Biogeography of the global ocean's mesopelagic zone

The work has arisen from a PhD studentship funded by Australian Antarctic Division, University of Tasmania, and School of Biology. This study has received support from the European H2020 International Cooperation project MESOPP (Mesopelagic Southern Ocean Prey and Predators; http://www.mesopp.eu/).The global ocean’s near-surface can be partitioned into distinct provinces on the basis of regional primary productivity and oceanography [1]. This ecological geography provides a valuable framework for understanding spatial variability in ecosystem function, but has relevance only part way into the epipelagic zone (the top 200 m). The mesopelagic (200-1,000 m) makes up c. 20% of the global ocean volume, plays important roles in biogeochemical cycling [2], and holds potentially huge fish resources [3–5]. It is however hidden from satellite observation, and a lack of globally-consistent data has prevented development of a global-scale understanding. Acoustic Deep Scattering Layers (DSLs) are prominent features of the mesopelagic. These vertically-narrow (10s-100s of m) but horizontally-extensive (continuous for 10s-1,000s of km) layers comprise fish and zooplankton, and are readily detectable using echosounders. We have compiled a database of DSL characteristics globally. We show here that DSL depth and acoustic backscattering intensity (a measure of biomass) can be modelled accurately using just surface primary productivity, temperature and wind-stress. Spatial variability in these environmental factors leads to a natural partition of the mesopelagic into 10 distinct classes. These classes demark a more complex biogeography than the latitudinally-banded schemes proposed before [6,7]. Knowledge of how environmental factors influence the mesopelagic enables future change to be explored: we predict that by 2100 there will be widespread homogenisation of mesopelagic communities, and that mesopelagic biomass could increase by c. 17%. The biomass increase requires increased trophic efficiency, which could arise because of ocean warming and DSL shallowing.PostprintPeer reviewe

Ecosystem approach to harvesting in the Arctic : walking the tightrope between exploitation and conservation in the Barents Sea

Funidng: This study was supported by the Changing Arctic Ocean project MiMeMo (NE/R012679/1) jointly funded by the UKRI Natural Environment Research Council (NERC) and the German Federal Ministry of Education and Research (BMBF/03F0801A). Brierley was also supported by ArcticPRIZE (NE/P005721/1).Projecting the consequences of warming and sea-ice loss for Arctic marine food web and fisheries is challenging due to the intricate relationships between biology and ice. We used StrathE2EPolar, an end-to-end (microbes-to-megafauna) food web model incorporating ice-dependencies to simulate climate-fisheries interactions in the Barents Sea. The model was driven by output from the NEMO-MEDUSA earth system model, assuming RCP 8.5 atmospheric forcing. The Barents Sea was projected to be > 95% ice-free all year-round by the 2040s compared to > 50% in the 2010s, and approximately 2 °C warmer. Fisheries management reference points (FMSY and BMSY) for demersal fish (cod, haddock) were projected to increase by around 6%, indicating higher productivity. However, planktivorous fish (capelin, herring) reference points were projected to decrease by 15%, and upper trophic levels (birds, mammals) were strongly sensitive to planktivorous fish harvesting. The results indicate difficult trade-offs ahead, between harvesting and conservation of ecosystem structure and function.Publisher PDFPeer reviewe

Fine-scale depth structure of pelagic communities throughout the global ocean based on acoustic sound scattering layers

