Deep-sea hydrothermal vent animals seek cool fluids in a highly variable thermal environment

Abstract

The thermal characteristics of an organism ' s environment affect a multitude of parameters, from biochemical to evolutionary processes. Hydrothermal vents on mid-ocean ridges are created when warm hydrothermal fl uids are ejected from the seafl oor and mixed with cold bottom seawater; many animals thrive along these steep temperature and chemical gradients. Twodimensional temperature maps at vent sites have demonstrated order of magnitude thermal changes over centimetre distances and at time intervals from minutes to hours. To investigate whether animals adapt to this extreme level of environmental variability, we examined differences in the thermal behaviour of mobile invertebrates from aquatic habitats that vary in thermal regime. Vent animals were highly responsive to heat and preferred much cooler fl uids than their upper thermal limits, whereas invertebrates from other aquatic environments risked exposure to warmer temperatures. Avoidance of temperatures well within their tolerated range may allow vent animals to maintain a safety margin against rapid temperature fl uctuations and concomitant toxicity of hydrothermal fl uids.

Temporal and spatial variation in temperature experienced by macrofauna at Main Endeavour hydrothermal vent field

“…The preferred temperature of the gastropods is in the range of 5-13 C based on experiments in pressurized aquaria (Bates et al, 2010), and similar preferences have been observed in in situ experiments (Bates et al, 2005 compared with the gastropods (Bates et al, 2010). While it appears that the palm worms were in areas much cooler than their preferred temperature, we cannot rule out that they aren't aggregated around small jets of warm water that would not have been resolved by our mapping.…”

“…This spike consisted of a rise over 20 hours followed by a decline over the subsequent 200 hours. Maximum temperatures in the arrays went up to 45C which is above the thermal maximum of several of the animal species observed in deployment images (Bates et al, 2010). Across the arrays, the average temperature warmed by 2 C, and 25% of the average increase could be attributed to a single logger.…”

“…An understanding of temperature niches is emerging from studies that map faunal distribution in relation to temperature, in combination with experimental studies of thermal tolerance. Under controlled conditions, vent animals exhibit behaviors demonstrating thermal preferences and upper thermal tolerance limits (Bates et al, 2010;Lee, 2003;Shillito, 2006). Some recent studies have combined faunal maps with physical and chemical mapping using geographic information systems (Podowski et al, 2009).…”

“…Thermal tolerance differences between species, observed in pressurized aquarium studies (e.g. Bates et al, 2010;Lee, 2003;Shillito, 2006), appear to correlate with distributions in nature. Vent animals also exhibit behavioral and locomotory responses to temperature (Bates et al, 2013).…”

“…Bates et al (2010) showed that selected temperature correlated with critical thermal maximum, with species that have a higher thermal maximum selecting higher temperatures. They postulated that vent animals were "playing it safe" by selecting lower temperatures than non-vent animals as a response to a stochastic thermal environment (Bates et al, 2010). But, at the spatial and time scales of measurements in this study, lethal temperatures were generally not detected.…”