A plankton bloom in the Baltic sea.  Credit: ESAHarmful algal blooms (HABs) are scary things.   The occur when populations of algae explode in coastal environments.  The algae suck up the oxygen and release neurotoxins into the water, and even the local air.   Fisheries and beaches have to be shut down.  People have been killed.  HABs aren’t predictable, but its clear that they more damaging and more common than they were in the past due to nutrient pollution in coastal areas.

Some recent studies on HABs have got me thinking about the long-term effects of these events. 

First, Melissa Miller and her team document a new threat - transport of toxins from HABs across space and up the food chain.  In an excellent forensic study, they traced the the death of sea otters in Monterey Bay to toxins released by an algal bloom in a freshwater lake 8 km inland.  While the toxins that flowed out to sea in small amount, they were accumulated and concentrated by filter-feeding clams and mussels, the otters’ favorite foods.

On the other side of the planet, a team of researchers have published an account of the damage wreaked by a HAB that spanned over 500 square kilometers.   They studied the effects of the bloom on two coral reefs and found massive changes in their community structures.  The mechanism? “Changes in species composition at both locations were mainly due to the reduction and/or complete elimination of the majority of species.”

The authors suggest that HABs have similar effects to severe coral bleaching event.   As I’ve discussed before, such events can result in regime shifts that are very hard to reverse.

To me, these studies highlight the potential for HABs, and other sudden events, to induce long-term changes in ecology and ecosystem services that extend far beyond the scope of direct damage from the blooms themselves.  In particular, I wonder about their ability to cause chains of cascading regime shifts.   Stephen Carpenter recently published a paper describing the forecasting problems posed by such cascades.  Suffice to say, we don’t know how to do it yet.

ResearchBlogging.org  HEISLER, J., GLIBERT, P., BURKHOLDER, J., ANDERSON, D., COCHLAN, W., DENNISON, W., DORTCH, Q., GOBLER, C., HEIL, C., & HUMPHRIES, E. (2008). Eutrophication and harmful algal blooms: A scientific consensus Harmful Algae, 8 (1), 3-13 DOI: 10.1016/j.hal.2008.08.006 

Miller, M., Kudela, R., Mekebri, A., Crane, D., Oates, S., Tinker, M., Staedler, M., Miller, W., Toy-Choutka, S., Dominik, C., Hardin, D., Langlois, G., Murray, M., Ward, K., & Jessup, D. (2010). Evidence for a Novel Marine Harmful Algal Bloom: Cyanotoxin (Microcystin) Transfer from Land to Sea Otters PLoS ONE, 5 (9) DOI: 10.1371/journal.pone.0012576 

ResearchBlogging.orgBauman, A., Burt, J., Feary, D., Marquis, E., & Usseglio, P. (2010). Tropical harmful algal blooms: An emerging threat to coral reef communities? Marine Pollution Bulletin DOI: 10.1016/j.marpolbul.2010.08.015 

ResearchBlogging.orgBrock, W., & Carpenter, S. (2010). Interacting regime shifts in ecosystems: implication for early warnings Ecological Monographs, 80 (3), 353-367 DOI: 10.1890/09-1824.1