The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Shaun P. Collin - One of the best experts on this subject based on the ideXlab platform.
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The Influence of Photoreceptor Size and Distribution on Optical Sensitivity in the Eyes of Lanternfishes (Myctophidae)
2016Co-Authors: Fanny De Busserolles, John L. Fitzpatrick, Justin N. Marshall, Shaun P. CollinAbstract:The Mesopelagic Zone of the deep-sea (200-1000 m) is characterised by exponentially diminishing levels of downwelling sunlight and by the predominance of bioluminescence emissions. The ability of Mesopelagic organisms to detect and behaviourally react to downwelling sunlight and/or bioluminescence will depend on the visual task and ultimately on the eyes and their capacity for detecting low levels of illumination and intermittent point sources of bioluminescent light. In this study, we investigate the diversity of the visual system of the lanternfish (Myctophidae). We focus specifically on the photoreceptor cells by examining their size, arrangement, topographic distribution and contribution to optical sensitivity in 53 different species from 18 genera. We also examine the influence(s) of both phylogeny and ecology on these photoreceptor variables using phylogenetic comparative analyses in order to understand the constraints placed on the visual systems of this large group of Mesopelagic fishes at the first stage of retinal processing. We report great diversity in the visual system of the Myctophidae at the level of the photoreceptors. Photoreceptor distribution reveals clear interspecific differences in visual specialisations (areas of high rod photoreceptor density), indicating potential interspecific differences in interactions with prey, predators and/or mates. A great diversity in photoreceptor design (length and diameter) and density is also present. Overall, the myctophid eye is very sensitive compared to other teleosts and each species seems to be specialised for the detection of a specific signal (downwelling light or bioluminescence), potentiall
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Eye-Size Variability in Deep-Sea Lanternfishes (Myctophidae): An Ecological and Phylogenetic
2016Co-Authors: Fanny De Busserolles, John L. Fitzpatrick, Justin N. Marshall, John R. Paxton, Shaun P. CollinAbstract:One of the most common visual adaptations seen in the Mesopelagic Zone (200–1000 m), where the amount of light diminishes exponentially with depth and where bioluminescent organisms predominate, is the enlargement of the eye and pupil area. However, it remains unclear how eye size is influenced by depth, other environmental conditions and phylogeny. In this study, we determine the factors influencing variability in eye size and assess whether this variability is explained by ecological differences in habitat and lifestyle within a family of Mesopelagic fishes characterized by broad intra- and interspecific variance in depth range and luminous patterns. We focus our study on the lanternfish family (Myctophidae) and hypothesise that lanternfishes with a deeper distribution and/or a reduction of bioluminescent emissions have smaller eyes and that ecological factors rather than phylogenetic relationships will drive the evolution of the visual system. Eye diameter and standard length were measured in 237 individuals from 61 species of lanternfishes representing all the recognised tribes within the family in addition to compiling an ecological dataset including depth distribution during night and day and the location and sexual dimorphism of luminous organs. Hypotheses were tested by investigating the relationship between the relative size of the eye (corrected for body size) and variations in depth and/or patterns of luminous-organs using phylogenetic comparative analyses. Results show a great variability in relative eye size within the Myctophidae at all taxonomic levels (from subfamily to genus), suggesting that this character may have evolved severa
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photon hunting in the twilight Zone visual features of Mesopelagic bioluminescent sharks
