Perfluoroalkyl substances (PFAS) occurrence, concentrations and spatial distribution along the French Mediterranean coast and lagoons, based on active biomonitoring.

Tracking PFAS in ecosystems is challenging. In this context, monitoring programs are crucial to fill data gaps, especially in marine environments, which are the ultimate outlets for these forever chemicals. The 2021 chemical contamination monitoring campaign along the French Mediterranean coast established a baseline for PFAS concentrations in mussels, with 90 % of measurements below quantification limits. When detected, long-chain PFCA's were predominant. Spatial distribution patterns suggested continuous PFAS inputs and complex dynamics, shaped by the influence of large watersheds and rivers (Rhône, Aude, Huveaune). Lapeyrade shallow lagoon stood out as the most contaminated site. Similar PFAS profiles in connected sites implied shared sources but raised questions about accumulation processes in mussels. While certain sites had evident sources (e.g., military airbase for Palo lagoon), others remained uncertain (e.g., Toulon bay). Coastal stations (Banyuls, Cap Agde, Brégançon, Pampelonne) showed PFAS contamination without clear onshore sources, possibly due to insufficient transportation process understanding.

C and N stable isotopes enlighten the trophic behaviour of the dugong (Dugong dugon).

The dugong (Dugong dugon), a large marine mammal herbivore of the Indo-Pacific, is vulnerable to extinction at a global scale due to a combination of human-related threats including habitat degradation. The species forages on seagrass habitats (marine phanerogams) and plays a key role in the functioning and sensitivity of these declining coastal ecosystems. The trophic behaviour and plasticity of dugong populations in response to extrinsic and intrinsic factors are therefore crucial features to both dugong and seagrass conservation. Yet, this knowledge remains limited to few visual observations and analyses of mouth, stomach or faecal contents of stranded individuals. We take advantage of a long-term monitoring of stranded individuals from the endangered New Caledonian population to depict features of dugongs' trophic ecology from Carbon and Nitrogen stable isotopes. A total of 59 dugong skin samples were used to portrait the stable isotope niche of dugongs according to their sex and maturity. In light of previous work conducted in New Caledonia, a subset of these samples was used to model the trophic mix of dugong males and females. Our stable isotope mixing models used C and N isotope values of 10 taxa bbelonging to five divisions of metazoans, plants, and chromists. Our results represent the first estimate of the species dietary niche in the isotopic space. They suggest that the diet of dugong calves overlaps more with that of adult females (δ13C: - 6.38 ± 1.13 ‰; δ15N: 2.49 ± 1.10 ‰) than males (δ13C: - 5.92 ± 1.10 ‰; δ15N: 3.69 ± 1.28 ‰). Further, we highlight differences in the expected trophic mix of dugong adult males and females. From these, we formulate a sex-specific foraging behaviour hypothesis in dugongs, whereby lactating females could forage over smaller spatial ranges but more diverse food sources thanmales. The study emphasizes the importance of long-term stranding monitoring programs to study the ecology of marine mammals.. Finally, it depicts an ecological feature that may contribute to the sensitivity of vulnerable dugongs to ongoing changes on tropical coastal ecosystems.

The French Mussel Watch: More than two decades of chemical contamination survey in Mediterranean coastal waters.

Active biomonitoring of chemical contamination (e.g., Cd, Hg, Pb, DDT, PCB, PAH) in French Mediterranean coastal waters has been performed for more than two decades. This study aimed at presenting the current contamination in 2021 and the temporal evolution of concentrations from 2000. Based on a relative spatial comparison, low concentrations were measured in 2021 at most sites (>83 %). Also, several stations with moderate to high levels were highlighted in the vicinity of major urban industrial centers (e.g., Marseille, Toulon) and near river mouths (e.g., Rhône, Var). Over the last 20 years, no major trend was revealed, mostly, especially for the relative high-level sites. This likely constant contamination over time, plus slight increases of metallic elements at a few sites, still raise questions on the efforts that remain to be made. The decreasing trends of organic compounds, in particular PAH, provide evidence of the efficiency of some management actions.

Isotopic discrimination in helminths infecting coral reef fishes depends on parasite group, habitat within host, and host stable isotope value.

