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Hydraulic activities by ghost shrimp Neotrypaea californiensis induce oxic-anoxic oscillations in sediments
Citation:
Volkenborn, N., L. Polerecky, D. S. Wethey, T. H. DEWITT, AND S. A. Woodin. Hydraulic activities by ghost shrimp Neotrypaea californiensis induce oxic-anoxic oscillations in sediments. MARINE ECOLOGY PROGRESS SERIES. Inter-Research, Luhe, Germany, 455:141-156, (2012).
Impact/Purpose:
We applied porewater pressure sensing, time-lapse photography and planar optode imaging of oxygen to investigate hydraulic behaviors of the Thalassinidean ghost shrimp Neotrypaea californiensis and the associated dynamics of oxygen in and around their burrows.
Description:
We applied porewater pressure sensing, time-lapse photography and planar optode imaging of oxygen to investigate hydraulic behaviors of the Thalassinidean ghost shrimp Neotrypaea californiensis and the associated dynamics of oxygen in and around their burrows. Ghost shrimp were hydraulically active 40% of the time. For more than 90% of this time the sediment was pressurized, which caused transport of oxygenated water into the burrow, into the sediment surrounding the burrow, and of anoxic water through the sediment-water interface. Some hydraulic behaviors, e.g., sediment blow-outs and irrigation episodes with the shrimp in head-down orientation, caused flow reversals and porewater transport towards the burrow. The hydraulically most important behavior was burrow irrigation by pleopod beating, which was performed at different locales within the burrow and occurred in intermittent bouts with an average frequency of 9 bouts per hour, each lasting on average 2.3 minutes. In parts of the burrow lumen frequented by the shrimp, this irrigation was sufficient to maintain oxygenated conditions during >90% of the time with oxygen concentrations typically below 40% air saturation. Intermittent and bidirectional irrigation at different locales induced irregular oxygen supply to the sediment surrounding the burrows with oxic and anoxic conditions alternating on the scale of minutes and oscillation frequencies in the range of 1-1.5 h-1. This oscillatory region was restricted to a few millimeters around the burrow in muddy sediments, but extended up to 4 cm away from the burrow in more permeable sediments. The oscillatory character of porewater chemistry induced by hydraulic activities of benthic infauna such as thalassinid shrimp is expected to have significant effects on microbial diversity, organic matter mineralization and other biogeochemical processes in marine sediments.