Epibenthic Sledge Research Articles

A new species of the genus Monstrilla (Copepoda: Monstrilloida: Monstrillidae) from the Gulf of California, Mexico

Based on deep-water (700-750 m) biological samples obtained from the southern Gulf of California, Pacific coast of Mexico, a new species of the monstrilloid copepod genus Monstrilla Dana, 1849 is described based on a single subadult female collected close to the bottom with an epibenthic sledge. Monstrilla hendrickxi sp. n. is distinguished by a unique combination of characters including: 1) no trace of eyes; 2) strong, thick antennules with segments 2-4 partly fused; 3) strongly developed apical elements on antennular segment 5 and spinous processes on segments 2-5; and 4) bilobed fifth legs with 2 apical setae on the exopodal lobe and a digitiform, unarmed endopodal lobe. The new species exhibits some affinity with surface-dwelling species of Monstrilla that have 2 setae on the exopodal lobes of the fifth legs. This is the fifth record of a species of the order Monstrilloida in the Gulf of California. The present discovery in deep oceanic waters significantly adds to our knowledge of the habitat range of this copepod order and likely anticipate further interesting findings of monstrilloids in deep waters worldwide.

Two new species of Cymbasoma (Multicrustacea: Copepoda: Monstrilloida: Monstrillidae) from the North Atlantic

ABSTRACT Monstrilloid copepods are protelean endoparasites of benthic invertebrates. Their adult free-living stage is chiefly found in the plankton of shallow coastal systems, estuaries and coral reefs; there are no previous records of monstrilloids from deeper marine habitats including epipelagic or mesopelagic waters. Two new species of the monstrilloid copepod genus Cymbasoma Thompson, 1888 are described based on adult females incidentally captured by an epibenthic sledge operated at a depth range of 118–302 m off north-west Iceland and the Norway Channel. Cymbasoma norvegicum sp. nov. is distinguished by a combination of characters including a long, constricted anal somite, bilobed fifth legs with long inner lobe, antennules with fused segments, and first antennule segment unarmed. Cymbasoma pedroi sp. nov. has a pair of rounded posterolateral protuberances on the genital somite, fused fifth legs lobes, and an anteriorly produced, ornamented forehead. Both species are considered new members of the Cymbasoma rigidum species group, widely distributed in different geographic areas but not previously known from epi-mesopelagic depths. The finding of these new species represents the first discovery of monstrilloids at epi-mesopelagic depths in the Pacific Ocean and it significantly adds to our knowledge of this copepod order, thus highlighting their potentially high yet unstudied diversity in deeper waters. http://www.zoobank.org/urn:lsid:zoobank.org:pub:C05EEC28-9936-41CB-BC9E-D990AE53B3B1

Pan-Atlantic Comparison of Deep-Sea Macro- and Megabenthos

Deep-sea benthic fauna is vital for a well-functioning marine ecosystem but is increasingly under threat from a changing environment. To monitor and conserve this fauna, an understanding of their large-scale spatial and bathymetric distribution and their environmental drivers is necessary. In this study, we conduct a multivariate analysis on abundance benthic fauna data collected at the phylum and multitaxon levels using an epibenthic sledge (EBS) across the Atlantic, and identify the environmental factors that affect such data. Our findings show a decrease in abundance with depth in most of the Atlantic but find relatively heterogeneous abundances with depth within the Southern Ocean. Principal component analyses indicate differences in environmental conditions south of the Antarctic Polar Front (~52° S), outlining contrasts in the quantities of macronutrients and physical factors. Despite this, community composition seemed markedly similar throughout the Atlantic with the Antarctic Circumpolar Current seemingly not affecting benthic community composition for higher taxonomic levels. Those differences that did occur were largely caused by benthic chlorophyll, benthic iron, and surface silicate through a Bio-ENV. Overall, we argue that further large-scale spatial and bathymetric distribution studies are important amid environmental changes that are driving shifts in benthic community abundance and composition.

Community structure of abyssal macrobenthos of the South and equatorial Atlantic Ocean - Identifying patterns and environmental controls

The DIVA (Latitudinal Gradients of Deep-sea BiodDIVersity in the Atlantic) expeditions studied benthic biodiversity of the abyssal Equatorial and South Atlantic as part of the Census of the Diversity of Abyssal Marine Life (CeDAMar), the abyssal component of the ten-year programme Census of Marine Life (2000–2010). Three expeditions were carried out from RV Meteor between 2000 and 2009. Samples were taken along a latitudinal gradient spanning the Cape, Angola, and Guinea basins in the SE Atlantic and the Argentine and Brazilian basins in the SW Atlantic. The objectives of this study were to analyse patterns of epi- and suprabenthic macrofaunal density and composition at higher taxon level from epibenthic sledge (EBS) taken during the DIVA sampling campaigns and how they relate to differences in environmental conditions. In particular, the different oceanic basins are characterized by variation in surface primary productivity, sedimentary properties, and depth. We expected this difference to be reflected in the structure of the abyssal benthic communities. Consistent with this hypothesis, we found significant differences in macrofauna density between different deep-sea basins, mainly related to food availability. However, only subtle differences in community composition were observed. We found that stations in close proximity to one another showed great variability in both macrofaunal density and composition. We conclude that smaller spatial scale sampling should be paired with higher taxonomic resolution analyses of macrofaunal samples to better understand the factors contributing to variations of macrobenthic communities in the deep sea.

