Table of Contents

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

In May 2024, the R/V Sally Ride cruises SR2407 and SR2408 were conducted in the Gulf of California. The MOCNESS tow nets were deployed from May 4th to May 18th. MOCNESS sampling protocols included the standard vertical 0-1000 m day night pairs as well as unpaired shorter interval tows (ranging in depths focused on 450-200 m) to capture a more detailed vertical resolution. Finally, a subset of tows were conducted in a horizontal fashion where the net was maintained at a constant depth +/- 5 m to sample communities across midwater oxygen features.

After collection different samples were preserved in formalin for later Zooscan analysis, dried as five size fractionated biomass (200, 500, 1000, 2000, 5000) samples, or preserved in ethanol for metabarcoding analysis. 

Environmental data was processed by the LVpki software aboard ship.

- Loaded 13 MOCNESS .PRO files (MOC1_01A through MOC13_13A) in regex-csv format with whitespace delimiter, using filename as resource name
- Header row taken from row 1; rows beginning with "%" skipped; missing values defined as -9999.0000, -9999.00, and -99.0
- Captured metadata from skipped comment lines into columns: tow, Date, Temperature Probe, Pressure Probe, Tranmissometer, Conductivity Probe, Oxygen Probe, Fluorometer, Irradiance Probe, and Flow Meter Calibration; capture_skipped_rows_join set to false to preserve separate values per file
- Concatenated all 13 resources into single resource moc_all, mapping all fields by identical name; added file_name column from source filename
- Renamed fields: CTDDEPTH(M) to CTDDEPTH (removing unit suffix), spaces replaced with underscores in probe and calibration column names, file_name renamed to raw_data_filename
- Converted Date field from format %m/%d/%Y to %Y-%m-%d (date type)
- Split tow column using regex pattern capturing tow number, vessel name, and cruise ID into fields tow, vessel, and cruiseID
- Applied find/replace on vessel field: "Sally Ride" replaced with "R/V Sally Ride"
- Renamed resource moc_all to 996661_v1_mocness_files
- Converted time field (decimal day of year, year 2024) to ISO_DateTime_UTC in format %Y-%m-%dT%H:%M:%S (datetime type)
- Reordered fields placing vessel, cruiseID, tow, raw_data_filename, ISO_DateTime_UTC, lat, lon first, followed by measurement and instrument metadata fields
- Exported file as 996661_v1_mocness_files.csv

NSF Award Abstract:
This project is seeking to define physiologically-accessible habitat for animals faced with changing ocean conditions. Many oceanic animals migrate daily from warm, oxygenated surface waters at night to deep, cold and hypoxic waters during the daytime, and these migrations play critical roles in oceanic ecology and biogeochemical cycles. Over their depth ranges, migrators face very different ecological and environmental demands that may lead to unique traits that in turn, influence how they respond to a warming ocean where oxygen minimum zones are also expanding. This study is combining ecological and physiological approaches during two expeditions to the Gulf of California. The investigators are measuring metabolic traits in a diverse suite of ocean animals that exhibit vertical migration to determine possible roles of oxygen and temperature in triggering changes in vertical and latitudinal distribution. They are also measuring species distributions in relation to environmental oxygen and temperature to determine ecologically-relevant thresholds of environmental tolerance. The project involves training and experiential learning for graduate and undergraduate students. In addition, engagement with educational experts and artists will generate media and lesson plans to support STEM education and Next Generation Science Standards. These activities leverage the Bermuda Institute of Ocean Sciences’ Databytes and Mid-Atlantic Robotics IN Education (MARINE) programs, designed to improve ocean literacy and technological fluency and targeting students from groups traditionally underrepresented in science. Project products also include a new level for a video game that introduces the concepts of how oxygen minimum zones influence animal distribution.

Climate change is driving poleward shifts in the distributions of marine animals. These shifting edges of the range of species habitats are often interpreted as a manifestation of oxygen limitation that is presumed to occur at high water temperatures due to a mismatch between physiological oxygen supply and thermodynamically-driven oxygen demand. However, recent work by the investigators suggests that oxygen supply has evolved to meet demand regardless of temperature. These opposing views predict very different thermal thresholds for range expansion. In this study, the investigators are employing a relationship between metabolic traits to infer a unique temperature sensitivity in tropical diel vertical migrators and to map their metabolically-available habitat in the Eastern Pacific. Specifically, the investigators propose that oxygen supply does not limit metabolism in tropical migrators, even in the oxygen minimum zone. Instead, they contend that the active metabolic rate for tropical migrators is highly sensitive to temperature, and that this creates a barrier to range expansion where the aerobic scope for growth and reproduction is insufficient in cold waters. This temperature sensitivity will also allow migrators to expand poleward to newly available habitat following modest warming, rather than simply being extirpated from their native tropical habitat by excess warming. This hypothesis, if supported, would transform our mechanistic understanding of species’ responses to climate change, amend our predictions of range expansion, and modify our assessment of migrator contributions to oceanic biogeochemical cycles in a warmer future 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.