Our second post today is from Meg Rippy.
Hello everyone, Meg Rippy here. I realized recently that I haven’t really described why I’m out here in the North Pacific subtropical gyre, other than a brief mention that I study marine bacteria. Let’s correct that, shall we? First, a bit about marine bacteria. Typically when we think about bacteria we conjure up images of infected wounds, colds, and other unpleasantness. Most bacteria, however, are beneficial. They can be thought of as the recyclers of the ocean because they play an important role in decomposing dead matter, which releases inorganic nutrients that other living organisms need to grow. Without bacteria nutrient concentrations in the ocean would decrease, the phytoplanktonthat form the base of ocean food webs (like plants do in terrestrial systems) would be less abundant, and zooplankton, fish, birds, and mammals would have less to eat. The ocean needs its bacteria folks, so leave the Lysol at home ;).
Besides playing an incredibly important role in marine food webs, the bacteria in our oceans are also extremely abundant and diverse. On average there are around one million bacteria living in every milliliter of seawater and no two bacterial species within that milliliter are exactly the same. Efficient recycling of dead matter requires an entire community of bacteria with complementary metabolisms that break down different compounds. Some of these bacteria specialize in the colonization of particulates and some are free living in the water column. A subset of the marine bacteria that specialize in particle colonization are called biofilm formers. They form thick coatings on solid objects. My work on the SEAPLEX cruise directly concerns these biofilming bacteria, which may opportunistically colonize plastic debris as well as organic matter. If these bacteria colonize plastic, then bacterial communities in high plastic areas could contain more biofilm formers than is typical for the open ocean. This could possibly perturb ocean nutrient cycling and/or food webs, but we don’t really know how. The role of bacteria as the ocean’s primary recyclers makes it important for us to find out.
It is also important to point out that some biofilm bacteria serve as cues for the settlement of invertebrates like polychaetes (marine worms) and mussels. In this light, plastic and associated bacterial biofilms could serve as a transport mechanism for coastal invertebrates, bringing non-native (invasive) species into the gyre and possibly to distant shores. Non-native organisms can be extremely problematic for local ecosystems because some invasives survive better than local species and can take over an area, drastically altering the local food webs that depend upon native species. The association between plastics, bacteria, and invertebrate fouling has been one of my focuses these past few weeks. So far we have collected large pieces of plastic from the small boat and smaller pieces via dip netting. The bacterial communities on these plastic pieces will be examined back on shore using genetic analyses that type bacterial groups using known DNA markers. Miriam Goldstein plans to examine the associated invertebrate fouling communities. So far we have already seen mussels, bryozoans, gooseneck barnacles, and an amazing number of small
crabs on our plastic samples. It will be really exciting to combine this information on invertebrate fouling with the bacterial data later this year.
The SEAPLEX team: (front row, left to right) Jesse Dubler, Andrew Titmus, Pete Davison, Doug Woodring, Karin Malmstrom, Miriam Goldstein, Darcy Taniguchi, Meg Rippy, and Chelsea Rochman. (back row, left to right) Timbo Stilliger, Jesse Powell, Mario Aguilera, Jim Leichter, Lara Dickens, Matt Durham, and Josh Jones.