Revealing the Paleo-ocean Environment of OSM-XX in the Western Pacific Magellan Seamount with Mineralogical and Geochemical Properties of Ferromanganese Crust

AbstractVariations in geochemical and mineralogical properties of the ferromanganese(Fe-Mn) crust reflect environmental changes. In the present study, geochemical and mineralogical analyses, including micro X-ray fluorescence and X-ray diffraction, were utilized to reconstruct the paleo-ocean environment of western Pacific Magellan seamount cluster. Samples of the Fe-Mn crust were collected using an epibenthic sledge from the open seamount XX (151° 51.12′ 7.2″ E and 16° 8.16′ 9.6″ N, 1557 meters below sea level) in the Western Pacific Magellan Seamount. According to the structure and phosphating status, the Fe-Mn crust of the OSM-XX can be divided into the following: phosphatizated (L4-L5), massive non-phosphatizated (L3), and porous non-phosphatizated (L1-L2) portions. All ferromanganese layers contain vernadite, and owing to the presence of carbonate fluorapatite (CFA), the phosphatizated portion (L4-L5) is rich in Ca and P. The massive non-phosphatizated section (L3) contains high Mn, Ni, and Co, whereas the porous non-phosphatizated portion (L1-L2), which comprises detrital quartz and feldspar, is rich in Fe. Variations in properties of the Fe-Mn crust from the OSM-XX reflect changes in the nearby marine environment. The formation of this crust started at approximately 51.87 Ma, and precipitation of the CFA during the global phosphatization event that occurred at approximately 36–32 Ma highlights an elevated sea level and low temperature during the associated period. The high Mn, Ni, and Co concentrations and elevated Mn/Fe ratios of samples from the massive phosphatizated portion indicate that the oxygen minimum zone (OMZ) was enhanced, and reducing conditions prevailed during the crust formation. The high Fe and low Mn/Fe ratios in the porous portion indicate a weak OMZ and dominantly oxidizing conditions. These data reflect environmental changes following the end of the Mi-1 glacial period in the Miocene-Oligocene boundary. Subsequently, Mn/Fe and Co/Mn ratios increased slightly in the outermost part of Fe-Mn crust because of the enhanced bottom current and OMZ associated with the continued cooling from approximately 9 Ma. However, the reduced carbonate dissolution rate in the Pacific Ocean from approximately 6 Ma decreased the growth rate of the Fe-Mn crust.망간각의 지화학적, 광물학적 특성의 변화는 인근 환경 변화를 반영한다. 따라서 서태평양 마젤란해산군 OSM-XX의 망간각에 대한 특성 파악과 고해양 복원 연구를 위하여 지화학적, 광물학적 분석을 각각 micro X-ray fluorescence (μ-XRF) 과 X-ray diffraction (XRD)를 이용하여 실시하였다. OSM-XX의 망간각은 인산염화 여부 및 구조에 의해 인산염화 작용을 받은 부분(L4-L5), 인산염화 작용을 받지 않은 치밀한 부분(L3), 인산염화 작용을 받지 않은 다공성 부분(L1-L2)의 세 부분으로 구분되었다. 철망간 산화광물 층에서는 모두 버나다이트 피크가 확인되었으며, 인산염화 작용을 받은 부분은 carbonate fluorapatite(CFA)의 존재와 높은 Ca, P의 특성을 나타내었다. 인산염화 작용을 받지 않은 치밀한 부분은 높은 Mn, Ni, Co를 나타내었고, 인산염화작용을 받지 않은 다공성 부분은 높은 Fe값과 detritus quartz, feldspar가 확인되었다. OSM-XX의 망간각이 성장하는동안 나타난 특성의 변화는 인근 해양환경의 변화를 반영하였다. 약 51.87 Ma의 연대를 나타내는 망간각의 인산염 퇴적체는 약 36-32 Ma의 전지구적 인산염화 작용에 의해 형성된 것으로 보이며, 이는 당시의 상승된 해수면 높이와 낮은 해수온을 지시한다. 또한, 치밀한 구조에서의 높은 Mn, Ni, Co, Mn/Fe 비는 강화된 산소최소층과 환원환경을 지시하며, 다공성 구조에서의 높은 Fe와 낮은 Mn/Fe 비는 약화된 산소최소층과 산화환경을 지시한다. 이는 마이오세-올리고세 경계의 Mi-1 빙하기가 끝난 후 환경변화를 반영하였다. 9 Ma부터 이어진 한랭화의 결과로 인한 저층류와 산소최소층의 강화에 의해 망간각 최외각의 Mn/Fe 비와 Co/Mn 비가 미세하게 증가하였지만, 6 Ma부터 태평양에 발생한 탄산염 용해율의 감소로 성장속도의 감소를 야기하였다.Keywords : ferromanganese crust, paleo-oceanography, redox condition, paleo productivity, western Pacific Magellan seamount

