Search

Your search keyword '"Essington, T. E."' showing total 14 results
Start Over Author "Essington, T. E."
14 results on '"Essington, T. E."'

5. The global contribution of forage fish to marine fisheries and ecosystems

Author

Pikitch, E. K., Rountos, K. J., Essington, T. E., Santora, C., Pauly, D., Watson, R., Sumaila, U. R., Boersma, P. D., Boyd, I. L., Conover, D. O., Cury, Philippe, Heppell, S. S., Houde, E. D., Mangel, M., Plaganyi, E., Sainsbury, K., Steneck, R. S., Geers, T. M., Gownaris, N., and Munch, S. B.

Subjects
fish, ecosystem-based management, trade-offs, Ecosystem service, forage, supportive values, fisheries value
Abstract

Forage fish play a pivotal role in marine ecosystems and economies worldwide by sustaining many predators and fisheries directly and indirectly. We estimate global forage fish contributions to marine ecosystems through a synthesis of 72 published Ecopath models from around the world. Three distinct contributions of forage fish were examined: (i) the ecological support service of forage fish to predators in marine ecosystems, (ii) the total catch and value of forage fisheries and (iii) the support service of forage fish to the catch and value of other commercially targeted predators. Forage fish use and value varied and exhibited patterns across latitudes and ecosystem types. Forage fish supported many kinds of predators, including fish, seabirds, marine mammals and squid. Overall, forage fish contribute a total of about $16.9 billion USD to global fisheries values annually, i.e. 20% of the global ex-vessel catch values of all marine fisheries combined. While the global catch value of forage fisheries was $5.6 billion, fisheries supported by forage fish were more than twice as valuable ($11.3 billion). These estimates provide important information for evaluating the trade-offs of various uses of forage fish across ecosystem types, latitudes and globally. We did not estimate a monetary value for supportive contributions of forage fish to recreational fisheries or to uses unrelated to fisheries, and thus the estimates of economic value reported herein understate the global value of forage fishes.

Published
2014

7. Disrupted seasonal clockwork in the population dynamics of a freshwater copepod by climate warming

Author

Winder, Monika, Schindler, D. E., Essington, T. E., Litt, A. H., Winder, Monika, Schindler, D. E., Essington, T. E., and Litt, A. H.

Abstract

Life history responses are expected to accompany climate warming, yet little is known how long-term effects of climate and environmental change affect the seasonal dynamics of planktonic organisms. We used an historical data set from Lake Washington (U.S.A.) to quantify population responses of a calanoid copepod (Leptodiaptomus ashlandi) to long-term changes in temperature and resource availability and explore potential mechanisms for the responses. Increasing water temperatures (annual mean increase of 1.5 degrees C in the upper 10-m water volume) and longer stratification periods (about 4 weeks) were observed between 1962 and 2005, coincident with a pronounced decline in Leptodiaptomus densities. However, production was maintained because of an increase in the production to biomass ratio and a life cycle shift in Leptodiaptomus from an annual to a 6-month cycle. Cross-wavelet analyses demonstrated that the annual thermal forcing of copepod recruitment observed during the first two decades of the study weakened substantially, leading to more stochastic population dynamics during the past two decades. This shift from one to two generations per year was most likely produced by a longer and warmer growing period combined with changing fluctuations in resource (phytoplankton) availability. Climate change can lead to higher-frequency voltinism in ectothermic organisms and to temporal reorganization of their population dynamics.

Published
2009
Full Text
View/download PDF

14. Sphingosine metabolism induces Ca2+ oscillations in rat pancreatic acinar cells.

Author

Yule DI, Wu D, Essington TE, Shayman JA, and Williams JA

Subjects
Animals, Cholecystokinin pharmacology, Estrenes pharmacology, Fluorescent Dyes, Fura-2 analogs & derivatives, In Vitro Techniques, Inositol 1,4,5-Trisphosphate metabolism, Kinetics, Male, Oscillometry, Phosphatidylinositols metabolism, Pyrrolidinones pharmacology, Rats, Rats, Sprague-Dawley, Time Factors, Type C Phospholipases antagonists & inhibitors, Calcium metabolism, Inositol Phosphates metabolism, Pancreas metabolism, Sphingosine metabolism, Sphingosine pharmacology
Abstract

The possibility that sphingosine or a related metabolite could mediate inositol-1,4,5-triphosphate (1,4,5-IP3)-independent Ca2+ release in pancreatic acinar cells was investigated. In intact rat pancreatic acini superfused at 37 degrees C, sphingosine (10-100 microM) evoked, after a delay of several minutes, an increase in the cytosolic [Ca2+]i which was oscillatory below concentrations of 50 microM. At room temperature no increase in [Ca2+]i was observed. The increase in [Ca2+]i evoked by sphingosine was not inhibited by U73122, and thus was unlikely to be due to phosphatidylinositol (PI) hydrolysis. Furthermore, no PI hydrolysis or 1,4,5-IP3 production was detected on incubation with sphingosine. As metabolism of sphingosine could explain the temperature-dependent action, the effects of sphingosine and related sphingoid bases were tested in permeabilized cells. After a delay of 30 s at 37 degrees C, sphingosine evoked a slow increase in [Ca2+] into the medium. In contrast, addition of sphingosylphosphorylcholine (SPC) resulted in a rapid increase in [Ca2+]. This response was mimicked by 1,4,5-IP3 but not by addition of sphingosine phosphate (1-10 microM), ceramide (30 microM), or sphingomyelin (50 micrograms/ml). SPC appeared to induce release of Ca2+ from the same store as 1,4,5-IP3, as SPC failed to evoke any further increase in Ca2+ from cells previously depleted by addition of a maximal concentration of 2,4,5-IP3 or thapsigargin. 1,4,5-IP3 but not SPC-induced Ca2+ release was blocked by heparin, indicating that SPC-induced Ca2+ release was not mediated through the IP3 receptor-channel complex. This study demonstrates that SPC, a sphingosine metabolite, could be responsible for IP3-independent Ca2+ oscillations previously seen in pancreatic acinar cells.

Published
1993

Catalog

Books, media, physical & digital resources
See catalog results