Lecture 16 competition on coral reefs

What is competition?

Interaction between individuals brought about by a shared requirement for resources in limited supply, and leading to reduction in the survivorship, growth, and/or reproduction of the competing individual concerned

Interference Competition

Directly Between individuals

when one organism physically restricts another organism’s access to resources

Exploitative and Apparent Competition

indirectly between individuals

Exploitative: when an organism is competing for resources

Apparent: when you have a prey that is influencing the predator with a parasite or a pathogen

What resources do organisms in tropical coral reefs compete for?

Competition for space

Competition among benthic invertebrates

Competition for space

Overgrowth: Intraspecific competition and Interspecific competition

Overtopping: grow tall and grow out

Mesenterial filaments: separation between the corals

Sweeper tentacles: aggressive strategy on pushing organisms away

Mucus Secretions: like darts

Allelopathy: Chemicals mechanisms of interference competition on coral reef

Locomotion away: some are able to break a piece away and move away and regenerate

Is competition costly? Effects on fitness

However, it depends because sometimes there is a negative

Many mechanisms of coral competition require low energy investment and thus may not alter rates of growth in dominant corals

• But effects on subordinate vs. dominant coral species is different

Competition in a changing environment

Increased anthropogenic activity, particularly he eutrophication, occurring along the Israeli coasts, creates favorable conditions for filter-feeding organisms such as ascidians, providing them with an advantage in competition for space over reef-building corals and other organisms

What resources do organisms in tropical coral reefs compete for? (Pelgaic)

Competition for space

Fish compete for limiting resources

Territories → nest sites mating sites

Hiding places → competition for predator free space

Food → but little evidence that it is limiting

What is Intraspecific competition?

Distribution and use of resources

Survival: the most commonly implicated resource in competition-induced, density-dependent survival is shelter space from predators

Growth and reproduction fitness: Low growth → delayed maturations

What is interspecific competition?

As with intraspecific competition, survival is the most common demographic response variable measured to assess interspecific competition among reef fishes