I admit, I have become a bit obsessed with the ever changing colour of the water in the yacht basin near the Aquarium. The cause of this phenomenon happened a few weeks ago when the Waterfront experienced a mass fish die-off. Noticeable impacts included a harsh smell and the light green colouring of the water in the basin.
This event was caused by an algal bloom coinciding with a large influx of maasbanker (horse mackerel) into the basin the sighting of whales behind the shoal of maasbanker (horse mackerel) suggest that they were chased into the basin on the day, however it cannot be said with absolute certainty that this was the cause of the shoal entering the basin, unusually low wind conditions and a neap tide.
This process, known as eutrophication, happens due to the high nutrient level in the area, allowing for an algal bloom to occur. Once the algae reach a critical level, they consume much of the oxygen in the area, with the resultant crash in the population. This then puts additional pressure on the oxygen level decreasing it further, to the point where the fish in the area can no longer breathe and also succumb.
This vast biomass settles to the bottom and starts to decompose, removing even more oxygen from the area resulting in good bacteria being replaced by the heterotrophic bacteria that survive in a very low oxygen environment. These bacteria start an anaerobic process that releases hydrogen sulphide which causes the unpleasant odour that can sometimes be smelt as well as the colour of the water. The colour of the water is also due to the vast amount of biological material (due to the decomposition of the fish on the bottom) suspended in the water.
Restoring a balance within our bodies of water requires effective control of oxygen levels to ensure that the natural systems are able to utilise the nutrients released by decomposition on the large biomass sitting on the bottom of the basin. The Waterfront are doing this by restoring oxygen levels to our basin through an aeration process in select areas. This will increase water movement and the oxygen content of the area, thereby providing an environment in which natural systems can flourish. This is an environmentally friendly technique to rejuvenate our water bodies and is being closely monitored by the marine biologists who are advising the V&A Waterfront.
We wish the Waterfront all the best as they work tirelessly to get the Marina back to its healthy state. In the mean time, head down to the yacht basin and hop on one of the City Sightseeing boats and experience the unique occurrence.