Plants of the Sea

Today we finished the 3rd of our “process stations” which are aimed at getting a more in-depth understanding of what influences the living creatures in the ocean at various locations. Some of the most abundant and most important sea creatures are phytoplankton. They are the tiny (microscopic!) photosynthetic plants that live in our seawater and form the base of the oceanic food web: phytoplankton are eaten by zooplankton such as krill, who are in turn eaten by fish, whales and penguins.

Oscar Schofield (Rutgers U.) and his team are on board to understand both the distribution of these phytoplankton and what controls their growth. There are many types of plankton, and light levels are one of the ways they differentiate their niches.  At each station his group sends optical sensors into the upper water column to collect data on light absorption and scattering, which is used to identify who is living where. By calibrating these measurements against satellites in space, we hope future satellite data can be used to predict phytoplankton community composition. We already use satellites to measure sea surface temperature and phytoplankton quantity – but being able to tell more about which types are there will help us make better predictions about the rest of the food web.

Oscar Schofield and his student Filipa Carvalho collecting seawater.

In addition to the optical sensors, more traditional methods of measuring phytoplankton are employed. This involves collecting seawater and passing it through very small (45 µm) filters. These filters are then analyzed back on land for both the quantity of phytoplankton and which species are present.

Left: Unused filter, Right: After 500 mL of seawater were filtered. Although the phytoplankton are too small to see in the seawater, here we can clearly see many diatoms are present (identified by their greenish-brown color).

Besides light, nutrient availability and grazers (zooplankton) also control phytoplankton growth. If there aren’t enough nutrients (i.e., food) like iron or nitrogen in the water not very many phytoplankton can grow. In contrast if zooplankton out number phytoplankton then they will be eaten as quickly as they can grow, keeping the population small. To understand which of these factors is most important in controlling phytoplankton blooms (large population spurts), graduate student Filipa Carvalho is doing incubation experiments that vary light, iron and grazer concentrations in clear bottles.

Recent doctoral graduate Mansha Seth-Pasricha and grad student Filipa begin an incubation experiment.

On this trip we only have time to stop at ~30 stations to collect data, so the Schofield group also has “gliders” which fill in the big gaps between these locations. The gliders are autonomous underwater vehicles (AUVs) which look like yellow torpedoes. They swim through the water, diving between the surface and several hundred meters depth. The gliders collect data on the current, salinity, temperature, oxygen levels, and biomass throughout the West Antarctic peninsula’s underwater shelf and then report it back electronically. Many oceanographers see AUVs as the future of oceanography because they can go out and collect large quantities of data for you to process from the comfort of your office. How convenient!

Under Pressure

Since leaving Rothera Station we scientists have been busy in our laboratories. Our ship is zig-zagging on and off shore to the west of the Antarctica Peninsula, stopping at pre-determined locations to collect water and plankton samples. Some of these stations are located above the continental shelf – a stretch of underwater land that is about 300 meters (~ 950 feet) deep. This shelf has numerous features where it gets deeper (troughs and canyons) which influence how the water moves, where plankton live, and bigger picture things like where whales go to eat. When we continue to move off-shore the shelf drops off and the seafloor is ~ 3,000 meters (~ 2 miles). That’s ten times deeper!

Imagine diving down to the bottom of the deep end in a swimming pool. One of the most noticeable feelings is that your ears begin to hurt. This is due to the pressure of ~ 5 meters of water above you. The scientific equipment we send down to collect data about the water (temperature, salinity, oxygen content, etc.) has to be specially built to withstand extremely high pressures – way more than what you could withstand. One way to visualize the pressure is to send down a piece of Styrofoam. Those of us on the ship who feel artistically inclined (… and some of us who don’t) have been decorating cups to attach to our equipment and send down 3,000 meters. Below are two photos of my cups: before and after. As you can see, the pressure compacts the Styrofoam quite a bit

