Tropical fish threaten kelp and algae

From ABC News in Science, 9 July 2014:

Plant-eating tropical fish species are causing serious damage to algae and kelp forests in sub-tropical and temperate regions around the world, an international team of experts warn.

The findings come from a review published today in the Proceedings of the Royal Society B, which suggests that climate change is leading to ‘tropicalisation’ – the movement of tropical species towards the poles – as waters get warmer and ocean currents strengthen.

It reveals how algae and kelp-eating tropical fish such as rabbitfish have already led to the collapse of kelp forests – and their associated abalone fisheries – in Japan, and decimated the canopy-forming algae forests in the Mediterranean.

Two herbivorous tropical species – rabbitfish and drummer fish – have also been implicated in the loss of kelp forests on both the east and west coasts of Australia, says lead author of the study Dr Adriana Verges, marine ecologist at the University of New South Wales.

Overgrazing of algae and kelp by fish hampers recovery of the ecosystem from events such as heatwaves.

‘The west coast of Australia had a really bad heat wave that wiped out the kelp, and then because it was warmer, a whole lot of other species came in that prevented the kelp from coming back,’ says Verges.

Verges likens the loss of algae and kelp forests to the clear-felling of terrestrial forests.

‘Once the algae forests disappear, everything that goes with them goes, so we lose fish, we lose biodiversity, and we lose biomass,’ she says. Read more.

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