Large numbers of postlarvae of the bathyal ophiuroid Ophiocten gracilis were collected by two time-series sediment traps moored on the continental slope of the NE Atlantic for 102 d at 1,000 and ...1,400 m deep (469 and 69 mab), respectively. With time, the organisms collected were progressively larger, suggesting that a single cohort was growing within the collection funnel of the traps but above the preservative solution. We believe that specimens from this cohort occasionally lost their grip on the funnel surface and fell into the preservative. This conclusion is supported by (1) the presence of food within the stomachs of postlarvae (these do not feed in their planktonic phase) and (2) the size of specimens (much larger than those previously found in the plankton). The upper trap was well above the benthic nepheloid layer, and suspension of these organisms by ambient currents is highly unlikely. Ophiuroids contributed up to 7% of the total daily flux of particulate organic carbon (POC) in the top trap and almost 30% in the bottom trap, and although they are not normally considered components of downward particle flux, these specimens had been growing on the material entering the traps and so should be included in this portion. Not all of the epifaunal population will have fallen into the collecting cups, but those that fell had requirements for growth and respiration that were a considerable proportion of the daily flux of POC into the traps (up to 16%). If this epifaunal community (a minimum estimate) was distributed evenly within the cone, a high proportion of the settling material would have come into contact with ophiuroids as it slid down the inside walls of the cone. This problem with the sediment trap technique is probably restricted to the continental slope and shelf and will not occur over abyssal depths.
Understanding the influence of anthropogenic forcing on the marine biosphere is a high priority. Climate change‐driven trends need to be accurately assessed and detected in a timely manner. As part ...of the effort towards detection of long‐term trends, a network of ocean observatories and time series stations provide high quality data for a number of key parameters, such as pH, oxygen concentration or primary production (PP). Here, we use an ensemble of global coupled climate models to assess the temporal and spatial scales over which observations of eight biogeochemically relevant variables must be made to robustly detect a long‐term trend. We find that, as a global average, continuous time series are required for between 14 (pH) and 32 (PP) years to distinguish a climate change trend from natural variability. Regional differences are extensive, with low latitudes and the Arctic generally needing shorter time series (<~30 years) to detect trends than other areas. In addition, we quantify the ‘footprint’ of existing and planned time series stations, that is the area over which a station is representative of a broader region. Footprints are generally largest for pH and sea surface temperature, but nevertheless the existing network of observatories only represents 9–15% of the global ocean surface. Our results present a quantitative framework for assessing the adequacy of current and future ocean observing networks for detection and monitoring of climate change‐driven responses in the marine ecosystem.
Residual flow, barotropic tides and internal (baroclinic) tides interact in a number of ways with kilometer-scale seafloor topography such as abyssal hills and seamounts. Because of their likely ...impact on vertical mixing such interactions are potentially important for ocean circulation and the mechanisms and the geometry of these interactions are a matter of ongoing studies. In addition, very little is known about how these interactions are reflected in the sedimentary record. This multi-year study investigates if flow/topography interactions are reflected in distributional patterns of the natural short-lived (half-life: 24.1 d) particulate-matter tracer ... relative to its conservative (non-particle-reactive) and very long-lived parent nuclide ... The sampling sites were downstream of, or surrounded by, fields of short seamounts and, therefore, very likely to be influenced by nearby flow/topography interactions. At the sampling sites between about 200 and 1000 m above the seafloor recurrent 'fossil' disequilibria were detected. 'Fossil' disequilibria are defined by clearly detectable ... disequilibria (total ... radioactivity ... radioactivity, indicating a history of intense particulate ... scavenging and particulatematter settling from the sampled parcel of water) and conspicuously low particle-associated ... activities. 'Fossil' disequilibria were centered at levels in the water column that correspond to the average height of the short seamounts near the sampling sites. This suggests the 'fossil' disequilibria are formed on the seamount slopes. Moreover, the magnitude of the 'fossil' disequilibria suggests that the slopes of the short seamounts in the study region are characterized by particularly vigorous fluid dynamics. Since 'fossil' disequilibria already occurred at ~O(1 - 10 km) away from the seamount slopes it is likely that these vigorous fluid dynamics rapidly decay away from the slopes on scales of O (1 - 10 km). These conclusions are supported by the horizontal distribution and magnitude of the modeled total (barotropic+baroclinic) tidal current velocities of the predominating tidal M... constituent: on (near-)critical seamount slopes baroclinic tides lead to localized ~O(1 km) increases of the overall tidal current velocity by a factor of 2, thereby pushing the total current velocity well above the threshold for sediment erosion. The results of this and a previous study Turnewitsch, R., Reyss, J.-L., Chapman, D.C., Thomson, J., Lampitt, R.S., 2004. Evidence for a sedimentary fingerprint of an asymmetric flow field surrounding a short seamount. Earth and Planetary Science Letters 222(3 - 4), 1023 - 1036 show that kilometer-scale flow/topography interactions leave a marine geochemical imprint. This imprint may help develop new sediment proxies for the reconstruction of past changes of fluid dynamics in the deep sea, including residual and tidal flow. Sedimentary records controlled by kilometer-scale seafloor elevations are promising systems for the reconstruction of paleo-changes of deep-ocean fluid dynamics. For the sediment-based reconstruction of paleo-parameters other than physical oceanographic ones it may be advisable to avoid kilometer-scale topography altogether. (ProQuest: ... denotes formulae/symbols omitted.)
