The Trophic Structure of Hawaiian Reefs Part 1

Food Chains Artificial devices to illustrate energy flow from one trophic level to another Trophic Levels: groups of organisms that obtain their energy in a similar manner

Total number of levels in a food chain depends upon locality and number of species Highest trophic levels occupied by adult animals with no predators of their own Secondary Production: total amount of biomass produced in all higher trophic levels Food Chains

Nutrients Inorganic nutrients incorporated into cells during photosynthesis - e.g. N, P, C, S Cyclic flow in food chains Decomposers release inorganic forms that become available to autotrophs again

Energy Non-cyclic, unidirectional flow Losses at each transfer from one trophic level to another -Losses as heat from respiration -Inefficiencies in processing Total energy declines from one transfer to another -Limits number of trophic levels

Energy Flow

ProducerPrimary Consumer Secondary Consumer Tertiary Consumer Food Chain Nutrients Decomposer grass grasshopper snake hawk fungi Energy Flow through an Ecosystem heat

Transfer Efficiencies Efficiency of energy transfer called transfer efficiency Units are energy or biomass E t = P t P t-1 P t = annual production at level t P t-1 = annual production at t-1

Transfer Efficiency Example Net primary production = 150 g C/m 2 /yr Herbivorous copepod production = 25 g C/m 2 /yr Typical transfer efficiency ranges *Level 1-2 ~20% *Levels 2-3, …: ~10% E t = P t P t-1 = P copepods P phytoplankton = 25 =

Energy and Biomass Pyramids Kaneohe Bay 1,000,000 J of sunlight Primary producers Tertiary consumers Secondary consumers Primary consumers 10,000 J Limu 1000 J 100 J 10 J

Feces Growth Cellular Respiration Algae eaten by Uhu

Food Webs Food chains don’t exist in real ecosystems Almost all organisms are eaten by more than one predator Food webs reflect these multiple and shifting interactions

Antarctic Food Web

Some Feeding Types Algal Grazers and Browsers Suspension Feeding Filter Feeding Deposit Feeding Benthic Animal Predators Plankton Pickers Corallivores Piscivores Omnivores Detritivores Scavengers Parasites Cannibals Ontogenetic dietary shifts Algal Grazers and Browsers Suspension Feeding Filter Feeding Deposit Feeding Benthic Animal Predators Plankton Pickers Corallivores Piscivores Omnivores Detritivores Scavengers Parasites Cannibals Ontogenetic dietary shifts Many species don’t fit into convenient categories

Food Webs… Competitive relationships in food webs can reduce productivity at top levels Phytoplankton (100 units) Phytoplankton (100 units) Herbivorous Zooplankton (20 units) Carnivorous Zooplankton A (2 units) Fish (0.2 units) Herbivorous Zooplankton (20 units) Carnivorous Zooplankton A (1 units) Fish (0.1 units) Carnivorous Zooplankton B (1 units)

Primary Producers zooxanthellae in corals filamentous algal scum (turf algae) coralline (calcareous) algae non-coralline seaweed filamentous algae growing through the upper layers of the porous reef rock (endolithic algae) benthic and interstitial diatoms phytoplankton zooxanthellae in corals filamentous algal scum (turf algae) coralline (calcareous) algae non-coralline seaweed filamentous algae growing through the upper layers of the porous reef rock (endolithic algae) benthic and interstitial diatoms phytoplankton

zooxanthellae

turf algae

coralline red algae

crustose coralline red algae

benthic seaweeds

benthic diatoms

phytoplankton

Herbivores herbivorous fish –most parrotfish –surgeonfish (e.g., manini, palani, pualu, kala) –Pacific Gregory (Stegastes fasciolatus) –tidepool blennies herbivorous snails and sea hares most sea urchins herbivorous crabs green sea turtles herbivorous fish –most parrotfish –surgeonfish (e.g., manini, palani, pualu, kala) –Pacific Gregory (Stegastes fasciolatus) –tidepool blennies herbivorous snails and sea hares most sea urchins herbivorous crabs green sea turtles

parrotfish

surgeonfishes

Pacific Gregory

tidepool blenny

tiger cowrie

chiton