ÌÇÐÄvlog¹ÙÍø

Coastal lagoons are important biodiversity hotspots. Credit: Darcy Whittaker/@dwhittaker99_photo

When a coastal lagoon flips from crystal-clear waters to murky green soup, it’s not the fish that sound the alarm, it’s the microbes. These tiny organisms respond first to rising salt stress and nutrient pollution, acting as early indicators of ecosystem decline.

Environment Institute member Dr Christopher Keneally is leading research that puts microbial communities at the centre of lagoon health and restoration strategies. In a new global review, Dr Keneally and colleagues examined how climate change and human pressures are altering these systems, and what we can do to turn the tide.

Why coastal lagoons matter
Although they only make up about 13% of the world’s shoreline, coastal lagoons punch well above their weight in ecological and economic importance. These shallow, semi-enclosed bodies of water support global fisheries, buffer storm surges, and provide spaces for recreation. They also help filter nutrient runoff and store significant amounts of atmospheric carbon.

Sitting at the interface of rivers and oceans, coastal lagoons are highly sensitive ‘sentinel ecosystems.’ Changes in climate or land use upstream rapidly cascade through these systems, making them an early warning site for broader environmental shifts.

Ìý

The importance of microbes
Microbes play a crucial role in keeping lagoon ecosystems in balance. They recycle nutrients, lock away carbon, and form the base of the food web. But when nutrient levels spike or salinity increases, that balance can tip and lead to toxic algal blooms, fish kills, and spikes in greenhouse gas emissions

In short: microbes are the first to respond and often determine whether a lagoon thrives or collapses.

What the research found
In his recent review, Dr Keneally investigated global studies on degraded lagoons to answer three key questions:

1. How does rising salinity change microbial communities?
2. What early warning signs can managers look for?
3. What practical actions can reverse decline?