Metazoan Meiofauna Research Articles

Meiofauna in the southeastern Bering Sea: community composition and structuring environmental factors

The Bering Sea is the second largest marginal sea in the North Pacific and is one of the areas with highest biological productivity in high-latitude waters. The continental shelf of the Bering Sea hosts large populations of marine mammals and fishery resources. However, the smaller organisms in benthic ecosystems, including meiofauna, have been largely overlooked in this area, despite their potential importance in ecosystem functioning and the resultant biogeochemical cycles. This study analyzed spatial differences in the total abundance and community structure of the metazoan meiofauna at five stations around the Bering Canyon, located at the southeastern margin of the Bering Sea. Their association with environmental factors in sediments was also studied. The results confirmed that the investigated stations had meiofaunal standing stocks that were comparable to those of other Arctic seas. Among the investigated sediment biological and geochemical parameters (total organic carbon, median grain size, prokaryotic cell numbers, etc.), multivariate analyses showed that the C/N of organic matter in sediments was the main factor associated with meiofaunal community structure.

Impact of local iron enrichment on the small benthic biota in the deep Arctic Ocean

This study assesses the impact of local iron enrichment on the small benthic biota (bacteria, meiofauna) at the deep seafloor. To evaluate the hypothesis that abundance, distribution, and diversity of the small benthic biota varies in relation to a local input of structural steel at the seabed, we analyzed sediment samples and the associated infauna along a short transect (~1.5 m in length) with increasing distance to an iron source, i.e., corroding steel weights (30 cm in length and width, and 6 cm in height) of a free-falling observational platform (bottom-lander), lying on the seafloor for approximately seven years. Bacterial and meiofaunal densities and biomasses in iron-enriched sediments were significantly lower than those in unaffected sediments. Moreover, bacterial and nematode community structure between iron-enriched sediments and unaffected sediments differed strongly; taxonomic richness as well as diversity was lowest closest to the iron source. The presence of iron fostered the establishment of specialized iron oxidizers and other chemolithoautotrophic bacterial members, which were rare or absent in the unaffected sediments, within which opportunistic heterotrophs predominated. Nematodes comprised >90% of the total metazoan meiofauna and were therefore studied in more detail. A total of 26 genera from 16 families occurred in iron-enriched sediments (three genera were found exclusively in these sediments), while 65 genera from 27 families occurred in the unaffected sediments (39 genera and 12 families were found exclusively in these sediments). Nematode genera number (S), estimated genera richness (EG(51)) and heterogeneity (H’(log2)) were significantly lower in iron-enriched sediments than in unaffected sediments. Our results confirm that the local enrichment of deep-sea sediments by metallic and corroding structures (e.g., by ship hulls, containers, scientific equipment) strongly affects the diversity of the small benthic biota at short distances from these sources.

Hydrothermal vent chimney-base sediments as unique habitat for meiobenthos and nanobenthos: Observations on millimeter-scale distributions

Hydrothermal vents are critical to marine geochemical cycling and ecosystem functioning. Although hydrothermal vent-associated megafauna and chemoautotrophic prokaryotes have received extensive dedicated study, smaller hydrothermal vent-associated eukaryotes such as meiofauna and nanobiota have received much less attention. These communities comprise critical links in trophic flow and carbon cycling of other marine habitats, so study of their occurrence and role in hydrothermal vent ecosystems is warranted. Further, an understudied vent habitat is the thin sediment cover at the base of hydrothermal vent chimneys. An initial study revealed that sediments at the base of vent chimneys of the Izu-Ogawasara Arc system (western North Pacific) support metazoan meiofauna, but very little is known about the taxonomic composition and abundance of the meiobenthic protists and nanobiota, or their millimeter-scale distributions. Using the Fluorescently Labeled Embedded Coring method (FLEC), we describe results on meiofaunal and nanobiota higher-level identifications, life positions and relative abundances within sediments from three habitats (base of vent chimneys, inside caldera but away from chimneys, and outside caldera) of the Myojin-Knoll caldera and vicinity. Results suggest that the chimney-base community is unique and more abundant compared to non-chimney associated eukaryotic communities. Supporting evidence (molecular phylogeny, scanning and transmission electron microscopy imaging) documents first known hydrothermal-vent-associated occurrences for two protist taxa. Collectively, results provide valuable insights into a cryptic component of the hydrothermal vent ecosystem.

