Bow-tie analysis

The bow-tie analysis for eutrophication shows the relationships between the DAPSIR components which need to be considered in a cumulative effects assessment. Human activities have been identified which contribute to eutrophication pressures and have the potential to both individually and cumulatively contribute to biodiversity state changes: transport – shipping; industrial uses; wastewater treatment and disposal; aquaculture and agriculture. The main pressure associated with eutrophication is the input of nutrients from these human activities and climate change . These can lead to eutrophication changes in state through effects that increase biomass (algal blooms) and increase turbidity and anoxia, leading to decreases in species diversity and trophic cascade in food webs.

The State section describes the potential ecological impacts associated with eutrophication in the marine environment. The input levels, frequency of occurrence, spatial extent and exposure to different human activities all collectively contribute to the extent to which eutrophication pressures are exerted on pelagic habitats ; Fish ; benthic habitats and food webs . To undertake a full quantitative analysis of cumulative effects requires consideration of the exposure pathways and ecological impacts. Further analyses and evidence of ecological impacts are required in order to progress the assessment of cumulative effects.

Eutrophication can also combine with other pressures to collectively affect marine species and habitats. The assessment of cumulative effects is considered within the biodiversity thematic assessments on Pelagic Habitats ; Fish ; Benthic Habitats and Food Webs .