Lecture 23- Life in estuaries Flashcards Preview

Marine Biology > Lecture 23- Life in estuaries > Flashcards

Flashcards in Lecture 23- Life in estuaries Deck (35):
1

What is an estuary?

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

2

What is a delta?

- composed of river- derived sediments

3

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

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

4

Does salinity differ a lot in estuaries?

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

5

What are stenohaline marine species?

-tolerate narrow range of salinities

6

What are euryhaline marine species?

-tolerate side range of salinities -most common in estuaries

7

What are brackish water species?

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

8

What are freshwater species?

-low salinity tolerance

9

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

-

A image thumb
10

What is an osmoregulator?

-regulates internal ion concentrations

11

What is an osmoconformer?

-internal ion concentrations change with ambient salinity

12

Can a species be both an osmoconformer and an osmoregulator?

-yes -eg. crab: bit of each, at low salinities= conforming,

-in inbetween salinities= regulating,

-when salinity high= conforming

-strategy varies with the outside conditions

A image thumb
13

What is an example of a perfect osmoconformer?

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

A image thumb
14

What are two examples of perfect osmoregulators?

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

A image thumb
15

What are characteristics of mangroves?

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

16

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

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

How do marine fish cope with salt water?

-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

A image thumb
18

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

-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

What are the temperature conditions in estuaries?

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

20

How does Northern Pacific seastar deal with temperature and salinity?

-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

What are the sediments in estuaries like?

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

22

Does sand have different grain sizes?

-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

What is space between grains important for?

-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

A image thumb
24

What is bioturbation?

-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

What are ghost shrimps important for?

-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

What are anoxic sediments?

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

27

What do suspended sediments do?

• 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

What is the productivity and nutrient level in estuaries?

• 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

What is the estuarine food web?

-detritus is at the centre of the food web

-open water, mangroves and further inland salt marsh= common in victoria

A image thumb
30

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

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

How does white mangrove disperse?

• 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

What is the life cycle of a blue crab?

-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

A image thumb
33

What are anadromous fish?

-• 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

What are catadromous fish?

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

35

What are shorebirds?

-• 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