Estuarine Shores Flashcards
Global Patterns
More soft sediment beaches in the tropics.
Related to coastal climate, freshwater inflow and glaciation history.
Local patterns
Soft shores are inhabited by mobile epifauna and infauna
Porosity and permeability
Porosity, volume of pore space in between particles.
Permeability, rate of percolation of water through the sediment.
Water content and mud
Water content related to parcel size, beach profile and water table height.
Dilatant sands:
- When pressure applied, the sand becomes dry and hard pack as water driven out of the interstices. Difficult to borrow.
Thixotrophic sands:
- Sands with high clay content, easy to burrow.
Muds:
- Do not drain and saturated with water. Easy to burrow
Oxygen and sediment chemistry
Aerobic bacteria decompose organic material at the surface when oxygen is abundant.
Oxygen consumption at the surface deprives deep layers of oxygen, so sediments below the surface are anaerobic.
Depth of oxygenated layer varies according to grain size, which determines permeability.
As oxygen concentrations diminish with depth anaerobic bacteria start to dominate.
Transition layer between oxygen rich and oxygen poor layers is the redox discontinuity layer.
Burrowing animals generate a respiratory current within their burrows to receive oxygen.
Macrofauna
Generally, no macroalgae, but sometimes see blooms of Enteromorpha and Ulva on mudflats.
Macrofauna: amphipod and arenicola, deposit feeders.
-Shore crab, heart urchin, lanice, cerianthus, sagartia, nereis, grazers.
Meiofauna
Detritus, bacteria and diatom feeders
Food for higher trophic levels
Macrofauna vs particle size
Species richness, abundance and total biomass increase with increasing sediment stability, decreased wave exposure.
Highest in muddy/sheltered habitatts.
Macrofauna vs tidal heigh
Lack of distinct vertical zonation.
Sediments buffer physical stress and the organisms are mobile.
Organisms burrow deeper in the intertidal.
Distribution related to particle size, emersion period, depth of water table.
On sandy shores, zonation schemes have been related to hydrodynamics.
Not just invertebrates
Burrowing fish.
Rays, eels, and band fish.
Evolutionary history of fauna
Cambrian animals primarily lived in the surface and often no more than 10cm depth.
Somehow Ordovician-Devonian fauna created extensive and deep burrows.
However, most Paleozoic fauna are epifaunal.
Infaunalization goes large scale in the Mesozoic.
Biostabilisers
Increase cohesiveness.
Make sediment surface smoother.
Form protective layer over sediment surface.
Bioturbators
Make sediment surface rougher.
Regrade sediment particle structure.
Reduce sediment strength.
Oxygenate sediment.
modify geochemistry profiles.
Often exclude filter feeders.
What is an estuary
Extended interface between a marine and freshwater flowing system.
Estuarine fauna
Invertebrates dominate epifauna and infauna.
Fish typically use estuaries as nursery grounds or move in with tides.
Birds are migratory visitors are all trophic levels.
Plankton, mainly diatoms and dinoflagellates.
Salinity profile
Balance between volume of river flow and strength of tide, water density.
Variation horizontally and vertically.
Salt wedge, partially and well mixed
Biological effects of varying salinity
Oncotic pressure, pressure which needs to be applied to a solution to prevent inward flow of its pure solvent across a semipermeable membrane.
Water loss in high salinity, crenation.
Physiological adaptations
Osmoconformer, equal osmotic P to surrounding water.
Osmoregulator, regulation of osmotic P within cells. Uptake/excretion of salt ions.
Behavioural adaptations
Move with tides
Bury head in sediment.
Human impacts
Estuaries are highly impacted by humans.
- historically settled due to sheltered, easy access to sea.
- Harbor construction and dredging, large scale modifications and perturbation.
Climate change
Acidification
Habitat alteration
harvesting
Invasive species
Freshwater inflow.
Pollution
Effluent, nutrient enrichment to eutrophication
Other pollutants including antifouling agents and industrial/agricultural run off.
Freshwater inflow
Colorado river:
14 main dams, no water reaches the gulf of Cali since 1960
Major impact on organisms
Impact on food web as clam species has been wiped out as it likes brackish water.
Totoaba need upper estuary water for nursery and early growth.
Totoaba now have slow growth rate, decreased population growth rate, endangered, later sexual maturity
