Food sources, behaviour, and distribution of hydrothermal vent shrimps at the Mid-Atlantic Ridge

Five species of bresilioid shrimp were investigated at seven hydrothermal sites on the Mid-Atlantic Ridge: Menez Gwen, Lucky Strike, Rainbow, Broken Spur, TAG, Snake Pit and Logatchev. Samples were prepared for analysis of stable isotopes, elemental composition and lipids. Shrimp behaviour was observed from the submersible ‘Alvin’ and in the laboratory aboard RV ‘Atlantis’. The distribution and zonation of the shrimp species was recorded. Juvenile shrimp of all species arrive at the vents carrying reserves of photosynthetic origin, built-up in the pelagic larval stages. These reserves are used while the shrimp metamorphose to the adult form and, in Rimicaris exoculata and Chorocaris chacei, while they develop epibiotic bacteria supporting structures, the modified mouthparts and the inside of the carapace. The main food of adult R. exoculata is filamentous bacteria that grow on these structures. The intermediate sizes of C. chacei also feed on such bacteria, but the final stage gets some food by scavenging or predation. Mirocaris species scavenge diverse sources; they are not trophically dependent on either R. exoculata or mussels. Adults of Alvinocaris markensis are predators of other vent animals, including R. exoculata. The dense swarms of R. exoculata, with their exosymbionts, can be compared to endosymbiont-containing animals such as Bathymodiolus and the vestimentiferan tube-worms of the Pacific vents. Such associations, whether endo- or ectosymbiotic, may be necessary for the development of flourishing communities at hydrothermal vents

Mikroobselt indutseeritud settetekstuurid ja nende interpreteerimine Paleoproterosoikumi Kondopoga kihistu (Karjala) mudakivimites

Käesolevas töös uuriti võimalikke mikrobiaalselt indutseeritud settetekstuure Paleoproterozoikumi Kondopoga kihistus, Karjalas ja anti ülevaade mikroobselt indutseeritud settetekstuuride (MIST) tekkimisest ja tunnusest ning geoloogilise tõlgenduse võimalustest. Makroskoopiliste tunnuste alusel võib Noffke (2009) klassifikatsiooni järgi pidada Kondopoga MISTe läbipaistmatuteks kortsulisteks tekstuurideks mida moodustavad sette pinnal elavad tsüanobakterite kolooniatest moodustunud biomatid. Sama ajal ei näidanud mikroskoopilised uuringud ja elementide kaardistamine, et oleksid säilinud või fossiliseerunud biomati bioloogilised osad. Samuti ei näita ka elementide jaotumine selget seost biomati moodustumisega, mis võiks väljenduda bioaktiivsete elementide spetsiifilises kontsentreerumises nendes kihtides. Siiski viitavad Ti-mineraalide lamellid võimalusele, et biomatti on haaratud raske fraktsiooni kuuluvate mineraalide terasid

Assessing the status, variability, and biodiversity conservation issues of Arctic benthic ecosystems of the Pechora Sea for improved management

