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Understanding fine-grained sediment accumulation is critical for developing robust geologic models and inferring environmental conditions. Here we report on processes that produce compositional layering at the mm and sub-mm scale, with gradational rather than sharp layer boundaries. Sometimes described as fuzzy laminae, this feature occurs in modern muds that accumulate under oxygen-stressed conditions, caused by meiofauna (tiny organisms; benthic foraminifera, polychaetes, nematodes, etc.) that disrupts the original fabric. In the rock record, fuzzy laminae are common in shales that accumulated under presumed oxygen-stressed conditions. Like their presumed modern analogs, ancient examples contain remains of benthic foraminifera and other small benthic organisms that were the likely agents of fabric disruption. As preserved lamination is considered indicative of bottom water anoxia in ancient shales, we need to better understand the cause of fuzzy lamination, because such insights have the potential to allow much refined assessments of the depositional history of laminated organic-rich shales. In experiments, nematode activity blurred the originally sharp contacts between successive sediment layers with contrasting composition. Although nematode activity produces tiny temporary traces aside of blurring of primary fabric, the former have minimal preservation potential due to compaction of the water-rich substrate. Experimental fabrics compare well to those observed in a wide range of ancient black shales, suggesting common meiofaunal activity in the latter. Our findings imply that the details of lamination (fuzzy vs. sharp) in ancient shales are not necessarily controlled by bottom water oxygenation, but instead result from the interplay between sedimentation rates and bottom current activity.

A microcosm experiment was carried out to determine how benzo(a)pyrene (BaP) may affect marine meiofauna community, with a main emphasis on nematode structure and functional traits. Three increasing concentrations of BaP (i.e. 100, 200 and 300 ng/l, respectively) were used for 30 days. The results revealed a gradual decrease in the abundance of all meiobenthic groups (i.e. nematodes, copepods, amphipods, polychaetes and oligochaetes), except for isopods. Starting at concentrations of 200 and 300 ng/l BaP, respectively, significant changes were observed at community level. At taxonomic level, the nematode communities were dominated at the start of the experiment and also after being exposed or not to BaP by Odontophora villoti, explicable through its high ecologic ubiquity and the presence of well-developed chemosensory organs (i.e. amphids), which potentially increased the avoidance reaction following exposure to this hydrocarbon. Moreover, changes in the activity of several biochemical biomarkers (i.e. catalase 'CAT', gluthatione S-transferase 'GST', and ethoxyresorufin-O-deethylase 'EROD') were observed in the nematode species Oncholaimus campylocercoides, paralleled by significant decreases in CAT activity for non-gravid females compared to controls at concentrations of 25 ng/l BaP and associated with significant increase in GST and EROD activities for both types of individuals.

In the framework of an ongoing extensive phylogenetic evaluation of the Ceratonotus group (Copepoda, Harpacticoida, Cletodidae), Poropsyllus menzelae gen. et sp. nov. from the sublittoral of south-western Cyprus (eastern Mediterranean Sea) and Paratouphapleura aaroni gen. et sp. nov. from the western Weddell Sea (Antarctica) are described. Both new species fit the autapomorphies of the Ceratonotus group but cannot be assigned to any of the genera so far known. Instead, each new species presents a set of derived characters that justify their placement in new genera, Poropsyllus gen. nov. and Paratouphapleura gen. nov., respectively. Furthermore, a comparison of the species placed in Ceratonotus Sars revealed that because of exclusive morphological deviations, Ceratonotus concavus Conroy-Dalton, C. steiningeri George, C. tauroides George, and C. vareschii George should be excluded from Ceratonotus and transferred to a new monophylum, Tauroceratus gen. nov. Likewise, Polyascophorus monoceratus George, Wandeness & Santos is characterized by several apomorphies that justify its transfer from Polyascophorus to a new taxon, Pseudopolyascophorus gen. nov. The Ceratonotus group is therefore increased to 31 species assigned to 13 genera. The systematic modifications conducted and resulting phylogenetic consequences are discussed in detail.

Abyssal plains cover more than half of Earth's surface, and the main food source in these ecosystems is phytodetritus, mainly originating from primary producers in the euphotic zone of the ocean. Global climate change is influencing phytoplankton abundance, productivity, and distribution. Increasing importance of picoplankton over diatom as primary producers in surface oceans (especially projected for higher latitudes) is projected and hence altering the quantity of organic carbon supplied to the abyssal seafloor as phytodetritus, consequences of which remain largely unknown. Here, we investigated the in situ responses of abyssal biota from viruses to megafauna to different types of phytoplankton input (diatoms or cyanobacteria which were labeled with stable isotopes) at equatorial (oligotrophic) and temperate (eutrophic) benthic sites in the Pacific Ocean (1°N at 4277 m water depth and 39°N at 5260 m water depth, respectively). Our results show that meiofauna and macrofauna generally preferred diatoms as a food source and played a relatively larger role in the consumption of phytodetritus at higher latitudes (39°N). Contrarily, prokaryotes and viruses showed similar or even stronger responses to cyanobacterial than to diatom supply. Moreover, the response of prokaryotes and viruses was very rapid (within 1-2 days) at both 1°N and 39°N, with quickest responses reported in the case of cyanobacterial supply at higher latitudes. Overall, our results suggest that benthic deep-sea eukaryotes will be negatively affected by the predicted decrease in diatoms in surface oceans, especially at higher latitudes, where benthic prokaryotes and viruses will otherwise likely increase their quantitative role and organic carbon cycling rates. In turn, such changes can contribute to decrease carbon transfer from phytodetritus to higher trophic levels, with strong potential to affect oceanic food webs, their biodiversity and consequently carbon sequestration capacity at the global scale.