A comparison of intertidal metazoan biodiversity among different salinity zones of Louisiana coastal marshes

Tidal marshes are among the most valuable, productive, and vulnerable ecosystems with high biodiversity. Louisiana’s saltmarshes are endangered by natural and man-made stressors, including oil pollution, saltwater intrusion, and land loss due to sea level rise and erosion. Freshwater diversions have been planned to restore sediment input from the Mississippi River to rebuild marsh habitats in South Louisiana. These proposed diversions will undoubtedly change salinity levels, which is a major controlling factor in the distribution of marsh organisms, including those in soil; however, detailed pre-event inventories are lacking. This study describes the diversity of metazoan meiofauna (organisms between 45 and 500 μm) and environmental DNA in marsh soil collected in 2018 from Barataria and Caillou Bay, Louisiana, across three salinity zones and four distances from the marsh edge. Diversity analyses using 18S rRNA gene metabarcodes identified salinity as a factor impacting soil metazoan composition. Nematoda and Mollusca were equally distributed across salinity zones. Gastrotricha, Bryozoa, Rotifera, and Platyhelminthes were more prevalent in low salinity while Kinorhyncha were not detected in low salinity. Annelida and insects were equally common in low and high salinity but less in mid salinity. Five nematodes (Eumonhystera filiformis, two Prismatolaimus spp., Anoplostoma sp., and Prodorylaimus sp.), two annelids (Marionina southerni and Dendronereis aestuarina), two platyhelminthes (Rhynchoscolex simplex and Olisthanella truncula), the gastrotrich Chaetonotus novenarius and four collembola and ostracods appear to be low salinity bioindicators and are expected to expand range with freshwater diversions. No frequently detected organisms were unique to mid or high salinity zones, but four Nematoda (Meleidogyne spartinae, Prochaetosoma sp., Halalaimus sp., and Dichromadora sp.), two Annelida (Alitta succinea and Namalycastis jaya), two Platyhelminthes (Macrostomum kepneri and Mesorhynchus terminostylis), and one Kinorhyncha (Echinoderes sp.) were never detected in low salinity zones. None of the frequently detected taxa were unique for a particular distance from the marsh edge or bay. This dataset will be useful as baseline for assessing how soil communities will change in response to salinity changes caused by freshwater diversions and saltwater intrusion as well as measuring the environmental impact of pollution and other stressors.

Community structure of deep-sea benthic metazoan meiofauna in the polymetallic nodule fields in the eastern Clarion-Clipperton Fracture Zone, Pacific Ocean

The abyssal sea floor of the Clarion-Clipperton Fracture Zone (CCFZ) in the Pacific Ocean is expected to become a commercially important nodule mining area in the near future. Hence, it is crucial to understand the community structure of biological communities there, so that nodule harvesting activities can be designed to minimize deleterious impacts on marine life. Meiofauna is an important component of the abyssal infaunal community but relatively little is known on their biodiversity, abundance, and community structure in the CCFZ. We provide here the first quantitative observations of metazoan benthic animals ≥40 μm in a 30 × 30 km area survey stratum in the Ocean Mineral Singapore contract area at the eastern end of the CCFZ. A total of 88 867 individuals, identified to 23 animal groups, were collected from 12 randomly sampled stations using a multiple corer. Even in our small surveyed area, the meiofaunal community structure appeared different at our stations, confirming that the CCFZ deep sea floor is very diverse. From the top 0–5 cm sediment layer, unsurprisingly, the three most abundant animal groups were the Nematoda (87.9 ± 2.9%), the Nauplii (5.0 ± 1.3%) and the Copepoda (4.3 ± 1.1%). The majority of the meiobenthos (76.6%) were in the top 0–2 cm sediment layer. Our results suggested that substratum shear strength was negatively and significantly correlated to meiofaunal abundances among the 12 stations. Nodule cover and nodule volume did not appear to affect the meiofaunal community structure at the major taxon level. The mean meiofaunal abundance (235.7 ± 26.4 ind./10 cm2) was relatively high at our site in comparison with previous studies elsewhere in the CCFZ, further confirming the westward decrease in meiofaunal abundance across the CCFZ.