PLOS ONE, 2014Co-Authors: Julien M Claes, J C Partridge, Nathan S Hart, Eduardo Garzagisholt, Jerome Mallefet, Shaun P. CollinAbstract:The Mesopelagic Zone is a visual scene continuum in which organisms have developed various strategies to optimize photon capture. Here, we used light microscopy, stereology-assisted retinal topographic mapping, spectrophotometry and microspectrophotometry to investigate the visual ecology of deep-sea bioluminescent sharks [four etmopterid species (Etmopterus lucifer, E. splendidus, E. spinax and Trigonognathus kabeyai) and one dalatiid species (Squaliolus aliae)]. We highlighted a novel structure, a translucent area present in the upper eye orbit of Etmopteridae, which might be part of a reference system for counterillumination adjustment or acts as a spectral filter for camouflage breaking, as well as several ocular specialisations such as aphakic gaps and semicircular tapeta previously unknown in elasmobranchs. All species showed pure rod hexagonal mosaics with a high topographic diversity. Retinal specialisations, formed by shallow cell density gradients, may aid in prey detection and reflect lifestyle differences; pelagic species display areae centrales while benthopelagic and benthic species display wide and narrow horizontal streaks, respectively. One species (E. lucifer) displays two areae within its horizontal streak that likely allows detection of conspecifics' elongated bioluminescent flank markings. Ganglion cell topography reveals less variation with all species showing a temporal area for acute frontal binocular vision. This area is dorsally extended in T. kabeyai, allowing this species to adjust the strike of its peculiar jaws in the ventro-frontal visual field. Etmopterus lucifer showed an additional nasal area matching a high rod density area. Peak spectral sensitivities of the rod visual pigments (λmax) fall within the range 484–491 nm, allowing these sharks to detect a high proportion of photons present in their habitat. Comparisons with previously published data reveal ocular differences between bioluminescent and non-bioluminescent deep-sea sharks. In particular, bioluminescent sharks possess higher rod densities, which might provide them with improved temporal resolution particularly useful for bioluminescent communication during social interactions.
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Eye-Size Variability in Deep-Sea Lanternfishes (Myctophidae): An Ecological and Phylogenetic Study
2013Co-Authors: Fanny De Busserolles, John L. Fitzpatrick, Justin N. Marshall, John R. Paxton, Shaun P. CollinAbstract:One of the most common visual adaptations seen in the Mesopelagic Zone (200–1000 m), where the amount of light diminishes exponentially with depth and where bioluminescent organisms predominate, is the enlargement of the eye and pupil area. However, it remains unclear how eye size is influenced by depth, other environmental conditions and phylogeny. In this study, we determine the factors influencing variability in eye size and assess whether this variability is explained by ecological differences in habitat and lifestyle within a family of Mesopelagic fishes characterized by broad intra- and interspecific variance in depth range and luminous patterns. We focus our study on the lanternfish family (Myctophidae) and hypothesise that lanternfishes with a deeper distribution and/or a reduction of bioluminescent emissions have smaller eyes and that ecological factors rather than phylogenetic relationships will drive the evolution of the visual system. Eye diameter and standard length were measured in 237 individuals from 61 species of lanternfishes representing all the recognised tribes within the family in addition to compiling an ecological dataset including depth distribution during night and day and the location and sexual dimorphism of luminous organs. Hypotheses were tested by investigating the relationship between the relative size of the eye (corrected for body size) and variations in depth and/or patterns of luminous-organs using phylogenetic comparative analyses. Results show a great variability in relative eye size within the Myctophidae at all taxonomic levels (from subfamily to genus), suggesting that this character may have evolved several times. However, variability in eye size within the family could not be explained by any of our ecological variables (bioluminescence and depth patterns), and appears to be driven solely by phylogenetic relationships.
Deborah K Steinberg - One of the best experts on this subject based on the ideXlab platform.
