首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Although the organization patterns of fauna in the deep sea have been broadly documented, most studies have focused on the megafauna. Bivalves represent about 10% of the deep-sea macrobenthic fauna, being the third taxon in abundance after polychaetes and peracarid crustaceans. This study, based on a large data set, examined the bathymetric distribution, patterns of zonation and diversity–depth trends of bivalves from the Porcupine Seabight and adjacent Abyssal Plain (NE Atlantic). A total of 131,334 individuals belonging to 76 species were collected between 500 and 4866 m. Most of the species showed broad depth ranges with some ranges extending over more than 3000 m. Furthermore, many species overlapped in their depth distributions. Patterns of zonation were not very strong and faunal change was gradual. Nevertheless, four bathymetric discontinuities, more or less clearly delimited, occurred at about 750, 1900, 2900 and 4100 m. These boundaries indicated five faunistic zones: (1) a zone above ∼750 m marking the change from shelf species to bathyal species; (2) a zone from ∼750 to 1900 m that corresponds to the upper and mid-bathyal zones taken together; (3) a lower bathyal zone from ∼1900 to 2900 m; (4) a transition zone from ∼2900 to 4100 m where the bathyal fauna meets and overlaps with the abyssal fauna and (5) a truly abyssal zone from approximately 4100–4900 m (the lower depth limit of this study), characterized by the presence of abyssal species with restricted depth ranges and a few specimens of some bathyal species with very broad distributions. The ∼4100 m boundary marked the lower limit of distribution of many bathyal species. There was a pattern of increasing diversity downslope from ∼500 to 1600 m, followed by a decrease to minimum values at about 2700 m. This drop in diversity was followed by an increase up to maximum values at ∼4100 m and then again, a fall to ∼4900 m (the lower depth limit in this study).  相似文献   

2.
The mid-domain effect was tested to evaluate the bathymetric patterns of the polychaete species richness in the Upper and Lower Gulf of California as a possible hypothesis to explain the species richness gradient, exploring the overlapping of species depth ranges towards the middle continental shelf. The bathymetric gradient of the number of species was estimated with the depth ranges of 554 polychaete species, and the mid-domain effect was tested using a Monte Carlo simulation program at bands of 10 m depth. The Upper (251 species) and Lower (491 species) Gulf regions showed clear differences in their faunal composition (Jaccard similarity index = 0.34); the species richness pattern was characterized by a highly significant presence of polychaetes with short depth ranges (< 10 m). The richness distribution could be described as a cubic polynomial curve, but the maximum values in both Gulf regions (141 and 317 species, respectively for Upper and Lower Gulf regions) are strongly biased to shallow waters (40 m). This is not consistent with the peak of diversity at 60–70 m predicted by the model. The observed patterns cannot be reproduced by the mid-domain effect, suggesting the existence of non-random factors affecting the species richness gradients in the Gulf.  相似文献   

3.
The deep sea has been shown to exhibit strong depth zonation in species composition and abundance. Examination of these patterns can offer ecological insight into how organisms adapt and respond to changing environmental parameters that co-occur with depth. Here we provide the first tropical study on bathymetric zonation and other depth-related trends (size, abundance, and species richness) spanning shelf to abyssal depths of scavenging megafauna. Baited time-lapse free-vehicle cameras were used to examine the deep-sea benthic and demersal scavenging communities of the Hawaiian Islands, an area for which the biology and ecology have remained poorly studied below 2000 m. Twenty-two deployments ranging in depth from 250 to 4783 m yielded 37 taxa attracted to bait, including the first known occurrence of the family Zoarcidae in the Hawaiian Islands. Cluster analysis of Bray–Curtis similarity of species peak abundance (nmax) revealed four main faunal zones (250–500, 1000, 1500–3000, and ?4000 m) with significant separation (ANOSIM, global R=0.907, p=0.001) between designated depth groups. A major faunal break was identified at the 500–1000 m transition where species turnover was greatest, coinciding with the location of the local oxygen minimum zone. Dominance in species assemblage shifted from decapod crustaceans to teleosts moving from shallow to deeper faunal zones. Significant size differences in total length with depth were found for two of the four fish species examined. A logarithmic decline was observed in scavenger relative abundance with depth. Evidence of interaction between scavenging species was also noted between Synaphobranchus affinis and Neolithodes sp. (competition) and Histiobranchus sp. and aristeid shrimp (predation), suggesting that interactions between scavengers could influence indices of abundance generated from baited camera data.  相似文献   

