Predator and prey interactions

example of rocky shore food chain

wrack → mollusc → crab → fish

top-down food chain

predator-mediated control

rocky shore top-down food chain

predatory starfish controlling mussel population and facilitating algal growth

keystone predator

very important predator, e.g. starfish

bottom up food chains

resource limited

antarctic bottom up food chain

krill (resource) very important for rest of food chain

diel vertical migration (DVM)

daily migration of zooplankton between surface and deep waters

types of DVM

nocturnal migration, twilight migration, reverse migraion

nocturnal migration

most common, ascend at sunset and descend at sunrise

twilight migration

2 ascents/descents. up at sunset, down at midnight, up at sunrise, down at day

reverse migration

least common, ascend at sunrise and descend at night

pycnocline

area where density increases rapidly with depth 

proximate cause of DVM

changes in light intensity (want to avoid light)

ultimate cause of DVM

predator evasion. reduce risk from visual predators (kremer & kremer 1988)

ecological significance of DVM

transport food from surface to deep, removal of C & N from surface