Stable isotopes of carbon and nitrogen characterize trophic relationships in predator-prey relationships, with clear differences between consumer and diet (discrimination factor Δ13C and Δ15N). However, parasite-host isotopic relationships remain unclear, with Δ13C and Δ15N remaining incompletely characterized, especially for helminths. In this study, we used stable isotopes to determine discrimination factors for 13 parasite-host pairings of helminths in coral reef fish. Differences in Δ15N values grouped according to parasite groups and habitat within the host with positive Δ15N values observed for trematodes and nematodes from the digestive tract and variable Δ15N values observed for cestodes and nematodes from the general cavity. Furthermore, Δ13C values showed more complex patterns with no effect of parasite group or habitat within host. A negative relationship was observed between Δ15N and host δ15N values among different host-parasite pairings as well as within 7 out of the 13 pairings, indicating that host metabolic processing affects host-parasite discrimination values. In contrast, no relationships were observed for Δ13C values. Our results indicate that parasite group, habitat within host, and host stable isotope value drive Δ15N of helminths in coral reef fish while their effect on Δ13C is more idiosyncratic. These results call for use of taxon- or species-specific and scaled framework for bulk stable isotopes in the trophic ecology of parasites.

Differential uses of coral reef habitats by a poorly-known cryptic fish predator.

This study used otolith microchemistry to evaluate whether the moray eel Gymnothorax chilospilus uses different habitats throughout its life (mainly juvenile and adult phases). Of the most informative trace elements within otoliths (the twelve isotopes 23 Na, 25 Mg, 43 Ca, 55 Mn, 59 Co, 60 Ni, 63 Cu, 66 Zn, 86 Sr, 111 Cd, 138 Ba and 208 Pb) only three ratios of Ca (Na:Ca, Sr:Ca and Ba:Ca) were informative and therefore used in a multivariate regression-tree analysis. Using a multivariate partitioning, three main phases were described from profiles, including the larval life phase (leptocephali), the intermediate phase (longest section between the larval life phase and the terminal phase) and the terminal phase (final section i.e., the most recent months preceding the death of fish). According to concentrations of the three ratios to Ca, G. chilospilus can be separated into three groups during their larval life stage (very different in Sr and Na), four groups during the intermediate phase (few differences in Sr and Na) and three groups during the terminal phase (differences in Sr), illustrating that G. chilospilus inhabit different habitats during these three phases. Our results showed that the leptocephali encountered different oceanic water masses with fluctuating Sr:Ca ratios during the early larval phase. During the intermediate phase (main part of their life-span), they lived in lagoonal waters such as fringing reefs or reef flats of lagoonal islets, characterized by a lower Sr:Ca ratio. During the latter part of their life, approximately one third of G. chilospilus encountered more oceanic waters close to or at barrier reefs, suggesting possible movements of these fish along a coast-to-ocean gradient.

Tracking trace elements into complex coral reef trophic networks.

The integration, accumulation and transfer of trace elements across the main tropic levels of many food webs are poorly documented. This is notably the case for the complex trophic webs of coral reef ecosystems. Our results show that in the south-west lagoon of New Caledonia both abiotic (i.e. sediments) and biotic (i.e. primary producers, consumers and predators) compartments are contaminated by trace elements. However, our analyses revealed different contamination patterns from the sources of organic matter to the predators. The trophic levels involved in the sedimentary benthic food web (S-BFW, based on the sedimentary organic matter) and to a lesser extent in the reef benthic food web (R-BFW, based on algal turf) were mainly contaminated by trace elements that originate from mining activities like Ni and associated trace elements (Co, Cr, Fe, and Mn). Trace elements linked to agro-industrial (As, Hg, and Zn) and urban (Ag, Cd, Cu, Pb, Se, and V) activities were also integrated into the S-BFW, but preferentially into the R-BFW, and to a lesser extent into the detrital benthic food web (D-BFW, supplied by sea-grass plants). Most of the trace elements were biodiminished with increasing trophic levels along food webs. However, a marked biomagnification was observed for Hg, and suspected for Se and Zn. These results provide important baseline information to better interpret trace element contamination in the different organisms and trophic levels in a highly diversified coral reef lagoon.

Occurrence of Anisakis (Nematoda: Anisakidae) larvae in unusual hosts in Southern hemisphere.

Nematodes belonging to the genus Anisakis are important parasites due to their abundance in seafood and health impacts on humans. In the present study Anisakis larvae were found in a number of uncommon hosts including the Grey petrel, Procellaria cinerea, the Little penguin, Eudyptula minor, Blue-lipped sea krait, Laticauda laticaudata and Spinner shark, Carcharhinus brevipinna. Morphological examination showed nematodes in these animals are Anisakis larval type I. Genetic characterisation suggested that the larva from one Grey petrel was Anisakis berlandi, whereas the other larvae from the second Grey petrel and from the little penguin were Anisakis pegreffii. A number of larvae found in Blue-lipped sea krait and Spinner shark were identified as Anisakis typica. This is the first report of infective stage of Anisakis larvae parasitising hosts other than teleost fish. Understanding of the extent of infection and the pathogenicity of anisakid nematodes in hosts found in the present study is important in the conservation studies and management plans of these hosts.