The biodiversity of the Arctic Ocean is described by the Arctic Council as an “irreplaceable cultural, scientific, ecological, economic and spiritual asset”. Global climate change together with industrial development pose major threats to Arctic ecosystems and biodiversity including but not limited to rise in water and air temperatures, loss of sea ice habitats, introduction of nonindigenous species (NIS) and anthropogenic pollution. The urgent need to protect Arctic marine ecosystems and biodiversity is emphasised in many national and international strategies and policy framework documents. Furthermore, improvement of baseline knowledge and implementation of ecosystem-based management are identified as key “actions for biodiversity”. Macrobenthic communities are one of the most conservative biotic components of marine ecosystems and are therefore prominently used in ecological monitoring as indicators of good environmental status of ecosystems. At the same time, macrobenthic invertebrates are focal ecosystem components as they provide food resources to sustain benthic predators of higher trophic levels. Our knowledge of Arctic benthic ecosystems, their biodiversity, temporal variability, individual and cumulative impacts of environmental stressors remain fragmentary and often insufficient for knowledge-based decision-making. This thesis aimed to improve regional knowledge through assessing the status, variability and biodiversity conservation issues of Arctic benthic ecosystems of the ecologically significant area of the Barents Sea, the Pechora Sea, for improved management. An extensive dataset on macrobenthos of the Pechora Sea was compiled through participating in a series of expeditions to the Pechora Sea with additional samples obtained in zoological collections or provided by partner institutions (Lomonosov Moscow State University Marine Research Center and Shirshov Institute of Oceanology, Russian Academy of Sciences). A total of 213 grab samples were used to study biodiversity and variability of macrobenthos in two research areas in the Pechora Sea – the Pechora Bay and Vaigach Island. Assessment of video footage obtained using remotely operated vehicles revealed likely increasing in time presence of important benthic NIS snow crab Chionoecetes opilio (O. Fabricius, 1788) near Vaigach Island. Morphological analysis of stomach content was performed to characterise trophic niches of C. opilio and assess overlap with the diets of native benthic decapods, Hyas araneus (Linnaeus, 1758) and Pagurus pubescens Krøyer, 1838. Accumulation of microplastics in benthic invertebrates of the Pechora Sea was then assessed and compared with samples from the Kara Sea, Laptev Sea and East-Siberian Sea. Macrobenthos of the continental shallows of the Pechora Bay were described for the first time in this thesis. A monodominant community of Limecola balthica (Linnaeus, 1758) comprised of eurythermal and euryhaline forms with reduced biomass, was shown to be at the margins of its distribution. In contrast, near Vaigach Island a high biomass, heterogeneous, macrobenthic community was found. During the six years of observations (2015–2020), the mean biomass, abundance, production and species composition fluctuated with no clear trends between years. Twenty categories of prey items were identified in the diets of benthic decapods near Vaigach Island. Overlap in diets of the three species suggested that C. opilio likely competes for food resources with both H. araneus and P. pubescens. A conceptual diagram was generated to illustrate trophic interspecies relationships between benthic predators and macrobenthic communities in the Pechora Sea. Microplastics were found to be a likely stressor on Arctic benthic ecosystems. Microplastic fibres were recorded in 29% of all samples of the Pechora Sea macrobenthos. Furthermore, an increase of average frequency of ingested microplastics in the field samples collected in 2017– 2018 compared to the historical samples from 2008 was proved statistically significant. Similar occurrence of ingested microplastics were discovered in other studied regions of the Eurasian Arctic (average 27±2%). No significant differences in occurrence of ingested microplastics were identified between species, feeding guilds or sampling sites. A conceptual diagram was developed to illustrate microplastic ingestion by benthic fauna from different feeding guilds in the Pechora Sea. Overall, the outcomes of this thesis provided valuable data, which are essential to review the current state of benthic biodiversity in the Pechora Sea, characterise the observed and expected impacts of key drivers of environmental change on benthic ecosystems, and provide recommendations including monitoring parameters and techniques, integration of which into the regional ecological monitoring programmes will lead to a more comprehensive understanding of the state and dynamics of the Pechora Sea benthic ecosystems. The Pechora Sea provides a case study illustrating the importance of incorporating data on benthic ecosystems into the marine spatial planning and specifically the design of marine protected areas, as well as the need for establishment of long-term ecological monitoring programmes with standardised approaches to data collection and interpretation to underpin the informed decision-making needed for sustainable development of the Arctic region

Different energy sources for three symbiont-dependent bivalve molluscs at the Lagatchve hydrothermal site (Mid Atlantic Ridge)

