Carbon Sinks in Estuaries Have Been Degraded by Industrial Activity

The ability of the world’s estuaries, salt marshes, and mangrove swamps to sequester carbon has been seriously degraded by industrial activity, according to a study by Australian researchers. Scientists at the University of Technology, Sydney, examined layers of estuary sediment in Sydney’s Botany Bay for the past 6,000 years. They found that sea grass abundance has declined sharply, while quantities of micro-algae have soared. Increasing nitrogen deposition and pollution are the main culprits in destroying seagrass beds, which have the capacity to store as much as 100 times more carbon than micro-algae. The researchers dated the sediments using radiocarbon dating and determined the plant makeup of the Botany Bay estuary by examining isotopic ratios of seagrass versus micro-algae. Reporting in the journal Global Change Biology, lead researcher Peter Macreadie said the results show the importance of preserving and restoring so-called “blue carbon habitats” in wetlands and estuaries. The partial loss of these carbon sinks has “severely hampered the ability of nature to reset the planet’s thermostat.”