Tue, 30 May 2023

SYDNEY, March 24 (Xinhua) -- A new research led by the Queensland University of Technology (QUT) has revealed that climate change could have significant effects on the diet quality of small fish, exacerbating the decline in fish biomass by up to 10 percent.

The research, published in the Nature Climate Change journal on Thursday, modeled the impact of climate change on zooplankton.

The microscopic animals account for roughly 40 percent of the world's marine biomass and serve as the primary connection between phytoplankton and fish, including Antarctic krill and jellyfish, which are crucial food sources for many marine species.

The researchers found that climate change would lead to changes in the composition of zooplankton communities across most of the world's oceans, as phytoplankton size decreases under these conditions.

Carnivorous groups, such as chaetognaths and jellyfish, and gelatinous groups, such as salps and larvaceans, will dominate future zooplankton communities, at the expense of small crustacean omnivores, according to the research.

Ryan Heneghan, lead author and QUT lecturer, told Xinhua that energy moves up marine food chains from primary producers to fish by big things eating small.

Salps and larvaceans are large zooplankton that feeds on primarily small phytoplankton and bacteria. They would have an advantage over similarly sized groups like copepods if small phytoplankton becomes more prevalent under climate change, said Heneghan.

"Our model suggests this would buffer marine food chains from becoming very much longer, but it comes at the cost that food available for small fish would become more gelatinous, so the quality of their diet would decline," the expert said.

Heneghan also pointed out that the carbon content in zooplankton serves as a useful proxy for their nutritional quality.

Small fish in the region shifted to more gelatinous diets, low-carbon zooplankton, which could lead to a decline in their weight and abundance, with far-reaching implications on a global scale, he added.

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