The dataset contains the processed bottle files, i.e., depths and associated data collected electronically by the CTD, for all CTD casts during cruises KM1919 and KM1920, along with all nutrient data on casts from which it was collected. The nutrients include nitrate, nitrite, silicate, phosphate, and ammonium. The concentrations for all nutrients are in micromoles per kg as is the CTD oxygen concentration. These two cruises took place on the R/V Kilo Moana from September to October 2019 in the Eastern Tropical North Pacific, off the coast of Mexico and Southern California. The data were collected as part of NSF grant numbers 1542240 to Gabrielle Rocap, Rick Keil, Allan Devol, and Curtis Deutsch along with NSF-1657958 to Allan Devol.

Table of Contents

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

Data were collected CTD during cruises KM1919 and KM1920.

The CTD data has been reprocessed and aligned, and outliers have been removed. Nutrient samples were filtered (Sterivex 0.22um) before analysis and analyzed using the US-JGOFS protocols (http://usjgofs.whoi.edu/protocols_rpt_19.html). All data are considered preliminary.

Known Problems:
Calibration salinity samples analyzed using an AutoSal salinometer agreed with CTD sensor 0, but sensor 1 was significantly off. Consequently, salinity values and derived values (density, oxygen, oxygen saturation) were calculated only from sensor 0. Sensor 1 data not included.

Data Processing:
Raw data from the CTD was processed using SeaBird software programs (Data conversion, Align, Thermal mass, Derive, Bin average and Bottle Summary).

BCO-DMO Processing:
- converted dates from Excel format to YYYY-MM-DD;
- renamed fields to comply with BCO-DMO naming conventions;
- added Cruise_ID field based on date;
- corrected date for station 8, second occupation.

Coverage: Eastern Tropical North Pacific

Extracted from the NSF award abstract:

Marine oxygen deficient zones (ODZs) are waters that are functionally devoid of oxygen. Without oxygen, some microbes are capable of converting nitrogen in the water into N2 gas, which then leaves the ocean and enters the atmosphere. This loss of an important nutrient from the ocean has impacts on phytoplankton growth and marine food webs. While oxygen deficient zones occupy a very small percentage of the ocean, they account for as much as half of the oceanic loss of N as N2. Moreover, the size of these regions is predicted to expand during this century due to climate change. The microbes that are capable of producing N2 gas are extremely diverse, and use several different biochemical pathways to carry out this process. They may occur both free-floating in the water and attached to small particles that are suspended or sinking from the surface waters and providing them a carbon source. However the importance of these two lifestyles (free-living vs particle attached) in terms of contributions to N loss from the oceans is not well understood. This project will identify the major organisms that result in N2 gas production on both suspended and sinking particles, the chemical reactions they carry out, and the rates at which this occurs. This information will be used to improve global climate models to better predict rates of N loss in a future ocean. Elementary and middle school teachers enrolled in a Masters in Science for Science Teachers program will be involved in the project and the graduate students and post-doctoral researchers supported by the project will have opportunities to participate in their classrooms. Underserved populations will also be integrated into the research at the undergraduate and middle school level through a series of summer internships.

ODZs have very complex elemental cycles, implying great microbial diversity. Intertwined with the microbial complexity of ODZ regions is the relatively unexplored interplay between free-living bacteria and those living on either suspended or sinking particles. Determining how these communities and niches interact and relate is one of the most challenging components of ODZ system studies today. Current climate models portray the dynamics of particles in the ODZs and throughout the deep ocean through prescribed functions based on sparse data from the oxic ocean with microbes represented only by the net chemical reactions of the community. However, in reality a phylogenetically and metabolically diverse group of microbes, likely acting in consortia, are responsible for the nitrogen transformations that ultimately result in the production of N2. To explore the processes maintaining the genetic diversity and functional redundancy in N loss processes, four research areas will be integrated: the community phylogenetic diversity (both taxonomic and genomic diversity) the genetic diversity of the proteins that carry out key N transformation processes (as seen through quantitative proteomics), the resulting biogeochemical functions (15N labeled nitrogen transformation rate measurements) and predictions about how this diversity and corresponding function may change in response to climate change (biogeochemical modeling). The approach will be to assay both phylogenetic (16S rRNA tag sequencing) and functional genetic diversity (genomics) on sinking particles collected using large-volume sediment traps. Phylogenetic and genomic studies will be intimately tied to measurements of activity - who is doing key biogeochemical transformations (proteomics) and what are the in situ rates at which they are doing them (using novel incubation systems). Data will then be used to model how diversity and corresponding function change on a range of time and space scales, from the sinking of a single particle to seasonal cycles. To understand the relationship of community diversity and function on suspended and sinking particles, a series of three cruises will be conducted in the Eastern Tropical North Pacific ODZ.

Coverage: Eastern tropical North Pacific 21N-12N: 130W-105W

NSF abstract:

Oxygen Deficient Zones (ODZs) are regions in the global ocean where concentrations of dissolved oxygen in seawater are very low. Low oxygen concentrations affect rates of denitrification, a microbial process in which nitrate is converted to nitrogen gas. This can lead to significant losses of nitrate from the ocean. Nitrate is an important nutrient in the ocean that supports ocean ecosystems. Ocean warming is likely to expand these ODZs making it imperative we understand the role of the ODZs on the chemistry and biology of these regions. This understanding requires repeated sampling of nutrient and oxygen concentrations through time. The investigator plans to utilize available ship time from an existing grant to sample the Eastern Tropical North Pacific (ETNP) ODZ six times over a two year period during the spring, summer, and winter months. The aim is to determine the permanence and seasonality of the recent expansion of the ODZ in the ETNP, as well as identify the processes responsible for any observed changes. This research will support the University of Washington's Masters in Science for Science Teachers program, which provides a link between researchers, graduate students, and elementary aged youth, and there will be funds provided for two undergraduate students to participate in two research cruises on the R/V Thompson.

This project seeks to answer whether observed increased rates of denitrification in the ODZ of the ETNP are solely due to a growing oxygen deficiency problem or can be attributed to sample timing and seasonality. Additionally, the increased loss of nitrate will be investigated to conclude whether it really is due to increased rates of denitrification in the ODZ or some other cause. Climate model simulations predict a large perturbation to the dissolved oxygen content of the ocean, which could have further consequences than purely oxygen chemistry. This study hopes to answer the question of how climate change impacts on dissolved oxygen will affect denitrification in the ocean, which in turn has a much larger effect on limiting marine productivity.

Website: http://www.nsf.gov/funding/pgm_summ.jsp?pims_id=503446

Coverage: global

(adapted from the NSF Synopsis of Program)
Dimensions of Biodiversity is a program solicitation from the NSF Directorate for Biological Sciences. FY 2010 was year one of the program.  [MORE from NSF]

The NSF Dimensions of Biodiversity program seeks to characterize biodiversity on Earth by using integrative, innovative approaches to fill rapidly the most substantial gaps in our understanding. The program will take a broad view of biodiversity, and in its initial phase will focus on the integration of genetic, taxonomic, and functional dimensions of biodiversity. Project investigators are encouraged to integrate these three dimensions to understand the interactions and feedbacks among them. While this focus complements several core NSF programs, it differs by requiring that multiple dimensions of biodiversity be addressed simultaneously, to understand the roles of biodiversity in critical ecological and evolutionary processes.