About the Microfauna - The Plankton’s Story

One of the principal investigators (PI’s), Dr. Rudi Scheltema, has made the following contribution to the Journal. In this he shares with you how his part of the grant partnership (shared with Dr. Ken Halanych, Chief Scientist) works in the Cruise Plan. We log the raw field data, and from that Dr. Scheltema will write a report to the National Science Foundation and likely publish a journal paper at a later date. I will quote (and paraphrase) here the text Rudi contributed on the last cruise, in November 2004, that will further explain to you new readers the purpose of this cruise and associated study. In a later Journal, he will provide an account on what they’ve learned so far, from the first 2 cruises to Antarctica.
“The Drake Passage is the seaway separating the South American and the Antarctic continents. We make collections of drifting planktonic [“wandering”] organisms by putting collecting nets over the side of the ship every few hours [weather permitting] along a route between Staten Island (off Argentina) and the South Shetland Islands (off Antarctica) using a fine-meshed net three-quarters of a meter in diameter at its mouth (ca. 39?). Why do we wish to undertake such a strenuous program?
About 100 million years ago, during the Jurassic and Cretaceous geologic time periods, the single existing super continent named Pangaea became divided into two parts. One, Laurentia, “drifted” by means of plate tectonics to the north forming the continents of the northern hemisphere; the other half, Gondwanaland, moved to the south to form the continents of the southern hemisphere, namely, Africa, Australia, South America and the Antarctic. Then more recently, about 40 million years ago, Antarctica and South America separated to form the Drake Passage which we now cross on our way to the Antarctic continent.
As a consequence of this separation, the marine organisms that live in the waters surrounding the Antarctic continent (in particular the Antarctic Peninsula and South Shetland Islands) have been long isolated from South America. So long, in fact, that they have changed significantly and
evolved into a new unique “local” fauna, different but related most recently (remember, in geologic time) to that of South America. While the majority of marine bottom dwelling organisms differ from those of South America, some groups (taxa) remain largely unchanged and are found on both the South American and Antarctica continents, including 40 to 50 percent of all mud-dwelling worms and about a third of all echinoderms (meaning “spiny skinned”), which include sea stars and brittle stars. If such species are to remain unchanged they must have had some means to maintain contact with one other, that is, to reproduce with one another. We suggest that this contact may be maintained through the dispersal of their minute larvae passively carried long distances by ocean currents (i.e., they didn’t set out to “swim” there). Such dispersal is similar to that of plant seeds, for example milkweed seeds which may be carried by the wind or “air currents”.
So we will undertake to discover if larvae might not be carried long distances maintaining genetic continuity or reproductive relationship, like those we have established for tropical oceanic waters. We shall attempt to discover larvae in the Drake Passage and to determine how the “water babies” contribute to the geographic distribution of marine invertebrate bottom-dwelling organisms.”
That is the purpose of a large part of the ‘Plankton Team’s’ role of this research study to capture and identify many of the floating spawn among the ocean’s population. The other part that complements this is the“Benthic Team” side. Each time we do a benthic or “bottom” dredge, a large metal frame with a net attached is dropped to the ocean bottom, and is dragged for several minutes, collecting bottom-dwelling creatures. By comparing the DNA of the plankton and the ‘adult’ animals, these great minds will put together conclusive data documenting and pairing larvae with adult.

Every good specimen that is identified by eye as well as under a microscope is photographed and catalogued. Some of the critters are known in their taxonomic pairing (though not by DNA yet), and others are known by their families, but not for sure by their larval-to-adult relationships. Check out the images at right:

So here’s the point of this study these samples will all be analyzed via DNA technology, and their ‘relatives’ will be much more easily identified, if not definitively so.

Catch of the Day Finback whales

Perks of the trade a herd of finback (or are they humpback? The debate continues…) whales joined us today during the plankton tow portion of our
program. About 10 whales visited I mean, they swam along side, tipped on their sides to look at us watching them, and even swam under the ship while we moved very slowly in the water. Andy Mahon contributed one view of
these magnificent visitors or are they the hosts and we the visitors? in these Southern Ocean waters.

Don't hesitate to email questions to us at outreach@lmg.usap.gov