Shore Watchers Tracking Purple Tides
Numerous reports have been coming in concerning “purple water” or “a gelatinous purple mass” in the water. There have been sightings at Roads End, Neskowin and elsewhere (for example, see the latest mile report on Mile 253).
We’re trying to help track this and discover what it is. CoastWatchers spotting anything purplish on the water or beach are asked to file a Dispatch or mile report if at all possible, and in any case contact Fawn Custer, our volunteer coordinator, at (541) 270-0027, email@example.com. If possible, we will arrange for water samples to be taken.
We contacted Dr. Cynthia Trowbridge, an expert on shoreline organisms and known to many mile adopters for teaching many CoastWatch training sessions over the years. She replied: “Without a water sample to see the organism, it would be hard to say. One strong possibility is the planktonic ciliate Mesodinium rubrum that ingests cryptomonads so can be orange, red, purple, or brown. It forms red tides but these are protozoan, not dinoflagellate red tides. The species is common in Oregon at this time of year and worldwide in spring and/or summer. Because ciliates are mobile animals, the blooms pulse and move. They are non-toxic except they do respire so bloom conditions can strip oxygen out of the water column at night at suffocate other organisms. If the specimens jump around like fleas in the water, it would be Mesodinium.”
We also received a comment from Diane Bilderback, our former Coos County coordinator: “Here on the south coast, we have been having a wash up of a pelagic purple tunicate, Dolioletta gegenbauri, that at times causes a deep purple wash on the beach and also has colored small sand pools. This wash has been seen here since 7/8 through 8/23 so far. The wash is in varying amounts. Sometimes it is very heavy with purple bands over a foot wide, thick and gelatinous, and other times it is just a light inch or slightly larger thin but still a purplish colored band. Dave took the photo under the dissecting scope. We wonder if this is the organism that is causing the 'purple colored water' up in the north coast.”
The latest news is that salps are the likely cause. According to a message from Caren Braby, manager of marine resources for the Oregon Department of Fish and Wildlife, “My staff have been communicating with WDFW (Washington Department of Fish and Wildlife) and taken samples at Clatsop Beach. They are a huge bloom of juvenile salps - a gelatinous VERTEBRATE, more closely related to fish than to jellies. This may be an unusual sight for us because of two or more possible (hypothetical) reasons: 1) they may be blooming significantly this year due to unusual ocean conditions, or 2) they are usually out there but this year they are onshore due to the suppressed upwelling (the "blob") pressed up alongshore."
Marine algae expert (and CoastWatcher) Gayle Hansen has offered to attempt to identify the organism for sure if people will bring her samples. If you are able to collect samples (and are within range of Newport) bring them to Gayle at her office in the Environmental Protection Agency headquarters at the Hatfield Marine Science Center. She has observed repeated blooms of Mesodinium in Oregon estuaries and occasionally in nearshore ocean waters. She she notes, “During the Mesodinium bloom in 2004, the oysters at our local oyster farm turned pink -- making them designer oysters! Luckily the ciliate is not toxic and it did not damage the oyster crop. It will be interesting to see if the new bloom is this as well.”
Contact Gayle at 541-867-5012 (lab), firstname.lastname@example.org.
For more images of the “purple tide,” go to the Oregon Shores Facebook page, or to CoastWatch mile 253 to look at photos.
CoastWatcher Range Bayer has supplied links that may be of related interest:
Scientific American, August 11, 2015. "Massive Toxic Algae Blooms May Prove a Sign of Climate Change to Come"
NOAA, August 6, 2015: Record-setting bloom of toxic algae in North Pacific