Spatial patterns and temporal variability of seagrass connectivity in the Mediterranean Sea

Abstract

Aim: The endemic seagrass Posidonia oceanica is a key component of the coastal seascapes of the Mediterranean Sea, where it provides crucial ecosystem services and promotes the assembly of diverse ecological communities. Although protection policies exist, P. oceanica meadows have been steadily declining in the recent past because of human activities and climate change. Here, we quantitatively analyse basin-wide patterns of seagrass connectivity over a 30-year-long period and identify connectivity hotspots that may serve as priority targets for conservation actions. Location: Mediterranean Sea. Time period: 1987-2016. Major taxa studied: The seagrass P. oceanica. Methods: A biophysical Lagrangian approach is used to simulate dispersal of seagrass fruits operated by marine currents. Connectivity metrics (self-retention, indegree and outdegree) are evaluated on top of Lagrangian simulations to identify the most ecologically connected areas. Time series of local connectivity scores are analysed to study temporal variability and possibly detect trends at different spatial scales. Results: Spatio-temporal variability is an important component of seagrass connectivity in the Mediterranean. Connectivity hotspots are unevenly distributed in all of its four main sub-basins, and along both European and African coastlines. Although statistically significant local trends in connectivity are generally quite infrequent across the whole basin, they appear to be relatively more prevalent in connectivity hotspots. The interannual variability of average connectivity scores seems to be at least partially linked to meteorological fluctuations.Main conclusions: The present study represents a step forward in the application of a quantitative, scalable and replicable methodological framework for the prioritization

A coupled model for the linked dynamics of marine pollution by microplastics and plastic-related organic pollutants

“…5 ), but also across entire sub-basins at regional scales (Fig. 5; see also Mari et al;2020; for Mediterranean connectivity). In particular, the likelihood of microplastics to serve as long-range vectors of PROPs seems quite dependent on their source of release.…”

The Genetic Component of Seagrass Restoration: What We Know and the Way Forwards

“…Moreover, despite the apparent spatial uniformity of the sea, marine habitats are characterized by clear discontinuities, and the presence of dispersal barriers may create a genetic breakdown in marine populations due to local selective pressures [55]. Nevertheless, dispersal vehicles such as buoyant fruits and vegetative propagules can travel long-distance transported by marine currents (potential connectivity), and new genotypes or allelic variants can establish in disjoint populations (realized connectivity [56][57][58]). This implies that even if sexual reproduction occurs at a low rate, passive transport of sexual propagules can play an important role in maintaining population connectivity and in the colonization of new habitats [59].…”

“…In the last case, the integration of genetic diversity, connectivity, and environmental data could reveal the reasons behind the isolation of the target area and the possible way of restoring dispersal and connectivity networks ( [106]). Recently, Mari and colleagues [58] built maps of potential connectivity for P. oceanica, modeling the dispersal and potential exchange of propagules between sites evaluating environmental features. The resulting patterns could be integrated with genetic data of target populations useful for choosing potential donor populations.…”

“…Future efforts on making complete maps (or georeferenced databases) as guidelines to restoration should also include information regarding intraspecific differences in genetic diversity, e.g., among different depths of the same population as seen in the case of the seagrass Z. marina [115] and P. oceanica [117,118], which can have potential implications in the collection of plant material. The integration of species distribution (a [119]), environmental data (b [58]), anthropogenic impacts (c [120]), with potential (d [58]) and realized connectivity maps (e [57]) and genetic diversity analysis (f [121]) could be combined to develop multilayers maps for the identifications of donor and target sites in seagrass restoration (see text for more detail). The figure was modified from the studies cited above.…”

“…Examples of models and distributions maps and genetic data from seagrass' studies of the Mediterranean Sea. The integration of species distribution (a[119]), environmental data (b[58]), anthropogenic impacts (c[120]), with potential (d[58]) and realized connectivity maps (e[57]) and genetic diversity analysis (f[121]) could be combined to develop multilayers maps for the identifications of donor and target sites in seagrass restoration (see text for more detail). The figure was modified from the studies cited above.…”