New contribution to the knowledge of the mesopelagic cephalopod community off the western Canary Islands slope
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Mesopelagic zone
Cephalopod
Bathyal zone
Archipelago
Deep ocean microbial communities rely on the organic carbon produced in the sunlit ocean, yet it remains unknown whether surface processes determine the assembly and function of bathypelagic prokaryotes to a larger extent than deep-sea physicochemical conditions. Here, we explored whether variations in surface phytoplankton assemblages across Atlantic, Pacific and Indian ocean stations can explain structural changes in bathypelagic (ca. 4,000 m) free-living and particle-attached prokaryotic communities (characterized through 16S rRNA gene sequencing), as well as changes in prokaryotic activity and dissolved organic matter (DOM) quality. We show that the spatial structuring of prokaryotic communities in the bathypelagic strongly followed variations in the abundances of surface dinoflagellates and ciliates, as well as gradients in surface primary productivity, but were less influenced by bathypelagic physicochemical conditions. Amino acid-like DOM components in the bathypelagic reflected variations of those components in surface waters, and seemed to control bathypelagic prokaryotic activity. The imprint of surface conditions was more evident in bathypelagic than in shallower mesopelagic (200-1,000 m) communities, suggesting a direct connectivity through fast-sinking particles that escape mesopelagic transformations. Finally, we identified a pool of endemic deep-sea prokaryotic taxa (including potentially chemoautotrophic groups) that appear less connected to surface processes than those bathypelagic taxa with a widespread vertical distribution. Our results suggest that surface planktonic communities shape the spatial structure of the bathypelagic microbiome to a larger extent than the local physicochemical environment, likely through determining the nature of the sinking particles and the associated prokaryotes reaching bathypelagic waters.
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Abstract. The faecal pellets (FPs) of zooplankton can be important vehicles for the transfer of particulate organic carbon (POC) to the deep ocean, often making large contributions to carbon sequestration. However, the routes by which these FPs reach the deep ocean have yet to be fully resolved. We address this by comparing estimates of copepod FP production to measurements of copepod FP size, shape, and number in the upper mesopelagic (175–205 m) using Marine Snow Catchers, and in the bathypelagic using sediment traps (1500–2000 m). The study is focussed on the Scotia Sea, which contains some of the most productive regions in the Southern Ocean, where epipelagic FP production is likely to be high. We found that, although the size distribution of the copepod community suggests that high numbers of small FPs are produced in the epipelagic, small FPs are rare in the deeper layers, implying that they are not transferred efficiently to depth. Consequently, small FPs make only a minor contribution to FP fluxes in the meso- and bathypelagic, particularly in terms of carbon. The dominant FPs in the upper mesopelagic were cylindrical and elliptical, while ovoid FPs were dominant in the bathypelagic. The change in FP morphology, as well as size distribution, points to the repacking of surface FPs in the mesopelagic and in situ production in the lower meso- and bathypelagic, which may be augmented by inputs of FPs via zooplankton vertical migrations. The flux of carbon to the deeper layers within the Southern Ocean is therefore strongly modulated by meso- and bathypelagic zooplankton, meaning that the community structure in these zones has a major impact on the efficiency of FP transfer to depth.
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Abstract. The faecal pellets (FP) of zooplankton can be important vehicles for the transfer of particulate organic carbon (POC) to the deep ocean, often making large contributions to carbon sequestration. However, the routes by which these FP reach the deep ocean have yet to be fully resolved. We address this by comparing estimates of FP production to measurements of FP size, shape and number in the upper mesopelagic (175–205 m), using Marine Snow Catchers, and in the bathypelagic, using sediment traps (1,500–2,000 m). The study is focussed on the Scotia Sea, which contains some of the most productive regions in the Southern Ocean, where epipelagic FP production is likely to be high. We found that, although the size distribution of zooplankton suggests that high numbers of small FP are produced in the epipelagic, small FP are rare in the deeper layers, implying that they are not transferred efficiently to depth. Consequently, small FP make only a minor contribution to FP fluxes in the meso- and bathypelagic, particularly in terms of carbon. The dominant FP in the upper mesopelagic were cylindrical and elliptical, while ovoid FP were dominant in the bathypelagic. The change in FP morphology, as well as size distribution, points to the repacking of surface FP in the mesopelagic and in situ production in the lower meso- and bathypelagic, augmented by inputs of FP via zooplankton vertical migrations. The flux of carbon to the deeper layers within the Southern Ocean is therefore strongly modulated by meso- and bathypelagic zooplankton, meaning that the community structure in these zones has a major impact on the efficiency of FP transfer to depth.
