Statistical Analysis of Physico-chemical Properties of the Estuaries of KwaZulu-Natal, South Africa

In general, estuaries may be classified variously according to inlet dynamics, geomorphology or
whether they are tide or river dominated or, on a combination of all three factors. In KwaZulu-Natal (KZN),
South Africa, the four recognised estuary types are temporary opened-closed estuaries (TOCEs), permanently opened estuaries, estuarine lakes and river mouths. Since physico-chemical parameters are important in defining the estuarine environment, multiple Pearson correlations were performed between summer datasets of five of these parameters: temperature (oC), salinity (ppt), pH and turbidity (Nephelometric Turbidity Units (NTU)) according to clustered estuary types for all estuaries of KZN. It was found that very few significant relationships exist in all estuary types. These results are partly reflective of the sampling dataset. During summer, open mouth conditions commonly prevail for several estuaries following seasonal hinterland rainfall. Mixing of waters due to tidal influences and fluvial input from the upper catchment in KZN’s shallow estuaries is known to inhibit stratification resulting in fewer pycnoclines and greater turbidity fluctuations. pH changes are closely linked to density changes (temperature and salinity) in water hence statistical relationships may not always be observable. It is clear that physico-chemical interactions are complex and long term sampling with seasonality and mouth state dynamics need to be taken into consideration. There is a need to develop a more holistic understanding of estuarine ecosystem functioning in this region.