Effects of sediment disturbance on deep-sea nematode communities: Results from an in-situ experiment at the arctic LTER observatory HAUSGARTEN

• Published in: Journal of Experimental Marine Biology and Ecology
• Main Authors: Hasemann, Christiane, Mokievsky, V. O., Sablotny, Burkhard, Tekman, Mine Banu, Soltwedel, Thomas
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2020
• Subjects: Arctic; Fram Strait; Greenland; Svalbard
• Online Access: https://epic.awi.de/id/eprint/49926/; https://hdl.handle.net/10013/epic.5d40019f-1c29-4c33-a145-37a7071ae3ce

The present study examines the effects of experimentally generated disturbance on bathyal nematode communities at the LTER (Long-Term Ecological Research) observatory HAUSGARTEN, situated in the Fram Strait, between Greenland and Svalbard. In order to understand the complex interactions between the biota and environmental perturbations we deployed a free-falling device (bottom lander) equipped with three rotating fork-like disturber units, able to perturbate the upper sediment layers with different disturbance frequencies at chosen time intervals. During a one-year deployment at 2493 m water depth, disturber unit DI was programmed to rotate every 14 days, DII every 28 days, and DIII every 72 days, resulting in 28, 14, and 7 perturbations, respectively. Sediment sampling following this experimental period was conducted with push-coring devices deployed by the Remotely Operated Vehicle “QUEST 4000” (MARUM, Bremen). These sediment cores were sub-sampled to determine the effect of the sediment perturbations on various sediment parameters (i.e., grain size distribution, chloroplastic pigment concentrations) as well as on benthic nematode communities. A total of 4773 nematodes from 27 families and 81 genera were identified. Nematode densities in the disturbed areas ranged from 617 ind. / 10 cm2 to 1566 ind. / 10 cm2, with a mean density of 1193 ind. / 10 cm2 observed overall in the disturbed sediments. Control sediments contained on average 20% more nematode specimens than were found within the disturbed sediments, with an average density of 1477 ind. / 10 cm2 observed. Nematode evenness (J'), genera richness (EG(51)) and heterogeneity (H′) were not significantly different between the treatments and controls (undisturbed vs disturbance). We found a significant effect of the interaction of disturbance frequency and sediment depth (interaction term Fr x De) on heterogeneity and genera richness, while evenness significantly differed between different sediment depths (De) and within the disturbed sediments between ...