The scientific part of our expedition has officially come to an end. In just a few days, we’ll be stepping off the ship – some of us heading deeper into New Zealand, others (like me) beginning the journey home. But just because we’re finishing the cruise doesn’t mean the work is over! Right now, we’re busy sorting, counting, and analyzing all the creatures we collected over the past few weeks. That means I finally get to share a little peek into the world of Tanaids!

During the NBP25-01 cruise, we collected an impressive 746 tanaidaceans! All of them belong to the suborder Tanaidomorpha. Most were caught using an EBS – 671 individuals, to be exact – while the rest came from a dredge (48) and a Smith-McIntyre Grab (27). 

I’ve sorted them into 12 families and 16 morphospecies, but those numbers might change once we’re back on land with proper lab conditions. These crustaceans are so tiny that identifying them correctly requires a high-quality microscope and a stable surface – which is pretty hard to find when the ship is constantly moving!

What’s especially interesting is that most of the tanaidaceans we found were juveniles. We only came across two individuals in the manca-I stage (Neotanais sp.), a few Nototanais males, some ovigerous females, and one swimming male from the family Pseudotanaidae.

I’m hoping these specimens will be the foundation for some exciting future analyses – including my PhD research, which I’ll be diving straight back into as soon as I return to Poland!

Kamila Głuchowska
University of Lodz

NBP25-01 is coming to an end. Today we had the last 'events' of the cruise. Each activity ranging from a run of multibeaming to image the sea floor to deploying an instrument like the epibenthic sled is given an event number. Today we had our last sled samples with event numbers 257 and 258, for a total of 24 successful EBS casts!  These samples were taken as we began our transit north, which enabled us to expand the geographical area we sampled during the cruise. Because the ice is really starting to get thick in the Ross Sea, finding a suitable site for an EBS deployment has gotten tricky. 

This morning, we thought we found a suitable site but keeping the ship at a steady 0.5 knots without churning up big chunks of ice that could hit the EBS proved impossible. We steamed further north and the Captain and First Mate identified a good site with cooperative ice and a depth of around 540 meters with nice and flat bathymetry. Whereas we usually collect a sample from the EBS and sort it carefully under the microscope, picking out nearly all the animals and sorting them taxonomically before taking photos and preserving specimens, we didn't have that luxury today. Instead, we took a quick look at the sample, picking a few interesting animals out and then bulk preserved the rest in cold 95% ethanol for sorting at a later date. This isn't ideal because many animals lose their color or shrivel after being preserved, but we will be getting out of the ice soon and needed to pack up the lab and have everything secured in case there are rough seas. We repeated this process again this evening at another site with cooperative ice and a depth of around 497 meters.

We have about 24 hours before the ship leaves the protection of the ice, when we could experience rough seas. Today we continued taking down the lab and packing up all of our supplies and tomorrow we will spend the day cleaning the lab, packing samples, and filling out the necessary paperwork to get our lab supplies and samples home safely.

The IcyInverts team is overall thrilled with the outcome of the cruise. We got to see a lot of amazing animals and collected some really valuable samples for our research. In the coming days we'll post more about the process of getting our samples home and next steps for our various projects.

Dr. Kevin Kocot
University of Alabama

When sea ice or rugged terrain make it too risky to deploy the epibenthic sledge (EBS), we rely on a more compact and ice-friendly tool: the Smith McIntyre Grab.

If you’ve ever played the claw game at an arcade, you already have the basic idea. The grab is lowered to the seafloor with its jaws open. When it makes contact with the bottom, the jaws snap shut, capturing a box-shaped sample of sediment along with all the small animals living in and on it. We then bring the grab back to the surface and carefully sieve and preserve the sample for further study.

While the EBS excels at sampling fauna living on or very near the surface of the sea floor, the Smith McIntyre Grab is ideal for collecting more quantitative, sediment-based samples—especially in spots where the EBS can’t go. It’s also a safer option in icy conditions, where a stray chunk of sea ice could damage the EBS on its way up or down. Today we used the grab to sample the top of a seamount. It returned a beautiful sample with lots of diversity including some burrowing animals not normally collected with the EBS.

We checked out the original paper describing the design of the grab and were amused to see that the version on the NBP is virtually identical to the original design from 1954!

These grab samples are rich with hidden biodiversity—tiny crustaceans, worms, mollusks, and other invertebrates that help us understand the complexity of Antarctic benthic ecosystems. Stay tuned as we dig deeper (literally and figuratively) into what we find!

