Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Curation Notes
• Data Files
• Supplemental Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Samples were collected on CCE-NSF process cruise (OCE-1637632, Project: California Current Ecosystem Long Term Ecological Research Site). 

Pyrosome colonies for production and sinking experiments were collected from the upper 40 m of the water column using a vertically towed 202 µm net equipped with a 30 L non-filtering cod-end. Tows were preferentially conducted at night, as organisms exhibited distinct DVM behavior, which was possible during the Offshore cycle; however, for the transects we conducted, these tows were conducted whenever the ship arrived on station. For fecal pellet production experiments, colonies were gently transferred from the cod-end, ensuring that no air entered the common canal of the organism, and placed in an appropriately sized container (allowing the organisms to be submerged in typically ~500 mL, but we used containers of up to 1.5L for a handful of large specimens) filled with filtered 0.2 µm seawater for microscopic evaluation. Pellet production experiments were only conducted during the Offshore cycle and the two transects (CCT and AT), while fecal pellet sinking rate determinations were conducted during Onshore 2, Offshore, and one transect (CCT).

After the production experiments were concluded, pellets were collected for sinking and aging experiments. A subsample of the produced pellets was allowed to sit in natural seawater for 24 and 48 hours and evaluated for sinking rates; these were referred to as ‘aged’ pellets.

To measure sinking rates, we took subsamples of both fresh and aged pellets and sank them in an acrylic tank. Pellets were first imaged with a Zeiss Stemi 508 stereomicroscope equipped with a Canon EOS 77D camera to estimate their size. The major and minor axes of the fecal pellets were measured using Image J (n = 237 pellets), with measurements down to the nearest 1 µm. After imaging, pellets were transferred to an acrylic container to estimate the sinking rate. The sinking container was 6.5 x 4 x 16.5 cm, and had marked lines at 0, 5, and 10 cm. Each pellet was gently transferred with a pipette and placed above the starting line to account for any acceleration caused by the pipette's release. The stopwatch started when the pellet crossed the 0 cm line, and the time was recorded when the pellet reached the marked lines at 5 and 10 cm. A total of 247 pellet sinking rates were obtained following this approach.

* Loaded `Cawleyetal_2026_PelletSinking.csv` treated empty strings and 'nd' as missing values.
* Formatted the `time` column by zero-padding values to four digits: `930` became `0930`, `500` became `0500`, and `0` became `0000`, `20` became 0020
* Combined `Year`, `Month`, `Day`, and padded time into a new `ISO_DateTime_UTC` column using `%Y`, `%m`, `%d`, and `%H%M`, and formatted the result as `%Y-%m-%dT%H:%M`.
* Renamed columns to remove special characters and spaces.
* Renamed the table from `cawleyetal_2026_pelletsinking` to `1003542_v1_sinkingrate`.

NSF Award Abstract:
A key component of the ocean food web is comprised of floating animals, or zooplankton, that transfer energy from phytoplankton to fish, whales, and birds. Zooplankton include many different types of organisms that can be broadly categorized as crustacean or gelatinous, with most fish and whales preferring crustaceans as a fat-rich food source over gelatinous animals, which are higher in water content. Historically, the California Current ecosystem off the U.S. West Coast has been dominated by crustacean zooplankton, such as krill and copepods, but in 2014 there were huge abundances of a type of colonial, gelatinous zooplankton known as pyrosomes, which caused widespread damage to fisheries by fouling fishing gear and dominating catch. Although the arrival of pyrosomes coincided with an extensive marine heatwave, lower abundances have since persisted despite a return to cooler ocean temperatures. Analysis of time series data from the California Cooperative Oceanic Fisheries Investigations (CalCOFI) indicate that pyrosomes were also observed in the California Current many decades ago when the ocean was not particularly warm. This study combines analysis of past samples from CalCOFI, ocean circulation models, and biological models to understand the causes of these quickly growing pyrosome populations in the California Current. It supports training for undergraduate and graduate students. In addition, the project is reaching K-12 students through a unique partnership with the San Diego County Office of Education that is developing Next Generation Science Standards (NGSS)-aligned resources for middle and high school science teachers in California. The educational resources are being disseminated through the California Science Project and California Environmental Literacy Initiative. Public outreach in San Diego (CA) is through the Enhancing Your Horizons San Diego conference and the San Diego Regional Competition of the National Ocean Sciences Bowl, and in Santa Cruz (CA) through the Seymour Marine Discovery Center.

Predicting how ecosystems respond to accelerating climate change is a major challenge. The recent appearance of the pyrosome Pyrosoma atlanticum in the California Current is a major perturbation to the ecosystem, and the cause remains unknown. Both ocean physics and plankton food-web dynamics are key determinants of variability in pelagic community composition in this ecosystem, yet unraveling the degree to which variability in physics (through warming and advection) combines with shifting biological interactions (through nutrient cycling and altered food-web dynamics) to determine composition and function is complicated. This project combines the analysis of past historical samples from seven decades of the CalCOFI time series, data-assimilative and non-data assimilative ocean circulation models, and biological population models to determine the role ocean physics and biological interactions have played in shaping pyrosome abundance, trophic dynamics, and population growth and mortality in the California Current. This novel framework is providing mechanistic understanding that is required to predict how plankton communities respond to climate change.

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.