Ecophysiological studies of Orchomenopsis affinis (Holmes) (Lysianassidae Amphipoda) in an intermittently anoxic fjord
Date
1989
Authors
Liu, Quanshun
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Abstract
This study was undertaken in order to understand the physiological adaptations and ecology of Orchomenopsis affinis (Holmes) (Lysianassidae, Amphipoda) in Saanich Inlet, an intermittently anoxic fjord on Vancouver Island, British Columbia, Canada. Field sampling, submersible observation and laboratory experiments were carried out from November, 1985 to April, 1987.
O. affinis was found in abundance under oxygen deficient conditions, especially in the anoxic and sulfide-rich layer. O. affinis can survive under anoxic conditions for at least 25 hours and tolerate concentrations of sulfide up to 3 mM. The survival of O. affinis to temperature and salinity changes are Oto 19 °c and 20 to 50 °/oo respectively.
O. affinis shows respiratory independence under the oxygen range from 0.5 to 10.0 mg/1. Respiratory dependence occurs when oxygen concentration is lower than 0.5 mg/1. Respiratory rates are lowest under low temperature and high salinity.
The vertical distribution of O. affinis indicates that more than 70 % of the population is associated with the sediment-water interface during the day and about 15 % of the population clings to the s e a floor at night.
Animals migrate vertically to oxygen rich layers to eliminate the oxygen debt which accumulates under anoxic conditions.
O. affinis feeds by scavenging on or in the sediment beneath the anoxic water layer. Because of its obligatory vertical migration, it has the ecological role of transporting energy to the oxygenated layer, thereby establishing a unique food chain. This phenomenon is named Biological Upwelling.
The advantages to O. affinis in occupying the anoxic zone are: (1) greater availability of food, (2) refuge from predation, and (3) energy conservation through relatively lower metabolic rates in deep and colder water.
Though our knowledge of ecophysiological adaptations and ecological significance has increased, biochemical adaptation of this animal to sulfide and its metabolic pathways under aerobic and anaerobic conditions remain
unknown.
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UN SDG 14: Life Below Water