Herbivory

Herbivory

• Three Types of Herbivorous Fishes
  • Reef fishes that are herbivores are typically invertebrates <ref> Cornell University: College of Agriculture and Life Sciences, "Herbivory in Fish." Last modified 2014. Accessed February 23, 2014. http://micro.cornell.edu/research/epulopiscium/herbivory-fish.
  • Territorial Grazers-site-attached fishes that actively defend their territories against other herbivores
  • Roving Grazers-mobile herbivores move around reefs in large schools feeding on macro algae and epilithic algae
  • Scrapers-highly mobile fish consume epilithic algae and remove sediment by scraping limestone surface of reefs
  • Examples-surgeonfish, butterflyfish, angelfish2

• Feeding Habits of Herbivore Fish/How Food is Digested2
  • Focus on enriched macrophytes
  • Shallower reefs have more herbivorous fishes and increased grazing rates
  • Some prey directly on Corals (parrotfish)3
  • Feed on red, green, and brown macro algae2
  • No teeth in jaws, rather pharyngeal teeth farther back
  • Digestion- must break down complex polysaccharide cell wall
  • Mechanical-stomach grinds the algal cells
  • Chemical-use acid lysis in the stomach
  • Enzymatic digestion-enzymes produced by gastrointestinal tract can further break down algal cells/ intestinal microbes are key

• Benefits of Herbivore Fishes to Stability of Coral Reefs
  • Help maintain coral dominated states
  • Limit growth of macro algae that compete with coral space
  • A decrease in herbivore fish can be linked to increase in macro algae and coral reef mortality (macroalgae and phytoplankton most significant primary producer in system)
  • Facilitate maintenance of reefs in coral dominated states1
  • Strong top down control of macroalgae
  • Elimination of herbivore fish can negatively impact survival, growth, and recruitment of corals and increase in prevalence of coral diseases
  • Alteration in consumer pressure will reduce coral reef resilience and increase probability that climate change, ocean acidification, etc. will drive reefs to state like algal domination

Turf algae and upright macroalgae increase are due to herbivore exclusion3 One of the most well known cases of overgrowth occurred in the Caribbean after a previously unseen disease virtually killed off the herbivorous sea urchin Diadema antillarum2 Caused collapse of Caribbean reefs in this area Macroalgae became dominant Decrease in diversity

References