DVM: The World’s Biggest Game of Hide-and-Seek

Diel vertical migration (DVM) refers to the daily, synchronized movement of marine animals between the surface and deep layers of the open ocean. This behavior is the largest animal migration on the planet and is undertaken every single day by trillions of animals in every ocean. Like a big game of hide-and-seek, animals that perform DVM spend the day hiding from predators in the deep ocean, and then migrate to the surface to feed under the cover of darkness. In this article we will explore this incredible strategy for survival. We will introduce the animals involved, describe how the environment of the open ocean drives DVM, and reveal the questions still to be answered as the ocean environment continues to change

Assessing key influences on the distribution and life-history of Arctic and boreal Calanus: are online databases up to the challenge?

Despite the importance of calanoid copepods to healthy ecosystem functioning of the Arctic Ocean and Subarctic Seas, many aspects of their biogeography, particularly in winter months, remain unresolved. At the same time, online databases that digitize species distribution records are growing in popularity as a tool to investigate ecological patterns at macro scales. The value of such databases for Calanus research requires investigation - the long history of Calanus sampling holds promise for such databases, while conditions at high latitudes may impose limits through spatial and temporal biases. We collated records of three Calanus species (C. finmarchicus, C. glacialis, and C. hyperboreus) from the Ocean Biodiversity Information System (OBIS) and the Global Biodiversity Information Facility (GBIF) providing over 230,000 unique records spanning 150 years and over 100 individual datasets. After quality control and cleaning, the latitudinal and vertical distribution of occurrences were explored, as well as the completeness of informative metadata fields. Calanus sampling was found to be temporally and spatially biased towards surfacemost layers (<10m) in spring and summer. Only 3.5% of records had an average collection depth ≥400m, approximately half of these in months important for diapause. Just over 40% of records lacked associated information on sampling protocol while 11% of records lacked life-stage information. OBIS data contained fields for maximum and minimum collection depth and so were subset into discrete “shallow summer” and “deep winter” life cycle phases and matched to sea-ice and temperature conditions. 23% of OBIS records north of 66° latitude were located in regions of seasonal sea-ice presence and occurrences show species-specific thermal optima during the shallow summer period. The collection depth of C. finmarchicus was significantly different to C. hyperboreus during the deep winter. Overall, online databases contain a vast number of Calanus records but sampling biases should be acknowledged when they are used to investigate patterns of biogeography. We advocate efforts to integrate additional data sources within online portals. Particular gaps to be filled by existing or future collections are (i) widening the spatial extent of sampling during spring/summer months, (ii) increasing the frequency of sampling during winter, particularly at depths below 400m, and (iii) improving the quality, quantity and consistency of metadata reporting

Climate change drives poleward increases and equatorward declines in marine species

Marine environments have increased in temperature by an average of 1°C since preindustrial (1850) times [1]. Given that species ranges are closely allied to physiological thermal tolerances in marine organisms [2], it may therefore be expected that ocean warming would lead to abundance increases at poleward range edges, and abundance declines towards the equator [3]. Here we report a global analysis of abundance tends of 304 widely distributed marine species over the last century, across a range of taxonomic groups from phytoplankton to fish and marine mammals. Specifically, using a literature database we investigate the extent that the direction and strength of longterm species abundance changes depend on the sampled location within the latitudinal range of species. Our results show that abundance increases have been most prominent where sampling has taken place at the poleward edges of species ranges, while abundance declines have been most prominent where sampling has taken place at the equatorward edge of species ranges. These data provide evidence of omnipresent large-scale changes in abundance of marine species consistent with warming over the last century, and suggest that adaptation has not provided a buffer against the negative effects of warmer conditions at the equatorward extent of species ranges. On the basis of these results we suggest that projected sea temperature increases of up to 1.5°C over pre-industrial levels by 2050 [4] will continue to drive latitudinal abundance shifts in marine species, including those of importance for coastal livelihoods

Visual predation risk and spatial distributions of large Arctic copepods along gradients of sea ice and bottom depth