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zooplankton diel vertical migration during antarctic summer
Deep Sea Research Part I: Oceanographic Research Papers, 2020Co-Authors: John A Conroy, Deborah K Steinberg, Patricia S Thibodeau, Oscar SchofieldAbstract:Abstract Zooplankton diel vertical migration (DVM) during summer in the polar oceans is presumed to be dampened due to near continuous daylight. We analyzed zooplankton diel vertical distribution patterns in a wide range of taxa along the Western Antarctic Peninsula (WAP) to assess if DVM occurs, and if so, what environmental controls modulate DVM in the austral summer. Zooplankton were collected during January and February in paired day-night, depth-stratified tows through the Mesopelagic Zone along the WAP from 2009-2017, as well as in day and night epipelagic net tows from 1993-2017. The copepod Metridia gerlachei, salp Salpa thompsoni, pteropod Limacina helicina antarctica, and ostracods consistently conducted DVM between the Mesopelagic and epipelagic Zones. Migration distance for M. gerlachei and ostracods decreased as photoperiod increased from 17 to 22 h daylight. The copepods Calanoides acutus and Rhincalanus gigas, as well as euphausiids Thysanoessa macrura and Euphausia crystallorophias, conducted shallow (mostly within the epipelagic Zone) DVMs into the upper 50 m at night. Rhincalanus gigas, T. macrura, and L. h. antarctica DVM behavior was modulated by chlorophyll a concentration, mixed layer depth, and depth of the subsurface chlorophyll a maximum, respectively. Carnivorous and detritivorous taxa – including the calanoid copepod Paraeuchaeta antarctica, ostracods, chaetognaths, and Tomopteris spp. polychaetes – as well as seasonally migrating copepods, were most abundant in the Mesopelagic Zone regardless of the diel cycle. Paraeuchaeta antarctica underwent reverse DVM within the top 100 m. The impacts of Antarctic zooplankton summer DVM and the substantial Mesopelagic assemblage on carbon export should be better quantified.
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autotrophic picoplankton in mesozooplankton guts evidence of aggregate feeding in the Mesopelagic Zone and export of small phytoplankton
Marine Ecology Progress Series, 2010Co-Authors: Stephanie E Wilson, Deborah K SteinbergAbstract:Zooplankton play a key role in affecting the efficiency by which organic matter is exported to depth. Mesozooplankton consumption of detrital aggregates has been hypothesized as a mechanism for enhancing the export of picoplankton from surface layers. We analyzed the gut con- tents of Mesopelagic copepods and ostracods using light and epifluorescence microscopy to deter- mine if cyanobacteria and eukaryotic phytoplankton too small to be ingested individually were pre- sent. Hind-guts were dissected from multiple species collected in discrete depth intervals between 0 and 1000 m during the day and night, at contrasting sites in the subtropical (Hawaii Ocean Time- series site ALOHA) and subarctic (Japanese time-series site K2) Pacific Ocean. Autofluorescing cyanobacteria and small eukaryotic phytoplankton were found in the guts of nearly all species sam- pled from all depths, indicating consumption of aggregates. Some of the cyanobacteria and other small cells ingested may have originated from inside the guts, or as symbionts, of microzooplankton, which were also common in the guts of many of these species. At both sites, most species' guts con- tained higher concentrations of cyanobacteria and small phytoplankton at night than during the day. Ostracod guts at ALOHA contained higher densities of picoplankton than those at K2, reflecting the predominance of smaller cells at ALOHA. Guts of diel vertical migrators still contained picoplankton at their deep, daytime residence depths, indicating active export of these cells. Our results indicate mesozooplankton grazing on aggregates is a pathway by which flux of picoplankton can be enhanced.
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Mesopelagic Zone ecology and biogeochemistry a synthesis
Deep-sea Research Part Ii-topical Studies in Oceanography, 2010Co-Authors: Carol Robinson, Deborah K Steinberg, Thomas R Anderson, Javier Aristegui, Craig A Carlson, Jessica R Frost, Jeanfrancois Ghiglione, Santiago Hernandezleon, George A Jackson, Rolf KoppelmannAbstract:The Mesopelagic Zone is the oceanic region through which carbon and other elements must pass in order to reach deeper waters or the sea floor. However, the food web interactions that occur in the Mesopelagic Zone are difficult to measure and so, despite their crucial importance to global elemental cycles, are not very well known. Recent developments in technology and new approaches have advanced the study of the variability in and controls upon the distribution and diversity of organisms in the Mesopelagic Zone, including the roles of respiration, recycling, and repackaging of particulate and dissolved organic material. However, there are remarkably few syntheses of the ecology and biogeochemistry of the microbes and metazoa that permanently reside or habitually visit this ‘twilight Zone’. Without this synthesis, it is difficult to assess the impact of ongoing changes in ocean hydrography and chemistry, due to increasing atmospheric carbon dioxide levels, on the biological carbon pump. This paper reviews what is known about the distribution of microbes and metazoa in the Mesopelagic Zone in relation to their activity and impact on global biogeochemical cycles. Thus, gaps in our knowledge are identified and suggestions made for priority research programmes that will improve our ability to predict the effects of climate change on carbon sequestration.