Macrofauna-sized foraminifera in epibenthic sledge samples from five areas in the eastern Clarion-Clipperton Zone (equatorial Pacific)

Benthic foraminifera cannot be sampled adequately using a single device. Smaller taxa are best collected using multicorers, the larger with box corers, but towed devices (dredges, trawls and epibenthic sledges) also retain many larger species. Here, we describe macrofaunal (>300 µm) foraminiferal assemblages obtained using an epibenthic sledge (EBS) in the Clarion-Clipperton Zone (eastern equatorial Pacific), a region hosting seafloor deposits of polymetallic nodules. Twelve EBS samples were collected in four areas licenced for exploration by the International Seabed Authority (ISA) to German, IOM, Belgium and French contractors, and to APEI-3, one of the protected Areas of Special Scientific Interest designated by the ISA. We recognised 280 morphospecies among 1954 specimens, with between 74 (IOM) and 121 (Belgium) in particular areas. Most (92.7%) were single-chambered monothalamids, of which 75 species (26.8%) belonged to the Komokioidea (‘komoki’), 47 (16.8%) to branched and unbranched tubes, 33 (11.8%) to chain-like and 32 (11.4%) to various ‘komoki-like’ forms. Fragments of megafaunal xenophyophores represented 21 species (7.50%), including Spiculammina delicata, previously reported only from the Russian area. Rarefaction curves and sample coverage completeness curves suggest that only a fraction of the macrofaunal foraminiferal diversity had been sampled. The occurrence of 71.8% of species in 1-2 of the 12 samples and 84.9% in 1-3 of the samples was a likely result of substantial undersampling. Dissimilarity in species composition between areas was very high: 64.2% (German vs IOM area) to 86.9% (German area vs APEI-3). Similarity within a single area was quite low: 29.1% (German) to 45.1% (IOM). In multidimensional scaling (MDS) plots, the APEI-3 area was clearly distinct in terms of faunal composition from all other areas, the French area somewhat separated from the German, IOM and Belgium areas, with the German and IOM samples being the most similar. These patterns may reflect the geographical separation of the French and APEI-3 areas and their location in deeper, more oligotrophic waters. Our study demonstrates that EBS samples from the eastern CCZ are a rich source of novel foraminiferal taxa, particularly light, easily resuspended komoki, providing a valuable perspective on foraminiferal biodiversity.

Habitat variability and faunal zonation at the Ægir Ridge, a canyon-like structure in the deep Norwegian Sea.

The Ægir Ridge System (ARS) is an ancient extinct spreading axis in the Nordic seas extending from the upper slope east of Iceland (∼550 m depth), as part of its Exclusive Economic Zone (EEZ), to a depth of ∼3,800 m in the Norwegian basin. Geomorphologically a rift valley, the ARS has a canyon-like structure that may promote increased diversity and faunal density. The main objective of this study was to characterize benthic habitats and related macro- and megabenthic communities along the ARS, and the influence of water mass variables and depth on them. During the IceAGE3 expedition (Icelandic marine Animals: Genetics and Ecology) on RV Sonne in June 2020, benthic communities of the ARS were surveyed by means of a remotely-operated vehicle (ROV) and epibenthic sledge (EBS). For this purpose, two working areas were selected, including abyssal stations in the northeast and bathyal stations in the southwest of the ARS. Video and still images of the seabed were usedtoqualitatively describebenthic habitats based on the presence of habitat-forming taxa and the physical environment. Patterns of diversity and community composition of the soft-sediment macrofauna, retrieved from the EBS, were analyzed in a semiquantitative manner. These biological data were complemented by producing high-resolution bathymetric maps using the vessel’s multi-beam echosounder system. As suspected, we were able to identify differences in species composition and number of macro- and megafaunal communities associated with a depth gradient. A biological canyon effect became evident in dense aggregates of megafaunal filter feeders and elevated macrofaunal densities. Analysis of videos and still images from the ROV transects also led to the discovery of a number ofVulnerable Marine Ecosystems (VMEs) dominated by sponges and soft corals characteristic of the Arctic region. Directions for future research encompass a more detailed, quantitative study of the megafauna and more coherent sampling over the entire depth range in order to fully capture the diversity of the habitats and biota of the region. The presence of sensitive biogenic habitats, alongside seemingly high biodiversity and naturalness are supportive of ongoing considerations of designating part of the ARS as an “Ecologically and Biologically Significant Area” (EBSA).

