Astronomical and atmospheric impacts on deep-sea hydrothermal vent invertebrates

Abstract

Ocean tides and winter surface storms are among the main factors driving the dynamics and spatial structure of marine coastal species, but the understanding of their impact on deep-sea and hydrothermal vent communities is still limited. Multidisciplinary deep-sea observatories offer an essential tool to study behavioural rhythms and interactions between hydrothermal community dynamics and environmental fluctuations. Here, we investigated whether species associated with a tubeworm vent assemblage respond to local ocean dynamics. By tracking variations in vent macrofaunal abundance at different temporal scales, we provide the first evidence that tides and winter surface storms influence the distribution patterns of mobile and non-symbiotic hydrothermal species (i.e. pycnogonids sp. and Polynoidae polychaetes) at more than 2 km depth. Local ocean dynamics affected the mixing between hydrothermal fluid inputs and surrounding seawater, modifying the environmental conditions in vent habitats. We suggest that hydrothermal species respond to these habitat modifications by adjusting their behaviour to ensure optimal living conditions. This behaviour may reflect a specific adaptation of vent species to their highly variable habitat.

Biological and environmental rhythms in (dark) deep-sea hydrothermal ecosystems

“…For both taxa, the multiple-day periodicities approached those visible in Fe, i.e. 4.5 and 7.5 days (though non-significant), and besides an apparent preference for lower temperatures there were no significant links with temperature (as corroborated by Lelièvre et al (2017) for the polynoids). Additional high-resolution investigations will be necessary to corroborate or validate these observations.…”

“…These horizontal bottom currents showed 12.4 h tidal periodicity which was also found in the temperature time series of the aforementioned article as well as in our NEP temperature time series. Consistent with the main orientation of the ridge and the topography of Grotto, temperature and oxygen saturation at the NEP deployment site were shown to be strongly and significantly influenced by the northern and southern horizontal bottom tidal currents (along the valley axis) (Lelièvre et al, 2017). Patterns in temperature variation of the MAR time series corresponded to the tidal signal observed in the Lucky Strike vent field at 25 h and to the semi-diurnal tidal oscillation at 12:30 h (Khripounoff et al, 2000(Khripounoff et al, , 2008.…”

“…A large difference in pycnogonid densities (ind m −2 ) was observed between the two sites as well, with a ratio of 1/250 MAR vs. NEP. Increased activity and aggregations of more than five individuals (and increased intra-species contact) at NEP were linked to conditions of high-temperaturelow-oxygen saturation (Lelièvre et al, 2017). Interestingly, these organisms all belong to the same genus, namely Sericosura.…”

“…Several studies reveal the presence of tidal cycles in environmental variables (such as currents, fluid emission, temperature) in the deep sea, particularly in hydrothermal vents (e.g. Tivey et al, 2002;Thomsen et al, 2012;Barreyre et al, 2014;Sarrazin et al, 2014;Lelièvre et al, 2017) and the influence of tides on the deepsea organisms has been previously inferred. Additionally, an actual tidal rhythm has been revealed in visible faunal densities and appearance rate for inhabitants of various deepsea chemosynthetic environments -e.g.…”

“…First ecological analyses based on deepsea observatories have been published (Juniper et al, 2013; Published by Copernicus Publications on behalf of the European Geosciences Union. 2956 D. Cuvelier et al: Biological and environmental rhythms Matabos et al, 2014Matabos et al, , 2015Cuvelier et al, 2014;Lelièvre et al, 2017), and many more works are in progress.…”