Dr. Kevin Kocot
University of Alabama

The major goal of the IcyInverts team on this cruise is to collect specimens of cumaceans and other peracarid crustaceans for two National Science Foundation-funded projects (see: here and here for details). However, given the expense and effort it takes to sample in Antarctica, we try to preserve specimens of as many of the organisms that come up in our nets as possible. Another group my lab studies is the worm-like aplacophoran mollusks (see previous IcyInverts blog posts about this group from our 2023 and 2020 cruises and a video on why we study these animals). When not photographing and processing peracarid samples, aplacophorans have been another major focus of mine. Today's post is about a different invertebrate distraction, though.

One really exciting thing that happened was the collection of dozens of colonies of the pterobranch hemichordate Cephalodiscus hodgsoni. Check out a blog post by Mike Tassia from our 2020 cruise to learn more about these weird animals here. Pterobranch hemichordates are fascinating because they offer a unique glimpse into early deuterostome evolution. These small, colonial, tube-dwelling animals are relatives of acorn worms and share features with both echinoderms and chordates, making them key to understanding our own evolutionary history. Despite their significance, pterobranchs remain poorly known, with many species yet to be described and their biology still largely mysterious. Their unusual body plan, suspension-feeding lifestyle, and rarity in collections make them especially intriguing to evolutionary biologists and invertebrate zoologists.

I was really excited to see so many colonies come up in the dredge and rushed nearly half a 5-gallon bucket of colonies inside to get them into cold water. The colonies were *teeming* with animals! Below are some photos and details on how I isolated zooids (individuals from the colony) and preserved them for future studies. We're pretty busy just sampling the peracarids but this was an exciting find, if a distraction.

You never know what you'll find in Antarctica!

Dr. Kevin Kocot
University of Alabama

After weeks of work, we now have a clear picture of heat flow in the Terror Rift System. We measured heat flow at 52 locations and found an average value of 94 mW/m². Let’s break down what this means and what’s next.

What Do These Numbers Mean?
Heat flow tells us how much heat is escaping from inside the Earth. Our value of 94 mW/m² is high, suggesting that the Earth's crust is thinner here, allowing more heat to escape. This is common in rift zones where the crust is stretching and magma moves closer to the surface.

How Does This Compare Globally?
To put it simply:

• Normal ocean heat flow is around 70-90 mW/m².
• Young, active areas like mid-ocean ridges can exceed 200 mW/m².
• Older, stable ocean crust shows lower values of 40-50 mW/m².
  

Our measured heat flow is higher than typical ocean crust but not as extreme as mid-ocean ridges. This tells us the Terror Rift is an active region but not as hot as newly forming crust.

What Needs to Be Corrected?
Even though our values look good, a few things could influence the results:

1. Ice Sheet History
   Ice sheets have come and gone over this region, changing the heat structure. We’ll need to correct for these effects.
2. Sedimentation
   Fast sedimentation can bury heat signals or distort the values. We’ll model these effects back onshore.
3. Water Flow
   Pore water moving through the sediments can change heat flow. We’ll check for any signs of this.
   

Refining the Data Onshore
Back onshore, we’ll combine our data with geophysical models, sediment records, and ice sheet histories. This will help us fine-tune the heat flow values and ensure we get the most accurate picture.

Why This Matters
These corrected values will help us better understand how the Terror Rift System is evolving. They’ll also refine models of crustal stretching, magmatic activity, and even improve predictions of geothermal resources in the region. Plus, they’ll contribute to better Antarctic climate models by showing how heat moves beneath the ice.
Stay tuned as we continue to explore the fascinating secrets hidden beneath the seafloor!

Dr. Florian Neumann
MARUM, University of Bremen

When you're a researcher in Antarctica entering the colder months, you're told that the sea ice is going to change rapidly as you approach the Austral winter. You can look at satellite imagery showing the ice form in past seasons - but to witness it firsthand is still surprising!

At the end of February, the sea surface was mostly pancake ice, which is flat, circular plates of ice. Then, as March set in, the ice thickened fast, turning into a solid, stable sheet. This happens as temperatures drop and winds change, but the speed of the transition was still fascinating.

