Meeting Abstracts chaetognatha and cnidaria chaetognatha and cnidaria Return to Thuesen Homepage

We gave three presentations at the Pacific Estuarine Research Society Annual Meeting in Portland, Oregon in May, 2002.

Ecophysiology of gelatinous zooplankton in estuarine hypoxia

Erik V. Thuesen

Gelatinous zooplankton can form rapid population blooms since they invest a relatively small amount of energy into growth relative to the energy content of their prey. Recent work by several researchers has shown that "jellyfish blooms" may be promoted by hypoxia potentially leading to ecosystems dominated adaptations of gelatinous zooplankton in southern Puget Sound in order to determine the effects of low oxygen on these ecologically important zooplankters. Our study organisms include ctenophores, scyphomedusae, hydromedusae, and siphonophores. We have found that several species can oxyregulate to less than 10% oxygen saturation, as well as survive at 0% oxygen for over several hours. Our intra-gel oxygen measurements on the ctenophore Pleurobrachia bachei have shown that facilitated diffusion is the likely mechanism allowing these animals to oxyregulate at low oxygen partial pressures. Our results indicate that estuarine gelatinous organisms are better at withstanding hypoxia than many of their pelagic competitors and prey.

Physiological adaptations and behavioral responses of gelatinous zooplankton to estuarine hypoxia

Gabrielle Kirouac, Heather Wiedenhoft, Patrica L. Brommer, Ladd D. Rutherford, Jr., and Erik V. Thuesen

Recent investigations have proposed a relationship between jellyfish blooms and hypoxia. Gelatinous zooplankton are known to vertically migrate through areas of low oxygen , giving them a potential advantage over their zooplankton prey (Breitburg et al., 2000). The physiological mechanisms that allow gelatinous organisms to succeed in low oxygen environments remain unclear. To investigate the hypothesis that gelatinous zooplankton survive aerobically in hypoxic waters, we measured the critical partial pressure (Pc, the point at which oxygen consumption is no longer regulated) of five species of gelatinous zooplankters . To investigate the hypothesis that gelatinous zooplankton prefer hypoxic waters, we created an artificial environment which mimics oxygen stratification in the southern Puget Sound. Hypoxic water is pumped into the bottom of a one meter cylindrical tank containing oxygen saturated water to create an oxygen stratified system. A similar tank with no oxygen stratification is used as a control. Organisms are placed in the tanks and observed over time for behavioral comparisons. Understanding the extent to which gelatinous zooplankton make use of the hypoxic niche may suggest which species will thrive as environmental conditions change over time.

Heat shock proteins induced by oxygen stress in the jellyfish Aurelia labiata

Jessica A. Archer, Anna Brownstein, Magdalena A. Gutowska, Amanda L. Robbins, Andrew Brabban and Erik V. Thuesen

Oxygen depletion, which is seasonally common in bottom waters of many stratified estuarine systems, may have an enormous effect on the abundance diversity, and interactions of marine organisms that inhabit these ecosystems. There is evidence that gelatinous zooplankton, such as Aurelia labiata, may thrive in hypoxic conditions. Due to their ability to migrate through the water column, A. labiata can have a profound effect on populations and diversity of other organisms in a low oxygen ecosystem. The molecular mechanisms behind their survival in these low oxygen waters are poorly understood. The current hypothesis is that they are either: 1) activating their anaerobic machinery, or 2) go into metabolic arrest. There has been significant research in recent years on the use of heat shock proteins as a mechanism for coping with various environmental stresses. We are exploring the hypothesis that A. labiata expresses hsp70 bat low oxygen tensions and determining the oxygen concentration at which these proteins are expressed in order to determine the potential use of these proteins as an indicator for oxygen induced environmental stress.

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