We’ve been doing modern limnological sampling to better understand why the haptophyte algae (the producers of biological thermometers) fare so well in our Greenlandic study lakes… it’s still a mystery.

We sit on a rubber boat (a Zodiac) making measurements and taking different kinds of samples. Have a look at this video to see us recover sediment samples from last season, and get introduced to some of the equipment we use to sample water, algae and sediment.

During the last few days we have taken the time to share results and evaluate our performance. The consensus is very positive: there is satisfaction from all parties for the work accomplished.

The scientists studying icebergs in this project are truly an interdisciplinary group. We look at iceberg physical properties, how they affect the physics and chemistry of the surrounding ocean water, and the consequences of those changes on the biota, microbes, phytoplankton, zooplankton, fishes and birds.

A group photo on the bow.

Carbon is the common denominator (or the currency) used by the different researchers to understand the flow of matter through the different components. Carbon is analyzed as gas (carbon dioxide or CO2), particulate and dissolved, as it moves from the atmosphere to the ocean surface and ultimately to the ocean floor.

During this cruise, instruments were tested and new ideas were generated on how to improve them. Methods of water collection, sampling approaches and data sharing schemes to optimize sampling around icebergs were successfully implemented.

A view of an iceberg off the back deck.

Results on the changes in water temperature and salinity due to iceberg melting were clear cut and shown on a scale useful to all science groups. Biological response was somewhat depressed, as expected at this time of the year when short days and low phytoplankton biomass cannot maintain rich marine communities.

We will be ready by next March 2009 to participate on a cruise to estimate the extent of iron enrichment by icebergs in iron-limited waters of the Southern Ocean.

We thank Raytheon Polar services and the crew from ECO (Edison Chouest Offshore) for excellent support during the cruise, in particular Captain Mike Watson and Marine Projects Coordinator Adam Jenkins. And special thanks to Ken Smith from the Monterey Aquarium Research Institute who organized the science (and the scientists) with great skill and dedication.

View of Punta Arenas as we return to port.

Everyone is busy trying to take that one last sample.

Me analyzing a sample under the microscope.

The last zooplankton net tow collected abundant gelatinous zooplankton, drifting animals whose bodies are almost entirely made up of water and have the consistency of gelatin.

The gelatinous zooplankton jellyfish, affectionately dubbed ‘eyeballs.’

Besides jellyfish, we have seen salps, arrow worms (chaetognaths) and comb jellies (ctenophores).

A ctenophore from a previous season at Palmer Station, Antarctica.

Phytoplankton maintain their position in surface waters through several mechanisms that increase buoyancy. Under stress, such as that provoked by low nutrient levels in the ocean at the end of summer, the phytoplankton cells sink at several meters per day.

Phytoplankton under the microscope.

Layers rich in phytoplankton can be found close to the ocean floor, becoming food for benthic animals. A portion of that carbon will be buried in the sediments and lost to the biosphere. Zooplankton swim up and down the water column, eating phytoplankton, and producing fecal pellets which sink tens to hundreds of meters per day, providing a very effective and fast transfer of carbon to the ocean’s depths.

Fecal pellets.

Icebergs can also release minerals, inorganic carbon, and various other particles of interest to characterize this unique environment. All of these different sinking particles can be caught and studied with the appropriate instrumentation.

Ken Smith, Brett Hobson, Alana Sherman and Paul McGill have built unique instrumentation called Langrangian Sediment Traps (LST), to collect the sinking particles around and below the icebergs. These traps are designed to sink below the iceberg, catching particles as they go, and to surface after a pre-determined period of time.

The recovery of an LST can be quite an adventure. High winds and high seas made yesterday’s recovery difficult. After searching for several hours the LST was found in sea ice late in the evening, thanks to Captain Mike Watson who saw it from the ship’s bridge.

Spotting the LST drone from the bridge.

Crabeater seals resting on a small ice floe.

Jake Ellena and Ken Smith are our bird surveyors. They count birds in flight while the ship is transiting between stations or during iceberg circumnavigation. Snow petrels are the most abundant of them; they are attracted to the iceberg, feeding on the zooplankton congregating within a few miles of the iceberg.

A Snow Petrel near Iceberg A43K.

Our sampling targets the study of the wildlife’s food source and the concept that birds and marine mammals are found in association with icebergs thanks to the physical and chemical modification of the ocean by the presence of the bergs. The icebergs enrich the water, promoting phytoplankton and zooplankton growth.

