An underwater kelp forest more that 60 miles long off the coast of western Australia has been seriously damaged by a massive marine heatwave in 2011, according to The Conversation.

Researchers noted higher water temperatures, as much as two degrees Centigrade above normal, lasted for about 10 weeks, ravaging the waters in the area.  And five years after the heatwave, the damage shows no signs of recovery.

The loss of the kelp is also causing severe harm to the delicate marine ecosystem off the coastline in the region, said the scientists.  Damage from the heatwave reaches as much as 620 miles in length, but an area of about 150 square miles felt the greatest impact.  Further South of that location, an additional 370 square miles of kelp may have also been lost the the warmer ocean waters.

Researchers monitoring kelp fields, looking to determine the changes in marine populations over time, estimate 43 percent of the kelp forests have been lost.  The kelp is being replaced by other tropical species.

The result is that now tropical fish species, that are replacing the fish, seaweed and invertebrate communities, are now intensely feeding along the reef, and preventing the kelp forests from recovering.

The damage has great implications for the Great Southern Reef (GSR), which is home for about 70 percent of all Australians, and a collection of temperate marine species.  The area supports some of the most valuable fisheries on the continent, and also a tourism industry estimated at around A$10 billion each year.

Part of the issue is the southward-flowing Leeuwin Current, which provides assistance to tropical species moving towards the south, and at the same time, making it more difficult for the temperate species to recolonize affected areas to the north.

This combination of ecological and physical processes, coupled with a warming rate of twice the global average, just adds to the difficulties faced by the struggling kelp forests.

The team’s research was reported in the journal Science.