scholarly journals The transformation of mesopelagic structure across polar fronts

2021 ◽  
Author(s):  
Julek Chawarski ◽  
Thor Klevjer ◽  
David Coté ◽  
Geoffroy Maxime
Keyword(s):  
Carbon Flux ◽  
The Arctic ◽  
Acoustic Backscatter ◽  
Mesopelagic Fish ◽  
Carbon Export ◽  
Low Latitude ◽  
Large Component ◽  
Measuring Surface ◽  
Oceanic Carbon ◽  
Carbon Transport

Abstract The oceans sequester 31% of atmospheric carbon annually 1, but the magnitude of biologically enhanced sequestration is not evenly distributed across the globe 2. Measuring surface primary productivity offers a reasonable proxy for estimating carbon flux into the ocean 3 but entirely misses the processes that affect carbon export to sequestration depths. A high proportion of carbon flux is broken up 4 or respired 5 by organisms at mesopelagic depths (200-1000 m). At low and mid-latitudes, daytime biomass peaks of mesopelagic organisms are clearly present and detectable as sound-scattering layers, and up to 40% of oceanic carbon passes through these layers 6,7. Here we demonstrate that acoustic backscatter, a proxy for abundance of mesopelagic fish and zooplankton decreases by up to 97% across polar fronts, revealing a distinct pelagic structure in high latitude systems. As mesopelagic fish and macrozooplankton comprise a large component of active carbon transport in the upper ocean, this latitudinal reduction in mesopelagic biomass across thermal fronts, in both the Arctic and Antarctic, suggests different carbon flux attenuation schemes exists in ocean twilight zones of polar ecosystem compared to low latitude systems. Rapid ocean warming projected at mesopelagic depths8 will likely disrupt vertical connectivity and alter biogeochemical cycles at high latitudes.

scholarly journals Metazoans, migrations, and the ocean's biological carbon pump

2021 ◽  
Author(s):  
Jérôme Pinti ◽  
Timothy DeVries ◽  
Tommy Norin ◽  
Camila Serra-Pompei ◽  
Roland Proud ◽  
...  
Keyword(s):  
Vertical Migration ◽  
Diel Vertical Migration ◽  
Euphotic Zone ◽  
Mesopelagic Fish ◽  
Carbon Export ◽  
Carbon Pump ◽  
Oceanic Carbon ◽  
Unregulated Fishing ◽  
Global Carbon ◽  
Biological Carbon Pump

Diel vertical migration of fish and other metazoans actively transports organic carbon from the ocean surface to depth, contributing to the biological carbon pump. Here, we use a global vertical migration model to estimate global carbon fluxes and sequestration by fish and metazoans due to respiration, fecal pellets, and deadfalls. We estimate that fish and metazoans contribute 5.2 PgC/yr (2.1-8.8PgC/yr) to passive export out of the euphotic zone. Together with active transport, we estimate that fish are responsible for 20% (9-29%) of global carbon export, and 32% (18-43%) of oceanic carbon sequestration, with forage and deep-dwelling mesopelagic fish contributing the most. This essential ecosystem service could be at risk from unregulated fishing on the high seas.

scholarly journals From siphonophores to deep scattering layers: uncertainty ranges for the estimation of global mesopelagic fish biomass

2018 ◽  
Vol 76 (3) ◽  
pp. 718-733 ◽  
Author(s):  
Roland Proud ◽  
Nils Olav Handegard ◽  
Rudy J Kloser ◽  
Martin J Cox ◽  
Andrew S Brierley
Keyword(s):  
Sensitivity Analysis ◽  
Aspect Ratio ◽  
Food Source ◽  
Acoustic Backscatter ◽  
Mesopelagic Fish ◽  
Fish Biomass ◽  
Future Studies ◽  
Oceanic Carbon ◽  
Potential Food

