L4 - Estuarine and Soft-sediment Ecosystems Flashcards
What are estuarines?
Areas where freshwater inputs meet the sea
Where are estuaries?
Scattered along the world’s coasts.
What do estuaries vary in?
Vary considerably in their origin, type and size
What are some different types of estuaries?
Drowned river valley, Fjord, Bar-built estuary, tectonic estuary
What is a halocline?
Salinity gradient, average seawater salinity ~35 psu/ppt, freshwater salinity = nearly 0 psu/ppt
What is a isohaline?
Line of uniform salinity
What are the major physical characteristics of estuaries?
Salinity, substrate, other physical factors (e.g. temp, turbidity)
What factors effect salinity distribution?
The tidal regime, the shape of the estuary, wind, seasonal variation, temperature
How do tides effect Salinity?
Salinity varies with depth, same location at different stages of tide
What is the substrate of estuaries?
Sand or soft mud. Mud is still rich in organic material, bacteria in the mud respire and use up oxygen, much of estuary sediment is anoxic
What is the level of diversity in estuaries?
Lower diversity, but higher biomass
What extremes do species have to deal with in estuaries?
Salinity, temperature, desiccation, oxygen depletion
Do other marine environments experience such changes in salinity?
No
What are the classifications of marine species by salinity?
Stenohaline, Euryhaline, Brackish, Freshwater
What are Euryhaline marine organisms?
Most estuarine organisms, tolerate a wide range of salinities
What are Stenohaline marine organisms?
Few by comparison, tolerate a narrow range of salinities, might penetrate into the estuarydown to 30ppt, but do not grow or divide below the salinity.
What are Brackfish marine organisms?
Estuarine species not found in the sea occur up to 30ppt, but optimum for growth is 3-10ppt
By what ways do organisms cope with different salinities?
Osmoregulation, osmoconformers, osmoregulators
What is osmoregulation?
The process of maintaining salt and water balance (osmotic balance) across, membranes in the body.
What is osmoconformers?
Allow their body fluids to change with salinity
What is osmoregulators?
Regulate the concentration of solutes in their body to keep salt concentration constant.
Do some organisms switch between methods of coping with salinity?
Yes
How do estuarine plants cope with salinity changes?
Grasses and some salt marsh plants have a high salt tolerance, they can absorb salts and concentrate sugars to prevent water leaving tissues. Cordgrasses (spartina) create salt through salt glands in their leaves. Pickleweed/glasswort (Salicornia) absorb water to dilute the salts they take up.
Soft-bottom communities - What are primary producers?
Seagrasses can produce large intertidal beds. Few seaweeds - the substrate is shifting and unstable
Soft-bottom communities - Epifauna vs infauna?
What species are supported and the conditions they live in depends on the kind of sediment, particularly the grain size
Soft-bottom communities - Sediments?
Size of sediments dictate their properties. Well-sorted (coarse) water drains quickly. Well-sorted (fine) water drains slowly. Poorly sorted, water blocked
Soft-bottom communities - What are the benthos by size?
Microfauna < Meiofauna < Macrofauna
Soft-bottom communities - Where do benthic meiofauna live?
Between the sediment grains, can be a good indicator of environmental conditions
Soft-bottom communities - Where do infauna burrow?
Into sediment, Lugworm (Arneicola marina), Cockles (Cerastoderma edule)
Soft-bottom communities - What does the high biomass bring to estuaries?
High biomass, particulary of invertebrates brings species of birds which are often on migratory paths.
What are open-water communities?
Many marine species get brought in with the tides, leads to a rich supply of fish and shell fish - and productive fisheries. However, very few fish species spend their lives wholely within estuarines. Golden grey mullet (Chelon auratus), european eel (Anguilla anguilla)
