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Sci Tech
Marine biodiversity for preserving species
A NEW study of marine ecosystems suggests that the preservation of biodiversity is more than just a lofty goal — it's an absolute necessity to keep the system healthy and prevent both local and regional extinction of multiple species.
The population balance between various fish species, their competitors and their predators are all essential to the proper functioning of the ecosystem, the study showed, and over fishing of any one species can have ripple effects that destabilize the whole fishery.
The study was conducted by marine zoologists at Oregon State University and published in the Proceedings of the National Academy of Sciences. It was done on coral reefs in the Bahamas, which allowed the type of experimental manipulations that are usually impossible to do in a marine ecosystem.
The research showed that all fish species within a food web are connected with one another., and the removal of any one species can cause whole populations to break down. This is true when you take away the predatory species, which are a key to natural health of marine ecosystems...
In particular, this study confirmed the operation in a marine ecosystem of a concept that has long been recognized with animals in terrestrial ecosystems — that of `density dependent mortality.' Basically, when a species population size is low, the mortality rate will also be low. Predators tend to target species that are more abundant.
And when a species population is high, the mortality rate will increase, as predators take advantage of the easy availability of food. Other than the interaction between prey and predator, there is also an important role for competitors — two or more species that fight for the same resources. The competing species have negative effects on each other's population, and distracted competitors can be more vulnerable to predation.
With experimental manipulations on coral reefs in clear waters of Bahamas, OSU scientists were able to isolate some reefs from others and selectively remove certain fish, their competitors or predators.
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