A threefold perspective on the role of a pockmark in benthic faunal communities and biodiversity patterns

Pockmarks are circular-shaped depressions that increase seabed heterogeneity and are characterized by discontinuous fluid emissions. To understand how environmental conditions of pockmarks affect the structure of macro- and meiofauna, we investigated two sites in a pockmark field in the northwestern Madagascar margin. In a comparative approach, we explored the community structure of the dominant taxa (Polychaeta, Nematoda and hyaline foraminifera) in each component (macro-, metazoan meiofauna and foraminifera, respectively). The investigated active pockmark showed approximately two times higher meiofauna abundance compared to in a site away from another pockmark field, but macrofauna showed the opposite trend, with almost half density at the pockmark site. However, at both sites, macro- and meiofauna showed higher richness and abundance values in the top well-oxygenated layers of the sediment than in the underlaying ones. Polychaeta and Nematoda showed lower richness in the pockmark, opposed to hyaline foraminiferans, but lower evenness in the pockmark was found for the three groups. The detection of gas flares in the water column attests of the recent activity within the pockmark. High amount of sulfur-bearing minerals (mainly pyrite) evidences a production of dissolved free sulfides (not detected at the time of sampling) by sulfate reduction process driven by organic matter degradation and anaerobic oxidation of methane. Furthermore, recent increase in sedimentation rates in the past 70 years and organic matter inputs could have led to higher organic matter degradation rates resulting in reduced conditions and a high oxygen consumption. All this together seem to act as key factors in the determination of variation in richness, abundance and community composition of macrofauna and meiofauna. Additionally, some taxa seem to be more tolerant to these extreme conditions, such as species belonging to the Nematoda genus Desmodora and the phylum Kinorhyncha, which are highly abundant in the pockmark, and hence, may be considered as potential bioindicators of pockmark activity in this area. Further studies are required for a better assessment.

Spatial and Temporal Variation in Deep-Sea Meiofauna at the LTER Observatory HAUSGARTEN in the Fram Strait (Arctic Ocean)

Time-series studies at the LTER (Long-Term Ecological Research) observatory HAUSGARTEN have yielded the world’s longest time-series on deep-sea meiofauna and thus provide a decent basis to investigate the variability in deep-sea meiobenthic communities at different spatial and temporal scales. The main objective of the present study was to investigate whether the sediment-dwelling meiofauna (size range: 32–1000 µm) is controlled by small-scale local environmental conditions, rather than large-scale differences between water depths. Univariate and multivariate statistical analyses, including distance-based linear models (DistLM) and redundancy analysis (dbRDA), revealed that due to their small size, meiofauna tend to mainly respond to micro-scale (centimeter) variations in environmental conditions in surface and subsurface sediment layers. Inter-annual temporal patterns among metazoan meiofauna at higher taxon levels revealed only a weak effect of time, and merely on the rare meiofauna taxa (<2% of the total meiofauna community) at HAUSGARTEN.

