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Governing marine environments is a highly complex and challenging enterprise. This applies particularly to the heavily exploited Baltic Sea for which despite extensive governance arrangements and a substantial scientific knowledge base, it is unlikely that the policy objective of ‘good environmental status’ is reached. Based on a review of governance arrangements linked to five large-scale environmental issues (eutrophication, overfishing, invasive alien species, chemical pollution and oil spills from shipping), this chapter aims to identify pathways and concrete ideas for institutional reform that may improve goal fulfilment. The results show that governance challenges differ substantially between environmental issues, implying a need for case-specific management reforms. For example, coping with extreme uncertainty is a key challenge in the chemical pollution case, whereas it seems more pertinent in the eutrophication case to address the complexity of nutrient pollution sources by adapting objectives and measures amongst sectoral policies to be in line with environmental ones. Furthermore, cross-case comparisons reveal a set of common vital functions (i.e. coordination, integration, interdisciplinarity, precaution, deliberation, communication and adaptability) that are needed in order to facilitate effective and efficient environmental governance in the long term. To promote these functions in Baltic Sea environmental governance, the chapter suggests pathways and institutional reforms aimed at improving multilevel and multisectoral integration, science-policy interactions and stakeholder participation. To further develop these ideas, it is proposed amongst other things that priority is given to setting up an international ‘Baltic Sea Policy Review Mechanism’, formed by cross-body and cross-stakeholder participation.

In 1684, the Venetian Republic joined the Empire, Poland and the Papacy in driving back the Ottoman forces that had just suffered a crushing defeat under the walls of Vienna. In a few campaigns, the Serenissima’s troops succeeded in securing the entire Peloponnese (the Morea), through the occupation of the main strongholds. The treaty of Karlowitz of 1699 ratified this conquest but, fifteen years later, the Turks took it back almost without a struggle. This barely known episode, often considered as a fruitless attempt from a Republic on the brink of decline, is here considered from diplomatic and strategic viewpoints, at the core of larger international stakes. The present study, chiefly based on unused archival material, unveils the different phases of the conflict between the Porte and the Holy League in the various fields, and attempts to examine the real significance of the Venetian intervention, the motivations, the means and the potential, the organization, the strategies. En 1684, la République de Venise s’allia à l’Empire, à la Pologne et à la Papauté pour repousser les Ottomans qui venaient de subir un cinglant échec devant Vienne. En quelques campagnes, les troupes de la Sérénissime parvinrent à s’emparer de tout le Péloponnèse (ou Morée) en occupant les places fortes du pays. Le traité de Karlowitz de 1699 entérina cette conquête mais, quinze années plus tard, les Turcs la récupérèrent sans peine. Cet épisode mal connu, souvent interprété comme le vain baroud d’honneur d’une Venise sur le déclin, a ici été traité du point de vue diplomatique et stratégique ; il se situe au cœur d’enjeux internationaux beaucoup plus larges. Cette étude, basée largement sur des documents d’archives inédits, retrace les différentes phases du conflit opposant la Sainte Ligue à la Porte sur les divers théâtres d’opérations, et tente d’analyser le rôle exact joué par les Vénitiens, leurs motivations, leurs moyens, leur organisation, leurs stratégies.

