Australian scientists said Friday there was now "striking evidence" of extensive southward migration of tropical fish and declines in other species due to climate change, in a major ocean report card.
Compiled by more than 80 of Australia's leading marine experts for the government science body CSIRO, the snapshot of global warming's effects on the island continent's oceans warned of "significant impacts".
"Climate change is already happening; widespread physical changes include rapid warming of the southeast and increasing flow of the east Australia current," the report said.
"There is now striking evidence of extensive southward movements of tropical fish and plankton species in southeast Australia, declines in abundance of temperate species, and the first signs of the effect of ocean acidification on marine species with shells."
The report described southeast Australia as a "global warming hotspot", with the contraction south and strengthening of southern hemisphere winds causing the eastern current to become more intense and also warmer.
"A range of species including plankton, fish and invertebrates are now found further south because of the enhanced transport of larvae and juveniles in the stronger (current) and the high rate of regional warming," it said.
Sea snakes were declining and warmer beaches were changing turtle breeding habits and seabird and marine mammal feeding and mating, it added.
Coral reefs had experienced increasing thermal bleaching in the past 30 years and that was projected to become more frequent and severe, "leading to chronic degradation of most coral reefs by the middle to late parts of the century."
Though there were some "concerning findings", project leader Elvira Poloczanska said there were some positives, with new research suggesting that certain tropical fish species were better equipped to adapt to warming than previously thought.
"Whether such acclimation capacity is widespread in tropical marine fishes and whether some critical processes (such as) reproduction remain significantly impaired is unknown."
Poloczanska said Australia had some unique marine ecosystems and they provided "irreplaceable services including coastal defence, oxygen production, nutrient recycling and climate regulation".
"Every second breath of oxygen we breathe is provided by marine plants; they provide protein when we eat fish and also relaxation such as when we go swimming," she said.
"It's important we make decisions about the future."