Meiofauna Community in Soft Sediments at TAG and Snake Pit Hydrothermal Vent Fields

The risk assessment of Seafloor Massive Sulfides (SMS) mining on meiobenthic organisms, specifically on soft-sediment meiofauna, is impeded by a lack of knowledge on the biology and ecology of these communities. In this study we investigated sediment samples taken in proximity of active vents at Trans-Atlantic Geotraverse (TAG) and Snake Pit, two hydrothermal vent fields of the Mid-Atlantic Ridge, in order to explore metazoan meiofauna, particularly nematode community, and its relation to organic carbon, total nitrogen, total sulfur and dissolved oxygen. Organic carbon and nitrogen contents were low at both sites. High concentrations of total sulfur and low oxygen penetration were found at Snake Pit compared to TAG. Snake Pit showed about four times higher meiofauna and nematode density compared to TAG, as well as a dissimilar nematode community composition. We hypothesize that high sulfur concentrations at Snake Pit may support high microbial growth, which represents one of the main food source for nematodes. Moreover, TAG nematode community mostly consisted of persisters (K-strategists), while Snake Pit one was composed by both persisters (Desmoscolecidae family) and colonizers (r-strategists Metalinhomoeus and Halomonhystera), whose presence can be facilitated by the bioturbation effect of polychaetes observed on the sediment surface. Therefore, food availability, geochemical settings and biotic interactions seem to drive the local meiofauna and nematode community. Our study also draws attention to the opportunity of including meiofauna and specifically nematodes in impact studies conducted in this area in order to assess and monitor the impact of SMS mining.

Small-scale distribution of metazoan meiofauna and sedimentary organic matter in subtidal sandy sediments (Mediterranean Sea)

While variations in sedimentary organic matter (OM) quantity, biochemical composition and nutritional quality as well as in meiofaunal abundance and assemblage composition at the macro- and mesoscale are relatively well known, information about variations at the microscale is much scarcer. To shed some light on this issue, we tested the null hypothesis by which abundance and composition of the meiofaunal assemblages, and the quantity, biochemical composition and nutritional quality of sedimentary organic matter in coastal shallow environments do not vary within a frame of 1 m2. No significant variation within the frame emerged for OM quantity, nutritional quality, biochemical composition and the abundance of meiofaunal assemblages. On the other hand, the composition of meiofaunal assemblages varied significantly within the frame and exhibited a clear segregation of assemblages farther to the shore, as a likely result of local micro-hydrodynamic conditions. Spatial autocorrelation analysis revealed that lipid and protein sedimentary contents had a random distribution, whereas carbohydrate and biopolymeric C contents and meiofaunal total abundance were characterized by a patchy distribution, with discrete peaks within the sub-frame squares (ca. 0.1 m2). Phytopigments showed a spatial positive autocorrelation distribution, following the micro-hydrodynamic pattern, with patches larger than the sub-frame square, but smaller than the entire one (1 m2). Overall, our results suggest that, within 1 m2 of subtidal sandy sediments, three replicates could be sufficient to assess correctly OM attributes and the abundance of meiofauna, but could be possibly inadequate for assessing meiofaunal assemblages’ composition at a finer scale (<1 m2).

Distribution of Meiofauna in Bathyal Sediments Influenced by the Oxygen Minimum Zone Off Costa Rica

Ocean deoxygenation has become a topic of increasing concern because of its potential impacts on marine ecosystems, including oxygen minimum zone (OMZ) expansion and subsequent benthic effects. We investigated the influence of oxygen concentration and organic matter (OM) availability on metazoan meiofauna within and below an OMZ in bathyal sediments off Costa Rica, testing the hypothesis that oxygen and OM levels are reflected in meiofaunal community structures and distribution. Mean total densities in our sampling cores (400-1800 m water depth) were highest with 3688 ind. 10 cm-2 at the OMZ core at 400 m water depth, decreasing rapidly downslope. Nematodes were overall dominant, with a maximum of 99.9% in the OMZ core, followed by copepods (13%), nauplii (4.8%), and polychaetes (3%). Relative copepod and nauplii abundance increased consistently with depth and increasing bottom-water O2. Meiofaunal composition was significantly different among sites, with lower taxonomic diversity at OMZ sites relative to deeper, oxygenated sites. Vertical distribution patterns within sediments showed that in strongly oxygen-depleted sites less meiofauna was concentrated in the surface sediment than at deeper slope sites. Highest meiofaunal abundance and lowest diversity occurred under lowest oxygen and highest pigment levels, whereas highest diversity occurred under highest oxygen-concentrations and low CPE, as well as high quality of sedimentary pigment (chl a/phaeo) and organic carbon (C/N). The lower meiofaunal diversity, and hence lower structural and trophic complexity, at oxygen-depleted sites raises concerns about changes in the structure and function of benthic marine ecosystems in the face of OMZ expansions.

