The salinity of Oyster Harbour is close to marine due to the permanent opening to King George Sound.

There is a small difference in salinity particularly at surface water in the north. This is caused by the freshwater inflow after rain from the Kalgan and King rivers.

Dissolved oxygen is the amount of oxygen dissolved in the water through absorption from the atmosphere and/or as a result of photosynthesis by seagrass or algae.

Dissolved oxygen concentrations range from 7-8 mgL^-1 which indicates excellent water quality throughout the harbour.

Water clarity is a measure of how far light penetrates into the water relative to the depth of the bottom.

The water clarity of the north sites at Oyster Habour is good for shallow water, which naturally has more suspended organic matter.

At the southern sites light penetrates approximately 4.5 meters which is excellent for estuaries.

*Water clarity is measured as Secchi depth

Nitrogen levels in Oyster Harbour were well below guideline values. The guideline values are an indication of the approximate nitrogen levels that may impact the health of an estuary.

There was a slight elevation in nitrogen for the northern sites at the surface. This is from nutrients being washed in from catchment land uses through the King and Kalgan rivers.

*Guideline is the ANZECC (2000) guideline value for south-west estuaries

Phosphorous levels in Oyster Harbour were below the guideline values. The guideline values are an indication of the approximate phosphorous levels that may impact the health of an estuary.

There was a slight elevation in phosphorous for the northern sites at the surface. This is from nutrients being washed in from catchment land uses through the King and Kalgan rivers.

*Guideline is the ANZECC (2000) guideline value for south-west estuaries

Algae levels in Oyster Harbour were below the guideline values. The guideline values are an indication of the approximate algae levels that may impact the health of an estuary.

There was more algae at the northern site, likely caused by the increase in nutrients at the northern sites. The prevailing winds in the harbour may also push organic matter north concentrating algae.

*Guideline is the ANZECC (2000) guideline value for south-west estuaries