Marine Macroalgae Assessment Tool (MarMAT) for intertidal rocky shores. Quality assessment under the scope of the European Water Framework Directive

The Water Framework Directive (WFD) requires European Member States to assess the Ecological Quality Status (EQS) of their water bodies based on Biological Quality Elements (BQEs). A tool called MarMAT (Marine Macroalgae Assessment Tool) was developed to implement the WFD in Portugal, which assesses the EQS of Portugal's coastal intertidal rocky shores. MarMAT is a multimetric method that is compliant with the European WFD requirement. It is based on the composition (Chlorophyta, Phaeophyceae and Rhodophyta) and abundance (coverage of opportunists) of marine macroalgae. This study focused on the demands of the WFD to have the assessment methodologies legally accepted by the European Commission. The following factors were examined: (a) the response of MarMAT against anthropogenic pressures; (b) the ability of MarMAT to report all of the five quality classes (bad, poor, moderate, good and high); and (c) the performance of MarMAT, specifically in comparing the RSL (Reduced Species List) methodology with the utility of including the abundance (coverage of opportunists) metric and the necessity of locally adapted reference conditions and boundaries. MarMAT was high inversely correlated (p < 0.001) with anthropogenic pressure. MarMAT also successfully reported all of the quality classes (bad to high) and captured the community changes more accurately when using the coverage of opportunists metric. Because MarMAT satisfactorily covered all of the issues examined, MarMAT may be accepted as a compliant assessment methodology in the scope of the WFD requirements.