STUDENT INSTRUCTIONS

Jigsaw

For this jigsaw follow your professor's instructions about which group you are initially in (A, B, or C) and which Figures you are responsible for understanding and explaining. In this jigsaw students first become "experts" in the figures assigned to group A, B, or C. In the second step of the jigsaw students regroup so that A, B, and C experts teach each other.

Remember to use the step one- step two approach to understanding figures and tables that you have practiced in class.

Background information on Pfiesteria

Each of the 5 figures focuses on a fascinating microscopic organism Pfiesteria piscicada. It is a dinoflagellate which is a common in marine environments. Dinoflagellates are single celled and are planktonic (drift in the water), although many forms have flagella and can therefore move. The are metabolically quite versatile; they can photosynthesize, absorb dissolved organic matter (like bacteria do), and also injest particles of organic matter. Dinoflagellates are brownish red in color and when they grow in large numbers (called blooms) the water can look red. Some dinoflagellates cause "red tides", which you may have heard of.

The Pfiesteria story is fascinating from many points of view - ecological, political, personal. Its life history is so bizarre that it sounds like a science fiction story. The politics center around JoAnn Burkholder, a microbial ecologist from North Carolina State University, who is either admired or chided, depending on who you are talking to. The politics are also those of hog industry in North Carolina.

Burkholder's first paper on Pfiesteria piscicada was published in the journal Nature in 1992. Since then researchers have learned a great deal about its highly complex life cycle (more than 20 different stages), its mode of attack on fish and other animals, the action and structure of the Pfiesteria toxin, factors that stimulate the toxic forms to grow in nature, and its presence in other estuaries in the U.S. and globally. There are many websites about Pfiesteria, some listed in the Resources section of this Issue.

Pfiesteria piscicida was discovered by accident when colleague of Burkholder noticed that the fish tilapia held in tanks suddenly died several days after being exposed to water collected in the Pamlico River, NC. The scientists observed that density of a small dinoflagellate increased before fish death and declined rapidly in number unless live fish were introduced. The dinoflagellate produced resting cysts or non-toxic amoeboid forms in the absence of fish (Burkholder et al. 1992). When Burkholder and her colleagues looked for dinoflagellates during massive fish kills in local estuaries, Pfiesteria was abundant, but only when fish were dying. In the journal Nature paper they name Pfiesteria as the causative agent of the many unexplained fish kills in NC estuaries, they identify a neurotoxin from the dinoflagellate as the lethal agent, and they link fish kill events to nutrient enriched Pfiesteria blooms (Burkholder et al. 1992).

In subsequent studies Burkholder reported that toxic forms of Pfiesteria were stimulated by inorganic and organic phosphate (e.g. Burkholder and Glasgow 1997). She became embroiled in arguments with NC officials about the role of the state's hog farm effluents in stimulating Pfiesteria growth. Nitrogen entered the story in the late 1990's when the incredible nutritional versatility of the dinoflagellate became clearer. In addition to consuming dissolved organic compounds (such as in animal waste), Pfiesteria retains chloroplasts from algae that it consumes when fish are not available. Pfiesteria zoospores with these inclusions, called kleptochloroplasts, are stimulated by N and P. In addition to stimulating the growth of Pfiesteria zoospores directly, N indirectly contributes to growth of the dinoflagellate because N is a limiting nutrient for phytoplankton in estuaries. Therefore N loadings stimulate phytoplankton growth which in turn contribute to proliferation of Pfiesteria.

The neurotoxin excreted by Pfiesteria deserves special mention. Until the discovery of Pfiesteria, estuarine ecologists often had a difficult time explaining to legislators and the public how too many nutrients, which sound like good things, could be bad. In addition to the vocabulary problem, nutrient loading does not directly give people diseases or make them sick. For both these reasons, explaining that nutrient loading to estuaries is a severe environmental problem has been an uphill battle.

But Pfiesteria does make people sick. Both Burkholder and Howard Glascow, who works with her, suffered serious neurological effects when they unknowingly inhaled the Pfiesteria toxin. The scientists were hospitalized and affected for months.

Pfiesteria is the first reported dinoflagellate that produces aerosols that seriously harm human nervous systems. Symptoms include acute respiratory problems blurred vision, nausea, vomiting, extreme headaches, and severe memory dysfunction. According to Burkholder and Glasgow (2001) "For days to weeks following exposure, several laboratory personnel could recognize words individually but could not form sentences, perform simple arithmetic, or remember more than the last words of a sentence directed to them. The most seriously affected person in our laboratory, who is a highly intelligent researcher, managed only a 7-year-old's reading level for 3 months after exposure and required reading lessons at first to help regain reading ability … two others … could not remember their names or where they had lived." One of the many controversial aspects of the Pfiesteria story is the degree to which fishermen were harmed by neurotoxin aerosols during Pfiesteria blooms.

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* In step one you first figure out how the figure or table is set up (e.g. what the labels on the axes mean). You also need to have a pretty good idea of the experimental design - how the researchers set up their study - and the hypotheses the study address. In step two you can go on to interpreting the data. For both steps write down any questions you have.