Changes in the community size structure of Arctic copepods toward smaller and less fat individuals or species have been linked to environmental changes. The underpinning mechanisms are, however, poorly understood. We use a two-step hurdle regression model to analyze spatially resolved, long-term survey data of the Barents Sea mesozooplankton community along gradients of water mass properties, sea ice, and bottom depth. We test the hypothesis that reduced visual predation, and hence increased survival in dim habitats, explains the distribution of large copepods. We expect the presence and biomass of large copepods to increase with increasing bottom depth and the occurrence of seasonal ice-cover. The patterns and drivers that emerge from our analysis support our hypothesis: in the Barents Sea large copepods were predominantly found in deep troughs that intersect the shelf south of the polar front, or at shallower depths in seasonally ice-covered waters northeast of Svalbard. On the banks, large copepods are largely absent whereas smaller copepods appear to survive. Top-down control provides one plausible explanation for these distributions. Large copepods survive where sea-ice shades the water or deep habitats permit escape from visual predators through vertical migrations. However, when upwelled onto shallow banks or flushed out from below the ice they are decimated by visual foragers. Therefore, advection and topographic blockage of vertical zooplankton distributions are key mechanisms for the efficient energy transfer and productivity in subarctic and Arctic shelf seas. New prolific foraging grounds may open up for planktivores where the ice-edge recedes under a changing climate

Illuminating the Living Lanterns of Antarctica

Lanternfish are a relatively small but very abundant fish. They live deep in the ocean’s “twilight” zone where there is not much light. A unique community of lanternfish live in the Southern Ocean, where they are a key part of the Antarctic food web. Lanternfish also play an important role in moving carbon from the atmosphere into the deep ocean, where it is stored. In this article, we explain current knowledge on Southern Ocean lanternfish, including how they produce their own light! We will also tell you about some mysteries surrounding lanternfish that scientists are yet to solve

Assessing the trophic ecology of Southern Ocean Myctophidae: the added value of DNA metabarcoding

Lanternfishes (Myctophidae) are key components of mesopelagic fish communities globally. In the Southern Ocean, incomplete information on myctophid diets limits our understanding of their energetics, interactions and wider ecosystem impact. Traditional microscopic methods of diet analysis have relatively coarse prey resolution and possible taxonomic and observer biases. DNA metabarcode sequencing promises higher taxonomic and temporal resolution, but uncertainty remains in comparing this is with microscopy-based analyses. Here, we applied 18S DNA metabarcode sequencing to stomach contents from twenty Electrona antarctica individuals which had previously been examined via microscopic analysis. Across all fish, crustacean and gastropod taxa dominated the prey identified via both methods, with broad agreement between methods on the relative abundance of different prey items. DNA metabarcode sequencing recovered greater taxonomic diversity and resolution, particularly for soft-bodied prey items and small crustaceans. DNA sequencing results also more clearly differentiated diet between individuals collected from different environments. Overall, our findings illustrate how DNA based methods are complementary to, and consistent with, traditional methods and can provide additional, high-resolution data on a range of trophic interactions

Duke Activity Status Index and Liver Frailty Index predict mortality in ambulatory patients with advanced chronic liver disease:A prospective, observational study

BACKGROUND: There remains a lack of consensus on how to assess functional exercise capacity and physical frailty in patients with advanced chronic liver disease (CLD) being assessed for liver transplantation (LT). Aim To investigate prospectively the utility of the Duke Activity Status Index (DASI) and Liver Frailty Index (LFI) in ambulatory patients with CLD.AIM: To investigate prospectively the utility of the Duke Activity Status Index (DASI) and Liver Frailty Index (LFI) in ambulatory patients with CLD.METHODS: We recruited patients from outpatient clinics at University Hospitals Birmingham, UK (2018-2019). We prospectively collated the DASI and LFI to identify the prevalence of, respectively, functional capacity and physical frailty, and to evaluate their accuracy in predicting overall and pre-LT mortality.RESULTS: We studied 307 patients (57% male; median age 54 years; UKELD 52). Median DASI score was 28.7 (IQR 16.2-50.2), mean LFI was 3.82 (SD = 0.72), and 81% were defined either 'pre-frail' or 'frail'. Female sex and hyponatraemia were significant independent predictors of both DASI and LFI. Age and encephalopathy were significant independent predictors of LFI, while BMI significantly predicted DASI. DASI and LFI were significantly related to overall (HR 0.97, p = 0.001 [DASI], HR 2.04, p = 0.001 [LFI]) and pre-LT mortality (HR 0.96, p = 0.02 [DASI], HR 1.94, p = 0.04 [LFI]).CONCLUSIONS: Poor functional exercise capacity and physical frailty are highly prevalent among ambulatory patients with CLD who are being assessed for LT. The DASI and LFI are simple, low-cost tools that predict overall and pre-LT mortality. Implementation of both should be considered in all outpatients with CLD to highlight those who may benefit from targeted nutritional and exercise interventions.</p

