Overgrazing by warm water fish contributes to destruction of underwater kelp forests
|Rabbitfish frenzied feeding on transplanted kelp. Photo courtesy of Adriana Vergés.|
Increasingly voracious Seaweed-eating fish are responsible for the recent destruction of kelp forests off the NSW north coast near Coffs Harbour, a study involving University of Queensland researchers shows.
The study includes an analysis of underwater video covering a 10 year period between 2002 and
2012 during which time the water warmed by 0.6 degrees and there was a significant increase in the appetites of herbivorous fish.
Watch some of the research videos of rabbitfish and surgeonfish feeding on kelp.
Dr Christopher Doropoulos of CSIRO Oceans and Atmosphere, who is affiliated with the UQ School of Biological Sciences said: “Our study is an important break-through because it shows how the indirect effects of climate change have led to the loss of habitat forming kelp forests at the Solitary Island Marine Park in NSW.
“Using a 10 year video data-set, combined with on-siteexperiments and simulation modelling, we show how rising sea-water temperatures increases the abundances of voracious tropical and subtropical herbivorous fish,” he said.
“These fish have munched down the kelp and prevented recolonisation in an extremely short period of time.”
Study first author Dr Adriana Vergés of UNSW and the Sydney Institute of Marine
Science said kelp forests provided vital habitat for hundreds of marine species, including fish, lobster and abalone.
In Australia, kelp forests support a range of commercial fisheries, tourism ventures, and recreation
activities worth more than $10 billion per year.
“As a result of climate change, warm-water fish species are shifting their range and invading
temperate areas,” she said.
“Our results show that over-grazing by these fish can have a profound impact, leading to kelp deforestation and barren reefs.”
Dr Vergés said this was the first study demonstrating that the effects of warming in kelp forests were two-fold: higher temperatures not only had a direct impact on seaweeds, they also had an indirect impact by increasing the appetite of fish consumers, which could devour these seaweeds to the point of completely denuding the ocean floor.
Co-author Dr Yves-Marie Bozec of the Marine Spatial Ecology Lab and ARC Centre of Excellence for Coral Reef Studies at UQ’s School of Biological Sciences said the study also demonstrated the importance of combining observations with models for testing mechanisms that could explain what scientists observed in the field.
The study is published in the journal Proceedings of the National Academy of Sciences.
The team behind this study also included researchers from UNSW, the Sydney Institute of Marine Science, the University of Sydney, the NSW Department of Primary Industries, James Cook University, Centre for Advanced Studies of Blanes Spain, and Nanyang Technological University in Singapore.