Effects of fish predation on Posidonia oceanica amphipod assemblages

Amphipod assemblages that inhabit Posidonia oceanica seagrass meadows are potentially relevant trophic resources for ichthyofauna. However, the effects of fish predation on amphipod assemblages in this system have received little attention. To address this gap in knowledge, experimental manipulations of predation intensity (exclusion and inclusion cages) were conducted at two sites in a Mediterranean marine protected area, where different levels of fish predation were expected to occur. We found that in the absence of predatory fishes (exclusion cages), total amphipod density and biomass were higher than in uncaged areas and partially controlled cages. At the species level, Caprella acanthifera and Iphimedia minuta responded to caging with increased abundance, while in most cases different species did not exhibit differences in density or biomass between treatments. The presence of one enclosed labrid fish predator (inclusion cages) resulted in a lower density and biomass of Aora spinicornis and a lower biomass of Phtisica marina, although total amphipod density and biomass were unchanged. In the inclusion cages, a size-frequency analysis revealed that predators mainly targeted large A. spinicornis and Apherusa chiereghinii individuals. Our results suggest that predation by fish may be an important factor in controlling amphipod abundances and biomasses in P. oceanica meadows. Overall, amphipod community composition was not affected by exclusion or inclusion of fish predators. However, some significant effects at the species level point to more complex interactions between some amphipods and fish

Distribution and density of the benthic microalga <i>Chrysophaeum taylorii</i> Lewis &amp; Bryan from Northern to central-Eastern Sardinian coasts = Distribuzione e densità della microalga bentonica <i>Chrysophaeum taylorii</i> Lewis &amp; Bryan dalle coste nord a quelle centro orientali della Sardegna

In August 2009 the distribution and density of the alien microalga Chrysophaeum taylorii Lewis &amp; Bryan (Pelagophyceae) were investigated on hard benthic substrates in seventeen sites from northern to central-eastern Sardinia, in order to estimate the distribution and abundance of this species in the area

Fish assemblages across the Mediterranean Sea and the effects of protection from fishing = I Popolamenti ittici nel Mediterraneo e gli effetti della protezione dall’impatto della pesca

Several studies have assessed the effectiveness of individual marine protected areas (MPAs) in protecting fish assemblages, but regional assessments of multiple parks are scarce. Here fish surveys using visual census were done in marine parks and fished areas at 31 locations across the Mediterranean Sea. Fish species richness, diversity and biomass (especially of top predators) were higher in MPAs compared to fished areas, and community structure differed significantly between MPAs and fished areas. Results suggest that MPAs are generally effective means to protect and recover fish populations and assemblages

Preliminary data on the genetic variability of the fan mussel <i>Pinna nobilis</i> in the Northern Sardinia = Dati preliminari sulla variabilità genetica del mollusco bivalve <i>Pinna nobilis</i> nella Sardegna settentrionale

The fan mussel Pinna nobilis Linnaeus, 1758 is one of the most endangered Mediterranean bivalve. After a reduction of its distribution as a consequence of anthropic factors, the environmental politics led to a new demographic increasing of individuals in some Mediterranean regions. This work aimed to shed some light on the genetic structure of two new-raised populations in northern Sardinia

Top-down role of fish predators in structuring amphipod community associated to Posidonia oceanica seagrass meadows

Despite the major ecological importance of Posidonia oceanica seagrass meadows in the Mediterranean Sea, little attention has been given to community structuring forces by predators in this ecosystem. To better understand the mechanisms by which fishes affect amphipod community structure associated to P. oceanica beds, experimental manipulations of predation intensity (enclosure and exclusion cages) were set up in the Tavolara-Punta Coda Cavallo Marine Protected Area (Sardinia, NW Mediterranean). In totally protected area, where high abundance of predatory fishes is recorded, we have performed exclusion experiment. Total amphipod abundance increased at the end of the experiment, but diversity and specific composition were unaffected. At the species taxonomic level, significant increase in abundance between treatments appeared only for Caprella acanthifera. In partially protected area, where fish abundance is lower and amphipod abundance higher, individuals of the carnivorous fish Coris julis (Labridae) were enclosed in cages to provide an estimate of the potential for this species to impact on amphipod community. There was a small but measurable effect on amphipod abundance between enclosures and unmanipulated controls. A few dominant amphipod species responded to fish predation by significant decrease in abundance. These results suggest that fish predation may determine the relative abundances in the community of some amphipod species and to some degree, through an untested link with habitat complexity, determine the spatial distribution of amphipod abundance within P. oceanica beds. Moreover, patterns observed at the species level, suggest parallel complex interactions probably mainly related to ecological behaviour of amphipod species