Macrobenthic Mollusca of the Prince Gustav Channel, Eastern Antarctic Peninsula: An Area Undergoing Colonisation

In 2018 RRSJames Clark Rossinvestigated the marine benthic biodiversity of the Prince Gustav Channel area which separates the eastern coast of the Antarctic Peninsula from James Ross Island. The southern end of this channel had been covered by the Prince Gustav Ice Shelf until its collapse in 1995. Benthic samples were collected by an epibenthic sledge at six stations (200–1,200 m depth) in the channel and adjacent Duse Bay. In total 20,307 live collected mollusc specimens belonging to 50 species and 4 classes (Solenogastres, Bivalvia, Gastropoda, and Scaphopoda) were identified. The area may be characterised by it’s low species richness (ranging from 7 to 39 species per station) but high abundances (specifically of the Scaphopods with 11,331 specimens). The functional traits of the community were dominated by motile development and mobility type. Assemblage analyses of the molluscan species abundances within the Prince Gustav Channel stations sit distinct, with no pattern by depth or location. However, when bivalve assemblages were analysed with reference to the wider Weddell Gyre region (15 stations from 300 to 2,000 m depth), the Prince Gustav Channel sits distinct from the other Weddell Gyre stations with a higher dissimilarity between the deeper or more geographically distant areas. The Prince Gustav Channel is undergoing colonisation following the recent ice shelf collapse. With many Antarctic ice shelves threatened under climate warming, this area, with future monitoring, may serve as a case study of benthic faunal succession.

Restoration experiments in polymetallic nodule areas.

Deep‐seabed polymetallic nodule mining can have multiple adverse effects on benthic communities, such as permanent loss of habitat by removal of nodules and habitat modification of sediments. One tool to manage biodiversity risks is the mitigation hierarchy, including avoidance, minimization of impacts, rehabilitation and/or restoration, and offset. We initiated long‐term restoration experiments at sites in polymetallic nodule exploration contract areas in the Clarion‐Clipperton Zone that were (i) cleared of nodules by a preprototype mining vehicle, (ii) disturbed by dredge or sledge, (iii) undisturbed, and (iv) naturally devoid of nodules. To accommodate for habitat loss, we deployed >2000 artificial ceramic nodules to study the possible effect of substrate provision on the recovery of biota and its impact on sediment biogeochemistry. Seventy‐five nodules were recovered after eight weeks and had not been colonized by any sessile epifauna. All other nodules will remain on the seafloor for several years before recovery. Furthermore, to account for habitat modification of the top sediment layer, sediment in an epibenthic sledge track was loosened by a metal rake to test the feasibility of sediment decompaction to facilitate soft‐sediment recovery. Analyses of granulometry and nutrients one month after sediment decompaction revealed that sand fractions are proportionally lower within the decompacted samples, whereas total organic carbon values are higher. Considering the slow natural recovery rates of deep‐sea communities, these experiments represent the beginning of a ~30‐year study during which we expect to gain insights into the nature and timing of the development of hard‐substrate communities and the influence of nodules on the recovery of disturbed sediment communities. Results will help us understand adverse long‐term effects of nodule removal, providing an evidence base for setting criteria for the definition of “serious harm” to the environment. Furthermore, accompanying research is needed to define a robust ecosystem baseline in order to effectively identify restoration success. Integr Environ Assess Manag 2022;18:682–696. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Macroecology of Southern Ocean benthic Ostracoda (Crustacea) from the continental margin and abyss

Abstract The Southern Ocean (SO) is the least understood environment on earth, but anthropogenic impacts related to climate change, fishing activities and tourism are already well-established in the region. Herein, we investigate biodiversity patterns in the Atlantic Sector of the SO by investigating a considerable number of samples collected from a wide depth range (89–6224 m). Three topics are addressed: (1) which taxa occur in the SO; (2) if there are distinct shelf, slope and abyssal faunas; and (3) which abiotic parameters explain the ostracod assemblages. We also tested putative ecological preferences of ostracod genera, widely used in palaeoceanographical reconstruction. For this, almost 5000 living ostracods from 51 epibenthic sledge samples were identified to 140 species. Statistically significant differences were observed among the faunas from the shelf, slope and abyssal faunas, indicating that the shelf fauna survived in refugia during the glacial periods of the Quaternary. Our analyses showed that the main variables influencing ostracod distribution is depth, followed by nitrate and phosphate. Temperature, salinity and oxygen content do not seem to be as important as previously proposed. Putative ecological preferences of ostracod genera, for example, low oxygen for Cytherella, could not be confirmed, suggesting that this topic requires further investigation.

