Warming California Waters Cause wandering Hopkins’ Rose Nudibranch Species

By. Ashley Gustafson


Hopkins' Rose Nudibranch

Nudibranchs, better known as sea slugs, are an incredibly beautiful, hypnotizing, and  often Technicolor animal found in oceans all over the world. Just like any ocean dwelling  animal, certain species of sea slugs have specific temperature requirements and limitations of the water they reside within. As the global average temperature increases so does the average ocean temperature causing a shift in many marine organisms’ original domains.

One example of this has been seen in the Hopkins’ Rose nudibranch. It is normally found in Southern California and until recently has rarely been spotted farther North than San Francisco. These inch-long, pink sea slugs have exploded into rocky tide pool ecosystems along the central and northern coastline of California. Scientists at the California Academy of Sciences attribute this to the increased temperature of California’s coastal waters. They also believe this bloom may signal a much larger shift in ocean climate and another forthcoming El Niño. Since the discovery of this new development of sea slugs earlier this year, these researchers along with the University of California Santa Barbara (UCSB), the University of California Santa Cruz (UCSC), and Bodega Marine Laboratory have been tracking this unusual settlement. In the past, scientists have seen these pink nudibranchs farther north during strong El Niño events (that cause rise in temperature) but only for short periods of time when the warmer-than-normal ocean temperatures last. The last time this occurred was in 1998 and before that was 1983. This current bloom in particular is out of the ordinary since there is not an official El Niño on record yet for 2015, so it seems these warming temperatures are coming from some other source. The researchers predict this other source is one of a much larger scale shift in the eastern Pacific Ocean. These warmer ocean temperatures first showed changes in ocean dwelling organisms nearly four decades ago in 1977.

Following the warming waters?

While it is exciting to see such beautiful animals, that are normally rare, so abundant and widespread, it causes concern for future consequences of this changing coastal ecosystem. Warmer coastal waters change the ranges of not only these sea slugs but other aquatic animals like dolphins, sea turtles, several fish species, gastropods, and numerous other aquatic animals. While this new warmer water habitat allows the Hopkins’ sea slug to thrive, it has several other consequences that can hurt others. For example, warmer water coastal waters generally mean less food for sea birds. Another example could be the changes in the ranges of large predators like sharks. The new ranges could introduce new prey species to the predators. Having never seen or had to escape these large predators before could make these new prey animals easy targets for the expanding predators thus causing a massive population decline in the prey species. This rapid change does not allow much time for adaptation for numerous coastal species and could lead to mass extinctions in the next several decades.

As previously stated, studies have linked widespread nudibranch booms with times of increasing water temperatures. Hopkins’ Rose nudibranchs are perfect candidates for tracking rapid changes in ocean conditions. They have fast-growing populations but only live for about one year. In 2011, a report in Limnology and Oceanography went further to predict a range-shift in sea slug populations when warm temperatures, northward ocean currents, and weak upwellings overlap. This phenomenon causes cold water full of nutrients to push into the ocean’s surface. This is the exact conditions that are occurring in California and causing this influx of pink nudibranchs right now.

While this is an exciting and fascinating change it is important for scientists to keep tracking the movements and patterns of these nudibranchs, not just for their sake, but also for the sake of other coastal marine animals. By recording and studying the movements and patterns of the Hopkins’ sea slug it is possible to have more conclusive predictions not only of their future, but the rest of the California Coast as well.