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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. more...

Stygiopontius senokuchiae is a hydrothermal-vent-specific copepod species (Dirivultidae, Siphonostomatoida) and abundantly distributes near vent orifices. This species is thought to have an early juvenile planktic stage, and previous studies using bulk tissue stable-isotope and radioisotope data suggest that adults ingest chemoautotrophic microbes growing on vent chimneys. However, ontogenetic changes in their diets have not been investigated. We analysed gut contents of copepodite I to adult stages of S. senokuchiae collected from a hydrothermal-vent chimney at the Izu-Ogasawara Arc to check for the presence of bacterial cells in oral tubes and guts. We compared these results with an unidentified co-occurring calanoid and a species of Ectinosoma (Harpacticoida) and to other Siphonostomatoid copepods, namely Hatschekia labracis (Hatschekiidae), which was attached to a scarbreast tuskfin (Choerodon azurio, Labridae), and Asterocheres sp. 1 (Asterocheridae), which was attached to a spirastrellid sponge. Carbon isotope ratios of S. senokuchiae at different stages and Ectinosoma were measured to complement the nutritional insights obtained from gut-content analysis. Our results clearly showed that most S. senokuchiae individuals possessed bacteria in the oral tube or gut regardless of growth stage, whereas the coexisting Ectinosoma and calanoid did not. The carbon isotopic compositions confirmed that S. senokuchiae gains its nutrition from chemoautotrophic bacteria that use the rTCA carbon-fixation pathway. Comparisons with other Siphonostomatoida copepods suggest that Dirivultidae are specifically adapted to feed on bacteria at hydrothermal-vent chimneys, allowing their high dominance and evolutionary success in these habitats. more...

Dirivultid copepods (Siphonostomatoida), one of the most successful meiobenthic organisms found at deep-sea hydrothermal vents, have been the focus of most previous ecological studies among meiofauna in these habitats. The ecology of Harpacticoida, a major benthic copepod group in typical deep-sea floor, however, is not well understood in terms of variations in community structure and controlling factors at venting sites. The spatial heterogeneities in benthic harpacticoid composition and their association with environmental parameters were investigated at hydrothermal vent chimney structures in the calderas of three neighbouring sea knolls (Bayonnaise Knoll, Myojin Knoll and Myojin-sho Caldera) in the western North Pacific. While a previous study had reported the distribution of dirivultids was strongly associated with spatial differences in stable carbon isotopic signatures (δ13C) of organic matter in the detritus on active chimneys in the field, multivariate analyses detected no significant corelation between the parameter and harpacticoid composition in this study. Instead, high associations of the harpacticoid composition with differences in water depth and total organic carbon (TOC) concentration were detected. Ectinosomatidae dominated at vent sites with lower TOC values in the shallowest Bayonnaise Knoll, while they were less prevalent at deeper vent fields in the other knolls, where Miraciidae was the most abundant family. This study indicated the availability of vent chemoautotrophic carbon is not a primary factor controlling the composition of harpacticoids even in the habitats on the hydrothermal vents, but instead by the food amount, regardless of its resources (including marine snow from the sea surface), in the study area. more...

Hypoxia in bottom environments of coastal marine ecosystems is a serious problem adversely affecting both benthic life and local fisheries. In this study, we monitored abundance, composition, and feeding types of nematode communities under pre-, mid-, and post-hypoxic conditions in Omura Bay, Nagasaki, Japan, for three consecutive years (2013-2015). The bay is almost completely enclosed, and experiences hypoxia at the bottom every summer. A positive correlation was found between dissolved oxygen (DO) concentration and nematode abundance over the entire sampling period (p3 mg L?1). These findings will help us to understand how global trends of ocean deoxygenation could shape the meiobenthic community and alter benthic ecosystem functioning in coastal areas., Plankton and Benthos Research, 13(2), pp.59-65; 2018 more...