The Institute of Oceanology of the Polish Academy of Sciences (IO PAN) stores 77,500 natural history specimens from marine areas, which have been collected since 1985, when the Arctic Ecosystem Laboratory was established, later transformed into the Department of Marine Ecology. The majority of the collection is zooplankton (approximately 36,000 specimens) collected during the annual research cruises with the s/y Oceania ship to the area of the Nordic seas. Some smaller collections organized by individual researchers working with specific systematic groups are equally important. Thus, the Institutes collection resources also include specimens of bryozoans (Bryozoa), crustaceans (Crustacea) with a separate collection of hermit crabs (Paguroidea), as well as hydroids (Hydrozoa), bristle worms (Polychaeta), molluscs (Mollusca), sipunculid worms or peanut worms (Sipuncula), and echinoderms (Echinodermata) as well as protists (Protista), meiofauna with separate collections of kinorhynchs, the spiny-crown worms (Kinorhyncha) and nematodes (Nematoda) as well as Antarctic and Gulf of Gdansk macrofauna. As part of the IMBIO project (Integration and mobilization of data on the biotic diversity of Eukaryota in the resources of Polish scientific institutions), the specimen collections currently held by the Institute will be systematized and organized, and the data on resources will be digitalized in the form of metadata databases. The idea of digitizing the data contained in the descriptions of scientific collections and sharing them through the Polish Biodiversity Information Network (KSIB) and the Global Biodiversity Information Facility (GBIF) organizations will facilitate a wider insight and use of previously unavailable scientific collections.

Most previous Black Sea palynology studies have used pollen-spore assemblages as proxies for climate and landscape changes, and dinocyst assemblages as proxies for surface water salinity. However, there are few data on within-region variations in these assemblages using large sets of surface samples and a full suite of palynomorphs, including terrigenous pollen + spores, freshwater algal spores, and organic remains of marine microplankton, micro- and meiobenthos. Here we fill this knowledge gap, using results from a palynological study of 43 surface samples from water depths of 71–905 mbsl on the Ukrainian Shelf and adjoining continental slope, NW Black Sea. The palynology samples were collected in conjunction with water and sediment chemistry data, grain-size, micropaleontological and meiobenthos data from the EU-FP6 project HERMES “Hotspot Ecosystems Research on the Margins of European Seas”. This dataset uniquely covers shelf and upper slope areas east and west of the Odessa-Sinop Fault Zone (OSFZ) that delimits areas of lower and higher hydrocarbon gas contents, respectively. The new data show that on the wide shelf with a shallow (ca. 80 m) oxycline, pollen assemblages differ from classical models for marine pollen transport. On the Ukrainian Shelf, pollen concentrations are extraordinarily high far offshore and the grains are often pyrite-infilled. These features apparently reflect high pollen preservation potential in low oxygen sediments, probably enhanced by cross-shelf transport of land-derived particulate organic matter. The new data have important consequences for accurate modelling of carbon burial and storage in epicontinental seas, and they provide a baseline for evaluating marine pollen concentrations expected to reflect the early Neolithic farming on the Ukrainian shelf. Furthermore, although large concentrations of dinocysts comprise more than half of the total Non-Pollen Palynomorphs (NPP), the high pollen concentrations skew the P:D index (pollen:dinocyst ratio) commonly used to evaluate changes in paleo-shoreline (proxy sea-level) positions. Despite the discharge of several large rivers to the Ukrainian Shelf, there are negligible traces of freshwater algae in the HERMES samples except at Sta. 15 where Pediastrum is abundant. Overall, palynomorphs of terrestrial origin make up about half (52%) of the acid-resistant organic-walled particles on the outer NW Black Sea Shelf and adjacent slope. The abundances of the major micro- and meiobenthic palynomorph groups show the same trends east and west of the OSFZ as the micropaleontological data reported for the HERMES samples taken at the same sites. The combined microzooplankton and zoobenthos surface assemblage data provide an important new baseline for evaluating historical and past changes in biodiversity and aquatic foodweb structure in the now polluted NW Black Sea. Comparison can also be made with foodweb reconstructions for Permian black shales.

The Central American Isthmus has had profound effects on the evolution and distribution of larger marine organisms, but the impacts on meiobenthic animals have received little attention. Tardigrade...

The experimental cultivation of Kappaphycus alvarezii was done to investigate its daily growth rates and biomass yields, and their impacts on planktonic and benthos population densities were evaluated by floating raft culture method. Biomass yields and daily growth rates of K. alvarezii were observed. The phytoplankton and zooplankton densities varied from 25,250 to 319,033 cells/m3 and 12,060 to 207,893 individuals/m3, respectively. Similarly, macrobenthos and meiobenthos densities varied from 11,105 to117061 nos/m2 and 14,740 to 727,000 nos/m2, respectively. The maximum values of plankton and benthos were recorded in the control site compared with the culture sites. Pearson correlation suggests that growth rate of K. alvarezii is negatively correlated with zooplankton density (r = −0.9); macrobenthos (r = −0.9) and meiobenthos density (r = −0.8) at P 0.01). The conclusion suggests that water nutrient declined at both culture sites than control site. So, the plankton and benthic fauna were declined in the culture sites.

The results of the first studies of the ecosystem state of the underwater part of the channel, artificially created in the middle of the 20th century on the western shore of the Balaklava Bay (Sevastopol) as a naval base of the Black Sea Fleet for the submarines repair, are presented. Channel's ecosystem is determined by uniqueness of anthropogenic formation and considered as analogue of natural Black Sea cave. Hydrospelological survey of the channel and biological studies allowed assessing its current state, the nature of biofouling of its walls and anthropogenic and technical pollution of the bottom. Macrofauna of the channel wall biofouling is represented by the Mytilaster lineatus community, which has a high level of species abundance (about 80 species have been registered) and quantitative development. Both in taxonomic diversity and in quantitative terms, this community is comparable to the rocky substrate community near open Crimean coasts, but with a smaller share of crustacean group development. Due to weakened hydrodynamics, well developed fauna of bryozoans forming plurannual crusty structures and single sponges is observed on the channel's walls. In contrast to the channel walls biofouling, its bottom macrofauna has relatively lower quantitative and qualitative composition. Meiobenthos in the channel’s wall biofouling is represented by 18 higher taxa (type, class, order) of Protozoa and Metazoa with predominance of harpacticoids by abundance. Meiobenthos of the soft bottom of underground channel is represented by 15 higher taxa with predominance of free-living nematodes and harpacticoids by abundance. Average density of meiobenthos in the channel’s bottom sediments is comparable with similar parameters of its development in open water areas and Sevastopol bays.

