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Marine Biology > Lecture 23- Life in estuaries > Flashcards

Lecture 23- Life in estuaries Flashcards

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1
Q

What is an estuary?

A

– tidal-influenced lower part of river and its valley – sink for both fluvial & marine sediments -estuaries are relatively sheltered, low energy environments

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2
Q

What is a delta?

A
  • composed of river- derived sediments
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3
Q

What are the key physical factors affecting the biota in estuaries? (3)

A
  1. Salinity (levels, fluctuations) 2. Temperature (fluctuations) 3. Sediments (suspended, benthic)
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4
Q

Does salinity differ a lot in estuaries?

A

-yes, over small temporal and spatial scales -organisms need to be adaptive to survive

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5
Q

What are stenohaline marine species?

A

-tolerate narrow range of salinities

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6
Q

What are euryhaline marine species?

A

-tolerate side range of salinities -most common in estuaries

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7
Q

What are brackish water species?

A

-tolerate saline waters but lower salinity than full sea water (35ppt)

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8
Q

What are freshwater species?

A

-low salinity tolerance

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9
Q

What is the distribution of types of salinity tolerance species in estuaries?

A

-

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10
Q

What is an osmoregulator?

A

-regulates internal ion concentrations

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11
Q

What is an osmoconformer?

A

-internal ion concentrations change with ambient salinity

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12
Q

Can a species be both an osmoconformer and an osmoregulator?

A
  • yes -eg. crab: bit of each, at low salinities= conforming,
  • in inbetween salinities= regulating,
  • when salinity high= conforming
  • strategy varies with the outside conditions
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13
Q

What is an example of a perfect osmoconformer?

A

-polychaete worm= almost the perfect osmoconformer, energetically easier option provided your internal structures can cope with it

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14
Q

What are two examples of perfect osmoregulators?

A

-salmon and eel= almost perfect osmoregulators= hard work in a physiological sense

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15
Q

What are characteristics of mangroves?

A

-trees and shrubs -halophytes= salt loving -adapted to conditions in mid-high intertidal -usual tropical but have them in Victoria

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16
Q

What are the 4 ways in which mangroves cope with salt?

A
  1. Reduce salt intake= have selectively permeable surface of roots 2. Reduce water loos=via leaves, fewer stomata, don’t let water evaporate as much 3. Isolate salt=for the salt that gets in, isolated in cell vacuoles, pump it into older leaves so when they are shed the salt is dispensed with 4. Increase salt loss= via leaves, have salt glands that exude salt to the outside, encrusted salt on the surface then falls off
17
Q

How do marine fish cope with salt water?

A
  • body fluids are less concentrated than seawater
  • thus water loss via osmosis
  • marine fish are always battling losing water
  • to prevent it they drink water
  • then get more salt in than they want
  • so they excrete lot of urine, to try to get rid of the salt
18
Q

What are the behavioural strategies of species living in salty water?

A

-mobile species:change longitudinal position within estuary, change position within water column -sessile or sedentary species: hide in burrows or close shells -deep in the sediment the salinity does not change very much -on the top it does change -burrowing is very helpful when tide changes so you escape change in salinity -bivalves= close the shell and keep water out so you control internal environment -some mussels can stay closed for a couple of months= salinity control

19
Q

What are the temperature conditions in estuaries?

A

-can vary greatly -shallow depths= varies very quickly -large surface area -variability is exacerbated by tides

20
Q

How does Northern Pacific seastar deal with temperature and salinity?

A

-can withstand: 19-41 ppt salinity (28.5-34.5 ppt for reproduction) -temperature: 0-25C (5-23C for reproduction) -but larvae survive in 35ppt only if temp is low -few larvae survive 34 ppt at 20C -strongly adaptive, strongly euryhaline end eurythermal, but larvae not as tolerant, can survive in full sea water only if the water is colder

21
Q

What are the sediments in estuaries like?

A

-much fluvial in origin -mostly rich in organic material -transport of nutrients

22
Q

Does sand have different grain sizes?

A

-yes -wentworth classification -really fine= mud -then fine sand, medium sand etc. eventually boulder -the type of sand can indicate what species will be present as many have different preferences

23
Q

What is space between grains important for?

A
  • for organisms
  • circulation of water, dissolved nutrients and gases
  • sorted= how uniform the grain size is
  • well sorted (coarse)= water drains quickly
  • well sorted (fine)= water drains slowly
  • poorly sorted(uneven grain size)= water blocked
24
Q

What is bioturbation?

A

-biota disturbs the sediment and allows oxygen in etc. -biota is very important for turnover of sediments -may ingest/excrete sediments and associated organic matter -may actively irrigate burrows -increase water-sediment interface

25
Q

What are ghost shrimps important for?

A

-ghost shrimp- have burrows -up to 58cm high -help with sediment turnover, the edges of the burrow are chemically are different than therest of the sediment as it is open to air and water= so will help oxygenate the sediment and help with nutrient exchange -makes a difference to organisms living in those sediments

26
Q

What are anoxic sediments?

A

-low in oxygen in sediments -reduced circulation + decay of organic matter -black in colour -rotten egg smell -little biota

27
Q

What do suspended sediments do?

A

• Reduce penetration of light needed for photosynthesis • May clog feeding mechanisms of filter feeders -murky water= suspended sediment if too much sediment then too bad for filter feeders -bigger grains settle quickly -fine sediment hangs around for a long time before settling

28
Q

What is the productivity and nutrient level in estuaries?

A

• High primary productivity –nutrients carried in by tide & river –nutrients released by nitrogen-fixing bacteria & decomposition of detritus –nutrients then used by bacteria, algae & plants

29
Q

What is the estuarine food web?

A
  • detritus is at the centre of the food web
  • open water, mangroves and further inland salt marsh= common in victoria
30
Q

Why is connectivity between estuaries important and what are its two types?

A
  1. Lateralconnectivity – between estuaries 2. Longitudinalconnectivity – upstream/downstream within estuary -how one habitat can be a source or a sink for another habitat -connectivity is important (larvae movement)
31
Q

How does white mangrove disperse?

A

• Avicennia marina – seed germinates on tree – drops off, floats about 3 days, then sinks – adrift up to 5 months -while floating a root system starts developing, tides can carry them -they move around the bottom for up to few months, then grow enough to get a grip -can attach to the sediment and get leaves etc.

32
Q

What is the life cycle of a blue crab?

A
  • important commercial species
  • eggs on the underside of the female, females move towards the mouth of the estuary
  • migration, then release the larvae
  • the larvae go trough the mouth into the ocean for a bit
  • when well developed, they position themselves so they get carried bacjk into the estuary(behavioural adaptation to get back into the estuary)
  • tide carries them back
  • evetually mass of adult crabs in the same spot where the females walked from
33
Q

What are anadromous fish?

A

-• anadromous – from sea upstream to spawn in freshwater • e.g. salmon -much of adult life in the North Pacific, then start going up the rivers when ready to spawn, then die -larvae move down and swim in the pacific -then again…

34
Q

What are catadromous fish?

A

• catadromous – from freshwater downstream to sea to spawn • e.g. most eels

35
Q

What are shorebirds?

A

-• 36 international migrant species to Aust • about 2 million individuals annually • mostly using East Asian Australasian Flyway -godwit= 11000 km direct -estuaries= birds stop there and feed and rest before going on on their journey again -• many come to estuarine wetlands – feed on benthic invertebrates

Marine Biology (29 decks)

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