When Roses Bloom in Northern California, Researchers Take Notice

While the presence of small pink roses may seem like an innocuous blossom, researchers from the University of California, Santa Cruz are finding that as little creatures appear they signal warmer waters to come. No, these pink roses aren't flora species, they're hot pink sea slugs found traditionally in southern California tide pools. But as they've migrated north, researchers now believe that coastal water temperatures are on the rise, and this could have serious implications farther up on the food chain.

The culprits, known as Hopkin's Rose Nudibranch (Okenia rosacea), may be fun to look at, but now that they've appeared in ample abundance marine biologists are starting to take notice. 

Though surveys of tide pools in southern California often find Hopkin's Roses within them, the transects of northern California tide pools are often devoid of the creatures. But as the water temperatures are warming up and down the coast, researchers at universities like the University of California, Santa Cruz are finding the sea slugs in a shocking abundance. In fact, in a series of surveys conducted in the past few weeks in tide pools ranging from Humboldt County to San Luis Obispo, university researchers have reported the highest and northernmost records of the species since the strong El Niños of 1983 and 1998.

"We haven't seen anything like it in years. These nudibranchs are mainly southern species, and they have been all but absent for more than a decade" UC Santa Cruz professor emeritus of ecology, John Pearse says. "What makes this event especially exciting for us is that in 2011 we published a paper in which we predicted that oceanographic conditions like we are now experiencing would be marked by heavy recruitment of these and other nudibranchs." 

"It's just wonderful to see the prediction coming true."

Some researchers have said thus far that global warming may be a contributing factor to the warmer ocean temperatures worldwide, however, Pearse and his colleagues believe that the far more localized conditions point to another cause altogether. Initially the team considered an oncoming El Niño event to be the culprit, seeing that past events occurred during El Niño events, marked by periods of heavy rainfall and warmer-than-average ocean water temperatures. However, in a recent study by the National Oceanic and Atmospheric Administration (NOAA)  researchers found that 2015 only shows a minimal chance of an El Niño event, if any at all.

"Similar to last month, most models predict SST anomalies [will] remain at weak El Niño levels during December-February 2014-15, and lasting into the Northern Hemisphere spring 2015. If El Niño were to emerge, the forecaster consensus favors a weak event that ends in early Northern Hemisphere spring" NOAA researchers said in a recent ENSO Alert. "In summary, there is an approximately 50-60% chance of El Niño conditions during the next two months, with ENSO-neutral favored thereafter."

Instead, according to most intertidal researchers along California's coast, the likely culprit are rare wind patterns that are allowing warm surface waters to remain, boosting the intertidal temperatures high enough for Hopkin's Roses and other species to flourish. But while the sights of the tide pools may be something fun to look at while they last, researchers like Dr. Terry Gosliner of the California Academy of Science caution that the implications of these warmer waters may be far worse the public realizes.

"Our current climate conditions are great for some of my favorite slugs, but we can't ignore that warming seas mean less food for sea birds, and adverse impacts for all marine ecosystems" Gosliner says. "California's unique marine life can't always adapt to so much instability."