Ron Kaufmann and Bruce Robison have been monitoring some of this growth by using large nets to sample the macrozooplankton and micronekton around the iceberg. Salps (Salpa thompsoni) have dominated most of the samples at various distances from the berg. Many of these salps had highly colored guts, perhaps indicative of recent feeding, and representative salps have been analyzed for gut contents and pigments. Small phytoplankton cells, abundant at this time of the year, are preferred by salps.

One of the crustacean species that we are catching near Iceberg A43K.

Conspicuously rare in the samples have been large Antarctic Krill (Euphausia superba), though large numbers of young or juvenile krill have been collected. Krill typically feed on diatoms which are not abundant in winter.

The nets also contain large numbers of vertically migrating mesopelagic fishes as well as hyperiid amphipods, small krill and occasional large medusae.

Cassandra Brooks is a marine scientist and science writer based in California. She’s studied Antarctic marine resources since 2004 at Moss Landing Marine Laboratories (MLML) and with the Antarctic Marine Living Resources (AMLR) Program.

Cassandra Brooks first began studying Antarctic toothfish in 2004 as part of her master’s thesis at Moss Landing Marine Laboratories. Antarctic toothfish are large, deep-sea predatory fish found only in the ice-laden waters surrounding Antarctica. Biologists who were fascinated with their ability to live in these freezing waters were the first to study these fish. It turns out that Antarctic toothfish have special proteins in their bodies that act like anti-freeze to keep their blood from freezing, thus enabling the fish to live in the icy waters off Antarctica.

Commercial fishermen took notice of the Antarctic toothfish only in the last ten years when populations of its sister species, the Patagonian toothfish, became depleted. Patagonian toothfish are found in the northern waters of the Southern Ocean, off the tip of South America and around sub-Antarctic islands. Both species of toothfish are more commonly known by their market name “Chilean Sea Bass,” though they bear no relation to sea bass. The depletions of Patagonian toothfish were likely caused by the large illegal pirate fishery, which has been estimated at up to 70 percent of the total harvest of this species.

As the subantarctic waters where the Patagonian toothfish lives were overharvested, vessels moved further south, into the remote and pristine waters of the Ross Sea, Antarctica, in search of the Antarctic toothfish. The commercial catch of Antarctic toothfish has increased steadily over the last ten years, even though very little is known about the basic biology of this fish. Cassandra’s work focuses on life history and population structure of this species. Her goal is to provide information on their age, growth, and spatial distribution to the toothfish’s managing body (CCAMLR) in order to facilitate sustainable management of this large Antarctic species.

Antifreeze Fish

Some of the coldest ocean waters on earth, where temperatures fall below the freezing point of fresh water, are found in the Southern Ocean surrounding Antarctica. Nearly every fish on the planet would freeze to death if it tried to brave such harsh conditions. The Antarctic toothfish, however, thrives in this icy environment. How does it do it?

Antarctic toothfish have evolved remarkable traits that allow them to survive in sub-freezing waters. One of these traits is a slow heartbeat—a beat only once every six seconds. The main secret of these unique fish, though—who have a natural lifespan of 40 years and can weigh in at over 200 pounds when full-grown—lies in a special protein that acts like antifreeze. By making this unique antifreeze glycoprotein, the Antarctic toothfish are able to keep their blood from freezing. It’s a remarkable evolutionary solution to surviving in the frigid waters of the Antarctic.

One of the most amazing things about these Antarctic antifreeze fish is their corollary in the Arctic, where waters reach similar subfreezing temperatures. There, fish carry a similar but different antifreeze protein—evolutionarily distinct from that of the Antarctic toothfish. What this means is that fish at both ends of the planet evolved similar antifreeze survival strategies through completely different methods.
For more on this awesome evolutionary achievement, please visit our Origins site here.

Background on AMLR

The United States is one of 25 nations that are bound by the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR). CCAMLR is an international treaty, the aim of which is to conserve marine life in the Southern Ocean and to ensure the harvesting of marine resources is done in a sustainable manner without disrupting the Antarctic ecosystem. The United States Antarctic Marine Living Resources (AMLR) program is responsible for collecting scientific information that will be used to develop and support US policy regarding the conservation and management of the marine resources in the waters surrounding Antarctica. For over 20 years, scientists with the AMLR program have investigated the effects of krill, crab and finfish fisheries on the ecosystem, including the effects on seal and seabird populations. The Antarctic Ecosystem Research Division (AERD), located at the Southwest Fisheries Science Center branch of NOAA Fisheries, manages the AMLR Program.

