The Deep-Sea Ecology and Biogeochemistry research group operate a number of unique technologies that are used to understand ecosystem processes at the deep seafloor. Our seafloor lander fleet comprises 7 deep-sea landers (free-vehicles), and include 2 respirometer or benthic chamber landers, a micro-profiling lander, 2 baited-camera landers and 2 baited-trap landers. With these instruments we can carry out experiments to measure seafloor respiration, nutrient fluxes, C-cycling processes and census and capture seafloor megafauna (e.g., scavengers) down to 6,000m (approx. 20,000 ft) water depth. We also house 2 micro-landers capable to being deployed by submersible or ROV down to 11,000m (36,000ft). All pictures here were taken by A. Sweetman, M. Cecchetto, A. Moser and J. Murray Roberts (Univ. Edinburgh)
Respirometer or benthic chamber landers
Our 2 respirometer landers are large circular devices with 3-4 benthic chambers mounted in the centre of each lander. Each lander is deployed autonomously at the sea surface and sinks to the seafloor (down to 6000m water depth) as a free vehicle. There, the benthic chambers (see below) are pushed into the sediment for a pre-set period of time (i.e., the incubation period) via electric motors and an onboard computer. During the incubation, the oxygen concentration of the seawater overlying the seafloor sediment is monitored by Aanderaa oxygen sensors allowing seafloor respiration rates to be quantified. Water samples are also periodically collected from above the sediment in each chamber at pre-programmed times by onboard syringe samples. From these samples it is possible to measure the concentration of oxygen, dissolved inorganic carbon (DIC or respired carbon dioxide), and nutrients in the seawater overlying the sediment. By measuring their concentration over time it is possible to measure the flux of these constituents across the sediment-water interface, and thereby parameterise biogeochemical processes. At the same time as the lander is collecting water samples, it can also inject isotope-labeled substrates (e.g., isotope-labeled organic matter) over the sediment in each chamber. The uptake of labeled C and N can then be tracked into sediment-dwelling organisms and DIC, which makes it possible to quantify the uptake and turnover of specific elements and assign the organisms and pathways responsible. This can then allow insights into the biological and geochemical processes taking place at the seafloor.
Our 2 baited camera landers are essentially what the name suggests, a lander with a camera and a bait mounted underneath the camera, which allows us to census deep-sea scavenging fishes and invertebrates at the seafloor. We presently operate two baited-camera landers.
The first 6000m-rated lander (left) features glass floatation and an Ocean Imaging Systems DSC 24000 digital camera system with 2 strobe flashes, and is often used in abyssal plain habitats .
.The second lander (left) uses syntactic foam and is capable of being deployed to 6000m depth on seamounts, in canyons as well as on soft-sediment habitats and features a state-of-the-art Ocean Imaging Systems digital and HD-video camera system with strobes and Deep-Sea Power and Light red and white lights. Both landers also feature Nortek Aquadopp 6000 ADCP current meters.
Deep-sea microprofiling lander
Our deep-sea microprofiling lander allows us to measure biogeochemical profiles of seafloor sediments in situ at ultra-high resolution, which allows us to measure fluxes of various metabolites (e.g., oxygen) across the sediment water interface or put ecosystem processes into an environmental context. The profiler can measures oxygen, pH, redox and sulphide concentrations at a resolution of 25-microns down to 20cm sediment depth, and is developed by UNISENSE / KC-Denmark.
Deep-sea baited trap landers
The team operate 2 baited trap landers that are used to collect benthic and demersal scavengers. The samples collected by the trap can be used to help identify the animals seen in the baited camera (see above) images, as well as collect samples for food-web analysis (stable isotopes, fatty and amino acids) and ecotoxicology.