4.
The paper describes new deep-water edwardsiid sea anemone Edwardsia sojabio sp. n. which is very common on soft muddy bottoms at lower bathyal and upper abyssal depths in the Sea of Japan. It was recorded in high quantity in depths between 2545 and 3550 m and is the second abyssal species of the genus Edwardsia.  相似文献   

5.
The aim of this study is to compare the depth distributions of four major Southern Ocean macrobenthic epi- and infaunal taxa, the Bivalvia, Gastropoda, Isopoda, and Polychaeta, from subtidal to abyssal depth. All literature data up to summer 2008, as well as the unpublished data from the most recent ANDEEP I–III (Antarctic benthic deep-sea biodiversity: colonisation history and recent community patterns) expeditions to the Southern Ocean deep sea are included in the analysis. Benthic invertebrates in the Southern Ocean are known for their wide bathymetric ranges. We analysed the distributions of four of the most abundant and species-rich taxa from intertidal to abyssal (5200 m) depths in depth zones of 100 m. The depth distributions of three macrofaunal classes (Bivalvia, Gastropoda, Polychaeta) and one order (Isopoda) showed distinct differences. In the case of bivalves, gastropods and polychaetes, the number of species per depth zone decreased from the shelf to the slope at around 1000 m depth and then showed stable low numbers. The isopods showed the opposite trend; they were less species rich in the upper 1000 m but increased in species numbers from the slope to bathyal and abyssal depths. Depth ranges of families of the studied taxa (Bivalvia: 31 families, Gastropoda: 60, Isopoda: 32, and Polychaeta: 46 families) were compiled and illustrated. At present vast areas of the deep sea in the Southern Ocean remain unexplored and species accumulation curves showed that only a fraction of the species have been discovered to date. We anticipate that further investigations will greatly increase the number of species known in the Southern Ocean deep sea.  相似文献   

6.
Macrofaunal polychaete communities (>500 µm) in the South Eastern Arabian Sea (SEAS) continental margin (200–1000 m) are described, based on three systematic surveys carried out in 9 transects (at ~200 m, 500 m and 1000 m) between 7°00′and 14°30′N latitudes. A total of 7938 polychaetes belonging to 195 species were obtained in 136 grab samples collected at 27 sites. Three distinct assemblages were identified in the northern part of the SEAS margin (10–14°30′N), occupying the three sampled depth strata (shelf edge, upper and mid-slope) and two assemblages (shelf edge and slope) in the south (7–10°N). Highest density of polychaetes and dominance of a few species were observed in the shelf edge, where the Arabian Sea oxygen minimum zone (OMZ) impinged on the seafloor, particularly in the northern transects. The resident fauna in this region (Cossura coasta, Paraonis gracilis, Prionospio spp. and Tharyx spp.) were characteristically of smaller size, and well suited to thrive in the sandy sediments in OMZ settings. Densities were lowest along the most northerly transect (T9), where dissolved oxygen (DO) concentrations were extremely low (<0.15 ml l−1, i.e.<6.7 μmol l−1). Beyond the realm of influence of the OMZ (i.e. mid-slope, ~1000 m), the faunal density decreased while species diversity increased. The relative proportion of silt increased with depth, and the dominance of the aforementioned species decreased, giving way to forms such as Paraprionospio pinnata, Notomastus sp., Eunoe sp. and lumbrinerids. Relatively high species richness and diversity were observed in the sandy sediments of the southern sector (7–9°N), where influence of the OMZ was less intense. The area was also characterized by certain species (e.g. Aionidella cirrobranchiata, Isolda pulchella) that were nearly absent in the northern region. The gradients in DO concentration across the core and lower boundary of the OMZ, along with bathymetric and latitudinal variation in sediment texture, were responsible for differences in polychaete size and community structure on the SEAS margin. Spatial and temporal variations were observed in organic matter (OM) content of the sediment, but these were not reflected in the density, diversity or distribution pattern of the polychaetes.  相似文献   