In this study, a microcosm experiment was conducted for 30 days to assess the impact of the presence of juvenile gray shrimp Crangon crangon on meiofauna. The results suggested that juvenile shrimp had a significant negative impact on the abundance of nematodes and copepods, but no effect on polychaetes. Moreover, nematodes showed a significant decline in individual weight. The collected nematodes were taxonomically identified and assigned to five functional traits: shapes of the tail and amphid, life history, feeding types, and adult length. The nematode traits were affected by the number of shrimp introduced, and descriptors followed normal or inversed bell-shaped curves. When no shrimp were present, the nematofauna had a higher species richness compared with treatments of 4, 8, and 12 shrimp. Bell-shaped curve patterns were common in relation to the two phases of feeding for C. crangon. During the first phase, C. crangon consumed the nematode species Oncholaimus campylocercoides; thereafter, shrimp fed mostly on the nematode Anticoma eberthi and copepods.

The intertidal coastline of Ceredigion, Wales, comprises a patchwork of unstable sand and cobble beaches, and stable bedrock areas and boulder-fields. The last two shoreline types support rock-pools with growths of the red alga Corallina officinalis, the thalli of which are a popular substrate for calcareous epiphytes. Replicate samples of C. officinalis (four per site) were taken from (a) three bedrock sites (Ceinewydd, Aberystwyth Victoria Rocks and Castle Rocks) and (b) three boulder-fields (Llanon, Aberaeron lower shore (Aberaeron LS), Llanina) on the lower shore. The middle shore boulder field at Aberaeron (Aberaeron MS) was also sampled. These replicates were examined for calcareous meiofauna (63–2000 μm) not previously examined as a community: spirorbids, foraminifera, gastropods, bryozoans, ostracods and ophiuroids. These were assigned to sessile and vagile modes of life. The sessile association overwhelmingly dominated bedrock coastlines and the Aberaeron MS, while the vagile association was at its most abundant on the Corallina from lower shore, stable boulder-fields. Gastropods were almost entirely limited to Corallina on boulder-fields. We hypothesize that the boulders induce low-energy turbulence among breaking waves, allowing the less firmly attached vagile meiofauna to dominate on C. officinalis in rock-pools in lower shore boulder-fields. The small attachment area of sessile organisms allows them to settle bedrock sites in greater densities than do vagile organisms at boulder-field sites, which are presumed to require larger foraging areas.

Five new species of the genus Sarsamphiascus Huys, 2009 were collected from a small Korean beach, which is a record for the number of syntopic copepod congeners. They differ in numerous macro-morphological characters, some of which extend generic boundaries, and are classified in two species groups. Diossacins are widely regarded as taxonomically problematic, and the new discovery presents an opportunity to test characters commonly used in their systematics through a cladistic analysis. Another aim is to test with landmark-based geometric morphometrics the extent of inter- and intraspecific variability of characters with reported significant variation but commonly used in diosaccin taxonomy. The cladistic analysis, based on 14 binary characters, reveals at least three distinct clades among five new species, which, in addition to significant size differences, probably facilitates their syntopy. Some characters previously used to distinguish species groups in Sarsamphiascus, and to distinguish this genus from other diosaccins, are exposed as symplesiomorphies, suggesting that some of these groups might not be monophyletic. Studies of alternative characters are suggested, including cuticular organs on somites, which are surveyed for the first time in this genus. Principal component analysis (PCA) of nine landmarks on the female fifth leg exopod reveals that 70% of variability can be explained by the first two eigenvectors and that in morphospace there is no overlap between Korean species, despite a significant intraspecific variability. Discriminant function analysis with cross-validation shows highly significant results, both in parametric tests and after 10,000 permutation runs, correctly classifying all specimens for all species pairs and suggesting the fifth leg exopod as an ideal taxonomic character here. Evolutionary integration of the morphometric data is tested by plotting PCA scores onto the cladistic tree; randomized permutation test suggests an absence of statistically significant phylogenetic signal. http://www.zoobank.org/urn:lsid:zoobank.org:pub:31913865-E23D-4E76-97B0-2F6D791E717A

A new species of Aegisthidae (Copepoda, Harpacticoida) is described from the upper subtidal of the western coast of the Isla Grande de Tierra del Fuego (Chile). Frisia magellanica gen. et sp. nov. ...

A marine heterotardigrade Cyaegharctus kitamuraigen. et sp. nov. (Arthrotardigrada, Styraconyxidae) is described from Daidokutsu, a submarine cave off Iejima island, Okinawa Islands, Ryukyu Archipelago, Japan. It is easily distinguished from all other styraconyxids by its pocket organs (putative sensory structures) on all legs in addition to the usual leg sensory organs. Its combination of other character states, such as the dorso-ventrally flattened body, ovoid primary clavae, conical secondary clavae, large terminal anus, internal digits with proximal pads and peduncles, external digits with developed peduncles and all digits with three-pointed claws in adult female, supports the erection of a new genus and species.

The exotic species Spartina alterniflora (S. alterniflora) seriously threatens the stability and functioning of saltmarsh ecosystems in the Yangtze Estuary. Ambitious efforts have been undertaken to control this species, but subsequent re-invasion is frequent, presenting a significant barrier to restoration. The complexity and high cost of integrated physical control programs has necessitated a shift in focus, leading to considerable attention being paid to the potential of herbicides to control S. alterniflora. To find a strategy for emergency control of small and scattered patches of re-invading S. alterniflora, an in situ field experiment using Gallant (Haloxyfop-R-methyl) herbicide was conducted. The growth parameters of plant density and height were used to evaluate the control efficiency of different treatment dosages and times and sediment samples were taken for environmental toxicity analysis. The results show the following: (1) the control efficacy of the maximum proposed application dose (2.70 g/m2) was 92% for continuous swards and 100% for small patches, while those of other dosages (0.45 g/m2, 0.90 g/m2, and 1.35 g/m2) were lower than 40%; (2) the appropriate implementation time was July to August with 100% mortality resulting from a single application, while S. alterniflora was shown to be capable of recovering rapidly after treatment in May; and (3) there were no significant differences in the community structure of meiofauna among the herbicide treatments and the control, and no herbicide residues were detected in sediment samples collected from treatment areas. This chemical control method was implemented in the Shanghai Chongming Dongtan National Bird Nature Reserve (CDNR). The results of this study indicate that Gallant is an environmentally friendly herbicide with high efficiency, which can be adopted for emergency control of re-invading S. alterniflora.