Connectivity was assessed during ATLAS for a diversity of organisms, from the corals that structure Vulnerable Marine Ecosystems (VMEs) to economically important fishery species using two main pathways. Predicted connectivity patterns were obtained through simulated larval Lagrangian particle modelling, based on oceanographic data gained in WP1 and reproductive knowledge produced in WP4. Realised connectivity was inferred using population genetics on sets of samples gathered before and during ATLAS, focusing on a subset of the target species initially listed, for which enough samples could be gathered to perform comprehensive population genetics analysis. Lagrangian modelling of larval dispersal within ATLAS unravelled the effect of long-term ocean variability (Atlantic Meridional Overturning Circulation - AMOC, subpolar gyre strength - SPG and North Atlantic Oscillation - NAO) and larval behaviour on particle transport pathways and population connectivity (Fox et al., 2016), the contribution of man-made structures to connectivity (Henry et al., 2018) and the application of these results to marine planning and the development of ecologically coherent marine protected area networks. This work has underlined the crucial need for data on reproductive and larval biology to inform these predictions (Fox et al., 2016). This proved to be even more important for deep-sea species due to the vast extent of the water column through which larvae can disperse. Very different outcomes can be expected depending not only on the timing of reproduction or the length of pelagic larval duration (PLD), but also on the behaviour of larvae remaining on the seafloor or migrating more or less along the water column. The relationship between PLD and “realised connectivity” as estimated through population genetics is far from easily predictable, despite some relationship existing (Riginos et al., 2011). This is likely to be worse in the deep sea as exemplified by recent models where extensive PLD resulted in extreme variance of predicted connectivity (Ross et al., 2019), possibly due to the importance of the third dimension (depth) in the space potentially explored by larvae. Nevertheless, the new method developed in ATLAS (Fox et al., 2019) allows a generic approach to optimise multi objectives in the design of MPAs. This showed that for highly dispersive behaviours, all the Northern Atlantic could in theory be connected with a favoured anti-clockwise dispersal along the slopes. Results also underlined that seamount populations may act as crucial stepping stones (hubs) in the broad scale connectivity, placing them in the priority list to maintain connectivity for a broad range of species. This important role of seamounts and offshore banks was also demonstrated through Lagrangian modelling based on the reef coral Lophelia pertusa’s reproductive and larval biology (Fox et al., 2016). As for inferences of “realised” connectivity, population genetics and genomics allow identification of distinct management units (MUs; Palsbøll et al., 2007), i.e. populations of conspecific individuals among which the degree of connectivity is sufficiently low so that each population should be monitored and managed separately, for example along the Northeast Atlantic coasts and the Mediterranean where the majority of samples analysed within ATLAS framework could be gathered. These samples laid also the foundations for a basin-scale analysis in the coming years in collaboration with partners from the northwest Atlantic under the leadership of the EU-funded project iAtlantic (see below). Importantly, genetically differentiated populations are not only demographically independent but may also shelter singular genetic diversity, one of the three components of biodiversity in need for conservation but too long neglected by management and conservation plans (Laikre et al., 2010). This was true for VMEs species such as Madrepora oculata, but also the commensal polychaete Eunice norvegica where at least one cryptic species was identified in the Atlantic. As for Lophelia pertusa, homogeneity was found in the Bay of Biscay despite some hints of differentiation of SE Rockall bank (Boavida et al., 2019b). The occurrence of those distinct MUs, or even distinct evolutionary significant units (ESUs; Ryder, 1986) in the case of Eunice sp., is essential for conservation, for each of them should be treated as distinct diversity entities, with no demographic (Brown Kodric-Brown, 1977) interdependence. This also means in case one MU would collapse, no evolutionary (Orr Unckless, 2014; Tomasini Peischl) rescue effect can be expected from the others, which needs to be accounted for in monitoring and management plans. Fish species studied in ATLAS were chosen among the target listed at the origin of the project for both their economic interest and, likewise invertebrates, the availability of samples to allow assessing connectivity over broad scales with a sufficient number of samples. Distinct MUs were also detected in the boarfish Capros aper, the horse mackerel Trachurus trachurus, and the Norway lobster Nephrops norvegicus. These MUs are demographically independent populations, thus multiple stocks expected to respond independently to harvesting and management. While the MUs in the boarfish largely agreed with the areas defined by the International Council for the Exploration of the Sea (ICES) (one exception though being noticed in the southern border), uncertainties remain for the horse mackerel and clear mismatches were revealed between MUs defined with genetic data and management areas for the Norway lobster, calling for a revision of management plans. In this report, we also develop detailed explanations of the difference between genetic and demographic independency that are essential to understand the power and limitation of population genomics, but also to account for connectivity data in management plans. We believe those explanations are essential to share with managers and stakeholders, as well as scientific colleagues expert in fields other than population genetics who are interested in applying population genetics to management and conservation. On the basis of the results obtained in ATLAS, guidelines could be provided for future management plans, whether through the identification of mismatch between fisheries management units and the genetic differentiation of stocks, or the identification of genetically specific and disconnected populations for benthic organisms characterising VMEs. In fact, nearly every species showed a singular spatial delineation of MUs, resulting in a mosaic of patterns illustrating the challenge of multispecies purpose MPAs. One result is to account for the most limited connectivity potential in management plans, to ensure the maintenance of exchanges. In fact accounting for very limited dispersal to include connectivity in spatial planning showed the need to design large areas and to favour contiguous prioritisation units for conservation (Combes et al., in prep.). Remaining uncertainties in areas where no genetic differentiation was detected is also important to consider and is different among taxa. Compared to those species for which clear MUs (or even ESUs) could be recognised, there were species and areas where no genetic differentiation could be detected (such as Lophelia pertusa in the Bay of Biscay), or no signature of bottleneck could be encountered (as was the case for most populations studied in ATLAS), despite extensive referenced exploitation or habitat destruction. In such cases it is very difficult to disentangle the real absence of barrier to gene flow and/or bottleneck from the insufficient power of the molecular method used. As demonstrated recently through simulations (Bailleul et al., 2018), there is a time lag between the moment barriers to connectivity or bottleneck occur and their signature can be detected through population genetics. This was designed as the “grey zone effect” and its duration depends on the statistical power delivered by the set of genetic markers used, but can encompass several tens to a thousand years. New generation high density genome scan analysis can help increasing the statistical power to detect such events. However, these methods are very demanding in terms of DNA quality and not all collections examined in ATLAS, particularly the older ones, gave such high quality DNA. Much work was thus dedicated during ATLAS to resolving DNA extraction protocols so that important existing deep-sea sample collections could be used. First results obtained on the two reef framework-forming corals and their associated commensal polychaete (Eunice spp., for we now know it encompasses at least two species), as well as the coral Dendrophyllia cornigera. For the last two species some samples liberated high quality DNA to build libraries that are being produced, and will allow to inferring our ability to detect hitherto ignored disruption of connectivity or bottlenecks. These data will be completed, analysed and interpreted beyond ATLAS, in the framework of iAtlantic using lessons learnt from genomic issues met and circumvented during ATLAS. Due to issues related to DNA quality, RADSeq analysis on a dozen species for which just a handful of specimens met DNA quality standards allows the provision of genomic resources to be used with protocols requiring a lower DNA quality standard. These new resources will allow optimisation of the use of old but precious specimens and DNA collections of deep-sea organisms. Along with the basin scale analysis forecast for the two main reef framework-forming corals taxa in collaboration with US partners, those are important perspectives of development beyond ATLAS, that are planned to emerge during the iAtlantic project.

