Snapshots of the Crew: Hank Carson

Hank Carson here, a post-doctoral researcher in marine debris science at University of Hawaii, Hilo. I came along on this voyage for a number of reasons, but my main research goal was to characterize the community of organisms living on, or associated with, plastic in the North Pacific Gyre. Does the debris transport invasive species? Even for species that are already “supposed” to be there, that have adapted to live on drifting objects, how does providing these particular organisms with unlimited and durable new habitat platforms affect the ocean ecosystem? Our original plan was to sample a huge transect from the tropical waters around Hawaii to the temperature waters off Canada and see what, if any, shifts in the “plastisphere” we saw along the way. This is the reason I brought a temperature and salinity meter on board, so that we could match all samples with information about the physical environment in which they were found.

Any sampling plan is at the mercy of the elements, and the rough weather has limited our ability to conduct manta trawls along the whole transect. We’ve had more luck with the high-speed trawl, although the samples out of it tend to be more abraded and scoured by the speed, and aren’t good for attached organisms. Even so, we’ve got a dozen manta trawls from the calmer portions of the route, many on an east-west transect at 40° N, instead of a north-south transect. I’m excited to get those samples, now preserved, back to Hilo to take a closer look at them through an electron microscope.

The most interesting work so far to me has been our opportunistic sampling of larger debris. From netballs, floats, mats and crates I’ve identified:
  • two kinds of bryozoans (colonial “moss” animals)
  • a hydroid
  • two kinds of fish eggs
  • two kinds of barnacles (goose-necked and “regular”)
  • a crab and also its late larval stages (called megalopae)
  • an isopod (a kind crustacean)
  • an amphipod (another kind of crustacean)
  • two kinds of polychaete worms
  • a flatworm
  • a roundworm
  • an anemone
  • a boring mollusc (known as a “shipworm”)
  • a nudibranch (a sea slug, or mollusc without a shell) and its egg capsules
  • and perhaps the most entertaining to me, a pacific oyster

Some of those animals, including the oyster and one of the barnacle species, are a long way from home. We’ve also seen our share of drifting organisms caught together with the plastic, including the by-the-wind sailor jelly and its predator, a beautiful purple snail that rafts on bubbles to seek out the jellies.
A highlight to me was definitely diving on the tangled mass of nets and traps to clip off samples. The associated fish swam in sort of an inverted food pyramid, with reef fish such as chubs swimming on the surface with the nets, larger rainbow runners schooling underneath a few meters, and a troupe of beautiful mahi mahi circling further in the depths. As exciting as the fish was the fact that the net ball drifted attached to the Sea Dragon at one or two knots … meaning that we had to keep up with our fins or get left behind. You don’t want to miss this bus, because there won’t be a next one.