An inspection of the Wilson's Wharf, Grunter Gully, Dry dock and the storm water canal entry to the Durban Harbour as a follow up to the pollution incident has revealed no further evidence of fish kill or dead and decaying marine fauna. The inspection team deployed in response to the fish kill incident has continued its work and the water quality appeared visibly improved since the weekend. Ongoing assessment of the dissolved oxygen levels in the harbour water quality has improved. The measurement of oxygen levels on the greater water body of the harbour, including Wilson's Wharf, the sand banks and harbour mouth have consistently improved over the period of the intensive measurements. The measurements of oxygen levels in water and other water quality parameters were undertaken on 26, 28, 30 December 2007 and 2 January 2008. The measurements were undertaken by City commissioned estuarine scientists Nicolette Demetriades and Professor Ticky Forbes.
The measurements will now continue to be undertaken on a weekly basis until such time the situation is normalised. The oxygen levels in the harbour mouth, in the intake to the uShaka Marine world are normal.What is still of concern is the unstable situation in the harbour water quality spanning the section from the Bluff Yacht Club down to the turning circle near the Dry dock. The measurements show cyclical levels of dissolved oxygen.
During the day, the photosynthesis taking place is causing oxygen levels to be elevated. This is due to algal photosynthesis related to the high organic nutrient load imposed on the system. At night, when there is no sunlight, the algal blooms switch to respiration mode, whereby oxygen will be consumed leading to a reduction in the dissolved oxygen levels. Demetriades advised that the situation would return to its natural state over time. Further, this head waters/estuarine section of the harbour does not mix intermittently with the greater harbor water body, despite the daily tidal exchanges.
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Image and Article source: Highway News
Article taken from the issue: 8th Jan 2008
Labels: Durban Harbour, harbour, oxygen, uShaka Marine