Mechanical imitation of bidirectional bioadvection in aquatic sediments

Abstract

Measuring the effects of bioirrigating infauna on sediment properties and geochemistry is often problematic due to the unpredictable nature of the animal activity. This can be overcome by the use of mechanical systems that mimic bioirrigation in a controlled and reproducible manner. A realistic mimic must allow both qualitative and quantitative imitation of the complex infaunal activities, i.e., generate both positive and negative porewater pressure waveforms in a realistic range of amplitudes and frequencies using biologically realistic water volumes. We developed a mechanical irrigation system (Robolug) that meets these criteria and used it to mimic a set of specific hydraulic behaviors of the common lugworm Arenicola marina. The resultant porewater pressure waveforms had realistic shapes and amplitudes and were realized by pumping biologically realistic volumes of water. The porewater flow patterns at depth and at the sediment water interface, induced by bidirectional bioadvection, were comparable to those observed with live lugworms. Additionally, we were able to reproduce the formation of sedimentary cracks, a phenomenon also observed with real lugworms. The Robolug irrigation system is a promising tool for a wide range of biogeochemical and ecological studies, as it (1) allows the exploration of bio-hydraulically induced disruption of sediment integrity and transient geochemical conditions in a controlled and reproducible manner; (2) avoids the uncertainties of animal performance; (3) permits manipulative experimental conditions that could potentially be harmful for organisms or alter their behaviors; and (4) allows for the investigation of energy requirements associated with bio-hydraulic behaviors.

Relating divergence in polychaete musculature to different burrowing behaviors: A study using opheliidae (Annelida)

“…For instance, injector organs (or gular membranes) are found in Arenicola (Wells, ) and the Thoracophelia / Ophelia clade, suggesting that this convergent feature is an important characteristic for sand burrowing; however, the presence of a gular membrane in the mud‐dwelling Notomastus (Eisig, ) does not follow this pattern. Moreover, Thoracophelia live in noncohesive, granular beach sands that differ mechanically from the heterogeneous sands in which arenicolids are found, where hydraulic fracture can result from irrigation, indicating that at least some of these sediments contain enough organic material to behave elastically (Matsui et al, ). Simple characterization of sand vs. mud may therefore overgeneralize the mechanical responses of sediments to burrowing behaviors.…”

Effects of Bioadvection by Arenicola marina on Microphytobenthos in Permeable Sediments

“…Six cylindrical containers (diameter 15 cm, height 18.5 cm) were filled with recomposed permeable sediment from the Oyster Landing site. The lugworm-mimic was administered through the use of the “robolug” system [ 28 ], which allows realistic imitation of porewater advection produced by lugworms. It consisted of a thin (1.6 mm inner diameter) tube, with one end connected to a peristaltic pump and the other end entering the sediment containers from the side and buried (14 cm deep) in the sediment at the central axis of the container.…”

Hydraulic activities by ghost shrimp Neotrypaea californiensis induce oxic−anoxic oscillations in sediments

“…We argue that to better understand the relationships between bioturbating infauna, microbial diversity, and biogeochemical processes, geochemical conditions in sediments need to be considered not only as highly heterogeneous in space but also as highly dynamic in time. Bioirrigation mimics that realistically imitate biohydraulically active animals (Na et al 2008, Matsui et al 2011 together with the analytical approaches employed in the present study provide a useful set of tools for elucidating the role of this dynamism at multiple spatial and temporal scales. …”

“…Oxygen distributions inside the sediments were measured with the luminescence lifetime imaging system described by Matsui et al (2011). In the present set-up, images were acquired at 30 s intervals, covered both shrimp tanks, and had an effective pixel size of 0.44 mm 2 .…”