Ecological status assessment in Irish coastal and estuarine sedimentary habitats using the Water Framework Directive Ecological Quality Ratio Infaunal Quality Index

The Infaunal Quality Index (IQI) is an Ecological Quality Ratio (EQR) developed for the purposes of monitoring coastal and polyhaline (estuarine) waterbodies to meet the requirements of the European directive Water Framework Directive WFD. In Ireland, from 2010 to 2023, IQI was calculated from benthic macrofaunal and sediment data using a custom Microsoft Excel software tool with embedded Visual Basic macros to determine suitable reference conditions for each station sampled. This involved the analysis of 4374 stations in 354 surveys of coastal and estuarine Assessment Groups (AG). The macrofaunal data was processed using a taxa library with a fixed taxonomy. An updated software tool, IQI V2 was released in 2024 including a substantially revised taxa library. Intercalibration between the IQI tools in coastal and estuarine surveys (Assessment Groups; AG) revealed that using all of the survey data, the agreement between the IQI was largely classified as “Very Good”. This is less than the required classification of “Almost Perfect” required for intercalibration between different EQR under the requirements of the WFD. This was true of sample stations, AG and also in the classifications of the probabilities that the true mean EQR value for AG was above the critical Good/Moderate boundary in WFD ecological status assessment. The difference in output between the tools appears to be caused by differences in how the surveyed fauna taxonomy is entered into the tools, what taxonomic groups are included in calculating the EQR, and how taxa abundances are processed. When the stations dataset was reanalysed with the removal of 2033 stations where IQI V2 did not include >10% of the fauna in the EQR calculation, the agreement between the tools was greatly improved. The interpretation of IQI monitoring data from AG surveyed following the introduction of the IQI V2 tool should involve the recalculation of IQI from that waterbody in previous years to place subsequent findings in context. The use of IQI in monitoring salmon aquaculture impacts in coastal waters was assessed using five years of survey data collected at three aquaculture sites on the west coast of Ireland (total 14 surveys). IQI was modelled as a function of distance from the sea pens, sediment organic content and the depth of the sediment apparent redox potential discontinuity (aRPD), including a random effect of aquaculture site. IQI decreased in response to increasing organic enrichment at the aquaculture sites (measured as increasing sediment organic content and decreasing aRPD). IQI was effective in mapping aquaculture impacts on coastal benthic communities. Adoption of IQI in aquaculture monitoring would facilitate improved management of coastal waterbodies by providing a common framework for aquaculture and other potential stressors to be assessed and managed in a cohesive network.

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University of Galway

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University of Galway Theses (Research Masters Theses)