On the morning of August 17, as probes measured a thick mat of blue-green algae, scientists aboard a university research vessel on Missisquoi Bay checked their watches at exactly 11:30 a.m. and looked heavenward a nod to an unseen presence.
The unseen presence was a U.S. satellite that passed over the lake at precisely that moment and snapped an image of northern Lake Champlain. Meanwhile, the probes took samples every 10 seconds across long swaths of the lake to measure levels of chlorophyll, a potential marker of the presence of algae, if not its toxicity. The group's goal is to explore better ways to locate and track areas of dangerous blue-green algae in order to understand the causes and movement of the blooms. The next day's newspaper put their efforts into context: Algae blooms explode, shouted a headline, the story below reminding that the blooms can contain toxins powerful enough to kill dogs and sicken humans.
Suzanne Levine and Leslie Morrissey, both associate professors of natural resources, along with graduate student Sarah Wheeler, correlate on-water test results with information from satellite images to develop models with enough predictive power to reliably monitor algal blooms over large areas. After the sampling trip on the research vessel, they return to the computer lab, where Morrissey and Wheeler use the chlorophyll numbers to create an algorithm that is applied to the satellite images to produce maps of chlorophyll density and distribution. The satellite image provides details of the algal blooms never before seen. Just to see those plumes was fabulous, says Morrissey. What Morrissey wants to know now is whether satellite imagery can capture the nature of the bloom, and the distribution of blooms over time.
The trio, whose work is funded by the Vermont Water Resources and Lake Studies Center, is attempting to take advantage of various Earth-observing satellites to acquire highly detailed images over the summer. New satellites like DigitalGlobes QuickBird and the European Space Agencys MERIS satellite images can record information that is better suited to monitor water quality than their predecessors. Remote sensing offers potential solutions to current challenges of algal-bloom monitoring, Morrissey says. If the new techniques prove successful, the combined efforts of the satellite and on-the-ground teams should further understanding of algal blooms and ensure that emerging blooms are detected and their toxicity assessed before tragedies occur.
In a parallel study, other researchers sample and test lake water weekly to determine if any algae present is merely a late-summer annoyance or a blue-green menace laden with cyanobacteria, which can produce toxins that attack the liver or brain. Mary Watzin, an associate professor and director of the Rubenstein Ecosystem Science Laboratory, oversees these tests, with help from her staff, graduate students, the Lake Champlain Committee and volunteers.
Toxic invader
Blue-green algae is nothing new. (Its) been around for more than three billion years, Levine says. But the problem of toxic blue-green algae became more common since the 1950s, perhaps tied to inadequate sewage treatment, increased fertilizer use and/or overall population increase.
Blue-greens are in all lakes and ponds and can even occur in slow-moving rivers. There have been toxic outbreaks all over the globe, including Europe, Japan, New Zealand, Australia, Brazil, and other places, adds Watzin. We don't know if all species that produce toxins can do it anywhere, because we know so little about what triggers toxin production.
It is concern for public health and curiosity about these unknowns that fuel the combined efforts of the UVM scientists.
Watzin, whose work is funded by grants from the National Oceanic and Atmospheric Administration and the Lake Champlain Basin Program, says she wants to figure out why were having the blooms. I think they're different than we ever had before, and I think they are more intense. She counts off and disputes one theory for every finger on her hand, then postulates her own. Im an ecologist, so my focus is what in the ecosystem may be driving this changes in the food web that may cause the increase.
Watzins former graduate student-turned-employee Emily Brines is pursuing the ecological angles. Graduate student Meghan Kreider working on the potential connection between zebra mussels and microcystan, the liver toxin. Graduate student Todd Clason will begin a study this fall to determine whether the algae is wintering over in the mud of Mississquoi Bay instead of dying off each year. And new grad student Sam Couture, who will work on the algae project, has a special interest his family dog was the first killed by the algal toxin on Lake Champlain.
The focus of our respective studies is different, says Morrissey, theyre looking at toxicity, were monitoring algal biomass from space. Working together we share samples, and when our turnaround (from image to information) is faster, well be able to see the bigger picture. The team anticipates the day when the satellite maps can reveal the location of blooms to improve the efficiency of UVM and state water-sampling efforts which resources currently limit to a handful of locations across the lake. This could save time and money as well as contribute to public health efforts, she says.
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