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changes in fecal pellet characteristics with depth as indicators of zooplankton repackaging of particles in the Mesopelagic Zone of the subtropical and subarctic north pacific ocean
Deep-sea Research Part Ii-topical Studies in Oceanography, 2008Co-Authors: Stephanie E Wilson, Deborah K Steinberg, Ken O BuesselerAbstract:We investigated how fecal pellet characteristics change with depth in order to quantify the extent of particle repackaging by Mesopelagic zooplankton in two contrasting open-ocean systems. Material from neutrally buoyant sediment traps deployed in the summer of 2004 and 2005 at 150, 300, and 500 m was analyzed from both a mesotrophic (Japanese time-series station K2) and an oligotrophic (Hawaii Ocean Time series—HOT station ALOHA) environment in the Pacific Ocean as part of the VERtical Transport In the Global Ocean (VERTIGO) project. We quantified changes in the flux, size, shape, and color of particles recognizable as zooplankton fecal pellets to determine how these parameters varied with depth and location. Flux of K2 fecal pellet particulate organic carbon (POC) at 150 and 300 m was four to five times higher than at ALOHA, and at all depths, fecal pellets were two to five times larger at K2, reflective of the disparate zooplankton community structure at the two sites. At K2, the proportion of POC flux that consisted of fecal pellets generally decreased with depth from 20% at 150 m to 5% at 500 m, whereas at ALOHA this proportion increased with depth (and was more variable) from 14% to 35%. This difference in the fecal fraction of POC with increasing depth is hypothesized to be due to differences in the extent of zooplankton-mediated fragmentation (coprohexy) and in zooplankton community structure between the two locations. Both regions provided indications of sinking particle repackaging and zooplankton carnivory in the Mesopelagic. At ALOHA, this was reflected in a significant increase in the mean flux of larvacean fecal pellets from 150 to 500 m of 3–46m gCm � 2 d � 1 , respectively, and at K2 a large peak in
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the flux of bio and lithogenic material associated with sinking particles in the Mesopelagic twilight Zone of the northwest and north central pacific ocean
Deep-sea Research Part Ii-topical Studies in Oceanography, 2008Co-Authors: Carl H. Lamborg, Deborah K Steinberg, Ken O Buesseler, Steven J. Manganini, James R Valdes, C H Bertrand, Robert R Bidigare, Steven M Pike, Thomas W Trull, Stephanie E WilsonAbstract:Abstract As part of the VERTIGO program, we collected and analyzed sinking particles using tethered and neutrally buoyant sediment traps at three depths in the oceanic Mesopelagic Zone and at two biogeochemically contrasting sites (N. Central Pacific at ALOHA; N. Pacific Western Subarctic Gyre at K2). This effort represented the first large-scale use of neutrally buoyant traps and represents a significant step forward in the study of the marine biological pump. In this paper, we present the results of mass, macronutrient, biominerals and phytoplankton pigment determinations made on these samples. The impact of a variety of potential collection biases were examined, including those from in-trap particle degradation, zooplankton swimmers and poisons. Though these factors have been observed to affect results in other programs, we found them to have relatively little impact on measured fluxes in this study. There was evidence, however, that the neutrally buoyant traps performed better than the tethered traps in terms of flux accuracy during one deployment, possibly because of improved large particle collection efficiency. Fluxes of material exhibited three different patterns through the Mesopelagic: increasing, decreasing and constant with depth. Decreasing fluxes with depth were observed for all biogenic material formed in the euphotic Zone. The attenuation of flux with depth was not the same for all components, however, with phytoplankton pigments exhibiting the greatest degradation with depth and particulate inorganic carbon the least. Organic carbon and nitrogen showed a very high correlation in these samples, with little evidence of different attenuation length scales. Increasing fluxes with depth were observed for particulate Ba at both sites and Al at K2. The increases in Ba are attributed to the formation of barite in degrading particles, while increasing Al at K2 was the result of lateral inputs from a continental shelf/slope. Constant fluxes with depth were observed for Al at ALOHA, where fluxes appeared to be in steady state with atmospheric dust deposition. The Mesopelagic Zone at K2 was observed to attenuate particle flux less than at ALOHA, and with a higher POC/PIC (“rain”) ratio. These two factors combine to imply that the Subarctic province had a much more efficient biological pump than had the subtropical gyre during our occupations. This could be the result of either faster sinking particles, generated from grazing by large zooplankton, or inherently slower particle degradation rates.
