Some physical factors affecting ecosystems

The response of a simple pelagic ecosystem is investigated in a domain with zero, one- and two-dimensional descriptions of the physical processes. Assuming complete mixing, internal recycling and external exchange of nutrients and their biological products are not additive in terms of the rate of primary production. In a one-dimensional system, advection without diffusion leads to low values of primary production. With two horizontal dimensions, cross diffusion at the boundary gives higher values of production. The consequences for higher trophic levels are described

Constructing end-to-end models using ECOPATH data

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Marine Systems 87 (2011): 227-238, doi:10.1016/j.jmarsys.2011.04.005.The wide availability of ECOPATH data sets provides a valuable resource for the comparative analysis of marine ecosystems. We show how to derive a bottom-up transform from the top-down ECOPATH; couple this to a simple NPZD web with physical forcing; and use the end-to-end model (E2E) for scenario construction. This steady state format also provides a framework and initial conditions for different dynamic simulations. This model can be applied to shelf ecosystems with a wide range of physical forcing, coupled benthic/pelagic food webs, and nutrient recycling. We illustrate the general application and the specific problems by transforming an ECOPATH model for the Northern Californian Current (NCC). We adapt results on the upwelling regime to provide estimates of physical fluxes and use these to show the consequences of different upwelling rates combined with variable retention mechanism for plankton, for the productivity of fish and other top predators; and for the resilience of the ecosystem. Finally we show how the effects of inter-annual to decadal variations in upwelling on fishery yields can be studied using dynamic simulations with different prey-predator relations. The general conclusion is that the nature of the physical regimes for shelf ecosystems cannot be ignored in comparing end-to-end representations of these food webs.This work was supported by the US-GLOBEC Pan-regional Synthesis progra

Fast Sorting of Weyl Sequences Using Comparisons

An algorithm is given which makes only $O(\log n)$ comparisons, and which will determine the ordering of the uniformly distributed (pseudo random) Weyl sequences given by $\{ (k\alpha )\bmod 1:1 \leqq k \leqq n\}$, where $\alpha$ is an unspecified irrational number. This result is shown to be best possible in the sense that no algorithm can perform the same task with fewer than $\Omega (\log n)$ comparisons

Are there eco-metrics for fisheries?

Author Posting. © The Author, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B. V. for personal use, not for redistribution. The definitive version was published in Fisheries Research 77 (2006): 1-3, doi:10.1016/j.fishres.2005.11.003.Ecosystem based management of marine resources is a worthy ideal. At present, however, the science is unable to measure and relate the fundamental concepts of diversity, productivity and resilience required for management decisions. Further, we do not have legal or fiscal measures that would allow us to allocate these resources to reserves, fishing quotas or fish farms. A proper appreciation of these shortcomings is needed

End-to-End Models: Management Applications

Preface to the 2012 issue of Progress in Oceanography

Lack of influence of commonly used drugs on bioassay indicator organisms.

Many commonly used pharmaceutical agents have been found to inhibit bacterial growth in vitro. Determinations of antimicrobial concentrations in sera of patients taking nonrecognized antibacterial agents could possibly be altered if bioassay systems are utilized for the determinations. We therefore attempted to determine the in vitro effect of commonly used drugs on bioassay indicator organisms. Fifty-one different agents (antihistamines, anticholinergics, central nervous system agents, cardiovascular agents, analgesics, steroids, muscle blockers, and other miscellaneous agents) were tested for inhibition or enhancement of the growth of Bacillus subtilis, Staphylococcus aureus, Micrococcus luteus, and Klebsiella pneumoniae. None of the agents tested exhibited any effect on standard in vitro bioassay organisms. Nortriptyline hydrochloride inhibited the growth of B. subtilis and M. luteus at a concentration of 500 micrograms/ml (zones of inhibition, 14 and 13 mm, respectively), but no inhibition was observed with concentrations of 50 micrograms/ml or lower

Effect of human rotavirus vaccine on severe diarrhea in African infants.

