Cohabiting with litter: Fish and benthic assemblages in coastal habitats of a heavily urbanized area

Not only in the crowd: Benthic litter characterization in a low population density area still reveals widespread pollution and local malpractices

Various anthropogenic activities affect marine coastal habitats, leading to heavy litter pollution. However, whilst high litter concentrations are nowadays common in the proximity of metropolises, few studies investigated the magnitude of this phenomenon around coastal villages and small towns. We hereby characterized the benthic litter occurring in the trawlable grounds of the Gulf of Policastro (Tyrrhenian Sea, central-western Mediterranean), a low population density area that becomes a popular tourist destination during summer. We furthermore tested differences between two depths (∼100-200 and ∼500-600 m) and the impact of tourism on the shallower waters. The area was characterized by a litter abundance of 651.12 ± 130.61 item/km2, with plastic being almost totalitarian (93%). The shallower waters hosted two-thirds of the litter found. Almost all (∼95%) the litter items had a land-based origin, while the sea-based litter was mostly found at higher depths. About 14% of the litter was found to be fouled, with the development of litter-associated communities that somehow mimic the natural ones living on hard substrates. The higher litter presence noticed during the touristic peak (July-August) suggests that tourism is an important source of local litter, although it contributed to the local accumulation in a synergic way with other factors. The majority of the litter items presumably originated from the nearby coastline, while the deeper waters were or are used as a dumping site by the local trawling fleet. The discovery of such a critical waste accumulation and management in a somehow remote area contributes to widen the perspectives on the presence of benthic litter mostly in territories characterized by wide anthropization. Moreover, it confirms that appropriate local policies and communication plans are urged even at a regional level to stimulate citizen consciousness and mitigate the ever growing litter pollution.

Rocky reef incursions: challenges faced by reef fishes in a Brazilian Hope Spot region

Biodiversity conservation has been a critical challenge faced by environmental managers worldwide. From 2020 to 2022, a total of 576 underwater visual censuses focused on reef fishes, marine litter (ML), and non-native species were performed in the newest Brazilian Hope Spot, to understand the distribution, characteristics, and effects of ML and Tubastraea spp., on the reef fish community. Plastic was the main category recorded (34.54 %), followed by Metal and Line (mostly fishing gear within a Marine Protected Area). Tubastraea spp. was widely distributed, especially between 10-20 meters deep. The t-test analysis showed that fish abundance and richness were significantly higher at low Tubastraea cover areas. Our efforts present the baseline of ML (mean 1.92 ± 1.5 items/100 m2) and non-native species occurrence (15) and distribution (including three new records) showing their negative impacts on rocky reef ecosystems and provide managers support in the elaboration of marine conservation strategies.

Parasites and prey of the nursehound shark Scyliorhinus stellaris (Linnaeus, 1758): Insights into hidden trophic web interactions in the Mediterranean Sea

The metazoan parasite community and the stomach contents of the nursehound shark Scyliorhinus stellaris from the Gulf of Naples (central Mediterranean Sea) were studied. The nursehound shark harboured a poor parasite community composed of a species of gill monogenean (Hexabothrium appendiculatum) and three intestinal cestode taxa (Acanthobothrium coronatum and two unidentified species of the genera Yamaguticestus and Scyphophyllidium), all represented by adult stages. Hosts were mostly parasitized by individuals of A. coronatum, which was the most abundant species and contributed to almost 80% of the total number of parasites found. Conversely, other trophically transmitted parasites (i.e., Yamaguticestus sp. and Scyphophyllidium sp.) showed low prevalence and abundance. The parasite infracommunity was poor, showing low values of species richness, total mean abundance, and diversity indices. Overall, 52 prey items belonging to 13 taxa were identified in the stomach contents. Cephalopods were the most important prey items (represented by nine taxa) and the most diverse and abundant group. In the multivariate space provided by a principal component of mixed data (PCAmix), nursehound sharks distributed along two main axes, related to individual traits (first axis) and stomach contents (including empty ones, second axis). A logistic regression based on the first two axes of the PCAmix showed a significant influence of host individual traits and, to a lesser extent, of stomach contents, regarding the probability of being infected by A. coronatum. Alongside specific traits already associated with parasites transmission, our results highlight the importance of cephalopods in transferring cestode infections through trophic web interactions in the top-predator nursehound shark.

