27 research outputs found
[Corrigendum to] Effects of small-scale turbulence on lower trophic levels under different nutrient conditions [vol 32, pg 197, 2010]
Small-scale turbulence affects the pelagic food web and energy flow in marine systems and the impact is related to nutrient conditions and the assemblage of organisms present. We generated five levels of turbulence (2*10 29 to 1*10 24 W kg 21 ) in land-based mesocosms (volume 2.6 m 3 ) with and without additional nutrients (31:16:1 Si:N:P m M) to asses the effect of small-scale turbulence on the lower part of the pelagic food web under different nutrient conditions. The ecological influence of nutrients and small-scale turbulence on lower trophic levels was quantified using multivariate statistics (RDA), where nutrients accounted for 31.8% of the observed biological variation, while 7.2% of the variation was explained by small-scale turbulence and its interaction with nutrients. Chlorophyll a, primary production rates, bacterial production rates and diatom and dinoflagellate abundance were positively correlated to turbulence, regardless of nutrient conditions. Abundance of autotrophic flagellates, total phytoplankton and bacteria were positively correlated to turbulence only when nutrients were added. Impact of small-scale turbulence was related to nutrient con-
ditions, with implications for oligotrophic and eutrophic situations. The effect on community level was also different compared to single species level. Microbial processes drive biogeochemical cycles, and nutrient-controlled effects of small-scale turbulence on such processes are relevant to foresee altered carbon flow in marine systems
The state of the Martian climate
60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes
Quantitative estimates of unique continuation for parabolic equations, determination of unknown time-varying boundaries and optimal stability estimates
In this paper we will review the main results concerning the issue of
stability for the determination unknown boundary portion of a thermic
conducting body from Cauchy data for parabolic equations. We give detailed and
selfcontained proofs. We prove that such problems are severely ill-posed in the
sense that under a priori regularity assumptions on the unknown boundaries, up
to any finite order of differentiability, the continuous dependence of unknown
boundary from the measured data is, at best, of logarithmic type
Soda and Tobacco Industry Corporate Social Responsibility Campaigns: How Do They Compare?
In an article that forms part of the PLoS Medicine series on Big Food, Andrew Cheyne and colleagues compare soda companies' corporate social responsibility (CSR) campaigns - which are designed to bolster the image and popularity of their products and to prevent regulation - with the tobacco industry's CSR campaigning
Quantifying zoobenthic blue carbon storage across habitats within the Arctic’s Barents Sea
Introduction: The Arctic sea ice extent in September (when it is at its lowest) has
declined 13% Q10 per decade, and the Arctic Ocean is becoming a more
Atlantic-influenced system. Rapid climate-forced changes are taking place in
many high-latitude marine ecosystems. The Barents Sea is one such highlatitude shelf ecosystem, between approximately 70° and 80°N in the
Norwegian Arctic. The purpose of the current study was to estimate
zoobenthic blue carbon across multiple habitats within the Barents Sea
(trough, basin, shelf, and shallows), potentially providing values to aid
ecosystem-based management of these areas under future climate
change scenarios.
Method: We tested this by capture and analysis of 947 high-resolution (each
405.7 × 340.6 mm, 12 MB, 5 megapixels) seabed images at 17 sites with latitudinal
cline, linked to a collection of corresponding oceanographic data. Biotas within
these images were identified to one of the 14 functional groups and the density
was calculated. Mean stored carbon per individual was assigned by ash mass (AM)
and ash-free dry mass (AFDM) of individuals caught within Agassiz trawl
deployments at the same sites.
Results: Trough sites, except for one site (B16), have a low quantity of zoobenthic
blue carbon compared with the shallow, shelf, and basin habitats.
