Lecture 17- Marine/Pelagic Food Webs Flashcards
pelagic
the water column environment
benthic
- the sea floor environment
- includes coral reefs and rocky intertidal
plankton
unable to swim horizontally against ocean currents but may move vertically in the water column
nekton
- able to swim against ocean currents
- fish, squids, sea turtles, dolphins, whales
holoplankton
- planktonic organisms that live their entire life in fluid suspension
- copepods, shrimp, arrow worms, some jellyfish
meroplankton
- planktonic organisms that spend only part of their life in fluid suspension
- crabs, barnacles, oysters, fish larvae
autotrophs
- group of organisms whose energy/carbon come from nonorganic sources
- ex. phytoplankton because they use sunlight and CO2 for their energy and carbon needs
heterotrophs
- group of organisms whose energy/carbon for growth comes from previously formed organic carbon material
- Ex. Herbivorous zooplankton are heterotrophs because they consume phytoplankton for their energy/carbon needs
- Carnivores are also heterotrophs
trophic level
nutritional feeding level within a food chain or web
first trophic level
primary producers (phytoplankton)
top trophic level
fourth consumers
primary consumer
herbivore
secondary consumer
first carnivore
first question to assign organism to particular trophic level
autotrophic or heterotrophic?
if organism is an autotroph
it contains chlorophyll
second question to assign organism to particular trophic level
if the organism is heterotrophic, is it primary, secondary, etc. consumer?
optimal prey size
- set by consumer’s mouth size
- usually 1/10 the size
marine food webs are said to be
strongly size structured
overall trophic transfer efficiency are affected by
- exploitation efficiency
- gross production efficiency
- trophic transfer efficiency
exploitation efficiency
efficiency with which a consumer population is able to find, capture, and ingest all of the potential prey present in the environment
gross production efficiency
the physiological/biochemical efficiency of converting ingested prey into consumer biomass
trophic transfer efficiency
exploitation efficiency X gross production efficiency
strategies for finding prey
- locomotion
- perception
locomotion
- cruising: rely on your own locomotion to encounter prey
- ambush: rely on the locomotion of your prey to come to you
perception
- visual perception
- mechanosensory
- chemisensory
strategies for capturing prey
- raptorial
- direct interception
- filtering
- entanglement
raptorial
grasp prey with appendages
filtering
sieve large volumes of water
strategies to avoid/escape predation
- avoid encounter or detection
- frustrate the capture process
- bioluminescence
frustrate the capture process
- very small or large size
- spines: mechanical defense
- escape response
- schooling
diel vertical migration
- much of the zooplankton community migrates up to the surface layer of the ocean at night to feed in the dark
- during the day, they migrate down to the safety of the darkness
spring blooms in the temperate North Atlantic region
- during the long winter periods, large grazers sink into the ocean and enter diapause (hibernation)
- in spring, phytoplankton grow to high density
- low exploitation efficiency because grazers aren’t there to eat the phytoplankton
tropical environment
- small grazers remain active throughout they year and consume phytoplankton as fast as it is made
- exploitation energy is very high: almost all phytoplankton is consumed by grazers
gross growth (production) efficiency
amount of consumer biomass produced divided by amount of prey ingestion
gross growth (production) efficiency range
between 20 and 60%
overall trophic transfer efficiency
about 10-20% but we will use 10%
coastal upwelling regions
number of trophic levels between phytoplankton and harvestable fish is smaller in high nutrient regions
open oceans
7 trophic levels
continental shelf
4 trophic levels
upwelling regions
3 trophic levels
highest production of harvestable fish is in the
coastal ocean region
upper limit on the total biomass of harvestable fish in a given ocean province is determined by
- intensity of primary production- number of trophic levels between primary producers and harvestable fish and the trophic transfer efficiencies