The vent mussel Bathymodiolus puteoserpentis, a large vesicomyid clam and a smaller thyasirid were collected from an area of sediment subject to diffuse hydrothermal flow. The mussels live on the surface, the vesicomyids are partly buried and the thyasirids burrow in the sediment. The fine structure of the gills differs in the three bivalves. Bathymodiolus puteoserpentis hosts two types of bacterial symbiont, one methanotrophic, and another probably thiotrophic. The other two bivalves have single types of symbiont of different shapes. Stable isotope ratios of carbon and nitrogen indicate thiotrophy in the vesicomyid and thyasirid, but a predominance of methanotrophy in the mussel. This is the first time that such an assemblage has been found at a hydrothermal site on the Mid-Atlantic Ridge (MAR), with the different faunistic elements exploiting different energy resource

Shared Arctic Variable Framework Links Local to Global Observing System Priorities and Requirements

The geographic settings and interests of diverse groups of rights- and stakeholders figure prominently in the need for internationally coordinated Arctic observing systems. Global and regional observing systems exist to coordinate observations across sectors and national boundaries, leveraging limited resources into widely available observational data and information products. Observing system design and coordination approaches developed for more focused networks at mid- and low latitudes are not necessarily directly applicable in more complex Arctic settings. Requirements for the latter are more demanding because of a greater need for cross-disciplinary and cross-sectoral prioritization and refinement from the local to the pan-Arctic scale, in order to maximize the use of resources in challenging environmental settings. Consideration of Arctic Indigenous Peoples’s observing priorities and needs has emerged as a core tenet of governance and coordination frameworks. We evaluate several different types of observing systems relative to the needs of the Arctic observing community and information users to identify the strengths and weaknesses of each framework. A typology of three approaches emerges from this assessment: “essential variable,” “station model,” and “central question.” We define and assess, against the requirements of Arctic settings, the concept of shared Arctic variables (SAVs) emerging from the Arctic Observing Summit 2020 and prior work by the Sustaining Arctic Observing Networks Road Mapping Task Force. SAVs represent measurable phenomena or processes that are important enough to multiple communities and sectors to make the effort to coordinate observation efforts worthwhile. SAVs align with essential variables as defined, for example, by global observing frameworks, in that they guide coordinated observations across processes that are of interest to multiple sectors. SAVs are responsive to the information needs of Arctic Indigenous Peoples and draw on their capacity to codesign and comanage observing efforts. SAVs are also tailored to accommodate the logistical challenges of Arctic operations and address unique aspects of the Arctic environment, such as the central role of the cryosphere. Specific examples illustrate the flexibility of the SAV framework in reconciling different observational approaches and standards such that the strengths of global and regional observing programs can be adapted to the complex Arctic environment. Les contextes géographiques et les intérêts de divers groupes de détenteurs de droits et de parties prenantes figurent au premier plan des besoins en systèmes d’observation de l’Arctique coordonnés à l’échelle internationale. Il existe des réseaux d’observation d’envergure mondiale et régionale visant à coordonner les observations en provenance de divers secteurs et de frontières nationales, s’appuyant sur des ressources limitées pour donner lieu à des données d’observation et à des produits d’information grandement accessibles. Les réseaux d’observation et les approches de coordination conçus pour des réseaux spécialisés desservant les latitudes allant de moyennes à faibles ne se transposent pas directement aux contextes plus complexes de l’Arctique. Dans le cas de l’Arctique, les exigences sont plus élevées en raison du plus grand besoin d’accorder de l’importance aux disciplines et aux secteurs variés ainsi qu’au raffinement de l’échelle, qui passe de locale à panarctique, afin de maximiser l’utilisation des ressources dans des contextes environnementaux difficiles. La considération des besoins et des priorités d’observation des peuples autochtones de l’Arctique constitue un des principaux principes des cadres de gouvernance et de coordination. Nous évaluons plusieurs types différents de réseaux d’observation à la lumière des besoins de la communauté d’observation de l’Arctique et des utilisateurs d’information afin de cerner les forces et les faiblesses de chaque cadre de référence. Cette évaluation a permis de produire une typologie de trois approches : la « variable essentielle », le « modèle de station » et la « question centrale ». Nous définissons et évaluons, en fonction des exigences des contextes de l’Arctique, le concept des variables partagées de l’Arctique (SAV) qui est ressorti du sommet d’observation de l’Arctique de 2020 et de travaux antérieurs réalisés par le groupe de travail des réseaux Sustaining Arctic Observing Networks Road Mapping Task Force. Les SAV représentent des processus ou des phénomènes mesurables suffisamment importants aux yeux de communautés et de secteurs divers pour que la coordination des efforts d’observation en vaille la peine. Les SAV concordent avec les variables essentielles comme définies, par exemple, par les cadres d’observation mondiaux, en ce sens qu’elles guident les observations coordonnées relevant de processus qui revêtent de l’intérêt pour de multiples secteurs. Les SAV accordent de l’importance aux besoins en information des peuples autochtones de l’Arctique et font appel à leurs capacités à concevoir et à gérer les efforts d’observation en collaboration. Par ailleurs, les SAV sont conçues pour tenir compte des défis logistiques des opérations dans l’Arctique et tiennent compte d’aspects uniques de l’environnement arctique, comme le rôle central de la cryosphère. Certains exemples illustrent la souplesse du cadre des SAV pour réconcilier diverses approches et normes d’observation, de sorte que les points forts des programmes d’observation mondiaux et régionaux puissent être adaptés à l’environnement complexe de l’Arctique.

