Benthic ecosystem functioning of the western Clarion-Clipperton Zone, Pacific Ocean, and the West Antarctic Peninsula : a study to assess the effectiveness of Areas of Particular Environmental Interest (APEIs) in the context of deep-sea mining and the effects of climate change

Abstract

The deep sea encompasses the largest ecosystem on Earth and remains largely unexplored. With plans for deep-sea mining and the increasing impacts of climate change on our oceans, there is a growing necessity to understand and safeguard deep-sea biodiversity and ecosystem functioning. The cycling of carbon (C) by deep-sea benthic communities is a key ecosystem function and pulse-chase experiments are aimed to measure this process I conducted pulse-chase experiments in situ at abyssal depths (4800-5300 m) in three no-mining areas, called Areas of Particular Environmental Interest (APEIs), in the Clarion-Clipperton Zone (CCZ) and in ex situ experiments using sediments collected from a bathyal (500-600 m) fjord, Andvord Bay, and the continental shelf of the West Antarctic Peninsula (WAP). My results underline the importance of organic C in driving ecosystem dynamics at the abyssal seafloor and support the notion that Antarctic fjords are hotspots of benthic biomass and ecosystem functions. The microbial community was shown to be a key player in the short term (1.5 d) cycling of C on the abyssal plain of the western equatorial Pacific Ocean, which is consistent with other published studies, while the macrofaunal community (>300 µm) dominated the initial (~1 d) degradation of phytodetritus in Andvord Bay. My study provides important information on benthic ecosystem functioning in the western CCZ, an area targeted for commercial-scale deep-sea mining, and the WAP, a region that is becoming increasingly impacted by climate change.