1 / 35

Productivity of Estuarine Habitats

Explore the factors influencing the high productivity of estuaries, their critical role in fisheries, and sensitivity to human impacts. Learn about sediment trapping, nutrient cycling, and biodiversity in these unique ecosystems.

nancywest
Download Presentation

Productivity of Estuarine Habitats

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Boundary Habitats Estuaries

  2. Interactions among physical parameters Seasonality

  3. Characteristics of biological communities: Marsh habitats • Generally, high density but low diversity • Physiological stresses • Low topographic & substrate variability • But very high potential for productivity due to nutrient input

  4. Components • Macrophytes (seagrasses, sedges, rushes, cordgrasses) • Epiphytic algae (macro- and micro-) • Benthic macroalgae and microalgae • Phytoplankton

  5. Estuary edge zonation in marshes

  6. High primary productivity • E.g., may have >4000 plants per meter square • Second only to tropical rainforests in productivity, among natural ecosystems

  7. High secondary productivity • Benthic macrofauna dense • Clams, annelids, crustaceans • Critical for coastal fisheries • Used as nursery areas for many pelagic spp • Approx 2/3 of fishery derived from nursery areas in estuaries • What factors influence this productivity?

  8. Questions: • Why are estuaries so productive? • How are offshore fisheries impacted by estuary quality? • What limits productivity? • How are estuaries sensitive to anthropogenic stress?

  9. Why are estuaries productive? • Nutrient trap • Tides provide an energy subsidy for the resident aquatic species • Autotrophs are present all year • Combination of freshwater and saltwater creates many different habitats

  10. Variety of habitats

  11. Physical complexity of an estuary basin Shallow Water Open Water Deep Water Deep Channel A. Cross Section of Chesapeake Bay or Tidal Tributary Migratory Finfish Spawning and Nursery Habitat B. Oblique View of the “Chesapeake Bay” and its Tidal Tributaries Shallow Water Habitat Open Water Habitat DeepWater Deep Channel

  12. Freshwater links with estuaries

  13. Sediment trapping in tributaries

  14. What happens to stream input? • Nutrient (sediment) trap effects due to physical factors • Settling with dispersion of water flow • Nutrients adsorbed on clays • Flocculation • pH & salinity change • alter electrostatic charges • water & small particles attract • increasing particle size and • tendency to settle

  15. Biotic sediment trapping: plants Spartina - cordgrass

  16. Plant effects in estuarine productivity • Sediment trap effect due to reduction of flow velocity • Nutrient pump effect • Nutrients taken by roots from sediments • Transferred to water column (for phytoplankton) • Nutrient modulation effect • Uptake when nutrients are abundant • Net release back to water when nutrients are scarce (through decomposition)

  17. Biotic sediment trapping: animals • Biodeposition • Filter feeders collect suspended matter, compact it • “Clearance rates” can be very high; 10’s of liters per day per clam or oyster

  18. Factors enhancing productivity: Tidal mixing • Ebb & flow of tides enhances settling of sediments/nutrients • Resuspension of materials can enhance phytoplankton productivity

  19. Factors affecting light & productivity

  20. Links between estuaries and fisheries • Fisheries classifications • Economic • Commercial • Recreational • Subsistence • What is being harvested • Arthropods (crabs, shrimp) • Molluscs (clams, oysters) • Fish

  21. Offshore fisheries depend on estuaries • 70 – 90% of commercial catch from east coast of USA is estuarine dependent • Fishery productivity is correlated with area of marsh and vegetated habitat

  22. Example of fisheries in North Carolina estuaries • Arthropods • Blue crabs ($40 million) • Shrimp ($20 million) • Mollusks • Oysters 1988 peak of $3 million, now <$1 million) • Clams also declining, from 1980 $8 million • Fish • Menhaden, flounder, croaker, weakfish > $24 million • Recreations catch can exceed commercial

  23. Estuaries and fisheries, an example

  24. Estuaries are especially sensitive to human impacts • Sediment trapping can be problematic • Tradeoff between adding nutrients and increasing turbidity • High sediment loads clog filtering systems of animals • Sediments carry pollutants (dredge spoils of Cape Cod harbors are “toxic wastes”) • Filter feeders tend to concentrate toxins • Estuaries are the “First stop” for poor agriculture and waste management

  25. Other reasons for estuarine sensitivity • Vulnerability of estuarine organisms • Many already at the limit of physiological tolerances • Added stress of chemicals, hypoxia may reduce reproduction below critical limits • Food web structure is based on few species • Low diversity is high risk

  26. SedimentSources to the Bay and Tribs • Watershed Inputs (1,2 and 3) • Shoreline erosion (4) • Ocean (5) • Biogenic production • Relative contribution varies in proportiondifferent areas of the Bay and tribs

  27. Sediment transport in Cheasapeake Bay

  28. Sediment Budget – Choptank Estuary 1979-80 (Yarbro et. al, 1983) 12 % Upland 8 % From estuary 80 % Shoreline 81 % Deposited 19 % Transfer downestuary Total Sediment input 0.43 x 106 metric tonnes

  29. Why They Are Being Destroyed • Level of habitat loss is ~ 80 to 95% • Many factors contribute to this destruction • Storm sewers are difficult to regulate due to old infastructure (EPA study)

  30. Information about Stormwater • More oil than was released in the Exxon Valdez spill flows into Galveston Bay per yr • One quart of spilled motor oil covers three football fields • Takes 20 years for an aquatic system to recover from oil contamination • In the Chesapeake Bay, 15% P, 14% N, and 9% of sediment loads come from storm water

  31. Stormwater Pollutants • Suspended soilds from steet dust and eroded sediments • Heavy metals from motor vehicles—wear of plating, bearings and brake linings • Chlorides from salt application • Oils, grease and other hydrocarbons from vehicle exhaust and lubricants

  32. Potential PoliciesVegetated Shoreline Buffer Zones • Improve water quality, create new habitat • Difficulties: waterfront land values are expensive, need to remove existing buildings, political opposition, reluctant governments

  33. Potential PoliciesBest management practices (BMPs) • Advanced • Detention ponds • Vegetated filter strips • Catch basin filters… • Baseline • Preventive maintenance • Education…. Detention pond

More Related