Satellite Oceanography and the "Malaspina Dragon"
At first blush it wouldn't seem as if training in astronomy is a natural fit for someone who ended up in oceanography, but it worked for Dr. Jim Gower. He is a researcher at the Institute of Ocean Sciences (IOS) located in Sidney, British Columbia on Vancouver Island. IOS is a centre for research on coastal waters of BC, the Northeastern Pacific, the western Canadian Arctic and navigable fresh waters - east to the Alberta border. As one of Canada's largest marine institutes, it represents part of DFO's ecosystem management approach to protecting the marine environment.
Dr. Gower explains: "I'm a physical oceanographer, originally trained as an astronomer. I was hired in 1971 when many satellites were going up, and there was a need for people who knew how to work with remote measurements. At that time, a number of scientists made the transition from astronomy to oceanography. I was hired as the original satellite oceanographer in DFO. Since then, lots of others have joined us because satellite oceanography is becoming mainstream. We have a remote-sensing group here at the Institute which has been running on a small scale ever since those early days."
Researchers are able to make use of satellite images made available online by the Earth Observation System of NASA, and similar systems of the European Space Agency and Space Agencies of other counties. One use of the technology is to track seasonal phytoplankton growth and the formation of algae blooms.
To understand why this tracking is such vital work, it is important to understand the role phytoplankton plays in our marine ecology. Phytoplankton are minute single-celled plants, and are the first step in the food chain on which ultimately all marine life depends. Although too small to be seen individually, when they are present in high enough numbers, they change the colour of the water from clear blue to a cloudier green. This colour change is due to the light they scatter and the presence of photosynthetic pigments such as chlorophyll within their cells. At high enough concentrations they form algae blooms which may colour the water white, green, brown or red.
High concentrations of phytoplankton, often caused by the ready availability of sunlight and nutrients are good for the ecosystem most of the time. They drive productivity for the large number of marine animals up the food chain. But they can also be harmful to local marine ecologies. The formation of blooms is cyclical and, all things being equal, spring blooms are just the normal spring resurgence of growth after the winter.
Dr. Gower notes, "The sort of data we look at is a standard chlorophyll product which is meant to measure chlorophyll in open ocean waters. It works pretty well, but it doesn't work nearly as well in coastal waters. This is something that everyone runs into when they come up against the coast. Difficulties arise with satellite imagery because of the complex nature of coastal water, often complicated by atmospheric pollution."
He adds, "One of the early bits of research I got involved in was a new method of measuring chlorophyll using fluorescence. We can measure this fluorescence using the images that the satellites produce, providing we have special bands Footnote 1 that look at the actual wavelength where the fluorescence occurs, and at nearby reference wavelengths where it does not. The fluorescence idea with satellite images is quite interesting because it is what everybody uses on a ship or in the water. If you want to know if chlorophyll is there, you simply shine a blue light at the water and look and see if any red light comes back to you. That is the chlorophyll fluorescing."
In recent years Dr. Gower and his colleagues used fluorescence measured by satellite images to look at the Strait of Georgia and adjacent inlets. They have identified a new factor which could be influencing the timing of the spring bloom in the Strait through early triggering by plankton growth in coastal inlets. They are calling this mechanism the "Malaspina Dragon" after the characteristic pattern of high-chlorophyll water flowing though Malaspina Strait in late February of some years. The Dragon pattern was seen in 2005, 2008, and 2009, and probably occurred in 2004 and 2007. It did not occur in 2003, 2006, 2010, 2011 and 2012.
The spring bloom in the Strait of Georgia occurs on average 3-4 weeks earlier in years when the "dragon" is active. That suggests that seeding from inlets may be a significant factor controlling timing. And timing of the bloom is important for survival of salmon and other fish species, and has potential application in developing ecosystem-based science.
The name "Malaspina Dragon" was inspired by satellite images of the bloom entering the Strait. The scientists remarked on it, and Sara Statham, a university co-op student working with Gower, illustrated the connection by drawing mythical dragons beside the images in poses that resemble the blooms.
Dr. Gower: "We attribute the blooms that happen in Jervis and Sechelt Inlets to continuing growth as it flows out into Malaspina Strait and to the patterns of fresh and salt water that exists in the Strait of Georgia. Basically, the shape comes as the bloom squeezes its way through large areas of freshwater near the surface. When it comes to fresh water, the water also tends to go under it because the bloom is a little bit denser.
One of the things we've been doing since 2009 is driving to Egmont, a little village near Skookumchuck Narrows, and installing a recording fluorometer on the dock there for February to April of each year. This will record any bloom that comes out of Sechelt Inlet when Skookumchuck is ebbing, or,out of Jervis Inlet when Skookumchuck is flooding. Ironically, we haven't seen a single early bloom since we started, but we see blooms that match the normal, later spring bloom in the Strait."
Dr. Gower notes it is important to be monitoring the Strait of Georgia to know - not just an average date when the spring bloom happens - but also what sort of mechanisms may be triggering it. The fact that the Malaspina Dragon coincides with earlier spring blooms in the Strait is interesting information. Whether it is causal is still to be determined. The appearance and timing of the Dragon is providing new information, whose importance will become clearer with further monitoring of the Strait and of Jervis and Sechelt Inlets. The combination of satellite imagery with surface moored fluorometer readings seems to be the best bet to fill in the blanks.
"On balance," Dr. Gower says, "The appearance of the Malaspina Dragon seems to be another link in understanding how the coastal ecosystem works. Whether it is a critical and "smoking gun" link is pretty hard to say at this point. The bottom line is that we have discovered something significant, new, and important to keep on top of."
The benefits of improving our understanding of factors affecting primary productivityFootnote 2 in BC coastal waters cannot be over emphasized. Understanding phytoplankton growth and algae blooms is an essential element of that understanding. The fate of our fisheries and the marine ecosystem lie in the balance.
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