Weedlines: A Sargassum Research Blog

PS-18-07 Daily Log

July 16, 2018 (Day 8)*

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

Wow, it’s hard to believe we’ve been at this for 8 days now! Below is a summary of today’s activities aboard the R/V Point Sur, another outstanding day on the water.

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The camera rig in a patch of Sargassum with the R/V Point Sur in the background taken from small boat ops.

We really hit the Sargassum jackpot today. Thanks to some helpful guidance from our remote sensing team, by 0830 this morning we had located a region of the Gulf with very high Sargassum biomass, the most we’ve seen during this project by far. As we slowly approached the mats to pick a few nice sampling targets, we were greeted by large schools of fish–Triggerfishes, Filefishes, Amberjacks, other small tunas and jacks, and more. Just an amazing number of fishes, many of them adults, though there were quite a few juveniles as well. We were in the bluest of blue water, so they were easy to see, and we got to work!

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The ROV being deployed as fish swim nearby.

Our sampling ops proceeded well, including the CTD cast, water sample collection, and camera rig survey. The Sabiki rig fishing was so productive we cut our fishing time in half after collecting many juvenile (small and large) Amberjack species (Seriolaspp.). We conducted an ROV survey under one of the large mats and observed scores of fishes, including Tripletails, Mahi Mahi, and numerous Filefish and Triggerfish species. Although very hot today, the sea conditions were absolutely perfect, glassy smooth, so we decided to try our luck with the purse seine. After one set that didn’t quite work out, the second purse seine set collected a large amount of Sargassum, along with Sargassumfish, Tripletail, Rainbow Runner, Filefishes, and other species. A very nice haul–thanks to a lot of effort (kudos to everyone who made that happen!). We wrapped up our sampling for the day (and for this cruise) with an open water station, where in addition to CTD data and water samples, we collected more cool fishes in the neuston net, including larval Billfish, Flyingfish and Mahi Mahi, among others.

Purse seine

And that’s it. We have set a course for Gulfport and expect to arrive at our home port around 1800 or so on Tuesday evening. This will be the last daily report for this cruise, as tomorrow will be spent cleaning our gear, packing samples and equipment, downloading vessel data, and cleaning up the lab and state rooms for the next group coming aboard. Not nearly as exciting as the previous 8 days.

Fun

I want to thank the Captain and crew of the R/V Point Surfor another wonderful cruise; we certainly could not accomplish our work without you guys. It’s been a productive and fun cruise, as always. And thanks to our funding agency, the NOAA RESTORE Act Science Program, for making this research possible.

Crew

First Mate JD Ellington, Assistant engineer/deck operations Mark McMullan, Captain Nicholas Allen, Chief Engineer Josh Jansen, Marine Technician Josh Bierbaum, Chef Alex Forsythe

And thanks to everyone who followed along with us during this cruise and our previous cruise in May. We hope you enjoyed the blog. We’ll be on the water again 2019, so don’t forget about us. Between now and then, we’ll be working up our samples, processing data, and preparing manuscripts for publication. We also plan to attend several state and federal management meetings to update fisheries biologists on our research, and work with them to incorporate our findings into population assessments for managed species.

P.S. from the Chief-Scientist

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Frank.jpgI can’t express enough my gratitude to all of the young scientists aboard the R/V Point Sur during our cruises this year. They have worked tirelessly, without complaint, in summer heat and in the rain. They are diligent and serious about the work we are doing, and at the same time their good cheer and gumbo of personalities has made these trips some of the most enjoyable I’ve ever had. To go to sea on a large research vessel is, for some, a once in a lifetime experience. For this summer’s group of undergraduate interns, graduate students, research technicians, and postdocs, I sincerely hope this is not the case, and that they enjoy many such opportunities in the future, perhaps even leading their own cruises one day. Until then, you are always welcome to hop on board with me, anytime!

FJH

Weedlines: A Sargassum Research Blog

Estimate Sargassum wet-weight, nutrients, and pigments from satellite images

 

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Dr. Mengqiu Wang collects reflectance data from the Sargassum.

Sargassum moves around quite a bit, carried from place to place by winds and currents. Although she is not with us on this cruise (because she just successfully wrapped up her PhD defense!), Mengqiu Wang (USF) provides us with a look at how satellite imagery can help us locate and quantify Sargassum habitats.

