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WQ.229/2022
WRITTEN QUESTION TO THE MINISTER FOR THE ENVIRONMENT BY DEPUTY L.V. FELTHAM OF ST. HELIER CENTRAL
QUESTION SUBMITTED ON MONDAY 17th OCTOBER 2022 ANSWER TO BE TABLED ON MONDAY 24th OCTOBER 2022
Question
Will the Minister detail what work, if any, is being undertaken to reduce the sea lettuce on our shoreline (particularly in St. Aubin’s Bay) next summer and in future years?
Answer
The quantity of nitrates entering St Aubin’s Bay both from land run-off and from the waste- water treatment works (WWTW) at Bellozanne impacts the growth of the nuisance weed, sea lettuce. The Government of Jersey has recognised the importance of reducing levels of nitrates for some time, particularly given that the bay receives run-off from a large proportion of the island.
Relevant stakeholders, including potato and dairy farmers and officers from Jersey Water and Natural Environment, have worked closely together for some time to reduce levels of nitrates in water across the island. This includes streams and groundwater entering the bay, and by default the quality of water being treated by the WWTW. Their collaborative work has been very successful and average nitrate levels in streams and groundwater have reduced by one-third during the past 20 years (the annual average level of nitrates in streams is currently less than 50 mg/l).
The new WWTW is currently being built and will be fully operational by the end of 2023. The new facility will result in lower levels of total nitrogen entering the bay and increased volumes of treatment during storm conditions leading to less shock loading of total nitrogen. These improvements will help limit the annual volume of this nuisance weed. A discharge permit issued under the Water Pollution (Jersey) Law 2000 will ensure that levels of potential pollutants (including total nitrogen) entering the Bay are regulated.
The excessive growth of sea lettuce in St Aubin’s Bay is highly complex. Multiple factors contribute to its growth, including bay topography, land reclamation, sea temperatures, nutrient inputs and more.
Natural Environmental officers undertake regular monitoring of St Aubin’s Bay in line with the EU Water Framework Directive (WFD). This work gathers base line data to assess the chemical and ecological status of the bay. In 2015, following the collection of 3 years of data, the water quality of St Aubin’s Bay was classified as ‘moderate’ according to the classification of the WFD. This was driven by the outcome of the opportunistic sea lettuce and the level of dissolved available inorganic nitrogen, both of which are indicators of nutrient enrichment. This classification is currently being updated.
Additional nutrient monitoring of the surf (inshore) zone of St Aubin’s commenced in 2014. This will lead to a better understanding of the source and distribution of nutrients across the bay and identify the conditions responsible for the variation in the growth of sea lettuce. Over time, the data collected will be used to assess the impact of the expected decrease in nutrient loadings from the new WWTW and from the work of the Action for Cleaner Water group tackling land- based sources.
The IHE Operations & Transport directorate responsible for removal and disposal of sea lettuce along the amenity beach areas of St Aubin’s Bay has increased the amount harvested, and disposed of 5,416 tonnes of green seaweed directly to suitable farm land this year. This provides the landowners with a source of organic fertiliser thereby reducing the amount of additional chemicals being used by the industry.
It remains that sea lettuce will always be present and that it will vary in quantity from year to year.