BACKGROUND: Rotavirus is the most common cause of severe gastroenteritis among young children worldwide. Data are needed to assess the efficacy of the rotavirus vaccine in African children. METHODS: We conducted a randomized, placebo-controlled, multicenter trial in South Africa (3166 infants; 64.1% of the total) and Malawi (1773 infants; 35.9% of the total) to evaluate the efficacy of a live, oral rotavirus vaccine in preventing severe rotavirus gastroenteritis. Healthy infants were randomly assigned in a 1:1:1 ratio to receive two doses of vaccine (in addition to one dose of placebo) or three doses of vaccine--the pooled vaccine group--or three doses of placebo at 6, 10, and 14 weeks of age. Episodes of gastroenteritis caused by wild-type rotavirus during the first year of life were assessed through active follow-up surveillance and were graded with the use of the Vesikari scale. RESULTS: A total of 4939 infants were enrolled and randomly assigned to one of the three groups; 1647 infants received two doses of the vaccine, 1651 infants received three doses of the vaccine, and 1641 received placebo. Of the 4417 infants included in the per-protocol efficacy analysis, severe rotavirus gastroenteritis occurred in 4.9% of the infants in the placebo group and in 1.9% of those in the pooled vaccine group (vaccine efficacy, 61.2%; 95% confidence interval, 44.0 to 73.2). Vaccine efficacy was lower in Malawi than in South Africa (49.4% vs. 76.9%); however, the number of episodes of severe rotavirus gastroenteritis that were prevented was greater in Malawi than in South Africa (6.7 vs. 4.2 cases prevented per 100 infants vaccinated per year). Efficacy against all-cause severe gastroenteritis was 30.2%. At least one serious adverse event was reported in 9.7% of the infants in the pooled vaccine group and in 11.5% of the infants in the placebo group. CONCLUSIONS: Human rotavirus vaccine significantly reduced the incidence of severe rotavirus gastroenteritis among African infants during the first year of life. (ClinicalTrials.gov number, NCT00241644.

Diffusive vertical heat flux in the Canada Basin of the Arctic Ocean inferred from moored instruments

Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 119 (2014): 496-508, doi:10.1002/2013JC009346.Observational studies have shown that an unprecedented warm anomaly has recently affected the temperature of the Atlantic Water (AW) layer lying at intermediate depth in the Arctic Ocean. Using observations from four profiling moorings, deployed in the interior of the Canada Basin between 2003 and 2011, the upward diffusive vertical heat flux from this layer is quantified. Vertical diffusivity is first estimated from a fine-scale parameterization method based on CTD and velocity profiles. Resulting diffusive vertical heat fluxes from the AW are in the range 0.1–0.2 W m−2 on average. Although large over the period considered, the variations of the AW temperature maximum yields small variations for the temperature gradient and thus the vertical diffusive heat flux. In most areas, variations in upward diffusive vertical heat flux from the AW have only a limited effect on temperature variations of the overlying layer. However, the presence of eddies might be an effective mechanism to enhance vertical heat transfer, although the small number of eddies sampled by the moorings suggest that this mechanism remains limited and intermittent in space and time. Finally, our results suggest that computing diffusive vertical heat flux with a constant vertical diffusivity of ∼2 × 10−6 m2 s−1 provides a reasonable estimate of the upward diffusive heat transfer from the AW layer, although this approximation breaks down in the presence of eddies.C. Lique acknowledge support from JISAO and the Program on Climate Change of the University of Washington. J. Guthrie and J. Morison are supported by National Science Foundation grants ARC-0909408 and ARC-0856330. M. Steele is supported by the Office of Naval Researches Arctic and Global Prediction Program, by NSFs Division of Polar Programs, and by NASAs Cryosphere and Physical Oceanography programs. Support for the BGOS program and R. Krishfield was provided by the National Science Foundation (under grants ARC-0806115, ARC-0631951, ARC-0806306, and ARC-0856531) and Woods Hole Oceanographic Institution internal funding. For A. Proshutinsky, this research is supported by the National Science Foundation Office of Polar Programs, awards ARC-1203720 and ARC-0856531.2014-07-2