Most multicellular biomass in the mesopelagic zone (200-1000 m) comprises zooplankton and fish aggregated in layers known as sound scattering layers (SSLs), which scatter sound and are detectable using echosounders. Some of these animals migrate vertically to and from the near surface on a daily cycle (diel vertical migration, DVM), transporting carbon between the surface and the deep ocean (biological carbon pump, BCP). To gain insight into potential global variability in the contribution of SSLs to the BCP, and to pelagic ecology generally (SSLs are likely prey fields for numerous predators), we investigated regional-scale (90000 km2) community depth structure based on the fine-scale (10s of m) vertical distribution of SSLs. We extracted SSLs from a near-global dataset of 38 kHz echosounder observations and constructed local (300 km × 300 km) SSL depth and echo intensity (a proxy for biomass) probability distributions. The probability distributions fell into 6 spatially coherent regional-scale SSL probability distribution (RSPD) groups. All but 1 RSPD exhibited clear DVM, and all RSPDs included stable night-time resident deep scattering layers (DSLs: SSLs deeper than 200 m). Analysis of DSL number and stability (probability of observation at depth) revealed 2 distinct DSL types: (1) single-shallow DSL (a single DSL at ca. 500 m) and (2) double-deep DSL (2 DSLs at ca. 600 and 850 m). By including consideration of this fine-scale depth structure in biogeographic partitions and ecosystem models, we will better understand the role of mesopelagic communities in pelagic food webs and the consequences of climate change for these communities.PostprintPeer reviewe

How is climate change affecting marine life in the Arctic?

Rising temperature is melting the ice that covers the Arctic Ocean, allowing sunlight into waters that have been dark for thousands of years. Previously barren ice-covered regions are being transformed into productive seas. Here we explain how computer modelling can be used to predict how this transformation will affect the food web that connects plankton to fish and top-predators like whales and polar bears. Images of starving polar bears have become symbolic of the effects of warming climate. Melting of the sea-ice is expected to reduce the bears’ ability to hunt for seals. However, at the same time, the food web upon which they depend is becoming more productive, so it is not completely clear what the eventual outcome will be for the bears. Computer models help us to understand these systems and inform policy decisions on the management of newly available Arctic resources

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

Funding: Horizon 2020 Framework Programme, (Grant/Award Number: “692173”).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.Publisher PDFPeer reviewe

The Simrad EK60 echosounder dataset from the Malaspina circumnavigation

The Malaspina Expedition was funded by the Spanish Ministry of Economy and Competitiveness through the Malaspina 2010 expedition project (Consolider-Ingenio 2010, CSD2008-00077), the Fundación BBVA, CSIC, the Spanish Institute of Oceanography, AZTI Foundation, the universities of Granada, Cadiz, Basque Country and Barcelona and the King Abdullah University of Science and Technology. Data have been made available through the EU funded project SUMMER (H2020-BG-2018-2, proposal number: 817806-2).We provide the raw acoustic data collected from the R/V Hesperides during the global Malaspina 2010 Spanish Circumnavigation Expedition (14th December 2010, Cádiz-14th July 2011, Cartagena) using a Simrad EK60 scientific echosounder operating at 38 and 120 kHz. The cruise was divided into seven legs: leg 1 (14th December 2010, Cádiz-13th January 2011, Rio de Janeiro), leg 2 (17th January 2011, Rio de Janeiro-6th February 2011, Cape Town), leg 3 (11th February 2011, Cape Town-13th March 2011, Perth), leg 4 (17th March 2011, Perth-30th March 2011, Sydney), leg 5 (16th April 2011, Auckland-8th May 2011, Honolulu), leg 6 (13th May 2011, Honolulu-10th June 2011, Cartagena de Indias) and leg 7 (19th June 2011, Cartagena de Indias-14th July 2011, Cartagena). The echosounder was calibrated at the start of the expedition and calibration parameters were updated in the data acquisition software (ER60) i.e., the logged raw data are calibrated. We also provide a data summary of the acoustic data in the form of post-processed products.Publisher PDFPeer reviewe

