High-resolution dynamics of a deep-sea hydrothermal mussel assemblage monitored by the EMSO-Açores MoMAR observatory

Abstract

Although the spatial distribution of hydrothermal vent assemblages in relation to environmental conditions has been assessed in several studies, there is little documented data on the temporal variation of the fauna and corresponding abiotic factors in a vent community. Here, we present one of the longest integrated (faunal and environmental data) time series ever obtained in a hydrothermal ecosystem. The data were acquired using the TEMPO ecological module that was deployed between 2006 and 2008 on the Mid-Atlantic Ridge, providing the first insights into the day-today variations in a Bathymodiolus azoricus mussel assemblage from the Lucky Strike vent field for the 48 days during which the video camera operated. The time-series yielded additional valuable information on longerterm variation in faunal distribution (comparing∼2 years), temperature (11.7 months) and iron concentrations (3.8 months). Results from daily observations showed that the vent mussel assemblage was quite stable over the 48 days of the study, reflecting the relative stability of environmental conditions during this period. Bathymodiolus azoricus mussels appeared to thrive in areas of very limited hydrothermal fluid input in habitats that are, as in other deep-sea ecosystems, significantly influenced by ocean tidal signals. Variation in species abundance was observed but, with the exception of Mirocaris fortunata shrimp, no links could be established with measured environmental variables. Although we did not observe any clear tidal influence on vent fauna, it is likely that physiological processes and species' activities are influenced by these periodic variations. Longer time series are currently being acquired by different experiments deployed on the EMSO-Açores MoMAR observatory (2010-2013 and still recording). They should further improve our knowledge of the dynamics of hydrothermal systems and their associated faunal communities. Highlights ► Relative stability of the vent mussel assemblage in relation with abiotic conditions. ► Hydrothermal habitats significantly influenced by ocean tidal signals. ► Temporal variations in species abundance observed. ► No established links between faunal abundance (except for shrimp) and environmental variables. ► Direct species interactions not frequently observed.

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

“…The biggest discrepancy between both modules was the energy provision, with the Atlantic one (TEMPO) being autonomous and battery dependent (wireless) and the NEP one (TEMPOmini) being connected to a cabled network. Detailed descriptions of both modules can be found in Sarrazin et al (2007Sarrazin et al ( , 2014 for TEMPO and Auffret et al (2009) and for TEMPO-mini. Henceforth, the Atlantic set-up (TEMPO on MoMAR/EMSO-Azores) will be referred to as MAR and the Pacific set-up (TEMPO-mini on NEPTUNE/ONC) set-up as NEP (Fig. 1).…”

“…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.…”

Trends in microfluidic systems for in situ chemical analysis of natural waters

“…Small sized peristaltic pumps are easily commercially sourced, relatively cheap and easy to M a n u s c r i p t use and consequently have proved consistently popular. [25,26,[28][29][30][32][33][34][35]37,[39][40][41][42][43] Nonetheless, peristaltic pumps can suffer from drifting flow rates due to variation in the elasticity and plasticity of the pump tubing with changes in temperatures [35] and, crucially, are relatively power hungry. [56] Consequently, reported deployments of peristaltic pumped sensors have been limited to a day or less, except where power could be externally supplied via cabling.…”

“…[56] Consequently, reported deployments of peristaltic pumped sensors have been limited to a day or less, except where power could be externally supplied via cabling. [42,43] In 1994, osmotic pumping was suggested as a solution to reduce power consumption and boost operational longevity. As illustrated in Fig 2b, osmotic pumps utilise the osmotic pressure difference between low and high-salinity reservoirs within the sensor to passively drive very slow flows (typically single µL/hour).…”

“…[48][49][50] Of these, colorimetry -in which the sample is mixed with an analyte-specific reagent to produce a measurable colour -has proved to be by far the most popular method and has been used for in situ analysis of a range of chemical parameters including nitrate and nitrite, [21,22,24,29,31,34,35,38] phosphate, [27,38] iron, [23,26,28,36,39,[42][43][44] manganese, [25,26,28,37,40] sulfide [32,33,35,39,41] silicate [30,32,33,38] and pH. [51][52][53][54][55] Colorimetry lends itself well to microfluidic in situ analysers as it is chemically robust, offers excellent analytical performance (limits of detection typically in the order of 10 nM [21,25,36]) and requires relatively small, cheap and easily-sourced components.…”