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THE MAINE EVENT: FALL 2003 Predation by Gelatinous Zooplankton in the Gulf of Maine MISSION DISPATCH 11 • Monday September 22, 2003 Location: Lydonia Canyon (40° 18.7'N and 67° 38.8'W) Dispatch by Brian Cousin - Harbor Branch Oceanoraphic Institution We are transiting from Georges Basin to the deep-water (ca. 3000 feet, 985 meters) canyons that indent the southern boundary of Georges Bank. The trip around the bank and its shoals takes about 15 hours. The site for our first JOHNSON SEA-LINK II (JSL II) dive this evening is Lydonia Canyon, at approximately 40° 18.7'N and 67° 38.8'W. The sky is blue (a welcome sight after the thick fog of the previous two days) and seas are calm for the time being. Norwegian Research Scientist Dr. Per Flood is in the wet lab, focused intently on the screen of his laptop computer as he edits a digital photograph of the deep-water ctenophore Beroe cucumis. With a critical eye, he removes minor imperfections, sharpens slightly, adjusts contrast, corrects color. Per is compiling a photographic atlas of marine plankton, a vast multitude of drifting organisms that inhabit all the oceans. "The idea is to assemble a collection of photographs of the more common planktonic 
organisms so people can identify what they find in the sea," Per explains. Per has been producing professional quality
images since about 1990. On this trip he has added a digital camera to his arsenal of photographic equipment that
interfaces with a dissecting microscope. Atop a more powerful compound scope, he maintains a 35-mm film camera. By
combining aspects of images from each magnifying instrument, Per is creating photographic composites that reveal the
remarkable morphological details of various creatures. The photograph of each organism is accompanied by a description
of where the organism was collected and what is known about its natural behavior. And that's what makes Per's work so
different. "Photography is an objective, physical process, in contrast to drawing, which is in principle a subjective
process - a product of the mind. The eye observes the subject, it is processed in the brain, and the hand is made to
interpret the result on paper."
Per also notes while drawings may include the most prominent morphological features, they often omit minor ones, or that illustrators may use a degree of creative license to complete a drawing. Either approach can be the cause of confusion and mis-identification of species by researchers relying on these hand-drawn illustrations. "Also, many drawings are made from fixed (preserved) specimens. An illustrator may never have seen the living organism and therefore cannot show the color, shape, or behavioral characteristics," Per says. As the depth and breadth of marine science grows, accurate representations of the plankton world become even more important, so that scientists, other than qualified taxonomists, can easily identify a range of common species. Per says he has about 300 species of phytoplankton and zooplankton so far, including Nanomia cara, Bolinopsis infundibulum and Beroe cucumis from the Maine Event. "This is a long-term project," he says. But Per has made all of his images by traveling "in-situ" - where the organisms live. That has taken him to the Mediterranean Sea along the south coast of France, the northwest and southwest Pacific in Washington and California, the Gulf Stream adjacent to Florida and the Gulf of Maine region where he is hard at work today. It's clear Per Flood enjoys his work very much, as well as the prospect of making a compendium available to the scientific community and the general public. "I am not satisfied with just a picture, it must also be aesthetically pleasing, approaching - maybe art is too ambitious a word - but the photos must be appealing. Part of my intention is to introduce people to the natural beauty of marine life." Earlier this year, about 100 of Per's photographs were exhibited in Gijon, Spain at a major international conference on marine zooplankton. "My favorite marine animals are undoubtedly the larvaceans or Appendicularians. These are small and transparent organisms belonging to the same group as salps and sea-squirts and located at the transition between invertebrates and vertebrates in the animal kingdom. I often nick-name them "vacuum-cleaners of the sea" since they feed by sucking water through a complex set of filters to extract all small particles, including bacteria, single-celled algae and decaying organic matter. These particles provide the food for their growth. I discovered these extremely fine-meshed filters more than 30 years ago and feel in many ways I have been trapped in them ever since. On this cruise I hope to study several of the poorly known, deep-water species of larvaceans. When we reach the 3000 ft. maximum depth of the submersible that we are using in the canyons south of Georges Bank, we are likely to encounter species that nobody has ever seen! Today we know that shallow water larvaceans, due to their unique external filter-house may grow 10 times faster than many other plankton organisms and also that they serve as prey for several commercially important species of fishes. These facts indicate that larvaceans constitute a crucial link in an ultrashort food chain from the microbial level to exploitable marine resources: There are certain flatfish larvae that will starve to death if they cannot find larvaceans to eat. Recently, we also learned that mackerel to a large extent depend on larvaceans as food. I am convinced that improved knowledge of larvacean biodiversity and ecology in the future will help us understand the annual variations in fish stock recruitment far better than we do today." Fun Facts for the Day • For the purpose of navigation, the globe is divided into lines of Longitude and Latitude that are expressed in degrees, minutes and seconds. Lines of Longitude run north-south and lines of Latitude run east-west. One point of each coordinate corresponds to an exact position on the earth. Find our location in Lydonia Canyon as closely as you can in an atlas or on a chart. A change of 1 degree of Latitude equals 60 nautical miles (111 kilometers). One nautical mile equals approximately 1.15 statute miles. • One fathom equals 6 feet.   |  |
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