Before

After

Rothera

Yesterday morning we arrived at Rothera Station on Adelaide Island. Most of the scientists on the Gould got off of the ship so that ~30 British scientists from the island could go aboard and do a half day of science around the island. While they were busy at sea, the rest of us were split into groups and taken on various activities by our British hosts. Some people went skiing and snowboarding, others did a strenuous hike followed by crevassing, and the rest took a nature walk around Rothera Point to see the bay and its wildlife. The weather was phenomenal: very sunny, blue skies and in the 30s °F. After our activities, the ship returned and we ate dinner together followed by music from 3 different bands that the British have formed for the summer season.

 Jack Conroy on the nature walk

 

Watching a plane land on the airstrip; planes are used to do aerial surveys (e.g., for whales) and also transport researchers to more remote field camps
  

An Adelie penguin jumps out of the water to look at us

 

A Weddell seal swimming around in the bay

 

A pile of sleeping elephant seals; they like to sun themselves on the rocky shore for warmth
 

A 180° view from the point. Directly across the water you can see the Antarctic Peninsula!

 

Jess Fitzsimmons and Filipa Carvalho (both Rutgers U.) inside a crevasse. The crevasse (a deep crack in a glacier) appears blue due to the light shining through the ice and snow from above (photo courtesy of Jess Fitzsimmons)

TGIF

Happy Friday! Because ship time is very expensive, we don’t (normally) get weekends here. In fact, operations are 24 hours a day, 7 days a week. However, most of us will get a day off tomorrow when we arrive at Rothera Station on Adelaide Island. This research station is the headquarters of British Antarctic research, and they will graciously host us for a few meals, outdoor activities, and traditional soccer match. After our 24 hour stop it will be back to work!

Today has been very crisp and clear. As we get closer to the Antarctic continent and islands we’re passing more and more icebergs. The scenery is phenomenal!

A small part of Adelaide Island

The very bright sun and some icebergs

What lives under the sea?

Hint: Not mermaids
Disappointed? Read on, because I think the answer is way more ornate and beautiful than a Disney caricature

Day or night, the music is always blasting in the wet lab where Debbie Steinberg (Virginia Institute of Marine Science) and her group are investigating zooplankton and other small organisms. At each station they deploy two different tow nets to collect organisms from the ocean, some at 120 m deep and others at 300 m deep. They slowly haul these nets through the water – so slow that bigger things like fish can easily swim away and avoid being caught. After hauling the nets on deck they spend many hours sorting through the various organisms that were caught.

Undergrad Jack Conroy (back) and grad student Tricia Thibodeau (forward) sort and identify the organisms from a tow.

They look at the types and quantities of organisms that live in the water. For two specific types of organisms, krill and salps, they also measure the length of each organism. Length then gives them a sense for the age distribution of the population, much as height would for humans.

Krill (Euphausia superba) being counted by lab guru Joe Cope

Observations of zooplankton have been going on in this region every year for many years. That might sound repetitive, but each year is different. For example, this year has more salps than they have seen before. This is important because it indicates larger changes in the environment. Salps prefer to live in open waters which are a bit warmer (not full of ice). Increasing average global temperatures include rising ocean temperatures – making the environment more hospitable for salps.

This is a salp (Salpa thompsoni). The orange-red blob is its “stomach” which is full of diatoms, a type of phytoplankton (the microscopic plants of the sea).

Alternatively, krill prefer to live in higher nutrient waters closer to the coast. Juvenile krill depend on algae embedded on sea ice to survive. Grad students Josh Stone and Tricia Thibodeau explained to me that as sea ice melts due to warming temperatures, there is less food for young krill. As a result the krill population diminishes. This starts a domino effect within the food web, because whales, penguins and seals all depend on krill as a vital food source.

An assortment of organisms from the tow, including larval fish and spongiobranchaea – a predatory sea slug!