When Cassandra goes to sea with AMLR, she primarily studies zooplankton under Dr. Valerie Loeb, a marine biologist at Moss Landing Marine Laboratories (MLML) and a contact scientist for AMLR. Valerie studies the abundance, demography, and distribution patterns of krill, and is head of the krill and zooplankton component of the AMLR program. Valerie and the AMLR crew study krill because these small (approximately 2–2.5 inches, or 5-6 cm) shrimp-like crustaceans are the most abundant and important food source in Antarctica. The whales, seals, fish, and seabirds in the Southern Ocean all depend on krill for their survival.

The zooplankton soup featuring all the major players: Krill (Euphausia superba), “T-mac” (Thysanoessa macrura), Euphausia crystallorophias (the krill-like ones that appear more orangeish/red), and “the angry one” Themisto gaudichaudii (black amphipod).

Zooplankton in the Southern Ocean are quite large when compared to their temperate water counterparts. Slow growth and delayed maturation result in a larger size in some Antarctic invertebrates, a phenomenon referred to as Southern Ocean Gigantism. This makes our job of picking the invertebrates from the zooplankton soup much easier. Amphipods can be in excess of 60-70 millimeters (but typically more like 10 mm); we have netted salps larger than 120 mm.

A particularly large Themisto gaudichaudii (predatory amphipod). From head to tail, he is over 20 mm.

Some of the amphipods and worms we find are voracious predators and actively hunt in the water column. Though they are small in relation to us, I can imagine the fear they instill in their prey. Themisto gaudichaudii, also known to us as “the angry one,” and chaetognaths, a type of arrow worm with large hooks and grasping spines for teeth, are particularly frightening. Even after the trauma of being hauled up in a net, dumped into a tray and crushed with tweezers, Themisto gaudichaudii still frantically grasp at anything they can get close to. Chaetognaths chomp with their bristly grasping spines at anything and everything, including other chaetognaths, their own body, and our skin if we let them. Though they are far too small to cause us any damage, they cling so hard to the unfortunate critters they manage to get a hold of that we have to rip them apart. No fun if you are a small euphasiid!

View from under the microscope of a Chaetognath worm (close-up of its grasping spines) and copepod, Pareucheata antarctica. (For a sense of scale, the copepod is only a couple mm in size.)

There are good reasons why we painstakingly identify and count individual zooplankton critters at the microscopic level (where we find most of the copepods and euphasiid larvae.) Zooplankton species assemblages and abundance are indicators of distinct water masses and allow us to determine how ocean currents change from year to year. Moreover, we can also detect long-term variation, including regime shifts (for instance, La Niña or El Niño) and climate change. Because krill are our primary focus, we still don’t know a lot about most of the other zooplankton species, including their role in the ecosystem or what the changes in distribution and abundance mean. Future studies hope to tackle this more.

Salpa thompsoni from the zooplankton catch. Salps can range in size from 4 mm to over 120 mm; these ones are about 40-70 mm.

I am on the zooplankton (the ocean’s small, drifting animal life) team and collectively we work 24 hours a day, 7 days a week sampling krill using an IKMT (Isaacs-Kidd Midwater Trawl) zooplankton net. We deploy the net off the back of the boat at designated stations and when the net comes up, we sort, identify, count and measure the krill as well as all the other zooplankton critters. We work in 12-hour shifts; I work the 8pm – 8am shift, and as you can imagine, that took a few days to get used to.

IKMT zooplankton net entering the water for sampling off the back of the vessel.
Photo by Lara Asato

The crew deploying the IKMT net.
Photo by Lara Asato.

Other teams on board sample for phytoplankton (tiny photosynthetic organisms drifting in the ocean), the primary food source for krill. Others spend their day watching for birds and mammals, the krill predators. Others study acoustics, which provide information about krill aggregations and biomass. We also deploy a CTD (Conductivity, Temperature and Depth) profiler to collect data on oceanographic variables, such as temperature and salinity. All of this is to get an understanding of the krill’s ecosystem and how that ecosystem drives their distribution and abundance.

Krill, (Euphausia superba) in a sorting dish after being hauled aboard in a zooplankton sampling net.
Photo by Lara Asato

And why do we care so much about krill to have a whole team of scientists dedicated to studying them? AMLR’s krill expert Dr. Valerie Loeb explains: “The whole ecosystem depends on krill. They are large shrimp-like crustaceans that form schools and abound in great numbers. Krill are a keystone species because they directly transfer primary productivity to energy in the system.” A host of predators depend on krill, including penguins, seabirds, fish, seals, as well as residential and migratory populations of whales.

The krill-filled cod end of the zooplankton net after a tow.
Photo by Darci Lombard

Me removing the cod end of the zooplankton net on the back of the boat.
Photo by Lara Asato

Krill are also harvested by humans. In fact, a few days ago, we saw three krill fishing vessels in the South Orkneys. The vessels were from Norway, Poland and Korea – evidence of this valuable international fishery. In the past, krill was primarily used as bait and as fish meal in terrestrial and aquaculture farms. Nowadays it is also harvested for direct human consumption and for pharmaceutical products, including omega-3 fatty acid supplements.