The role of fish predation in the structure of amphipod community associated with Posidonia oceanica seagrass meadows

Despite the major ecological importance of Posidonia oceanica seagrass meadows in the Mediterranean Sea, little attention has been given to community structuring forces by predators in this ecosystem. To better understand the mechanisms by which fishes affect amphipod community structure associated to P. oceanica beds, experimental manipulations of predation intensity (enclosure and exclusion cages) were set up in the Tavolara-Punta Coda Cavallo Marine Protected Area (Sardinia, NW Mediterranean). In totally protected area, where high abundance of predatory fishes is recorded, we have performed exclusion experiment. Total amphipod abundance increased at the end of the experiment, but diversity and specific composition were unaffected. At the species taxonomic level, significant increase in abundance between treatments appeared only for Caprella acanthifera. In partially protected area, where fish abundance is lower and amphipod abundance higher, individuals of the carnivorous fish Coris julis (Labridae) were enclosed in cages to provide an estimate of the potential for this species to impact on amphipod community. There was a small but measurable effect on amphipod abundance between enclosures and unmanipulated controls. A few dominant amphipod species responded to fish predation by significant decrease in abundance. These results suggest that fish predation may determine the relative abundances in the community of some amphipod species and to some degree, through an untested link with habitat complexity, determine the spatial distribution of amphipod abundance within P. oceanica beds. Moreover, patterns observed at the species level, suggest parallel complex interactions probably mainly related to ecological behaviour of amphipod species

The role of gorgonians on the diversity of vagile benthic fauna in Mediterranean rocky habitats

Mediterranean gorgonian forests are threatened by several human activities and climatic anomalies that increase their susceptibility to pathogens and epibionts, potentially leading to mass mortality events. Although these phenomena have been largely documented, the effects of the loss of gorgonian colonies on temperate reef assemblages have been poorly evaluated until now, especially those that concern the vagile fauna. This is the first study comparing vagile fauna assemblages living in Mediterranean rocky bottoms between patches with and without the gorgonians Eunicella cavolini and Paramuricea clavata. Vagile fauna were analysed at the end of a field experiment where patches with and without gorgonians were simulated by transplanting gorgonian branches on to plastic recruitment panels. Panels were deployed for 4&nbsp;months at two depths (24&nbsp;m for E. cavolini and 40&nbsp;m for P. clavata) at two sites in the north-western Mediterranean Sea (Tavolara Island and Portofino Promontory). Overall, 211 taxa belonging to the phyla Platyhelminthes, Nemertea, Mollusca, Brachiopoda, Nematoda, Anellida, Arthropoda and Echinodermata were found. Despite high local heterogeneity and large differences between sites, the abundance of some vagile species was related to the presence of gorgonians. For instance, the shrimp Periclimenes aegylios, absent at Tavolara, was facilitated by the presence of E. cavolini at Portofino, while the tanaid Leptochelia sp. was absent/scarce in the presence of gorgonians at both sites. Overall, at 40&nbsp;m depth, vagile community structures did not differ significantly between experimental patches with and without P. clavata; at 24&nbsp;m depth, vagile assemblages in the presence of E. cavolini were different and less heterogeneous compared to those found in patches without transplanted gorgonians. Ultimately, gorgonians could directly and indirectly affect vagile assemblages

Vibrio splendidus clade associated with a disease affecting Paracentrotus lividus (Lamarck, 1816) in Sardinia (Western Mediterranean)

This work reports for the first time the so-called bald sea urchin disease of the populations of Paracentrotus lividus in Sardinia (Italy). Following the disease occurrence reported by local fishermen of about 35% on the collected specimens for commercial purpose, the phenomenon was evaluated in two areas. Animals displayed external lesions represented by loss of spines and greenish/brownish skeleton patches. Microscopy of exoskeleton and tube feet showed haemocytosis with associated bacteria; gut and intestine histopathology revealed inflammatory lesions of different type and intensity. Microbiological and molecular analysis revealed the presence of the strains belonging to the Vibrio splendidus clade. Due to the important ecological role of Paracentrotus lividus in the Mediterranean Sea, this report represents a wake-up call for the entire basin worth of further insights