Friday, September 30, 2016

Ocean Heat Wave Kills Kelp Forests Off West Australian Coast

Ocean Heat Wave Kills Kelp Forests Off West Australian Coast

National Oceanic and Atmospheric Administration

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Large stretches of kelp forests off the western coast of Australia were destroyed by a marine heat wave between 2010 and 2013, according to a study published in July in the journal Science. Apparently, kelp forests are now transformed into tropical and subtropical marine ecosystems that turf algae, corals and coral fish currently inhabit.

The kelp forests, which used to contain a variety of seaweed species, have not undergone such a drastic change previously. Now, the seaweed turfs and fish prevent the kelp forests from coming back. Overall, the heat wave wiped out 963 square kilometers of kelp forests in just a short period of time.

To assess how the increase in ocean temperature affected the ecosystems in the region, the research team led by the University of Western Australia’s  Oceans Institute and School of Plant Biology conducted observations of seaweeds, fish, kelp forests, mobile invertebrates and corals in 65 reefs between 2001 and 2015.

Kelp forests
Kelp forest. Credit: Ed Bierman/Wiimedia

Kelp forests used to cover higher than 70 percent of shallow rocky reefs in midwest Australia before the devastating heat wave in December 2010. However, the survey data reveal that a total of 43 percent of these forests disappeared two years after the extreme heat wave.

The researchers concluded that the temperatures have been increasing and affecting the kelp forests along the midwest of the Australia’s coast since the 1970s. The area that suffered the most is the northern region at 29° south of the country, where kelp forest populations have decreased by more than 90 percent.

The UWA team laments that there are no signs of kelp forest recovery. On the other hand, the marine life that replaced the kelps is thriving.

They observed a dramatic increase in seaweed turf populations. They also saw that the population of grazing fishes and other organisms commonly found in coral reefs increased by up to 400 percent. The new ecosystem now resembles the ecosystem normally found in subtropical and tropical waters.