Land drainage, development and land-use intensification since the early 1900s have all contributed to a gradual decline in estuary health. This has revealed itself more visibly in recent years through:
- Loss of sea grass and excessive algae growth. This is making the estuary less suitable for birds and fish to live, breed and feed in.
- Unsafe levels of bacteria in shellfish and a 2018 cyanobacteria (potentially toxic algae) bloom, prompting public health warnings.
- Declining water quality including an increase in oxidised nitrogen which promotes algae growth.
- Less abundance and variety of shellfish, crabs and worms (benthic macrofauna) living in the estuary bed.