Some polychaetes of the genus Tomopteris in a jar. These remind me a lot of centipedes, and are known to be voracious predators of other small marine organisms. They were swimming around their jar very quickly, wiggling their many legs and their long bodies. It was almost like they were dancing to the music!

Mooring Recovery

Everyone on board has been busy collecting, processing and analyzing their samples – we’ve just completed the first ¼ of our research stations! In addition to collecting water and plankton we occasionally recover moorings for an oceanographer who is not on board. These moorings are long ropes, weighted at the bottom and with buoys on their top. At various points along the line there are data collectors which record information about the current, temperature, and pressure of the water. Having these spaced out throughout the water column vertically gives physical oceanographers the information to understand how various water masses are moving. Having multiple moorings spaced out at various locations around the Western peninsula gives a more complete (vertical and horizontal) picture of how water moves in this region.

These moorings aren’t able to send their data back to us from their deep location within the ocean, so once a year during this research trip they are collected. The ship has the coordinates of where the moorings were deployed 1 year prior; we return to the site and send an acoustic signal to the mooring which then releases itself from the weight anchoring it to the ocean floor. The buoy at the top of the line drags the whole thing to the surface. Then the competition begins on board to see who can spot the buoys first. Despite having detailed coordinates, the ocean is a huge place. With the waves heaving up and down it can be difficult to spot the buoy!

Once spotted the ship maneuvers close by and someone tosses a hook and line to snag the buoy. The buoy, line and sensors are then hauled on board. Here on the ship the information is downloaded for use.

Second mate Greg helps spot the buoy

Naomi Shelton (Lamont Doherty Earth Observatory) tosses the line and hook to catch the mooring

  Oscar Schofield (Rutgers U.) walks 1 of 15 sensors (still attached to the line) inside as others continue to haul in the line

Oscar Schofield and Filipa Carvalho (both Rutgers U.) haul in the acoustic sensor (yellow) and floats (orange) which were attached to the line and help make it buoyant

January 6, 2015

For the last 2 days we’ve been busy doing an assortment of science activities at our first two “stations”. These are locations of interest where we stop the ship (or circle around slowly) so that we can sample the water and survey what is living in it.
 

 

We are in relatively shallow waters, sitting above an underwater shelf and still well within sight of Antarctica. We see lots of snowy mountains and icebergs!

 
Josh Stone, a grad student at the Virginia Institute of Marine Science, notes the size and gender of Euphausia superba. These are a type of krill which primarily eat photosynthetic plankton (aka algae).

Palmer Station

This past Saturday (1/3/15) we arrived at Palmer Station on Anvers Island. This is one of 3 permanent US research stations on Antarctica – the other two are McMurdo Station and the South Pole. During the summer field season (now) Palmer is home to ~45 scientists and personnel. When our ship arrived it more than doubled the population on the island!

We stopped to resupply their food, drop off scientists, and pick up a few that had been living on station for a few weeks.

Palmer Station has 3 main buildings and a few smaller sheds for storage; the small orange things in the foreground are people coming out to greet our ship as it docked. (Photo courtesy of Jess Fitzsimmons)

During our 48 hour port call we finished setting up our lab spaces and many of us took the opportunity to hike / snowshoe the glacier directly behind the station. This glacier has been receding – most dramatically in the last 20 years.

The group I’m a part of even used the hike as an opportunity to collect a few glacial/snow melt samples to help us understand what’s flowing from the continent into the ocean.

Jess Fitzsimmons (Rutgers U.) takes a syringe sample of meltwater near the base of the glacier. She will analyze this sample back in New Jersey for iron (Fe), an element that is essential for algae to grow.

A strategically placed snowmobile for rescue operations near the top of the glacier, should an emergency arise.

Rob Sherrell and Jess Fitzsimmons (both Rutgers U.) and myself on top of the glacier.

The view from the top of the glacier. Flags mark the boundary of where it is safe to walk so we don’t fall into a crevasse.