05 August 2016
The Department for Infrastructure (DfI) will be moving seaweed that has accumulated on the beach in St Aubin’s Bay, starting on Sunday for a two or three day period.
The seaweed has been building up over the last few days, however this will be the first opportunity Dfi has for effective larger scale clearance. There are limitations as to what DfI is able to do to clear the seaweed including the following:
- clearance is only effective for a few days after the top a spring tide when the seaweed would otherwise be stranded at the high level of the beach
- sea lettuce deposits further down the beach at St Aubin’s Bay are also lying in an ecologically sensitive area, on top of sea grass beds - a protected marine growth, and can’t be easily moved without causing damage. DfI is not allowed to remove seaweed in these areas or drive machinery over them
- due to environmental licencing restrictions, DfI is not authorised to remove seaweed from stony parts of the beach, in particular the First Tower part of the beach.
There are also limitations to the viability of actually removing seaweed from the beach, these include:
- light deposits collected by the DfI Surf-Rake machine can go to La Collette to be mixed with other composting material. However, there is no capacity for large quantities and there would be potential odour issues
- as current methods would only remove sea lettuce contaminated with sand it could not be disposed of at the Energy from Waste Plant due to potential damage to the plant by the sand
- the high salt content in the sea lettuce limits the attractiveness of depositing it directly onto fields.
During the summer season the department tries to keep the top part of the beach, where people sit and play, clear of litter and seaweed/sea lettuce, especially near the slipways, beach concessions and cafés.
It uses a Surf-Rake at times when there are few beach users around so removal is usually limited to early mornings – and then only when tides permit. DfI do not have the resources or remit to remove the seaweed further down the beach.
Causes tackled
DfI and the Department of Environment (DoE) continue to investigate the causes of the build-up of sea lettuce. Reducing nitrates in the streams that flow into St Aubin’s Bay and the inflow into the Sewage Treatment Works will also go some way to help reduce the nutrients available for sea lettuce growth in the bay.
However, as the background levels of nitrates are also high in the Island’s offshore surrounding waters due to its close proximity to the French coast, which is suffering similar problems, this is unlikely to completely eradicate the sea lettuce.
The characteristics of St Aubin’s Bay and our climate make the conditions good for the growth of sea lettuce during the summer months given that these nutrients are available.
DfI and DoE are actively trying to find ways to improve the situation. Recently they saw a specialist machine that was harvesting the seaweed from the water in France. They want to get the machine over to Jersey for a trial, and are close to securing a date from the French organisation.
Download a sea lettuce fact sheet (size 1.24MB)
gov.je