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Ginzburg-Getz-Ardith trophic level biomass vs environmental productivity

all increasing
ratio dependent
highly contradicted system, level can't increase at a ratio dependent manner, would self restrict


Persson trophic level biomass vs environmental productivity

looks the same as F-O only 2 trophic levels exist. one is increasing while the other is constant


length of food chain

affects accumulation process and efficiency


each food web interaction (energy transfer)

- 10-15% of E
shorter food chain = more efficient


Menge and Sutherland, views on top down regulation in food webs

physical disturbance shortens food chains, most organisms will shift diet depending on food availability


Hairston, Smith, Slobodkin , views on top down regulation in food webs

predator/prey interaction bring in self regulatory processes. predators regulate herbivores, releasing plants to become resource limited


Freewill and Oksanen, views on top down regulation in food webs

top trophic levels and even numbered steps below are resource limited, trophic levels odd numbered steps below are predator limited


McQueen, views on predator and resource co-limitation in food webs

top-down diminishes efficiency at bottom of food chain, but both affect each other


Getz, views on top down regulation in food webs

inference hypothesis- predators interfere with each other- prevent efficient exploitation of resources, prey can increase


Mittelbach, views on top down regulation in food webs

predators require different resources as they grow (ontogenetic shift)


Lei bold, views on top down regulation in food webs

control of prey by consumer is not always consistent (shifts to less edible species)


Sinclair and Norton, views on top down regulation in food webs

starvation-weakened prey become more vulnerable to predation or disease


predator negative feedback, self regulation

interference competition
exploitative competition
depletion of nutritious, palatable, accessible prey


algal biomass vs. potential productivity, even link system (hypothetical)

2-link (algae, zooplankton), increased productivity will not increase algal biomass


algal biomass vs. potential productivity, odd links system (hypothetical)

potential productivity can increase, 3rd link consumes 2nd link and allows 1st link to grow


TP, indicator of



fishing down top of foodweb

shifting average trophic level (down)
significant decline in average trophic level of fish catch, average size of fish becoming smaller
crowding down foodweb?


how to define trophic level

analyze gut content


as average catch increases

average trophic level decreases, Pauley et al., 1998


cascading effects of the loss of apex predatory sharks from a coastal ocean

11 species of shark- all declining from overfishing
different species of mesopredators - all increasing
termination of scallop fishery


effects of fish in river food webs

one of first experiments on river ecosystem to demonstrate cascading effect of predators on lower trophic levels are consistent w/ observations from other ecosystem (remove large fish, small fish dominant, algal biomass increased, odd/even # trophic level limitations)


major change in food web concept theories

foodwebs are not closed systems. local interaction in one ecosystem may reverberate into another.
ex. aquatic system affecting terrestrial


aquatic system affecting terrestrial example

fish eating larval dragonfly-- decrease dragonfly abundance -- increase honeybee abundance -- increase pollination
no fish-- pollination significantly decreased


shrimp stocking theory

add more food, they will produce more


shrimp stocking results

reduced number of spawner, reduces numbers of bears and eagles


what happened with the shrimp stocking?

the introduced shrimp (Mysis) come up in water column at nigh and prey on the kokanee/trouts food but stay at the bottom of the lake during the day- reducing fish prey


Lake Victoria changes

introduced Nile Perch (1954) to increase European sport fishing; HAD extremely high diversity before; major shift to invasive species, basically replaced natives, loss of diversity and food web interactions


stability and diversity

higher diversity = higher stability



zooplanktivorous cichlid, significantly decreased since introduction of nile perch


one positive side to nile perch introduction

more protein for Kenyan people