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Contributed Talk

Session: : Behavior: Foraging And Diet 1

COS 3-2 - Differential foraging adaptations of benthic macrofauna in response to severe biogeochemical disturbance following extreme events

Monday, August 7, 2023
1:45 PM – 2:00 PM PDT
Location: B112
Abstract: Hydrothermal vent systems are crucial for biodiversity, hosting a wide range of unique species and providing insights into how life adapts to extreme environments. These habitats, however, face threats from human activities and extreme natural events, both of which can quickly disrupt the delicate food webs present in these systems. This is particularly true for shallow vent-endemic animals, which have limited dietary niches and specialized adaptations to specific biogeochemical conditions. To investigate how a benthic food web responds to disturbances, we studied the shallow hydrothermal vents of Kueishantao off the coast of Taiwan. We focused on the effect of a consecutive M5.8 earthquake and C5 typhoon in 2016, which led to a two-year "near shutdown" of active vents. Our study aimed to understand how these events altered the local biogeochemical cycle and the availability of photosynthetic versus chemosynthetic food resources.

Our analysis of stable isotopes (δ34S, δ13C, and δ15N) from different benthic macrofauna species showed that endemic and non-endemic consumers responded differently to the sudden disruption of their habitat and biogeochemical cycling. The endemic vent crab, Xenograpsus testudinatus, continued to rely on chemosynthetic sulfur bacteria, despite photosynthetic sources being the most dominant food source after the perturbation. We suggest that X. testudinatus has an obligate nutritional dependence on chemoautotrophic sources, as the decrease in chemoautotrophic production was accompanied by a significant decrease in X. testudinatus abundance. The population decline rate increased from ~19 individuals per m2 per year before the perturbation to 40 individuals per m2 per year after the perturbation. On the other hand, non-endemic gastropods displayed much greater dietary flexibility, which tracked the overall abundance of photo- and chemosynthetic dietary sources. The catastrophic events in shallow hydrothermal vent ecosystems presented a unique opportunity to examine dietary adaptations among endemic and non-endemic benthic macrofauna in response to altered biogeochemical cycling. Our findings underscore the vulnerability of benthic specialists to the mounting environmental pressures exerted worldwide by human activities.