Award: OCE-1130033

Our objectives for this project were to apply molecular tools (DNA-based analyses) to understand the distribution of certain kinds of microorganisms (ciliated protozoa) in the ocean. We know that these single-celled organisms are widespread and play important roles in the ocean's food web, but we do not know how different species vary in their distributions over space and time. Because of difficulties in identifying them, we do not even know how many kinds of these creatures exist in the world. Using DNA sequences in conjunction with traditional microscopy, we first made a short cruise in Fisher's Island Sound, USA, and evaluated how distributions of different species correlated with tidal currents and vertical layering in the water caused by temperature differences. We found that although clear patterns were difficult to discern, the influence of freshwater on mixing seemed to be important; and we found that our molecular methods could be used successfully in the field. Following the short cruise, we made a longer expedition beyond the edge of the continental shelf south of Montauk on the RV Cape Hatteras. On this longer cruise, we were able to sample over a much greater scale, sampling throughout the water at 39 stations. One surprising result was that a small goup of about six species was found in the majority of samples over a scale of more than 150 km. These six were joined by a further group of four species that were only found in the offshore samples. Even more surprising, these common ciliates were found even in very deep waters, far from the sunlit waters where they were presumed to live. We have recently been using a more detailed molecular technique called Illumina MiSeq to look into these distributions in the same samples in more detail. One other interesting outcome of this research is that the DNA-based methods allowed us to sample much more comprehensively than traditional microsocpy and this allows us to be much more confident that we have sampled all or nearly all the species present in an area, even ones that would be too rare to observe by microscopy. The results suggest that individual species are ubiquitous in the ocean with very few limits on their dispersal. For example, on samples from a single day in Long Island Sound, we found sequences identical to about 8% of all those recorded for this group of plankton in the public database at the National Center for Biotechnology Information (NCBI). For comparison, if 8% of all the world's bird species were present in one day in a single area (e.g. Central Park in New York), that would be about 800 different birds! In the history of bird watcing in Central Park, which opened in 1859, a total of 275 species have ever been observed. We conclude from this that microbes are much more widely distributed around the world ocean, compared to larger organisms, with minimal likelihood of geograpic isolation. In addition to the cruise results, we have performed some preliminary experiments to determine what factors (predators, food availability, temperature, ocean pH. etc.) are most important in determining what species will be present in a given area. By isolating samples in sea tables and subjecting them to changes in these factors, we can examine them under controlled conditions and see how they change. So far, it seems that predation and food availabilty are the most important factors, but we are continuing this line of inquiry. To ensure that this research has broader impacts in society beyond its intellectual merit, we have been engaged in public outreach to describe our work in coursework, graduate training, teacher workshops and through public lectures at the Woods Hole Oceanographic Institution, Sea Education Association and other venues. Data from this project are archived at the BCODMO website: http://www.bco-dmo.org/project/2164 Last Modified: 10/16/2015 Submitted by: George B Mcmanus