African Wildlife & Environment Issue 76 FINAL

CONSERVATION

season these muddy freshwater pockets are evident as they pulse along the shore, slowly mixing with the sea water as a result of wave action. Its interesting to observe the movement of these pulses, clearlymanifestasdifferentcolourwaters with straight lines separating them, as they respond to each tidal ebb and flow. Satelliteimagesshowthisphenomenon clearly, where summer flood pulses of freshwater discharged through estuaries present as plumes of distinctly coloured water, with clearly defined barrier lines between them. These patterns repeat themselves consistently over time scales recorded by satellite imaging, suggesting that they are persistent.

Image 5 : 4 Februar y 2019

but more importantly across the banks and mudflats associated with pristine systems. Its this pulsing wedge that triggers many of the ecological processes such as spawning. Therefore, a reduction of estuarine flow by over-abstraction of freshwater upstream disturbs the dynamics of this flood pulse, and destroys biodiversity of the oceans some distance away. The presence of muddy floodwaters is common along the coast adjacent to rivers that still have enough base flow to prevent sedimentation of the mouth and the formation of a lagoon. KZN has many lagoons where streamflow has been so reduced that the flood pulse is unable to break through into the open sea. In the rainy

It is these freshwater pulses into the salty sea that drives biodiversity and sustains fisheries. Therefore, to consider water flowing into the ocean as a 'wasted resource', merely speaks of an ignorance about the interconnectedness of ecosystems, of which humans are a part. Environmentally savvy people ought to educate those with such beliefs.

Prof Anthony Turton Centre for Environmental Management University of the Free State

ADVENTURE A WORLD OF in our own backyard

10 | African Wildlife & Environment | Issue 76 (2020)