Influences of geothermal sulfur bacteria on a tropical coastal food web

Abstract

The activity of the geothermal plant at Bouillante in Guadeloupe (French West Indies) releases thioautotrophic bacteria into the coastal environment. Fish counts reveal that fish abundance increases with higher availability of this bacterial resource. In order to evaluate the trophic role of these bacteria, isotopic compositions (C, N, S) of potential consumers were evaluated on transects at increasing distance from the source of bacteria. The 3 mobile fish species examined (Abudefduf saxatilis, Acanthurus bahianus, and Stegastes partitus) ingested and assimilated chemosynthetic bacteria. Similarly, the isotopic composition of the mobile sea urchin Diadema antillarum was different close to the discharge channel, suggesting a diet mainly composed of sulfur bacteria. In contrast, endofauna sampled from the nematode community did not show a diet influence by chemosynthetic bacteria. A broad variety of epifaunal organisms with passive and active suspension-feeding activities were also investigated, including sponges (Aplysina fistularis and Iotrochota birotulata), barnacles (Balanus sp.), bivalve molluscs (Spondylus tenuis) and cnidarians (Pseudopterogorgia sp.), but no strong evidence for sulfur bacteria contributions were determined in the diets of any of these organisms. This was also true for the omnivorous predator annelid Hermodice carunculata. In this coastal oligotrophic environment, only certain opportunistic species seem to benefit from the emergence of a new food item such as chemosynthetic bacteria.

Hydrothermal sulphur bacteria enhance mercury availability for coastal marine organisms

“…cyanobacteria (Oscillatoriaceae) associated with the sulphur-oxidising Thiomicrospira sp . gammaproteobacteria (Pascal et al, 2017). Associations between Oscillatoriaceae and sulphur-oxidising bacteria were already reported in mats over sulphur-rich sediments (Stolz, 1985; Mir et al, 1991; Guézennec et al, 2011) since bacteria benefits from the O 2 released by the cyanobacteria.…”

“…Associations between Oscillatoriaceae and sulphur-oxidising bacteria were already reported in mats over sulphur-rich sediments (Stolz, 1985; Mir et al, 1991; Guézennec et al, 2011) since bacteria benefits from the O 2 released by the cyanobacteria. The development of Thiomicrospira in the discharge channel is clearly linked with the Bouillante plant activity, since this obligate sulphur-oxidising bacteria (Takai et al, 2004) quickly disappears when discharge waters stop flowing during maintenance work, cutting off the abundant sulphur supply (Pascal et al, 2017).…”

“…Interestingly, A. bahianus showed the lowest and the highest Hg concentrations in the muscle and the liver, respectively, likely because its benthivorous/periphytophagous diet favours the ingestion of inorganic forms of Hg (48% to 72% of Hg in their food) that preferentially accumulates in the liver and kidneys (Maury-Brachet et al, 2006). On the contrary, the planktivorous A. saxatilis , which has a higher trophic level (δ 15 N = 5.70 ± 0.31‰) than A. bahianus (δ 15 N = 4.89 ± 0.10‰; Pascal et al, 2017), likely contains more MeHg, since concentrations in its muscle and liver are similar (Scheuhammer et al, 2015). The comparison with other probable Hg-poor sites reveals similar tendencies for fishes’ liver and muscle ( Table 1 ) indicating a classical accumulation of Hg in the tissue of these fishes, with differences between species probably explained by their different diet.…”

“…The thick mat (6-7mm) is made of benthic cyanobacteria, identified as Plectonema sp ., covered with white filamentous bacteria of the genus Thiomicrospira (Pascal et al, 2017). These chemosynthetic bacteria use sulphur compounds (e.g.…”

Ontogenetic resource utilization and migration reconstruction with δ13C values of essential amino acids in the Cynoscion acoupa otolith

“…Numbers under the triangles represent standard length in cm for each individual from which the otolith was obtained To gain a complete insight into the contribution of primary producers to estuarine and offshore fish food webs, all possible primary producers should be collected in the immediate environment and migration area of the species. This would also include the contribution of bacteria and fungi, which have been indicated to play an important role in the diet of first trophic-level consumers (Pascal, Dubois, Goffette, & Lepoint, 2017;Steffan et al, 2017;Yi et al, 2017). Due to time and funding constraints, such samples were not included in the current study, but future studies could take full advantage of the source diagnostic ability of δ 13 C EAA patterns to distinguish among algal-, bacterial-, fungal-, and plant-derived EAA sources (Larsen et al, 2013).…”