Gastrotricha is poor known phylum of small metazoans. Information about Ukrainian gastrotrichs’ fauna is old. In total 9 species are reported in this paper. Chaetonotus (Hystricochaetonotus) hystrix, Chaetonotus (Primochaetus) heideri,Chaetonotus (Zonochaeta) bisacer, Lepidodermella minor minor, Lepidodermella squamata, Ichthydium maximum and Haltidytes festinans are new to the Ukraine fauna. This investigation is giving also additional information for Chaetonotus (Chaetonotus) maximus, Chaetonotus(Hystricochaetonotus) macrochaetus, which have been previously reported to the Ukraine fauna but are new for Kharkiv oblast. We provide short description of all species and some ecology aspects.

For the first time, features of the formation of the total number and biomass of permanent members and temporary members) of meiobenthos in periphyton of natural stony substrates are described for the shelf of the northwestern part of the Black Sea. The material for the scientific analysis was quantitative samples collected during 2012, 2014, and 2015. On two polygons of the North-Western shelf of the Black Sea in the coastal zone of Odessa Bay in the area of the Hydrobiological Station ONU I.I. Mechnikov. Representatives of the following large meiobenthos taxa were found on a stony substrate at a depth of 3–10.7 m: Foraminifera, Nematoda, Ostracoda, Harpacticoida, Halacaridae, Turbellaria, Oligochaeta, young Polychaeta, Bivalvia, Balanus, Amphipod, Cumidae, Crayfish. Kinohryncha and Gastrotricha were absent. The species composition of the main meobenthic groups (Nematoda, Harpacticoida and the young Polychaeta) and their numbers are given. Indicators of the total abundance of meiofauna in the periphyton of the stony substrate varied from 59000 to 341500 ind.·m-2 (average density 156107 ind.·m-2), which was dominated by eumeiobenthos, making up 64% of the total number of organisms. At 57% of the stations studied, representatives of the meiobenthos of the harpacticoids dominated in the density of the settlements, which accounted for 53.2–80% of the total number of organisms. Polychaetes belonging to meiobenthos were unevenly distributed in fouling of a stony substrate. Their average number was 18786 ind.·m-2, an average of 12.7% of the total number of organisms. The share of nematodes in the total number of stones was 20%. Their average density is 23,864 ind.·m-2. Studies have shown that the biodiversity of the meiobenthic community of organisms in the periphyton of natural stony substrates is much poorer than on the loose soils of the adjacent water areas.

Macroalgae produce several allelopathic substances, including polyunsaturated aldehydes (PUAs), which may inhibit photosynthesis and growth rates of other algal species, and grazing. Additionally, macroalgal structural complexity is an important factor in determining abundance patterns and size structure of epiphytic organisms. In this study the PUAs production of two Mediterranean macroalgae, Dictyopteris polypodioides, (DP, Phaeophyceae, Dictyotales) and Cystoseira compressa (CC, Phaeophyceae, Fucales), was characterized to clarify the relationships between the meiobenthic and microphytobenthic communities. Results showed a higher PUAs production and a diverse qualitative profile for DP, which reported long-chain compounds (i.e. C14-C16) as main aldehydes, than CC, with the short-chain C6:2 as the main compound, as well as variability among sampling times. A clear separation of the meiofauna and microphytobenthos assemblages was found for the macroalgae, but with different temporal trends. Dissimilarities were due to five microalgal orders, namely Naviculales, Lyrellales, Gonyaulacales (i.e. Ostreopsis), Bacillariales, and Licmophorales, and to the meiofaunal groups nematodes, copepods, and copepod nauplii, which were more abundant on DP than on CC. Results indicate that macroalgal complexity is a major determinant of the meiofaunal community structure (accounting for 26% of the variation), rather than PUAs production itself (17%). PUAs effects seem species-specific, thus affecting some grazers instead of the entire community. Conversely, microphytobenthos affected the meiofauna assemblages, particularly harpacticoids, confirming the role of these organisms as the primary food source of all marine food chain producers. Since PUAs are produced also by several epiphytic diatoms, the understanding of their effects on the community structure and on the relationships among taxa in the field is complicated and requires further in-depth investigations in simplified systems (i.e. microcosms).

In various biotopic groups of invertebrates of small rivers, the species richness and nematode abundance vary. Periphyton is poorer than meiobenthos. Along with common species, a number of worms are found only in biofouling or only in meiobenthos. A significant increase in species richness, diversity of ecological groups, and abundance of worms in meiobenthos and periphyton of small rivers is observed in zones contaminated with organic substances of anthropogenic and zoogenic origin. The biocenotic and functional role of nematodes in these groups depends to a higher extent on the level of food availability than on a number of other environmental factors that limit their development.

Stable isotope tracer addition can enhance the isotopic differences of primary producers for a wider food-web resolution than the use of natural abundance stable isotopes (NASIs) alone, particularly in ecosystems where primary producers have similar NASI values. To investigate the food sources and the trophic status of benthic infauna in an intertidal area near a Halophila minor seagrass bed within inner Tai Tam Bay, Hong Kong, China, a 15N addition experiment was conducted, and the results were compared with those from NASI data. Only benthic microalgae (BMA) were labeled by applying 15N-enriched NH4Cl to the sediment daily for the first 7 days during a 21-day study. In contrast to the NASI results, Bayesian mixing models based on the isotope tracer experiment suggested a larger dietary contribution of BMA for nematode Daptonema sp. and copepods, whereas a higher reliance on phytoplankton and seagrass detritus was noted for polychaete Neanthes sp. However, both NASI and isotope tracer addition demonstrated that seagrass detritus was a major food source for nematode Spilophorella sp. The present isotope tracer experiment also revealed a contrasting result of the relatively lower contribution of meiofauna in the diets of carnivores/omnivores as compared to the results of NASIs. This finding suggested that the isotope values in these consumers may have not reached an equilibrium with the added isotope in the study period. Thus, there is a need for applying NASI coupled with isotope tracer addition in the investigation of ecosystems in which primary producers have similar isotope values, especially in ecosystems with lower tissue turnover rates, in order for a more accurate determination of dietary contribution and trophic status of consumers in the food-web study.

