Trophic interactions among the macrofauna of the deep-sea hydrothermal vents of Alarc acute accent on Rise, Southern Gulf of California

The Alarc ' on Rise (AR) hydrothermal system recently discovered in the Southern Gulf of California is characterized by the presence of black smokers, fluids with temperatures up to 360 degrees C, high concentrations of metalsulfides and H2S. The trophic structure and the energy flow in the vent community were determined through the carbon (813C), nitrogen (815N), and sulfur (834S) isotopic signatures of 19 macrofaunal species. The 813C values had an ample range from -36 and -8%o, reflecting a wide variety of carbon sources and the predominance of organic carbon fixed through the reductive tricarboxylic acid cycle (rTCA). The 815N values varied from -7.9 and 18%o, corresponding to primary and secondary consumers, and the most enriched value (18%o) to a non-vent organism. Dominant organisms included primary consumers such as symbiont-bearing, and bacterivores, which revealed the importance of the bacterial consortium in the energy transfer. Secondary consumers comprised scavengers/detritivores, the most diverse guild, and predators, rather scarce. The 834S values were between -14.5 and 15.6%o, indicating the assimilation of magmatic sulfur in the vent-fauna, and the complementary assimilation of photosynthetically derived organic matter in the non-vent organisms, hinted by their highest value (15.6%o). Interestingly, an unidentified Actiniaria anemone displayed anomalously depleted 813C values (-30.4%o), reflecting a potential symbiotic relationship with sulfur-oxidizing endobacteria.

Automated summary

The recently discovered Alarc'on Rise (AR) hydrothermal system in the Southern Gulf of California is characterized by black smokers, high-temperature fluids, metalsulfides, and H2S. Through isotopic signatures, the study determined the trophic structure and energy flow in the vent community, revealing a wide range of carbon sources, the position of different fauna in the food chain based on nitrogen isotopes, and the assimilation of sulfur in vent fauna and organic matter in non-vent organisms indicated by sulfur isotopes.