Graduate students Christian Briseno and Lina Lawrence took the second version of our zooplaknton imaging sonar (MAZOOPS) out on the R/V Melville as part of the Cal-Echoes Research Program. This version of MAZOOPS provides high-resolution (~30 micron) optical images and high-frequency, broadband acoustic data from zooplankton. The system willl be used in concert with many other sampling modalities to study the animals in the water column of the Santa Barbara Basin. For more information about the research program go to: http://calechoes.ucsd.edu
We returned yesterday from the first deployment of the new MAZOOPS zooplankton sonar at sea. We were able to deploy the system several times per day, and collected nearly 100 GB of acoustic and image data from two different stations off the coast of San Diego. Deployments of the MAZOOPS were combined with MOCNESS tows and the two modalities generally showed good agreement.
In total, the system was deployed eleven times during the four day cruise. Typically, the system was deployed running in autonomous mode during the day down to 250 meters, and running in tethered mode with real-time data during the night down to 100 meters.
During the daytime, typical profiles showed that most of the acoustic scattering was down around 250 meters or deeper. These data were supported by images from the low-light-level camera on the MAZOOPS. Image data showed that copepods and euphaussiids were likely the most abundant animals, and these data were confirmed by the MOCNESS tows.
On two occasions, while idling at 30 meters depth, the system encountered very high concentrations of euphausiids which were seen in acoustic data as a dramatic increase in the number of echoes and also the amplitude of these echoes. Image data showed a proportional increase in the number of animals imaged. These small scale features are unlikely to be seen in MOCNESS data (due to its averaging of animal concentrations over much larger scales than the MAZOOPS.
One of the key features of MAZOOPS is the combination of acoustic and optical imaging sensors that image the same field of view, making the system truly multimodal. By combining these data together more information about the type of animal and its orientation are available to aid in understanding acoustic echoes. The multiview nature of the acoustic system can then be used in concert with optical imagery to obtain improved estimates of shape and/or taxa specific abundance.
A big thanks to Jules, Fernando, Florian, Prasanna, Justin, Christian, Gabriel, Paul, the crew of the R/V Sproul, and all of the other team members who made this cruise possible.
Below are a few images from the cruise:
We just returned from our spring cruise to Dabob Bay in the state of Washington. The purpose of our cruise was to explore a hypothesis that has to do with the foraging behavior of zooplankton, the small (1-4 mm) animals that live in the sea. Every night they make a big trip to the surface waters from the deeper parts of the ocean to forage on plants (phytoplankton). Once there, do they eat, turn around, go back down? or: Do they eat and keep eating up in the surface waters? Our new imaging system is a bispectral (two wavelength) method which records not only the green reflected light from their outsides (carapace) but also their insides (the phytoplankton) that they ate that fluoresces in the red. Together, the green reflected light and the red light from their insides tells us which animals they are and how recently they ate. We spent about 8 days on the U. of Washington ship the Tommy Thompson in Dabob Bay and worked almost all night to see these little guys make a living. We returned, tired but happy with lots of great data that will help us try and unravel how these animals, probably the most numerous multicellular animal on the planet, make a living.