The Discovery and Preliminary Geological and Faunal Descriptions of Three New Steinahóll Vent Sites, Reykjanes Ridge, Iceland

During RVMS Merianexpedition MSM75, an international, multidisciplinary team explored the Reykjanes Ridge from June to August 2018. The first area of study, Steinahóll (150–350 m depth), was chosen based on previous seismic data indicating hydrothermal activity. The sampling strategy included ship- and AUV-mounted multibeam surveys, Remotely Operated Vehicle (ROV), Epibenthic Sledge (EBS), and van Veen grab (vV) deployments. Upon returning to Steinahóll during the final days of MSM75, hydrothermal vent sites were discovered using the ROV Phoca (Kiel, GEOMAR). Here we describe and name three new, distinct hydrothermal vent site vulnerable marine ecosystems (VMEs); Hafgufa, Stökkull, Lyngbakr. The hydrothermal vent sites consisted of multiple anhydrite chimneys with large quantities of bacterial mats visible. The largest of the three sites (Hafgufa) was mapped, and reconstructed in 3D. In total 23,310 individual biological specimens were sampled comprising 41 higher taxa. Unique fauna located in the hydrothermally venting areas included two putative new species of harpacticoid copepod (Tisbesp. nov. andAmphiascussp. nov.), as well as the spongeLycopodina cupressiformis(Carter, 1874). Capitellidae Grube, 1862 and Dorvilleidae Chamberlin, 1919 families dominated hydrothermally influenced samples for polychaetes. Around the hydrothermally influenced sites we observed a notable lack of megafauna, with only a few species being present. While we observed hydrothermal associations, the overall species composition is very similar to that seen at other shallow water vent sites in the north of Iceland, such as the Mohns Ridge vent fields, particularly with peracarid crustaceans. We therefore conclude the community overall reflects the usual “background” fauna of Iceland rather than consisting of “vent endemic” communities as is observed in deeper vent systems, with a few opportunistic species capable of utilizing this specialist environment.

Diversity of Deep-Sea Scale-Worms (Annelida, Polynoidae) in the Clarion-Clipperton Fracture Zone

The polymetallic nodules lying on the seafloor of the Clarion-Clipperton Fracture Zone (CCFZ) represent over 30 billion metric tons of manganese. A single mining operation has potential to directly impact approximately 200 km2 of the seabed per year. Yet, the biodiversity and functioning of the bentho-demersal ecosystem in the CCFZ remain poorly understood. Recent studies indicate a high species diversity in a food-poor environment, although the area remains poorly sampled. Undersampling is aggravated by a combination of low densities of fauna and high habitat heterogeneity at multiple spatial scales. This study examines the Polynoidae, a diverse family of mobile polychaetes. Sampling with an epibenthic sledge and a remotely operated vehicle was performed during the cruise SO239 within the eastern CCFZ. Five areas under the influence of a sea surface productivity gradient were visited. Specimens were identified using morphology and DNA: (i) to provide a more comprehensive account of polynoid diversity within the CCFZ, (ii) to infer factors potentially driving alpha and beta diversity, and (iii) to test the hypothesis that epibenthic polychaetes have low species turnover and large species range. Patterns of species turnover across the eastern CCFZ were correlated with organic carbon fluxes to the seafloor but there was also a differentiation in the composition of assemblages north and south of the Clarion fracture. In contrast to the previous studies, patterns of alpha taxonomic and phylogenetic diversity both suggest that polynoid assemblages are the most diverse at Area of Particular Environmental Interest no. 3, the most oligotrophic study site, located north of the Clarion fracture. Without ruling out the possibility of sampling bias, the main hypothesis explaining such high diversity is the diversification of polynoid subfamily Macellicephalinae, in response to oligotrophy. We propose that macellicephalins evolved under extremely low food supply conditions through adoption of a semi-pelagic mode of life, which enabled them to colonise new niches at the benthic boundary layer and foster their radiation at great depths.

Drivers of abundance and spatial distribution in Southern Ocean peracarid crustacea

The Southern Ocean (SO) continental shelf and deep sea are environments characterised by different benthic communities. Their structure and composition are driven and shaped by different variables: whilst on the continental shelf physical environmental variables are the main drivers shaping faunal abundance, structure and composition, the deep-sea fauna is most problably driven by biological variables such as predation and competition. Among shelf and deep-sea benthic communities, peracarids (e.g. amphipods and isopods) are one of the most dominant groups, showing high levels of abundance and diversity in both environments. Knowledge on their assemblage structure and composition in the SO remains limited, as well as the knowledge of the environmental variables that influence them. Therefore, the aim of our study was to investigate peracarid assemblages from the SO continental shelf and deep sea and to assess the main drivers shaping their assemblage structure along a wide bathymetric gradient (from 160 m to about 6000 m depth) and at a large geographic scale. We analysed the spatial distribution of 183,606 peracarids sampled using an epibenthic sledge (EBS) during nine different expeditions in the SO, covering a latitudinal range of 77° to 41° South. Depth was identified as the main driver shaping peracarid abundance pattern, their assemblage structure from the continental shelf (<1499 m) was dissimilar to that from the deep sea (>1500 m). Also, depth was differently correlated with different peracarid orders: while isopod abundances increased with depth, amphipods and mysids were negatively correlated; no correlation was found with cumaceans and tanaidaceans. The dissimilar peracarid assemblage structure between the SO continental shelf and the SO deep sea can be due to the assumption that there are different driving forces shaping benthic assemblages from these two environments (physical variables on the continental shelf, biological interactions in the deep sea). As a result, we also suggest that environmental changes due to climate change (e.g. temperature, ice coverage, productivity) would have different consequences depending on the bathymetric range considered.

