Marine ecosystems 2 (food webs) Flashcards
Why are polar food webs simpler than boresal food webs?
b/c there are fewer species and less productivity
Arctic marine food webs are characterized by a __ food chain, high ___ content in the diets, and an apex predator of ___ ___
short
fat
polar bears
In arctic marine ecosystems, what is the main keystone species that’s connected to everyone else?
polar cod
- & they rely on ice! no ice= change in entire ecosystem
Phytoplankton are small ___ and zooplankton are ___.
They ____ with the currents and form the ___ of the marine food chain
plants
animals
drift
bottom
What are the 2 main primary producers in arctic waters?
plankton- diatoms and flagellates
diatoms are phytoplankton that produce a ___ (__) covering
glass
silicate
Why is chlorophyll so abundant in polar waters?
- lots of stored nutrients (not utilized in winter)
- lots of sunlight in summer= they can grow quickly
given ongoing changes in the arctic ocean, how has primary production changed in recent years?
- was this expected?
- where has the largest change been?
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
What drives primary productivity in the arctic ocean? Why?
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
t/f
phytoplankton blooms can occur beneath a ~1m thick sea ice pack, over 100km from the melt edge
why/ why not?
true!
maybe related to altered nutrient cycling or reduced snow cover on sea ice
____ can periodically limit diatom growth in the summer and fall
nitrogen
Copepods are known as the “___ of the sea” and may be the most numerous ____ animals on earth
insects
multicellular
the major consumer of marine primary production is
the copepods of the genus Calanus spp
Where do copepods spend their winter? Spring?
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
What’s the largest species of copepod? Why is it a critical link in the arctic food web?
Calanus hyperboreus
b/c it eats phytoplankton/ small zooplankton in the spring
- it’s endemic to arctic waters (only lives there)
Amphipods are _____ that eat phytoplankton, and there are over 150 species of them in the arctic
crustaceans
t/f
there are no cnidaria in the arctic ocean b/c they can’t survive in the cold waters
false
- over 100 cnidarian species occur in the arctic (comb jellies, deep water medusa, arctic tube anemone, etc)
sea ice is a complex enviro with numerous ___environments
microenviros
Explain what brine channels are
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!
What is a sympagic community?
a community of organisms that lives in ice, for example within the brine channels in sea ice
benthic fauna includes lots of ____ and ____
echinoderms and anemones
macrobenthic assemblages is best explained by ___ and bottom ___
salinity
bottom temp
___ ___ are a major link b/w lower trophic levels (invertebrates) and upper trophic levels (birds, mammals)
arctic cod
___ are another important fish, but they’re more associated with sub-arctic than arctic waters
capelin
borealization=
give ex
the shift from an arctic species in an area to a more temperate one
ex shift from arctic cod to capelin in an area
Pinnipeds in the north include:
(3)
- otariidae (sea lions)
- Odobenidae (walrus)
- Phocidae (seals)
walrus eat mostly ___
clams (3000-6000 of them in a single feeding!)
t/f
pregnant polar bears can fast for up to a year
false
they can fast up to 8 months
What are the 3 main species of arctic whales?
- bowhead whale
- narwhal
- belgula (white whale)
List the 3 key adaptations that arctic whales have
- migrate to ice margins in the winter
- remain in sea ice to avoid killer whale predation
- lack dorsal fin (adaptation to break ice)
t/f
bowhead whales declined a lot in late 1800s due to commercial whaling but the population is now recovering
true
changes in __-___ extent are causing shifts from traditional sympagic-pelagic-benthic web
sea-ice
greater area and time of open water is shifting phytoplankton blooms to __ waters, making them occur ___(earlier/ later) and reduces sympagic-benthic connection
deeper
earlier
Which trophic level is seeing the most changes/ having the hardest time with recent sea ice and climate changes ?
top predators
