Identifying priority sites for whale shark ship collision management globally.

The expansion of the world's merchant fleet poses a great threat to the ocean's biodiversity. Collisions between ships and marine megafauna can have population-level consequences for vulnerable species. The Endangered whale shark (Rhincodon typus) shares a circumglobal distribution with this expanding fleet and tracking of movement pathways has shown that large vessel collisions pose a major threat to the species. However, it is not yet known whether they are also at risk within aggregation sites, where up to 400 individuals can gather to feed on seasonal bursts of planktonic productivity. These "constellation" sites are of significant ecological, socio-economic and cultural value. Here, through expert elicitation, we gathered information from most known constellation sites for this species across the world (>50 constellations and >13,000 individual whale sharks). We defined the spatial boundaries of these sites and their overlap with shipping traffic. Sites were then ranked based on relative levels of potential collision danger posed to whale sharks in the area. Our results showed that researchers and resource managers may underestimate the threat posed by large ship collisions due to a lack of direct evidence, such as injuries or witness accounts, which are available for other, sub-lethal threat categories. We found that constellations in the Arabian Sea and adjacent waters, the Gulf of Mexico, the Gulf of California, and Southeast and East Asia, had the greatest level of collision threat. We also identified 39 sites where peaks in shipping activity coincided with peak seasonal occurrences of whale sharks, sometimes across several months. Simulated collision mitigation options estimated potentially minimal impact to industry, as most whale shark core habitat areas were small. Given the threat posed by vessel collisions, a coordinated, multi-national approach to mitigation is needed within priority whale shark habitats to ensure collision protection for the species.

Seasonal and plurennial changes of POPs repository in freshwater zooplankton: A 10-year study in the large deep subalpine Lake Maggiore (Italy).

Determining the concentration of POPs (Persistent Organic Pollutants) such as total dichlorodiphenyltrichloroethane (DDTtot) and polychlorinated biphenyls (PCBs) in the zooplankton is essential for evaluating the level of toxicity in the environment and the risk to ecosystem health. The extent to which POPs persist in the environment and affect human health depends on accumulation in the different components of the zooplankton community such as particle feeders and/or predators and their subsequent consumption by fish, which varies seasonally. We analyzed ten-years (2011-2020) of seasonal data on POPs in the crustacean zooplankton community of Lake Maggiore (Italy). The concentration of total DDTs, as sum of all congeners ranged between 23.5 and 156.9 ng/g dry weight, while sumPCB14 ranged from 24.4 and 133.6 ng/g dry weight. We traced particle feeders' vs predatory taxa within the zooplankton community using carbon and nitrogen stable isotopic values. POPs concentration was significantly related to the nitrogen isotopic values. The zooplankton biomass increase in Spring was important, both through this being a period of increased metabolism and activity of planktivorous fish and also as it was the period when the zooplankton repository of POPs was at a maximum. DDTtot stocked in zooplankton ≥450 µm was up to 275 ng/m2, while sumPCB14 was 285 ng/m2 in 2013. A decrease of DDTtot stocked in the zooplankton repository characterized the last five years examined, when mean annual values (14.8-56.9 ng/m2) were less than half those of the previous period (50.7-128.6 ng/m2).

Annual Recurrence of the Critically Endangered Bowmouth Guitarfish (Rhina ancylostomus) in Djibouti Waters.

The bowmouth guitarfish (Rhina ancylostomus) is among the most endangered of marine vertebrates, and evidence of severe declines and localized extinctions has been reported. Yet its life history and ecology suffer from a lack of scientific attention due to the scarcity and unpredictable movements of the species. By collecting opportunistic records from 2015 to 2023 during diving activities, this study describes for the first time the occurrence of a predictable aggregation of R. ancylostomus in the Gulf of Tadjoura (Djibouti). These data provide a key record of this species in the area, whose presence is strongly associated with sandy seabeds and corals at approximately 35 m depth. Based on the opportunistic sightings of R. ancylostomus during diving activity, Ras Eiro and Ras Korali appear to be the currently known core habitats for this species and may serve as breeding or feeding grounds. Overall, our data show that the Gulf of Tadjoura is a globally important conservation hotspot, and therefore its protection should be prioritized.

Physicochemical and biological ageing processes of (micro)plastics in the environment: a multi-tiered study on polyethylene.

