Clams after storms: the impact of multiple disturbances on seep vesicomyid clams revealed by long-term monitoring
Cabled seafloor platforms can overcome many constraints of stand-alone systems and archived long-term seafloor monitoring, and their advantages include unlimited power, real-time communication, a synchronized clock, and virtually unlimited data storage. Using monthly images from a fixed camera on a cabled deep-sea observatory in the Off Hatsushima seep site in Sagami Bay, Japan, fluctuations in clam density (Phreagena soyoae and P. okutanii) were observed over 5 years, March 1994–July 1999. Eight disturbances were seen, including five phytodetritus deposition events associated with seasonal blooms, two earthquake-associated turbid flows, and one caused by a maintenance visit by a remotely operated vehicle. Overall, these observations indicate that the vesicomyids experienced an ongoing decline throughout the observation series, and strong disturbance events such as earthquakes appeared to be too severe for the clams to survive. As such, vesicomyid clams are unlikely to survive the foreseeable impacts of deep-sea mining. These results show that long-term observations of deep-sea chemosynthetic communities are useful for understanding their resilience and for making an environmental impact assessment.
The authors thank Hiroshi Morita for his help in image analysis and Takami Nobuhara (Shizuoka University) for helpful discussion. We are greatly indebted to Julia D. Sigwart and Elena M. Krylova for constructive reviews that improved earlier versions of this paper.
This study was supported by the Environmental Research and Technology Development Fund (S9) of the Ministry of the Environment, Japan.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Human and animal rights statement
This article does not contain any studies with human participants performed by any of the authors. The present study is a video image analysis study and thus no live samples of any sort were collected and no experiments were carried out.
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