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Water Quality in Cowes Harbour,

Water Quality

Cowes Harbour Commission (CHC) works in partnership with Island Rivers (the Isle of Wight Catchment Partnership), Solent Forum, The Green Blue and other partners throughout the Solent to help identify and address water quality issues. Regional coordination and catchment partnerships are extremely important as the high levels of nutrients in our coastal waters are from a wide variety of mainly land-based sources throughout the Solent area.

In the Medina Estuary, nutrients (mainly nitrogen in the form of nitrates) are a significant water quality issue. They enter the catchment as a result of runoff from farmland and urban areas or as discharges from the sewerage system, faulty sewage connections or vessels. The problems caused by nutrients affect how we use the estuary and can have a huge impact on the plants and animals.

Nitrogen is a plant nutrient but too much of it in estuaries can lead to excessive growth of opportunistic green seaweed (also called macroalgae). The effect of this can be seen at low water as thick green seaweed mats covering the intertidal mudflats. It looks unsightly and affects recreation if it clogs up propellers or washes up on slipways. It can also affect the birds that feed on the mudflats because their bills cannot penetrate the weed or because it changes the availability of their mud-dwelling prey items. Smothering of saltmarsh can also occur that prevents plant growth and increases bank erosion. When the seaweed breaks down either after a period of rough weather or at the end of the growing season it can give off unpleasant smells typically that of rotten eggs or vegetables, which can sometimes incorrectly be attributed to sewage pollution.

This problem is not confined to the Medina Estuary; it occurs in many sheltered, muddy estuaries within the Solent area and elsewhere where conditions are suitable. It is referred to as ‘eutrophication’, which is the process by which nutrient enrichment causes excessive algal growth that then causes ecological disturbance. In most Solent estuaries, the problem nutrient is usually nitrate (a type of nitrogen) whereas in freshwaters the problem nutrient is usually phosphate (a type of phosphorus). In the Medina Estuary both nitrate and phosphate may contribute to excessive algal growth.

For more information about nutrients in the Medina see the briefing paper compiled by the Environment Agency.

What can we do to help improve water quality?
The impact of excess nitrates will only be dramatically reduced by long-term widescale projects led by the Environment Agency and working in partnership with organisations throughout the Solent and the catchments of all rivers that flow into it. However, as individuals we can help to minimise any additional input from our boats or homes.

• Use a holding tank and pump-out* system if possible and if not possible then only discharge sewage from your vessel out at sea.

(*Boaters are encouraged to use the free pump-out at Shepards Marina, available year round. The pump-out berth is located on the south pontoon at Shepards. Call the marina in advance on VHF Ch80 and a Berthing Master will be glad to help.)

• Ensure domestic septic tanks are maintained and sewage pipes are correctly connected.

• Support and encourage the use of a variety of environmental ‘Good Practice’ within both the estuary and the catchment to help reduce nitrates.

• Recycling facilities are available at all marinas in Cowes Harbour – please use them where possible and help us improve the environment of the Island.

See also our section on ‘Environmental Campaigns’. [link to come]

Report Pollution / Discharges on 0800 807060
Harbour users can play a key role by helping to report any incidents of pollution or discharges through the Environment Agency’s incident hotline number 0800 80 70 60, which is open 24/7. This will ensure that incidents are recorded systematically, and any problem areas can then be identified.

If necessary CHC can enforce the Cowes Harbour General Directions:
5.16. Discharge of Oil, Sewage and Garbage - No person is to cause the discharge into the Harbour of any:
5.16.1. Oil or oily residues/discharge.
5.16.2. Sewage or other pollutant materials into Cowes Harbour when moored within or alongside marina mooring facilities or alongside pontoon berths having direct pedestrian access to the shore.
5.16.3. Garbage, plastics, or foodstuffs, except into designated receptacles ashore.

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