Modelling the effects of changes in sea-ice extent on Arctic marine food webs

Diminishing extent of sea-ice cover in the Arctic over recent decades is well documented, and linked to global warming. The ecological effects have been profound especially in areas which have transformed from extensive seasonal ice-cover, to marginal sea-ice or year-round open water. The effects include an increase in Arctic primary production and changes in habitat and food availability for iconic marine mammals. Fishing nations anticipate increased harvesting opportunities in the Arctic as ice cover retreats further, but in November 2017 an international agreement was reached to prevent fisheries development in the Central Arctic Ocean for at least the next 16 years, to give time for development of scientific understanding. The scope for changes primary production due to diminishing sea-ice to propagate through the food web and affect higher trophic levels and charismatic megafauna such as whales, seals and polar bears, is extremely uncertain and hard to predict. The classical hypothesis would be that warming climate will result in a bottom-up trophic cascade from a) increased primary production, to b) increased zooplankton production, to c) increased fish production and harvesting potential, through to d) increased populations of charismatic marine megafauna. However, this assumes that primary production is retained in the upper layers of the water column – the outcome could be quite different if changes in vertical mixing and animal behavior associated with loss of ice cover lead instead to a greater proportion of primary production being directed to the benthos. Here we report on results from a configuration of the StrathE2E marine food web model to represent the Barents Sea. First, we show a baseline model representing sea-ice and temperature conditions during the 1980s-1990s, and then compare this with results from simulation of a warmer, year-round ice-free scenario. The results show that the increase in primary production in the ice-free scenario is amplified as it cascades up the food web. The effects preferentially benefit benthos and demersal fish, but this result is sensitive assumptions about prey preferences and vertical mixing. We also show how the food web responds to harvesting of fish, under both contemporary ice-cover and future ice-free situations. The results presented here are a starting point for a much more extensive new project under the NERC Charging Arctic Ocean Programme (Microbes to Megafauna Modelling of Arctic Seas (MiMeMo)) which we briefly introduce

Using predicted patterns of 3D prey distribution to map king penguin foraging habitat

FUNDING The at-sea data collection and 50% of CLG’s Ph.D. studentship was provided by the Swiss Polar Institute as a grant ‘Unlocking the Secrets of the False Bottom’ to ASB. The School of Biology, University of St Andrews, funded the other 50% of CLG’s studentship. Work at South Georgia was supported by the Natural Environment Research Council’s Collaborative Antarctic Science Scheme (CASS-129), a grant from the TransAntarctic Association grant to RBS, and a British Antarctic Survey Collaborative Gearing Scheme grant to RBS and ASB. ASB and RP were supported in part by UKRI/NERC under grant NE/R012679/1. ACKNOWLEDGMENTS We thank the staff at the British Antarctic Survey base at King Edward Point (South Georgia), Quark Expeditions and the crew and staff of the Ocean Endeavour and the FPV Pharos South Georgia for their help with the fieldwork logistics. We also thank the Swiss Polar Institute and the ACE foundation for funding our ACE project, and all our colleagues who assisted with acoustic data collection at sea: Matteo Bernasconi, Inigo Everson, and Joshua Lawrence. We thank Yves Cherel for fruitful discussion on the role of prey patches for king penguins in the Kerguelen region. We also thank C. Ribout and the Centre for Biological Studies of Chizé for conducting the sexing analyses of the birdsPeer reviewedPublisher PD

Post-Operative Functional Outcomes in Early Age Onset Rectal Cancer

Background: Impairment of bowel, urogenital and fertility-related function in patients treated for rectal cancer is common. While the rate of rectal cancer in the young (<50 years) is rising, there is little data on functional outcomes in this group. Methods: The REACCT international collaborative database was reviewed and data on eligible patients analysed. Inclusion criteria comprised patients with a histologically confirmed rectal cancer, <50 years of age at time of diagnosis and with documented follow-up including functional outcomes. Results: A total of 1428 (n=1428) patients met the eligibility criteria and were included in the final analysis. Metastatic disease was present at diagnosis in 13%. Of these, 40% received neoadjuvant therapy and 50% adjuvant chemotherapy. The incidence of post-operative major morbidity was 10%. A defunctioning stoma was placed for 621 patients (43%); 534 of these proceeded to elective restoration of bowel continuity. The median follow-up time was 42 months. Of this cohort, a total of 415 (29%) reported persistent impairment of functional outcomes, the most frequent of which was bowel dysfunction (16%), followed by bladder dysfunction (7%), sexual dysfunction (4.5%) and infertility (1%). Conclusion: A substantial proportion of patients with early-onset rectal cancer who undergo surgery report persistent impairment of functional status. Patients should be involved in the discussion regarding their treatment options and potential impact on quality of life. Functional outcomes should be routinely recorded as part of follow up alongside oncological parameters

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries