WHAT DID WE DO TODAY?

What a difference a day makes!  Our weather was absolutely tropical today. We have been working at our Station #16 throughout the day. We are protected by surrounding islands in relatively shallow water (about 500 m). We have had the luxury of working steadily throughout the day, without the down-town necessitated by waiting for workable weather.

So what did we do today? We collected zooplankton in IKMT and MOCNESS tows, and then worked quickly to observe and measure the living organisms and also prepare, process, and preserve samples. Here is a sampling of our work on board the LM GOULD.

A) When the MOCNESS is recovered after a tow, 3 or 4 people – including scientists and technicians – are needed on deck to wash down the nets while they hang of the stern gate, and then lift the cod ends over the gate, where they are detached from the net.

B) Each of the nine cod ends is brought into an “aquarium room” with running sea water, where the zooplankton sample can be processed. Paola is using a seawater hose to wash the cod end after the sample is removed.

C) The catch from one net: we have been sampling dense swarms of Southern Ocean krill in the surface layers (above 50 m), especially during the night. The bright red color is characteristic of krill; if you look closely you can see that their guts look greenish – they have been grazing on phytoplankton. For more about other zooplankton we have caught, see Melissa Patrician’s blog for today at http://aleslab.blogspot.com/.  Be warned, it’s a quiz!

D) Each step in the processing of samples is recorded, with separate logsheets for each procedure or analysis. We keep track of all the collection information (called “metadata”) for each sample. Here Melissa M. is keeping track of specimens removed from the samples.

E) The sample is pourted from the cod end into a device that divides the sample into equal halves, so they can be shared between the science teams and preserved for different types of analyses. Joe is holding the “box splitter”, while Paola pours out the sample.

F) The box splitter is rocked back and forth to separate the sample into two chambers, which can be poured off separately. Joe is splitting the net sample.

G) Each half of the sample is washed into a sieve to remove the sea water. The zooplankton can then be washed into a plastic sample jar.  Paola demonstrates our sieving technique, with a seawater wash bottle.

H) One half of the sample is preserved in formalin for later identification of species and determination of their abundance or concentration in the volume of water sampled by each net. Melissa preserves samples in buffered formalin, working in a fume hood in the ship’s hydrolab.

I) Living specimens of species of interest – including salps, krill, jellyfish, comb jellies, chaetognaths, amphipods, and many other species of diverse animal groups – are removed from the samples for special analysis. Ann is measuring individual alive-and-kicking krill inside the “freezer van” on the LM GOULD, before flash-freezing them in liquid nitrogen for genetic analysis.

J) The specific gravity of specimens of a variety of zooplankton groups is being measured by Joe Warren’s team. Katie is setting up the experiment in a ship’s “cold van”. For more explanation about this study, see Joe Warren’s blog for November 14th at http://aleslab.blogspot.com/.

We can only hope for more lovely work days like today, but the weather forecast suggests that the Southern Ocean may have something else in store for us. Here we go again!

-- Ann Bucklin (University of Connecticut)

WHY ARE WE HERE?

Figure 1. Changes in krill and salp densities over time: a) Krill density in the SW Atlantic sector; b) post-1976 krill density in scientific trawls; c) 1926–2003 circumpolar salp data. Figures from Atkinson et al. (2004)

We might ask ourselves this question on a day like today, when the winds have sprung back up, whipped up the waves, thrown ice bergs in our path, caused the ship to pitch and roll ceaselessly, and stopped us from carrying out the sampling we had planned for today. But in fact, this question – in a larger context – is important to many of us who have spent much of our lives studying the ocean, especially the Southern Ocean. 

We are here in the Western Antarctic Peninsula (WAP) region of the Southern Ocean because it is a bell-weather region for climate change and global warming. A 2004 paper by Angus Atkinson and others summed it up well:  

“The western Antarctic Peninsula is one of the world’s fastest warming areas, and (atypically for the Southern Ocean) winter sea ice duration in this sector is shortening. Key spawning and nursery areas of krill are thus located in a region that is sensitive to environmental change. Deep ocean temperatures have increased, and a circumpolar, pre-1970s decrease in sea ice has been indicated at several locations. The regional decrease in a high-latitude species with high food requirements (krill) coincides with an increase in a lower-latitude group with lower food requirements (salps). However, as the mechanisms underlying these changes are uncertain, future predictions must be cautious. These changes among key species have profound implications for the Southern Ocean food web. Penguins, albatrosses, seals and whales have wide foraging ranges but are prone to krill shortage.”

