An inter-tidal ecosystem: a salt marsh
Salt marsh = coastal wetlands where ocean meets the land, common in mid-high latitudes.
Form in sheltered estuaries where shallow water covers a low coastal gradient. Affected by
incoming (flood) and outgoing (ebb) tides which cover and expose the marsh.
Sediment accumulation from eroded material moves via fluvial transport and flocculation of
clay particles provides nutrient source. Water is mixed by regular tidal movements.
Green algae live on mudflats and rooted plants (glasswort) grow on marsh surface.
Crustaceans and molluscs live on mudflats, fed on by wading birds (curlew and oyster
catchers).
Goby fish inhabit shallow creeks.
Phototropic bacteria decompose plant matter for consumption by worms and molluscs.
Plant succession = the sequence of changes within a plant community as it develops
through time.
Halophyte = Salt-tolerant plant.
A deep-water ecosystem: the Antarctic
Despite low temp, high concentration of dissolved oxygen increases productivity.
Phytoplankton blooms in summer due to long photoperiod (12+hours) and nutrient-rich
surface waters.
Nutrient transfer through upwelling:
• Sea ice forms, increasing salinity and density.
• Surface waters cooled to below 0 degrees as saline water has lower freezing point.
• Cold, saline water sinks, and less saline/dense water rises with nutrients such as N
and Si.
• Phytoplankton use nutrients for growth.
Squid feed on primary consumers (zooplankton and krill). They provide food for sperm
whales, seals, fish and seabirds.
The physical environment greatly influences the ecosystem due to physical changes in the
extent of sea ice (February = 3mil km2
, September = 20mil km2
)
Marine food webs are relatively simple as biodiversity is lower.
e.g = Phytoplankton, krill, feeding whales