The contribution of carbonate-producing benthic organisms to the global marine carbon budget has been overlooked, the prevailing view being that calcium carbonate (CaCO₃) is predominantly produced ...and exported by marine plankton in the "biological pump." Here, we provide the first estimation of the global contribution of echinoderms to the marine inorganic and organic carbon cycle, based on organism-level measurements from species of the five echinoderm classes. Echinoderms' global CaCO₃ contribution amounts to ∼0.861 Pg CaCO₃/yr (0.102 Pg C/yr of inorganic carbon) as a production rate, and ∼2.11 Pg CaCO₃ (0.25 Pg C of inorganic carbon) as a standing stock from the shelves, slopes, and abyssal depths. Echinoderm inorganic carbon production (0.102 Pg C/yr) is less than the global pelagic production (0.4-1.8 Pg C/yr) and similar to the estimates for carbonate shelves globally (0.024-0.120 Pg C/yr). Echinoderm CaCO₃ production per unit area is ∼27.01 g CaCO₃·m⁻²·yr⁻¹ (3.24 g C·m⁻²·yr⁻¹ as inorganic carbon) on a global scale for all areas, with a standing stock of ∼63.34 g CaCO₃/m² (7.60 g C/m² as inorganic carbon), and ∼7.97 g C/m² as organic carbon. The shelf production alone is 77.91 g CaCO₃·m⁻²·yr⁻¹ (9.35 g C·m⁻²·yr⁻¹ as inorganic carbon) in contrast to 2.05 g CaCO₃·m⁻²·yr⁻¹ (0.24 g C·m⁻²·yr⁻¹ as inorganic carbon) for the slope on a global scale. The biogeography of the CaCO₃ standing stocks of echinoderms showed strong latitudinal variability. More than 80% of the global CaCO₃ production from echinoderms occurs between 0 and 800 m, with the highest contribution attributed to the shelf and upper slope. We provide a global distribution of echinoderm populations in the context of global calcite saturation horizons, since undersaturated waters with respect to mineral phases are surfacing. This shallowing is a direct consequence of ocean acidification, and in some places it may reach the shelf and upper slope permanently, where the highest CaCO₃ standing stocks from echinoderms originate. These organism-level data contribute substantially to the assessment of global carbonate inventories, which at present are poorly estimated. Additionally, it is desirable to include these benthic compartments in coupled global biogeochemical models representing the "biological pump" and its feedbacks, since at present all efforts have focused on pelagic processes, dominated by coccolithophores. The omission of the benthic processes from modeling will only diminish the understanding of elemental fluxes at large scales and any future prediction of climate change scenarios.
The contribution of carbonate-producing benthic organisms to the global marine carbon budget has been overlooked, the prevailing view being that calcium carbonate (...) is predominantly produced and ...exported by marine plankton in the "biological pump." Here, we provide the first estimation of the global contribution of echinoderms to the marine inorganic and organic carbon cycle, based on organism-level measurements from species of the five echinoderm classes. Echinoderms' global ... contribution amounts to ~0.861 Pg .../yr (0.102 Pg C/yr of inorganic carbon) as a production rate, and ~2.11 Pg ...(0.25 Pg C of inorganic carbon) as a standing stock from the shelves, slopes, and abyssal depths. Echinoderm inorganic carbon production (0.102 Pg C/yr) is less than the global pelagic production (0.4-1.8 Pg C/yr) and similar to the estimates for carbonate shelves globally (0.024-0.120 Pg C/yr). Echinoderm CaCO3 production per unit area is ~27.01 g ... (3.24 g ... as inorganic carbon) on a global scale for all areas, with a standing stock of ~63.34 g ... (7.60 g C/m... as inorganic carbon), and ~7.97 g C/m... as organic carbon. The shelf production alone is 77.91 g ... (9.35 g ... as inorganic carbon) in contrast to 2.05 g ... (0.24 g ... as inorganic carbon) for the slope on a global scale. The biogeography of the ... standing stocks of echinoderms showed strong latitudinal variability. More than 80% of the global ... production from echinoderms occurs between 0 and 800 m, with the highest contribution attributed to the shelf and upper slope. We provide a global distribution of echinoderm populations in the context of global calcite saturation horizons, since undersaturated waters with respect to mineral phases are surfacing. This shallowing is a direct consequence of ocean acidification, and in some places it may reach the shelf and upper slope permanently, where the highest ... standing stocks from echinoderms originate. These organism-level data contribute substantially to the assessment of global carbonate inventories, which at present are poorly estimated. Additionally, it is desirable to include these benthic compartments in coupled global biogeochemical models representing the "biological pump" and its feedbacks, since at present all efforts have focused on pelagic processes, dominated by coccolithophores. The omission of the benthic processes from modeling will only diminish the understanding of elemental fluxes at large scales and any future prediction of climate change scenarios. (ProQuest: ... denotes formulae/symbols omitted.)
