Table of Contents

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

We sampled six cross-shelf transects in the Northern California Current (NCC) along the coasts of Oregon and Washington, USA from March 2-11, 2022 (Winter = W22) and July 20-28, 2022 (Summer = S22) on cruises SKQ202204S and MGL2207. Pelagic tunicates and pteropods were collected using a 4 m^2 Multiple Opening/Closing Net and Environmental Sensing System (MOCNESS, 1 mm mesh) at each station from depths ranging 0 to 100 m. All sampled mucous mesh grazers were from shelf-break or off-shelf sampling stations, and were processed immediately to reduce gut contents being digested or expelled. Animals and/or dissected guts were rinsed in deionized water (DI) to remove salt and preserved at -20 ˚C or in 0.125% TEM-grade glutaraldehyde at +4 ˚C until further processing. 

Large individuals and guts (e.g., T. vagina) were dissected and frozen individually. For small or colonial animals (e.g., D. gegenbauri, P. atlanticum, and L. helicina) groups of individuals or dissected guts were combined into samples of 10-20 individuals. Samples were homogenized in ~10 mL DI using an EtOH-sterilized 15 mL glass mortar and pestle. Homogenized material (1-2 mL) was filtered onto a 0.2 µm nucleopore filter (Whatman) using vacuum filtration and the remaining homogenate was preserved as above. The homogenization process was done shipboard in S22. In W22, animals were frozen at sea and homogenized as above in a shore-based lab.

To analyze the planktonic prey fields from surrounding seawater, we collected surface seawater in S22 from 0-25 m deep using a CTD Rosette, from one of 24 12L Niskin Bottles at each station. Exact sampling depth was determined at each site based on real-time CTD measurements (salinity, temperature, fluorescence) to select for highest likely prey field abundance.

Seawater was immediately filtered onto a 0.2 µm nucleopore filter. The goal of water filtration was to concentrate available prey for imaging, so the volume filtered varied between 300-1000 mL depending on prey density and feasibility of filtration. Filters were rinsed with freshwater to reduce salt crystals which impair ESEM imaging. Filters were gently rolled and transferred to 1.8 ml cryovials containing 0.125% TEM-grade glutaraldehyde in freshwater and frozen (-20˚C) or refrigerated (4˚C) until imaging.

A small volume (~10 µl) of homogenized samples was imaged using bright field microscopy on a Nikon epifluorescence compound light microscope equipped with a Nikon D850 camera. Quantitative image analysis was performed on images generated using an Apreo (ThermoFisher) scanning electron microscope from the Center for Advanced Materials Characterization in Oregon facility (University of Oregon). Nucleopore filters were cut into 1 mm square pieces and affixed to double sided tape on the Apreo imaging stage and immediately imaged.

All prey items were identified to the lowest taxon possible from ESEM and bright field images. To compare prey sizes in the gut of each grazer, we measured a subsample of prey items by applying grids with 500,000 pixels2 to ESEM images using ImageJ, version 2.16.0/1.54p (Schneider, 2012). All potential prey items were identified, enumerated, and measured when 75% intact from randomly selected grids until 100 prey items were measured and the grid completed. Prey items were manually outlined, with major and minor axis lengths obtained. 

Two station locations, CR-4 and CR-3, were sampled, but not processed for prey size. The CTD summary data is included. 

- Imported "CTD summary data_BCO DMO.xlsx" and "ESEM data_BCO DMO.xlsx" files into the BCO-DMO system
- Normalized all station ids and season information, creating combination identifier to join on
- Removed W (mm), H (mm), and area (mm-2) parameters to reduce duplication
- Joined data sources on station ids and season information
- Added local and UTC datetimes of sampling from submitter
- Replaced µm → um in all values to since that's not an accepted charater in our system
- Renamed parameters for clarity and to comply with BCO-DMO recommendations
- Changed "H" parameter name to "L" to reflect length
- Added field for scale and move information from file names to the scale field
- Added default value of 100 to the scale values that were empty
- Added LSID and AphiaIDs to dataset for grazer species (all names were accepted when checked on 2-25-05-22)
- Exported file as "962096_v1_ctd_prey_size.csv"

NSF Award Abstract:
Marine microorganisms are among the most abundant life forms on the planet, playing a key role in ocean nutrient cycling. Though predation on these microorganisms is critical to nutrient cycling, little is known about their interactions with predators - specifically the direct interaction between microorganism cell surfaces and predator capture surfaces. This project examines how cell surfaces may influence the predation of marine microorganisms. Cell surface modification is a recognized strategy for predator avoidance among terrestrial microorganisms, but its application in the ocean is largely unexplored. By examining microbial prey with varying surface characteristics and predators with a range of feeding strategies, this research is providing foundational knowledge for future ocean food web models. This project engages public audiences through exhibits and workshops at museums (e.g., Oregon Museum of Science and Industry) and coastal aquariums with a focus on predator-prey interactions in the ocean from small microbial prey to larger predators. A large-scale art installment emphasizes these food web interactions. These 'Eco Murals' focus on ocean ecosystems and involve participation from community members, especially underrepresented minorities. This project is training the next generation of scientists by involving graduate and undergraduate students in research, professional development, and scientific communication. This research includes independent graduate student research as well as capstone projects in Bioinformatics and Genomics. Undergraduate students participate in this research following the previously successful NSF REU Exploration of Marine Biology on the Oregon Coast model. Finally, by leveraging initiatives aimed at promoting the persistence of historically underrepresented and underserved populations in STEM fields, this project recruits, supports, and retains female, first-generation, and underrepresented minority students.

The differential selection and rejection of microbial prey alters our understanding of carbon fate and nutrient cycling in the ocean. This project directly tests the effects of microbial surface properties on particle selection by globally abundant suspension feeders. Cell surface properties are known to be a fundamental aspect of predation avoidance in terrestrial microbes, but the role of microbial surface properties in avoiding or enhancing predation is a research frontier in ocean science. This knowledge gap limits understanding of microbial mortality, microbial loop function, and prediction of ecosystem response to future climate scenarios. This research links specific particle properties with ecologically-relevant trophic interactions through experiments with widespread suspension feeders representing major feeding strategies by copepod nauplii, pteropods, appendicularians, and echinoderm larvae. First, this project quantifies the surface properties of major marine microbial groups to inform feeding incubations with artificial prey. Second, artificial microspheres with varying surface properties are used in controlled laboratory feeding incubations to determine selectivity and third, to quantify particle fate from released fecal pellets and pseudofeces. Finally, the major marine microbial taxa in the guts of wild-caught suspension feeders are quantified using qPCR. This research forms an integrative approach, yet the results of each objective have scientific impact which can be applied to diverse fields beyond the ocean.

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.