Posts Tagged ‘autotrophs’

Skidaway Institute researchers published in international journal

June 14, 2012

Skidaway Institute of Oceanography scientists Jens Nejstgaard and Stella Berger are part of a 21-member, international team of researchers whose paper was recently published in the Journal of Experimental Marine Biology and Ecology.

The object of the research was to observe the effects of different light levels on the behavior of microscopic marine organisms. The team focused their efforts at a group of organisms called mixotrophs. Those are single-cell plankton that exhibit the characteristics of both animals (heterotrophs) and plants (autotrophs). They feed on other organisms, but they also can grow through photosynthesis, just like algae and other plants.

“Most higher organisms are either plants or animals, and we have therefore traditionally sorted most organisms in to these two groups, or fields of science: botany or zoology,” said Nejstgaard. “However, as our understanding of the smallest sized life on earth, single celled organisms is rapidly growing it appears that a large part of the life on Earth may be mixotrophs. This opens new focus of seeing, and investigating our ecosystems.”

The international team with Stella Berger (back row, center, with sunglasses) and Jens Nejstgaard (far right) conducting experiment with specially designed mesocosms, using neural (grey) optical films to simulate light levels on different depth’s down to 50 m in the Eastern Mediterranean.

Nejstgaard, Berger and their colleagues, collected natural water containing plankton and other organisms from the Eastern Mediterranean Sea near Crete and transported it to a into specially-designed tanks on land, called mesocosms, at the Hellenic Centre for Marine Research.  In the 30-cubic-feet mesocosms they adjusted light levels to simulate differences in ocean depths down to approximately 150 feet.

The researchers found the mixotrophs do react to different levels of light. In general, the organisms tended towards plant behavior in brighter light and animal behavior at lower light levels. However, they also found that response is very complex, and the entire team of  scientists that worked on the mesocosms are presently analyzing a large amount of data to clarify many of the ecosystem interactions in this complex system.

Advertisements

Barrow — Jan 16

January 19, 2012

16 Jan 2012

Ice conditions are still unstable.  Our UMIAQ support team spent the morning doing reconnaissance of our intended sampling sites. After yesterday’s efforts they suggested that since it might be dangerous, it wasn’t a good idea for anyone on the science team to accompany them. Because the ice is still forming and the ocean is a powerful force, the ice can break-up pretty quickly. The team first scouted out our near shore site, but it was inaccessible due to a major crack between it and our ice trail. We use a trail cut through the ice to guide us on a safe snow machine run over it. They continued on to our second site located further out into the ocean and to the north. The ice in that area seems to be more stable. They liked what they saw and decided that it would be safe for us to set up camp there.

Brower Frantz, UMIAQ logistics leader proudly stands by the ice camp.

After making this decision the team came back, loaded up the camp gear (tents, generators, heaters, ice augers, etc) and went back out. This time Steven Baer from the Bronk group went with them to help orient the tents and make some basic measurements. Before starting we need to know the ice thickness, water depth, and usually how far light penetrates. In this case there basically isn’t any light but hey, we’re scientists. Measuring zero’s (or close to zero) can be just as important. Its data!

Meanwhile, back on the NARL campus where our labs are, there was a flurry of activity as we all checked and prepped our gear. Finally, around 3pm the camp was set-up and we were ready to go. I was pretty worried about how late it was getting, but because we have such a short time up here and the ice was deemed safe now we needed to push a little bit. Who knows if we’ll even get another chance given the dynamic condition of the ice.

The ride out was relatively uneventful. The ice was remarkably smooth compared to our previous trips.  As was explained to me, when the ice first forms it is relatively flat and it only gets jumbled up later as storms, wind, currents, and tides push it around. Flat ice generally means that it is new ice.  That is what was worrying everybody. We know the ice is still forming and moving a lot. Hopefully it won’t move while we’re on it! After about 30 min of driving we made it to our camp. Having well established sampling routines by now, this is our 6th expedition, we all got to work unloading our gear and starting to sample. The Yager group occupies their own tent (the smaller one) while the Frischer and Bronk group occupy the larger one.