India has a long history of research on freshwater and marine Gastrotricha. In more than 110 years of study on Order Chaetonotida, two families consisting of 11 genera and 39 species have been described. Thirty of these species are taxa originally described from other continents, while only nine species (7 freshwater, 2 marine) are only known from India. The large percentage (77%) of so-called cosmopolitan species in India has contributed to the phenomenon known as the “meiofauna paradox”. However, a careful review of the pertaining literature provides a different biogeographical picture of the chaetonotidan fauna of India. Herein we show that the high incidence of European and North American species reported from India is mainly due to a mixture of misidentification and species lumping. In fact, for only 12 species there are enough data that would make the Indian specimens morphological similar to taxa previously reported from Europe and/or North America. However, without the appropriate molecular sequence data for comparison, there is no way to rule out the possibility of cryptic speciation.We conclude that further sampling throughout India and the use of more powerful microscopical techniques (e.g., DIC optics) and molecular sequencing will reveal more species and improve the quality of re-descriptions of those (9 spp.) that so far appear to be endemic to the subcontinent. Here we recommend six species to be excluded from the fauna of India while another 11 species (non endemic to India) should be considered dubitatively present in the Indian fauna.

Summary ‘Who eats whom?’ is a fundamental question about the ecological roles and interactions of deep-sea organisms. However, the tools needed to analyze trophic relationships remain limited, especially with regard to studying meiofauna and small macrofauna in abyssal and hadal depths. We present results from indirect molecular analyses of the gut contents of abyssal and hadal Solenogastres (Mollusca, Aplacophora) of the Northwest Pacific. Our data revealed a high food specialization and a surprising diversity of food sources among these inconspicuous worm-shaped predators. We hypothesize that Hydrozoa forms the ancestral food source of Solenogastres, and that specialization on non-cnidarian prey (such as annelids, nemerteans, and bivalves) evolved independently along with modifications in the digestive tract. Despite being intuitively advantageous in the nutrient-limited deep sea, we found only one widespread generalist feeder (potentially associated with scavenging).

Information about invertebrates in the low-flow water bodies of northeastern Siberia is far from complete. In particular, little is known about crustaceans—one of the main components of meiobenthic and zooplanktonic communities. An open question is which environmental factors significantly affect the crustaceans in different taxonomic and ecological groups? Based on the data collected on the zooplankton and meiobenthos in the tundra ponds in the southern part of the Lena River Delta, analysis of the crustacean taxocene structure was performed. In total, 59 crustacean species and taxa were found. Five of these are new for the region. The species richness was higher in the large thermokarst lakes than in the small water bodies, and the abundance was higher in small polygonal ponds than in the other water bodies. Variations in the Cladocera assemblages were mainly affected by the annual differences in the water temperature, non-harpacticoid copepods were generally determined by hydrochemical factors, and for Harpacticoida, the macrophyte composition was significant. Three types of the crustacean assemblages characteristic of different stages of tundra lake development were distinguished. The hypothesis that the formation of crustacean taxocenes in the Lena River Delta is mainly determined by two types of ecological filters, temperature and local features of the water body, was confirmed.

Benthic foraminiferal research in the North Pacific has a long history, with works published over a century ago providing important information about the taxonomy and distribution of morphospecies. These studies focused mainly on areas outside the Clarion-Clipperton Zone (CCZ). Our knowledge of foraminiferal faunas within the CCZ originates largely from recent baseline investigations related to likely future seabed mining of the polymetallic nodule deposits. These have revealed highly diverse assemblages of sediment-dwelling morphospecies among the meiofauna and macrofauna, as well as megafaunal xenophyophores and nodule-attached fauna. Morphological analyses have been complemented by metabarcoding studies that yielded even higher numbers of molecular species (Operational Taxonomic Units - OTUs). Monothalamids, the vast majority undescribed, constitute a substantial proportion of both morphological and molecular datasets, with multichambered agglutinated and calcareous foraminifera being less common. Their importance in this abyssal (>4,000 m depth) habitat likely reflects food limitation combined with carbonate dissolution close to and below the carbonate compensation depth. Literature records, supported in a few cases by genetic data, suggest that many morphospecies found in the CCZ have wide geographical distributions across the Pacific abyss and in other oceans. At smaller spatial scales (several 100s of kilometers) there is a general uniformity in assemblage composition. Nevertheless, many morphospecies are too rare to conclude anything about their geographical distributions. Similarly, the part played by benthic foraminifera in CCZ ecosystems is largely a matter of speculation, although their abundance across different size classes suggests that it is significant. Meiofauna-sized taxa that consume freshly-deposited organic detritus may be important in carbon cycling, particularly at the shallower, more eutrophic eastern end of the CCZ. Megafaunal xenophyophores can provide habitat structure for other organisms, potentially enhancing benthic biodiversity. Foraminifera of all sizes could be among the earliest recolonisers of disturbed or redeposited sediments. Their potential contributions in terms of both ecology and biodiversity make these protists significant members of benthic communities in the CCZ.

Assessment of ecosystem health entails consideration of species interactions within and between size classes to determine their contributions to ecosystem function. Elucidating microbial involvement in these interactions requires tools to distil diverse microbial information down to relevant, manageable elements. We used covariance ratios (proportionality) between pairs of species and patterns of enrichment to identify “core communities” of likely interacting microbial (1 mm) taxa within assemblages hosted by a foundation species, the hydrothermal vent tubeworm Ridgeia piscesae. Compared with samples from co-located hydrothermal fluids, microbial communities within R. piscesae assemblages are hotspots of taxonomic richness and are high in novelty (unclassified OTUs) and in relative abundance of Bacteroidetes. We also observed a robust temperature-driven distinction in assemblage composition above and below ~25 °C that spanned micro to macro size classes. The core high-temperature community included eight macro- and meiofaunal taxa and members of the Bacteroidetes and Epsilonbacteraeota, particularly the genera Carboxylicivirga, Nitratifractor and Arcobacter. The core low-temperature community included more meiofaunal species in addition to Alpha- and Gammaproteobacteria, and Actinobacteria. Inferred associations among high-temperature core community taxa suggest increased reliance on species interactions under more severe hydrothermal conditions. We propose refinement of species diversity to “core communities” as a tool to simplify investigations of relationships between taxonomic and functional diversity across domains and scales by narrowing the taxonomic scope.