Abstract The mesopelagic community is important for downward oceanic carbon transportation and is a potential food source for humans. Estimates of global mesopelagic fish biomass vary substantially (between 1 and 20 Gt). Here, we develop a global mesopelagic fish biomass model using daytime 38 kHz acoustic backscatter from deep scattering layers. Model backscatter arises predominantly from fish and siphonophores but the relative proportions of siphonophores and fish, and several of the parameters in the model, are uncertain. We use simulations to estimate biomass and the variance of biomass determined across three different scenarios; S1, where all fish have gas-filled swimbladders, and S2 and S3, where a proportion of fish do not. Our estimates of biomass ranged from 1.8 to 16 Gt (25–75% quartile ranges), and median values of S1 to S3 were 3.8, 4.6, and 8.3 Gt, respectively. A sensitivity analysis shows that for any given quantity of fish backscatter, the fish swimbladder volume, its size distribution and its aspect ratio are the parameters that cause most variation (i.e. lead to greatest uncertainty) in the biomass estimate. Determination of these parameters should be prioritized in future studies, as should determining the proportion of backscatter due to siphonophores.

chapter 7 Carbon Export Efficiency and Phytoplankton Community Composition in the Atlantic Sector of the Arctic Ocean

2017 ◽  
pp. 149-188
Author(s):  
FRÉDÉRIC A. C. LE MOIGNE ◽  
ALEX J. POULTON ◽  
STEPHANIE A. HENSON ◽  
CHRIS J. DANIELS ◽  
GLAUCIA M. FRAGOSO ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Community Composition ◽  
Phytoplankton Community ◽  
The Arctic ◽  
Carbon Export ◽  
Atlantic Sector ◽  
Phytoplankton Community Composition ◽  
The Arctic Ocean

scholarly journals Contrasting pelagic ecosystem functioning in eastern and western Baffin Bay revealed by trophic network modeling

Elem Sci Anth ◽  
2020 ◽  
Vol 8 ◽  
Author(s):  
Blanche Saint-Béat ◽  
Brian D. Fath ◽  
Cyril Aubry ◽  
Jonathan Colombet ◽  
Julie Dinasquet ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Food Web ◽  
Biological Data ◽  
The Arctic ◽  
Ecosystem Structure ◽  
Carbon Export ◽  
Baffin Bay ◽  
Planktonic Food ◽  
Carbon Transfer ◽  
Current Flows

Baffin Bay, located at the Arctic Ocean’s ‘doorstep’, is a heterogeneous environment where a warm and salty eastern current flows northwards in the opposite direction of a cold and relatively fresh Arctic current flowing along the west coast of the bay. This circulation affects the physical and biogeochemical environment on both sides of the bay. The phytoplanktonic species composition is driven by its environment and, in turn, shapes carbon transfer through the planktonic food web. This study aims at determining the effects of such contrasting environments on ecosystem structure and functioning and the consequences for the carbon cycle. Ecological indices calculated from food web flow values provide ecosystem properties that are not accessible by direct in situ measurement. From new biological data gathered during the Green Edge project, we built a planktonic food web model for each side of Baffin Bay, considering several biological processes involved in the carbon cycle, notably in the gravitational, lipid, and microbial carbon pumps. Missing flow values were estimated by linear inverse modeling. Calculated ecological network analysis indices revealed significant differences in the functioning of each ecosystem. The eastern Baffin Bay food web presents a more specialized food web that constrains carbon through specific and efficient pathways, leading to segregation of the microbial loop from the classical grazing chain. In contrast, the western food web showed redundant and shorter pathways that caused a higher carbon export, especially via lipid and microbial pumps, and thus promoted carbon sequestration. Moreover, indirect effects resulting from bottom-up and top-down control impacted pairwise relations between species differently and led to the dominance of mutualism in the eastern food web. These differences in pairwise relations affect the dynamics and evolution of each food web and thus might lead to contrasting responses to ongoing climate change.

scholarly journals Direct observation of the setular web that fuses thoracopodal setae of a calanoid copepod into a collapsible fan

2019 ◽  
Author(s):  
George von Dassow ◽  
Richard B. Emlet
Keyword(s):  
Food Webs ◽  
Carbon Flux ◽  
High Speed ◽  
Calanoid Copepod ◽  
Swimming Performance ◽  
Structure And Function ◽  
High Speed Video ◽  
Aquatic Food ◽  
And Function ◽  
Oceanic Carbon

