Instruments & Methods
Gitai Yahel Lab
Underwater Optical Oxygen Meter for continuous measurement of suspension feeders respiration - Firesting
In collaboration with Dr. Sally Leys , Jeremy Childress from the Sexton and with the support of Dr. Roland Thar from Pyro Science and Carsten Held from MacArtney we have built an underwater unit with online and standalone capabilities that allow us to study the respiration of undisturbed benthic suspension feeders in situ. The hurt of the instrument is a 4 or 2 channels Optical Oxygen Meter - FireStingO2 to which different oxygen probes can be attached. A battery pack, data logger, and web interface allow underwater spot measurements from within the exhalant siphon or oscula that can be as small as 2 mm and even within sponge bodies. The difference between the dissolved oxygen concentration in the water exhaled and inhaled by the organism is the amount of oxygen consumed per each liter pumped.
Photos from the Medas Islands (Spain) and from BC (Hex 2014)
“InEx” – a direct in situ method to measure filtration rates, nutrition and metabolism of active suspension feeders
Sponges, bivalves and tunicates play an important role in the trophic dynamics of many benthic communities. However, accurate in situ measurements of their filtration and excretion rates are lacking. Our knowledge of these rates is based on indirect, artifact-prone, mostly in vitro measurements. This paper presents and evaluates an in situ, non-intrusive technique to directly measure the rate and efficiency by which an active suspension feeder removes (or discharges) substances from (to) the water it filters. The technique, termed “InEx”, is based on the simultaneous, pair-wise collection of the waterInhaled and Exhaled by the animal. The difference in the concentrations of a substance among a pair of samples provides a measure of the retention (or excretion) of the substance by the animal. Calculations of feeding (or excretion) rates are obtained by multiplying the concentration difference by pumping rate. The latter is concurrently measured by recording the movement of a dye front in a transparent tube positioned within the ex-current jet. An important quality of the InEx technique is the lack of any manipulation of the studied organisms thus allowing realistic estimates of the organism’s performance under natural conditions. Preliminary results showing the diet composition, feeding rates and removal efficiencies of some coral reef sponges, bivalves and tunicates are presented and discussed.
SIP
The SIP is a new water sampler designed to allow clean point source water sampling. A simple valve operation by an ROV manipulator or a SCUBA diver allows the external water pressure to force the sampled water into a Teflon coated stainless steel sample cylinder. The small ID of the inlet tube (capillary PEEK) insures slow suction rate during the sampling. Sampling a cloud sponge at Barkley Sound, BC, 150 m depth. Two SIP samplers are operated simultaneously by the ROV’s (ROPOS) manipulators to sample the water inhaled and exhaled by the sponge.
VacuSIP
We introduce the VacuSIP, a simple, non-intrusive, and reliable method for clean and accurate point sampling of water. The system was developed and evaluated for the simultaneous collection of the water inhaled and exhaled by benthic suspension feeders in situ, to cleanly measure removal and excretion of particulate and dissolved compounds.
SEDON- An electronic underwater balance for the measurements of sedimentation rate
We are ideveloping an underwater electronic balances system that will allow (among other thing) the unattended or online of measurements of sedimentation rates at unprecedented resolution. To date, sedimentation rates are measured by manual deployment of sediment traps (open containers that collect the falling sediments) and by analyzing geochemical tracers in sediment cores. These measurements are inherently costly, labor intensive, and above all have a limited temporal resolution. "Sophisticated" sediment traps use a rotating battery of containers so that several samples can be taken at predetermined intervals. The SEDON is a low power mass monitor that is based on magnetic levitation that can be either deploy on the sediment surface, moored, or attached to the collecting funnel of a conventional sediment trap.
