The Colonial Ascidians Die Back?

Launching the Hela ROV (Photo: N. Balcom, CT Sea Grant)

The early autumn skies were clear and the air crisp as the NOAA Undersea Research Center at the University of Connecticut returned to survey Long Island Sound (LIS) with its Hela remotely Operated Vehicle (ROV, right). The survey was part of an ongoing assessment of the impacts of the invasive sea squirt, Didemnum, on LIS supported by NURC, Connecticut Sea Grant and UConn's Department of Marine Sciences.

Survey Broadcast Live on the Web

The survey was also broadcast live onto the Web using wireless broadband ship to shore networks that NURC has been developing over the past few years. Both broadcasts were archived as progressive Windows Media (WMV) downloads and are accessible on our website. Depending on your internet connection speed, please click the appropriate bandwidth (LBW=128Kbps, MBW=256Kbps, HBW>512Kbps) below to download and watch undersea video from the Fishers Island Sound.

Morning Webcast (video only) (LBW, MBW, HBW)	Afternoon Webcast (video only) (LBW, MBW, HBW)
Morning Webcast (w/slides)	Afternoon Webcast (w/ slides)

The survey revisited the deeper, gravel habitat of eastern LIS that Didemnum prefers to compare the level of colonization that had occurred following the May, 2006 survey. The two-day survey coincided with a UConn Marine Sciences Open House that included visitors from NOAA National Marine Fisheries Service (NMFS), Connecticut Department of Environmental Protection (CT DEP) and the Environmental Protection Agency. Both Webcasts featured narration by the University of Connecticut's Professor Bob Whitlatch who has been studying the Didemnum invasion in LIS for the past six years and by NOAA NMFS scientist Bob Reid who has been studying the Didemnum invasion of Georges Bank since 2003. The morning Webcast also featured commentary from Tim Keeney, NOAA's Deputy Assistant Secretary for Oceans and Atmosphere, while the afternoon featured CT DEP Commissioner Gina McCarthy.

Image of the seafloor taken during the September cruise showing the small white Didemnum colonies and a yellow sponge. (Photo: NURC-UConn)

NURC-UConn conducted four dives over two days, September 26th and 27th to survey for the sea squirt. A July, 2006 diver survey revealed large areas of the sea floor blanketed with the sea squirt (see video clips). Interestingly, during the September survey only small, white colonies were seen. The reasons for the observed reduction in coverage of the bottom from the July survey could be: 1) we were not at the exact location of the July dive (sea squirts can be very patchy), despite good navigation indicating we were, 2) potential physical disturbance by high seas caused by tropical storm Ernesto a few week previous to the cruise or 3) a natural senescence or die back of the sea squirt that had already begun to occur. More surveys will be needed to follow the dynamics of this invasive species and continue to monitor its impacts on Long Island Sound.