 

Sargassum has distinctive pigment compositions, which control the reflected light intensity at different wavelengths or the “color”. The reflectance properties have been used to develop remote sensing algorithms to detect and quantify Sargassum from satellite images. However, currently we are only able to infer the area coverage or relative abundance, but not the associated wet-weight or biomass, which are very important for understanding their impacts on the ocean’s biology and chemistry.

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To derive Sargassum biomass from satellite data, field measurements of the Sargassum density (biomass per area) and the corresponding reflectance become necessary. During previous cruises, we measured the natural density of several individual Sargassum patches and estimated a mean value of ~ 3 kg/m2 by referencing to a 1 m2 quadrat.  We also designed experiments to measure the reflectance signals at different densities. These data were applied to build a model to link the remote sensing signal and Sargassum wet-weight. Generally, higher reflectance signal strength would indicate a larger Sargassum biomass density. Besides that, we also measured the nutrients and pigments concentrations per unit wet-weight in the lab with the Sargassum samples collected from the cruises. Using those relationships, we can calculate not only Sargassum wet-weight, but also their nutrients and pigments directly from satellite images.

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Weedlines: A Sargassum Research Blog

PS-18-07 Daily Log

July 15, 2018 (Day 7)*

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

Well, we’re getting close to the end of the cruise, with just a few days left before we head back to Gulfport. Below is a summary of today’s activities aboard the R/V Point Sur.

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The science team getting prepped for some sabiki rig fishing. (Photo: Eric Haffey)

We were able to stay in the general vicinity of yesterday’s sampling region, and find Sargassummats to sample during the morning. The mats were scattered about, with no obvious pattern in their distribution, so we chose the biggest we could find and collected the usual samples. Sample collection and processing went smoothly, and we were able to collect many small juveniles in the mats, including Sergeant Majors, Tripletail, Amberjacks (Seriolaspp.), and Bermuda Chubs, among other species. Larger juvenile Amberjacks were collected during our Sabiki fishing set, so a nice size range from this station. We decided to do two more neuston tows, as there were numerous mats to survey, and they were relatively small and manageable.

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A quick neuston dip before we drifted into a large vessel buffer zone.  (Photo: Zabe Premo)

If you’ve never been to the northern Gulf of Mexico, it’s hard to express how busy this body of water can be. Thousands of oil and gas platforms and structures are located off the coasts of Texas, Louisiana, Mississippi and Alabama, and they are serviced by all manner of survey and supply vessels. Often times these operations have buffer (safety) zones around them, and we had to work around one such vessel today. Our Sargassum mats kept drifting along (as they are want to do) and into one of these buffer areas. It took some zigging and zagging, Shipbut we were able to follow the weedlines and get everything done. So a long morning extended into the afternoon, but all in all a great day of sampling Sargassum(thanks to the tireless team of scientists we have on board, and the crew, who are always willing to help us get the job done).

We made our way south to waters relatively free of Sargassum to sample an open water station. Again, all went well, and the neuston picked up several cool larvae, including a Mahi Mahi, a few Flyingfish and a nice larval Billfish! Love seeing those guys!

Overnight we will steam further south to what we hope will be a great ending to our Sargassum sampling (the last day, Tuesday, will be for traveling home). We have our fingers crossed for an area that should have high Sargassumbiomass according to analyses by our remote sensing team. Stay tuned to see how the cruise wraps up!

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Due to the physical processes that aggregates the Sargassum, trash is often found associated, as well. Check out our blog on micro plastics! https://hernandezfishecologylab.com/2018/06/07/weedlines-a-sargassum-research-blog-8/  (Photos: Carla Culpepper and Olivia Lestrade) 

 

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.

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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.

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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!

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

 

Weedlines: A Sargassum Research Blog

PS-18-07 Daily Log

July 13, 2018 (Day 5)*

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

Happy Friday the 13th from the Gulf of Mexico! More good luck for us during our Sargassum cruise; read below to catch up on all the action.

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A majority of our day is spent rinsing through the sargassum at this table to ensure we get all the vertebrates, invertebrates, and any unique items, biological and manmade. (Photo: Carla Culpepper)

Well, we’ve come full circle in our sampling ops so far–literally. We’ve had success locating Sargassum  around the edges of the recently formed eddy that is separated from the Loop Current, and today was no exception. We cruised around a bit this morning looking for Sargassum, and in the process spotted a few whales in the distance (always a treat). Being relatively free of Sargassum for a change, we decided to start the day with an open water station, which went very smoothly (neuston net tow, CTD cast, and water sample collection). We then continued our search for Sargassum, and picked up quite a convoy of (Pantropical Spotted) dolphins along the way, until we arrived at a location with numerous large Sargassum  mats!

