We all depend on the environment around us to stay healthy. It turns out that the same is true for coastal ecosystems. Their connections with other ecosystems and the land are critical to their own health.
Connected ecosystems will be a key discussion point for Australian Rivers Institute staff who are presenting at the World Science Festival in Brisbane during the week of 21st March.
This blog is a brief taste of some of the research we have been doing on connected ecosystems.
Connections help reefs recover from floods
Professor Rod Connolly has been studying connections among coastal ecosystems for decades. During the catastrophic 2011 Brisbane flood, he observed first hand the importance of keeping the right connections across ecosystems.
Moreton Bay sits right next to Brisbane and its ecosystems are no exception. Professor Connolly’s team discovered that coral reefs were badly affected by the flood.
Sediment plumes washed out of the river by the flood badly affected Moreton Bay’s coral reefs, many of which were simply covered with mud.
Coral recovery depends on having clean space for young corals to grow into. Unfortunately, after the flood seaweeds took over the reefs, preventing coral recovery.
However, reefs that were situated near mangroves did much better. Professor Connolly’s team found that a seaweed eating fish, known locally as rabbit fish or black trevally, preferred to live on reefs near mangroves. The rabbit fish tend to move up into mangroves at high tide but return to reefs at low tide.
Having the rabbit fish around meant that they keep the seaweed levels down, giving the corals a chance to recover.
Extremes in weather can make or break connections
Many types of fish like to forage or shelter in mangroves as youngsters, but then migrate to coral reefs at an older age.
But finding those unique locations where reefs and mangroves co-occur might be challenging for young fish. Many fish have an extended larval phase where they wander about in the open ocean. Whether they end up near mangroves and corals depends largely on where they get pushed by currents, winds, and waves.
Dr Chris Brown led a study that found coral reefs that are sheltered from wind and waves are really important for healthy fish populations.
Fish larvae born in sheltered locations are likely to hang around, because they won’t be moved around as much by wind and waves.
It turns out that mangroves really like sheltered locations too. So fish larvae born in sheltered locations have a survival advantage: they stay near mangroves and can easily find coral reefs when they are old enough.
Protecting these sheltered locations from fishing and developement, like marinas, is therefore important for the health of coral reef ecosystems.
Mangroves help clean the water and the air
Dysfunctional connections can be bad for coastal ecosystems.
Take our rivers, industry, logging and agriculture all contribute to pollutants, like fertilizers, the find their way into the ocean via the rivers.
In fact, run-off of pollutants from on land is a major threat to the health of the Great Barrier Reef.
Dr Fernanda Adame’s work is showing how wetlands, including mangroves, can help clean the air and water.
As mangroves grow they capture carbon dioxide from the air which they store in their branches, leaves and roots. Conserving mangroves so they capture carbon dioxide can help slow greenhouse gas emmissions.
Mangroves and other wetlands are also traps for water borne pollutants.
Water slows as it flows through wetlands, giving the ecosystem time to process pollutants and clean up the water. Dr Adame is currently studying how wetlands may help trap pollutants from on land, and contribute to saving the Great Barrier Reef.
So conservation work to keep mangroves healthy can be important for both clean air and water.
Run-off from on land can help or hinder coastal ecosystems
Keeping healthy coastal ecosystems is not just about reducing run-off, many of them require freshwater to thrive. So it is the balance that counts.
On the other side of Cape York Peninsula from the Great Barrier Reef, Professor Michele Burford has been studying the connections between rivers and coastal mudflats.
Coastal mudflats make up a huge area of the Gulf of Carpentaria. The Gulf supports one of Australia’s most valuable prawn fisheries, millions of threatened migratory birds and a thriving indigenous culture.
Professor Burford and her team discovered that the humble mudflats are a critical part of the Gulf’s ecosystems and contribute to supporting its people and industries.
During the wet season, freshwater runs out onto the mudflats creating an extensive shallow muddy region. Algae love to grow under these conditions, and they really flourish on the mudflats.
Algae are the base of the Gulf’s food chains, so it is likely that this infrequent growth is important to ultimately providing food for prawns, fish, birds and people.
Come and meet us to find out more about connected ecosystems
We hope you can come and meet us at the World Science Festival. You can find a list of all of our members who are attending, covering everything from healthy drinking water, to the action needs to save ocean ecosystems here.