Chapter 5: Etuaries Flashcards
what are the four size gradients of tides?
Microtidal 6m
what are the five zones of the estuary, and their salinity?
1: Head,
what are the four environmental variables of estuaries?
salinity
sediment
DO
temp
why do estuaries typically have low DO concentration?
due to anaerobic bacteria in the mud.
–> breaks down OM, can result in methane or hydrogen sulphide
what is the importance of temperature in estuaries?
- can be a trigger for reproduction or migration
- can be more important than salinity
- influence the speed of bacteria breakdown
what are the 3 scenarios for colonization of estuaries after glacial retreat?
- REFUGIA: recolonization by organisms similar to those present before glaciation
- REMAINED IN BRACKISHWATER: in lower latitudes then re-colonized higher latitudes
- NO REFUGIA: evolution after each post-glacial period
Estuarine organisms originated from which two possible sources?
- FW origin extending into estuaries from rivers
- Marine sp. colonizing estuaries from the sea
why must a species be resilient to live in estuary environmets?
environements are dynamic, stressful, and produce strong evolutionary selection forces.
what are the three most abundant FW groups to colonize estuaries?
- Oligochaetes most successful
- Fish
- Pulmonate molluscs
what are the prevalent species groups of the mudflats?
- polychaetes
- oligochates
- small crustaceans (amphipods)
- benthic diatoms
hyperosmotic
uptake of water by organism which has an internal fluid concentration greater than surrounding water
osmoconformer
- little if any ability to osmoregulate
- high tolerance to diluted blood concentrations
which species group are the most efficient osmoregulators?
Crustaceans
Organisms found in the most variable conditions within an estuary are not necessarily the most sophisticated osmoregulators, but simply the most ________.
tolerant
______ enables organisms to adapt to various salinities even with limited osmoregulatory capabilites
Physiological plasticity
what are impacts of increased FW inflow?
-large decrease in salinity
-can boost estuarine productivity
ORGANISMS CAN:
-tolerate changes
-migrate/drift
-die
what are impacts of reduction of FW flow?
-upsteam movement of spp
-increase in salinity upstream can have dramatic effects
-productivity of estuary affected
(meiofauna, phytoplankton)
name factors influencing fish communities in estuarine habitats
- water temp main one
- DO
- habitat complexity
- variations in climate
low plant biomass and 1* productivity. EXCEPTIONS:
seagrass beds
systems at outer estuaries (mangroves, saltmarshes)
production is dominated by what?
detritus.
due to organic carbon in sediment of mudflats
where does the detritus come from?
marine (algae by tide)
semi terrestrial (saltmarshes)
terrestrial (leaf litter etc)
why is the huge number of detritivores important to the food web?
supports fish and birds, influences trophic interactions
how do estuaries influence birds?
key feeding areas, especially for migrating spp.
how do birds influence estuaries?
- major bioturbators
- some cases re-work top sediment 8 times in 3 months
- eat roots as well as leaves
foraging birds:
what does it mean, ‘ideal free distribution’
that the birds have non-uniform distribution. They are free to go where the rate of reward is the greatest. good patches with higher competition, less suitable patch with less competition.
General description of saltmarshes
- mostly exposed to air
- submerged @ high tide
- areas vegetated by herbs, grasses or low shrubs
- top end of mudflats
- plants play an important role
what are the function of the saltmarsh?
- reproduction area
- refuge (environmental stress, predation)
- foraging area
how do tropic estuaries compare to temperate?
temperate: newer due to glaciation, less effective evolutionary time.
tropic: older and more diversification. hypersaline due to intense evaporation.
what is the spp diversity like in estuaries compared to other regions?
less diversity, as less species are able to survive harsh conditions.
hyposaline seas
Baltic Sea (quick overview)
- similar range of spp as estuaries
- no tides and a stable salinity
- allows further penetration of spp into lower salinity areas
- a mixture of FW and Marine species unlike anywhere else worldwide
Hyper saline waters
- coastal
- salinity >34
- evaporation rate > inflow of FW
- decrease diversity with increase salinity from 34
what is an example of a hypersaline water, and some features.
Crimea peninsula
- long, thin, isolated by land barrier
- limited water exchange
- minimal tides
- organisms originate from sea
Lagoons
-very shallow
-wide range of salinity
-diverse submerged plant community
-small areas of sea semi-isolated by a barrier
-deposition of sand:
begins offshore, builds a barrier w/o connecting to land, or barrier extends from the land.
when were most estuaries formed? 6
6-10000 years ago (last ice age)
where can most of the best osmoregulators be found?
in the mud
