Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Data comes from VERTEX-style, surface-tethered, drifting sediment trap deployments. Particle interceptor tubes were deployed on cross-pieces with 16 tubes attached. Tubes were deployed with a dense formaldehyde brine created by adding NaCl and formaldehyde to filtered seawater. After recovery, overlying seawater was removed from each cruise by gentle suction. Tubes were then gravity filtered through a 200-micron nitex mesh filter, and the 200-micron filters were carefully analyzed under a stereomicroscope and all metazoan zooplankton "swimmers" were removed from the sample. Material remaining on the 200-micron filters (i.e., sinking material) was then imaged with a macrophotography rig and subsequently rinsed back into the original sample tube (i.e., re-combined with the <200-micron sinking material). Samples were then separated and filtered onto different types of filters for a suite of different analyses including: particulate organic carbon flux, particulate nitrogen flux, carbon and nitrogen isotopes, chlorophyll a and phaeopigment flux, microscopy, genetic analyses, and 234Th flux.

>200-um filters for each sediment trap tube (used for removing mesozooplankton swimmers) was imaged using a Canon 5D mark II camera with attached 100-mm F/2.8 macro lens mounted in a downward-facing macrophotography rig. Images were manually analyzed using Image J to determine morphometric measurements for each large salp fecal pellet, which were then used to estimate biovolume. Carbon content of each fecal pellet was determined from a log-log relationship between pellet volume and pellet carbon mass. This relationship was determined from individual fecal pellets that were collected at sea, imaged to determine biovolume, and analyzed for carbon and nitrogen content on an isotope ratio mass spectrometer. Please note that these pellet flux measurements should be considered a conservative estimate of total salp fecal pellet mass flux as they only include intact pellets that could be identified from the images take of the filters.

BCO-DMO Processing:
- converted latitude values from degrees South to degrees North;
- rounded lat and lon to 5 decimal places;
- added UTC date/time fields in ISO8601 format;
- renamed fields.

NSF Award Abstract:
Salps are unique open-ocean animals that range in size from a few millimeters to greater than twenty centimeters, have a gelatinous (jelly-like) body, and can form long chains of many connected individuals. These oceanic organisms act as oceanic vacuum cleaners, having incredibly high feeding rates on phytoplankton and, unusual for consumers of their size, smaller bacteria-sized prey. This rapid feeding and the salps' tendency to form dense blooms, allows them move substantial amounts of prey carbon from the surface into the deep ocean, leading to carbon dioxide removal from the atmosphere. However, salps are often considered a trophic dead-end, rather than a link, in the food web due to the assumption that they themselves are not consumed, since their gelatinous bodies are less nutritious than co-occurring crustacean prey. Along with this, salp populations are hypothesized to be increasing due to climate change. This proposal addresses these questions: 1) Do salps compete primarily with crustaceans (as in the prevailing paradigm) or are they competitors of single-celled protists, which are the dominant grazers of small phytoplankton? 2) Do salp blooms increase the efficiency of food-web pathways from tiny phytoplankton to fisheries production in nutrient-poor ocean regions?

This project will support the interdisciplinary education of a graduate student who will learn modeling and laboratory techniques in the fields of biological and chemical oceanography and stimulate international collaborations between scientists in the United States and New Zealand. Additionally, several Education and Outreach initiatives are planned, including development of a week-long immersive high school class in biological oceanography, and education modules that will serve the "scientists-in-the schools" program in Tallahassee, FL.

It is commonly assumed that salps are a trophic sink. However, this idea was developed before the discovery that protists (rather than crustaceans) are the dominant grazers in the open ocean and was biased by the difficulty of recognizing gelatinous salps in fish guts. More recent studies show that salps are found in guts of a diverse group of fish and seabirds and are a readily available prey source when crustacean abundance is low. This proposal seeks to quantify food web flows through contrasting salp-dominated and salp-absent water parcels near the Chatham Rise off western New Zealand where salp blooms are a predictable phenomenon. The proposal will leverage previously obtained data on salp abundance, bulk grazing impact, and biogeochemical significance during Lagrangian experiments conducted by New Zealand-based collaborators. The proposal will determine 1) taxon- and size-specific phytoplankton growth rate measurements, 2) taxon- and size-specific protozoan and salp grazing rate measurements, 3) compound specific isotopic analysis of the amino acids of mesozooplankton to quantify the trophic position of salps, hyperiid amphipods, and other crustaceans, 4) sediment traps to quantify zooplankton carcass sinking rates, and 5) linear inverse ecosystem modeling syntheses. Secondary production and trophic flows from this well-constrained ecosystem model will be compared to crustacean-dominated and microbial loop-dominated ecosystems in similarly characterized regions (California Current, Costa Rica Dome, and Gulf of Mexico).

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.