Soundscape Tool Could Help Assess Anthropogenic Impacts on Deep Seabed

Mining the deep seabed for resources has been a growing topic of interest among countries and industries around the globe, correlated with a rising global demand for minerals and rare-earth elements. However, targets for deep-sea mining typically coincide with biological ‘hotspots’ where vibrant and unique lifeforms flourish, such as hydrothermal vents producing massive sulfide deposits and seamounts with metal-rich crusts. Assessing and monitoring the anthropogenic impacts of mining to these hotspots and their resilience is a key topic where urgent development is needed, in order to prevent irreversible damage to unique ecosystems which we still understand very little about.

 

Animals inhabiting the seafloor maintain their distribution through the process of larval dispersal where the egg or larvae of bottom-dwelling species travel in the water column and eventually settle in suitable habitats, potentially hundreds of kilometers away. In the recent years, compelling evidence has been compiled to show that larvae of shallow water animals often use soundscape, the collective sounds characteristic of a habitat, to orient and settle in their preferred (adult) environment, for example tropical coral reefs.

A research group co-led by Tzu-Hao Lin of the Marine Biodiversity and Environmental Assessment Research Center (BioEnv) of the Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and Chong Chen of SUGAR Program, X-STAR, JAMSTEC has proposed that larva of animals endemic to deep-sea hotspots likely also use similar mechanisms to find their habitats, and that anthropogenic noise generated by mining will likely disrupt this and thereby reduce the connectivity and resilience among nearby ecosystems. For example, hydrothermal vents generate natural geophony and biophony totaling about 10-50dB above the background level, but anthropogenic sounds generated by mining activities in the deep-sea is approximated to be well above this (approx. 100dB above background) and masks the natural soundscape.

Understanding and monitoring soundscapes at deep-sea hotspots may therefore provide an important index to measure mining impacts in the deep. While the Global Ocean Observing System has listed ocean sound one of the essential ocean variables, currently proposed environmental assessment criteria for deep-sea mining makes no mention of ocean sound monitoring. The International Seabed Authority (ISA) is finalizing the ‘Mining Code’ which will apply to all seabed development activities in international waters, which currently does not include sound monitoring. As such, the research group urges for a global collaborative effort in using soundscape as a new deep-sea conservation tool, and an increased effort in studying the interaction between deep-sea larvae and soundscapes. The research group believes this new monitoring tool will have significant contributions to the formation of new environmental guidelines governing the sustainable use of oceanic resources.

The paper was published in the journal Trends in Ecology & Evolution on November 8th, 2019 (JST).

Title: Using soundscapes to assess deep-sea benthic ecosystems Authors: Tzu-Hao Lin1*, Chong Chen2*, Hiromi Kayama Watanabe2, Shinsuke Kawagucci2, Hiroyuki Yamamoto1, Tomonari Akamatsu3 Affiliations: 1. BioEnv, RIGC, JAMSTEC; 2. X-STAR, JAMSTEC; 3. National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency *These authors contributed equally to this study.