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A Great Barracuda seen exploring the Sargassum   mats and underneath the boat for a majority of the afternoon (Photo: Carla Culpepper)

Again, our sampling went smoothly. We collected a large amount of Sargassum, which included several small juvenile Tripletails and Sergeant Majors, among other species. The camera rig survey, CTD cast, and water collection proceeded without a hitch. Once again our Sabiki fishing was an adventure; many juvenile Amberjack (Seriola spp.) were collected, as well as a few Bluerunners. No large Mahi Mahi to contend with this time, but there was a very menacing Great Barracuda patrolling the weedlines, as well as several larger tunas/mackerels (we couldn’t see them well enough for an identification).

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Small boat ops discussing with the vessel the best techniques to deploy the plankton purse seine. (Photo: Valeria Nunez)

Afterwards we spent some time with the ROV again and conducted a second video survey using this method. Lastly, we spent the last daylight hour practicing the deployment/retrieval of our plankton purse seine, a gear we’ve yet to use so far during the cruise. We have some kinks to work out here, but we hope to use it before the cruise is over.

 

 

 

Purse seine

The science team and crew watch as small boat ops practices deploying the purse seine. (Photo: Captain Nicholas Allen)

Having circled around the eddy, we’ve decided to head to a new region in the hopes of collecting Sargassum  and associated fishes under different environmental conditions. So we’ve set a course towards the birdsfoot where the Mississippi River enters to the Gulf of Mexico. There are usually strong “tide lines” here, which are density fronts formed where the freshwater from the river meets the sea. So stay tuned to see how it goes!

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The top map (from NOAA AOML) shows the geostrophic currents in the Gulf of Mexico for July 13, 2018. The small arrows show current directions, and the background colors denote the dynamic height (in cm). Note the large, clockwise eddy that has recently separated from the Loop Current. This is the feature we’ve been sampling so far during this cruise, as indicted in the bottom map (orange dots are Sargassum  stations; blue dots are open water stations).

Weedlines: A Sargassum Research Blog

Nutrients / Chemistry

Water chemistry and nutrients are another important component of our project. Zabe Premo (PhD student, USM) explain some of the sampling we do aboard the R/V Point Sur as part of the Sargassum project.

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The CTD collects water as near the Sargassum as possible.

As part of the Sargassum study, water samples are collected at surface (within the Sargassum feature itself), at 1.0-meter depth, and at chlorophyll maximum depth. Surface samples are obtained using a beta-sampler, while the two other depths are collected using niskins affixed to the CTD unit deployed from the vessel. Water is filtered in the field shortly after collection using a glass syringe and filter to remove large particles and detritus in the water sample. Filtered water is then immediately frozen onboard to ensure nutrients dissolved within the water do no volatilize or decompose before they may be analyzed. Upon return to the laboratory, the samples are analyzed for nitrate, nitrite, ammonia, phosphate, and dissolved carbon. As this study aims to evaluate the foodweb structure associated with Sargassum features, it is essential to understand primary production and nutrient availability within the system. In open water locations of the Gulf of Mexico, large portions of the water column are often nutrient-limited. This gives the water the

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The science crew retrieves the water samples collected from the niskins affixed to the CTD.

distinctive cobalt blue hue as there is minimal primary production (phytoplankton) in many areas. Macronutrients such as nitrogen, phosphorous, and carbon in the open water are derived from biogenic pathways where chemical species are utilized and become bioavailable to sustain discrete ecosystems such as those found surrounding Sargassum features. By sampling the water for these compounds, we seek to better understand nutrient cycling within the Sargassum features and to compare these processes with those found in open water without Sargassum present and at the chlorophyll maximum layer. The chlorophyll maximum is a subsurface layer of high primary production usually associated with the thermocline of the water column and the depth at which sufficient sunlight penetrates to support photosynthetic processes.

 

Nutrients and Chemistry

The Nitrogen Cycle
From https://www.enn.com/

Weedlines: A Sargassum Research Blog

PS-18-07 Daily Log

July 12, 2018 (Day 4)*

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

Another great day on the water for us! Seas have remained calm and we’ve managed to avoid pop up showers for the most part so far. And there’s plenty of Sargassum in this part of the Gulf at the moment. Here’s another brief summary of our sampling ops during Day 4 of our NOAA RESTORE cruise.