The flow of warm and saline water from the Atlantic Ocean, across the Greenland–Scotland Ridge, into the Nordic Seas – the Atlantic inflow – is split into three separate branches. The most intense of these branches is the inflow between Iceland and the Faroe Islands (Faroes), which is focused into the Faroe Current, north of the Faroes. The Atlantic inflow is an integral part of the North Atlantic thermohaline circulation (THC), which is projected to weaken during the 21st century and might conceivably reduce the oceanic heat and salt transports towards the Arctic. Since the mid-1990s, hydrographic properties and current velocities of the Faroe Current have been monitored along a section extending north from the Faroe shelf. From these in situ observations, time series of volume, heat, and salt transport have previously been reported, but the high variability of the transport has made it difficult to establish whether there are trends. Here, we present results from a new analysis of the Faroe Current where the in situ observations have been combined with satellite altimetry. For the period 1993 to 2013, we find the average volume transport of Atlantic water in the Faroe Current to be 3.8 ± 0.5 Sv (1 Sv = 106 m3 s−1) with a heat transport relative to 0 °C of 124 ± 15 TW (1 TW = 1012 W). Consistent with other results for the Northeast Atlantic component of the THC, we find no indication of weakening. The transports of the Faroe Current, on the contrary, increased. The overall increase over the 2 decades of observation was 9 ± 8 % for volume transport and 18 ± 9 % for heat transport (95 % confidence intervals). During the same period, the salt transport relative to the salinity of the deep Faroe Bank Channel overflow (34.93) more than doubled, potentially strengthening the feedback on thermohaline intensity. The increased heat and salt transports are partly caused by the increased volume transport and partly by increased temperatures and salinities of the Atlantic inflow, which have been claimed mainly to be caused by the weakened subpolar gyre.

