A new analysis suggests that the movement of plankton and plankton-eating fish plays a central role in driving local peaks of extreme biological productivity in tropical coral reefs, creating ‘sweet spots’ of abundant fish. Renato Morais of James Cook University in Townsville, Australia, and colleagues present these findings in a study published November 2n/a in the open access journal PLOS Biology.
Although some ecosystems are limited by their intrinsic productivity (of photosynthesis, for example), previous research has shown that mobile resources such as plankton can serve as vectors that transfer energy and nutrients from offshore ecosystems to ecosystems in Coral reefs. These transfers of resources between ecosystems are known as spatial grants and allow ecosystems to exceed the limits of their intrinsic capacities for biological productivity, resulting in more abundant life. However, the extent to which the movement of plankton and plankton-eating fish increases abundance in tropical marine ecosystems is unclear.
To help clarify and quantify this role, Morais and his colleagues integrated and analyzed extensive data from visual counts of fish. One data set covered the tropical waters of the Indian Ocean and much of the Pacific, while the other fish count data came from three specific tropical locations that were representative of the diversity of coral reef ecosystems found in the ocean. larger data set.
The analysis revealed that plankton-eating fish do indeed play a major and widespread role as vectors of spatial subsidies to tropical coral reefs. By feeding on offshore plankton, they provide additional resources to reef ecosystems and thus lead to local periods of extreme biological productivity, including for their own predators. In these ‘sweet spots’, plankton-eating fish are responsible for more than 50% of total fish production, and people could find optimal conditions there for abundant fishing.
The researchers note that their findings are of particular importance for the future of tropical reef fishing. Coral reefs continue to degrade and offshore productivity is expected to decline, so ideal areas that concentrate these declining resources could become more important to fishers.
Morais adds, “How do tropical oceans sustain high production and intense coastal fishing despite being in nutrient-poor oceans? Spatial grants transmitted by planktivorous fish greatly increase local reef fish biomass production, creating “sweet spots” of fish aggregation. By harvesting ocean productivity, planktivorous fish circumvent spatial constraints imposed by local primary productivity, creating “oases” of tropical marine biomass production. »
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