Deep-sea trenches are one of the last frontiers for deep-sea exploration and represent a large reservoir of undiscovered biodiversity. This applies in particular to organisms belonging to smaller-size classes, such as meiofauna. Among different meiofauna taxa, kinorhynchs represent a large gap in our knowledge about global marine biodiversity in general, but primarily in extreme deep-sea environments. Out of the more than 300 known mud dragon species, only a single species has ever been described from hadal depths (> 6000 m), i.e., Echinoderes ultraabyssalis from the Kuril-Kamchatka Trench. The results presented in this paper are based on material collected during a research expedition in 2018 investigating the Atacama Trench environment. We provide a first overview and comparison of the diversity and abundance of mud dragons in the Atacama Trench, the adjacent abyssal plain and continental slope off Chile. The study revealed six species of Echinoderes. Of these, Echinoderes mamaqucha sp. nov. is described as a new species and morphological data of three undescribed species are given. Because of the low number of available specimens, we provide only a brief description of these three species and comparison with their morphologically closest congeners, but formal descriptions are not given. Moreover, Echinoderes juliae and Echinoderes pterus were also recovered. Echinoderes juliae was described from the abyssal plain off Oregon and along the continental rise off California, at 2702 to 3679 m depth. Echinoderes pterus is known from the high Arctic, the North Atlantic, and the Mediterranean Sea, and has also been reported to show a wide bathymetric distribution, from 675 to 4403 m. Interestingly, E. mamaqucha sp. nov. dominated at the trench stations and it reached its highest abundance at the deepest station, at 8085 m water depth. The only other single individual that was found in the Atacama Trench was Echinoderes sp.1. The remaining four species were all found at the abyssal and slope stations. The obtained results seem to confirm previous hypotheses about geographic isolation of deep-sea trenches and relatively low connectivity with other habitats, reflected by limited diversity of sediment dwelling fauna, particularly in the deepest parts of trenches.

The meiobenthos of sandy beaches was collected with a 2.54 cm diameter nucleator introduced 5 cm into the sediment. Samples were also taken to microbiological analysis of the wet sand of the beaches during the lowest tide of syzygy, every 15 days for a period of two months. The samples were taken at beaches in the Los Santo region, Los Guayaberos, Bella Vista, El Rincon and La Yeguada. The analysis of the microbiological results indicated that there was growth in Los Guayaberos and Bella Vista of faecal coliforms, while the other two beaches growth is lower or there was no growth. The analysis of the results of the four beaches indicated the following groups associated with polluted areas: Nematodes with 45,2 ind/10 cm², Oligochaets with 6,91 ind/10 cm², Gnathostomulids with 1,97 ind/10 cm², and Foraminiferans with 0,98 ind/10 cm², which represented the 90 % of the meiobenthic fauna. On the other hand, in the uncontaminated zone: Nematodes 12.82 ind / 10 cm², Oligochaetas 4.27 Gnathostomulids 2.63 ind / 10 cm², and no Foraminifera, the highest abundance of these groups is a good indicator of beach pollution.

Data on benthic harpacticoid copepods from the Voronin Trench (central part of the Kara Sea) are reported for the first time. Harpacticoids accounted for 1–25% of total meiofauna, their abundance varied from 6 to 102 ind/10 cm2 and decreased with depth. Totally, 42 nominal species have been found, 15 species are new for the Kara Sea, and at least eight species are new for science. Several species are first records for the Arctic waters (Cylindronannopus bispinosus, Haloschizopera clotensis, H. bathyalis, Metauntemannia pseudomagniceps, Mesocletdemus duosetosus, M. parabodini, Proameira echinipes, Cletodes tuberculatus). Ameiridae, Argestidae, Pseudotachidiidae, Miraciidae and Ectinosomatidae are the most species-rich families. Joint analysis with data on shallow-water stations (Yenisei Gulf, southern Kara Sea) revealed three assemblages occupying different habitats. The assemblage inhabiting shallow silts (20–62 m in depth) was the poorest one, the shallow sands were more species-rich, while the deepest stations (92–698 m) was the richest one. The latter assemblage had the composition of families typical for the deep-sea areas. The known fauna of the Kara Sea includes 82 harpacticoid species, most of which have been also reported from north Atlantic and/or western Arctic waters.

Kinorhyncha is usually one of the more neglected groups in meiofauna ecology. Although their presence is frequently reported in a number of ecological meiofaunal studies, knowledge on their taxonomic composition and distribution at the local and regional scale is very limited. Particularly for the Arctic region, no comprehensive ecological description of kinorhynch communities has yet existed. To address this gap in our knowledge, we compared kinorhynch community structure in different localities: in the region north of Svalbard, in the Barents Sea and four Spitsbergen fjords. Sample locations covered a wide depth gradient from 300 up to 2200 m and different environmental regimes. We analyzed over 4000 individuals among which 18 species belonging to 4 genera and 2 families were identified. The most common species were Echinoderes drogoni and Echinoderes angustus, while the most dominant species was Echinoderes eximus. Patterns of species abundance and shift in their occurrence across the stations were pronounced, with notable distinctions between regions. Three distinct kinorhynch assemblages were observed: ‘fjord assemblage’ dominated by E. eximus and characterized by the highest standing stock and diversity; ‘open water assemblage’ with Echinoderes arlis as dominant species and ‘north of Svalbard assemblage’ characterized by the presence of E. drogoni and Echinoderes peterseni, but at the same time, by the lowest abundance and diversity. We found sediment particle size diversity as the most important explanatory variable. Variation in kinorhynch community structures and diversity was also explained by water depth, but this factor was less important in comparison to sediment characteristics. Surprisingly, food-related variables did not contribute significantly to the model, which could suggest that food partitioning did not influence on promoting diversity. However, it is the first study of arctic kinorhynch ecology and further research is needed to get a more comprehensive understanding of the environmental drivers for turnover in Arctic kinorhynch diversity and distribution.

