For the first time, Rasmus joins us on the blog!

Rasmus and Nancy

My name is Rasmus Swalethorp and I am a postdoctoral researcher at Scripps Institution of Oceanography, UC San Diego. I am a biological oceanographer with a particular interest in the ecology of planktonic organisms. Up until now most of my research has been done in the Arctic and Antarctic and this was my first research cruise to the Gulf of Mexico.

Fishing for copepods in the sea ice in the Artic Ocean

Compared to the polar seas it was astounding to see the number of planktonic species that lived in the Gulf. While, I am used to only seeing about tens of different species of fish larvae or copepods (small planktonic crustaceans), in the Gulf I was amazed to see hundreds. This high species richness leads to very complex ecosystems that my colleagues and I are working hard to disentangle!

A lovely bluefin tuna (Thunnus thynnus) larvae collected during our survey

This is the second cruise aimed at understanding what makes up a good habitat for larval Bluefin tuna (BFT) to survive and grow. We want to be able to tell where to find these habitats and how much will be available in the future ocean. Much of my research has focused on baby fishes, the larval period of a fish’s life. This is the time when fish, are the most vulnerable to starvation and predation. Therefore, it is also considered to be the period most critical to recruitment: which is the number of fish that make it to adulthood and reproduce themselves someday. Understanding what is needed for a larval fish to survive is of particularly importance to management of commercially exploited fish such as Bluefin tuna.

After all what would the world be without sushi?

That’s where my expertise comes at play. I study what they eat. The more the larvae eat, the faster they can grow to improve their hunting capabilities and to avoid being eaten themselves. So, how do we determine a good larval tuna habitat? First, we need to know how much food is available to the larvae, and then which sources of nutrients are sustaining the food chain sustaining the larvae.

Mike L. and Ramus recover and rinse the ring-net
that has sampled the zooplankton (prey of BFT)

You may imagine that these guys are just little eating machines consuming everything available around them. But despite being ferocious predators, we have found that they are actually quite picky with what they eat. So to determine the availability of larval tuna “food,” we first need to figure out what the larvae are actually eating. This is done through meticulously by dissecting the tiny stomach and intestine of the larvae under a microscope to analyze their diet. As many of the prey are crustaceans, they are difficult to digest, (imagine digesting a crab with its shell, ouch!), so we can identify the species and size based on the undigested remains. By comparing this diet information with what is collected in our zooplankton nets we can see which zooplankton the larvae prefer to eat and how much food is available to them.

We are also studying their feeding habits by looking at their Nitrogen (N) signature. What is a Nitrogen signature? We look at the two naturally occurring isotopes of N (that is different variants of N). This is done in specific amino acids, the building blocks of proteins that make up the body tissues of the fish larvae. The less common 15N isotope is heavier than the common 14N. This weight difference means that 15N assimilated from the food is moved around the larval body and ultimately excreted as waste products at a slower speed relative to 14N. As a result there is a buildup of 15N compared to 14N in the larvae relative to their food.

Nitrogen atoms

Because we know the amount of 15N in the prey, and that the buildup increases at a constant rate for each level of the food chain, from algae to herbivorous zooplankton to carnivorous fish, we can determine how high up the food chain the larvae are.

Some larger zooplankton collected by our ring net

This method gives information on what the larvae have been feeding on the past days to weeks, while looking at the stomach contents only tells us what they have eaten over the last few hours. Also this method gives us clues on other potential preys, such as smaller unicellular protozooplankton that have soft bodies and are rapidly digested and therefore cannot be seen in the stomachs analyzed under the microscope. By looking at 15N we can also tell from where the N is coming from that is taken up by the algae at the bottom of the food chain. We can see this by looking at certain amino acids in the larval tuna where there is no buildup of 15N. Therefore, these amino acids reflects the composition of the N taken up by the algae so if e.g., there is very little 15N compared to 14N it means that the plants are taking up N2 from the atmosphere, and if there is more it means they are taking up Nitrate brought up from the deep.
I am now back in the lab and I can’t wait to start analyzing all the tuna larvae we collected to unravel the secrets of their diet.

NF1802! May the tuna be found today!

Fish eggs

Hello and welcome back to another year of our Nancy Foster Chronicles! This time we are well into Episode 2 of our NOAA RESTORE Project "Bluefin Tuna Ecology." Please check out last year's posts particularly the Return of the tuna!

Top: NOAA Shiptracker map of transit
around Florida
Bottom: Four NOAA Ships meet off the
Dry Tortugas!

Our survey started in Jacksonville, FL, and did a fun U-shaped track around the Florida Peninsula until we reached our study destination: the grand Gulf of Mexico. We even sailed past several other NOAA ships doing work in the area (NOAA Ship party!) to include the NOAA Ships Okeanos Explorer (EX), Oregon II (R2), and the Pisces (PI)! The NOAA Ships fleet support science in multiple fields including oceanographic, fisheries, and atmospheric research.

Join us for another adventure on NOAA Ship Nancy Foster!