Seasonal dynamics of meiofauna from the oligotrophic continental shelf of Crete (Aegean Sea, eastern Mediterranean)

The response of metazoan meiofauna and nematode communities to the sedimentation of a spring phytoplankton bloom was investigated at four stations of the continental shelf of Crete (south Aegean Sea, eastern Mediterranean). The four stations were located on a transect with depths of 20, 70, 130 and 190m, and samples were taken monthly from May 1989 to May 1990. After the onset of the spring bloom, a marked increase in sedimentary chlorophyll α values was observed (on average 1.6μg/g). These values remained stable throughout the spring and summer period while during autumn and winter they dropped to very low levels (0.2μg/g). Nematodes dominated in the meiofauna, ranging from 78% in March to 95% in August and January. Harpacticoid copepods were the second most abundant group, ranging from 2% in August to 18% in April. Total meiofauna biomass was lowest in January (0.03mg/10cm2) and highest during spring and summer after the spring bloom (1.07mg/10cm2). Most meiofaunal taxa displayed significant seasonal changes at the shallower stations (20, 70 and 130m), with abundances rising during spring and autumn following the productivity of the water column. Conversely, no seasonal variability was evident in terms of abundance or biomass at the deeper station (190m). Nematode epistrate feeders and selective deposit feeders were more abundant at the two shallower stations, increasing their numbers after the spring bloom. Among the most dominant species, some represented as much as 18% of the total nematode abundance. The nematode community structure displayed a gradual transition, with increasing depth being mostly influenced by the sedimentary characteristics of the environment as well as the overall productivity of the system. The nematode species diversity was found to be significantly lower at the intermediate station (70m), where physical and biological disturbance were highest.

Deep-sea metazoan Meiofauna from a Polymetallic nodule area in the Central Indian Ocean Basin

The metazoan meiofauna in the Central Indian Ocean Basin were collected at five deep sea stations (depths ranging 4738 to 5418 m) during the China Ocean Mineral Resources Research and Development Association (COMRA) 22nd Expedition Cruise in December, 2011. The sampling stations were in and around a potentially commercial important polymetallic nodule area. All together five meiofauna taxa were detected, including Nematoda, Harpacticoida copepoda, Polychaeta, Halacaroidea and Ostracoda. Average meiofaunal abundance (9.59 ± 5.44 ind./10cm2) was generally lower than the other meiofaunal abundance reported in the Central Indian Ocean and much lower than those reported from other deep-sea regions. The abundance pattern of vertical distribution corresponded well with those from other deep-sea regions. Biomass calculation with coefficients considering detailed size classes was done. Average total meiofaunal biomass was estimated as 4.64 ± 1.81 μg/10 cm2 (dry weight). The composition of meiofaunal assemblages from different stations differed substantially. Stations in the center of the polymetallic nodule area had similar meiofaunal abundance, biomass, as well as relatively high similarity. The present study could offer a baseline of the meiofauna and enrich the meiofauna data in the area, and could be helpful for future disturbance studies.

Short-term CO2 exposure and temperature rise effects on metazoan meiofauna and free-living nematodes in sandy and muddy sediments: Results from a flume experiment