SummaryCopepods are numerically dominant planktonic grazers throughout the waters of Earth, preyed upon in turn by a wide diversity of pelagic animals (1,2). Their feeding and swimming performance thus has global importance to aquatic food webs and oceanic carbon flux. These crustaceans swim and feed using cuticle-covered, segmented, muscular appendages whose reach is extended greatly by setae, extracellular chitinous extensions with diverse structure and function (3). Plumose setae, with subsidiary setules arranged like barbs on a feather, have well-documented roles in generating feeding and swimming currents (4,5). Recent work showed that plumose setae of barnacle cyprid thoracopods are permanently linked by setules into a single fan that opens and closes as one sheet during high-speed swimming (6). Intersetular linkage across cyprid thoracopods may greatly decrease leakage between extended setae, ensure even spread of setae within the fan, and promote ordered collapse of the fan to avoid entanglement of adjacent appendages. Here we demonstrate similar setular webbing amongst thoracopod setae in the calanoid copepod Acartia sp. High-speed video directly documents the existence of such links, and reveals that individuals experience apparently-irreparable degradation of the setal array due to de-linkage, with likely consequences for swimming performance.

scholarly journals Spatial and Temporal Modelling of Biophysical Variables Within A High Arctic Wetland

2021 ◽  
Author(s):  
Gillian Ramasay
Keyword(s):  
Dynamic Systems ◽  
Temporal Variability ◽  
Hot Spots ◽  
Carbon Flux ◽  
Seasonal Changes ◽  
High Arctic ◽  
The Arctic ◽  
Layer Depth ◽  
Wetland Ecosystems ◽  
Temporal Modelling

The Arctic has experienced greater climate warming in the last decade than anywhere else, potentially shifting its carbon status from a sink to a source. Increasing temperatures impact nival wetlands that rely on a strong hydrological input from melting perennial snowpacks. Soil moisture, soil temperature and active layer depth are key biophysical variables in predicting carbon flux trajectories in this environment. How these variables interact is crucial in delineating links between snowmelt and seasonal changes in wetland productivity. To date, there have been numerous studies that have examined these variables, but few have investigated the relationships between these biophysical variables and wetland thaw patterns at a high spatial and temporal scale. This study found a decrease in temporal variability and reduced interactions between variables as the wetland thawed as well as localized hot spots of increased values and an overall east to west trend across the site. This implies that Arctic wetland ecosystems are dynamic systems that reach a level of stability during peak growth. They also exhibit changeable spatial patterns that cannot be generalized.

Separating the influences of low-latitude warming and sea-ice loss on Northern Hemisphere climate change

2022 ◽  
pp. 1-59
Author(s):  
Paul J. Kushner ◽  
Russell Blackport ◽  
Kelly E. McCusker ◽  
Thomas Oudar ◽  
Lantao Sun ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
High Latitude ◽  
North Pacific ◽  
Heat Fluxes ◽  
The Arctic ◽  
Low Latitude ◽  
The Arctic Ocean

Abstract Analyzing a multi-model ensemble of coupled climate model simulations forced with Arctic sea-ice loss using a two-parameter pattern-scaling technique to remove the cross-coupling between low- and high-latitude responses, the sensitivity to high-latitude sea-ice loss is isolated and contrasted to the sensitivity to low-latitude warming. In spite of some differences in experimental design, the Northern Hemisphere near-surface atmospheric sensitivity to sea-ice loss is found to be robust across models in the cold season; however, a larger inter-model spread is found at the surface in boreal summer, and in the free tropospheric circulation. In contrast, the sensitivity to low-latitude warming is most robust in the free troposphere and in the warm season, with more inter-model spread in the surface ocean and surface heat flux over the Northern Hemisphere. The robust signals associated with sea-ice loss include upward turbulent and longwave heat fluxes where sea-ice is lost, warming and freshening of the Arctic ocean, warming of the eastern North Pacific relative to the western North Pacific with upward turbulent heat fluxes in the Kuroshio extension, and salinification of the shallow shelf seas of the Arctic Ocean alongside freshening in the subpolar North Atlantic. In contrast, the robust signals associated with low-latitude warming include intensified ocean warming and upward latent heat fluxes near the western boundary currents, freshening of the Pacific Ocean, salinification of the North Atlantic, and downward sensible and longwave fluxes over the ocean.

