Between 2015 and 2018, fishermen off the coast of Oregon were baffled and alarmed by the sudden appearance of thousands of rod-shaped, jelly-like animals fouling their gear and dominating their catches. Beachgoers, too, were fascinated by these creatures that, at times, appeared to form a blanket on the sand when washed up in the surf. These animals, or rather colonies of thousands of very small animals, are called pyrosomes. They are typically considered a warm water species, rarely encountered north of southern California. But, since 2015, pyrosomes have become increasingly abundant in the Northern California Current (NCC) off the coast of Oregon and even up into the Gulf of Alaska. So abundant, that a 2017 fisheries survey caught 18,000 pyrosomes in a 5-minute trawl. There have been only a few studies conducted, globally, on pyrosomes and this lack of information is limiting scientific understanding of the implications of increased pyrosome occurrence in the NCC. The aim of our research was to determine the effect of pyrosomes on the local marine food webs of the NCC by measuring the amount of the microscopic algae (also known as phytoplankton) they can consume compared to the amount available. We were curious to know if they could consume a large percentage of the phytoplankton that fuels Oregon’s fisheries and marine ecosystem. We discovered that these microscopic creatures that live in large tubular colonies can eat a lot. And really fast. In fact, they are able to eat phytoplankton so fast that when they are found in large numbers, as they were off Oregon in 2015-2018, they can mow down nearly a quarter of the phytoplankton in their path. This is concerning to us because phytoplankton is an important food source for many other small creatures drifting in the ocean, like krill (small shrimp-like crustaceans) and copepods (even smaller crustaceans), which are incredibly important food for young fish (including salmon, cod and rockfish), whales and seabirds. The ability of pyrosomes to remove large amounts of phytoplankton also has the potential to alter the marine carbon cycle (and other elemental cycles, such as nitrogen), and when they die and sink to the seafloor, and bacteria get to work decomposing them, pyrosomes may also affect oxygen concentrations near the seafloor. Intellectual Merit: Our study provides important data to help scientists better understand the potential impact of pyrosomes not only off the Oregon Coast, but also more broadly throughout the Northern California Current and even the Gulf of Alaska, where pyrosomes have also become more abundant in recent years. The results of our research will further advance scientific understanding of pyrosomes at a global level, since so few studies had been conducted on this group in the past. With global climate change, invasive species, including tunicates (the subphylum in which pyromes belong), have become a prevalent force due to their poleward expansion. It is vital that we have a good understanding of the biological function of all oceanic species, and especially those for which information is lacking. Expansion upon our knowledge of pyrosomes provides insights into the ecology of tunicates, the impacts of invasive species, and the effects of climate change on biological oceanography in general. Broader Impacts: Two undergraduate students joined the project in the summer of 2018. These students gained valuable experience in conducting field experiments, analyzing data, and participating in day-long research cruises to collect specimens. One of the REU students was subsequently hired on as a Faculty Research Assistant for the project and received additional laboratory training, participated in longer research cruises conducted on large vessels, presented her findings at an international conference, and is the first author of the peer-reviewed publication associated with our work. Throughout the course of the project, we participated in a variety of outreach opportunities to disseminate the results to the public and to other scientists. Outreach events included (i) Da Vinci Days, an annual Corvallis science fair with 4000 attendees, (ii) the Haystack Rock Library Lecture Series with 20 attendees, (iii) the Corvallis Maker Faire with 942 attendees, and (iv) Hatfield Marine Science Day with 1700 attendees. At these events, we had a mix of small talks, posters, slide shows, 3-D printing demonstrations, and preserved specimens that we used for educational purposes. In addition, we regularly posted about pyrosome work on the Newportal Blog, a blog run by NOAA Northwest Fisheries Science Center that gets ~200 hits a month. We presented our findings at the PICES (North Pacific Marine Science Organization) 2018 Annual Meeting in Yokohama, Japan and at the 6th International Jellyfish Bloom Symposium in 2019 in Cape Town, South Africa. We also contributed to the development of a teaching activity in collaboration with the Oregon Science Teachers Association through the Anchoring Phenomena webpage (https://oregonscience.org/Oregon-Phenomena). Last Modified: 10/01/2020 Submitted by: Kim S Bernard