Global concern over increasing CO2 emissions, and the resultant CO2 driven temperature rises and changes in seawater chemistry, necessitates the advancement of understanding into how these changes will affect marine life now and in the future. Here we report on an experimental investigation into the effects of increased CO2 concentration and elevated temperature on sedimentary meiofaunal communities. Cohesive (muddy) and non-cohesive (sandy) sediments were collected from the Eden Estuary in St. Andrews, Scotland, UK, placed within a flume setup and exposed to 2 levels of CO2 concentration (380 and 750ppmv, current at the time of the experiment, and predicted CO2 concentration by 2100, respectively) and 2 temperature levels (12°C and 16°C, current in-situ and predicted temperature by 2100, respectively). We investigated the metazoan meiofauna and nematode communities before and after 28days of exposure under these experimental conditions. The most determinative factor for abundance, diversity and community structure of meiofauna and nematodes was sediment type: on all levels, communities were significantly different between sand and mud sediments which agrees with what is generally known about the influence of sediment structure on meiofaunal organisms. Few CO2 and temperature effects were observed, suggesting that meiofauna and nematodes are generally much less responsive than, for instance, microbial communities and macrofauna to these environmental changes in estuarine environments, where organisms are naturally exposed to a fluctuating environment. This was corroborated by the observed effects related to the different seasons in which the samples were taken from the field to run the experiment. After 28days, meiofauna and nematode communities in muddy sediments showed a greater response to increased CO2 concentration and temperature rise than in sandy sediments. However, further study is needed to investigate the underlying mechanisms and meiofauna species-specific resilience and responses to ocean acidification and warming, and their interactions with other biota, to understand what such changes may mean for meiofauna communities and the ecosystem processes and functions they contribute to.

Local effects of large food-falls on nematode diversity at an arctic deep-sea site: Results from an in situ experiment at the deep-sea observatory HAUSGARTEN

To study the response of the smaller benthic biota to larger food-falls and their possible effects on the biodiversity at the deep seafloor, we deployed the halves of a sagittally bisected porpoise (1.3m in length; each half approximately 18kg) at 2500m and 5400m water depth at the LTER (Long-Term Ecological Research) observatory HAUSGARTEN in the eastern Fram Strait. Five weeks after the porpoise deployment, sediments beneath the carcasses and at different distances (0, 20, 40cm) from these artificial food-falls were sampled with push-corers handled by a Remotely Operated Vehicle. The samples provided empirical evidence for a quick response by sediment-inhabiting bacteria and metazoan meiofauna to the carcasses at both water depths. Compared to control sediments, the substantial pulse of organic matter also led to generally increased meiofauna/nematode densities around the artificial food-falls. The comparison of nematode communities in sediments affected by the carcasses with those in control sediments exhibited shifts in the structural composition and the associated trophic and functional diversity of the nematodes. Our results confirmed that the impact of large food-falls on the deep benthic community largely depend on environmental factors (water depth, alternative food sources) as well as the background species composition, i.e., the structure of the prevailing meiofauna/nematode assemblages and the composition of the necrophagous community present in the wider area.

Composition and vertical distribution of metazoan meiofauna assemblages on the continental shelf off central Chile

A quantitative study of metazoan meiofauna was carried out in Valparaiso Bay (33°S 71°W) which is affected by seasonal hypoxia in central Chile. The contents of bottom water, dissolved oxygen (BWDO), organic carbon, chloroplast pigments and composition of stable carbon isotope (d13C) in the sediment were used as a measure of the contribution of primary production in the water column, which accumulates in the sediment. Meiofauna abundances in the three sampling stations (80-140 m depth) ranged from 2.218 ± 643 to 1.592 ± 148 ind 10 cm-2. Nine upper metazoan meiofauna groups were recorded, with nematodes as the dominant group, contributing with more than 95% of total abundances. The abundance vertical distribution was concentrated in the first layers of sediment in most groups except Acari and nauplii larvae. Canonical correspondence analysis revealed significant correlations (P < 0.05) between the meiofauna abundance and organic content, depth and redox potential from sediments. These results represent a first approach to understanding the ecology of meiofaunal assemblages in the Valparaiso Bay and may be useful as a baseline for future comparisons and descriptions of the ENSO (El Niño Southern Oscillation) and seasonal variations of these unknown benthic communities.