Benthic litter in the continental slope of the Gulf of Naples (central-western Mediterranean Sea) hosts limited fouling communities but facilitates molluscan spawning

Seafloor pollution by benthic litter is an emerging phenomenon, although debris colonization by biota remains largely unexplored. We characterized the litter of the continental slope (~400-600 m) of the Gulf of Naples (Mediterranean) and investigated its fouling biota through integrative taxonomic approaches. Plastic pieces (82 %) with land-based origin (96 %) and limited sizes (10-20 cm) were the items most commonly encountered, suggesting a transfer to deep waters through floating and sinking. The majority of the items were not fouled, and the debris hosted an impoverished biota, leading to hypothesize that benthic litter supports wide communities only in shallow waters. Higher colonization rates were observed for gastropod and cephalopod eggs with no preference for materials and sizes, suggesting that even small pieces of soft plastic provide a spawning habitat for molluscs and affect species' connectivity in the deep-sea ecosystem. Holistic approaches are necessary to evaluate interactions between litter and biota.

Drivers of parasite communities in three sympatric benthic sharks in the Gulf of Naples (central Mediterranean Sea)

Sharks play a key role in the functioning of marine ecosystems and maintenance of trophic web balance, including life cycles of parasites co-occurring in their habitats. We investigated the structure of parasite communities of three sympatric shark species (Etmopterus spinax, Galeus melastomus, and Scyliorhinus canicula) and explored both the influence of host features in shaping the communities and their role as biological indicators of environment stability in the Gulf of Naples (central Mediterranean Sea), a geographical area characterized by strong anthropic pressure. Parasites found were all trophic transmitted helminths with a complex life cycle, except Lernaeopoda galei, that is a ecto-parasite copepod. Communities were all similarly impoverished with 4–5 component species and low values of species richness and diversity. Higher abundance of cestode larvae of the genus Grillotia was found in G. melastomus, although their dominance in all host species suggests that the three sharks have a similar role as intermediate/paratenic hosts in local food webs. Similarly, high abundance of Grillotia larvae could also suggest the occurrence of high abundance of largest top predators in the area. Host morphological (fork length in S. canicula and G. melastomus and body condition index in G. melastomus) and physiological (sex and gonadosomatic and hepatosomatic indices in S. canicula) variables were differently correlated to parasite community structures depending by host species. Potential reasons for the present impoverished parasite communities are discussed.

Diversity Loss in Coralligenous Structuring Species Impacted by Fishing Gear and Marine Litter

Coralligenous structuring species (CSS) form a group of marine megabenthic species with an engineering capacity. Since they are highly vulnerable to anthropogenic activities, they have been selected for the Marine Strategy Framework Directive (MSFD) monitoring programs. The pressure and impact of fishing gear and marine litter on these species were evaluated through the image analysis of 54 remotely operated vehicle (ROV) routes along the Campania coasts (Tyrrhenian Sea, Italy). CSS density was calculated as the number of colonies/100 m2. Anthropogenic pressure was estimated as the frequency of frames showing longline, nets, other gear, plastic objects, metal objects, and other litter; while the impact was expressed as the frequency showing necrosis/epibiosis, broken/upturned and covered/entangled colonies. Cnidaria dominate in the Napoli, Campanella and Capri areas, while Bryozoa dominate in Cilento N and Cilento S areas. Campanella and Capri appeared to be the least heterogeneous despite their higher CSS densities, which was possibly related to the dominance of a few species. These areas were the most affected by showing the highest numbers of fishing gear (longlines) and marine litter (metal objects) recorded, amongst which longlines are the most abundant. In addition, these fishing areas are either close to a large urban center or located along popular touristic routes. In all the areas, colonies with necrosis/epibiosis (CNE) impact are present with low-moderate values, while the category gears covering/entangling (GCE) impact prevails in the Campanella and Capri areas, and this is strictly connected to the high presence of fishing gear.