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Graduate student, Courtney Stachowiak, and Dr. Frank Hernandez observe the ROV footage as it runs a transect under a Sargassum line. (Photo: Eric Haffey)

Overnight we cruised across the newly formed eddy that’s separating from the Loop Current, and found the western edge by morning, along with new Sargassum mats to sample. The team is really in a rhythm now; everyone jumps into action and knows what to do, like a well-oiled science machine! The CTD cast, water collection and camera rig deployment went smoothly, though the winds did pick up a bit and our camera system drifted out of the mat at some point during the end of the recording period.

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Valeria Nunez catches a juvenile fish on the sabiki rigs. (Photo: Carla Culpepper)

Our neuston two went very well, and we picked up a number of juveniles, including a nice Tripletail and a few Sergeant Majors. But much like yesterday, this mat was loaded with juvenile carangids, and we had quite a time fishing the Sabiki rigs. But today it wasn’t so easy, because we were competing with a school of larger Mahi Mahi that would chase these smaller fishes as we reeled them in. The water was so clear, you could watch the race to the boat, and on more than one occasion we watched as a Mahi ripped a small Amberjack right off our hook, often leaping out of the water to do so. Still, we easily caught at least a dozen or so Amberjacks and Bluerunners, even after losing a few to one of the top predators in the Sargassum community.

Mahi

A group of Mahi Mahi feed on the juvenile fishes around the sargassum mat during a sabiki rig sampling event (Photo: Carla Culpepper)

We searched for an open water site to sample, but again we were well-surrounded by Sargassum weedlines and mats. So we opted to do another Sargassum station. Having located a nice mat, we were prepping for a neuston tow when we spotted a juvenile sea turtle–or at least his/her back end as it plunged under the Sargassum and dove away. We decided to steam to another mat (there were plenty) to avoid any incidental catch, and we were able to collect another neuston net sample, along with a CTD cast and water samples. We stayed with this set of Sargassum mats until dark, then deployed a pair of light-traps in the Sargassum before setting a course for the northern edge of the eddy.

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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.

Weedlines: A Sargassum Research Blog

Stable Isotope Ecology

One of our project goals is to understand the food web associated with Sargassum. Check out the blog post below from Zabe Premo (PhD student, USM) detailing how stable isotopes can help us understand feeding ecology in marine ecosystems.

Stable isotopes have countless applications in physical and biological sciences, as well as medical research, forensics, and Earth and environmental systems. Simply speaking, atoms are comprised of protons, neutrons, and electrons. Combined, protons and neutrons form the nucleus of an atom, while electrons orbit the nucleus.  Each element has a set number of protons contained in the nucleus, for example, carbon has six protons and nitrogen has seven protons, while the simplest element, hydrogen, has one. Generally, most elements have the same number of neutrons and protons, but sometimes, additional neutrons are present, thus increasing the mass of the atom but not changing the element itself. Atoms with the same number of protons but differing numbers of neutrons are isotopes of one another, and may be radioisotopes, where the isotope radioactively decays into a new element by eliminating a radiogenic particle, or stable isotopes, where the structure of the nucleus of the isotope does not change over time.

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PhD student, Zabe Premo, sorting for inverts for later stable isotope analysis. (Photo: Dillon Lab)

Stable isotopes are useful in ecological systems because they can be employed as tracers to evaluate a range of interactions. In the Sargassum study, stable isotopes of carbon and nitrogen are used to assess where organisms associated with the Sargassum features are getting their food (carbon), and who is eating whom within the foodweb (nitrogen). Samples that are collected encompass microorganisms, algae (including both S. natans and S. fluitans), invertebrates, and fish at a range of life stages. Back in the laboratory, samples are analyzed with a mass spectrophotometer to determine the relative ratio of “heavy” isotopes to “light” isotopes. In the case of carbon, the common (and also “light”) isotope is 12C, meaning it has six protons and six neutrons, while the “heavy” isotope is 13C, meaning it has six protons and seven neutrons. Biological processes such as respiration that use carbon-based molecules can fractionate the isotopes, wherein the “light” and “heavy” isotopes are separated due to differing energy potentials in their atomic structure. The result is that the tissues of organisms will have a particular isotopic ratio that can be used to evaluate environmental conditions, food sources, and regional variation, among many other parameters.