Long-term and seasonal changes in the life-history biology of the abyssal holothurian Pseudostichopus aemulatus from the Porcupine Abyssal Plain (North-East Atlantic)

Long-term interannual variations in the benthic community structure are well-known from abyssal plains in the North Atlantic and North Pacific, where rapid responses to changes in the environment by first-order opportunists modify overall species composition. To increase our knowledge of the long-term variations of deep-sea benthic communities in the North-East Atlantic, we studied the response of a second-order opportunist echinoderm, the holothurian Pseudostichopus aemulatus, before, during and after the “Amperima Event” – a four-year episode (1996–1999) where the first-order opportunistic holothurian, Amperima rosea, increased dramatically in density. We used a collection of 14 sampling times of deep-sea community assemblage over a sixteen-year period to understand the temporal variation (i.e., interannual and seasonal) in population structure (i.e., density and individual sizes) and reproduction (i.e., mean oocyte sizes, sex ratios, gonadal indices, and fecundity) in P. aemulatus. Samples were collected from the Porcupine Abyssal Plain (PAP) in the NE Atlantic Ocean at a depth of ca. 4850 m between 1989 and 2005 with a semi-balloon otter trawl (OTSB14) and an epibenthic sledge (BN1.5/C) at varying seasons. We measured individual body size, dissected organisms to prepare histological slides of their gonads, and measured the Feret oocyte diameter in females. We found changes in the life-history biology of P. aemulatus during the “Amperima Event”. Population density increased gradually from September 1997 until April 1999, when P. aemulatus reached a peak in density coinciding with the smallest mean body size observed (1998 and 1999) suggesting recruitment of juveniles. In 1997, before these changes in population structure, mean oocyte sizes were at their largest, suggesting a strong reproductive effort with individuals either preparing to spawn or spawning. This reproductive effort was minimal in the years after 1999, when we found the largest proportions of previtellogenic oocytes in individuals that were probably allocating their energy into growth rather than reproduction given their smaller size. The presence of gametes of all sizes across seasons and a broad range of individual sizes in various sampling times suggests no seasonal reproductive patterns. We suggest that feeding guild differences between various holothurian species explain the diverse life-history responses observed among holothurians competing for resources in a food-poor environment.

Adult life strategy affects distribution patterns in abyssal isopods – implications for conservation in Pacific nodule areas

Abstract. With increasing pressure to extract minerals from the deep-sea bed, understanding the ecological and evolutionary processes that limit the spatial distribution of species is critical to assessing ecosystem resilience to mining impacts. The aim of our study is to gain a better knowledge about the abyssal isopod crustacean fauna of the central Pacific manganese nodule province (Clarion–Clipperton Fracture Zone, CCZ). In total, we examined 22 epibenthic sledge (EBS) samples taken at five abyssal areas located in the central northern Pacific including four contracting areas and one Area of Particular Environmental Interest (APEI3). Additional samples come from the DISturbance and reCOLonization experiment (DISCOL) area situated in the Peru Basin, southeastern Pacific. Using an integrative approach that combined morphological and genetic methods with species delimitation analyses (SDs) we assessed patterns of species range size, diversity, and community composition for four different isopod families (Munnopsidae Lilljeborg, 1864; Desmosomatidae Sars, 1897; Haploniscidae Hansen, 1916; and Macrostylidae Hansen, 1916) displaying different dispersal capacities as adults. Isopods are brooders, so their distribution and connectivity cannot be explained by larval dispersal but rather by adult locomotion. In particular, our objectives were to (1) identify potential differences in the distributional ranges of isopod families relative to their locomotory potential and to (2) evaluate the representativeness of the APEI for the preservation of regional biodiversity in the CCZ following mining disturbances. From 619 specimens, our SD analysis could distinguish 170 species, most of which were new to science (94.1 %). We found that increased locomotory ability correlated with higher species diversity with 9 species of Macrostylidae, 23 of Haploniscidae, 52 of Desmosomatidae, and 86 of Munnopsidae. This is supported by family-level rarefaction analyses. As expected, we found the largest species ranges in the families with swimming abilities, with a maximum recorded species range of 5245 and 4480 km in Munnopsidae and Desmosomatidae, respectively. The less motile Haploniscidae and Macrostylidae had maximal species ranges of 1391 and 1440 km, respectively. Overall, rarefaction analyses indicated that species richness did not vary much between areas, but the real number of species was still not sufficiently sampled. This is also indicated by the large proportion of singletons (40.5 %) found in this study. The investigated contractor areas in the CCZ were more similar in species composition and had a higher proportion of shared species between each other than the closely located APEI3 and the distantly located DISCOL area. In fact, the DISCOL area, located in the Peru Basin, had more species in common with the core CCZ areas than APEI3. In this regard, APEI3 does not appear to be representative as serving as a reservoir for the fauna of the investigated contractor areas, at least for isopods, as it has a different species composition. Certainly, more data from other APEIs, as well as preservation reference zones within contractor areas, are urgently needed in order to assess their potential as resources of recolonization of impacted seabed.