The present study investigated spatiotemporal variations in meiofaunal abundance and composition at high taxonomic levels, and their associations with certain measures of food availability around hydrothermal vents on chimney structures and in adjacent non-vent fields in the calderas of three neighboring seamounts (Bayonnaise Knoll, Myojin Knoll, and Myojin-sho Caldera), in the Izu-Ogasawara Arc, western North Pacific Ocean. Total meiofaunal abundance in seafloor sediment at the bases of vent chimneys appeared to be greater than that in other non-vent habitats outside or inside the calderas of all seamounts, which was partly explained by temporal variations at the bases of the chimneys. There was no significant difference in the mean meiofaunal abundances among those habitats. A typical deep-sea meiofaunal composition (nematodes as the most abundant taxon, harpacticoid copepods as the second) was observed in the seafloor sediments in the non-vent fields, and even in the sediments at chimney bases. This was significantly different from the meiofaunal composition observed on the surfaces of vent chimneys, where copepods and their nauplii were most abundant. This spatial difference was significantly correlated with a difference in stable carbon isotope ratios (δ13C) of organic matter in sediment, suggesting that the availability of chemosynthetic food controls the spatial differences in meiofaunal composition around these hydrothermal vents, even at a high taxonomic level. more...

In contrast to specific large benthic invertebrates in chemosynthetic ecosystems such as hydrothermal vents, meiofaunal communities in such habitats have been reported to have strong taxonomic overlap with meiofauna in the adjacent “normal” environments. However, meiofauna have only recently been included in studies of those environments and detailed information on these communities is still rare. This is especially true in the Northwest Pacific Ocean, even though there are many seamounts with active vents in the calderas of the region. Nematode community composition at the genus level in sediments from a hydrothermal vent field in the caldera of Myojin Knoll (32°06′N, 139°52′E, depth 1,300 m), a seamount on the Izu-Ogasawara Arc, Japan, was investigated for the first time and was compared with adjacent non-vent areas inside and outside the caldera. Multivariate analyses showed that the composition of nematodes in the hydrothermal field was significantly different from that in the non-hydrothermal fields around the caldera. However, the common genera, such as Oxystomina, Pareudesmoscolex, Desmoscolex, and Microlaimus were found in two, or all three vent fields while their rank contributions differed among the three fields. When the data from Myojin Knoll were compared with those from other deep-sea vent environments in different regions (e.g., North Fiji Basin, East Pacific Rise, Mid-Atlantic Ridge), the nematode composition in the vent field of the Myojin caldera was more similar to that of the non-vent fields around the caldera than the composition in vent fields of other regions. These data from the Northwest Pacific Ocean also suggest the absence of long-range transport systems and local adaptations for meiofauna in hydrothermal vent fields. more...

We investigated the genus diversity and community composition of harpacticoid copepods and their relationship with environmental factors around the Kuril Trench (490–7090 m). Harpacticoid densities did not decrease with water depth and were highest at 1000 m water depth. Diversity values based on the number of genera, Shannon diversity and the expected number of genera (rarefaction) indicated unimodal patterns with water depth, with peaks at intermediate depth; genus evenness increased with water depth and slightly decreased at hadal depths. This result suggested that the general relationship between water depth and diversity described for macrofauna and megafauna could be extended to meiofauna across all depth ranges. However, the regulating factor that affects harpacticoid diversity could not be identified. The community composition of harpacticoids gradually changed with water depth (from bathyal to hadal depths). In addition, comparison of assemblages between the trench slope, trench floor and abyssal plain suggested that the community found at hadal depth was largely different from those found on the trench slope and abyssal plain. Multivariate analyses suggested that water depth, or certain factors associated with water depth, affects harpacticoid assemblages around the Kuril Trench. more...

In tidal flat sediments, larger invertebrates often modify the sedimentary environment in a manner that causes smaller animals, such as meiofauna, to become more abundant. In other words, macrofauna can “promote” meiofauna. In summer (August) and autumn (November/early December) 2007, we investigated centimetre-scale horizontal and vertical profiles of total metazoan meiofaunal abundance and community structure around burrows of Uca lactea (De Haan, 1835) (fiddler crabs) and Scopimera globosa (De Haan, 1835) (sand bubbler crabs) on an intertidal sandflat of the Amakusa Islands, western Japan. Meiofaunal community structure changed significantly with sediment depth around burrows of U. lactea in both seasons, whereas vertical differences were less clear for S. globosa. Although no evidence was found that total meiofaunal abundance or the abundances of certain taxonomic groups were positively influenced by burrows of S. globosa, the abundance of nematodes in subsurface sediment around burrows of U. lactea was significantly higher than in controls in autumn. High concentrations of fresh organic matter had not accumulated in the sediment around burrows of either species of crab. Uca lactea, however, made its burrows in significantly finer sediment than did S. globosa. One possibility is that differences in meiofaunal distribution in sediment around the burrows of the two crabs were the result of habitat and behavioural differences between the species. more...

