From Spain to New York, jellyfish are becoming more numerous, and they’re showing up in places where they have rarely been seen before. Scientists say this explosion can be attributed to a combination of overfishing, rising sea temperatures, and pollution. Find out all about jellyfish, why they’re thriving, and whether their rise is signaling the ocean’s decline. Dr. Jennifer E. Purcell is a Marine Scientist at Shannon Point Marine Center and Adjunct Professor at Western Washington University; Dr. Monty Graham is Assistant Professor in the Department of Marine Sciences at University of South Alabama and Senior Marine Scientist at Dauphin Island Sea Lab.

Weigh in: Have you noticed more jellyfish than usual at NYC-area and NJ beaches? Has it affected your swimming habits?