Bathymetric patterns in standing stock and diversity of deep-sea nematodes at the long-term ecological research observatory HAUSGARTEN (Fram Strait)

Abstract Bathymetric patterns in standing stocks and diversity are a major topic of investigation in deep-sea biology. From the literature, responses of metazoan meiofauna and nematodes to bathymetric gradients are well studied, with a general decrease in biomass and abundance with increasing water depth, while bathymetric diversity gradients often, although it is not a rule, show a unimodal pattern. Spatial distribution patterns of nematode communities along bathymetric gradients are coupled with surface-water processes and interacting physical and biological factors within the benthic system. We studied the nematode communities at the Long-Term Ecological Research (LTER) observatory HAUSGARTEN, located in the Fram Strait at the Marginal Ice Zone, with respect to their standing stocks as well as structural and functional diversity. We evaluated whether nematode density, biomass and diversity indices, such as H 0 , H inf , EG (50) , Θ − 1 , are linked with environmental conditions along a bathymetric transect spanning from 1200 m to 5500 m water depth. Nematode abundance, biomass and diversity, as well as food availability from phytodetritus sedimentation (indicated by chloroplastic pigments in the sediments), were higher at the stations located at upper bathyal depths (1200–2000 m) and tended to decrease with increasing water depth. A faunal shift was found below 3500 m water depth, where genus composition and trophic structure changed significantly and structural diversity indices markedly decreased. A strong dominance of very few genera and its high turnover particularly at the abyssal stations (4000–5500 m) suggests that environmental conditions were rather unfavorable for most genera. Despite the high concentrations of sediment-bound chloroplastic pigments and elevated standing stocks found at the deepest station (5500 m), nematode genus diversity remained the lowest compared to all other stations. This study provides a further insight into the knowledge of deep-sea nematodes, their diversity patterns and a deeper understanding of the environmental factors shaping nematodes communities at bathyal and abyssal depths.

Extraction of metazoan meiofauna from muddy deep-sea samples: Operator and taxon effects on efficiency

Deep-sea metazoan meiofaunal specimens are usually extracted from muddy samples by centrifugation in a fluid in which meiofauna tend to float and sediment particles tend to sink. Although the procedure is in common use, its efficiency has seldom been examined. The study reported here showed that well-trained operators extracted metazoan meiofauna with efficiencies that were different enough to be a concern in quantitative studies. Therefore, samples should be assigned to operators in a stratified-random manner. In the course of these studies, both operators also extracted individuals of the common nematode family Desmoscolecidae significantly less efficiently than other nematode families, a bias that could interfere with studies that compared relative abundances of nematode families.

Meiofaunal Distribution across the Oxygen Minimum Zone of Continental Margin, North East Arabian Sea

A quantitative study of metazoan meiofauna across the oxygen minimum zone (OMZ) of continental margin in the N-E Arabian Sea in the depth range 500-1965 m was carried out in September-November 2008. Bottom water oxygen and sediment organic carbon showed large variation between stations. The bottom water temperature and salinity was very similar in the area. The fauna was dominated by nematoda followed by harpacticoid copepoda and polychaeta. Maximum meiofaunal density of 164/10 cm 2 was recorded at St. 1 (500 m) and the lowest density of 25/10 cm² was observed at St. 2 (650 m) which coincided with lowest oxygen concentration. Total abundance of meiofauna was significantly lower than those reported from other areas. The average density was high (65/10 cm 2 ) in OMZ than in non OMZ (52/10 cm 2 ) area. Nematodes were the dominant taxon at every station. The dominance was particularly significant at those stations having very low oxygen. The meiofaunal density was positively correlated with sediment organic carbon while oxygen exhibited a negative correlation. Epibenthic Crustacean groups were more in areas of non OMZ having high oxygen. Vertical distribution revealed consistent reduction in total density and major taxa with increasing depth in sediment. Maximum density was recorded in top 0-2 cm layer. Among environmental parameters the availability of food in the form of sediment carbon appeared to be key factor in controlling meiofauna in study areas.

