Weedlines: A Sargassum Research Blog

PS-18-07 Daily Log

July 14, 2018 (Day 6)*

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

Greetings all! Thanks for checking up on us on your weekend. Today we took a chance, and left the great fields of Sargassum circling around the eddy to search other another region with different environmental conditions for comparison. It was a risk that paid off…eventually.

We cruised northwest overnight to search along the “tide lines” that usually form near the Birdsfoot Delta, where the the muddy waters of the Mississippi reach the Gulf, and water color changes from brown to green to blue as different water masses mix together. It is common for Sargassumto get entrained along these density fronts, and we had great success last summer sampling in this region.


Zabe Premo collects water from the niskin bottles on the CTD. (Photo: Josh Bierbaum) 

Today, however, things looked bleak for a while. The morning search included several squalls, 30 knot winds, and overall poor conditions for searching out Sargassum. We tried to zigzag along regions where we anticipated these frontal regions where green water meets blue water, and we did this for much of the day. All day, in fact, until finally we came across a surface slick with a Sargassumweedline at around 5:00 pm. Though late in the day, we were restless from all the sitting around and jumped right to work, collecting CTD profile data and water samples along the convergence zone, followed by two neuston tows. We collected quite a few juvenile fishes, including Bermuda Chub, Gray Triggerfish, Amberjack, Sergeant Majors, Orangespotted Filefish, and a Porcupinefish, among other species. We collected several Atlantic Bumper juveniles as well, though we suspect they were less associated with the Sargassumthan they were with the large Aurelia jellyfish that ended up in our nets as well.


Left: Tripletail (Lobotes surinamensies) Middle: Amberjack (Seriola sp.) Right: Planehead filefish (Stephanolepis sp.) (Photos: Frank Hernandez) 

After the sun had set, we spent some time watching a large barracuda feed on flyingfishes and small remoras that were lured towards us by the halo of lights from the vessel. Great entertainment, and a cool way to end the day.

So a whole day of scanning the horizon paid off in the end. A great job by the science team!


A Remora and a Flying fish swim under the light of the boat. (Photo: Eric Haffey) 


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