Changes in phytoplankton concentration now drive increased Arctic Ocean primary production

Science ◽  
2020 ◽  
Vol 369 (6500) ◽  
pp. 198-202 ◽  
Author(s):  
K. M. Lewis ◽  
G. L. van Dijken ◽  
K. R. Arrigo
Keyword(s):  
Sea Ice ◽  
Primary Production ◽  
Arctic Ocean ◽  
Open Water ◽  
Water Area ◽  
The Arctic ◽  
Carbon Export ◽  
Phytoplankton Primary Production ◽  
Open Water Area ◽  
The Arctic Ocean

Historically, sea ice loss in the Arctic Ocean has promoted increased phytoplankton primary production because of the greater open water area and a longer growing season. However, debate remains about whether primary production will continue to rise should sea ice decline further. Using an ocean color algorithm parameterized for the Arctic Ocean, we show that primary production increased by 57% between 1998 and 2018. Surprisingly, whereas increases were due to widespread sea ice loss during the first decade, the subsequent rise in primary production was driven primarily by increased phytoplankton biomass, which was likely sustained by an influx of new nutrients. This suggests a future Arctic Ocean that can support higher trophic-level production and additional carbon export.

scholarly journals Fluvial organic carbon flux from an eroding peatland catchment, southern Pennines, UK

2008 ◽  
Vol 12 (2) ◽  
pp. 625-634 ◽  
Author(s):  
R. R. Pawson ◽  
D. R. Lord ◽  
M. G. Evans ◽  
T. E. H. Allott
Keyword(s):  
Organic Carbon ◽  
Carbon Flux ◽  
Relative Importance ◽  
Carbon Export ◽  
Event Scale ◽  
Organic Carbon Flux ◽  
Poc Export ◽  
Event Based ◽  
First Time ◽  
Annual Flux

Abstract. This study investigates for the first time the relative importance of dissolved organic carbon (DOC) and particulate organic carbon (POC) in the fluvial carbon flux from an actively eroding peatland catchment in the southern Pennines, UK. Event scale variability in DOC and POC was examined and the annual flux of fluvial organic carbon was estimated for the catchment. At the event scale, both DOC and POC were found to increase with discharge, with event based POC export accounting for 95% of flux in only 8% of the time. On an annual cycle, exports of 35.14 t organic carbon (OC) are estimated from the catchment, which represents an areal value of 92.47 g C m−2 a−1. POC was the most significant form of organic carbon export, accounting for 80% of the estimated flux. This suggests that more research is required on both the fate of POC and the rates of POC export in eroding peatland catchments.

scholarly journals The sporadic radiant and distribution of meteors in the atmosphere as observed by VHF radar at Arctic, Antarctic and equatorial latitudes

2009 ◽  
Vol 27 (7) ◽  
pp. 2831-2841 ◽  
Author(s):  
P. T. Younger ◽  
I. Astin ◽  
D. J. Sandford ◽  
N. J. Mitchell
Keyword(s):  
Spatial Variability ◽  
Annual Cycle ◽  
High Latitude ◽  
The Arctic ◽  
Low Latitude ◽  
Vhf Radar ◽  
Ascension Island ◽  
Temporal And Spatial Variability ◽  
Temporal And Spatial ◽  
Celestial Sphere

Abstract. Results are presented of a study of the temporal and spatial variability in meteor count rate observations from three VHF meteor radars. These radar are located in the Arctic (at Esrange, 68° N), in the Antarctic (at Rothera, 68° S) and near the Equator (on Ascension Island, 8° S). It is found that for all three locations there is a strong diurnal cycle in observed hourly meteor counts and the time of maxima and minima in these counts depends on the month of the year. In addition, at high latitude there is a strong annual cycle in observed monthly-mean meteor counts, whereas for the radar at low latitude there is a semi-annual cycle. At high latitude there is also an annual cycle in the mean height at which meteors are observed. However, no such annual cycle is found in observed meteor count rates from the low latitude radar. The meteor count data from all the radars are combined to investigate the sporadic radiant distribution (i.e. the distribution of direction of arrival on the celestial sphere of sporadic meteors). This combined radiant distribution shows that there are six main source regions for meteors. The latitudinal and temporal dependence in observed meteor count rates appears to result from a combination of the sporadic radiant distribution, annual fluctuations in atmospheric density, the sensitivity of the radar to meteors from different source directions and the temporal and spatial variability in meteor fluxes.

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