To examine the specific features of trench communities, spatial changes in the assemblages of harpacticoids were investigated at the family level around the Ryukyu Trench (the Ryukyu region) and Kuril Trench (the Kuril region). In the Ryukyu region, there were high average dissimilarities in the harpacticoid assemblages among the trench, trench slope and abyssal plain, indicating that the assemblage structures differ substantially between these topographic settings at the family level. Conversely, in the Kuril region, the average dissimilarities in harpacticoid assemblages between the trench and the trench slope and between the trench and the abyssal plain were lower than that between the slope and the abyssal plain. This result suggests that the hadal assemblage is a transition zone between the slope and the abyssal plain in this region. In addition, the analyses indicate that the composition of harpacticoid assemblages is influenced by the quantity of organic matter in the Ryukyu region, while sediment properties play a key role in the Kuril region. Comparisons of the assemblages between the two regions, however, revealed that the average dissimilarities between the trenches and between the abyssal plains were higher than that between the adjacent slopes. This result suggests that interchange among regions is difficult for deep-sea benthic animals, including harpacticoid copepods, likely due to the presence of physical barriers around trenches. more...

The abundance and biomass of metazoan meiofauna and their relationships with environmental factors [chloroplastic pigment equivalents (CPE) and sediment characteristics] were studied quantitatively around and within the Kuril Trench (560–7090 m) and the Ryukyu Trench (1290–7150 m), which are located in eutrophic and oligotrophic regions, respectively, of the western North Pacific. Faunal abundance and biomass, as well as the CPE content of sediments, were considerably higher in the Kuril region than in the Ryukyu region. In both cases, CPE tended to decrease with water depth, but relatively high values were found in the deepest areas, suggesting that organic matter has accumulated in both trenches. Meiofaunal abundance and biomass were lower than expected from sediment CPE values at hadal stations below 6000 m. Differences in the density and biomass of meiofauna between these two trenches appeared to reflect differences in overall ocean productivity above them. When the analysis was restricted to each region, however, no association was found between the abundance and biomass of meiofauna and food availability. Furthermore, the factors regulating the bathymetric patterns in these meiofaunal parameters appeared to differ between the two trenches. more...

We investigated the sex differences in the spatiotemporal distribution, body length, and gut contents of adult Neocervinia itoi, the most abundant cerviniid harpacticoid in Sagami Bay, Japan. Two other cerviniid species, Cerviniopsis sp. A and Cervinia bradyi, were also examined for comparison. The density of N. itoi tended to be higher at stations in or below sea bights with steep slopes in the bay, although there was no correlation between their distribution and chloroplastic pigment equivalent (CPE) in the sediment. In general, the sex ratio was strongly biased toward females in this species; the overall mean percentage of males was approximately 23% of adults. The sex ratio seemed to fluctuate temporally, even at the same site, although this fluctuation was not statistically significant. Comparisons of body size and sex ratio between the three species suggest that sampling bias was not the only cause for the observed skewed sex ratio. Distinct sex differences were observed in gut contents of N. itoi. Detritus-like gut contents were clearly observed in the urosomes of almost all females, whereas few males had gut contents. This result suggests that males do not forage during the adult stage. This non-feeding habit of males may result in a shorter lifespan than that of females and may be one cause of the skewed sex ratio. It remains unknown, however, whether this is a general trend among cerviniid species. more...

