(Image: Catheline Froelich)

Changes to the Great Barrier Reef environment are beginning to have an impact in southern waters, according to experts.

Dr Marian Wong from the University of Wollongong’s Centre for Sustainable Ecosystems Solutions said increases in appearances of tropical species in the south is concerning.

“Many juvenile tropical fish from the north are being ‘washed down south’ by the East Australian Current, and some of those are surviving over winter because of the warmer temperatures in the south,” she said.

She said the presence of these tropical species further south will impact species living in southern reefs and could have unknown consequences.

Dr Wong recently returned from her latest visit to the Australian Museum’s Research Station on Lizard Island in the far northern sector of the Great Barrier Reef.

Dr Wong was part of a team of researchers from UOW, Southern Cross University and the University of Technology Sydney that observed the behavioural patterns of fish and the effects of coral bleaching to tropical fish species.

The researchers found much of the sea coral surrounding Lizard Island has transformed from a once spectical of colour to a dull brown.

The impacts of rising sea temperatures and weather phenomenons, such as the tropical cyclones that have hit Northern Queensland, contribute to coral bleaching and have devastating effects on coral-reef fish.

The populations of coral-dwelling fish have been significantly recued to the point of local extinction.

Dr Wong said is particularly concerned with the decline of the coral-gobie.

“There were very few if any live branching corals and their associated coral-gobies in the exact same areas where we surveyed in 2014, before bleaching and cyclones happened, we found lots,” she said.

Not all fish are struggling. Fish that are reliant on coral networks for food, shelter or breeding sites such as the coral-gobies and the famous Clown fish, many know as Nemo, are feeling the most impact.

“Think about a bushfire, destroying people’s homes leaving many homeless,” Dr Wong said.

Dr Wong said there is still time for coral reefs to recover and for fish populations to return.

“Fish populations can recover provided corals come back and are given sufficient time without another bleaching event to grow,” she said.

Image: Catheline Froelich