‘Glistening green mudflats might look healthy – but they are a sign that all is not well in our harbour’
Aparish councillor, as they gazed upon an expanse of glistening green mudflats, opined that Chichester Harbour looked remarkably healthy, writes R.C.J. Pratt for Save Our South Coast Alliance (SOSCA).
Sadly mistaken, was our councillor. Why? One big word we have to cogitate. The word is eutrophication.
Eutrophication (from Greek eutrophos –well nourished) is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients. It has also been defined as ‘nutrient-induced increase in phytoplankton productivity’.
Eutrophication in freshwater ecosystems is almost always caused by excess phosphorus. In sea water it is caused by excess nitrogen often released from nitrates washing off agricultural land and other human activities including homes and industries.
Hence our rivers suffer from phosphates and our harbours from nitrates. In fact, the whole Solent has been enriched by nitrates. Enriching in this context means impoverishing the natural habitat.
This eutrophication has been kicking around for the last 80 years or so, but only now showing the outward signs of an ignominious conclusion: the premature demise of our bon vivant and that of our precious Sussex natural assets.
Sources reveal the consequences for shallow water coastal areas. The Chichester Harbour Conservancy have received research reports that show that the coverage of sea grasses has been reduced by over 50 per cent since 1949. The main sea grass, spartina, is a key measure of the health of our harbour.
Not only has it framed those 1940s, 1950s and early 1960s photo snaps of harbour-side idyll, but it has also held the mudbanks up, maintaining wonderfully intimate little backharbour channels for children to explore in summer and ducks, geese, grebes and waders to thrive in winter.
This habitat is being trashed. The destruction of the spartina makes for greater coastal erosion as an important buffer against storm damage is removed, the mud banks slump with no roots to hold them up and the character of the harbour slowly changes.
The process has an annual cycle related to the rise in critical temperature around April, producing algal blooms that can carpet the salt flats as the tide recedes. It not only chokes the surface, making it difficult if not impossible for birds to feed and invertebrates to survive, but it is responsible for forming the algal mats that suffocate and kill the spartina.
These observations have caused Natural England (NE) to be alerted to the progressive deterioration of the Chichester Harbour Site of Special Scientific Interest (SSSI).
Dinghy sailors in the harbour who have sailed the waters for decades have seen this continued deterioration, the algae being so thick at certain times that it wraps around rudders and foils.
The sources of this excess nitrate are hotly debated and apportionment of causes can vary.
In Chichester Harbour much comes in from the Solent which has been fed by the surrounding land fluvial runoff for decades. The run-off comprises that from agricultural land, urban areas and waste water delivered by the water companies into the sea.
However, in recent years increased concentrations have been observed by NE in the upper reaches near to the sewage outfalls and the agricultural land drains. Farmers don’t want to waste expensive nitrates, so with modern techniques, this has been reduced.
Planning authorities have responded and require nutrient budgets to be produced before granting consent to development. But the devil is in the detail and schemes to swop nitrate emissions on development proposals for net nitrate-emission reductions on remote sites (even ones on farmland in quite different counties) is controversial if not nonsensical.
The technical capacity for planning authorities to accurately assess developers’ nitrate budget proposals is also problematic. Many just use a onesize-fits-all methodology.
In Hampshire the absence of adequate forward planning has prevented consents being given on large-scale developments.
With nitrates, and phosphates, it seems we are paying much lip-service while practical measures are absent.