Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Curation Notes
  • Problem Description
• Data 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). 

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, 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).

Fecal pellet production was measured following the methods described in Drits et al. (1992). Pyrosome colonies were transferred into containers filled with 0.2-µm-filtered seawater and placed under dissecting microscopes to visualize their common cloacal aperture. The number of fecal pellets produced was counted during continuous observations over 2 min. Initially, we observed colony defecation for 1 to 7 min while determining the count period length. Since we observed a noticeable decrease in production over time, beginning after the first ~2-3 minutes, as noted by Drits et al. (1992), we conducted counts for 2 min immediately after transferring the colonies into the observation container.

For biogenic silica estimations, pellets (n = 35-104) collected from the above production experiment, were transferred to a 47 mm diameter track-etched polycarbonate filter (Isopore™), then folded and placed in a cryogenic vial and placed in an oven at 60°C for 24h. Biogenic silica measurements were conducted as described below for water column samples. Biogenic silica concentrations from grouped pellets on the filter was then divided by the number of pellets to obtain individual bSi per pellet measurements.

For biogenic silica [KB1] analysis, seawater samples (0.25–1 L, depending on distance to shore, or biomass) were filtered under gentle vacuum through 0.8 μm pore size, 47 mm diameter track-etched polycarbonate filters (Isopore™). Filters were then folded into quarters (particulate matter inside-facing) and placed in cryovials with the caps slightly loosened, dried in an oven at 60° C for 24 h, and stored until their laboratory analysis (Brzezinski and Nelson 1989). On land, all biogenic particles filtered were digested at 95° C for 40 minutes in a 0.2 N NaOH solution (Paasche 1973; Brzezinski and Nelson 1995). This procedure specifically targets the dissolution of biogenic silica, so lithogenic silica interferences are essentially avoided (Krausse et al. 1983). The samples were digested in HF-cleaned 15 mL TPX® polymethylpentene tubes as recommended in Brzezinski and Nelson, 1995. Immediately after their digestion, the samples were cooled, neutralized with 1 N HCl and centrifuged for 10 minutes at 1200 × g (Brzezinski and Nelson, 1989). The reactive orthosilicic acid content of the supernatant is determined at 810nm via the colorimetric ammonium molybdate method described by Strickland and Parsons (1972). Sodium hexaflurosilicate (Na 2 SiF 6) standard curves (0, 0.5, 5, 20, 50, 100 µmol L-1) were made in deionized water. Standards were treated identically to samples.

bSi on the filter was calculated by computing bSi in umoles in 20 mL  (dividing abs (%) by slope and multiplying by 0.2.) and then multiplying by the dilution factor. 

- Loaded data from Cawleyetal_2026_PelletbSi.csv, set, "nd", and "ND" as missing values
- Renamed columns: "Cycle; transect1=10; transect 2=20;" to Cycle_id, "day/sta" to day_sta_id, "lat [deg_north]" to latitude, "lon [deg_west]" to longitude, "abs [%]" to absorbance, "dilution factor" to dilution_factor, "bSi [umoles in 20 mL]" to bSi, "bSi [umols on filter]" to bSi_filter, "pellets for filter" to pellets_for_filter
- Renamed table 1004017_v1_cawley_pelletbsi

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.