Figure 2. Southern Ocean food web. Image British Antarctic Survey

The vulnerability to climate change of the Southern Ocean pelagic ecosystem – and the special

Figure 3. Top: The Southern Ocean krill, Euphausia superba (Photo Uwe Kils). Center and bottom: The Southern Ocean salp, Salpa thompsoni, solitary and aggregate forms (Photos Larry Madin, WHOI)

vulnerability of krill - is of deep concern to oceanographers and climate scientists. Krill are a keystone species for this ecosystem, meaning they are pivotal to the nexus of relationships among species that live here and are connected in a “who-eats-who” framework, known as a food web. The Southern Ocean food is pretty simple compared to many other ocean regions. There are fewer species and fewer trophic steps to the top predators or “charismatic megafauna” (seals, whales and porpoises) that many people know and love best. This cruise is focused on salps and krill, and our goal is to help ensure that many people know and love these creatures best – or at least as much – too. To help make our case, here are the major protagonists of our story, alive and well and looking their charismatic best (Fig. 3).


-- Ann Bucklin (University of Connecticut)


Citation for quotation:

Angus Atkinson, Volker Siegel, Evgeny Pakhomov & Peter Rothery (2004) Long-term decline in krill stock and increase in salps within the Southern Ocean. Nature 432: 100-103

Picture of the Day - November 15, 2011

Early morning sun shines on the ice cliffs of Clarence Island, Antarctica.
Photo Paola G. Batta-Lona

EUREKA – WE CAUGHT A SALP!

The Southern Ocean pelagic ecosystem is known to be highly variable among different Antarctic regions and to show dramatic variation among both seasons and years. This year, many people have commented on the unusual amounts of remaining ice. Perhaps Austral Spring is late this year. Our studies will help analyze this variation in species composition and abundance over time and space. Prof. Joe Warren (Stony Brook University) and his students – carrying out another salp project on our cruise – are measuring “biovolume” of our plankton catches. At SBU, other students will determine the abundance of different zooplankton species in the preserved samples. These data will be compared with results from other Southern Ocean regions and years.

Figure 1. Living Southern Ocean krill soon after capture.

Our zooplankton catches have been rather smaller than we expected. – but with many different species. Important for our study, we have sampled dense patches of juvenile and adult Southern Ocean krill (Euphausia superba; Fig. 1). Krill are a keystone species for the pelagic ecosystem here and dominate the zooplankton assemblage in biomass and abundance. They are an important species for us too, since they are important player in the dynamic balance between salps and krill in the Southern Ocean food web. Our goal is to understand the population dynamics of both species in relation to the zooplankton community and environmental conditions in the Southern Ocean.

Figure 2. Station locations for the Salp Survey cruise, including sites in the Drake Passage (Stns 4-11) and Bransfield Strait (Stns 14-21). We have completed work at stations with red numbers.

Back to our unfolding oceanographic adventure! Yesterday the winds blew at 30 – 40 kts as we steamed SE in the Drake Passage from our Stn 11 (Fig. 2), where we had completed work in a patch of good weather amidst days of howling winds and high seas. We arrived at Stn 12 during the morning, but the seas were still up and swells were coming from two directions. We waited until conditions calmed down and went to work in the early evening.

Figure 3. Fifteen seconds of fame for the first salp caught on our cruise! With the star is its biggest fan, UConn PhD student Paola Batta-Lona. Photo Ann Bucklin

Eureka! We caught our first salp in Net 4 (which sampled from 200 – 100 m) in our fifth MOCNESS tow of the cruise. We preserved the salp separately to give it some special attention (Fig 3). We hope to find many many many more salps! And we may catch a bit of luck with weather, with forecasts for winds between 15 and 20 kts for the next 24 - 48 hrs in our area. That should give us time to sample our northern-most stations and head back south through Bransfield Strait, where we should find some protection from the westerly winds. Salps, Ho!

-- Ann Bucklin (University of Connecticut)

ARE WE HAVING FUN YET?

The Southern Ocean in shades of blue and gray. Photos Peter H. Wiebe

Today finds us standing by near our Station #12, which is NE of Elephant Island. We are waiting on the weather to start working at this site, which is at the northern end of our sampling region and therefore of particular interest to us. Farther north means farther along in Austral Spring, so perhaps our favorite species, the Southern Ocean salp, will be more abundant. In fact, we will be happy to see our first salp on this, our sixth day of salp hunting!

So here we sit, waiting for the weather to be nicer – a lot nicer! Last night, we had sustained winds at 50 kts, with gusts to 60 kts. The motion of the ship in this weather makes lying down hard work. Sitting in a chair, working in the lab, and eating a meal are even more challenging.

So, are we having fun yet? Well, not everyone is. Sometimes the changing motion can make you seasick even after you get your “sea legs”. (After a few days, you get used to having the floor rock and roll under you. In fact, you can get so used it, you can get “land sick” until you get your “land legs” back). But I am in fact having a bit of fun. For whatever reason, since my first cruise as a postdoc at Woods Hole Oceanographic Institution in 1980, I have loved it best when the seas kick up and toss us around. I suppose it makes me feel connected to the forces of nature. And the ocean is lovely when it gets churned up: the waves become a kaleidescope of colors – all shades of blue and grey here in the Southern Ocean. Elsewhere in the world ocean, there are shades of turquoise, green, and blue.