Major Sources of Organic Matter in a Complex Coral Reef Lagoon: Identification from Isotopic Signatures (δ13C and δ15N).

A wide investigation was conducted into the main organic matter (OM) sources supporting coral reef trophic networks in the lagoon of New Caledonia. Sampling included different reef locations (fringing, intermediate and barrier reef), different associated ecosystems (mangroves and seagrass beds) and rivers. In total, 30 taxa of macrophytes, plus pools of particulate and sedimentary OM (POM and SOM) were sampled. Isotopic signatures (C and N) of each OM sources was characterized and the composition of OM pools assessed. In addition, spatial and seasonal variations of reef OM sources were examined. Mangroves isotopic signatures were the most C-depleted (-30.17 ± 0.41 ‰) and seagrass signatures were the most C-enriched (-4.36 ± 0.72 ‰). Trichodesmium spp. had the most N-depleted signatures (-0.14 ± 0.03 ‰) whereas mangroves had the most N-enriched signatures (6.47 ± 0.41 ‰). The composition of POM and SOM varied along a coast-to-barrier reef gradient. River POM and marine POM contributed equally to coastal POM, whereas marine POM represented 90% of the POM on barrier reefs, compared to 10% river POM. The relative importance of river POM, marine POM and mangroves to the SOM pool decreased from fringing to barrier reefs. Conversely, the relative importance of seagrass, Trichodesmium spp. and macroalgae increased along this gradient. Overall, spatial fluctuations in POM and SOM were much greater than in primary producers. Seasonal fluctuations were low for all OM sources. Our results demonstrated that a large variety of OM sources sustain coral reefs, varying in their origin, composition and role and suggest that δ13C was a more useful fingerprint than δ15N in this endeavour. This study also suggested substantial OM exchanges and trophic connections between coral reefs and surrounding ecosystems. Finally, the importance of accounting for environmental characteristics at small temporal and spatial scales before drawing general patterns is highlighted.

Anguilliform fish reveal large scale contamination by mine trace elements in the coral reefs of New Caledonia.

Due to intensive mining activity, increasing urbanization and industrialization, vast amounts of contaminants are discharged into the lagoon of New Caledonia, one of the largest continuous coral reef systems and a major biodiversity hotspot. The levels of 11 trace element concentrations were examined in the muscles of predator fish in the south-western lagoon (moray eels and congers). These species are sedentary, widespread, abundant, and they are easily collected using a sea snake sampling technique. We found the highest mean and maximal concentrations of different trace elements ever found in coral fish, notably regarding trace elements typical from mining activity (e.g., mean values for Cr and Ni, respectively: 5.53 ± 6.99 µg g(-1) [max, 35.7 µg g(-1)] and 2.84 ± 3.38 µg g(-1) [max, 18.0 µg g(-1)]). Results show that important trace element contamination extends throughout the lagoon to the barrier reef, following a concentration gradient from the oldest nickel factory (Nouméa).

Variations of natremia in sea kraits (Laticauda spp.) kept in seawater and fresh water.

Marine tetrapods evolved specific excretory structures (e.g. salt glands) that maintain salt concentrations within a narrow range of variation. However, recent investigations showed that in some lineages (sea snakes), individuals dehydrate in seawater and cannot equilibrate their hydromineral balance without access to fresh water. How these marine species cope with salt gain is therefore puzzling. We sampled two species of amphibious sea kraits (Laticauda saintgironsi and L. laticaudata) in the field. We also experimentally investigated patterns of salt regulation, specifically variations in natremia (plasma sodium) and body mass (net water flow), in individuals transferred first to fresh water and then to seawater. Our results show that free-ranging sea kraits display hypernatremia (up to 205mmol·l(-1)). Experimental data showed that natremia markedly decreased in snakes exposed to fresh water and increased when they were transferred to saltwater, thereby demonstrating a marked flexibility in their relation to environmental conditions. A literature survey indicated that all free-ranging marine snake species usually display hypernatremia despite having functional salt glands. Overall, sea snakes exhibit a marked tolerance to salt load compared to other marine tetrapods and apparently trigger substantial salt excretion only once natremia exceeds a high threshold. We hypothesise that this high tolerance significantly decreases energetic costs linked to salt gland functioning.

Coral assemblages in Tonga: spatial patterns, replenishment capacities, and implications for conservation strategies.