Abundance and Distributional Patterns of Benthic Peracarid Crustaceans From the Atlantic Sector of the Southern Ocean and Weddell Sea

Climate change is influencing some environmental variables in the Southern Ocean (SO) and this will have an effect on the marine biodiversity. Peracarid crustaceans are one of the dominant and most species-rich groups of the SO benthos. To date, our knowledge on the influence of environmental variables in shaping abundance and species composition in the SO’s peracarid assemblages is limited, and with regard to ice coverage it is unknown. The aim of our study was to assess the influence of sea ice coverage, chlorophyll-a, and phytoplankton concentrations on abundance, distribution and assemblage structure of peracarids. In addition, the influence of other physical parameters on peracarid abundance was assessed, including depth, temperature, salinity, sediment type, current velocity, oxygen, iron, nitrate, silicate and phosphate. Peracarids were sampled with an epibenthic sledge (EBS) in different areas of the Atlantic sector of the SO and in the Weddell Sea. Sampling areas were characterized by different regimes of ice coverage (the ice free South Orkney Islands, the seasonally ice-covered Filchner Trough and the Eastern Antarctic Peninsula including the Prince Gustav Channel which was formerly covered by a perennial ice shelf). In total 64766 individuals of peracarids were collected and identified to order level including five orders: Amphipoda, Cumacea, Isopoda, Mysidacea, and Tanaidacea. Amphipoda was the most abundant taxon, representing 32% of the overall abundances, followed by Cumacea (31%), Isopoda (29%), Mysidacea (4%), and Tanaidacea (4%). The Filchner Trough had the highest abundance of peracarids, while the South Orkney Islands showed the lowest abundance compared to other areas. Ice coverage was the main environmental driver shaping the abundance pattern and assemblage structure of peracarids and the latter were positively correlated with ice coverage and chlorophyll-a concentration. We propose that the positive correlation between sea ice and peracarid abundances is likely due to phytoplankton blooms triggered by seasonal sea ice melting, which might increase the food availability for benthos. Variations in ice coverage extent and seasonality due to climate change would strongly influence the abundance and assemblage structure of benthic peracarids.

Diversity and composition of benthic asellote Isopoda from two different New Zealand continental margin habitats - implications of habitat heterogeneity, productivity and depth

As part of the New Zealand government Ocean Survey 20/20 programme (OS 20/20, 2006–2013), samples from the Chatham Rise and Challenger Plateau collected in 2007 were analysed to determine the effects of key environmental parameters, in particular sediment and water mass properties, on spatial changes in the community structure (abundance, diversity and community composition) of bathyal asellotan isopods. Benthic collections were obtained in austral autumn (May/June 2007) and included a total of 21 epibenthic sledge samples taken from the upper slope between 218 and 1239 m. Due to the contrasting environmental settings between the Chatham Rise and Challenger Plateau, in terms of surface productivity and habitat heterogeneity, we expected the abundance, regional (or gamma-) diversity and community composition of benthic isopods to significantly differ between the two regions, and furthermore local (or alpha-) diversity and abundance (density) to decrease with increasing depth. Consistent with our assumptions, multivariate PERMANOVA analysis revealed a clear distinction in species composition between the Chatham Rise and Challenger Plateau with satellite surface chlorophyll (Chl) a and bottom temperature being the main environmental drivers. In contrast to previous benthic studies from the same sampling campaign, however, differences in isopod density and diversity between the two regions were not significant, either at species, or generic and family level. In addition, no depth-related changes in abundance and diversity could be observed at any hierarchical level. Instead, isopod densities at species and generic level were positively correlated with satellite surface Chl a and %silt, whilst species and generic diversity could be positively linked to the amount of total organic matter (TOM) in surficial sediments. In total, 97 asellote species in 54 genera and 15 families could be identified from both regions, of which 90.7% were likely new species. Species diversity was average to high when compared to other regions in the Northern and Southern hemispheres. However, neither for Chatham Rise nor for the Challenger Plateau did the species accumulation curves reach an asymptote, indicating that additional samples are required to provide more robust diversity estimates.

