Rocky Reef Assessment in the Derwent Estuary

Our team at the Institute for Marine and Antarctic Studies (IMAS) has recently published a new report looking at the health of rocky reefs in the Derwent estuary. We used our new Rapid Visual Assessment methodology that has been developed to identify the early signs of organic enrichment on reef ecosystems.  

This project was initiated in 2019 when the Derwent Estuary Program (DEP) engaged our team to undertake a rocky reef monitoring program in the Derwent estuary prior to aquaculture expansion in Storm Bay.  

It is important to understand the current health of rocky reefs so that any changes can be monitored over time. This is particularly important in areas of high human activity which can change the natural balance of nutrient availability in coastal water and potentially lead to organic enrichment. These include urban areas, ports and marinas, agriculture, and marine aquaculture.  

Key findings from the report show that:  

• All reefs surveyed are dominated by kelp species which provide canopy cover over the reef creating habitat and shelter for a wide range of species.  

• The amount of canopy cover over reefs varies throughout the year. At the sites surveyed, there was higher canopy cover in autumn (March) than in winter (July).  
• Some reefs surveyed (at Bellerive and Tranmere) showed signs of low to moderate nutrient enrichment, particularly in the autumn (March).  
• Findings from this project can be used to benchmark any future change which may occur to rocky reefs in the area.  

For more information, please visit our Rocky Reef Interactions web page