Coral reefs in Tonga have been confronted by multiple threats of various origins, including large-scale disturbances and human-induced stressors. These reef communities have been poorly studied, and efficient conservation actions are urgently needed. The aim of this study was to: (1) examine the spatial distribution of coral assemblages in the lagoon of Tongatapu; (2) determine the degree to which spatial heterogeneity of adult corals is influenced by recruitment processes; and (3) examine the implications of these results in terms of conservation actions. We recorded a total of 37 adult and 28 juvenile coral genera, a mean density of 11.6 adult and 5.5 juvenile colonies m(-2), and a dominance of Montipora, Acropora, and Porites. For seven of the 10 dominant genera, spatial patterns of adults were linked to the short-term recruitment pattern history. Despite a reduced diversity and abundance of adult corals in some areas, the lagoon of Tongatapu retains the potential for replenishment through recruitment of young corals. Consequently, we suggest that conservation actions should focus on reducing factors causing coral mortality and maintain suitable conditions for the establishment and growth of juvenile corals, thus increasing the probability that they will reach maturity and participate to the maintenance of local populations. Rather than establishing a large marine protected area, which will almost certainly suffer from a lack of control and poor enforcement, alternative conservation measures could be successfully implemented through the establishment of several small village-based marine reserves, as has been undertaken in other South Pacific islands with promising results.

A quick and simple method, usable in the field, for collecting parasites in suitable condition for both morphological and molecular studies.

Many methods have been proposed for collecting and fixing parasites, but most were written before the molecular age, and were intended to be practised by experienced parasitologists in well-equipped laboratories. We describe here a very simple method, illustrated by photographs, for collecting helminths from the digestive tract of vertebrates. It only requires a few plastic vials, some ethanol and a means to heat water. Basically, the method consists of: (a) the extraction of all organs from the abdominal cavity; (b) opening the digestive system longitudinally; (c) agitate gut and contents in a saline solution (i.e. ca. 9% NaCl or 1/4 sea water in tap water); (d) decant in saline as many times as needed to clean contents; (e) immediately fix parasites in near-boiling saline; (f) discard saline and keep specimens in 95% ethanol. Additional information is given for collecting parasites from fish gills with a similar process. The method will collect most helminths (digeneans, larval cestodes, nematodes, acanthocephalans) from the digestive tract, and monogeneans and isopod and copepod crustaceans from fish gills. The specimens will be suitable for both morphological study and DNA sequencing. The method is simple, fast, inexpensive and can be used by untrained personnel, even in the field without electricity and without a binocular microscope. It can also be used by trained parasitologists who need to expedite treatment of abundant samples.

Three new species, Lamellodiscus tubulicornis n. sp., L. magnicornis n. sp. and L. parvicornis n. sp. (Monogenea: Diplectanidae) from Gymnocranius spp. (Lethrinidae: Monotaxinae) off New Caledonia, with the proposal of the new morphological group 'tubulicornis' within Lamellodiscus Johnston & Tiegs, 1922.

Three new species of Lamellodiscus are described from four (including two undescribed) species of Gymnocranius off New Caledonia, South Pacific. All three species have a similar body anatomy and morphology of the haptoral hard parts and are distinguished on the basis of the male copulatory organ (MCO). Lamellodiscus tubulicornis n. sp. (type-host: G. grandoculis; other host: Gymnocranius sp. B) has an MCO with a tube and horn; L. magnicornis n. sp. (type-host: G. grandoculis; other hosts: G. euanus, Gymnocranius sp. A and Gymnocranius sp. B) has an MCO with a long horn and a membrane; L. parvicornis n. sp. (type-host: G. euanus; other hosts: G. grandoculis and Gymnocranius sp. B) has an MCO with a small horn and a membrane. Lamellodiscus epsilon Yamaguti, 1968 is redescribed based on the type-specimens (from Monotaxis grandoculis off Hawaii). Lamellodiscus sp. is recorded from Gnathodentex aureolineatus off New Caledonia. All these five species have lamellodiscs that exhibit a unique characteristic: the second lamella forms an almost closed circle, in contrast to all other described species of Lamellodiscus in which the second lamella has the form of one or two crescents. Lamellodiscus spp. are usually classified in two groups, the 'ignoratus' and 'elegans' groups, according to the structure of the lamellodisc; we propose a new 'tubulicornis' group for these five species. In addition to their lamellodisc structure, species of the tubulicornis group are also characterised by their egg (elongate in contrast to tetrahedral in the two other groups) and their hosts (monotaxine lethrinids as opposed to mainly sparids). The generic diagnosis of Lamellodiscus given by Amine & Euzet (2005) is amended to include species with elongate eggs.