In the winter, the SEM lab at UQAR- ISMER is a quiet contrast to the rugged Arctic expedition Prof. André Rochon goes on each summer aboard the icebreaker CCGS Amundsen. He enjoys the opportunity to devote more time to meticulously imaging the samples he and his colleagues have collected from the Arctic earlier in the year.
André has taken thousands of images of marine biological and geological specimens, many useful in identifying organic microfossils and plankton. In December 2014, JEOL selected one of his micrographs showing a daisy chain of six cells of the dinoflagellate Neoceratium ranipes to win the Grand Prize in its first image contest.
As a result of his extensive collection of images, André is currently preparing a book on plankton identification for the Canadian Arctic that will be useful for scientists studying the marine life there. "I mostly use the SEM for illustrating the morphological criteria for identification. Some species differ from each other by minor details not easily seen on regular microscopes," he explains.
The objective of his work with the dinoflagellates (unicellular algae) is to study climate change, often referred to as paleoclimate, over geological time (approximately the last 10,000 years), pollution, invasive species, and ballast water transport.
The icebreaker Amundsen is a research platform for multiple disciplines and is employed in the ArcticNet program, which brings together researchers from centers of excellence in Canada and abroad to study all aspects of the impact of climate and modernization on the Arctic. Canada is at the forefront of climate change research, with good reason because the country has the longest Arctic shoreline.
The collected microscopic marine life can tell a great deal about what transformations are occurring there.
"There are over 2000 species of dinoflagellates today in the Arctic and we are discovering new species ever year that we didn't know were there. There are approximately 200 species that we have documented from the Arctic," André says.
The dinoflagellates, which range in length from 30 to 100 microns, can be collected at either the surface of the water or as cysts when they sink and can be found in the sediment. Cysts are formed, Andre explains, when "an organic membrane develops inside the cell. Cysts contain all the nutrients necessary for the cell to survive through the winter. They can remain viable for several years - some that have been dormant for as long as 110-120 years and can be revived. They can survive any catastrophic environmental event."
The collection process requires using various coring devices to penetrate and recover a 9 meter long tube of a core sample material from the sediment, or a box core of 50cm2 for larger samples. Researchers use a plankton net of 20 micron mesh to collect the algae in the upper part of the water column.
André's focus is "documenting the changes in species assemblages over time, which is indicative of environmental changes, or documenting the distribution of actual plankton and changes in the geographical range of modern species (also indicative of climate change). I also document the presence of these algae in ballast water and sediment, which allow me to quantify the risk of invasion of nonnative species in a given port or region."
Through ballast water pumped out by ships, organisms from distant places can be introduced into a harbor or port. "We have a team studying dinoflagellates pumped in as ballast water and transported, then when they are de-ballasted. We learn which species are transported and how well they survive the transport, which can be several days or weeks, and how well, once released, is their capacity to survive. Dinoflagellates are the main organism responsible for red tides, or toxic tides. If a toxic species arrives in a ballast tank and is dumped into the sea water, they may survive and thrive and develop new toxic outbreaks and they are difficult to get rid of in new environment."
André's microscopy techniques were perfected over the years, initiated during his post-doctoral work in London with Dr. Jane Lewis. He explains the process of creating his remarkable images: "To obtain maximum resolution and quality for dinoflagellate or dinocyst specimens, individual specimens are picked individually, washed several times in distilled water, dehydrated in an acetone series, air or critical point dried (depending on the species), then sputter coated with gold-palladium. In the SEM, I am using low KV (2.8 - 3.0) and a spot size that provides the best signal to noise ratio combined with high resolution. The background on the photographs is removed using Photoshop, first by outlining the specimen, then by isolating it and removing the rest of the image and replacing it with black. I sometimes color the specimens the same way, this time using a color, or color gradient overlay over the specimens."
Low kV is crucial to obtaining quality images of biological specimens. Higher kV can cause the specimen to "burn or cook - at higher kV you can still get good images but the sample will not withstand it," he says.
A key advantage to lower kV, according to JEOL applications scientists, is that it provides much better surface information due to lack of penetration of the electron beam into the sample which would make the samples appear translucent.
In addition to his research at ISMER-QTAR, André teaches at the MSc and PhD level and trains students to identify dinoflagellates using both regular compound optical microscopes and SEM.
Before winning the Grand Prize for the JEOL Image Contest in 2014, he also won 4th place in a Canadian scientific image contest with this image in 2010.