Community response of deep-sea soft-sediment metazoan meiofauna to the Deepwater Horizon blowout and oil spill

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 528:127-140 (2015) - DOI: https://doi.org/10.3354/meps11290 Community response of deep-sea soft-sediment metazoan meiofauna to the Deepwater Horizon blowout and oil spill Jeffrey G. Baguley1,*, Paul A. Montagna2, Cynthia Cooksey3, Jeffrey L. Hyland3, Hyun Woo Bang1, Colin Morrison1, Anthony Kamikawa1, Paul Bennetts1, Gregory Saiyo1, Erin Parsons1, Meredyth Herdener1,2, Morgan Ricci1 1The University of Nevada-Reno, Reno, Nevada, USA 2Texas A&M University-Corpus Christi, Corpus Christi, Texas, USA 3National Oceanic and Atmospheric Administration, National Centers for Coastal Ocean Science, Charleston, South Carolina, USA *Corresponding author: baguley@unr.edu ABSTRACT: The Deepwater Horizon (DWH) blowout and oil spill of 2010 released an estimated 4.9 million barrels of oil into the Gulf of Mexico. Spill-related contaminants that sank to the seafloor pose risks to benthic fauna living within bottom substrates that are unable to avoid exposure due to their relatively sedentary existence. Metazoan meiofauna are abundant and diverse members of deep-sea soft-sediment communities and play important roles in ecosystem function. We investigated the deep-sea metazoan meiofauna community response to the DWH blowout and oil spill at 66 stations ranging from <1 km to nearly 200 km from the Mississippi Canyon Block 252 wellhead. Metazoan meiofauna abundance, diversity, and the nematode to copepod ratio (N:C) varied significantly across impact zones. Nematode dominance increased significantly with increasing impacts, and N:C spiked near the wellhead. Conversely, major taxonomic diversity and evenness decreased in zones of greater impacts that were in closer proximity to the DWH wellhead. Copepod abundance and the abundance of minor meiofauna taxa decreased where impacts were most severe, and at these severely impacted stations the abundance of ostracods and kinorhynchs was negligible. Increasing abundance and dominance by nematodes with increasing impacts likely represent a balance between organic enrichment and toxicity. Spatial analysis of meiofauna diversity and N:C at 66 stations increased our spatial understanding of the DWH benthic footprint and suggests expanded spatial impacts in areas previously identified as uncertain. KEY WORDS: Meiobenthos · Nematoda · Harpacticoida · N:C · Macondo Well · MC252 Full text in pdf format PreviousNextCite this article as: Baguley JG, Montagna PA, Cooksey C, Hyland JL and others (2015) Community response of deep-sea soft-sediment metazoan meiofauna to the Deepwater Horizon blowout and oil spill. Mar Ecol Prog Ser 528:127-140. https://doi.org/10.3354/meps11290 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 528. Online publication date: May 28, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Effects of mass sedimentation events after the 2011 off the Pacific coast of Tohoku Earthquake on benthic prokaryotes and meiofauna inhabiting the upper bathyal sediments

We examined the effects of mass sedimentation events caused by the 2011 off the Pacific coast of Tohoku Earthquake on abundances and vertical distributions of prokaryotes and metazoan meiofauna in sediments, using sediment cores collected from eight bathyal stations off Tohoku 1 year after the M9.0 earthquake. Event deposits 1–7 cm thick were observed at the topmost part of the sediment cores at all sampling stations. At some stations, prokaryotic cell abundances were lower in the surface event-deposit layers compared to those in deeper sediments. These variations were explained by environmental parameters such as a dimensionless sorting factor and mean grain size, suggesting that turbidite sedimentation affected prokaryotic cell abundances. Nematodes had anomalously higher subsurface abundances at the stations where subsurface peak prokaryotic cell numbers were observed, whereas copepods always showed peak densities in the sediment surface layer. Although there are no available data for prokaryotic cell abundances and meiofaunal densities before the earthquake from the same sites, it is likely that the subsurface peaks in prokaryotic cell numbers and nematode densities resulted from the sedimentation events. The effects of sedimentation events on the organisms were observed 1 year after the earthquake, indicating that episodic sedimentation events on scales of several centimeters have a large effect on small organisms inhabiting sediments.