Bioturbation rates in the deep Fram Strait: Results from long-term in situ experiments at the arctic LTER Observatory HAUSGARTEN

• Published in: Journal of Experimental Marine Biology and Ecology
• Main Authors: Soltwedel, Thomas, Hasemann, Christiane, Vedenin, Andrey, Bergmann, Melanie, Taylor, James, Krauß, Florian
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: ELSEVIER SCIENCE BV 2018
• Subjects: Arctic; Arctic Ocean; Fram Strait
• Online Access: https://epic.awi.de/id/eprint/46021/; https://hdl.handle.net/10013/epic.a2ec3e00-8974-4b0e-9e71-8f751d31f0d6

Benthic fauna constantly modifies their physical, chemical and biological environment. The permanent biological reworking of surface sediments mediates biogeochemical processes at the seafloor and is, therefore, of global importance. There are numerous studies measuring the rate and extent of bioturbation worldwide, however, information on mixing rates in the deep ocean and especially in the Polar Regions are extremely scarce; to our knowledge there is, by now, only a single study providing bioturbation rates from the deep Arctic Ocean. The present study presents mixing rates and mixed layer depths for the deep seafloor at the LTER (Long-Term Ecological Research) observatory HAUSGARTEN in Fram Strait, Arctic Ocean. Two stations at similar water depths (2400 m and 2500 m water depth, respectively) but approx. 55 km apart from each other were chosen to carry out long-term (2 and 4 years, respectively) in situ bioturbation experiments using luminophores as a tracer. Biodiffusion-like mixing rates Db at the experimental sites were rather similar (0.26 cm2 a-1 at HG-IV; 0.28 cm2 a-1 at S3); slightly (non-significantly) higher Db values at the southern HAUSGARTEN site S3 could be explained by more favorable environmental conditions and related differences in the faunal composition. Indications for a non-local transport of sediment particles from the surface to deeper parts of the sediment, resulting in higher values for the Non-Local Index (NLI), could only be found for the central HAUSGARTEN site HG-IV. Elevated densities of burrowing megafauna at HG-IV, compared to S3, might be responsible for the subsurface maxima in luminophore distribution and comparably higher NLI values at the central HAUSGARTEN site (5.37 at HG-IV; 3.26 at S3). Mixed layer depths L at the two sites were almost identical; considerable mixing of surface sediments occurred down to max. 6-7 cm sediment depth.