Abstract
Enrichment of nutrients and metals in seawater associated with anthropogenic activities can threaten aquatic ecosystems. Consequently, nutrient and metal concentrations are parameters used to define water quality. The European Union’s Water Framework Directive (WFD) goes further than a contaminant-based approach and utilises indices to assess the Ecological Status (ES) of transitional water bodies (e.g. estuaries and lagoons). One assessment is based upon the abundance of opportunistic Ulva species, as an indication of eutrophication. The objective of this study was to characterise Ireland’s Ulva blooms through the use of WFD assessment, metal concentrations and taxonomic identity. Furthermore, the study assessed whether the ecological assessment is related to the metal composition in the Ulva. WFD algal bloom assessment revealed that the largest surveyed blooms had an estimated biomass of 2164 metric tonnes (w/w). DNA sequences identified biomass from all locations as Ulva rigida, with the exception of New Quay, which was Ulva rotundata. Some blooms contained significant amounts of As, Cu, Cr, Pb and Sn. The results showed that all metal concentrations had a negative relationship (except Se) with the Ecological Quality Ratio (EQR). However, only in the case of Mn were these differences significant (p = 0.038). Overall, the metal composition and concentrations found in Ulva were site dependent, and not clearly related to the ES. Nevertheless, sites with a moderate or poor ES had a higher variability in the metals levels than in estuaries with a high ES.
Highlights
Anthropogenic activities occurring in the coastal areas can produce an array of stressors on the local biological communities
The survey revealed that the two sites categorised as ‘Poor’, with the lowest Ecological Quality Ratio (EQR) scores in this study, i.e. Courtmacsherry and Clonakilty, had the largest algal blooms, with an estimated biomass of 2164 and 845 metric tonnes, respectively
Sequence comparisons showed that seven of the Irish Ulva blooms included in this study contained U. rigida, while the New Quay bloom comprised U
Summary
Anthropogenic activities occurring in the coastal areas can produce an array of stressors on the local biological communities. These pressures can change the aquatic conditions producing different forms of pollution (e.g. dystrophy caused by an excess of eutrophication, acidification, metal toxicity, biological invasions, and pollution by organic compounds and organic matter) that degrade the environment. This environmental degradation is significant in the coastal zone, where human activities have been historically concentrated [1]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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