Meiofaunal abundance, assemblage structure and richness of higher taxa were investigated for the first time in two submarine canyons (Polcevera and Bisagno) of the Ligurian Sea and along the adjacent open slope, in relation with the quantity and quality of sedimentary organic matter and other environmental variables, including grain size. Meiofaunal abundance and richness of higher taxa decreased with increasing water depth (from ca. 200 down to ca. 2000-m depth) in the open slope and Polcevera canyon, whereas the highest values were observed at 500 m depth in the Bisagno canyon. The comparison between canyons and the adjacent open slope, showed the lack of significant differences in meiofaunal abundance, at the same depth except for samples collected at 200 and 2000-m depth. Overall the biodiversity was higher in canyons than in the open slope. Phytopigments, utilised as a proxy of the input of primary organic matter, were up to 3 times higher in canyon than in slope sediments and, along with grain size, explained a large portion of the variability in all meiofaunal variables. Canyon and slope showed a high beta diversity (83%), mostly due to the presence of a high portion of rare taxa in the canyons. Some taxa, such as Cladocera, Cumacea, Gastrotricha, Nemertina were exclusively encountered in canyon sediments, whereas Tardigrada were encountered only in the adjacent slope. Results reported here indicated that, differences in meiofaunal assemblages between canyons and slopes are primarily driven by quantity and quality of the available food resources and by the presence of specific topographic features.

Data on benthic harpacticoid copepods from the Voronin Trench (central part of the Kara Sea) are reported for the first time. Harpacticoids accounted for 1–25% of total meiofauna, their abundance varied from 6 to 102 ind./10 cm2 and decreased with depth. I total, 42 nominal species have been found, 15 species are new for the Kara Sea, and at least 8 species are new for science. Several species have been recorded for Arctic waters for the first time: Cylindronannopus bispinosus, Haloschizopera clotensis, H. bathyalis, Metauntemannia pseudomagniceps, Mesocletdemus duosetosus, M. parabodini, Proameira echinipes, and Cletodes tuberculatus. The most species-rich families are Ameiridae, Argestidae, Pseudotachidiidae, Miraciidae, and Ectinosomatidae. Comparative analysis including the data obtained at shallow-water stations from the Yenisei Gulf (southern Kara Sea) revealed three assemblages occupying different habitats. The assemblage inhabiting shallow-water silts (20–62-m depth) was the poorest in regard to species diversity; shallow-water sands were richer in species number, while the deepest stations (92–698 m) were the richest. The latter assemblage had the composition of families typical for the deep-sea areas. The fauna of the Kara Sea includes by now 82 harpacticoid species, most of which have been also reported from North Atlantic and/or western Arctic waters.

Spatial structure of the macroand meiobenthic communities of the south-eastern Barents Sea (also known as Pechora Sea) was investigated in 2003 during the expedition of the RV «Professor Shtokman». One grid of the stations was used for both benthic size classes. Community dominated by Serripes groenlandicus occupied the most part of the investigated polygon, Astarte borealis dominated the easternmost station. Described communities are in correspondence with historic data. In the meiobenthic communities, nematodes played a leading role, accounting for 86–94% of the total number. Nematode Richtersia inaequalis was dominant on most stations, at the northernmost station the nematodes Cervonema papillatum and Microlaimus affinis dominated. The temperature and the salinity of the near-bottom water layer were homogenous, macroand meiobenthic communities were not influenced by grain size. In contrast to our expectations, communities of the macroand meiobenthos were distributed independently of each other on the mesoscale area (30×11 km).

A new species of stygobiontic interstitial annelid, Diurodrilus kunii sp. nov., is described based on material collected from medium sand sediment (φ = 1.2–1.7) at groundwater level (40–100 cm in depth; 5–15 m inland from splash zone) in the intertidal beach slope on Ishikari Beach, facing the Sea of Japan, Hokkaido, Japan. The new species differs from six known congeners in the arrangement of the anterior-head ventral ciliophores, the degree of development in the primary and secondary toes, and the shape of the spermatozoa. We inferred the phylogenetic position of the new species among other congeners for which 18S rRNA, 28S rRNA, and COI gene sequences were available in public databases. This is the first representative of the genus from the Northwest Pacific.

A new species of the monotypic genus Pseudoameiropsis was found in samples collected from the eastern Mediterranean coast of Turkey. The new species can be separated from P. argentinus by the armature formula in the endopod of the second to fourth swimming legs (0, 1, 021; 0, 1, 121; 0, 1, 121 in P. argentinus, but 1, 1, 221; 1, 1, 221; 1, 1, 221 in the new species), and armature complement in the third exopodal segment of the fourth swimming leg (with eight setae/spines in the new species, but seven elements in P. argentinus). The general shape and armature of the female fifth leg is similar in the two species but some minor differences in their ornamentation were observed. This is also the first record of the genus in the Mediterranean Sea and outside of the South Atlantic Ocean.

A study was performed in 2003 during the cruise of the R/V Professor Shtokman. A single sampling grid and similar approaches to community identification and analysis were used for both size classes of the benthos. A macrobenthic community dominated by Serripes groenlandicus occupied the majority of the study area, whereas Astarte borealis dominated at the easternmost station. Nematodes played a leading role in the meiobenthic communities, where they accounted for 86–94% of the total abundance. The nematode Richtersia inaequalis dominated in almost all areas, while Cervonema papillatum and Microlaimus affinis dominated in the northernmost part of the study area. Temperature, salinity, and grain-size characteristics did not affect the distribution of macro- and meiobenthic communities. The distribution of mosaic elements of macrobenthos and meiobenthos was independent of each other in a mesoscale (30 km long and 11 km wide) study area.

Although soluble hydrocarbons persist for only hours to days in aquatic environments, they potentially pose a high toxicity to aquatic biota. Here we investigate effects of the water-soluble fraction (WSF) of crude oil on estuarine meiofauna, with special focus on nematodes. Copepods and amphipods were the most sensitive taxa, disappearing almost completely within 3 weeks after exposure. In nematodes, we observed mostly sublethal short-term effects of WSF, such as changes in feeding-type composition and age structure. In the longer term (months), total nematode density and species composition were significantly affected, whereas different diversity indices did not exhibit significant responses. Deposit-feeding and predatory nematodes were the most affected feeding types. Nevertheless, sensitivity was species-specific, with sometimes opposing responses between even congeneric species. Our results demonstrate the need to assess WSF effects on communities at the species level and over time periods well exceeding the residence time of the WSF in the environment. Copyright © 2019 Elsevier Ltd. All rights reserved.