7.
We analysed the reproductive biology of the asteroid species Styracaster elongatus based on time-series samples from a 5000-m-deep site on the Porcupine Abyssal Plain (N.E. Atlantic). The ratio of males to females, the gonadosomatic index (GI), and pyloric caecum index (PCI) were determined and the results were corroborated by histological examination of the gonads. Fecundity and oocyte-size distribution were determined by histological and image analyses. Styracaster elongatus is a gonochoric asteroid and the ratio of males to females was not significantly different throughout the year. Oogenesis was asynchronous. The previtellogenic oocytes grew to a size of ～230 μm before undergoing vitellogenesis. Maximum oocyte size was ～620 μm. The ovary volume was mainly occupied by small previtellogenic oocytes (100–150 μm) at any one time. Mean GI was 6.38±3.30 for females and 9.04±4.1 for males. Mean PCI was 7.44±1.66 for females and 7.66±1.46 for males. Mean fecundity was 16,373±5988 oocites per female. There were no seasonal variations in GI and fecundity. There was evidence of a pyiloric caecum seasonal development for females and males. For S. elongatus there is no direct relationship among seasonal primary production at the surface and production of vitellogenic oocytes. Nevertheless, this species takes advantage of the pulse of phytodetritus to the seabed by increasing the storage of nutrients in the pyloric caecum in order to maintain a constant production of eggs and sperm.  相似文献   

8.
A quantitative study of metazoan meiofauna was carried out on bathyal sediments (305, 562, 830 and 1210 m) along a transect within and beneath the oxygen minimum zone (OMZ) in the southeastern Pacific off Callao, Peru (12°S). Meiobenthos densities ranged from 1517 (upper slope, middle of OMZ) to 440–548 ind. 10 cm−2 (lower slope stations, beneath the OMZ). Nematodes were the numerically dominant meiofaunal taxon at every station, followed by copepods and nauplii. Increasing bottom-water oxygen concentration and decreasing organic matter availability downslope were correlated with observed changes in meiofaunal abundance. The 300-m site, located in the middle of the OMZ, differed significantly in meiofaunal abundance, dominance, and in vertical distribution pattern from the deeper sites. At 305 m, nematodes amounted to over 99% of total meiofauna; about 70% of nematodes were found in the 2–5 cm interval. At the deeper sites, about 50% were restricted to the top 1 cm. The importance of copepods and nauplii increased consistently with depth, reaching ∼12% of the total meiofauna at the deepest site. The observation of high nematode abundances at oxygen concentrations <0.02 ml l−1 supports the hypothesis that densities are enhanced by an indirect positive effect of low oxygen involving (a) reduction of predators and competitors and (b) preservation of organic matter leading to high food availability and quality. Food input and quality, represented here by chloroplastic pigment equivalents (CPE) and sedimentary labile organic compounds (protein, carbohydrates and lipids), were strongly, positively correlated with nematode abundance. By way of contrast, oxygen exhibited a strong negative correlation, overriding food availability, with abundance of other meiofauna such as copepods and nauplii. These taxa were absent at the 300-m site. The high correlation of labile organic matter (C-LOM, sum of carbon contents in lipids, proteins and carbohydrates) with CPE (Pearson's r=0.99, p<0.01) suggests that most of the sedimentary organic material sampled was of phytodetrital origin. The fraction of sediment organic carbon potentially available to benthic heterotrophs, measured as C-LOM/Total organic carbon, was on average 17% at all stations. Thus, a residual, refractory fraction, constitutes the major portion of organic matter at the studied bathyal sites.  相似文献   

9.
As part of a multidisciplinary cruise to the Porcupine Abyssal Plain (PAP) study site (49°00′N 16°30′W), in June and July 2006, observations were made of the vertical nitrate flux due to turbulent mixing. Daily profiles of nitrate and turbulent mixing, at the central PAP site, give a mean nitrate flux into the euphotic zone of 0.09 (95% confidence intervals: 0.05–0.16) mmol N m−2 d−1. This is a factor of 50 lower than the mean observed rate of nitrate uptake within the euphotic zone (5.1±1.3 mmol N m−2 d−1). By using our direct observations to ‘validate’ a previously published parameterisation for turbulent mixing, we further quantify the variability in the vertical turbulent flux across a roughly 100×100 km region centred on the PAP site, using hydrographic data. The flux is uniformly low (0.08±0.26 mmol N m−2 d−1, the large standard deviation being due to a strongly non-Gaussian distribution) and is consistent with direct measurements at the central site. It is demonstrated that on an annual basis convective mixing supplies at least 40-fold more nitrate to the euphotic zone than turbulent mixing at this location. Other processes, such as those related with mesoscale phenomena, may also contribute significantly.  相似文献   

