An ecosystem-based approach to assess the status of Mediterranean algae-dominated shallow rocky reefs

A conceptual model was constructed for the functioning the algae-dominated rocky reef ecosystem of the Mediterranean Sea. The Ecosystem-Based Quality Index (reef-EBQI) is based upon this model. This index meets the objectives of the EU Marine Strategy Framework Directive. It is based upon (i) the weighting of each compartment, according to its importance in the functioning of the ecosystem; (ii) biological parameters assessing the state of each compartment; (iii) the aggregation of these parameters, assessing the quality of the ecosystem functioning, for each site; (iv) and a Confidence Index measuring the reliability of the index, for each site. The reef-EBQI was used at 40 sites in the northwestern Mediterranean. It constitutes an efficient tool, because it is based upon a wide set of functional compartments, rather than upon just a few species; it is easy and inexpensive to implement, robust and not redundant with regard to already existing indices.

Global patterns of kelp forest change over the past half-century

Kelp forests (Order Laminariales) form key biogenic habitats in coastal regions of temperate and Arctic seas worldwide, providing ecosystem services valued in the range of billions of dollars annually. Although local evidence suggests that kelp forests are increasingly threatened by a variety of stressors, no comprehensive global analysis of change in kelp abundances currently exists. Here, we build and analyze a global database of kelp time series spanning the past half-century to assess regional and global trends in kelp abundances. We detected a high degree of geographic variation in trends, with regional variability in the direction and magnitude of change far exceeding a small global average decline (instantaneous rate of change = -0.018 y-1). Our analysis identified declines in 38% of ecoregions for which there are data (-0.015 to -0.18 y-1), increases in 27% of ecoregions (0.015 to 0.11 y-1), and no detectable change in 35% of ecoregions. These spatially variable trajectories reflected regional differences in the drivers of change, uncertainty in some regions owing to poor spatial and temporal data coverage, and the dynamic nature of kelp populations. We conclude that although global drivers could be affecting kelp forests at multiple scales, local stressors and regional variation in the effects of these drivers dominate kelp dynamics, in contrast to many other marine and terrestrial foundation species.

Quality Index of Subtidal Macroalgae (QISubMac): A suitable tool for ecological quality status assessment under the scope of the European Water Framework Directive

Despite their representativeness and importance in coastal waters, subtidal rocky bottom habitats have been under-studied. This has resulted in a lack of available indicators for subtidal hard substrate communities. However, a few indicators using subtidal macroalgae have been developed in recent years for the purpose of being implemented into the Water Framework Directive (WFD). Accordingly, a quality index of subtidal macroalgae has been defined as a French assessment tool for subtidal rocky bottom habitats in coastal waters. This approach is based on 14 metrics that consider the depth penetration, composition (sensitive, characteristic and opportunistic) and biodiversity of macroalgae assemblages and complies with WFD requirements. Three ecoregions have been defined to fit with the geographical distribution of macroalgae along the French coastline. As a test, QISubMac was used to assess the water quality of 20 water bodies. The results show that QISubMac may discriminate among different quality classes of water bodies.