Hydrostatic pressure and cellular respiration: are the values observed post-decompression representative of the reality under pressure?

Measuring the biological impact of drilling waste on the deep seafloor: An experimental challenge

The depletion of traditional oil fields is driving the oil & gas industry to explore new exploitation sites previously considered as unprofitable. Deep-sea oil fields represent one of these new areas of exploitation. Well drilling during exploration and production operations generate large quantities of drilling waste whose biological impact on the deep-sea floor remains largely unknown. Because of the harsh abiotic factors characterizing this environment, the evaluation of this impact remains challenging. High hydrostatic pressure is the prominent factor which will affect in-situ biological processes. This review will examine the feedback on the various strategies used to evaluate the biological impact of deep-sea drilling waste deposition as well as the current technological limitations. Given the complexity of this issue, a good perspective strategy would be to trend towards the research and development of more relevant bioassays, especially considering the crucial factor of hydrostatic pressure.

Deep-sea echinoderm oxygen consumption rates and an interclass comparison of metabolic rates in Asteroidea, Crinoidea, Echinoidea, Holothuroidea and Ophiuroidea

Echinoderms are important components of deep-sea communities because of their abundance and the fact that their activities contribute to carbon cycling. Estimating the echinoderm contribution to food webs and carbon cycling is important to our understanding of the functioning of the deep-sea environment and how this may alter in the future as climatic changes take place. Metabolic rate data from deep-sea echinoderm species are, however, scarce. To obtain such data from abyssal echinoderms, a novel in situ respirometer system, the benthic incubation chamber system (BICS), was deployed by remotely operated vehicle (ROV) at depths ranging from 2200 to 3600 m. Oxygen consumption rates were obtained in situ from four species of abyssal echinoderm (Ophiuroidea and Holothuroidea). The design and operation of two versions of BICS are presented here, together with the in situ respirometry measurements. These results were then incorporated into a larger echinoderm metabolic rate data set, which included the metabolic rates of 84 echinoderm species from all five classes (Asteroidea, Crinoidea, Echinoidea, Holothuroidea and Ophiuroidea). The allometric scaling relationships between metabolic rate and body mass derived in this study for each echinoderm class were found to vary. Analysis of the data set indicated no change in echinoderm metabolic rate with depth (by class or phylum). The allometric scaling relationships presented here provide updated information for mass-dependent deep-sea echinoderm metabolic rate for use in ecosystem models, which will contribute to the study of both shallow water and deep-sea ecosystem functioning and biogeochemistry.

In vitro effect of hydrostatic pressure exposure on hydroxyl radical production in fish red muscle

The effects of hydrostatic pressure on reactive oxygen species (ROS) production have been studied in vitro on fish red muscle fibres. In the eel, Anguilla anguilla, previous studies have shown that hydrostatic pressure acclimatization improves oxidative phosphorylation efficiency together with a supposed concomitant decrease in electron leak and ROS production. In order to test the hypothesis of an electron leak decrease under pressure, hydroxyl radical (HO*) production and oxygen consumption were measured on fish red muscle fibres directly exposed to hydrostatic pressure. Experiments were performed under two conditions--atmospheric pressure and hydrostatic pressure (16.1 MPa)--on eel and trout (which exhibit low- and high-pressure sensitivity, respectively). This work has permitted, first, the validation of an indirect HO* measurement (in vitro) on fish red muscle and the documentation of reference values for fish. Second, at atmospheric pressure, results show higher oxygen consumption for trout (+40%) than for eel which is accompanied by higher HO* production (+90%); in addition, both species present a positive relationship between HO* production and oxygen consumption. Hydrostatic pressure exposure reverses this relationship for eel but not for trout. These preliminary results only partially verify the proposed hypothesis and further experiments are needed.

Pressure resistance of aerobic metabolism in eels from different water environments

Eels from different locations were tested comparing their energetic capacities to migrate by studying muscle (red and white) aerobic metabolism. As the migratory activity corresponds to a lengthy swimming activity at depth, their pressure resistance was evaluated by considering fish response to compression, mitochondrial respiration measured under pressure (101 ATA) and cytochrome c oxidase after 3 days under pressure. The results show that only fish from two of the sites have the metabolic capacities to cope with the high pressure encountered during migration.