It's been a week already, and we are now in the Northern Gulf of Mexico searching for the elusive bluefin tuna larvae. They have been hiding from us, but we are relentless and will keep searching! Our strategy is to target some favorable habitat which is usually in between oceanographic features.

I hope you learn something new during our journey and feel free to ask questions!

We are back home! Last post from the Chief Sci

Scientists and crew sign the NF1703/04 NOAA Corps flag 

First of all thank you for following our research expedition by reading our blog! My name is Estrella Malca and I was the chief scientist for this survey (NF1704) aboard the NOAA Ship Nancy Foster. What does that mean? Each project has a designated person that takes a leading role on the logistical, scientific and reporting aspect of the entire survey. 

One last selfie!
Estrella (Chief Sci) and Samantha (Senior survey tech)

I love to figure out the 'tetris' of things, so this year's cruise has been challenging but fun! Why challenging? Well, usually we have 6 months+ to prepare for our surveys: buying equipment, supplies, assigning scientists and volunteers to participate, and most importantly, securing any relevant permits as well as communicating with the ship's officers and crew about the multiple operational aspects of our project at sea. However, because of our very recent NOAA RESTORE project selected for funding, we had just two months to get a brand new project planned, signed and delivered on time! Without the rest of the science team, there is no way we can come out here and successfully achieve all of our research goals and deliverables!


We had the pleasure to continue to collaborate with several of our partners and also obtained new research connections!

NF1704 Leg 1 scientists

NF1704 Leg 2 scientists

Estrella and Niki deploy our very last satellite tracked drifter

Here is a list of our NF1704 accomplishments!! We were quite busy this  past month as you can see!

ü  500++ Tunas collected, more than 600 specimens individually measured at sea

ü  90 CTD casts: Depths were (300m, 500m, 1500m, and 2500m). The sensors we used on the CTD included temperature, oxygen, salinity, chlorophyll-a and CDOM, conductivity, PAR.
ü  Continuous measurements of currents (ADCP) from Key West to Progreso and to Miami

ü  Continuous measurement of flow through (TSG) from Key West to Progreso and to Miami

ü  7 SVP Drifters were deployed

ü  546 Flow cytometry samples (phytoplankton, bacteria, water column abundance)

ü  72 Elemental Nitrogen (N₂)-fixing organism samples

ü  6 casts with PAR (Photosynthetically-Active Radiation) sensor

ü  207 Microbial Abundances and Biomass samples

ü  95 Sediment Trap Flux samples

ü  78 Thorium concentration profiles (dissolved + particulate)

ü  354 Primary Production and Nitrate Uptake

ü  226 Deckboard Incubations for nitrogen utilization rates

ü  120 Shipboard Nitrate Concentrations

ü  57 Deckboard Incubations for δ¹⁵N.

ü  130 Nutrient Profiles for NO₃^- + NO_2,^-PO₄^3- and isotope analyses (δ¹⁵N and δ¹⁸O)

ü  95 Mesozooplankton Biomass and Grazing

ü  48 Growth and Grazing Rate Profiles (8 experiments x 6 depths)

ü  279 Phytoplankton Pigments fluorometric Chla,

ü  210 High-performance liquid chromatography  samples

ü  19 ring net tows (100m)

ü  136 net tows (25m): 120 Bongo-90 (240 jars) & 16 Mini-bongo net tows

ü  16 Mesozooplankton and 16 microzooplankton samples

ü  120 Live-sorted plankton samples
ü  95 specimens selected for genetic analysis
*   40+ Open House attendees. Our outreach event welcomed our scientific counterparts, students, professors, and fishermen in Progresso, Mexico

We hope that our projects will fill in a lot of the gaps about the biogeochemical ecosystem in the Gulf of Mexico as it relates to bluefin tuna research for the Western Atlantic stock. Our results will be shared with local and regional stakeholders like NOAA, ICCAT, among others. Soon, we will get started working up the data! Stay tuned and read our posts!

Group selfie, navigating into to the port of Miami

Featured today: LTJG Niki Norton

Today’s post features LTJG Nikita "Niki" Norton, and officially welcomes her to the FORCES Lab family! Niki is the current "Florida Bay Operations Officer," replacing LTJG Aras Zygas.  As a part of the NOAA Commissioned Officer Corps, she operates sampling platforms to facilitate scientific research and provides logistical and administrative support to NOAA’s mission.  She shared with the blog: 

Niki  records the flowmeter data into our logsheets

"For the last three years, I was assigned to the NOAA Ship Bell M. Shimada out of Newport, Oregon, conducting fisheries surveys from Vancouver, Canada all the way down to San Diego, CA.  Along with the responsibilities of being Navigation Officer and Medical Person in Charge, my primary duty was to “drive” the 210’ Fisheries Survey Vessel every day for 200+ days a year

Niki and Loni on the back deck, waiting to deploy the CTD

"Many of the sampling techniques that are routinely performed by research groups on the West Coast to collect plankton are exactly the same as those conducted by the FORCES lab to collect larval fish! 

