Dr. Mike Lakeman. Photo courtesy of Mike.

Mike Lakeman’s interest in biology was shaped by his childhood environment. He grew up on an orchard in New Zealand catching frogs and turning over tree stumps to look at bugs. But his interest in biology as a science began as an undergraduate at the University of Canterbury, where he got a job working for a couple of professors who were compiling a database of literature documenting natural marine products. While entering the data, Mike learned a lot about marine organisms. More importantly, he liked what he was learning; so, he came to the University of Washington specifically to study algae.

A normal H. akashiwo cell. Photo courtesy of Mike.

For his dissertation Mike worked in Rose Ann Cattolico’s lab researching the effects of human-mediated environmental change on the physiology of Heterosigma akashiwo, a bloom-forming brown alga responsible for killing thousands of salmon in the Puget Sound during the summer of 2006. Algal blooms are essentially population explosions. They happen when environmental conditions such as temperature and day length are just right to promote extremely rapid growth. Blooms often last only a few days before being disrupted by weather, say by wind pushing them out to sea, but their capacity for devastation far outweighs their brief existence.

The harmful nature of algal blooms varies according to species. Some algal species actually produce and excrete toxins. Others have morphological structures such as spines that damage fish gills. Many algal blooms cause hypoxic, or oxygen deficient, conditions, especially as they decay. This is because following the algal bloom is a population boom of bacteria that feed on the dead algae. Bacteria use dissolved oxygen in the water during respiration. As the bacteria population continues to expand, more and more dissolved oxygen is used, finally resulting in a hypoxic environment. But regardless of the mechanism, the end result is typically a massive die-off of marine creatures in the bloom’s vicinity, such as the aforementioned consequence of an H. akashiwo bloom in the summer of 2006.

Mike investigated the physiological effects of iron limitation on H. akashiwo. Iron limitation occurs in one of two ways: through a reduction in the amount of dissolved organic carbon in the system, which happens when there is less plant matter entering rivers and streams, a typical consequence of deforestation. Or, via eutrophication, the increase in dissolved nutrients in the water usually caused by fertilizer runoff or septic systems leaking near waterways.

An iron-limited H. akashiwo cell. Photo courtesy of Mike.

Observations of algal cultures in the lab experiencing short-term iron limitation show an increase in the quantity of reactive oxygen species (ROS) produced. ROS are toxic to organisms in all trophic levels; a familiar example is hydrogen peroxide. ROS are produced extra-cellularly when carbon secreted from the cell reacts with light. There are a couple of plausible explanations for why algae produce ROS.  It may be an adaptive response to iron limitation because the ROS might actually help transform the iron from an unavailable form to a form available to the algae for uptake. But it may also just be a byproduct of the cell’s secretion of carbon. When iron or other nutrients such as nitrogen or phosphorus are limiting, the cell may excrete excess carbon that it’s not able to use.

Algal cultures in the lab. Photo courtesy of Mike.

Mike tested the hypothesis that prolonged iron limitation leads to an increase in the toxicity of H. akashiwo populations. His research has shown that an increase in ROS production is a stress response to the iron limitation and that the rise is only a short-term response. In the long run, H. akashiwo populations limited by iron are unlikely to evolve greater levels of toxicity through a sustained increase in ROS production.

Nevertheless, reports of harmful algal blooms are on the rise, as are their reported levels of severity. However, it is unclear whether this is because there is a greater effort on the part of scientists to document blooms, or whether bloom frequency and severity are actually increasing. What seems likely is a combination of both. And, as Mike’s research suggests, short-term rises in ROS production caused by human-mediated iron limitation are likely contributing to the rising levels of bloom severity.

Mike finished his dissertation in October of 2007. We are pleased to report that he accepted a job at Imperium Renewables in Seattle to work on biofuel production.