How does freshwater impact on estuaries?

Estuaries are coastal bodies of water where the freshwater from rivers and streams mixes with the salt water of the ocean.

As freshwater travels down a catchment, ki uta ki tai, it picks up and carries nutrients and sediment to an estuary that can impact the estuary health.

Increased nutrients can lead to the growth of problematic phytoplankton and algae which can reduce the oxygen available in the water, degrading the habitat for aquatic life (fish, shellfish, plants,etc), and negatively impacting the environment.

Sediment carried down a catchment and deposited in an estuary can affect water clarity and the distribution of fish and invertebrates living in the estuary.

Bacteria from animal faeces can be carried in rainfall runoff from the land to rivers and then in to estuaries, making shellfish unsafe to harvest and eat, and increasing risk of getting sick if you swim or have contact with the water.