Intertidal seagrass in Ireland: Pressures, WFD status and an assessment of trace element contamination in intertidal habitats using Zostera noltei

Abstract Intertidal seagrasshas been selected as a Biological Quality Element for the assessment of ecological status under the Water Framework Directive. In Ireland, two species of seagrass, Zostera marinaand Z. noltei occur in intertidal habitats. This study presents the first comprehensive assessment of the distribution and Water Framework Directivestatus of intertidal seagrassin the Republic of Ireland and Northern Ireland. Most of the areas assessed, using the Water Framework Directive-compliant assessment tool, have a status of HIGH or GOOD. Only two areas were found to have a status less than GOOD and in both, the cause for the decline was smotheringby opportunistic foliose green macroalgae. Linear regression showed a relationship between pressure index scores and Ecological Quality Ratio, showing the relevance of the index as a metric of anthropogenic pressure. Trace elementconcentrations were examined in Z. noltei tissues and Trace ElementPollution Index values were calculated. The relationship between Trace Elementcontamination and Water Framework Directivestatus was examined but the results showed little correlation. However, a relationship between the pressure index and trace elementcontamination was obtained. This assessment provides the most comprehensive overview of intertidal seagrassbeds in Ireland and establishes a strong baseline for ongoing monitoring and assessment under the Water Framework Directive. The data provide key information on the pressures affecting these valuable habitats which will assist in the development of measures to improve and protect our transitional and coastal waters.