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A fish blood sample collected by the Dillon Lab for further stable isotope analysis. (Photo: Dillon Lab)

Similarly, because organisms eat one another, nitrogen isotope fractionation is evident with increasing trophic level, with “heavy” nitrogen (15N; seven protons and eight neutrons) abundance increasing as predators consume lower trophic level organisms and nitrogen forms portions of muscle tissue and amino acids. A portion of the Sargassum study will look further into the behavior of nitrogen isotopes in this system through compound-specific isotope analysis (CSIA). As nitrogen flows through a food web, it is used to form amino acids, and by analyzing nitrogen isotopes of these amino acids, a better understanding of biosynthetic pathways is achieved, and it is possible to refine the relationships between trophic levels. This study considers not only muscle tissue of fish, but other tissues including blood, plasma, and liver which have different turnover times in the body, and can demonstrate shorter-term feeding habits (versus muscle which has a lengthier turnover time).

Stable Isotopes

From: https://oceanbites.org/
The basic plot shows that with increasing trophic level in a food web, both of the “heavy” isotopes of carbon and nitrogen increase. By looking at the isotopes of different tissues of the same organism, the goal is to see if we can pinpoint on which trophic level predators are consuming. The goal is to better understand the food web dynamics within this system, and to evaluate recruitment of fish to Sargassum features.

 

Weedlines: A Sargassum Research Blog

PS-18-07 Daily Log

July 10, 2018 (Day 2)*

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

After a great first day at sea, we were excited to do it all over again. We drifted overnight along with the Sargassum, and after breakfast (waffles!) and cup (or two or three) of coffee, we got to it!

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The science team and the vessel crew enjoy watching as the designated anglers use sabiki rigs to catch juvenile Sargassum associated fish. (Photo: Carla Culpepper)

Our intent today was to collect 2-3 small-volume neuston tows, in order to examine sampling variability within a single Sargassumfeature. However, we were a little overzealous and grabbed quite a bit of Sargassumon the first tow (oops). So we spent much of the morning processing that first sample. Again, relatively few fish, especially compared to last summer. The scientist in us always wants more fish, but understanding variability in Sargassum biomass, distribution and fish associations is a big part of this project, so these data will be very helpful in our assessment of these parameters.

After lunch, we set out the camera rigs to record under the Sargassumcanopy, and conducted hook-and-line sampling, which yielded a few juvenile Hardtails (Bluerunners) and Amberjack (Seriola sp.). One of the Amberjacks was host to a pair of parasitic isopods which were attached to its tongue (!), which is very cool or very gross, depending on your point of view. We’re not sure which species of isopod these were, but we know that some isopods actually feed on the tongue until it falls off (by depriving it of blood flow), then functionally replace the tongue by attaching itself to the bottom of the fish’s mouth. Again, very cool!

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Pair of parasitic isopods in the mouth of an Amberjack caught with the sabiki hook and line rigs. (Photo: Angie Hoover) 

We had enough time to conducted a second neuston tow, after which we steamed a kilometer or so away from this area to an ‘open water’ (free of Sargassum) station for a CTD cast, water collection, and more net tows. Our large open water net sampler (Methot Frame Trawl) unfortunately did not collect the desired juvenile fishes, but did collect a number of larval fishes, including eel leptocephali, tunas, and barracudas. The ‘open water’ neuston followed, but during the tow we encountered stray clumps of Sargassum, so the sample was a bit of a mixed bag.

Our plan was to then head back to the large Sargassummats for a last round of sampling with the light-traps after dinner. But, we were not able to locate them again (?!). Finding ourselves in relatively open water again, we decided to do a night tow with the large frame trawl. Again, we encountered stray clumps of Sargassum, quite a few large jellyfish (Aurelia), and lots of cool larval fishes and invertebrates, including many eel leptocephali, an Angelfish (Pomacanthidae), a Pearlfish (Carapidae), and many more.

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Barracuda larvae caught in open water neuston net (Photo: Frank Hernandez) 

After processing this last sample, we set a course further south for the edge of the Loop Current, where our remote sensing team has identified likely areas of high Sargassumbiomass. We hope for another successful day!

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Pair of tuna larvae caught in the open water neuston net (Photo: Frank Hernandez)