Controlled field experimentation in marine ecology is well established for shallow water habitats. Due to technical and logistical difficulties, experimental work in deep waters is still in its infancy. Prerequisite for experimental approaches at the deep seafloor is the availability of free-falling devices and remotely operated vehicles (ROVs). Especially the regular access on a deep-diving ROV allowed us to conduct unique short- and long-term experiments at the deep-sea long-term observatory HAUSGARTEN.

The small benthic biota (range: bacteria to meiofauna) is in focus of our experimental work. Their reaction to sporadic food supplies was studied by spreading algae suspensions over isolated areas of the sediments, and by the deployment of colonization trays containing natural or artificial sediments enriched by various organic matters. Bundles of dead fish as well as a small whale carcass were set out at the seafloor to simulate “large food-falls”. Large cages with solid top lids were installed to prevent the settling of particulate organic matter (POC) over distinct areas (“starvation experiment”).

Smaller cages with partly open tops were deployed to exclude disturbances created by larger benthic organisms from certain spots at the seafloor. Plough-like disturber units were used to repeatedly perturbate the upper sediment layers at different frequencies, in that way mimicking enhanced megafauna bioturbation. A flume, 8.5 m in length and 50 x 50 cm in cross-section, has been installed to increase current velocities at the seabed, thereby also reducing POC sedimentation.

Results from the outlined experiments will help to elucidate how sediment-inhabiting organisms interact with each other and with their changing environment.

Contact:  T. Soltwedel, C. Hasemann, I. Schewe

Literature:

Gallucci, F., Sauter, E., Sachs, O., Klages, M. & T. Soltwedel (2008). Caging experiment in the deep sea: efficiency and artefacts from a case study at the Arctic long-term observatory HAUSGARTEN. Journal of Experimental Marine Biology and Ecology 354 (1): 39-55.

Kanzog, C., Ramette, A., Quéric, N.V. & M. Klages (2008). Response of microbial communities to chitin enrichment: an in-situ study in the deep Arctic Ocean. Polar Biology 32: 105-112.

Premke, K., Klages, M. & W.E. Arntz (2006). Aggregations of Arctic deep-sea scavengers at large food falls: temporal distribution, consumption rates and population structure. Marine Ecology Progress Series 325: 121-135.