For decades, scientists have been puzzled as to how and why some microscopic marine phytoplankton produce specialized neurotoxins that poison animals and humans. UNCW associate professor of biology and marine biology Alison Taylor has set out to answer these questions by investigating the effects of the Florida dinoflagellate Karenia brevis and other algae responsible for harmful algal blooms (HABs).
Grazed upon by other neighboring planktonic species in nutrient-rich coastal waters, dinoflagellates are a type of algae. Smaller than the diameter of a human hair, these water-dwelling unicellular organisms exhibit an array of morphological and physiological traits. Some may emit light through bioluminescence, the same process by which fireflies glow, and most are photosynthetic using the sun’s energy to produce food, thereby playing a critical role in marine ecosystems.
Yet under the right conditions, a few species can cause HABs that result in devastating ecological and economic damage in coastal regions because of the neurotoxins they produce. Such HABs are known colloquially as red tides, because the pigments of these organisms discolor the water a pinkish-reddish hue.
While HABs have been known to occur naturally since the 18th century, according to the National Oceanic and Atmospheric Administration (NOAA), outbreaks are increasing in both frequency and severity. It is estimated that along the coastlines and in the surface waters of the United States, a single HAB event can cost as much as $60 million in lost fisheries and recreational economic activity in affected communities. To respond to an increasing environmental threat and human health risk from HABs, the U.S. Congress passed a law in 1998 requiring NOAA to lead an inter-agency task force on HABs and provide continually funded research into the origins and types of organisms that cause them.
“It is estimated that along the coastlines and in the surface waters of the United States, a single HAB event can cost as much as $60 million in lost fisheries and recreational economic activity in affected communities.
Because dinoflagellates are microscopic marine plants, it is curious that they make neurotoxins which can adversely affect humans and other mammals that do not share their environment or evolutionary history. Interestingly, Taylor’s team discovered several non-toxic phytoplankton that exhibit properties similar to animal nerve cells, including membrane ion channels which enable them to generate nerve-like impulses. Because Karenia brevis competeswith nontoxic phytoplankton for resources,it is possible it may have evolved channel-specific poisons to target planktonic prey or competitors as a mechanism of self-defense.
“As soon as we saw these nerve-like impulses in non-toxic marine phytoplankton,my first thought was this could be an ecologically relevant target for algal neurotoxins,” Taylor says.
With the microscopy lab’s current laser-based confocal microscope, Sheila Kitchen, a marine biology graduate student working with Taylor, has determined the distribution of toxins and fluorescent markers within non-toxic phytoplankton cells. Using this technology, Kitchen can scan a thin section and, by focusing through the cell in steps, reconstruct a three-dimensional image of the cell and spatial location of the markers. “Her research in the last two years has really moved this work along,” Taylor says. “Sheila’s thesis research verified the localization of certain toxins within the cell and, using electrophysiology, demonstrated an effect on the fast signaling events of the membrane.”
Taylor developed a National Science Foundation grant proposal to support further research into the interaction of toxins with ion channels in other species of plankton. The proposal, funded this year, supported the purchase of new microscope imaging equipment essential for the study of the cell signaling patterns associated with the phytoplankton nerve-like impulses.
The new advanced microscope with EMCCD (electron multiplying charge coupled device)-based live cell imaging — a fast and ultra-sensitive digital camera technology — will enable real-time capture of the cellular events that underlie rapid cell signaling in both Karenia and non-toxic species. This increased capability will permit an unprecedented view of the subcellular activities that underlie behavior and the ability of these cells to sense their environment.
“What we are doing,” Taylor explains, “is using light to interrogate live cells.”
Taylor, who is originally from the UK, joins UNCW’s collaborative team of HAB researchers in the departments of biology and marine biology, chemistry and biochemistry and at the Center of Marine Science who have been studying Karenia brevis and its name-bearing toxin, brevetoxin, for more than 12 years. Center for Marine Science director Daniel Baden and CMS researchers have collected extensive background and exposure data to indicate that brevetoxins elicit neurotoxic, immunologic and pulmonary effects in models of humans and animals exposed to brevetoxin by inhalation. Effects can be potentially fatal when humans consume contaminated shellfish, resulting in neurotoxic shellfish poisoning,a serious condition of the central nervous system that also hinders ability to breathe.
“Collaboration with HAB researchers here on campus and at the Center for Marine Science, together with our long-standing international link with scientists in the UK, provides an excellent platform with which to develop this exciting new interdisciplinary research program,” Taylor says. “New imaging equipment provided by NSF will complement imaging equipment already available to faculty, graduate and undergraduate students and significantly extend our high-resolution live-cell imaging capabilities at UNCW.”