Flooding in 2009 and 2010 followed by Cyclone Yasi in 2011 caused significant damage to meadows in Cairns Harbour, with a 98% loss of seagrass coverage leading to an 84% decline in fish abundance and 73% reduction in fish species richness.
TropWATER PhD student Darcy Philpott, who led the study, said this had major flow-on effects for the organisms that call seagrass meadows home.
“The seagrass meadows that are found in Cairns are an extremely important ecosystem. They form a fish nursery habitat, protecting young fish as well as prawns from predation and giving them a safe place to forage,” she said.
The study analysed over 30 years of beam trawl data to show how fish assemblages have changed through the periods of damage and recovery of these seagrass meadows.
The team found that fish abundance and richness had both recovered to pre-disturbance conditions in just over ten years – but the types of fish living in the meadows were different.
“We found that these fish communities are recovering in a different trajectory to what they were pre-disturbance… you’re still getting that recovery and return, but it's coming back different,” said Ms Philpott.
While some species returned to the seagrass meadows after disturbance, others did not. Fish like the Goldsilk Seabream (Acanthropagrus berda) were previously abundant but disappeared after the storm events, while Grunter (Pomadasys argenteus) were less common pre-disturbance and are now abundant.
TropWATER’s Dr Robert Coles, a co-author of the study, was part of the team who began monitoring fish in the seagrass meadows in Cairns Harbour in the 1990s.
“You need these longer-term datasets – which are rare – in order to understand how ecosystems are recovering,” said Dr Coles. “Over that time [since monitoring began], we’ve collected more than eleven thousand individuals from 190 different species.”
Our researchers annually monitor seagrass for north Queensland ports, building the long-term datasets needed to identify how these ecosystems may be changing.
The study was published in Estuarine, Coastal and Shelf Science and funded through a scholarship from North Queensland Bulk Ports Corporation.