"This included Bongos, Neustons, MOCNESS, and CTDs on many of the projects.  We performed extensive mid-water stern trawls with a net the size of a football field to catch fish like Pacific hake and sardine. We followed and tagged endangered Resident Killer Whale pods and acoustically monitored beaked whales at 4000m depth.  The remainder of the year, the ship completed Remotely Operated Vehicle (ROV) transects and hydrographic missions in the Farallons and Channel Islands.

Niki and Estrella deploy a satellite tracked drifter

"While many of the operations may be the same, this new job with the Southeast Fisheries Science Center is quite different - as is the scenery!  Rather than the whipping cold wind of the Pacific Northwest, the hot sun in the Caribbean and Gulf of Mexico is one of my favorite parts of the job. With the FORCES Lab, I get to work "on deck" to deploy and recover gear, wash down nets, assist with station planning, and see the plankton and water samples we catch up close! 

NOAA Ship Nancy Foster, Brewers Bay, USVI

"When I am not underway as a scientist, I work in the office to ensure that the lab has everything they need logistically to sail each year by assisting with cruise planning and administrative budgeting.  Now that the first year of sampling has come to a close, I am very excited to see what new projects I will get to be a part of and hope to use my background in reef fish ecology and microbiology to explore new research with the FORCES lab – while getting ready for next year!"

Girl Power! The women behind the science in NF1703!
Top (L-R): Sarah H., Niki, Trika, Sarah P.
Bottom (L-R): Kristen, Vanessa, Jess, Alexis

Niki on the bridge

Featured Scientist: Michael Landry

As we wrap up this year's survey, the first of two annual research surveys in the Gulf of Mexico for the NOAA RESTORE Act Science Program, we'd like you to get to know the PI from Scripps Institution of Oceanography, Professor Mike Landry! Read on as he describes his research and our cruise goals in his own words!

"I am a biological oceanographer. I have been on many ocean research expeditions over the years (since the 1970s), but never on a cruise in the Gulf of Mexico, never on a NOAA ship and never with fisheries scientists trying to understand a specific fisheries-related problem. So this particular cruise is special and a new learning experience in many respects. At the same time, it is also familiar. What we have investigated on past expeditions is how plankton food webs in different areas of the oceans function under different environmental conditions in order to understand the “rules” of why systems vary and how they respond to change. Our hope in this project is to apply the techniques that we have developed and the results from past experiences to characterize the unique aspects of the Gulf of Mexico habitat that lead to rapid growth and success of larval bluefin tuna (why do momma tunas migrate vast distances to spawn in only few small places in the ocean?) so that fisheries scientists might be better able to predict how they might be affected by future ocean changes.

Above: Groups of water bottles to
be sent to different depths
Below: Our filtration set up -
6 bottles at once!

"In this project, we are taking two approaches to studying food-web relationship and rates. One is experimental, involving direct measurements of community composition, productivity and nutrient uptake by phytoplankton, the microscopic plants of the sea. We also measure the consumption (grazing) of phytoplankton by zooplankton, the slightly larger but still pretty small protozoa and small animals that comprise the first 2-3 steps of the ocean food web. This is the “what is there,” "what are they doing,” and “how fast are they doing it” part of the study. Phytoplankton often go through one or two generations (cell divisions) per day, and they get eaten almost as fast as as they divide, so the tricky part of these experiments is separating the two rates (production growth and grazing loss) that are going on at the same time. We have a technique for this, which involves dilution of the grazing impact (using filtered water, changing the encounter frequency of predators and prey) in some of our experimental bottles. It is also important that we run our experiments under natural conditions of underwater light and temperature, so all of our experimental bottles that contain the plankton that we collected at different depths are put in net bags and attached at same depth to a line underneath a free-floating drifter float that we track by satellite for a day before picking up and exchanging bottles for a new batch of experiments. After a lot of filtering, preservation or freezing, and later analysis in our lab on shore, we should have a pretty good picture of how productivity and nutrients are moving through various routes in the food web to get to the specific zooplankton prey that bluefin tuna larvae like to eat.

Tom (L) and Mike (R) attach bottles to the sediment trap array

Mike (L) and Aki (R) hunt for BFT using microscopes onboard

"In the second approach to this study, we will use the tuna larvae themselves to tell us where they reside in the food web and what is the main source of nutrients (nitrogen) for primary production. This information resides in the nitrogen isotopic composition of the amino acids that make up the proteins of the tuna larva muscle tissue, which varies with the source of nitrogen (N2 gas for nitrogen fixation versus nitrate from deep water upwelling) and the number of predator-prey steps that the nitrogen has taken to get to the larvae, starting from phytoplankton. This sounds complicated, but the isotope analysis is easier to do than all of the experiments that are needed to assemble the food-web picture. One of our goals is to see if results from these two approaches agree, which has never been done before for any system because the isotope approach is so new. If this works out, it would validate using the isotopes in future studies, or also to look at changes in food-web structure and nitrogen sources that may have already occurred with climate change, using the muscle tissues of fish samples that have been taken in the past and preserved in museum collections."