Marine ecosystems 2 (food webs)

Question 1

Why are polar food webs simpler than boresal food webs?

Answer 1

b/c there are fewer species and less productivity

Question 2

Arctic marine food webs are characterized by a __ food chain, high ___ content in the diets, and an apex predator of ___ ___

Answer 2

short
fat
polar bears

Question 3

In arctic marine ecosystems, what is the main keystone species that’s connected to everyone else?

Answer 3

polar cod

• & they rely on ice! no ice= change in entire ecosystem

Question 4

Phytoplankton are small ___ and zooplankton are ___.

They ____ with the currents and form the ___ of the marine food chain

Answer 4

plants
animals
drift
bottom

Question 5

What are the 2 main primary producers in arctic waters?

Answer 5

plankton- diatoms and flagellates

Question 6

diatoms are phytoplankton that produce a ___ (__) covering

Answer 6

glass
silicate

Question 7

Why is chlorophyll so abundant in polar waters?

Answer 7

• lots of stored nutrients (not utilized in winter)
• lots of sunlight in summer= they can grow quickly

Question 8

given ongoing changes in the arctic ocean, how has primary production changed in recent years?
- was this expected?
- where has the largest change been?

Answer 8

it’s gone up! related to increase in open water season

• not expected due to presumed limited nutrients
• largest increases have been on the continental shelves

Question 9

What drives primary productivity in the arctic ocean? Why?

Answer 9

sea ice melt and breakup during the spring
- b/c melt results in enhanced light avail and increased stratification and stabilization of the water column

Question 10

t/f
phytoplankton blooms can occur beneath a ~1m thick sea ice pack, over 100km from the melt edge

why/ why not?

Answer 10

true!

maybe related to altered nutrient cycling or reduced snow cover on sea ice

Question 11

____ can periodically limit diatom growth in the summer and fall

Answer 11

nitrogen

Question 12

Copepods are known as the “___ of the sea” and may be the most numerous ____ animals on earth

Answer 12

insects
multicellular

Question 13

the major consumer of marine primary production is

Answer 13

the copepods of the genus Calanus spp

Question 14

Where do copepods spend their winter? Spring?

Answer 14

copepods overwinter at great depths (below 1000m)
Spring= they reproduce and then they all come up to surface
- spring feed allows them to accumulate a lipid-rich sac used to overwinter

Question 15

What’s the largest species of copepod? Why is it a critical link in the arctic food web?

Answer 15

Calanus hyperboreus

b/c it eats phytoplankton/ small zooplankton in the spring
- it’s endemic to arctic waters (only lives there)

Question 16

Amphipods are _____ that eat phytoplankton, and there are over 150 species of them in the arctic

Answer 16

crustaceans

Question 17

t/f

there are no cnidaria in the arctic ocean b/c they can’t survive in the cold waters

Answer 17

false

• over 100 cnidarian species occur in the arctic (comb jellies, deep water medusa, arctic tube anemone, etc)

Question 18

sea ice is a complex enviro with numerous ___environments

Answer 18

microenviros

Question 19

Explain what brine channels are

Answer 19

when sea ice forms, small spaces b/w the ice crystals remain and are filled w/ brine (salty solution)
- brine channels in the sea ice form a 3D network of tubes (up to a few cm wide)
- specialized organisms live in this matrix!

Question 20

What is a sympagic community?

Answer 20

a community of organisms that lives in ice, for example within the brine channels in sea ice

Question 21

benthic fauna includes lots of ____ and ____

Answer 21

echinoderms and anemones

Question 22

macrobenthic assemblages is best explained by ___ and bottom ___

Answer 22

salinity
bottom temp

Question 23

___ ___ are a major link b/w lower trophic levels (invertebrates) and upper trophic levels (birds, mammals)

Answer 23

arctic cod

Question 24

___ are another important fish, but they’re more associated with sub-arctic than arctic waters

Answer 24

capelin

Question 25

borealization=
give ex

Answer 25

the shift from an arctic species in an area to a more temperate one

ex shift from arctic cod to capelin in an area

Question 26

Pinnipeds in the north include:
(3)

Answer 26

• otariidae (sea lions)
• Odobenidae (walrus)
• Phocidae (seals)

Question 27

walrus eat mostly ___

Answer 27

clams (3000-6000 of them in a single feeding!)

Question 28

t/f
pregnant polar bears can fast for up to a year

Answer 28

false

they can fast up to 8 months

Question 29

What are the 3 main species of arctic whales?

Answer 29

• bowhead whale
• narwhal
• belgula (white whale)

Question 30

List the 3 key adaptations that arctic whales have

Answer 30

1. migrate to ice margins in the winter
2. remain in sea ice to avoid killer whale predation
3. lack dorsal fin (adaptation to break ice)

Question 31

t/f
bowhead whales declined a lot in late 1800s due to commercial whaling but the population is now recovering

Answer 31

true

Question 32

changes in __-___ extent are causing shifts from traditional sympagic-pelagic-benthic web

Answer 32

sea-ice

Question 33

greater area and time of open water is shifting phytoplankton blooms to __ waters, making them occur ___(earlier/ later) and reduces sympagic-benthic connection

Answer 33

deeper
earlier

Question 34

Which trophic level is seeing the most changes/ having the hardest time with recent sea ice and climate changes ?

Answer 34

top predators