The Antarctic Circumpolar Current (ACC) plays a huge role here. As the world’s strongest ocean current, it influences ice formation by moving cold water and shaping temperature patterns around the continent. For marine life like seals and penguins, thicker ice means more stability. For researchers, it can limit access to sampling sites and complicate fieldwork. Deploying gear and navigating frozen-over areas makes for fluid plans as the expert crew navigate in the Ross Sea. Watching this shift reminds me how much the environment controls what we can study and how we do it.

Even with the ice thickening, we've been very lucky to have 18 successful EBS deployments and to have collected over 6,000 cumaceans!

Victoria Vandersommen
University of Alaska Anchorage

We’re down to our last two weeks of research and have already collected over 30 sediment cores! Most of these are gravity cores, reaching up to 2.5 meters long, with some piston cores stretching beyond 3 meters. Once collected, we process each core by taking sediment samples for various analyses. The sediment itself will be used for stable isotope measurements, sediment methane analysis, and radiocarbon dating.

​Porewater — the water between sediment grains — is extracted using syringes and rhizon samplers, which carefully pull porewater out of the sediment. This porewater will be analyzed for sulfate, sulfide, chloride, and nitrate. All analyses, except for isotopic ratios and radiocarbon dating, are performed on board.
We are using three main instruments on the ship: a gas chromatograph, an ion chromatograph, and a spectrophotometer. The gas chromatograph measures methane in sediment; the ion chromatograph measures nitrate, sulfate, and chloride; and the spectrophotometer measures sulfide. Before each run of samples, we carefully prepare standards to ensure accuracy.

All of these measurements will help us better understand the carbon cycle and the presence of methane beneath the seafloor. Today, we’ll begin coring again, and we’re hopeful we’ll recover even longer cores!

Hannah Organ
Texas A&M University- Corpus Christi

Sorry for another lapse in blog posts! We've been getting an EBS sample nearly every day lately (yay!) but that leaves little time for much else. We're really happy with our success in sampling and have been getting some great photos of really interesting animals (more soon). Here's a video 'tour' of one of our sieved EBS samples. After we sieve the material that comes up and pick out any large animals, we scan what's left under the microscope to pick out smaller animals with floppy forceps or a Pasteur pipette and sort them into little dishes on ice so they stay nice and cold while we sort.

Dr. Kevin Kocot
University of Alabama

March 19th is Taxonomist Appreciation Day, which recognizes the work of taxonomists responsible for classifying and naming organisms, a foundation for understanding and protecting biodiversity. 

In an age of advanced technology and genomic breakthroughs, some might wonder why traditional taxonomy and biodiversity studies still matter. The truth is, despite our ability to sequence DNA at an unprecedented scale, we still need to know what we are sequencing. Understanding biodiversity isn’t just about collecting data; it’s about making sense of the living world and ensuring we can recognize, describe, and classify organisms, potentially before they disappear forever. Nowhere is this more critical than in Antarctica, a region that remains one of the least explored and most rapidly changing ecosystems on the planet. The Southern Ocean is home to a surprising diversity of marine invertebrates (and other organisms) and many of these organisms live here and nowhere else. Many species of small marine invertebrates remain undescribed, and without taxonomists, they may never be formally recognized. Without proper species identification, we can’t track biodiversity changes, study evolutionary relationships, or make informed conservation decisions.

Taxonomy is considered by some a “dying art,” with fewer experts being trained in the meticulous work of species identification and classification. This gap in expertise threatens our ability to document biodiversity effectively. While molecular tools offer powerful insights, they cannot replace the foundational work of taxonomy. DNA sequences are only meaningful when tied to properly identified specimens, and without skilled taxonomists, that critical link is lost. Training the next generation in these skills is essential for continuing this work. Expeditions like ours expand our understanding of life in Antarctica but also provide invaluable hands-on experience and training for not just the student members on our team, but all of us. Moreover, working with a team of invertebrate zoologists with different taxonomic expertise has been fun because we can all teach each other something. I've been learning a ton about cumaceans from my shift-mate Victoria, for example.

This cruise reminds us that the unknown still exists, and many exciting organisms (like the undescribed cumaceans mentioned by Victoria in a previous blog post) and interactions (like the tanaid parasite mentioned by Kamila in yesterday's post) are just waiting to be discovered. Every new species described adds to our understanding of life’s complexity and adaptation to the frigid waters of Antarctica. Ensuring we have experts to carry this work forward is just as crucial as the discoveries themselves. Without taxonomists, we risk losing not only species but the knowledge needed to protect them.

Dr. Kevin Kocot
University of Alabama