The southernmost continent of Antarctica is the fifth largest continent and the coldest and driest place on earth.   Antarctica separated from the southern tip of the South American continent approximately 30 million years ago and has been isolated since. During this time, many of the marine animals living around Antarctica have evolved and are now different than any other animals in the world. These endemic animals are unique to Antarctica and include worms, molluscs, echinoderms, crustaceans and many others. However, some of the animals are able to live in both Antarctic and South American waters.

This research effort is looking at how the larval forms of some marine animals move between Antarctica and South America. By using plankton nets, we will look for larvae actually moving across the Drake Passage - one of the roughest bodies of water in the world. Because larvae are so small and the Drake Passage is so big, this will be like looking for a needle in a haystack.

However, we have found larvae in the Drake Passage on previous cruises in 2000 and 2001. Once we get back home, we will use genetic (DNA) tools on larvae and adults collected in Antarctica and South America to determine if animals in both locations are closely related. The best explanation for how these areas stay closely related is that larvae, not the adults, move long distances. In order to collect adults to investigate their DNA, we will use several different pieces of equipment to sample the shallow sea floors around the tip of South America and around Antarctica, at depths up to around 200 meters (around 600 feet). To collect the larvae forms, we will use plankton nets in the much deeper waters of the Drake Passage to capture the larvae as they travel across from one continent to the other. After collecting these animals, they will be identified on the boat based on their outward appearance, or morphology. We will then preserve the animals in a deep freezer so that we can study their DNA back in the laboratory. The DNA of larvae will also be used as a way to identify them since they are so tiny and very difficult to identify based on outward appearances, so we can match up the DNA from the larvae to the DNA from the adults and figure out which larvae belong to each adult animal.

Salps are pelagic animals, which means they spend their whole life cycle swimming in the water. Although each individual looks much like a blob of jelly, they are more closely related to animals with backbones (fish, birds, mammals etc.) than to real jellyfish. Salps feed on small particles. They are analogous to biological vacuum cleaners. They can clog if there is too much particulate matter in the water.

There is much to be learned about the salps that occur in the waters around Antarctica. The most common species of salp in these very cold waters (temperatures near freezing year round) does not occur anywhere else in the world. Salps occur either as long chains of many individuals or as solitary animals.

The emphasis of our study is to measure rates for several important processes including: respiration, feeding, defecation, reproduction.

We also will relate the distribution of salps with the quantity and quality of particulates in the water, in order to better understand important factors controlling salp abundance.

Salps are delicate animals. Therefore we SCUBA dive to collect the salps that are used in the lab.

Each of the “working divers” is attached to a central “trapeze”, where another diver is located. It is the job of this “safety diver” to oversee the dive, allowing the working divers to concentrate on collecting animals in jars.

Recent analysis of historical data from the last 80 years has revealed a marked decrease in the abundance of krill (small shrimp) and an increase in salps near the Antarctic Peninsula, where we will be sampling during the cruise. This change is linked with climate change and a warming of the waters in this region. The result has been less winter ice cover, a necessary habitat for overwintering larval krill but not salps.

There appears to have been a shift away from favorable krill habitat, towards a system that supports more salps. When salps are abundant, they can be the dominant grazer on small particulates. This change has implication for the various birds and mammals that feed on krill.