Ice Camp 16 January 2012

In the Frischer tent I got started right away making measurements of the water column. We are using a new instrument that lets us measure depth, temperature, salinity, oxygen, chlorophyll, pH, and turbidity. It’s a pretty nice instrument but a bit delicate and the computer software is not straightforward. We transported it as if it was a delicate infant wrapped in blankets with warm water bottles and hand warmers to make sure it didn’t freeze on the way out. I think we overdid it! When I unwrapped it in the tent it was positively hot. The instrument worked well and we got a good look at the water conditions. As expected the water temperatures was -1.8 deg C, salinity was around 33 PSU (normal for the Arctic coastal ocean), there was almost no chlorophyll in the water (no light no algae in the water). Most importantly the water column was well mixed which means that we could sample at one depth and be reasonably assured that it would be representative of the whole water column. We decided to sample at 2 meters below the bottom of the ice.

Graph of water data from the MANTA, Eureka Environmental

After I was finished measuring the water the Bronk group got rolling. They rinse and fill what seem like a million small bottles to which they add a very small amount of nutrients enriched in their stable isotope concentrations. Stable isotopes are non-radioactive form of elements (atoms) that are slightly heavier than the normal form. For example, the normal atomic weight of Carbon is 12 (meaning it has 12 protons) while the stable isotopic form has a weight of 13. We refer to it as 13C.  Because 13C  is slightly heavier than 12C, it can be measured on a mass spectrometer. By measuring how much of it goes into cells during an incubation, the rate of uptake can be calculated. The Bronk group is making some of the first ever measurements of nutrient uptake rates by microbes in this region of the Arctic coastal ocean.

The process went pretty smoothly but since it was so cold, even in the tent, the pipettes which they were using to inject the stable isotope into the samples were freezing and slowing the process.

Dr. Debbie Bronk injects stable isotope labeled nutrients into seawater.

Meanwhile in the other tent the Yager group were having even more problems with freezing. They are collecting water samples to make measurements of the carbon chemistry and general activity of the microbes, so it is especially important that their samples do not freeze and are not exposed to the atmosphere which can contaminate the dissolved gas content of the seawater. Unfortunately, their samples were freezing.  However, after getting them off the ice floor of the tent and placing them into a seawater bath (a cooler filled with seawater) they seem to have solved the problem and were able to collect most of the samples they needed.

Dr Tish Yager and Colin Willams collecting water.

When the Bronk group was finished it was our turn.  Our sampling is probably the most straightforward, but we need to collect a lot of water.  We’re collecting enough water so that we can extract DNA and RNA from the bacteria in it.  We collect about 140 liters (about 40 gal or 310 lbs). Using a specially designed submersible pump we collected water in seven 20 liter carboys wrapped in neoprene and then place them in a cooler of snow. Believe it or not, the snow actually keeps the water from freezing. But, as simple as it sounds, we had our problems too. The generator that was running our pump ran out of gas.  Actually, the generator had a gas leak so it’s lucky it just ran out of gas and didn’t explode. But, because of excellent planning on the part of the UMIAQ team we had two generators on site. However, that meant the Yager group was without lights in their tent. We solved that problem by moving two snow machines so they pointed at the tent and the headlights provided enough light.

Finally we were all done and got all our gear and samples loaded back onto the sleds.  It was unbelievably cold and windy and we were all tired and ready to get back. The trip started off smoothly until I managed to get my sled stuck. It’s really tricky pulling a very heavily loaded sled. I had to slow down over a series of small ridges because the person in front of me slowed, and that was all it took for the snow machine to sink a little too much into some soft snow and lose traction. With all of us helping we disconnected the sled and managed to lift the back end of the snow machine out of snow, enough to get it moving. Then we were able to push the sled back to some more level ice and reconnect it to the snow machine. It was exhausting! But the fun wasn’t quite over. As we started moving again Debbie, in an effort to make it over the hole I had dug with the snow machine, went a little too fast over the area and bumped into Rachel and Jenna who were on the snow machine in front of them. No real harm though. Jenna fell off the snow machine but it was into soft snow and she wasn’t hurt. The brand new snow machine Deb was driving suffered a cosmetic crack in its fairing. Without further incident we all made it back safely to campus and quickly rushed our samples to our respective labs for processing.