Darci Lombard and I count the microscopic portions of the zooplankton sample. Every zooplankton tow has inverts we can pick out with tweezers and count. Then there is the “small portion” of microscopic organisms which we subsample and count.
Photo by Mitch Meredith

Krill biomass estimated from our survey will be used by CCAMLR to set appropriate fishing quotas. Additionally, because AMLR has over 20 years of survey data, we can tease out environmental- versus human-induced change in krill distribution and abundance. This is of interest to CCAMLR because humans are in direct competition with krill predators. Our data helps them in their goal of allowing rational harvesting without harming the Antarctic ecosystem.

Corethron, a type of phytoplankton, highly magnified under the microscope.

A ball of corethron, less magnified under the microscope.

At every station of the LTER grid the B-045 group takes water samples to analyze for dissolved gasses, dissolved organics and bulk bacterial parameters. The amount of oxygen in the water can give us an idea of the amount of primary and secondary production occurring in the water column. Dissolved organic carbon is also an important parameter to measure because it is the amount of material available for bacterial consumption. We directly measure bacterial production using radio-labeled amino acids, which shows the rate of carbon utilization by the bacteria.

In addition, we preserve samples to measure the amount of bacteria in each water sample. This analysis is done with the use of flow cytometry back at our home institution, the Ecosystems Center, MBL. We also do experimentation onboard involving molecular genetics to look at the diversity of the bacterioplankton community. In this process, we filter water to concentrate bacterial cells to perform downsteam DNA analysis.

Our Microbial Biogeochemistry team. At top center, from left: Chip Cotton, Heidi Geisz, Erin Morgan, Aaron Randolph, and team leaders Matthew Erickson and Kristen Myers. At bottom center are images of the bacterial community, taken with a camera attached to a microscope aboard the vessel. At lower left, Aaron Randolph filters water to concentrate bacterial cells to perform downsteam DNA analysis. At lower right, Erin Morgan “pickles” a dissolved oxygen sample. At top right, Chip Cotton and Heidi Geisz inoculate a set of samples with the radio-labeled amino acid. At top left, an exuberant Heidi Geisz and Erin Morgan sample for dissolved organic carbon.

It has been a very successful and enjoyable cruise. While very busy the group has been able to enjoy several beautiful sunsets.

The LTER’s sampling grid covers inshore and offshore waters along the Antarctic Peninsula, where we see a broad range of organisms including jellyfish, squid, fish, salps, worms, and amphipods, among others.

A ctenophore: a creature similar to jellyfish but without any stinging cells. These populate cold waters in both Antarctica and the Arctic.

One of our dissecting microscopes, used in the analysis of these organisms, is equipped with a digital camera that allows us to take pictures of what we see. We decided to compile some of our favorites here with the magnification for scale.

In the upper left is a pteropod called Limacina. Pteropods (a name meaning winged foot) are similar to snails and slugs, only they have wings and swim around in the ocean. Limacina swim with a bat-like flapping motion of their wings (the “chinchilla ears” in the photo). Also of note is their mucus net used in feeding; a single Limacina, roughly the size of the “G” on your keyboard, can cast a mucus net many times its size in diameter. This net traps phytoplankton until the Limacina consumes the net: algae, mucus and all. This architectural feat was discovered by blue-water divers watching pteropods feed in the ocean far from land.

These closeups, taken through a microscope, are layered against a picture of the net tow being brought back aboard the ship.

At the top-center of the picture is a species of Protomyctophum, or Lantern Fish. The pearl-like spheres along its body are called photophores. Photophores are light-producing organs that typically line the bottom of a fish (though not only in fish, Euphausia superba has them too) in order to break up its silhouette, making it difficult for predators to identify them as prey.

In the middle of the picture is a very, very small starfish. To give you an idea of how small, the width of the forceps next to it is roughly 0.25 millimeters! This interesting pelagic (which is strange for the mostly bottom dwelling starfish) creature has shown up in two catches, hundreds of kilometers apart. None of us know exactly who or what it is.

The three pictures on the bottom are of a squid, a polychaete worm curled up next to a copepod (a small planktonic crustacean) and a group of Hyperoche amphipods. Amphipods are another group of crustaceans. This particular species is one of the more common amphipods found in the study. Note the large eyes! The squid and the polychaete, on the other hand, are rare finds. These photos offer a glimpse of the high diversity of small animals living in the Southern Ocean.