Discussion: The results of a previous study focused entirely on trough habitats
and are therefore difficult to scale up as the basis for a meaningful estimate of
across-habitat zoobenthic blue carbon in the Barents Sea. Compared with the
trough and the basin, the shelf and shallow habitats of the Barents Sea are also
subjected to more trawling events through demersal fisheries and showed higher
zoobenthic blue carbon stock values
Modeling suggests frequency estimates are not informative for predicting the long-term effect of horizontal gene transfer in bacteria
Horizontal gene transfer (HGT) is an important mechanism by which bacteria recombine and acquire novel genes and functions. Risk scenarios where novel plant transgenes transfer horizontally into bacteria have been addressed in numerical theoretical assessments and experimental studies. A key outcome of these studies has been that the frequencies of such inter-domain transfer are very low, if occurring at all, suggesting that such transfers would not occur at a level that is biologically significant. The relationship between transfer frequencies and the subsequent selection or genetic drift of transgene carrying bacteria often remains unresolved in these studies and assessments. Here we present a stochastic model to better understand the initial establishment and population dynamics of rare bacterial transformants carrying horizontally acquired (trans)genes. The following key parameters are considered: initial transformant numbers, strength of selection, bacterial population size and bacterial generations (time). We find that the initial number of transformants is important for the subsequent persistence of transformants only in the range of 1 to ~50 independent HGT events. Our simulations show that transformant populations under a wide range of HGT rates and selection coefficients undergo stochastic developments where they persist at low frequencies for up to several years (at frequencies that are below detection using available field sampling methodology), after which they eventually may go to fixation. Stochastic variability may thus play a crucial but disregarded role in the design of field monitoring strategies e.g. in biosafety assessments. We also estimate the time required for transformants to reach 0.0002% prevalence in a bacterial population, a threshold that allows experimental detection of transgene carrying bacteria through sampling of the larger bacterial populations
Effects of small-scale turbulence on lower trophic levels under different nutrient conditions
12 pages, 4 figures, 1 tableSmall-scale turbulence affects the pelagic food web and energy flow in marine systems and the impact is related to nutrient conditions and the assemblage of organisms present. We generated five levels of turbulence (2*10–9 to 1*10–4 W kg–1) in land-based mesocosms (volume 2.6 m3) with and without additional nutrients (31:16:1 Si:N:P µM) to asses the effect of small-scale turbulence on the lower part of the pelagic food web under different nutrient conditions. The ecological influence of nutrients and small-scale turbulence on lower trophic levels was quantified using multivariate statistics (RDA), where nutrients accounted for 31.8% of the observed biological variation, while 7.2% of the variation was explained by small-scale turbulence and its interaction with nutrients. Chlorophyll a, primary production rates, bacterial production rates and diatom and dinoflagellate abundance were positively correlated to turbulence, regardless of nutrient conditions. Abundance of autotrophic flagellates, total phytoplankton and bacteria were positively correlated to turbulence only when nutrients were added. Impact of small-scale turbulence was related to nutrient conditions, with implications for oligotrophic and eutrophic situations. The effect on community level was also different compared to single species level. Microbial processes drive biogeochemical cycles, and nutrient-controlled effects of small-scale turbulence on such processes are relevant to foresee altered carbon flow in marine systems.Access to installations was funded by the Large-Scale Facility of the University of Bergen and the Improving Human Potential Programme from the European Union through Contract No. HPRI-CT-1999-00056. This study was supported as part of the shared cost research project NTAP (Contract No. EVK3-CT-2000-00022) by the key action "sustainable Marine Ecosystems" of the European Community RTD Programme "Environment and Sustainable Development" and forms part of the ELOISE project cluster.Peer reviewe
Increased importance of cool-water fish at high latitudes emerges from individual-level responses to warming
High latitude ecosystems are experiencing the most rapid warming on earth, expected to trigger a diverse array of ecological responses. Climate warming affects the ecophysiology of fish, and fish close to the cold end of their thermal distribution are expected to increase somatic growth from increased temperatures and a prolonged growth season, which in turn affects maturation schedules, reproduction, and survival, boosting population growth. Accordingly, fish species living in ecosystems close to their northern range edge should increase in relative abundance and importance, and possibly displace cold-water adapted species. We aim to document whether and how population-level effects of warming are mediated by individual-level responses to increased temperatures, shift community structure, and composition in high latitude ecosystems. We studied 11 cool-water adapted perch populations in communities dominated by cold-water adapted species (whitefish, burbot, and charr) to investigate changes in the relative importance of the cool-water perch during the last 30 years of rapid warming in high latitude lakes. In addition, we studied the individual-level responses to warming to clarify the potential mechanisms underlying the population effects. Our long-term series (1991-2020) reveal a marked increase in numerical importance of the cool-water fish species, perch, in ten out of eleven populations, and in most fish communities perch is now dominant. Moreover, we show that climate warming affects population-level processes via direct and indirect temperature effects on individuals. Specifically, the increase in abundance arises from increased recruitment, faster juvenile growth, and ensuing earlier maturation, all boosted by climate warming. The speed and magnitude of the response to warming in these high latitude fish communities strongly suggest that cold-water fish will be displaced by fish adapted to warmer water. Consequently, management should focus on climate adaptation limiting future introductions and invasions of cool-water fish and mitigating harvesting pressure on cold-water fish.Peer reviewe
Effects of small-scale turbulence on lower trophic levels under different nutrient conditions
Small-scale turbulence affects the pelagic food web and energy flow in marine systems and the impact is related to nutrient conditions and the assemblage of organisms present. We generated five levels of turbulence (2*10−9 to 1*10−4 W kg−1) in land-based mesocosms (volume 2.6 m3) with and without additional nutrients (31:16:1 Si:N:P μM) to asses the effect of small-scale turbulence on the lower part of the pelagic food web under different nutrient conditions. The ecological influence of nutrients and small-scale turbulence on lower trophic levels was quantified using multivariate statistics (RDA), where nutrients accounted for 31.8% of the observed biological variation, while 7.2% of the variation was explained by small-scale turbulence and its interaction with nutrients. Chlorophyll a, primary production rates, bacterial production rates and diatom and dinoflagellate abundance were positively correlated to turbulence, regardless of nutrient conditions. Abundance of autotrophic flagellates, total phytoplankton and bacteria were positively correlated to turbulence only when nutrients were added. Impact of small-scale turbulence was related to nutrient conditions, with implications for oligotrophic and eutrophic situations. The effect on community level was also different compared to single species level. Microbial processes drive biogeochemical cycles, and nutrient-controlled effects of small-scale turbulence on such processes are relevant to foresee altered carbon flow in marine systems