10.
The results from a time series study (1989–2005) at a depth of 4850 m on the Porcupine Abyssal Plain, NE Atlantic, are presented, showing radical changes in the density of large invertebrates (megafauna) over time. Major changes occurred in a number of different taxa between 1996 and 1999 and then again in 2002. One species of holothurian, Amperima rosea, was particularly important, increasing in density by over three orders of magnitude. There were no significant changes in total megafaunal biomass during the same period. Peaks in density were correlated to reductions in mean body size, indicating that the increases were related to large-scale recruitment events. The changes occurred over a wide area of the Porcupine Abyssal Plain. Comparisons made with changes in the density of protozoan and metazoan meiofauna, and with macrofauna, showed that major changes in community structure occurred in all size fractions of the benthic community at the same time. This suggests that the faunal changes were driven by environmental factors rather than being stochastic population imbalances of one or two species. Large-scale changes in the flux of organic matter to the abyssal seafloor have been noted in the time series, particularly in 2001, and may be related to the sudden mass occurrence of A. rosea the following year. Time-varying environmental factors are important in influencing the occurrence of megafauna on the abyssal seafloor.  相似文献   

11.
Seafloor mapping of the central Lomonosov Ridge using a multibeam echo-sounder during the Beringia/Healy–Oden Trans-Arctic Expedition (HOTRAX) 2005 shows that a channel across the ridge has a substantially shallower sill depth than the ∼2500 m indicated in present bathymetric maps. The multibeam survey along the ridge crest shows a maximum sill depth of about 1870 m. A previously hypothesized exchange of deep water from the Amundsen Basin to the Makarov Basin in this area is not confirmed. On the contrary, evidence of a deep-water flow from the Makarov to the Amundsen Basin was observed, indicating the existence of a new pathway for Canadian Basin Deep Water toward the Atlantic Ocean. Sediment data show extensive current activity along the ridge crest and along the rim of a local Intra Basin within the ridge structure.  相似文献   

12.
We present a 3-year multidisciplinary biogeochemical data set taken in situ at the Porcupine Abyssal Plain (PAP) time-series observatory in the Northeast Atlantic (49°N, 16.5°W; water depth ∼4850 m) for the period 2003 to 2005. The high-resolution year-round autonomous measurements include temperature, salinity, chlorophyll-a (derived from in situ chlorophyll-fluorescence) and inorganic nitrate, all at a nominal depth of 30 m on an Eulerian observatory mooring. This study compares these in situ time-series data with satellite chlorophyll-a data, regional data from a ship of opportunity, mixed-layer depth measurements from profiling Argo floats and lateral advection estimates from altimetry. This combined and substantial data set is used to analyse seasonal and inter-annual variability in hydrography and nitrate concentrations in relation to convective mixing and lateral advection. The PAP observatory site is in the inter-gyre region of the North Atlantic where convective mixing ranges from 25 m in the summer to over 400 m in winter when nutrients are supplied to the surface. Small inter-annual changes in the winter mixed layer can result in large changes in nitrate supply and productivity. However the decrease in maximum winter nitrate over the three-year period, from 10 to 7 mmol m−3, cannot be fully explained by convective mixing. Trajectories leading to the PAP site, computed from altimetry-derived geostrophic velocities, confirm that lateral advection cannot be ignored at this site and may be an important process along with convective mixing. Over the three years, there is an associated decrease in new production calculated from nitrate assimilation from 85.4 to 40.3±4.3 gCm−2 a−1. This confirms year-to-year variability in primary production seen in model estimates for the region. The continuous in situ dataset also shows inter-annual variation in the timing of the spring bloom due to variations in heat flux; the 2005 bloom occurred earlier than in 2004.  相似文献   

13.
There have been comparatively few large-scale studies on spatial genetic structure of bathyal seafloor fauna, despite the importance of these data to the successful management of the world's oceans. We use a comparative analysis of mitochondrial DNA from five bathyal (200–3500 m) species of brittle-stars (Ophiuroidea) to assess phylogeographic structure along an extensive (8000 km) longitudinal gradient at temperate latitudes (28–56°S) from south-west Australia (113°E) to seamounts east of New Zealand (175°W). We found no evidence of a genetic discontinuity between Australia and New Zealand, either across the temperate Tasman Sea or across the Southern Ocean between the South Tasman Rise and the Macquarie Ridge. However, there were latitudinal phylogeographical breaks between tropical, temperate and polar regions; longitudinal breaks across the eastern Indian Ocean; and a bathymetric break at approximately 1700 m. Although there was limited regional structure in the frequency of haplotype distributions within the major clades, and no clade appeared to be strictly panmictic, the regional structure in general was not concordant with a simple isolation-by-distance model. Demographic structure varied with three clades having a simplified haplotype network, low effective population sizes and no evidence of significant population expansion, and two clades having a high diversity of haplotypes, relatively high effective population sizes and signs of recent population expansion. These results are discussed with respect to putative dispersal strategies. We hypothesise that the ‘brooding’ species produce both brooded young and pelagic larvae, allowing for both the maintenance of local populations and long-distance dispersal.  相似文献   

14.
A study was carried out to assess primary production and associated export flux in the coastal waters of the western Antarctic Peninsula at an oceanographic time-series site. New, i.e., exportable, primary production in the upper water-column was estimated in two ways; by nutrient deficit measurements, and by primary production rate measurements using separate 14C-labelled radioisotope and 15N-labelled stable isotope uptake incubations. The resulting average annual exportable primary production estimates at the time-series site from nutrient deficit and primary production rates were 13 and 16 mol C m−2, respectively. Regenerated primary production was measured using 15N-labelled ammonium and urea uptake, and was low throughout the sampling period.The exportable primary production measurements were compared with sediment trap flux measurements from 2 locations; the time-series site and at a site 40 km away in deeper water. Results showed ∼1% of the upper mixed layer exportable primary production was exported to traps at 200 m depth at the time-series site (total water column depth 520 m). The maximum particle flux rate to sediment traps at the deeper offshore site (total water column depth 820 m) was lower than the flux at the coastal time-series site. Flux of particulate organic carbon was similar throughout the spring–summer high flux period for both sites. Remineralisation of particulate organic matter predominantly occurred in the upper water-column (<200 m depth), with minimal remineralisation below 200 m, at both sites. This highly productive region on the Western Antarctic Peninsula is therefore best characterised as ‘high recycling, low export’.  相似文献   

15.
Trends in the abundance, diversity and taxonomic composition of ‘live’ (rose Bengal stained) foraminiferal assemblages (0-1 cm layer, >63-μm fraction) were analysed in replicate multiple corer samples collected at the Porcupine Abyssal Plain (48° 50’ N, 16° 30’ W, 4850 m water depth) over a 13-yr period (1989-2002). Total densities were significantly higher in 1996-2002 compared to 1989-1994, a change coincident with a spectacular rise in the density of the holothurian Amperima. However, total densities exhibited no significant relation to seasons or any significant correlation with modelled organic matter flux, the North Atlantic Oscillation (NAO) index, Amperima densities, or megafaunal assemblage composition. Over the same period, species richness and diversity measures decreased and dominance increased, although not significantly. Multivariate analyses revealed three assemblages represented by samples collected in 1989-1994, 1996-July 1997 and October 1997-October 2002. These reflected temporal changes in the densities of higher taxa and species. Trochamminaceans, notably a small undescribed species, increased from 5-9% (1989-1994) to 29-40% (1996-2002) of the assemblage with a corresponding rise in absolute abundance. Species of Hormosinacea and Lagenammina also tended to increase in density from 1996/1997 onwards. Rotaliids, dominated by Alabaminella weddellensis and Epistominella exigua, showed a bimodal distribution over time with peak densities in May 1991 (32%) and September 1998 (28%) and lowest densities in 1996-1997. Responses by these species to seasonal phytodetritus inputs probably explain the relative abundance of E. exigua, and to a lesser extent A. weddellensis, in 1989 and 1991 when phytodetritus was present. A qualitative change in the phytodetrital food, repackaging of food by megafauna, increased megafaunal disturbance of the surficial sediment, or a combination of these factors, are possible explanations for the dominance of trochamminaceans from 1996 onwards. The miliolid Quinqueloculina sp. was virtually absent in multicore samples (0-1 cm, >63-μm fraction) from 1989-1994, peaked in September 1996 (22%) when degraded phytodetritus was present on core surfaces, was less common in March 1997, and thereafter was relatively uncommon. However, horizontally sliced box-core samples (0-5 cm, >250-μm fraction) revealed that large specimens were more abundant in March 1997, and also were concentrated in deeper sediment layers, than in September 1996. We suggest that Quinqueloculina sp. migrated to the sediment surface in response to a 1996 flux event, grew and reproduced, before migrating back into deeper layers as the phytodetrital food became exhausted. Overall, the abyssal time-series revealed decadal-scale changes among shallow-infaunal foraminifera, more or less coincident with changes in the megafauna, as well as indications of shorter-term events related to seasonally-pulsed phytodetrital inputs.  相似文献   

16.
In the framework of the deep-sea environmental programme BIOZAIRE (Ifremer-Total), colonization trays were deployed for 283–433 days at three sites along the equatorial West African margin: ZA at 1300-m depth, ZC at 4000-m depth far from the Congo canyon and ZD at 4000-m depth close to the Congo canyon. The experiments aimed at determining the influence of depth and local environmental settings on macrofaunal colonization patterns and organic carbon degradation rates. The trays were filled with glass beads and this artificial substrate was enriched with ground particulate organic matter in a gradient of 0%, 0.34%, 1.02% and 3.43% organic carbon. The highest rates of organic carbon degradation ranged, according to the duration of the experiments, from 1.59 to 2.36 gC m−2 day−1 but were independent of depth or location. Colonization rates, conversely, varied by one order of magnitude between bathyal and abyssal experiments. The influence of experimental treatments on the structure of the colonizing macrofauna also varied according to location and depth. At ZA, colonization patterns were highly predictable and driven by a shift in dominance of opportunistic taxa along the enrichment gradient. To a lesser extent, this was also true at ZD, near the Congo canyon, while at ZC the treatments had no significant effect on the composition of the colonizing fauna. At abyssal depth, high rates of organic matter degradation associated with low rates of colonization suggested that pulse of organic matter would mainly benefit the resident community. At bathyal depth, high colonization rates of a specialized fauna might conversely play an important role in the functioning of the ecosystem. The regional and local coexistence of an opportunistic fauna via a spatial storage effect associated with dispersal might significantly contribute to the maintenance of high diversity on continental margins.  相似文献   

17.
Deep-sea benthic communities and their structural and functional characteristics are regulated by surface water processes. Our study focused on the impact of changes in water depth and food supplies on small-sized metazoan bottom-fauna (meiobenthos) along a bathymetric transect (1200–5500 m) in the western Fram Strait. The samples were collected every summer season from 2005 to 2009 within the scope of the HAUSGARTEN monitoring program. In comparison to other polar regions, the large inflow of organic matter to the sea floor translates into relatively high meiofaunal densities in this region. Densities along the bathymetric gradient range from approximately 2400 ind. 10 cm-2 at 1200 m to approximately 300 ind. 10 cm-2 at 4000 m. Differences in meiofaunal distribution among sediment layers (i.e., vertical profile) were stronger than among stations (i.e., bathymetric gradient). At all the stations meiofaunal densities and number of taxa were the highest in the surface sediment layer (0–1 cm), and these decreased with increasing sediment depth (down to 4–5 cm). However, the shape of the decreasing pattern differed significantly among stations. Meiofaunal densities and taxonomic richness decreased gradually with increasing sediment depth at the shallower stations with higher food availability. At deeper stations, where the availability of organic matter is generally lower, meiofaunal densities decreased sharply to minor proportions at sediment depths already at 2–3 cm. Nematodes were the most abundant organisms (60–98%) in all the sediment layers. The environmental factors best correlated to the vertical patterns of the meiofaunal community were sediment-bound chloroplastic pigments that indicate phytodetrital matter.  相似文献   

18.
Since the first major hadal sampling efforts in the 1950s, crustaceans of the order Decapoda have been thought absent from the hadal zone (6000–11,000 m) with no representatives documented >5700 m. A baited video lander deployed at 6007, 6890 and 7966 m in the Kermadec Trench, 8798 and 9729 m in the Tonga Trench (SW Pacific), 6945 and 7703 m in the Japan Trench and 5469 m in the Marianas region (NW Pacific) has now revealed a conspicuous presence of the Benthesicymid prawn Benthesicymus crenatus Bate 1881. Decapods were observed at all sites except at 7966 m in the Kermadec Trench and the two Tonga Trench sites, making the deepest finding 7703 m in the Japan Trench, 2000 m deeper than previously thought. These natantian decapods were readily attracted to fish bait and, rather than feeding on the bait itself, were observed preying upon smaller scavenging amphipods. These are the first observations of predation in the hadal zone. In less than 10 h of bottom time, 12 observations of 10 individuals were documented at 6007 m and 5 observations of 3 individuals were documented at 6890 m in the Kermadec Trench. In the Japan Trench at 6945 m 29 observations of 20 individuals were documented whilst only one individual was seen at 7703 m. Two individuals were observed in the abyssal Marianas Region (5575 m). Also, in the Kermadec Trench, individual caridean prawns (Acanthephyra spp.) were observed at 6007 and 6890 m, proving categorically that the crustacean order of Decapoda is represented in the hadal zone.  相似文献   

19.
Deep-water sharks are considered highly vulnerable species due to their life characteristics and very low recovery capacity against overfishing. However, there is still limited information on the ecology or population connectivity of these species. The aim of this study was to investigate if the species Centrophorus squamosus could make long displacements and thus confirm the existence of connectivity between different deep-water areas. In addition, the study was the first attempt to use tagging techniques on deep-water sharks, since it has never been undertaken before. Five C. squamosus were tagged with satellite tags (PAT) in the El Cachucho Marine Protected Area (Le Danois Bank) located in waters of the North of Spain, Cantabrian Sea (NE Atlantic). Data from four of these tags were recovered. One of the sharks travelled approximately 287 nm toward the north east (French continental shelf) hypothetically following the continental slope at a mean depth of 901±109 m for 45 days. Two other sharks spent almost 4 months traveling, in which time they moved 143 and 168 nm, respectively, to the west (Galician coast). Finally, another leafscale gulper shark travelled to the NW (Porcupine Bank) during a period of 3 months at a mean depth of 940±132 m. Depth and temperature preferences for all the sharks are discussed. Minimum and maximum depths recorded were 496 and 1848 m, respectively. The temperature range was between 6.2 and 11.4 °C, but the mean temperature was approximately 9.9±0.7 °C. The sharks made large vertical displacements throughout the water column with a mean daily depth range of 345±27 m. These preliminary results support the suggestion of a whole population in the NE Atlantic and confirm the capacity of this species to travel long distances.  相似文献   

20.
Quantitative collections of tubeworm- and mussel-associated communities were obtained from 3 cold seep sites in the deep Gulf of Mexico: in Atwater Valley at 1890 m depth, in Alaminos Canyon at 2200 m depth, and from the Florida Escarpment at 3300 m depth. A total of 50 taxa of macro- and megafauna were collected including 2 species of siboglinid tubeworms and 3 species of bathymodiolin mussels. In general, the highest degree of similarity was between communities collected from the same site. Most of the dominant families at the well-characterized upper Louisiana slope seep sites of the Gulf of Mexico were present at the deep sites as well; however, there was little overlap at the species level between the upper and lower slope communities. One major difference in community structure between the upper and lower slope seeps was the dominance of the ophiuroid Ophioctenella acies in the deeper communities. The transition between upper and lower slope communities appears to occur between 1300 and 1700 m based on the number of shared species with the Barbados seeps at either end of this depth range. Seep communities of the deep Gulf of Mexico were more similar to the Barbados Accretionary Prism seep communities than they were to either the upper slope Gulf of Mexico or Blake Ridge communities based on numbers of shared species and Bray–Curtis similarity values among sites. The presence of shared species among these sites suggests that there is ongoing or recent exchange among these areas. An analysis of bathymodioline mussel phylogeography that includes new collections from the west coast of Africa is presented. This analysis also suggests recent exchange across the Atlantic equatorial belt from the Gulf of Mexico to the seeps of the West Nigerian margin.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号