Chapter 5: Etuaries

Question 1

what are the four size gradients of tides?

Answer 1

Microtidal 6m

Question 2

what are the five zones of the estuary, and their salinity?

Answer 2

1: Head,

Question 3

what are the four environmental variables of estuaries?

Answer 3

salinity
sediment
DO
temp

Question 4

why do estuaries typically have low DO concentration?

Answer 4

due to anaerobic bacteria in the mud.

–> breaks down OM, can result in methane or hydrogen sulphide

Question 5

what is the importance of temperature in estuaries?

Answer 5

• can be a trigger for reproduction or migration
• can be more important than salinity
• influence the speed of bacteria breakdown

Question 6

what are the 3 scenarios for colonization of estuaries after glacial retreat?

Answer 6

• 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

Question 7

Estuarine organisms originated from which two possible sources?

Answer 7

• FW origin extending into estuaries from rivers

- Marine sp. colonizing estuaries from the sea

Question 8

why must a species be resilient to live in estuary environmets?

Answer 8

environements are dynamic, stressful, and produce strong evolutionary selection forces.

Question 9

what are the three most abundant FW groups to colonize estuaries?

Answer 9

• Oligochaetes most successful
• Fish
• Pulmonate molluscs

Question 10

what are the prevalent species groups of the mudflats?

Answer 10

• polychaetes
• oligochates
• small crustaceans (amphipods)
• benthic diatoms

Question 11

hyperosmotic

Answer 11

uptake of water by organism which has an internal fluid concentration greater than surrounding water

Question 12

osmoconformer

Answer 12

• little if any ability to osmoregulate

- high tolerance to diluted blood concentrations

Question 13

which species group are the most efficient osmoregulators?

Answer 13

Crustaceans

Question 14

Organisms found in the most variable conditions within an estuary are not necessarily the most sophisticated osmoregulators, but simply the most ________.

Answer 14

tolerant

Question 15

______ enables organisms to adapt to various salinities even with limited osmoregulatory capabilites

Answer 15

Physiological plasticity

Question 16

what are impacts of increased FW inflow?

Answer 16

-large decrease in salinity
-can boost estuarine productivity
ORGANISMS CAN:
-tolerate changes
-migrate/drift
-die

Question 17

what are impacts of reduction of FW flow?

Answer 17

-upsteam movement of spp
-increase in salinity upstream can have dramatic effects
-productivity of estuary affected
(meiofauna, phytoplankton)

Question 18

name factors influencing fish communities in estuarine habitats

Answer 18

• water temp main one
• DO
• habitat complexity
• variations in climate

Question 19

low plant biomass and 1* productivity. EXCEPTIONS:

Answer 19

seagrass beds

systems at outer estuaries (mangroves, saltmarshes)

Question 20

production is dominated by what?

Answer 20

detritus.

due to organic carbon in sediment of mudflats

Question 21

where does the detritus come from?

Answer 21

marine (algae by tide)
semi terrestrial (saltmarshes)
terrestrial (leaf litter etc)

Question 22

why is the huge number of detritivores important to the food web?

Answer 22

supports fish and birds, influences trophic interactions

Question 23

how do estuaries influence birds?

Answer 23

key feeding areas, especially for migrating spp.

Question 24

how do birds influence estuaries?

Answer 24

• major bioturbators
• some cases re-work top sediment 8 times in 3 months
• eat roots as well as leaves

Question 25

foraging birds: | what does it mean, 'ideal free distribution'

Answer 25

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.

Question 26

General description of saltmarshes

Answer 26

- mostly exposed to air - submerged @ high tide - areas vegetated by herbs, grasses or low shrubs - top end of mudflats - plants play an important role

Question 27

what are the function of the saltmarsh?

Answer 27

- reproduction area - refuge (environmental stress, predation) - foraging area

Question 28

how do tropic estuaries compare to temperate?

Answer 28

temperate: newer due to glaciation, less effective evolutionary time. tropic: older and more diversification. hypersaline due to intense evaporation.

Question 29

what is the spp diversity like in estuaries compared to other regions?

Answer 29

less diversity, as less species are able to survive harsh conditions.

Question 30

hyposaline seas

Question 31

Baltic Sea (quick overview)

Answer 31

- 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

Question 32

Hyper saline waters

Answer 32

- coastal - salinity >34 - evaporation rate > inflow of FW - decrease diversity with increase salinity from 34

Question 33

what is an example of a hypersaline water, and some features.

Answer 33

Crimea peninsula - long, thin, isolated by land barrier - limited water exchange - minimal tides - organisms originate from sea

Question 34

Lagoons

Answer 34

-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.

Question 35

when were most estuaries formed? 6

Answer 35

6-10000 years ago (last ice age)

Question 36

where can most of the best osmoregulators be found?

Answer 36

in the mud