Algae are nutritious organisms that lie at the base of many marine food chains. But there seem to be more stories about harmful algal blooms (HABs) sickening both people and animals in recent years. We asked Dr. Raphael Kudela of UC Santa Cruz to explain what’s going on. … “A nice meta-analysis a few years ago took global datasets and looked for an increase in HABs. It showed that globally, there has not been a consistent increase. But if you break it down by region and organism, some regions are seeing increases, some are flat, and some are decreasing. We’re interested in where HABs are happening more. We see problems where we’re putting extra nutrients into the water, for instance through wastewater discharge. Urea, ammonia, and other forms of nitrogen pose particular problems. We also suspect that climate change is having an effect.”