Weedlines: A Sargassum Research Blog

PS-18-07 Daily Log

July 11, 2018 (Day 3)*

*Note:these will be posted on a one-day delay, i.e., this report is for yesterday’s activities.

Hi Sargassum fans, glad you’re following along with us. Here’s another brief summary of our sampling ops during Day 3 of our NOAA RESTORE cruise.

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Intern, Alex Sandercock, and Marine Tech, Josh Bierbaum, deploy the floating camera rig using small boat ops. (Photo: Eric Haffey)

As luck would have it, we happened upon a relatively large patch of Sargassum first thing in the morning (thanks to the alert eye of mate, J.D. Ellington, during his night watch). This patch was located along the eastern edge of a large eddy that recently separated from the Loop Current. Sampling went very smoothly; the CTD cast, water sample collection, and camera rig survey were all completed by approximately 0900. A neuston tow was conducted, and again yielded relatively few fishes. However, we noticed many of the juvenile fishes were relatively large (and fast) juvenile carangids (jacks), which are not likely to be collected in a neuston tow. But these fishes are the perfect targets for the Sabiki rig fishing, and a great example of why we use multiple gear types. A 30-minute fishing set (with four anglers) yielded over a dozen juvenile Amberjacks (Seriolasp.), over 50 Bluerunners, and a few other species (e.g., Bermuda Chub, Rainbow Runner)–a great haul! A subsample of these were worked up for blood, liver and muscle tissue (for later stable isotope analyses), and will be worked up further for diet and age/growth analyses as well. Before leaving the Sargassum station, we experimented a bit with a small ROV that was loaned to us by our colleagues in the USM Department of Marine Sciences. The team practiced a bit on smaller Sargassum patches, and worked out a few kinks. Hopefully we’ll have time to do a standardized ROV survey later during the cruise, now that we’ve got things (more or less) figured out.

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The sabiki anglers proudly pose during the largest hook and line haul of the trip thus far. (Photo: Carla Culpepper)

 

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Dr. Dillon collecting water from the CTD. (Photo: Eric Haffey)

After collecting all of our Sargassum station samples, we were a bit unsure as to where to go to get away from Sargassum for an open water station. We noticed that we were quite surrounded by small weedlines and scattered clumps. We continued south until the surface waters seemed relatively free of Sargassum, so we stopped and collected CTD profile data and water samples. A neuston net tow was attempted, but we collected a good bit of Sargassumin the sample. We set a course towards the west with the hopes of encountering more open water in the center of the eddy feature. In the evening we conducted one more neuston net tow in relatively Sargassum free water, and collected many cool zooplankton and larval fishes, including larval Lanternfishes (myctophids) and a larval billfish!

After wrapping up the deck ops, we continued on our course to the west. Our goal is to cross the eddy feature overnight and arrive on its western edge, where we hope the north-flowing currents will have more Sargassum mats to sample.

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