Victoria and I spent the next 5 hours in our cold room filtering all that water we had collected. We had hoped to start another humic addition bioassay that is a component of Zac Tait’s thesis research, but it was just too late so we decided we’d do that first thing in the morning. After all the filtering was done, our samples put away safely, and all our gear cleaned-up it was time for some well deserved rest. I felt weary and frozen to the bone but pleased with the progress we had made.

Even though the sun won’t shine, tomorrow is a new day.

Skidaway Institute scientists study Arctic climate change

December 1, 2009

Climate change will have profound effects on the Arctic ecosystem, and those effects may be felt around the world. Skidaway Institute of Oceanography professor Marc Frischer is launching a three-year project to examine the effects of rising temperatures in the Arctic and how those changes will impact the marine food web.

The project is funded by a $356,139 grant from the National Science Foundation (NSF).

“We know global climate change is impacting the fragile Arctic environment,” said Frischer. “Atmospheric concentrations of heat absorbing greenhouse gases including carbon dioxide are rising; the Arctic sea ice and permafrost are melting; and models are predicting significant changes in precipitation patterns in the Arctic.

“What we don’t know is how living systems will respond or adapt to those changes and how, ultimately we as humans will have to adapt to those changes.”

The work will be conducted in Point Barrow, the northernmost location in the US, at a NSF supported research station operated by the Barrow Arctic Science Consortium.

Pt. Barrow, Alaska, in winter

The landscape at Point Barrow is tundra that sits on top of as much as 1,300 feet of permanently frozen soil called “permafrost.” The concern is that with climate warming this permafrost will begin to melt and release an enormous amount of organic material into the coastal ocean.

“What you have now is have is up to 1,300 ft deep frozen soils consisting of ancient forest peat locked in the permafrost,” said Frischer. “What will happen when the permafrost starts to melt and that material, called humic acid, is released into groundwater, streams, rivers and ultimately into the ocean? That is what we want to know.”

Frischer’s focus will be on the microscopic organisms that comprise the very bottom of the Arctic Ocean food web. They include a wide variety of tiny organisms. On one end are the autotrophs, organisms that consume inorganic material and produce energy through photosynthesis, like plants. At the other end are the heterotrophs that consume organic material and obtain their energy from what they eat, like animals.

The humic acid material is rich in carbon, but lacks nitrogen, a key element that both autotrophs and heterotrophs need to make use of the carbon in the humic material. For every carbon molecule an organism uses, it will also need nitrogen.

“If you are going to grow more things, then that nitrogen has to come from somewhere,” said Frischer. “Our hypothesis is that as this humic material enters the coastal Arctic, there will be a greater demand for nitrogen at the base of the food web.”

Whoever gets that nitrogen, whether it will be the plant-like autotrophs or the animal-like heterotrophs, will determine how much organic production ends up farther up the food web in larger marine animals and eventually humans.

“This will all be set by whoever wins the war for nitrogen,” said Frischer.

Over the course of the project, Frischer and his team will travel to the Arctic several times a year. While in the Arctic, Frischer’s team will focus on making observations of the system and conducing experiments to determine what organisms are growing, which organisms are using the humic material, and determining where they are getting their nitrogen from and how they are doing it.

“We will manipulate the nutrients in the water samples and see how the different micro-organisms react,” said Frischer. “From that we should be able to project how the natural environment will react and ultimately contribute new data that help us understand and predict the biological effects of climate warming in the Arctic.”

Frischer will be working with two collaborators on the project, Patricia Yager from the University of Georgia, and Deborah Bronk from the Virginia Institute of Marine Science. Both Yager and Bronk received independent grants from NSF to participate in the study.