Diffuse and concentrated nitrogen sewage pollution in island environments with differing treatment systems

Abstract

Macroalgae is an under-utilised tool as a bioindicator of anthropogenic nitrogen loading to the coastal environment in the UK. This study compared two island systems—Jersey (Channel Islands) and St Mary’s (Isles of Scilly) to assess how differing sewerage infrastructure affects nitrogen loading. A total of 831 macroalgae samples of Fucus vesiculosus and Ulva sp. were analysed for nitrogen isotopes (δ15N). Elevated δ15N values were recorded for Jersey (> 9‰) in St Aubin’s Bay—caused by the outflow of the Bellozanne Sewerage Treatment Works (STW). δ15N isoplots maps indicate low diffusion of nitrogen out of St Aubin’s Bay. St Mary’s produced a varied δ15N isoplot map in comparison. δ15N was typically lower and is attributed to a smaller population and inefficient STW. Outflow of sewage/effluent at Morning Point, Hugh Town and Old Town produced elevated δ15N values in comparison to the island average. St Mary’s inefficient sewerage treatment and reliance on septic tanks/soakaways complicates δ15N interpretation although it still indicates that nitrogen pollution is an island-wide issue. Future sewerage development and upgrades on islands are required to prevent similar effluent environmental issues as recorded in St Aubin’s Bay. This study advocates the use of macroalgae as a bioindicator of nitrogen effluent in the marine environment.

Nitrogen isotopes in herbaria document historical nitrogen sewage pollution in the Mersey Estuary, England

“…34,69 Elevated δ 15 N values >+16‰ are rarely recorded in macroalgae studies 45,74 (Gröcke et al , unpub. data), and only a handful of studies have recorded values >20‰, 21,25,45,74 and none previously in the UK. Although BOD assessments indicate that the Mersey Estuary has improved, the Environment Agency reports that it is “not achieving good status” due to industry, 63 with no indication of water detriment from the water industry.…”

“…It is proposed that the stability of d 15 N in this time interval was a result of stricter controls on discharges, monitoring and increased chemical processing (i.e., ammonia) in wastewater treatment plants. 25,61,72,73 During this time interval, stricter regulations were implemented by the European Union on the UK government to address water quality issues. This legally enforced that the level of nitrate released into freshwater and marine environments be set to a maximum limit of 50 mg l −1 (or 11.3 mg l −1 of nitrate N).…”

“…[22][23][24] Although there are numerous studies that have used macroalgae d 15 N to identify sewage pollution, there are only a handful of studies that exist for the UK despite the ongoing sewage pollution crisis. 17,21,25,26 Museum herbarium collections contain a vast amount of ecological and environmental information that is oen underutilised in the study of recent anthropogenic change. 27,28 Only recently have researchers considered herbaria as a tool to track biogeographical, environmental, and climatological changes.…”

“…22–24 Although there are numerous studies that have used macroalgae δ 15 N to identify sewage pollution, there are only a handful of studies that exist for the UK despite the ongoing sewage pollution crisis. 17,21,25,26…”

Anthropogenic modifications: impacts and conservation strategies

“…The researchers highlight the need to establish systems for monitoring the interior to understand the impact of marine ecosystems and biogeochemistry. With an equal focus on the marine system, particularly the coastal one, Alldred et al used macroalgae as a bioindicator of the anthropogenic nitrogen load on the coasts of the United Kingdom 8 . The authors compared two island systems, Jersey (Channel Islands) and St Mary's (Isles of Scilly), to assess how different sewage infrastructure affects nitrogen loading and demonstrated that upgrading sewer systems in the islands is necessary to reduce environmental problems.…”