Although cyclopoids of the genusOithonaare considered the most abundant copepods in the marine environment, there is still very little information about what sustains their population and almost ...constant reproduction rate throughout the year. Feeding and egg production rate (EPR) ofO. similiswere measured at coastal and oceanic stations during 3 cruises in the North Atlantic between April and November 2002.O. similisingested ciliates preferentially to other components of the nano- and microplankton (herein nano-microplankton), which only became a more important component of the copepod diet when the abundance of the former decreased to low concentrations. EPR did not show significant seasonal differences, with 2.13 ± 0.67 eggs female–1d–1in spring, 1.61 ± 0.32 eggs female–1d–1in summer and 1.60 ± 0.15 eggs female–1d–1in winter. The ingestion rates measured at many oceanic stations and in winter were often too low to sustain EPR. Egg production efficiency (GGE) >100% indicated that sustained EPR might have relied, particularly in winter, on alternative food sources such as a more carnivorous diet and/or on the faecal pellets of euphausids.
Oithonaspp. is considered the most abundant and ubiquitous copepod genus in the marine environment, often outnumbering calanoid copepods throughout the year. Previous studies have argued that one of ...the reasons for such success is that the respiration rate ofOithonaspp. is insensitive to temperature changes and lower than in calanoids. However, comprehensive data on the thermal biology of this important copepod genus is lacking. In this study, the respiration rate of adult femaleO. similisfrom the English Channel, was measured over the temperature range 4 to 25°C. The respiration rate ofO. similischanged exponentially with temperature (ln O₂-rate = –3.59 + 0.114T, df = 35, r² = 0.85, p < 0.001,Q
10= 3.1) similar to that of other poikilotherms. Over the temperature range examined,O. similisbasic metabolic cost varied from a minimum of ~1.4% body-C d–1at 4°C to a maximum of 23% body-C d–1at 25°C, corresponding to an energy demand of ~3% and 32% body-C d–1respectively. The respiration rate ofO. similis, from the present study, is ~8 times lower than that of a calanoid copepod of equivalent body weight estimated from published empirical metabolism–temperature data. We suggest that these differences in metabolic rates may account for the year-round persistence and higher abundances ofOithonaspp. over calanoid copepods, particularly in oceanic and oligotrophic environments where food resources may be limiting for calanoid copepods.
Metabolic activity in the water column below the euphotic zone is ultimately fuelled by the vertical flux of organic material from the surface. Over time, the deep ocean is presumably at steady ...state, with sources and sinks balanced. But recently compiled global budgets and intensive local field studies suggest that estimates of metabolic activity in the dark ocean exceed the influx of organic substrates. This imbalance indicates either the existence of unaccounted sources of organic carbon or that metabolic activity in the dark ocean is being over-estimated. Budgets of organic carbon flux and metabolic activity in the dark ocean have uncertainties associated with environmental variability, measurement capabilities, conversion parameters, and processes that are not well sampled. We present these issues and quantify associated uncertainties where possible, using a Monte Carlo analysis of a published data set to determine the probability that the imbalance can be explained purely by uncertainties in measurements and conversion factors. A sensitivity analysis demonstrates that the bacterial growth efficiencies and assumed cell carbon contents have the greatest effects on the magnitude of the carbon imbalance. Two poorly quantified sources, lateral advection of particles and a population of slowly settling particles, are discussed as providing a means of closing regional carbon budgets. Finally, we make recommendations concerning future research directions to reduce important uncertainties and allow a better determination of the magnitude and causes of the unbalanced carbon budgets.
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