Award: OCE-2125407

Marine plankton form the foundation of oceanic food webs yet predicting how these communities will respond to climate change remains a critical challenge. The SPECTRA project addressed this gap by investigating how environmental gradients influence plankton community structure and function in the northern California Current (NCC), a dynamic and highly productive eastern boundary current system. The project focused on quantifying spatial and temporal variability in plankton size spectra—a proxy for ecosystem functioning—across gradients in temperature, nutrients, oxygen, and pH. Using advanced imaging tools including the In Situ Ichthyoplankton Imaging System (ISIIS) and a LISST particle imager, researchers captured high-resolution data spanning ten orders of biomass magnitude. These data were coupled with depth-discrete mesozooplankton sampling to assess shifts in community composition, carbon content, and stoichiometric ratios. By integrating in situ imagery, morphometric data, and biochemical analyses, SPECTRA contributed to a mechanistic understanding of plankton dynamics and improved predictive models of ecosystem response to climate change.

SPECTRA generated a rich set of findings that advance our understanding of plankton community dynamics, trophic interactions, and ecosystem responses to environmental variability. An edge computing system aboard research vessels enabled real-time classification of in situ plankton imagery into 170 classes. This innovation allowed adaptive sampling in response to ephemeral oceanographic features, transforming how oceanographic data are collected and analyzed. New code produced simultaneous automated measurement of individual plankton sizes. The collection of 11.2 billion plankton images enabled the measurement of plankton size spectra in the NCC at unprecedented resolution. A portion of these images coupled with microbial data showed that intermittent upwelling systems are structured by microbial loop taxa, while continuous upwelling systems are more influenced by primary production. These findings highlight the potential resilience of microbial-driven communities to environmental shifts. Specific findings across mesozooplankton taxa addressed aspects of growth and trophic dynamics. Researchers found that the larvae of myctophids grew faster and had fuller guts during moderate upwelling conditions, with seasonal dietary shifts from copepod nauplii to calanoid copepods. These results suggest a dome-shaped relationship between upwelling intensity and larval growth, with implications for recruitment success. Genetic identification of larval rockfishes is producing the first species-specific distribution maps of larval rockfishes in the NCC. ISIIS imagery enabled measurement of the effect of low oxygen on larval fishes, their prey, and predators, providing a deeper understanding of the effects of changing ecosystems. Analysis of prey availability and food web structure for a forage fish, the northern anchovy, indicate that larval anchovy trophic position is negatively related to growth rate and that anchovy recruitment strength is related to degree of anchovy overlap with their prey. Project data provided the first map of the distribution of Dungeness crab zoea in the NCC, useful for biophysical modeling and experiment parameterization. Gelatinous zooplankton such as doliolids and salps were found to consume a wide range of microbial prey, including picocyanobacteria and archaea, expanding our understanding of microbial mortality and nutrient cycling. Gut content and fatty acid analyses of a numerically abundant ctenophore showed a significant role in NCC food webs, with contributions to energy transfer across trophic levels. More broadly, stable isotope analyses revealed that gelatinous zooplankton span 4-7 trophic levels. Together, these findings underscore the importance of integrating high-resolution imaging, biochemical analyses, and ecological modeling to understand plankton dynamics in variable environments.

SPECTRA supported a diverse and far-reaching set of broader impacts. Each of four major research cruises involved ~20 scientists, providing at-sea training for 5 postdoctoral fellows, 12 graduate students, 4 REU interns, and 11 undergraduate students. Additional undergraduates participated in sample and image processing. In collaboration with the Sitka Center for Art and Ecology, 5 professional artists and a filmmaker joined research cruises and created original works inspired by their experiences. A 2023 participant was inspired to pursue a subsequent Arctic expedition. Another released a music album and held live performances in New York based on her time at sea. A short film, Life at Sea, was screened at two international film festivals. During Ocean Week each year of the project, students from Edison Elementary School in Eugene, Oregon interacted with scientists, plankton sampling equipment, and specimens. Similarly, >2000 members of the public engaged with the project each year during Hatfield’s Marine Science Day. Project researchers also continued their efforts with Plankton Portal, a citizen science platform that invites the public to classify plankton images, and helped design the new Plankton Exhibit in the HMSC Visitor Center. SPECTRA’s automated image analysis pipeline is being made openly available to the oceanographic community. ISIIS imagery is contributing to the Global Plankton Imagery Library, and size spectra data will be shared with ecosystem modelers to support climate change forecasting. These broader impacts reflect the project’s commitment to interdisciplinary collaboration and public engagement. By integrating art, education, and open data, SPECTRA has created lasting connections between ocean science and society.

Last Modified: 12/05/2025
Modified by: Su Sponaugle