Pollution by plastic and microplastic impacts the environment globally. Knowledge on the ageing mechanisms of plastics in natural settings is needed to understand their environmental fate and their reactivity in the ecosystems. Accordingly, the study of ageing processes is gaining focus in the context of the environmental sciences. However, laboratory-based experimental research has typically assessed individual ageing processes, limiting environmental applicability. In this study, we propose a multi-tiered approach to study the environmental ageing of polyethylene plastic fragments focusing on the combined assessment of physical and biological processes in sequence. The ageing protocol included ultraviolet irradiation in air and in a range of water solutions, followed by a biofouling test. Changes in surface characteristics were assessed by Fourier transform infrared spectroscopy, scanning electron microscopy, and water contact angle. UV radiation both in air and water caused a significant increase in the density of oxidized groups (i.e., hydroxyl and carbonyl) on the plastic surface, whereby water solution chemistry influenced the process both by modulating surface oxidation and morphology. Biofouling, too, was a strong determinant of surface alterations, regardless of the prior irradiation treatments. All biofouled samples present (i) specific infrared bands of new surface functional groups (e.g., amides and polysaccharides), (ii) a further increase in hydroxyl and carbonyl groups, (iii) the diffuse presence of algal biofilm on the plastic surface, and (iv) a significant decrease in surface hydrophobicity. This suggests that biological-driven alterations are not affected by the level of physicochemical ageing and may represent, in real settings, the main driver of alteration of both weathered and pristine plastics. This work highlights the potentially pivotal role of biofouling as the main process of plastic ageing, providing useful technical insights for future experimental works. These results also confirm that a multi-tiered laboratory approach permits a realistic simulation of plastic environmental ageing in controlled conditions.

Freshwater Lacustrine Zooplankton and Microplastic: An Issue to Be Still Explored.

Lakes are essentially interlinked to humans as they provide water for drinking, agriculture, industrial and domestic purposes. The upsurge of plastic usage, its persistence, and potential detrimental effects on organisms cause impacts on the trophic food web of freshwater ecosystems; this issue, however, still needs to be explored. Zooplankton worldwide is commonly studied as an indicator of environmental risk in aquatic ecosystems for several pollutants. The aim of the review is to link the existing knowledge of microplastic pollution in zooplankton to assess the potential risks linked to these organisms which are at the first level of the lacustrine trophic web. A database search was conducted through the main databases to gather the relevant literature over the course of time. The sensitivity of zooplankton organisms is evident from laboratory studies, whereas several knowledge gaps exist in the understanding of mechanisms causing toxicity. This review also highlights insufficient data on field studies hampering the understanding of the pollution extent in lakes, as well as unclear trends on ecosystem-level cascading effects of microplastics (MPs) and mechanisms of toxicity (especially in combination with other pollutants). Therefore, this review provides insight into understanding the overlooked issues of microplastic in lake ecosystems to gain an accurate ecological risk assessment.

Playing "hide and seek" with the Mediterranean monk seal: a citizen science dataset reveals its distribution from molecular traces (eDNA).

Animal conservation relies on assessing the distribution and habitat use of species, but for endangered/elusive animals this can prove difficult. The Monk Seal, Monachus monachus, is one of the world's most endangered species of pinniped, and the only one endemic to the Mediterranean Sea. During recent decades, direct observations have been few and scattered, making it difficult to determine its distribution away from the Aegean Sea (core distribution area of the post-decline relict population). This study relies on environmental DNA (eDNA) analysis to detect the presence of the Monk Seal in 135 samples collected in 120 locations of the central/western Mediterranean Sea, spanning about 1500 km longitudinally and 1000 km latitudinally. A recently described species-specific qPCR assay was used on marine-water samples, mostly collected during 2021 by a Citizen Science (CS) project. Positive detections occurred throughout the longitudinal range, including the westernmost surveyed area (Balearic archipelago). The distribution of the positive detections indicated six "hotspots", mostly overlapping with historical Monk Seal sites, suggesting that habitat-specific characteristics play a fundamental role. We applied single-season occupancy models to correct for detection probability and to assess the importance of site-specific characteristics. The distance from small islets and protected (or access-restricted) areas was correlated negatively with the detection probability. This novel molecular approach, applied here for the first time in an extensive CS study, proved its potential as a tool for monitoring the distribution of this endangered/elusive species.

Selective organomercury determination by ICP-MS made easy.

A fast and cost-effective procedure based on Inductively Coupled Plasma - Mass Spectrometry (ICP-MS) for the selective determination of methylmercury (MeHg) is proposed and validated for fish tissue analysis. Selectivity for MeHg is achieved by simply inserting a strong anion exchange resin to block inorganic mercury as negatively charged chloride species, leaving MeHg unretained. The procedure features a 15 min extraction time followed by a 100 s analysis time achieving a limit of detection of 1.6 µg kg-1 on solid samples. The effect of the solution composition and inorganic mercury concentration were extensively studied to fully assess the selectivity of the procedure: Hg(II):MeHg ratios up to 50 are tolerated and cause systematic errors lower than 15%. The entire procedure was successfully validated by standard reference material from the marine food web, namely fish muscle and liver plus zooplankton. The method was finally applied to the detection of MeHg in the marine trophic web of Djibouti (Gulf of Aden): a trophic magnification factor of 13.5 proved the high risk associated with the biomagnification of methylmercury.

High-throughput, Multi-batch System for the Efficient Microwave Digestion of Biological Samples.

In this paper, we proposed a high-throughput microwave digestion system based on multi-batch reactors (three quartz test tubes inside commercial PTFE vessels). This original configuration was validated by ICP-MS analysis of several elements in biological certified reference materials (fish tissues and plankton). The proposed system was proved to be free from contamination showing very low LODs. The improved hardware configuration is therefore highly beneficial for the detection of trace elements in microsamples from the marine food web.