This project will use the opportunity of a ship crossing the North Atlantic at high latitude to conduct a high-resolution sampling transect of mesozooplankton, marine "snow" (biogenic aggregates), and environmental variables from Aberdeen, Scotland to southern Greenland via a route south of Iceland, thence south across the Labrador Sea and the Grand Banks to Woods Hole, MA. Sampling will be done with the Video-Plankton Recorder II (VPRII). The VPR enables non-destructive sampling of fragile plankton in situ, and through rapid tow-yo deployments (continuous raising and lowering while under way), it provides high vertical (top 150 m) and horizontal resolution of robust as well as fragile plankton and aggregates and numerous environmental variables. The VPRII has now been deployed in several locations around the world, but there is no comparable data set for the far North Atlantic, an area of intense ecological interest. This opportunity arises from the delivery of a new research vessel, R/V Falkor, to the Woods Hole Oceanographic Institution. The budget covers technician time, travel to the ship, and supplies. The fact that ship time comes "free" because of the transit makes this an exceptionally cost-effective way to sample. This project will collect a major data set that will be available for analysis, and data that can be quickly processed (acoustic, hydrographic, automated image analysis) will be available to the community soon. Two Ph.D. students will participate in the cruise, adding to their training in oceanography and high latitude marine science.
The North Atlantic basin and adjoining shelf seas are critically important to the ecological and socio-economic health of North America and Europe. This region feeds the global ocean circulation and is subject to freshening due to polar ice melt. It also is a major source of the dominant transatlantic copepod species, Calanus finmarchicus, and includes shelf and oceanic ecosystems that support large fisheries. This region is the focus area of the recent EU-North American BASIN program, whose goal is to better understand the north Atlantic subpolar system, including both shelf and basin and their connections. Prior to this study, there were no existing high-resolution data on the vertical-horizontal distribution of zooplankton across the entire region. Furthermore, traditional sampling methods are typically destructive and do not provide data on important delicate taxa and marine snow. Data on the relationship of plankton taxa to their environment across a continuum of scales from the individual organism to the basin scale is needed for better insight into the underlying processes controlling their populations. A vessel of opportunity, the maiden voyage of the Schmidt Ocean Institute (SOI) ship, R/V Falkor, (July 2-28, 2012), was used to tow the second generation Video Plankton Recorder (VPRII), an underwater digital video microscope, across the North Atlantic (Fig. 1). The VPRII was towed along a continuous transect from the northern UK shelf to the southern Greenland shelf (Leg 1, FK003a) followed by a second continuous transect from Nuuk, Greenland to the North Atlantic Slope Water south of Nova Scotia (Leg 2, FK003b). The survey yielded an unprecedented data set on the relationship of plankton to their environment across multiple scales in the North Atlantic sub-polar gyre and adjacent shelf and slope seas. The VPRII (Fig. 2) is an underwater video microscope that images plankton and particles and collects data on environmental variables. The tow body was designed to avoid disturbing the imaged volume prior to sampling it, minimizing avoidance by zooplankton and destruction of delicate plankton and marine snow. The VPRII includes a digital video camera and strobe mounted on a fast, 5m/s (10-knot) towfish that undulates automatically between the surface and 130m and steers to starboard when surfacing to avoid the ship’s wake. The VPRII environmental sensors included a CTD, fluorometer, and ambient light sensor. Data are sent from the VPRII to the ship via electro-optical tow cable. Image analysis software automatically identifies plankton and marine snow in the size range of 100 microns to centimeters, providing quantitative abundance estimates. The VPRII successfully sampled a 5382-kilometer (2906 nautical mile) transatlantic transect (Fig. 1), providing high quality images of plankton (Fig. 3) together with environmental data (Fig. 4). Unprecedented numbers of plankton images were recorded during leg 1 due to an extensive bloom of chain-forming diatoms and other plankton (Fig. 4). This bloom was unexpected given the time of year (July) and large spatial extent (>1000 km). The VPRII data were collected simultaneously with underway acoustic-backscatter data (Simrad EK60 and hull mounted ADCP) that measured larger zooplankton and nekton (e.g., fish, squid, shrimp). A series of deep CTD casts and plankton net tows were made at daily stations along the transect. Satellite data on temperature, chlorophyll, and sea level height are being used to identify oceanographic features sampled along the transect and relate them to the in situ data. The continuous high-resolution vertical section of data, across a wide diversity of habitats, oceanographic features, and water masses, is currently being processed using other funding and is part of a PhD thesis. Two PhD students participated in this cruise. These students are using optical, acoustical, and net sampling to study marine zooplankton distributions in their thesis work. The experiences and training during the cruise provided them an excellent opportunity to learn these sampling systems and the North Atlantic subpolar gyre ecosystem. The completed survey demonstrates the capability for trans-ocean surveys using digital imaging, which can be incorporated into future sampling programs using ship’s of opportunity. Data have been made publicly available via the Biological-Chemical Oceanography Data Management Office at Woods Hole.
