Eutrophic standing waters are nutrient-rich, naturally or through artificial enrichment. They are characteristically green in colour due to the dense populations of algae.

Key Characteristics

  • Site: Nutrient-enriched, anaerobic mud
  • Main species: Algae
  • UK: 1785 km2
  • NI: 940 km2

Habitat Description

  • Eutrophic standing waters are rich in plant nutrients & are characterised by algae populations in mid-summer.
  • The beds are typically composed of dark anaerobic mud that has high organic matter content.
  • Water bodies such as lakes, reservoirs, gravel pits may become eutrophic through natural or artificial enrichment (e.g. input of fertilisers).
  • Nitrogen & phosphate, which are required for plant growth, are present in high concentrations from natural or artificial sources. Inorganic nitrogen & total phosphorus are the main indicators of the nutrient content of lakes. Eutrophic standing waters have nutrient levels of >0.035 mg 1-1 total phosphorus & >0.5mg 1-1 total inorganic nitrogen.
  • Characteristic plant species vary with the area, nutrient levels & exposure. They include duckweeds Lemna spp., white water-lily Mymphaea alba, yellow water-lily Nuphar lutea & spiked water-milfoil Myriophyllum spicatum.

Current Status in UK & Northern Ireland

  • A large proportion (72%) of lakes in Northern Ireland have a surface area of <2 ha, representing only 1.2% of the total water surface. In NI lakes cover approximately 4.5% of the total surface area.
  • There is an estimated 1785 km2 of eutrophic standing water in the UK (UK Biodiversity Steering Group, 1998)
  • Northern Ireland contains a high proportion (>52%) of the UK resource, especially in the east & west lowlands (NIBG, 2000). The EHS estimated that eutrophic standing water covers 940 km2 in NI.
  • The largest eutrophic standing waters in Northern Ireland are Lough Neagh & Lough Beg & Upper Lough Erne.
  • Eutrophic standing waters are under considerable pressure from human activities, which may reduce their biodiversity. Threats include:
    – Agricultural practices may pollute water bodies through inappropriate application of slurry or inorganic fertilisers.
    – Eutrophication is a considerable concern in Northern Ireland waters, which occurs due to the release of nutrients, particularly phosphorus. This stimulates excess phytoplankton growth, which results in a cloudy underwater environment & submerged plants do not receive sufficient sunlight.
    – Drainage & water removal can result in low water levels, which can cause drying out of important wetland habitats & prevent fish from spawning.
    – Dredging & bank side vegetation clearance may increase suspended sediment & nutrient concentrations.
    – Invasive species, such as the Zebra mussel, can negatively affect native species by direct competition and/or altering the natural habitat.
    – Recreational activities (e.g. boating) can damage aquatic plants & disturb bird populations.
    – Fish farms on rivers may release waste & partly decomposed food into natural waterways, which may lead to enrichment, increased suspended solids & decreased oxygen levels.

Designated Sites

  • Lough Neagh & Lough Beg

Further Information