[3] A large part of the upper catchment area of Terrigal Lagoon is rural land, most of which has been cleared.

From 2005 to 2008 a study, led by Dr. John Marsdale from the University of Newcastle, completed a region-wide survey of waterways.

The research team found that abiotic features in the area greatly affected biotic organisms within the lagoon.

Marsdale's team also found that the light level available to shrubbery in the lagoon lessened over during the course of the study due to growth of taller trees taking critical sunlight from the smaller grounded plants.

The potassium levels were affecting not only the fish in the lagoon but also the multitudes of plants that lined the waters edge.