Uniform bathymetric zonation of marine benthos on a Pan-Arctic scale

While numerous regional studies of bathymetric zonation of benthic fauna globally have been done, few large-scale analyses exist, and no ocean-scale studies have focused on the Arctic Ocean to date. In the present work we, hence, examined bathymetric zonation of macro- and megabenthos over a depth range spanning from the shelf to the abyssal plain (14 – 5416 m) and regionally extending from the Fram Strait to the Beaufort Sea (as a whole hereafter called the Central Arctic). Based on 104 quantitative (box-corers and grabs) and 37 semi- quantitative (trawls) samples compiled from different studies we evaluated bathymetric zonation patterns in abundance, biomass and diversity, and also compared species composition among samples. Abundance and biomass decreased with depth from > 3000 ind. m−2 and > 40 g ww m−2 to ∼ 130 ind. m−2 and −2 corroborating previous studies. Diversity showed a parabolic pattern, peaking at ∼ 100–600 m. Cluster analysis revealed four (macrofauna) and five (megafauna) groups of benthic assemblages, including three that covered the upper and lower continental slope and the abyssal plains with relatively little overlap (named the Lower Shelf – Upper Slope 1, the Lower Slope and the Abyss). Substantial changes in benthic community composition were observed at depths 650–950 m (between the Lower Shelf – Upper Slope 1 and the Lower Slope) and 2600–3000 m (between the Lower Slope and the Abyss), so we interpreted these two depth horizons as major bathymetric boundaries. The first boundary (650–950 m) corresponds to the transition from sublittoral to bathyal fauna consistent with previous studies. The second boundary (2600–3000 m) reflects a decrease in benthic abundance, biomass and diversity within the Central Arctic abyssal plain. Bathymetric patterns and species overturn of benthos were relatively uniform throughout the entire Central Arctic continental slope and abyssal plain. For some regions of the Arctic Ocean, foremost for the area north from Greenland and Canadian Archipelago, benthic data are still unavailable and further research is needed

Does Presence of a Mid-Ocean Ridge Enhance Biomass and Biodiversity?

