![]() ![]() Last year, some beaches were closed to swimming if the number of Man-o-War or jellyfish were in great abundance. Where the Man-o-War were found recently, the Town of Nantucket Harbormaster reported the beaches with purple flags on the daily beach report. And be aware that while the tentacles are more dangerous in the water (because they are more difficult to avoid) they can even fire when dead on the beach, so avoid them whenever possible. Beach conditions are posted daily by 11 am at the Insider’s Guide to Nantucket: /beaches. Based on their behavior last year, keep an eye out for warnings before headed to the beach. That, coupled with the south wind we recently had, brought the Man-o-Wars in to the south shore beaches of Nantucket. This combination, while detrimental to some, has created a suite of conditions where Portuguese Man-o-War can thrive. Rising ocean temperatures are coupled with reduced oxygen levels in the water. With this warming comes changing patterns for marine species which are either seeking cooler waters or following changing ocean currents. Similarly, our ocean waters are warming off New England at a faster rate than many other areas. June 2023’s global average temperature was the hottest June on record and we’re on trend for 2023 to be the warmest on record. Why so many all of a sudden? As ocean temperatures begin to rise on average due to global climate change, the Portuguese Man-o-War population has also begun to rise in number. Last year, several beaches were closed because of the “hazardous marine life” including Man-o-War and related jellyfish species. On Nantucket, we typically have reports of a few each year, but the past couple of years we’ve seen greater numbers. ![]() More sightings of the Portuguese Man-o-War in northern waters are anticipated as ocean warming continues. Occasionally, some colonies have even been observed in Irish and British coastal waters when they float on the currents or in the gusts of wind as far north as the Bay of Fundy in Canada. They typically live in tropical or subtropical climates in coastal and open-ocean environments. But they have a broad distribution and can be found in the Indian Ocean, the Pacific Ocean, the Atlantic Ocean, and even the Caribbean Sea. Portuguese Man-o-War are generally found in larger numbers further south. The sting isn’t deadly to people, but it packs a punch that can cause welts on exposed skin. Their tentacles contain stinging microscopic capsules loaded with coiled, barbed tubes that deliver venom capable of paralyzing small fish and crustaceans. This is why they are often found on the beach in the wrack line they can’t really avoid the shore. The pneumatophore (the balloon-like top part) can act like a small sail catching the breeze. There is no propulsion device, such as fins, and the Man-o-War travel only by tides, currents, and winds. ![]() Lastly, the gonozooids are tentacles that serve a reproductive function. The gastrozooids are tentacles that digest food and nutrients coming into the organism. The dactylozooids are tentacles filled with venom-filled nematocysts. ![]() It is filled with atmospheric gasses, primarily carbon monoxide. According to NOAA (National Oceanic and Atmospheric Administration), “Each of the four specialized parts of a man o’ war is responsible for a specific task, such as floating, capturing prey, feeding, and reproduction.” The pneumatophore is the balloon-like structure that is visible above the water line. A siphonophore is unusual in that it is comprised of a colony of specialized, genetically identical individuals called zooids (sort of like clones) with various forms and functions, all working together as one. During the day, the Man-o-War tentacles coil up, and appear thicker and shorter, but when they fish for prey at night, the tentacles extend out further, difficult to avoid for a swimmer.Ĭounter to popular belief, Portuguese Man-o-War are actually not a jellyfish as all, but rather a siphonophore. Known for its vibrant blue and pink colors, Portuguese Man-o-War has a gas filled bag on top with tentacles that can extend up to 30 feet in length. By the time this article is printed, I expect there will have been more sightings. Last weekend, the first Portuguese Man-o-War of the season were spotted off of Cisco and Ladies Beaches. Director of Research & Education at the Linda Loring Nature Foundation ![]()
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