• Overnight sampling in the South Pacific Subtropical Gyre. The South Pacific is one of the least studied biomes on the planet. In November-December 2010, we helped to organize and lead an expedition from Arica, Chile to Easter Island in order to study microbial community metabolism in some of the most oligotrophic waters of the planet. Photo by Dr. Mar Nieto Cid.

  • Water sampling at Station ALOHA. In order to collect pristine water samples for chemical and microbiological analyses, we use a “rosette” fitted with specialized, ultra-clean Niskin bottles. The weighted rosette descends into the deep ocean with the bottles open, communicating back to the ship information about water temperature, salinity, dissolved oxygen, and chlorophyll fluorescence. As the sampler is brought back to the surface, we can remotely trigger the bottles to close at depths of our choosing.  

  • Cooking in the lab. La’Toya James, a long-time guest student shows off a batch of specialized resin she synthesized for the extraction of dissolved organic phosphorus from seawater. We work to develop new techniques to address critical issues in marine chemistry, which often involves customizing our instrumentation or chemical analyses.

  • Oceanography is a very “hands on” science. Although we spend most of the year in the lab, more and more sample processing is done on board research vessels. Here summer student Katherine Heal works with me to collect samples off the coast of Chile.

  • Our lab belongs to the Center for Microbial Oceanography Research and Education (CMORE), a National Science Foundation Science and Technology Center designed to support innovative, potential transformative, complex research and education programs that require long-term support. Much of our work is based in the tropical and subtropical Pacific Ocean. Here graduate student Jamie Becker dives on a coral reef near Fiji Island before embarking on a cross equatorial cruise.

  • Sight-seeing on Rapa Nui (Easter Island). After a month at sea, we are ready to be on land once again and visit some of the local sites. Photo by Jamie Becker.

  • A recent cruise took us down the west coast of Mexico, around Baja, and into the Sea of Cortez, which supports a rich ecosystem. Here a flying fish makes its escape as we begin a hydrocast.

Microbial biogeochemical cycling of dissolved organic matter

Educational Opportunities
If you are interested in working in our lab, go to:
WHOI Academic Programs »

Each year marine phytoplankton extract enormous quantities of carbon dioxide, nutrients, and minerals from the atmosphere and ocean to manufacture the proteins, carbohydrates, and lipids needed to sustain life. Microbes continually reorganize the distribution of nutrients and minerals in seawater in response to ever changing environmental conditions, such that regional and local variations in climate yield a diverse community of phyto- and bacterioplankton that are highly tuned to their environment. At the molecular level, this diversity and tuning is expressed as the microbial community’s genome. Genes direct the synthesis of organic chemicals, and the enormous diversity we observe in microbial genomes is the source of an equally diverse suite of organic chemicals present in seawater. This dissolved organic matter (DOM) is itself a factor in shaping the microbial community and directing many biogeochemical cycles. Understanding what organic compounds are present in the environment, how they impact microbial metabolism, and why they are preserved in sediments is fundamental to our knowledge of elemental cycles in the ocean. With support from the National Science Foundation and the Gordon and Betty Moore Foundation, we are engaged in a number of projects designed to investigate the microbial biogeochemistry of organic matter cycling in seawater.

All of our research uses advanced organic chemical analysis in collaboration with other laboratories that specialize in genomic, transcriptomic, or trace metal analyses as well as mathematical modeling of biogeochemical cycles. As these projects unfold, there are many new opportunities for student research through the WHOI summer and guest student fellow programs and MIT/WHOI Joint Program in oceanography, as well as co-op partnerships with other universities. If you are interested in learning more about research opportunities in our lab, please contact us at drepeta@whoi.edu.