Munnopsidae (Crustacea, Isopoda, Asellota) from the Kuril–Kamchatka Trench with a regional and inter-ocean comparison of their biogeographic and richness patterns

The benthos of the Kuril–Kamchatka Trench (KKT) was sampled during the KuramBio II expedition on board the RV Sonne in 2016. Macrobenthos was, for the first time, collected in the KKT hadal zone using an epibenthic sledge. Isopod crustaceans were one of the dominant taxa, and Munnopsidae was the most abundant and diverse asellotan family, comprising 49% of all Isopoda. During the expedition, a total of 67 species of 24 genera from eight subfamilies of Munnopsidae were collected, including 41 species of 15 genera from 18 hadal stations. In general, the taxonomic diversity of the munnopsid fauna in the KKT hadal zone was lower than that of the Northwest Pacific (NWP) abyssal fauna adjacent to the KKT. Two subfamilies, Lipomerinae and Acanthocopinae, were not found in the hadal zone. Most of all collected munnopsid individuals (92%) belonged to the three subfamilies: Eurycopinae (42%; 15 species), Betamorphinae (33%; four species), and Storthyngurinae (17%; two species). The rest of all munnopsid individuals (8%) belonged to the subfamilies Ilyarachninae, Munnopsinae, Syneurycopinae, and to a group of incertae sedis genera. The eight most numerous species representing the three most widely distributed and speciose genera—Eurycope, Betamorpha and Rectisura—encompassed 78% of all munnopsid individuals. The study of the Munnopsidae collected during the four expeditions (SoJaBio in 2010, KuramBio in 2012, SokhoBio in 2015 and KuramBio II in 2016) extended the known diversity of the munnopsid species in the KKT area from 39 described species of 14 genera to 157 species of 36 genera. Most collected species (87%) were new to science. The fauna richness showed a tendency to decrease from the open abyssal towards the hadal zone of the KKT and towards the semi-isolated abyssal Kuril Basin of the Sea of Okhotsk, and especially towards the more isolated abyss of the Sea of Japan. A comparison of the munnopsids from NWP and those from other oceans showed their similar composition with the same dominant subfamilies. The main difference between the abyssal munnopsids from the NWP and from the Atlantic sector of the Southern Ocean was the proportion of the Lipomerinae (2% vs. 16% of munnopsid individuals, respectively). A trend of reduction in the munnopsid diversity from abyssal to hadal depths, similar to that in the KKT, was also revealed in the Puerto-Rico Trench.

Tanaidacean faunas of the Sea of Okhotsk and northern slope of the Kuril-Kamchatka Trench

The Sea of Okhotsk is one of the world’s largest marginal seas; its benthic fauna, especially from deeper parts, remains virtually unexplored. The material for this study was collected in the Sea of Okhotsk, Bussol Strait, and from the northern slope of the Kuril-Kamchatka Trench, during the Russian-German expedition Sea of Okhotsk Biodiversity Studies (SokhoBio) onboard the RV Akademik M.A. Lavrentyev in 2015. Material was collected using a camera-equipped epibenthic sledge (C-EBS). Forty-six tanaidacean species representing 31 genera and 12 families were found in 19 samples collected at depths from 1696 to 4798 m. All the species were new to science. The highest number of species (44) was recorded in the deepest part of the Sea of Okhotsk (Kuril Basin), followed by the northern slope of the Kuril-Kamchatka Trench (16 species) and the Bussol Strait (3 species). Almost one-third of all tanaidaceans (14 species) were common to both sides of the Kuril Island archipelago. Our results reveal a substantial faunal exchange between those two areas, although the small number of samples makes final conclusions about faunal similarity between the Sea of Okhotsk and the Pacific Ocean not fully possible. The level of rarity and patchiness of the tanaidacean fauna was high. The large number of species and individuals per sample observed in the Sea of Okhotsk might reflect high food availability in this area.

Deep-sea amphipod fauna of the Sea of Okhotsk

During joint Russian-German SokhoBio expedition held in 2015, the deepest area of the Sea of Okhotsk (Kuril Basin), the Bussol Strait and the western abyssal slope of the Kuril-Kamchatka Trench were investigated using camera epibenthic sledge. In total, 19 stations ranged between 1696 and 4798 m depth were sampled. The amphipods constituted 10% of all macroinvertebrates and one fourth of all Peracarida. The identification of families resulted in 32 taxa of which two (Liljeborgiidae and Valettiopsidae) were recorded for the first time from the Sea of Okhotsk. The most abundant group was Corophiida (17.4%), followed by the Oedicerotidae (15.8%), the Phoxocephalidae (12.3%), and the Eusiridae (11.7%). A multivariate analysis carried on the amphipod family abundance data (three stations excluded), discriminated four different assemblages in the studied area: a Bussol Strait assemblage (group A, two stations, 2327–2333 m) dominated by Corophiida group; a Kuril Basin assemblage (group B, 11 stations, 3210–3366 m) characterized by Oedicerotidae and Phoxocephalidae; and two assemblages in the Kuril-Kamchatka Trench area: a single station (group C, 4681 m) dominated by Phoxocephalidae and two grouped stations (group D, 3371–4798 m) characterized by Lysianassoidea. The effect of environmental variables on amphipod taxocenosis was also discussed.