Duke Activity Status Index and Liver Frailty Index predict mortality in ambulatory patients with advanced chronic liver disease:A prospective, observational study

BACKGROUND: There remains a lack of consensus on how to assess functional exercise capacity and physical frailty in patients with advanced chronic liver disease (CLD) being assessed for liver transplantation (LT). Aim To investigate prospectively the utility of the Duke Activity Status Index (DASI) and Liver Frailty Index (LFI) in ambulatory patients with CLD.AIM: To investigate prospectively the utility of the Duke Activity Status Index (DASI) and Liver Frailty Index (LFI) in ambulatory patients with CLD.METHODS: We recruited patients from outpatient clinics at University Hospitals Birmingham, UK (2018-2019). We prospectively collated the DASI and LFI to identify the prevalence of, respectively, functional capacity and physical frailty, and to evaluate their accuracy in predicting overall and pre-LT mortality.RESULTS: We studied 307 patients (57% male; median age 54 years; UKELD 52). Median DASI score was 28.7 (IQR 16.2-50.2), mean LFI was 3.82 (SD = 0.72), and 81% were defined either 'pre-frail' or 'frail'. Female sex and hyponatraemia were significant independent predictors of both DASI and LFI. Age and encephalopathy were significant independent predictors of LFI, while BMI significantly predicted DASI. DASI and LFI were significantly related to overall (HR 0.97, p = 0.001 [DASI], HR 2.04, p = 0.001 [LFI]) and pre-LT mortality (HR 0.96, p = 0.02 [DASI], HR 1.94, p = 0.04 [LFI]).CONCLUSIONS: Poor functional exercise capacity and physical frailty are highly prevalent among ambulatory patients with CLD who are being assessed for LT. The DASI and LFI are simple, low-cost tools that predict overall and pre-LT mortality. Implementation of both should be considered in all outpatients with CLD to highlight those who may benefit from targeted nutritional and exercise interventions.</p

Boris Havel, Pregled povijesti Izraela. Od Abrahama do moderne države, Zagreb, Antibarbarus, 2015, 308 str.

Long-term monitoring of seabird numbers around Antarctica has revealed that the chinstrap penguin (Pygoscelis antarctica) is largely declining throughout its range in the Scotia Arc. Whether archipelagos across this large area remain connected via dispersal or represent genetically isolated groups has not yet been established. The purpose of this study was to assess the level of genetic differentiation between four breeding colonies on the Western Antarctic Peninsula (WAP), South Shetland, South Orkney, and South Sandwich Islands using microsatellite-based analysis of population structure. All colonies had similar levels of genetic diversity (mean heterozygosity, H O = 0.583) but colonies from the WAP and South Orkney Island had significant inbreeding coefficients. Hierarchical and pairwise F-statistics revealed very limited population structure in the Scotia Arc, with weak differentiation between colonies from the WAP, South Shetland and South Orkney Islands relative to the South Sandwich Islands, which are situated at least 1000 km apart from these other archipelagos. Bayesian model-based clustering methods found no evidence of significant population structuring, suggesting that whilst some isolation by distance may occur, there are no strong barriers to dispersal across this wide geographic range. No evidence of sex-biased dispersal was detected. We conclude that chinstrap penguin colonies across the Scotia Arc represent one interconnected breeding population. High levels of gene flow may be important in maintaining smaller, less stable colonies, and this status should be preserved by creating dispersal corridors throughout the Scotia Arc