Ken O Buesseler - One of the best experts on this subject based on the ideXlab platform.
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effects of sinking velocities and microbial respiration rates on the attenuation of particulate carbon fluxes through the Mesopelagic Zone
Global Biogeochemical Cycles, 2015Co-Authors: Andrew M P Mcdonnell, Philip W Boyd, Ken O BuesselerAbstract:The attenuation of sinking particle fluxes through the Mesopelagic Zone is an important process that controls the sequestration of carbon and the distribution of other elements throughout the oceans. Case studies at two contrasting sites, the oligotrophic regime of the Bermuda Atlantic Time-series Study (BATS) and the mesotrophic waters of the west Antarctic Peninsula (WAP) sector of the Southern Ocean, revealed large differences in the rates of particle-attached microbial respiration and the average sinking velocities of marine particles, two parameters that affect the transfer efficiency of particulate matter from the base of the euphotic Zone into the deep ocean. Rapid average sinking velocities of 270 ± 150 m d−1 were observed along the WAP, whereas the average velocity was 49 ± 25 m d−1 at the BATS site. Respiration rates of particle-attached microbes were measured using novel RESPIRE (REspiration of Sinking Particles In the subsuRface ocEan) sediment traps that first intercepts sinking particles then incubates them in situ. RESPIRE experiments yielded flux-normalized respiration rates of 0.4 ± 0.1 day−1 at BATS when excluding an outlier of 1.52 day−1, while these rates were undetectable along the WAP (0.01 ± 0.02 day−1). At BATS, flux-normalized respiration rates decreased exponentially with respect to depth below the euphotic Zone with a 75% reduction between the 150 and 500 m depths. These findings provide quantitative and mechanistic insights into the processes that control the transfer efficiency of particle flux through the Mesopelagic and its variability throughout the global oceans.
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changes in fecal pellet characteristics with depth as indicators of zooplankton repackaging of particles in the Mesopelagic Zone of the subtropical and subarctic north pacific ocean
Deep-sea Research Part Ii-topical Studies in Oceanography, 2008Co-Authors: Stephanie E Wilson, Deborah K Steinberg, Ken O BuesselerAbstract:We investigated how fecal pellet characteristics change with depth in order to quantify the extent of particle repackaging by Mesopelagic zooplankton in two contrasting open-ocean systems. Material from neutrally buoyant sediment traps deployed in the summer of 2004 and 2005 at 150, 300, and 500 m was analyzed from both a mesotrophic (Japanese time-series station K2) and an oligotrophic (Hawaii Ocean Time series—HOT station ALOHA) environment in the Pacific Ocean as part of the VERtical Transport In the Global Ocean (VERTIGO) project. We quantified changes in the flux, size, shape, and color of particles recognizable as zooplankton fecal pellets to determine how these parameters varied with depth and location. Flux of K2 fecal pellet particulate organic carbon (POC) at 150 and 300 m was four to five times higher than at ALOHA, and at all depths, fecal pellets were two to five times larger at K2, reflective of the disparate zooplankton community structure at the two sites. At K2, the proportion of POC flux that consisted of fecal pellets generally decreased with depth from 20% at 150 m to 5% at 500 m, whereas at ALOHA this proportion increased with depth (and was more variable) from 14% to 35%. This difference in the fecal fraction of POC with increasing depth is hypothesized to be due to differences in the extent of zooplankton-mediated fragmentation (coprohexy) and in zooplankton community structure between the two locations. Both regions provided indications of sinking particle repackaging and zooplankton carnivory in the Mesopelagic. At ALOHA, this was reflected in a significant increase in the mean flux of larvacean fecal pellets from 150 to 500 m of 3–46m gCm � 2 d � 1 , respectively, and at K2 a large peak in
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the flux of bio and lithogenic material associated with sinking particles in the Mesopelagic twilight Zone of the northwest and north central pacific ocean
Deep-sea Research Part Ii-topical Studies in Oceanography, 2008Co-Authors: Carl H. Lamborg, Deborah K Steinberg, Ken O Buesseler, Steven J. Manganini, James R Valdes, C H Bertrand, Robert R Bidigare, Steven M Pike, Thomas W Trull, Stephanie E WilsonAbstract:Abstract As part of the VERTIGO program, we collected and analyzed sinking particles using tethered and neutrally buoyant sediment traps at three depths in the oceanic Mesopelagic Zone and at two biogeochemically contrasting sites (N. Central Pacific at ALOHA; N. Pacific Western Subarctic Gyre at K2). This effort represented the first large-scale use of neutrally buoyant traps and represents a significant step forward in the study of the marine biological pump. In this paper, we present the results of mass, macronutrient, biominerals and phytoplankton pigment determinations made on these samples. The impact of a variety of potential collection biases were examined, including those from in-trap particle degradation, zooplankton swimmers and poisons. Though these factors have been observed to affect results in other programs, we found them to have relatively little impact on measured fluxes in this study. There was evidence, however, that the neutrally buoyant traps performed better than the tethered traps in terms of flux accuracy during one deployment, possibly because of improved large particle collection efficiency. Fluxes of material exhibited three different patterns through the Mesopelagic: increasing, decreasing and constant with depth. Decreasing fluxes with depth were observed for all biogenic material formed in the euphotic Zone. The attenuation of flux with depth was not the same for all components, however, with phytoplankton pigments exhibiting the greatest degradation with depth and particulate inorganic carbon the least. Organic carbon and nitrogen showed a very high correlation in these samples, with little evidence of different attenuation length scales. Increasing fluxes with depth were observed for particulate Ba at both sites and Al at K2. The increases in Ba are attributed to the formation of barite in degrading particles, while increasing Al at K2 was the result of lateral inputs from a continental shelf/slope. Constant fluxes with depth were observed for Al at ALOHA, where fluxes appeared to be in steady state with atmospheric dust deposition. The Mesopelagic Zone at K2 was observed to attenuate particle flux less than at ALOHA, and with a higher POC/PIC (“rain”) ratio. These two factors combine to imply that the Subarctic province had a much more efficient biological pump than had the subtropical gyre during our occupations. This could be the result of either faster sinking particles, generated from grazing by large zooplankton, or inherently slower particle degradation rates.
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sinking fluxes of minor and trace elements in the north pacific ocean measured during the vertigo program
Deep-sea Research Part Ii-topical Studies in Oceanography, 2008Co-Authors: Carl H. Lamborg, Ken O Buesseler, Phoebe J LamAbstract:As part of the Vertical Transport in the Global Ocean (VERTIGO) program, we collected and analyzed sinking particles using sediment traps at three depths in the oceanic Mesopelagic Zone and at two biogeochemically contrasting sites (N. Central Pacific at ALOHA; N. Pacific Western Subarctic Gyre at K2). In this paper, we present the results of minor and trace element determinations made on these samples. Minor and trace elements in the sinking material showed 2 trends in flux with depth: increasing and constant. The sinking particulate phase of some elements (Al, Fe, Mn) was dominated by material of lithogenic origin and exhibited flux that was constant with depth and consistent with eolian dust inputs (ALOHA), or increasing in flux with depth as a result of lateral inputs from a shelf (K2). This shelf-derived material also appears to have been confined to very small particles, whose inherent sinking rates are slow, and residence time within the Mesopelagic ‘‘twilight Zone’’ would be consequently long. Furthermore, the flux of this material did not change with substantial changes in the rain of biogenic material from the surface (K2), suggesting mechanistic decoupling from the flux of organic carbon and macronutrients. Micronutrient (Fe, Co, Zn and Cu) fluxes examined in a 1-D mass balance suggest widely differing sources and sinks in the water column as well as impacts from biological uptake and regeneration. For example, total Fe fluxes into and out of the euphotic Zone appeared to be dominated by lithogenic material and far exceed biological requirements. The export flux of Fe, however, appeared to be balanced by the eolian input of soluble Fe. For Zn and Cu, the situation is reversed, with atmospheric inputs insufficient to support fluxes, and the cycling therefore dominated by the draw down of an internal pool. For Co, the situation lies in between, with important, but ultimately insufficient atmospheric inputs.
Craig A Carlson - One of the best experts on this subject based on the ideXlab platform.
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Mesopelagic Zone ecology and biogeochemistry a synthesis
Deep-sea Research Part Ii-topical Studies in Oceanography, 2010Co-Authors: Carol Robinson, Deborah K Steinberg, Thomas R Anderson, Javier Aristegui, Craig A Carlson, Jessica R Frost, Jeanfrancois Ghiglione, Santiago Hernandezleon, George A Jackson, Rolf KoppelmannAbstract:The Mesopelagic Zone is the oceanic region through which carbon and other elements must pass in order to reach deeper waters or the sea floor. However, the food web interactions that occur in the Mesopelagic Zone are difficult to measure and so, despite their crucial importance to global elemental cycles, are not very well known. Recent developments in technology and new approaches have advanced the study of the variability in and controls upon the distribution and diversity of organisms in the Mesopelagic Zone, including the roles of respiration, recycling, and repackaging of particulate and dissolved organic material. However, there are remarkably few syntheses of the ecology and biogeochemistry of the microbes and metazoa that permanently reside or habitually visit this ‘twilight Zone’. Without this synthesis, it is difficult to assess the impact of ongoing changes in ocean hydrography and chemistry, due to increasing atmospheric carbon dioxide levels, on the biological carbon pump. This paper reviews what is known about the distribution of microbes and metazoa in the Mesopelagic Zone in relation to their activity and impact on global biogeochemical cycles. Thus, gaps in our knowledge are identified and suggestions made for priority research programmes that will improve our ability to predict the effects of climate change on carbon sequestration.
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meridional variability in dissolved organic matter stocks and diagenetic state within the euphotic and Mesopelagic Zone of the north atlantic subtropical gyre
Marine Chemistry, 2010Co-Authors: Craig A Carlson, Stuart J Goldberg, Brandon Bock, N B Nelson, David A SiegelAbstract:article i nfo Article history: Dissolved combined neutral sugars (DCNS) Total hydrolyzable carbohydrates (TCHO) Dissolved organic matter (DOM) Diagenetic state North Atlantic Ocean Concentrations of dissolved organic carbon (DOC), bulk carbohydrates (TCHO), and dissolved combined neutral sugars (DCNS) were measured during a meridional U.S. CO2 — Climate Variability (CLIVAR) Repeat Hydrography Project cruise (A20) from 7-43°N in the North Atlantic. Maxima in DOC, TCHO, and DCNS concentrations and carbohydrate yields (TCHO and DCNS as a % of DOC) were observed within the most stratified surface waters south of 27°N. Concentrations and yields of TCHO and DCNS decreased to the north and south of their respective maxima, indicating significant variability in the apparent diagenetic state of dissolved organic matter (DOM) along the transect. Changes in apparent diagenetic state to the north appeared to be largely related to the previous entrainment of recalcitrant DOM during deep winter/spring convective mixing. Deep mixing was less of a factor in the more stratified waters to the south where the decrease in carbohydrate yields indicated diagenetic alteration of the surface-accumulated pool of DOM. Overall, diagenesis decreased both carbohydrate yields and the mol% of galactose and mannose+xylose content and in deep waters resulted in a significant enrichment in the mol% of glucose. TCHO yields and the mol% of glucose revealed significant differences in DOM quality between subtropical mode water (STMW) and upper Antarctic Intermediate Water (uAAIW) that were related to the extent of water mass ventilation.
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interactions among dissolved organic carbon microbial processes and community structure in the Mesopelagic Zone of the northwestern sargasso sea
Limnology and Oceanography, 2004Co-Authors: Craig A Carlson, Stephen J Giovannoni, Dennis A Hansell, Stuart J Goldberg, Rachel Parsons, Kevin L VerginAbstract:At the Bermuda Atlantic Time-Series Study (BATS) site, the field observations of dissolved organic carbon (DOC) dynamics indicate that seasonally produced "semilabile" DOC is resistant to rapid microbial degradation in the surface waters but available for microbial remineralization once it is delivered into the Mesopelagic Zone after convective overtum. In this study, we employed an experimental simulation of convective overtum events to determine whether the remineralization of semilabile DOC would occur in a controlled laboratory setting. Seawater culture experiments were conducted in which surface ('10 m) and Mesopelagic (250 m) 0.2-pLm filtrates were inoculated with unfiltered water from 10 and 250 m in an assortment of combinations to simulate various mixtures of nutrients, DOC quantity and quality, and microbial assemblages. Results indicate that (I) microbial inocula from the upper euphotic Zone were incapable of remineralizing the seasonally accumulated semilabile DOC (j.mol C L-' resolution) on the timescales of the incubations; (2) the utilization of semilabile DOC was greatest when the inoculum source was from 250 m and the filtrate source was from the upper 10 m; and (3) the decrease in bacterioplankton diversity, estimated with the Shannon-Wiener diversity index, was greater in treatments in which inoculum from 250 m was mixed with filtrate from 10 m than in treatments in which the surface inoculum was mixed with the surface filtrate. Our findings are that a portion of the surface semilabile DOC can be metabolized by microorganisms in a laboratory setting and that Mesopelagic nutrients alone are insufficient to stimulate DOC drawdown > 1.3 p.mol L-'. Transformations of microbial community structure were associated with the drawdown of surface DOC in simulated mixing events and suggest that microbial community structure is a factor in surface-layer DOC dynamics.
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sar11 clade dominates ocean surface bacterioplankton communities
Nature, 2002Co-Authors: Robert M. Morris, Craig A Carlson, Kevin L Vergin, Michael S. Rappé, Stephanie A. Connon, William A Siebold, Stephen J GiovannoniAbstract:The most abundant class of bacterial ribosomal RNA genes detected in seawater DNA by gene cloning belongs to SAR11-an alpha-proteobacterial clade. Other than indications of their prevalence in seawater, little is known about these organisms. Here we report quantitative measurements of the cellular abundance of the SAR11 clade in northwestern Sargasso Sea waters to 3,000 m and in Oregon coastal surface waters. On average, the SAR11 clade accounts for a third of the cells present in surface waters and nearly a fifth of the cells present in the Mesopelagic Zone. In some regions, members of the SAR11 clade represent as much as 50% of the total surface microbial community and 25% of the subeuphotic microbial community. By extrapolation, we estimate that globally there are 2.4 x 10(28) SAR11 cells in the oceans, half of which are located in the euphotic Zone. Although the biogeochemical role of the SAR11 clade remains uncertain, these data support the conclusion that this microbial group is among the most successful organisms on Earth.
Bin Wang - One of the best experts on this subject based on the ideXlab platform.
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changes of carbon to nitrogen ratio in particulate organic matter in the marine Mesopelagic Zone a case from the south china sea
Marine Chemistry, 2021Co-Authors: Bin Wang, Yiming Luo, Jingjing Zhang, Haiyan Jin, Jianfang ChenAbstract:Abstract In this study, a model of remineralization patterns was developed to explore the particulate organic matters (POM) decomposition process among marine Mesopelagic Zone (200 to 1000 m) using data from the South China Sea. The results suggest that three high C/N remineralization patterns are identified at 200 to 400 m, 600 to 700 m and 900 to 1000 m, and two low C/N remineralization patterns are found at 400 to 600 m and 700 to 900 m. These findings indicate three increasing trends and two decreasing trends of C/N ratios in POM, which are further confirmed by measured C/N data in POM from the global ocean. Only the exposed POM has the chance to experience the selective remineralization process, thus the C/N ratios in POM of the remained particles are closely related to selective preservation of specific bio-macromolecules, aggregates, zooplankton community structure at different depths and the microbial loop.