In situ measurement of oxygen in aquatic egg masses field tests of theoretical models


Meeting Abstract

28.2  Friday, Jan. 4  In situ measurement of oxygen in aquatic egg masses: field tests of theoretical models MORAN, A.L.**; WOODS, H.A.; Clemson Univ.; Univ. of Montana, Missoula moran@clemson.edu

Aquatic, gelatinous egg masses occur in a wide range of organisms, and physiological models of oxygen demand (by embryos within masses) and oxygen supply (by diffusion) show that low oxygen can limit development and survival of embryos in masses. In the lab, structural factors such as mass thickness and density of embryos have been shown to affect the degree of O2 limitation. In the field, O2 gradients are likely also affected by numerous factors including boundary layers, temperature fluctuations, location, and substrate. We used an underwater picoammeter equipped with a 50-μm oxygen electrode to take what we believe are the first in situ measurements of oxygen gradients in invertebrate egg masses. In the field, internal O2 levels of natural masses were as low as 20% of ambient. We also made artificial egg masses and deployed them subtidally for 24 hours, after which we measured internal O2 in situ, returned masses to the lab and measured O2 gradients in both still and air-bubbled water. In the field, internal O2 was comparable to air-bubbled laboratory conditions, suggesting that the zero-boundary-layer condition assumed by most models is reasonable. We will also discuss field measurements of O2 levels in egg masses in the Southern Ocean (to be performed in fall 2007); previous laboratory work suggests that constant extreme cold and high O2 leads to high oxygenation of masses relative to temperate systems.

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