Mesopelagic zone
Bathyal zone
Marine snow
Sediment trap
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Mesopelagic zone
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Deepwater Horizon
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The pelagic environment can be divided into five gross regions. These are the intertidal and estuarine, the neritic and the oceanic epipelagic, mesopelagic and bathypelagic regions. Each of these regions has an endemic crustacean fauna but many species inhabit more than one region. The ranges and rates of fluctuations of environmental characteristics vary from the extremes encountered in the intertidal and estuarine region to the relative constancy of those in the bathypelagic region.
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Intertidal ecology
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Data are reported from 30 dives during winter and spring 1980–83 at sites in the Strait of Georgia and inlets running off it, and in inlets on the west coast of Vancouver Island. Observations were made from the surface to the bottom (maximum 733 m) but most attention was given to the midwater plankton community. The vertical distribution and abundance of hydromedusae, siphonophores, ctenophores, euphausiids, pelagic worms and molluscs were recorded systematically, along with data for one copepod species ( Neocalanus plumchrus ). The midwater environment was found to be stable in terms of species composition and depth ranges, which permitted the data for several years and many locations to be pooled. Four categories of plankton are recognized: (a) epipelagic (concentrated in the top 50 m); (b) mesopelagic (50–175 m); (c) bathypelagic (below 175 m); and (d) meso-bathypelagic (forms living in both meso- and bathypelagic zones). Species in this last category behave like mesopelagic forms at the upper end of their ranges, migrating to the surface at night. Deeper-lying members of the same species do not migrate. For six such species, the cut-off point between migratory and non-migratory components was found to lie at a mean depth of 175 m. This depth is therefore taken as the demarcation point between the meso- and bathypelagic zones. Taking account of published data on light penetration, it is estimated that, for the whole region, daytime light intensity at 175 m, and hence the effective limit for phototaxis of the species in question, lies in the range 10 −8 –10 −9 μW cm −2 .
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Bathyal zone
Diel vertical migration
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Bathyal zone
Mesopelagic zone
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The Earth’s most extensive living space is found in the bathypelagic zone of the oceans, yet research in these areas is scant. The micronekton of the bathypelagic zone in the eastern Gulf of Mexico (EGOM) was investigated with the goals of comparing its community structure and trophic interactions with those of the well-studied overlying mesopelagic micronekton. Significant changes in faunal structure were found, including shifts in dominant families as well as species. Compared to the mesopelagic zone, the bathypelagic community had increased abundance and biomass contributions from the Gonostomatidae, Oplophoridae, and Eucopiidae, with a simultaneous decrease in the importance of the Myctophidae and the Dendrobranchiata. The changed faunal structure within the crustacean assemblage includes a distinct difference in reproductive strategies. There is increased prevalence of taxa which feature egg brooding and abbreviated larval development. In addition, the bathypelagic zone was characterized by relatively large biomass contributions from rare but large species, particularly those within the families Oplophoridae and Nemichthyidae. The faunal shifts, in combination with a high percentage of bathypelagic species absent from mesopelagic samples (~50% of crustacean and ~37% of fish species), suggest the bathypelagic zone is home to a distinct pelagic community, with a biology and ecology fundamentally different from that of the mesopelagic zone. The broad zoogeographic distributions of bathypelagic species suggest the EGOM assemblage is possibly similar to that of other geographic locations at similar latitudes. Diet analysis was performed on several prominent species and revealed 2 major feeding strategies based on diet composition and prey size. Species of Cyclothone and Eucopia preyed
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Diel vertical migration
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Abstract We assess the biomass of deep-pelagic shrimps in the Atlantic Ocean using data collected between 40°N and 40°S. Forty-eight stations were sampled in discrete-depth fashion, including epi- (0–200 m), meso- (200–800/1000 m), upper bathy- (800/1000–1500 m), and lower bathypelagic (1500–3000 m) strata. We compared samples collected from the same area on the same night using obliquely towed trawls and large vertically towed nets and found that shrimp catches from the latter were significantly higher. This suggests that vertical nets are more efficient for biomass assessments, and we report these values here. We further compared day and night samples from the same site and found that biomass estimates differed only in the epi- and mesopelagic strata, while estimates from the bathypelagic strata and the total water column were independent of time of day. Maximal shrimp standing stocks occurred in the upper bathypelagic (52–54% of total biomass) and in the mesopelagic (42–43%). We assessed shrimp biomass in three major regions of the Atlantic between 40°N and 40°S, and the first-order extrapolation of these data suggests that the global low-latitude deep-pelagic shrimp biomass (1700 million tons) may lie within the range reported for mesopelagic fishes (estimations between 1000 and 15000 million tons). These data, along with previous fish-biomass estimates, call for the reassessment of the quantity and distribution of nektonic carbon in the deep ocean.
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Bathyal zone
Nekton
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