Water science: remote sensing for algal blooms
Colourful Research - Remote Sensing for Algal Blooms
Space RelationsWhen Dr. Caren Binding of Environment Canada’s Watershed Hydrology and Ecology Research Division found out the news, she was very excited. Her application had been accepted and her research on algal blooms in major inland lakes would get a big boost.
The remote sensing scientist learned about the possibility of using the new technology for her research during a workshop in Madison, Wisconsin in June 2012, and submitted a proposal. “The level of detail we now receive from images of Lake Winnipeg and the Great Lakes is vastly improved,” says Dr. Binding.
Using Aquatic Optics
When light enters water, it interacts with materials in water. The light is absorbed or scattered in various degrees to determine the colour of that water. To put a complex process in simple terms, Dr. Binding and her fellow scientists use special in-water and laboratory instruments that characterise the interaction between dissolved and suspended materials and light across the visible spectrum. “Using measurements of aquatic colour in optical models that we have developed, we can determine the concentrations of those materials. In turn, those concentrations allow us to detect algal blooms.”
Remote sensing of water quality is based on the principle of aquatic optics. When Dr. Binding started at EC, she worked with and was mentored by an early pioneer in the field of inland water optics, Dr. Robert Bukata. He discovered that the signals from all the dissolved and particulate material in the water (things like phytoplankton of various sizes and colours, or suspended sediments) made for a complex interaction of optical processes. “Our more recent work has built on that understanding and developed methods to apply satellite remote sensing to observe lake processes on scales not possible using ground based observations,” says Dr. Binding.
Earth observation satellites carrying sensors orbit the earth at altitudes of 700-800km. The sensors measure the colour of the light leaving the world’s oceans and lakes. “After removing the effects of the atmosphere and applying appropriate optical models, we can interpret the coloured water quality parameters present in a water body and study specific events such as algal blooms or shoreline erosion.”
The Impact of ISS Technology on EC’s Research
Dr. Binding began using images from a sensor aboard the ISS in September 2012. The sensor, called HICO (Hyperspectral Imager for the Coastal Ocean), was developed by the US Naval Research Laboratory and is now supported by NASA’s ISS Program, becoming the first spaceborne hyperspectral imager designed to observe coastal and inland waters. HICO represents a huge advancement in technology.
Previously, scientists relied on the relatively small number of spectral bands available on earth observation satellites to develop methods of determining colour. “HICO imagery provides spectral information in approximately 100 bands, compared with typically less than 10, and is allowing us to investigate an enhanced suite of water quality parameters.” While previous methods have allowed scientists to detect and monitor algal blooms in terms of overall biomass, extent, and timing, the additional spectral information offered by HICO allows them to investigate the potential to determine the composition of algal blooms. “For example, we can look for specific pigments to distinguish potentially harmful cyanobacteria from more harmless varieties.”
Contribution of the Remote Sensing Research
Currently, Dr. Binding is using the HICO technology to focus on two lakes: Lake Erie and Lake Winnipeg.
Lake Erie is the most severely impaired of the Great Lakes, with the western basin in particular being prone to intense algal blooms. EC’s Great Lakes Nutrient Initiative is working towards improving the conditions and reducing the frequency and extent of these blooms. Lake Winnipeg is also noted for its deteriorated water quality characterized by recurring, intense algal blooms. Water quality issues are being tackled through the efforts of EC’s Lake Winnipeg Basin Initiative.
The remote sensing technology offers information that complements EC’s algal bloom monitoring and research activities under these two programs. “We have been able to use the technology to better understand the long-term changes that occur to water clarity and algal blooms in the lakes, in response to invasive species, implemented nutrient management practices, and climate change.”
“We are developing methods to discriminate via satellite between the different types of blooms and where they are concentrated. These methods will offer significant advances in our ability to manage risks to our environment and health brought about by potentially harmful algal blooms.”
Dr. Binding says she is continuously amazed by how much information can be obtained from space observations to describe environmental processes. She is happy to participate in the ISS Program, using its cutting edge technology while remaining grounded. “To be just a small part of that advancement of knowledge is very satisfying.”
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