We examined the trophic levels of deep-sea benthic foraminifera and metazoans based on stable carbon and nitrogen isotopic compositions of soft tissue to evaluate the role of foraminifera in deep-sea benthic ecosystems. Living benthic foraminifera and metazoans were collected from 2 bathyal sites in Sagami Bay, Japan (water depths 750 and 1430 m) on 3 occasions (April 2004, November 2004 and August 2005). Both carbon and nitrogen isotopic compositions significantly dif- fered among the analysed foraminiferal species. At the deeper site δ 15 N of the benthic foraminifera ranged from 6.7 to 11.0‰ (typically 7 to 10‰) with considerable interspecies variations. This implies that most benthic foraminifera utilize primarily surface sediments (4.5‰) or particulate organic mat- ter (6.4‰) as their food sources. Many metazoan meiobenthic organisms, in particular polychaetes of meiofaunal size, some harpacticoid copepods, and kinorhynchs (examined only at the shallower site), exhibited δ 15 N heavier than foraminifera, suggesting that they occupy higher trophic levels than benthic foraminifera. Macro- and megabenthos (spatangoids, ophiuroids and Dentalioida) exhibited δ 15 N of 10 to 14‰, suggesting they belong in trophic levels 1 to 2 steps higher than metazoan meiobenthos and benthic foraminifera. Similar isotopic trends were observed at the shallower site. Combining the isotopic evidences and the observations on gut contents of some metazoan meio- benthos, together with previous experimental results, the benthic foraminifera in the bathyal Sagami Bay are considered a bridge in the energy flow from phytodetritus and sediments to metazoans. more...

To estimate species turnover rates on scales of several tens of km in deep-sea benthic animals, we analyzed spatial and inter-annual changes in species diversity and composition of cerviniids, a typical group of deep-sea harpacticoids, at stations in and around Sagami Bay, central Japan. Associations with environmental factors were also investigated. Generally, bathymetrical patterns in diversity of benthos are unimodal and peak at depths of 2,000–3,000 m. In Sagami Bay, cerviniid diversity did not follow this trend; both species richness and evenness were negatively correlated with water depth. Multivariate analyses [detrended correspondence analysis (DCA) and non-metric multi-dimensional scaling] suggested that temporal changes in species composition of cerviniids are smaller than spatial changes that occur on horizontal scales of several tens of km. Community structure does not change completely on these scales in the bathyal zone around Sagami Bay. DCA also showed that bathymetrical changes in species composition can be regulated by certain factors associated with water depth. more...

Benthic foraminiferal food sources were examined in the central part of Sagami Bay, Japan (water depth 1450 m) based on an in situ feeding experiment with 13 C-labeled food materials. In this study, 3 different 13 C-labeled food materials were used: the unicellular marine algae Dunaliella tertiolecta, the marine diatom Chaetoceros sociale, and the marine bacterium Vibrio algi- nolyticus. The first two are representatives of phytodetritus and the third of organic matter produced in the sediments. Each type of food material was injected into a series of in situ culture cores and incubated for up to 21 d. We observed that some benthic foraminiferal species selectively ingested 13 C-labeled algae from the sedimentary organic matter. On the other hand, benthic foraminifera ingested 13 C-labeled bacteria unselectively from sedimentary organic matter. Total benthic forami- nifera assimilated 8.8 mg C m -2 d -1 of sedimentary organic matter without phytodetritus assimilation. Based on the assimilation rates estimated in this experiment, we recognized 3 types of feeding strat- egy among deep-sea benthic foraminifera in Sagami Bay. There are those that ingest (1) fresh phyto- detritus selectively (phytophagous species: Uvigerina akitaensis, Bolivina spissa, Bolivina pacifica); (2) fresh phytodetritus selectively but sedimentary organic matter as well when phytodetritus is absent (seasonal-phytophagous species: Bulimina aculeata, Textularia kattegatensis, Globobulimina affinis); and (3) sedimentary organic matter at random (deposit feeders: Cyclammina cancellata, Chilostomella ovoidea). These different types of carbon utilization should be considered not only for understanding modern ecosystems on the deep-sea floor but also for paleoceanographic reconstruc- tions using the abundance and distribution, or isotopic composition, of benthic foraminifera. more...

