Gamtoos Estuary LTER

The Gamtoos Estuary is situated in St Francis Bay, ca. 50 km west of Port Elizabeth. Gamtoos receives more freshwater compared to the adjacent Kromme Estuary, despite water being abstracted for irrigation and other agricultural activities. Throughout the year, salinity gradients are well established over both vertical and horizontal axes. It is a productive system thanks to an abundance of nutrients that fuel a thriving plankton community and in turn a myriad of consumers including fishes and birds. Read more..

The Gamtoos Estuary is situated in St Francis Bay, ca. 50 km west of Port Elizabeth.  Gamtoos receives more freshwater compared to the adjacent Kromme Estuary, despite water being abstracted for irrigation and other agricultural activities.  Throughout the year, salinity gradients are well established over both vertical and horizontal axes.  It is a productive system thanks to an abundance of nutrients that fuel a thriving plankton community and in turn a myriad of consumers including fishes and birds.  The general perception is that the present ecological state is deteriorating as the quality and quantity of freshwater is declining and impacts from human intervention is rising. In response, Elwandle Node established a long-term research programme in 2013 to enable us to better understand these changes to the estuary as they occur.  Our approach conforms to SAEON's strategy for long-term observations in estuaries, comprising of the following components:

• A continuous monitoring platform (CMP) measuring conductivity (salinity) and temperature with in situ CT sensors deployed in the lower, middle and upper estuary
• Quarterly pelagic ecosystem sampling at 10 fixed stations along the length of the estuary.  Sampling involves physico-chemical variables (temperature, salinity, oxygen, pH, turbidity, secchi depth and light attenuation), nutrients (ammonia, nitrates, silicates and phosphates), total chl-a and mesozooplankton
• Quarterly physico-chemical profiling at 20 fixed stations along the length of the estuary
• Episodic events: Elwandle Node remains on standby to sample episodic events such as floods, storm surges, pollution, plankton blooms and so on.

Observation period: 2013/06/20 - ongoing

SAEON team: Dr Shaun Deyzel, Dr Tommy Bornman, Mfundo Bizani