Genetic Diversity and Phylogeography of a Turf-Forming Cosmopolitan Marine Alga, Gelidium crinale (Gelidiales, Rhodo-Phyta).

Cosmopolitan species are rare in red algae, which have a low-dispersal capacity unless they are dispersed by human-mediated introductions. Gelidium crinale, a turf-forming red alga, has a widespread distribution in tropical and temperate waters. To decipher the genetic diversity and phylogeography of G. crinale, we analyzed mitochondrial COI-5P and plastid rbcL sequences from collections in the Atlantic, Indian, and Pacific Oceans. Phylogenies of both markers statistically supported the monophyly of G. crinale, with a close relationship to G. americanum and G. calidum from the Western Atlantic. Based on the molecular analysis from these materials, Pterocladia heteroplatos from India is here merged with G. crinale. Phylogeny and TCS networks of COI-5P haplotypes revealed a geographic structure of five groups: (i) Atlantic-Mediterranean, (ii) Ionian, (iii) Asian, (iv) Adriatic-Ionian, and (v) Australasia-India-Tanzania-Easter Island. The most common ancestor of G. crinale likely diverged during the Pleistocene. The Bayesian Skyline Plots suggested the pre-LGM population expansion. Based on geographical structure, lineage-specific private haplotypes, the absence of shared haplotypes between lineages, and AMOVA, we propose that the cosmopolitan distribution of G. crinale has been shaped by Pleistocene relicts. The survival of the turf species under environmental stresses is briefly discussed.

The Status of Posidonia oceanica at Tremiti Islands Marine Protected Area (Adriatic Sea).

Posidonia oceanica meadows are Mediterranean coastal habitats of great conservation importance. This study is focused on a meadow located at Tremiti Islands Marine Protected Area (Adriatic Sea, Italy), which was monitored in 2003, 2015, and 2020 to evaluate its health state over time in relation to coastal human activities, which have been highly affecting this MPA for the last 20 years. To assess any change in the physiognomy of the meadow, rhizome density, percentage coverage, and lower limit progressions and/or regression over time were evaluated by scuba diving, while the distribution and extension of the meadow were assessed through habitat mapping using a side-scan sonar. Moreover, phenological and lepidochronological analyses were performed on the collected rhizomes to assess the leaf area index (LAI, m2m-2) and the rhizome age (lepidochronological years). Our study showed a general deterioration of P. oceanica meadow from 2003 to 2020, with a significant reduction of its absolute and relative rhizome density and LAI at almost all sampling stations, absence of renovation of the meadow, and lower limit regression and overall worsening of the main conservation status indicators. However, appropriate management actions, such as the establishment of mooring buoy fields, supported the improvement of the P. oceanica status at the local scale with a significant increase in density and LAI and the presence of active stolonization processes, suggesting that mitigation actions can play a crucial role in the conservation of this habitat. On the contrary, local anthropogenic impacts, especially anchoring and coastal development, markedly affect the resilience of P. oceanica meadows to global stressors, such as climate change.

Effects of global warming on Mediterranean coral forests.

The effects of global warming have been addressed on coral reefs in tropical areas, while it is still unclear how coral forests are reacting, particularly at temperate latitudes. Here we show how mesophotic coral forests are affected by global warming in the Mediterranean Sea. We highlight how the current warming trend is causing the lowering of the thermocline and it is enhancing mucilaginous blooms. These stressors are facilitating a massive macroalgal epibiosis on living corals, here reported for the first time from different areas in the Western and Central Mediterranean Sea. We provide a focus of this phenomenon at Tremiti Islands Marine Protected Area (Adriatic Sea), were the density of the endemic red gorgonian Paramuricea clavata decreased of up to 47% in 5 years, while up to the 96% of the living corals showed signs of stress and macroalgal epibiosis. Only populations deeper than 60 m depth were not touched by this emerging phenomenon. Spot observations performed at Tuscan Archipelago and Tavolara Marine Protected Area (Tyrrhenian Sea) suggest that this this combination of stressors is likely widespread at basin scale.

Monitoring of the endangered Pinna nobilis Linné, 1758 in the Mar Grande of Taranto (Ionian Sea, Italy).

The present study aimed to improve the knowledge of the bivalve Pinna nobilis L. population distribution in Mar Grande of Taranto (Ionian Sea). Although historical references report the local abundant presence of this endangered species, there is a lack of updated information about its exact distribution. For this purpose, a visual census of P. nobilis was performed by SCUBA diving in the Mar Grande basin from September 2004 to March 2005. Pinnids were found at depths from 3 to 16 m, with a density ranging from 0.1 to 0.7 ind ha(-1). The survey method employed in this study was non-destructive, relatively simple to perform and easily applicable for monitoring studies. Field data were stored in a database and linked with the study area by means of the GIS technology. The results of the present study indicate a tentative of recovery of P. nobilis population in Mar Grande in spite of all the difficulties of a degraded and heavily polluted environment and the damages of illegal fishing methods.