Benthic organisms are considered among the best bioindicators being closely associated to sediments in which many pollutants are stored. In this study, macrophytes and meiofauna have been investigated in a transitional area (Venice lagoon, Italy) characterized by numerous anthropogenic pressures. Macrophyte Quality Index and meiofaunal richness were used to assess Ecological Quality (EcoQ) status in line with Water Framework and Marine Strategy Framework Directives. Comparing the EcoQ classes, the results appeared consistent in 24 sites, whereas, in the remaining 5 ones, the values significantly diverged. These results could be related i) to the presence of the seagrass Cymodocea nodosa that could affect meiofaunal taxa with the production of tannins; ii) to the different time response of these communities to human impacts. This synergistic investigation has allowed an accurate description of the spatial and temporal changes of meiofauna through data on abiotic and biotic parameters characterizing the ecosystem trophic level.

Community and abundance patterns of meiofauna and Harpacticoida in the Kuril-Kamchatka Trench, that trench’s slope and adjacent abyssal plain which is located in the North-Western Pacific were investigated in relation to environmental variables. Overall, Nematoda was the dominant taxon of the meiofauna community (93%), followed by Copepoda (3%). Nineteen harpacticoid families and 1 subfamily were found, whereby the family Ameiridae was most abundant in the study area. Within eight selected (sub)families (Argestidae, Aegisthidae, Ancorabolidae, Canthocamptidae, Cletodidae, Cylindropsyllinae, Parameiropsidae, Zosimeidae) 27 genera were found, with Zosime and Mesocletodes being most abundant. Dispersion effects characterized the meiofauna community abundances, while the Harpacticoida communities in the hadal and abyssal were distinct. The main contributor to the dissimilarities observed were Nematoda, Ameiridae, Zosime and Mesocletodes. Food availability, sediment composition and water depth are environmental drivers structuring the investigated communities in the abyssal and hadal. For the trench slope, no correlations with the investigated environmental variables were found. Very likely variables other than the investigated ones act as environmental drivers for the trench slope (e.g. topography). Furthermore, a tendency of meiofauna to increase in total abundances was detected with increasing depth in the deeper stations starting at 6000 m. In contrast, total Harpacticoida abundances decrease with depth. Considering the abundance of Harpacticoida families and genera individually, the abundance of some taxa decreased in the trench slope but increased in the trench floor (Zosimeidae, Miraciidae, Argestidae, Parameiropsis, Zosime). Diversity indices based on Harpacticoida genus and family level were not distinguishable with the exception of equitability (J) at the genus level (abyssal vs hadal; trench slope vs hadal).

The effects of compacted algal mats growing attached to sediments on the abundance and community structure of intertidal sediment meiofauna and harpacticoid copepod assemblages were evaluated on a tropical estuarine mudflat. Differences in fauna based on the presence of algae (within vs. outside the algal patches) and the physiological stages of the algae (live vs. decomposing algal patches) were compared. In general, lower densities occurred within algal patches for most meiofaunal groups, except for harpacticoids, which showed an increase in number in the live algal patches (LAP). Non-metric MDS analysis clearly distinguished both meiofauna community and harpacticoid assemblage in relation to the presence of algae and the physiological stage. Organic matter, carbohydrates, proteins and photosynthetic pigments were higher within algal patches and highly correlated with meiofauna variables. One species of harpacticoid ( Cletocamptus sp.1) dominated the LAP samples and thus reduced species richness and diversity of harpacticoids in these samples. The species Robertsonia mourei occurred exclusively in decomposing algal patches (DAP) and probably is an opportunistic species within the DAP samples. Strong differences regarding live and decomposing algae samples highlighted the importance of physiological stage in understanding meiofaunal responses to algal mats.

Seagrass meadows ecosystem engineering effects are correlated to their density (which is in turn linked to seasonal cycles) and often cannot be perceived below a given threshold level of engineer density. The density and biomass of seagrass meadows ( Z. marina ) together with associated macrophytes undergo substantial seasonal changes, with clear declines in winter. The present study aims to test whether the seasonal changes in the density of recovering seagrass meadows affect the benthic food webs of the southern Baltic Sea (Puck Bay). It includes meiofauna , macrofauna and fish of vegetated and unvegetated habitats in summer and winter seasons. Two levels of organization have been tested – species-specific diet preferences using stable isotopes ( δ13C, δ15 N) in Bayesian mixing models (MixSIAR) and the community-scale food web characteristics by means of isotopic niches (SIBER). Between-habitat differences were observed for grazers, as a greater food source diversity in species from vegetated habitats was noted in both seasons. Larger between-habitat differences in winter were documented for suspension/detritus feeders. The community-wide approach showed that the differences between the habitats were greater in winter than in summer (as indicated by the lower overlap of the respective isotope niches). Overall, the presence of seagrass meadows increased ecological stability (in terms of the range of food sources utilized by consumers) in the faunal assemblage , while invertebrates from unvegetated areas shifted their diet to cope with winter conditions. Therefore, as a more complex system, not sensitive to seasonal changes, Z. marina meadows create a stable habitat with high resilience potential.

Ostracoda, minute aquatic crustaceans with calcitic shells, are highly versatile proxies in geoarchaeological contexts. Their species-specific ecological preferences and ranges allow the reconstruction of palaeoenvironments and anthropogenic impacts in detail. Environmentally driven morphological variability and shell chemistry signatures as stable isotope and trace element values can provide additional palaeoenvironmental information. Ostracods can be used for provenance analyses and stratigraphical investigations as well. Their small size and high abundance in most water bodies makes them ideal for studying sediment cores and smaller samples from trenches or outcrops, especially in coastal areas where they show a high diversity and abundance compared to other groups of meiofauna. In archaeological contexts, fossil ostracods may provide information about climate, sea level and hydrography, high energy events like storms or tsunamis, ocean currents, land use, pollution, water constructions, stratigraphy, trade connections or the origin of sediment material. We give an overview on the state of ostracod-based research in geoarchaeology today and present some European case studies to illustrate concepts and methods of such field of study.