SALISBURY — Dr. Don Anderson, a senior scientist of biology at Woods Hole Oceanographic Institute, will discuss red tides, toxic seafood, green slime and seaweed-covered beaches at the English Speaking Union Salisbury Branch meeting Thursday, April 20, at 6:30 p.m. at the Country Club of Salisbury

Some people might be more familiar with lakes, rivers and ponds covered with green slime that is not only aesthetically unpleasant, but dangerous as well. Now we are hearing about a 5,000-mile mass of seaweed in the Atlantic moving toward the U.S. coast where it will pile up on beaches, preventing swimming or recreation, and decaying and releasing dangerous and even deadly gases. These are just a few of the many natural phenomena that scientists collectively call harmful algal blooms.

This talk, by one of the world’s leading experts on the subject will cover tropical waters and coral reefs in the Caribbean, where fish like grouper or red snapper can be poisonous. In China, our love of sushi is responsible for a natural seaweed disaster of biblical proportions. In the Arctic, warming waters are allowing algae that produce potent neurotoxins to proliferate, threatening local communities dependent on subsistence harvesting of marine animals for their food.

The many manifestations and impacts of these phenomena will be highlighted, as well as the dangers they pose to human society and to ecosystems, their causes (some of which relate directly to pollution, climate change, or other human activities), and new approaches to control and management.

Cost is $40 per person and reservation deadline is Tuesday, April 18.