By Ivan Muzychka
Every spring, when the sun shines on the waters around Newfoundland and Labrador, a pulse of life is created below the surface of the ocean. This pulse -- known as a "bloom" in biological circles -- is a collection of phytoplankton, tiny organisms which are the most important source of food in the marine ecosystem.
The bloom is invisible to the naked eye and is initially suspended in the water column, then begins to sink. Some of the phytoplankton is digested by sea life as it makes its way to the deeper reaches (the hyperbenthos and benthos) just above the ocean floor. How much of this bloom is eaten by fish and other organisms and how much remains unused is not clearly known.
Now researchers at Memorial University's Ocean Sciences Centre (OSC) and the Department of Earth Sciences will be trying to find out more about how this bloom moves through the ecosystem by following the bloom's various pathways through the food web. To do this, the interdisciplinary group of scientists will use the approximately $384,000 awarded to them by the Natural Sciences and Engineering Research Council (NSERC) Collaborative Research Grants program. The three-year award is especially significant since it was secured from a highly competitive grants program which has recently been cut by NSERC; the group had the only successful application from Memorial under this program.
Dr. Ray Thompson, a biologist with the OSC, is leading the project, which will be carried out in Conception Bay. "I'd like to think it was a combination of things," Dr. Thompson said of his group's success. "We are proposing to attack a problem which requires a variety of different expertise. No single researcher has all the skills required, and scientifically the project is also very meaningful."
He explained that the project will focus on an area of the ocean traditionally ignored the hyperbenthos, which is the name given to the community of flora and fauna living in the water within a few metres of the seabed. "It hasn't received much attention, and in addition, I think we were able to make a case for the novelty of the chemical techniques we will be using," he said. "Stable isotope chemistry is not particularly novel, but using specific markers to trace the flow of energy and essential nutrients through the ecosystem is."
Dr. Thompson will try to understand how the bloom interacts with benthic species. "How much do they depend on this pulse? Do they store the energy, and live off it over the year?"
From sunlight to lipids
"We are going to be looking at the spring bloom starting from where sunlight is used by the phytoplankton to make organic compounds such as lipids," said Dr. Chris Parrish, a marine chemist with the OSC. "We are interested in where this material goes. My specific area of expertise is to look at the lipid compounds. We use chromatographic techniques to identify the fatty acids which have been synthesized by the algae, some of which are essential to animal growth.
"The phytoplankton are largely invisible to the naked eye. If there are lots of them clumped together, they look like snowflakes," said Dr. Don Deibel, a biologist at the OSC. "They are utilized by many types of water column organisms, including zooplankton. The most abundant group of zooplankton is small crustaceans which are called copepods. Our previous research had to do with determining how much phytoplankton was created during the initial bloom, and how much was eaten by the zooplankton. If the zooplankton don't consume all the phytoplankton, some of the remainder may be degraded by water column bacteria which is also important to the food chain. But at -1 C, very little of the bloom gets used by bacteria or zooplankton, and a significant portion sinks to the bottom of Conception Bay."
Dr. Deibel intends to collect, identify and study various aspects of the feeding of animals known as hyperbenthic phytoplankton. "These zooplankton spend all or part of a given day within five metres of the bottom," he explained. "This is a poorly known community of consumers, because it is too deep to collect animals by scuba diving and very difficult to collect samples from just above the bottom using nets at such great water depths."
Food for thought
While the study does not have an applied component per se, Dr. Deibel hints that the work will have important implications. "There is much known about what a cods eats," he said. "What's more poorly known is where the food a cod does eat comes from. What is the food web which produces the food a cod prefers? Our project is aimed directly at attempting to answer this type of question."
At the centre of the project is a research technique which uses isotopes -- different forms of an element -- to trace how the bloom is degraded. It's a technique Dr. Jun Abrajano knows well; the earth scientist has used it in a variety of other research projects aimed at understanding environmental processes.
"We are coming in with an very important set of approaches," he explained. "It would be very hard to find elsewhere in Canada a combination of expertise such as this to understand where this biomass has gone after it sinks to the bottom."
Dr. Abrajano has experience in identifying the sources of individual compounds in sediment and in benthic organisms.
"I will be looking at the ratio of two stable carbon isotopes as a means of indexing the sources of individual compounds," he explained. "Using this technique we have been able to say that not all the fatty acids have gone through the food web in the same way. We can combine this data with a knowledge of biology and we get a very potent combination to unravel the pathways taken by these chemical markers."
"That's the beauty of biomarker research," Dr. Parrish noted. "Isotopic analysis lets us know how long the bloom has been degrading and how many times a molecule has been consumed in the food web."
The study will be completed in 1998. In addition to the four researchers,
it will involve several graduate students, postdoctoral fellows and research
assistants, who will be trained in the use of the techniques the project