Effect of a physical disturbance event on deep-sea nematode community structure and ecosystem function

Abstract

Numerous studies have been conducted on the effect of physical disturbance on shallow water benthic communities, but there is a paucity of data from deep-sea environments. We conducted a laboratory experiment using undisturbed sediment cores from Chatham Rise (water depth =345 m), Southwest Pacific, to investigate the effects of a physical disturbance event (resuspension of surface sediments) on sediment characteristics (sediment grain size, pigment content), nematode community attributes (abundance, diversity, community structure) and ecosystem function (sediment community oxygen consumption (SCOC)) over a period of 9 days. Disturbance did not have any noticeable impact on sediment characteristics, SCOC, or nematode species richness, but led to changes in vertical distribution patterns and shifts in nematode community structure. The magnitude of disturbance-related effects was, however, much smaller than the effect of sediment depth (0-1, 1-3, and 3-5 cm), and the main impact of disturbance on nematode vertical distribution patterns and community structure appeared to be related to a vertical re-shuffling of nematodes in the sediments rather than mortality. We did not observe substantial increases in the abundance of nematode genera generally regarded as disturbance-tolerant, such as Sabatieria. The worst-affected species belongs to the Stilbonematinae, a group of typically long and slender nematodes that may be easily damaged by physical disturbance. The limited impact of physical disturbance on benthic community structure and function suggests that the Chatham Rise nematode community is relatively resilient to sediment resuspension. This resilience may have arisen from frequent exposure to disturbance in the field (e.g., from strong currents), or may be a more widespread feature of nematode communities.