Project: RAPID: The ecological role of Pyrosoma atlanticum in the Northern California Current

NSF Award Abstract:
In the last three years, fishermen off the coast of Oregon have been baffled and alarmed by the sudden appearance of thousands of rod-shaped, jelly-like animals, called pysrosomes, fouling their gear and dominating their catches. Beach-goers, too, have been fascinated by these creatures that can blanket the sand when washed up in the surf. This warm water species was rarely encountered north of southern California until the last three years, when they have become increasingly abundant in the Northern California Current (NCC) off the coast of Oregon and even up into the Gulf of Alaska. A recent fisheries survey caught 18,000 pyrosomes in a 5-minute trawl. The effect on local marine food webs is not clear, but pyrosomes could compete with other important species for food, potentially changing the marine food web of the NCC. Few studies have been conducted so understanding of the implications of increased pyrosome occurrence is limited. There is thus an urgent need to learn more about the species. This project provides insight into the possible ecological effects of pyrosomes in the NCC. The study will also benefit researchers working in other regions, like the Gulf of Alaska. Broader impacts will be strengthened by outreach. An undergraduate student will work on the project over the summer, gaining valuable research experience. The research team will create a display about pyrosomes in collaboration with the Visitor Center at the Hatfield Marine Science Center (Newport, OR). The lead investigator on the project will also work with the media outreach team at Oregon State University to produce a high-quality popular science article about the research to be distributed via various media streams, including online, in print, and via social media.

Pyrosoma atlanticum (commonly known as the pyrosome) is a warm water species of pelagic colonial tunicate that until recently had not occurred north of southern California. However, in the last three years, pyrosomes have become increasingly abundant in the Northern California Current (NCC) off the coast of Oregon, and as far north as the Gulf of Alaska, with implications for ecosystem productivity and fisheries. Preliminary data collected by the investigators show that pyrosome colonies off the Oregon Coast have extremely high grazing rates, suggesting that pyrosome blooms are capable of grazing significant amounts of phytoplankton standing stock. Indeed, in other parts of the world oceans, pyrosome blooms are capable of removing more than half of the phytoplankton standing stock in the top 10 m of the ocean. Pyrosome blooms in the NCC could outcompete other zooplankton grazers, such as copepods and euphausiids, thereby negatively affecting the higher trophic levels that rely on those crustaceans as prey. The effects on the food chain are likely to be significant. Pyrosomes have already been recorded in the stomach contents of a number of fish species, including Pacific halibut, rockfishes, sablefish, and Pacific salmon, yet their caloric content is half that of these fish species' preferred prey, krill. With increasing frequency of pyrosome blooms, there is an urgent need to assess their potential ecological implications in the NCC. Scientific understanding of the ecological role of pyrosomes in the global oceans is severely limited and the effects of the unprecedented continuous large blooms of pyrosomes in the NCC are unknown. This project is an intensive study on the role of pyrosomes in the pelagic food web and biogeochemical cycles of the NCC to answer the following research questions: (1) What proportion of the phytoplankton standing stock do pyrosome blooms remove daily? (2) What size fraction of the phytoplankton do pyrosomes preferentially graze upon in the NCC? (3) What is the contribution of pyrosomes to the flux of organic matter to the sea floor in the NCC?

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.