Aquatic Sciences Meeting, Albuquerque 2001

SS35 Biological and Ecological Responses to Low Oxygen in Constant and Fluctuating Environments (Spatial and Temporal Connections)

Date: Thursday, February 15, 2001, Time: 10:30:00 AM

Location: La Cienega

Seibel, B, A, Monterey Bay Aquarium Research Institute, Moss Landing, CA, USA, bseibel@rsmas.miami.edu

Hunt, J, C, Japanese Marine Science and Technology Center, Yokosuka, Japan, james@mstip3.jamstec.go.jp

GONATUS ONYX: DIURNAL AND ONTOGENETIC VERTICAL MIGRATION INTO THE OXYGEN MINIMUM LAYER

Gonatus onyx is an active midwater cephalopod (teuthoidea) that undergoes diurnal vertical migrations through the oxygen minimum layer off California. Recent submersible observations of 670 individuals reveal that G. onyx undergoes an ontogenetic descent to great depths as well, where spawning and egg-brooding are believed to occur. Glycolytic enzymatic activities are reduced in adult animals suggesting that burst swimming capacity is limited. This is consistent with the visual interactions hypothesis, which states that visually-orienting pelagic animals have reduced metabolic rates and locomotory abilities relative to shallower species (or life history stages) due to relaxed selection for strong locomotory abilities for visual predator-prey interactions in the light-limited deep-sea. Both juveniles and adults are capable of regulating their oxygen consumption down to 30 mm Hg, an oxygen concentration consistent with the minimum experienced at their day- and night-time habitat depths, respectively. Therefore, juveniles appear to fuel their routine metabolism aerobically at all depths while adults must rely on either metabolic suppression and/or anaerobic glycolysis to augment their metabolism at their deeper daytime depths. Preliminary measurements on board ship revealed anaerobic survival greater than 6 hours in adult G. onyx (juveniles were not tested). In situ behavioral observations from a remotely operated vehicle support the assertion that activity and, perhaps, metabolism are suppressed during daytime forays into the oxygen minimum layer.

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Aquatic Sciences Meeting, Albuquerque 2001

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