Small animals with big impact – the world’s most common animal release unique substances into the oceans

Copepods, the world’s most common animal, release unique substances into the oceans. Concentrations of these substances are high enough to affect the marine food web, according to new research from the University of Gothenburg. The studies also show that phytoplankton in the oceans detect the special scent of copepods and do their utmost to avoid being eaten.

The substances that copepods release into seawater are called copepodamides. When phytoplankton in the water sense copepodamides, they activate their defence mechanisms to avoid being eaten. Some phytoplankton then produce light, bioluminescence; other plankton use chemical warfare and produce toxins or shrink in size.

“Since the phytoplankton in the ocean are the basis of all marine life, the effects become large-scale,” says Erik Selander at the Department of Marine Sciences at the University of Gothenburg, who heads the research team.

CREDIT: Erik Selander

Selander compares the effect of copepodamides with the effect of hormones in the body.

“The substances are remarkably potent. Very small quantities produce large systemic effects. The amount of copepodamide that would fit in a grain of salt are enough to cause phytoplankton in a whole swimming pool to mobilise their defences. Some of the defences involve very strong toxins, and as a result copepodamides can have far-reaching effects such as toxic algal blooms.”

The article, which has now been published in Science Advances, also shows that copepodamides affect more of the ocean’s inhabitants than researchers previously recognised. The new discoveries increase our understanding of the marine food web, and especially the mechanisms that lead to toxic algal blooms.

Research article: Copepods drive large-scale trait-mediated effects in marine plankton

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