Exam 4 Friday April 10 2015 7 49 PM Part 3 Survey of Marine Ecosystems 3 25 15 A Coastal Ecosystems 1 Estuaries 2 Intertidal 3 Coral Reefs 4 Continental Shelf B Open Ocean Ecosystem C Special Marine Ecosystems 1 Deep Sea 2 Polar D Humans and Marine Ecosystems 1 Estuaries A What is an Estuary B Physical Characteristics C Types of Estuaries D Productivity E Challenges for Life in an Estuary F Communities Associated with Estuaries A What is an estuary Where rivers meet the sea Mixing of FW and SW Often highly productive Constant environmental change Shallow sunlight nutrients Ecological roles Nutrients to sea Nursery for many young animals Humans benefit greatly 85 of commercial fish and shellfish of world spend all or part of lives in estuaries Oysters shrimps flounder fluke tarpon striped bass Inlet in the ocean that extends into a river valley as far as the upper limit of the tide B Physical Characteristics Often form in embayment s partially cutoff from the sea Rivers streams carry from FW from land and mixes with SW All estuaries Partially isolated from the sea by land Diluted by FW C Types of Estuaries There are a variety of ways that freshwater and sea water are mixed along the ocean edge i e forming estuaries Estuaries can be categorized according to their geologic history how they were formed Coastal plain tectonic fjord bar built Can be categorized according to the pattern of FW and SW mixing Salt wedge well mixed partially mixed 1 Coastal plain drowned river valley Between glacial periods Water floods low lying plains and river basins Chesapeake Bay Long Island Sound Narragansett Bay 2 Tectonic estuary Earthquake causes land to sink SW covers San Francisco Bay 3 Fjord Glaciers cut deep valleys in coast Filled with water forming fjords Scandinavia 4 Bar built Currents and tides deposit sediment on seaweed side Barrier island Cape Hatteras Texas coast Satellite images of three types of estuaries a two coastal plain estuaries on the US East Coast b several bar built estuaries and c steep sided fjords Negative estuary FW evaporates more quickly than replaced and inward flow of SW over the top of FW Gradient of increasing salinity moving from river to sea Salinity mixing patterns variable among estuaries Tidal overmixing Dense SW sinks as lighter FW rises causes mixing FW flow seaward over the top of more dense SW Most estuaries are positive estuaries of this type Types of estuaries by mixing 1 Salt Wedge 2 Well mixed 3 Partially mixed 1 Salt wedge estuaries Mouths of rivers flowing into SW FW flows rapidly out to sea at surface SW flow upstream along river bottom FW flow rapid and prevents SW from entering further Wedge moves in and out of river basin with rising falling ride One way exchange from SW to FW 2 Well mixed River flow low tidal currents major role in circulation Seaward flow of water and uniform salinity at all depths Salinity decreases as water approaches river Delaware Bay 3 Partially mixed Strong surface flow of FW and strong flow inward of SW High productivity of estuaries long known Freshwater runoff brings nutrients N Si SW brings other nutrients P Light nutrients for not that high of primary productivity D Productivity Most of input into trophic webs is as detritus Organic matter in estuaries may be 100x of open ocean Detritus in estuarine mudflat can support 10 times more biomass than offshore sediments Sediments and organisms have high capability and retain nutrients and organic matter Estuaries as nurseries Excellent habitat for young of many spp High level of nutrients Lower number of predators All of those commercially and recreationally valuable fish and shellfish Bluefish Young feed in estuaries Most of life spent in SW Move to SW to develop Striped bass spawn at border of FW and salinity E Challenges for Life in an Estuary Estuaries characterized by two types or organisms those from FW and those from sea water SW Highly productive ecosystem good place to live However organisms inhabiting estuaries face two major challenges resulting from the dynamic nature of the environment 1 Highly variable salinity 2 Challenge to osmoregulate 2 Water movement Strong river and tidal currents Challenge to maintain position 1 Highly variable salinity Salinity of most of the ocean fairly constant The salinity of estuarine water can change very quickly FW invaders must tolerate elevated salinity and marine invaders must tolerate low salinity Most estuarine animals are euryhaline tolerate broad range of salinity Most estuarine invertebrates are osmoconformers 2 Water movement strong river and tidal currents Water in estuaries almost always moving rivers out tidal current in and out Many benthic plants and algae have extensive root systems rhizoids stolons holdfasts to anchor Small amount hard substrate to attach to to bottom Temps in estaury may fluctuate greatly 3 Temperature Water is shallow changes temp rapidly with air temp Surface water may be cooler in winter than water below resulting in sinking of cooler surface water and winter turnover and vertical mixing 4 2 15 Prominent mollusk in temperate estuaries Free swimming larvae attach to solid substrate F Communities Associated with Estuaries 1 Oyster Reefs Usually at right angles to tidal current and at lower salinity regions of estuary Oyster reefs habitat for many other organisms Extensive oyster beds in estuaries along the US east coast Delaware Bay Currents deliver nutrients remove wastes Sediments accumulate sand silt and clay mud good at trapping nutrients detritus 2 Mudflats Often associated with estuaries less water movement Where water movement reduced Primary production energy into ecosystem Some by anaerobic bacteria Rich In bacteria that use SO4 for energy chemosynthesis Many produce H2S rotten egg smell Other major primary producers diatoms algae sea grasses 2 Mudflats Primary Producers Three main primary producers 1 Diatoms Coat mud with golden brown film Food source for many small invertebrates 2 Large algae 3 Sea grasses Turtle grass Eel grass 2 Mudflats Animals Green mats often attached to hard substrate rocks shells wood Fed upon by herbivores worms amphipods crabs Burrowing animals shrimp clams worms Abundant lugworms innkeeper worms ghost shrimp By burrowing Protected from predators Sheltered from drying sun at low tide Salinity of mud fluctuates less than overlying water Feeding strategies Suspension feeders infauna near surface when under water deposit feeder eat mud sediments and extract