Little is known about temporal changes in the diversity and species composition of deep-sea metazoan meiofauna and their relationships with changes in the food supply. Those changes were studied for benthic copepod assemblages based on 2-year time-series data at a bathyal site in Sagami Bay (1430 m depth), central Japan, where annual fluctuation in the abundance of benthic foraminiferans was previously observed. Species diversity of benthic copepods at the site was as high as, or slightly higher than, that observed at other deep-sea sites, but did not fluctuate temporally through the study period. Multivariate analyses did not reveal any clear seasonal or directional change occurring over the longer term in their species composition, although there was some consistent pattern. These results indicate a lack of, or only weak, seasonality in the diversity and species structure of the deep-sea benthic copepod assemblages, even though the fresh organic food supply fluctuates seasonally. They also suggest that there are differences between copepods and foraminiferans in the response to changes in environmental factors, and that spatial differences in the composition of copepod communities are greater than temporal ones at this deep-sea site. more...

Profiles of the radioisotopes 210 Pb and 137 Cs were determined in 15 sediment cores collected from Sagami Bay, Japan. The activities of 210 Pb ex (unsupported) in core top sediments increased with water depth from 25 dpm g −1 on the upper continental slope off the mouth of Tokyo Bay to an average of 283 dpm g −1 at the deep-sea station SB. The high 210 Pb trapping efficiency of settling particles expected from the results of the sediment trap experiment near the SB site suggests that effective 210 Pb enrichment in surface sediments may occur during resuspension and lateral transportation of particles via the benthic nepheloid layer on the continental slope. In several cores, 137 Cs profiles showed an increase, a distinct peak, and then a decrease to an undetectable level downcore. These profiles can be compared with the temporal change of bomb-produced 137 Cs fallout. The mean sedimentation rates estimated by the 210 Pb ex inventory method, rather than using 210 Pb ex profiles, ranged from 0.06 g cm −2 y −1 to 0.14 g cm −2 y −1 . The average value of the rates in SB cores was calculated to be 0.11 g cm −2 y −1 , which was similar to that calculated under the assumption that the age of the 137 Cs peak corresponds to its maximum fallout year in 1963. Although 137 Cs inventories represented one tenth of the anthropogenic fallout of 137 Cs until 1997, they correlated with the increase in 210 Pb ex inventory. This suggests that the scavenging of refractory 137 Cs as well as 210 Pb by settling particles in the water column can lead to the formation of a time marker layer even in deep-sea sediment core, such as at the SB site. more...

Sex ratios and reproductive activity of benthic copepod assemblages were investigated at the bathyal site (depth 1430 m) in Sagami Bay, central Japan. The ratio of adult females to adult males was approximately 3.5:1, significantly different from 1:1, although this parameter did not show a seasonal pattern. On the other hand, the percentage of ovigerous females among adult females and the ratio of nauplii to total copepods appeared to fluctuate seasonally in 1997 and 1998. Statistical tests, however, could not detect significant difference in either parameter. We discuss the possibility that the reproductive activity of copepods was enhanced by the increased supply of fresh phytodetritus to the sea floor. more...

Deep-sea benthic ecosystems are mainly sustained by sinking organic materials that are produced in the euphotic zone. “Benthic–pelagic coupling” is the key to understanding both material cycles and benthic ecology in deep-sea environments, in particular in topographically flat open oceanic settings. However, it remains unclear whether “benthic–pelagic coupling” exists in eutrophic deep-sea environments at the ocean margins where areas of undulating and steep bottom topography are partly closely surrounded by land. Land-locked deep-sea settings may be characterized by different particle behaviors both in the water column and in relation to submarine topography. Mechanisms of particle accumulation may be different from those found in open ocean sedimentary systems. An interdisciplinary programme, “Project Sagami”, was carried out to understand seasonal carbon cycling in a eutrophic deep-sea environment (Sagami Bay) with steep bottom topography along the western margin of the Pacific, off central Japan. We collected data from ocean color photographs obtained using a sea observation satellite, surface water samples, hydrographic casts with turbidity sensor, sediment trap moorings and multiple core samplings at a permanent station in the central part of Sagami Bay between 1997 and 1998. Bottom nepheloid layers were also observed in video images recorded at a real-time, sea-floor observatory off Hatsushima in Sagami Bay. Distinct spring blooms were observed during mid-February through May in 1997. Mass flux deposited in sediment traps did not show a distinct spring bloom signal because of the influence of resuspended materials. However, dense clouds of suspended particles were observed only in the spring in the benthic nepheloid layer. This phenomenon corresponds well to the increased deposition of phytodetritus after the spring bloom. A phytodetrital layer started to form on the sediment surface about two weeks after the start of the spring bloom. Chlorophyll-a was detected in the top 2 cm of the sediment only when a phytodetritus layer was present. Protozoan and metazoan meiobenthos increased in density after phytodetritus deposition. Thus, “benthic–pelagic coupling” was certainly observed even in a marginal ocean environment with undulated bottom topography. Seasonal changes in features of the sediment–water interface were also documented. more...