The Nekton Maldives Taxonomic Workshop took place at the Maniyafushi Research Station in the Maldives between 12 and 23 February 2023. This workshop had two primary objectives. Firstly, it aimed to identify species from biological samples and underwater imagery collected during the Nekton Maldives Mission in 2022. Secondly, it sought to facilitate training and knowledge exchange sessions between early career researchers from the Maldives and international taxonomists. These sessions were designed to share knowledge and introduce fundamental taxonomy concepts and enhance practical identification skills for common reef benthic groups and major zooplankton taxonomic groups. A total of 24 people from 10 different countries were directly or indirectly involved with the workshop comprising nine taxonomic experts, eleven trainees and four organisers. Collectively, we identified 278 biological specimens including potentially undescribed species of hydroids, black corals, sponges and octocorals, 318 morphotypes for underwater footage and zooplankton composition congruent with previous reports from the Indian Ocean Region. Next steps will involve depositing the specimens into a more a permanent facility to facilitate the process of specimen description and knowledge transfer.

About one third of the anthropogenic carbon dioxide (CO2) released into the atmosphere in the past two centuries has been taken up by the ocean. As CO2 invades the surface ocean, carbonate ion concentrations and pH are lowered. Laboratory studies indicate that this reduces the calcification rates of marine calcifying organisms, including planktic foraminifera. Such a reduction in calcification resulting from anthropogenic CO2 emissions has not been observed, or quantified in the field yet. Here we present the findings of a study in the Western Arabian Sea that uses shells of the surface water dwelling planktic foraminifer Globigerinoides ruber in order to test the hypothesis that anthropogenically induced acidification has reduced shell calcification of this species. We found that light, thin-walled shells from the surface sediment are younger (based on 14C and δ13C measurements) than the heavier, thicker-walled shells. Shells in the upper, bioturbated, sediment layer were significantly lighter compared to shells found below this layer. These observations are consistent with a scenario where anthropogenically induced ocean acidification reduced the rate at which foraminifera calcify, resulting in lighter shells. On the other hand, we show that seasonal upwelling in the area also influences their calcification and the stable isotope (δ13C and δ18O) signatures recorded by the foraminifera shells. Plankton tow and sediment trap data show that lighter shells were produced during upwelling and heavier ones during non-upwelling periods. Seasonality alone, however, cannot explain the 14C results, or the increase in shell weight below the bioturbated sediment layer. We therefore must conclude that probably both the processes of acidification and seasonal upwelling are responsible for the presence of light shells in the top of the sediment and the age difference between thick and thin specimens.

In the Etang de Thau (Herault, France), three species of Helicometra parasitize in their adult stage the digestive tract of the black goby Gobius niger, the grass goby Zosterisessor ophiocephalus, the grey wrasse Symphodus cinereus, and the common eel Anguilla anguilla (Teleostei). These fish act as definitive hosts in the biological cycle of these platyhelminths. Also H. gobii exists in G. niger, Z. ophiocephalus, S. cinereus and A. anguilla ; H. fasciata is found in G. niger ; and H. pulchella is only found in S. cinereus. In the case of the two gobies and the eel, these three congeneric digenes sometimes coexist in the same infracommunity. Spatio-temporal analysis of these different populations has enabled : 1) detection of seasonal variations in their structure, 2) identification of the relationships between the nature of their specificity and demographic strategy, and 3) the global absence of statistical dependence between the intensities of different species in the same infracommunity to be show. Implications arising from previous research concerning the demographic behaviour of these trematodes in their first intermediate host (mollusc compartment), were taken into account when interpreting structures observed in the definitive hosts. The problems of coexistence between these species, which are taxonomically very close in the same parasite community, and the under-lying speciation mechanisms are discussed in the light of population structuration.

Recent observations and modelling studies suggest that biogeochemical changes can mask atmospheric CO2-induced pH decreases. Data collected by the Dutch monitoring authorities in different coastal systems (North Sea, Wadden Sea, Ems-Dollard, Eastern Scheldt and Scheldt estuary) since 1975 provide an excellent opportunity to test whether this is the case in the Dutch coastal zone. The time-series were analysed using Multi-Resolution Analysis (MRA) which resulted in the identification of system-dependent patterns on both seasonal and intra-annual time scales. The observed rates of pH change greatly exceed those expected from enhanced CO2 uptake, thus suggesting that other biogeochemical processes, possibly related to changes in nutrient loading, can play a dominant role in ocean acidification.