Marine ecosystems 2 (food webs)
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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