Temporal variations of sinking particle flux, together with their organic chemical properties, were monitored in the deep basin of Sagami Bay, Japan, using sediment traps with very high time resolutions from March 1997 to August 1998. At a height of 350 m above the bottom (about 1200 m water depth), the averaged total mass flux was more than 1000 mg/m2/day, which is about 10 times higher than those obtained for open ocean regions near Sagami Bay. While large amounts of phytodetritus, derived from phytoplankton blooms in the surface water, were transported downward in spring, the following extraordinary patterns in the temporal variability of sinking particle flux were also observed: (1) A sustained large flux of sinking particles during low productive periods from summer to winter in 1997. (2) An episodic increase of sinking particle flux in June 1998. (3) A difference in the temporal variability of sinking particles between the spring bloom periods of 1997 and 1998. The content of total organic carbon (TOC) and the stable carbon isotopic ratio (δ13C) of TOC demonstrated that the large fluxes observed in (1) and (2) could be attributed to the resuspension of phytodetritus deposited on the sea floor during the spring bloom period, and the abrupt erosion of surface sediment on the continental slope, respectively. The concentration of suspended particles in the deep water column affect the apparent flux of sinking particles. At the same time, sinking particles exported from surface waters during the spring bloom both decrease and increase suspended particle concentration through scavenging and rebound processes, respectively. Finally, the apparent difference in sinking particle flux between 1997 and 1998, (3), could be explained by differences in the extent of the scavenging process, which depend on the flux and quality of exported particles from the surface waters. more...

An interdisciplinary research project was carried out to understand seasonal carbon cycling in a deep-sea ecosystem in Sagami Bay, central Japan. Temporal-changes in the chloroplastic pigment (CPE) concentration in the sediment, as well as the abundance, the biomass and the metabolic activity of benthic organisms were studied. CPE was detectable throughout the year, and its amount increased in the spring when a fluffy layer was observed on the surface of the sediment. Significant seasonal fluctuation of bacterial abundance was found, but the range was small, the maximal value being only 1.6 times larger than the minimal one. Metabolic activity did not show significant temporal difference. The abundance and biomass of metazoan meiofauna seemed to fluctuate seasonally, but ANOVA did not confirm it statistically. Our results suggest that if enough organic matter is supplied constantly, the deep-sea benthic community will be stable even though seasonality of organic matter flux associated with the spring bloom exists., Un programme de recherche interdisciplinaire a été consacré au cycle saisonnier du carbone dans un écosystème profond de la baie de Sagami, au centre du Japon. Les variations temporelles de la concentration du pigment chloroplastique (CPE) dans le sédiment ont été étudiées, ainsi que l'abondance, la biomasse et l'activité métabolique des organismes benthiques. La concentration CPE est détectable pendant toute l'année, avec une augmentation au printemps lorsqu'une couche pelucheuse est observée à la surface du sédiment. L'abondance bactérienne présente une fluctuation saisonnière significative mais de faible amplitude, avec un rapport de 1,6 entre les valeurs maximale et minimale. L'activité métabolique ne varie pas de manière significative avec le temps. L'abondance et la biomasse de la méiofaune de métazoaires semblent fluctuer avec les saisons, sans confirmation statistique Anova. Les résultats montrent que la communauté benthique profonde reste stable si l'apport de matière organique est suffisant et continu, même avec une variabilité saisonnière associée à la floraison printanière. more...

We measured organic carbon uptake rates by deep-sea benthic foraminifera and studied differences among species, living depth, and seasons to investigate how these protists contribute to carbon consumption on the deep-sea floor. In situ feeding experiments using more...