In contrast to generally sparse biological communities in open-ocean settings, seamounts and ridges are perceived as areas of elevated productivity and biodiversity capable of supporting commercial fisheries. We investigated the origin of this apparent biological enhancement over a segment of the North Mid-Atlantic Ridge (MAR) using sonar, corers, trawls, traps, and a remotely operated vehicle to survey habitat, biomass, and biodiversity. Satellite remote sensing provided information on flow patterns, thermal fronts, and primary production, while sediment traps measured export flux during 2007-2010. The MAR, 3,704,404 km 2 in area, accounts for 44.7% lower bathyal habitat (800-3500 m depth) in the North Atlantic and is dominated by fine soft sediment substrate (95% of area) on a series of flat terraces with intervening slopes either side of the ridge axis contributing to habitat heterogeneity. The MAR fauna comprises mainly species known from continental margins with no evidence of greater biodiversity. Primary production and export flux over the MAR were not enhanced compared with a nearby reference station over the Porcupine Abyssal Plain. Biomasses of benthic macrofauna and megafauna were similar to global averages at the same depths totalling an estimated 258.9 kt C over the entire lower bathyal north MAR. A hypothetical flat plain at 3500 m depth in place of the MAR would contain 85.6 kt C, implying an increase of 173.3 kt C attributable to the presence of the Ridge. This is approximately equal to 167 kt C of estimated pelagic biomass displaced by the volume of the MAR. There is no enhancement of biological productivity over the MAR; oceanic bathypelagic species are replaced by benthic fauna otherwise unable to survive in the mid ocean. We propose that globally sea floor elevation has no effect on deep sea biomass; pelagic plus benthic biomass is constant within a given surface productivity regime

Fauna associated with shallow-water methane seeps in the Laptev Sea

Background Methane seeps support unique benthic ecosystems in the deep sea existing due to chemosynthetic organic matter. In contrast, in shallow waters there is little or no effect of methane seeps on macrofauna. In the present study we focused on the recently described methane discharge area at the northern Laptev Sea shelf. The aim of this work was to describe the shallow-water methane seep macrofauna and to understand whether there are differences in macrobenthic community structure between the methane seep and background areas. Methods Samples of macrofauna were taken during three expeditions of RV Akademik Mstislav Keldysh in 2015, 2017 and 2018 using 0.1 m2 grabs and the Sigsbee trawl. 21 grabs and two trawls in total were taken at two methane seep sites named Oden and C15, located at depths of 60–70 m. For control, three 0.1 m2 grabs were taken in area without methane seepage. Results The abundance of macrofauna was higher at methane seep stations compared to non-seep sites. Cluster analysis revealed five station groups corresponding to control area, Oden site and C15 site (the latter represented by three groups). Taxa responsible for differences among the station groups were mostly widespread Arctic species that were more abundant in samples from methane seep sites. However, high densities of symbiotrophic siboglinids Oligobrachia sp. were found exclusively at methane seep stations. In addition, several species possibly new to science were found at several methane seep stations, including the gastropod Frigidalvania sp. and the polychaete Ophryotrocha sp. The fauna at control stations was represented only by well-known and widespread Arctic taxa. Higher habitat heterogeneity of the C15 site compared to Oden was indicated by the higher number of station groups revealed by cluster analysis and higher species richness in C15 trawl sample. The development of the described communities at the shallow-water methane seeps can be related to pronounced oligotrophic environment on the northern Siberian shelf.publishedVersio

Vertical zonation of the Siberian Arctic benthos: bathymetric boundaries from coastal shoals to deep-sea Central Arctic

The bathymetric distribution of species of Annelida, Crustacea and Echinodermata from the region including the Kara, Laptev and East Siberian seas and the adjacent region of the deep-sea Central Arctic was analysed. We focused on vertical species ranges revealing zones of crowding of upper and lower species range limits. Using published data and in part the material obtained during the expeditions of the P.P. Shirshov Institute of Oceanology, we evaluated species vertical distribution from 0 m to the maximum depth of the Central Arctic (~4,400 m). The entire depth range was divided into smaller intervals; number of upper and lower limits of species depth ranges was counted and plotted to visualize the range limits crowding. Several zones of crowding of vertical species range limits were found for all analysed macrotaxa. The most significant zones occurred at depths of 450–800 m and 1,800–2,000 m. The first depth zone corresponds to the boundary between the sublittoral and bathyal faunas. The last one marks the boundary between the bathyal and abyssal faunas. Depths of these boundaries differ from those reported from other Ocean regions; possible explanations of these differences are discussed