One problem with weather like we have had on our Salp Survey cruise is that we can’t actually get much work done. The weather decks are closed since the waves crash over them regularly, so we can’t easily reach the aquarium room or our laboratories in the “freezer van” lashed to the back deck. We certainly can’t put anything over the side or collect any samples in this weather.

Everyone finds something to do (see Melissa Patrician’s Nov. 13th blog at http://aleslab.blogspot.com/). Some of us watch movies, read books, play video games, sleep more, and/or keep working. And some of us – including me – enjoy the ride.

-- Ann Bucklin (University of Connecticut)

Picture of the Day - November 13, 2011

Photographs don't seem to capture the huge swells driven by high winds blowing over the vast reaches of the Southern Ocean. The blue-gray color of the ocean, with petrels careening in the fierce winds, is typical of the past two stormy days.

Picture by Peter H. Wiebe.

WHAT LIVES BENEATH?

The ocean pelagic habitat has been divided vertically into five zones: epipelagic, mesopelagic, bathypelagic, abyssopelagic, and hadopelagic (Table 1). Most sampling is done in the top 200 m, called the epipelagic zone. A great deal of sampling has been in the top 1,000 m or through the mesopelagic zone. Little sampling is typically done below 1,000 m, in the bathypelagic (1,000-4,000 m), and much less even deeper.

Table 1. Depth zones of the pelagic habitat, with total volume in the world oceans in millions of cubic km [Vol (106 km3)] and percent volume (% Vol) of the total. Note that most of the ocean volume is considered bathypelagic (from Hedgepeth, 1957).

The vertical partitioning of the ocean, including the Southern Ocean, is very important, since the different zones have quite different environmental and habitat charateristics – and sometimes very different zooplankton species composition. Although some planktonic species vertically migrate each day, visiting the surface waters during the night and hiding from visual predators in the deep dark waters during the day, other species live in the deepest layers of the ocean all the time. In general, the very deep sea is thought to be a region of low biomass, low abundances, and high diversity. Since the deep layers are rarely sampled, they are also a zone of discovery – of new species and unsampled populations of known species.

For our project, our particular interest is in investigating earlier reports of very deep populations (below 2,000 m) of our target salp species in the deep waters of the Western Antarctic Peninsula region. We wonder whether there are unsampled deep-living populations of this species, or whether perhaps the species migrates between the surface and such great depths. Our molecular genetic and genomic analyses are designed to help answer this question.

For our salp survey, we are sampling from surface to as the near the bottom as possible. For stations deeper than 1,000 m, we sample to 1,000m, except for stations deeper than 2,500 m, when we sample to that depth. We are sampling zooplankton with a complicated instrumented net system, called a MOCNESS (Multiple Opening-Closing Net and Environmental Sensing System; Fig. 1) that provides data in “real time” (immediately) through a conducting cable to a ship-board computer.

Figure 1. The MOCNESS is launched from the LM GOULD. You can see the electronic instrumentation in pressure cases at the top and cod ends (PVC buckets) at the end of the nine nets. Photo Peter H. Wiebe

Yesterday we steamed NE in the Drake Passage and arrived at our Station #11 during the afternoon. We are particularly interested in this sampling area, which is offshore and among the deepest of our stations (estimated depth 3,069 m), so we asked that the LMG remain near the location so we can wait for better weather. We (Ann, Joe, and Peter) headed for bed, with a request to be waked up when conditions were workable. Amazingly, we got our “weather window” - winds below 30 kts (see Fig. 2) – and got the wake-up call at 3:30 am. Work could begin!

Figure 2. The red line shows wind speeds over the previous 24 hr at 12:00 Noon GMT or 9:00 am local time on Nov. 13th.

After an initial CTD cast, we launched our first “deep tow” of the cruise. The MOCNESS went over the side about 6:30 am and was recovered at 11:45 am. The net system had traveled 5,000 m in about five hours. Throughout the tow, environmental data (temperature, salinity, particulates, chlorophyl) and net information (depth, angle of the net, volume of water filtered) are displayed on the ship-board data acquisition computer (Fig. 3). During the uphaul, eight nets are opened and closed successively, sampling discrete depth zones of the ocean.

Figure 3. MOCNESS data acquisition screen, showing net trajectory (with different nets in different colors), environmental parameters, and position during a 2,500 m tow. 

We were happy to have completed this deep tow successfully and felt fortunate to have a long enough patch of good weather. This came after a very bad two-day stretch of wind and sea that prevented work. During the tow, we kept a close eye on the wind speed and also the barometer, which was moving from low to higher pressure as the storm center moved away. During the tow, the barometer peaked and the winds dropped to below 20 kts for a short time and then the barometer began to fall again. Unfortunately, our target species, the salp, Salpa thompsoni, was not present. However, salps are colonial animals that can form large patches or blooms very quickly. When we do find salps – and we remain quite optimistic that we will – we will likely find LOTS of them!

-- Ann Bucklin (University of Connecticut) and Peter Wiebe (Woods Hole Oceanographic Institution)