How can I identify a Dall's porpoise?
Dall's porpoises are beautiful! Though individual animal coloring varies slightly, Dall's porpoises are easy to identify as they are mostly black with white along their sides, on the top half of their dorsal fins and on the trailing edge of their flukes. Dall's porpoises mature to around 7 feet (2.1 meters) long and have 19-23 spade-shaped teeth. When swimming, Dall's porpoises leave a characteristic splash called a 'rooster tail.'
Back to the reason for being out here.
Quoting the Chief Scientist Dr. Mark Wells, "The driving reason for this research is ocean sequestration of atmospheric CO2. The ocean is both a sink and a source of CO2 to the atmosphere. But the big questions now are how the balance (mainly source, mainly sink) has changed in the past, and how it might change in the future. It is the HNLC regions of the oceans that are the most important in this aspect, by current thinking. In essence, HNLC regions will become more of a sink for atmospheric CO2 if the growth of large phytoplankton (like diatoms) is enhanced over that of smaller cells. Normally when larger cells grow and all the nutrients are used, their physiology begins to deteriorate and they begin to sink. The same thing happens to smaller cells, but they sink much much slower. What this means is that larger cells tend to be degraded in subsurface waters, while smaller cells are degraded in surface waters. As a result, larger cells transport carbon (taken up as CO2) from surface waters to subsurface ocean waters and out of contact with the atmosphere. Because surface waters are in a type of equilibrium with the atmosphere, the CO2 removed from the surface by sinking cells is replenished from the atmosphere, drawing down atmospheric CO2. Now obviously a bunch of single cells sinking isn’t going to remove much CO2, but if you total up the area of the oceans that are HNLC regimes (30-50% of the ocean surface), and go for many years (centuries), then you have the possibility of a significant drawdown of atmospheric CO2 -- a reverse of the greenhouse effect. The “removal” of atmospheric CO2 would not be permanent because ocean circulation eventually brings deep waters to the surface again, and the CO2 would be released back to the atmosphere. But this process takes several centuries so it is thought that that enhanced ocean productivity likely has been involved in climate change during the geologic past. Back to the project at hand here, if dust deposition to the subarctic Pacific were to increase naturally, it could result in more CO2 transport into the deep ocean. We are studying the mechanisms that might underlie such natural (gentle) changes.
Anybody still there? If you have questions, please send them. I will seek an explanation and relay the information.