. Biotic zones Low tide: rock is exposed Mussels closed tight Vagile organisms still Crabs at work Exposure to predators High tide: rock sides under water, but high E Organisms feed, vagile critters move and feed

  14. Shallow Shelf Many invertebrates, vertebrate organisms Algae if shallow enough Floating algae: Sargasm Attached algae: Kelp Complex food webs: types producers + sessile benthos + vagile predators Storm events --> stable environment with occasional perturbations

  15. Example: Offshore CA Shallow shelf: active margin Upwelling in spring, summer Cold water, oxygen, nutrients Plankton bloom --> albacore, others --> sharks Kelp forests Sea urchins, lobsters, diverse attachers, benthic inverts fish, seals, sea otters, killer whales Fairly stable environment, complex food webs

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