Table of Contents

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

The CTD methodology applies to all data associated with Lake Superior and August Lake Erie. All of the other Lake Erie data is covered by the Sonde methodology.

SeaBird Model 911 plus CTD profiler

At each site, the SeaBird Model 911 plus CTD profiler was moved over the site using the A-frame at the rear of the R/V Blue Heron. The profiler was then lowered into the water and allowed to collect the data on the way down to the bottom of the water column. This is based on the water depth at each site, which ranged from about 7m to over 160m. Once at the bottom of the water column, the profiler was then raised back through the water column. During this process, the profiler was stopped at select water depths based on the site. This was done so the onboard 8L Niskin bottles could be used to collect the water at the selected sites. For each site, several casts of the profiler were necessary to collect the desired amount of water. Despite this, representative casts from each site during each cruise were selected to avoid unnecessary confusion and cluttering of the files with redundant data. The profiler produced two different data sets, marked as ASC1 and ASC2, both of which are included as supplemental files. The ASC1 files are continuous readings from the CTD as it moved through the water column. The ASC2 files is the same data set, but has been binned into 1m increments. Data from the ASC2 files were converted to Excel format and included in the main dataset, as that matches the data collected with the Sonde.

Eureka Manta 2 Sonde

At each site, the Eureka Manta 2 Sonde was placed into the water off the side of the R/V Gibraltar III. The Sonde was slowly lowered through the water column and was stopped every meter. At each meter increment the data readout from the Sonde was recorded into a notebook. The Sonde was lowered through the entire water column, but was only used to record water conditions on the way down through the water column. There are no associated raw files for this data, as the data was recorded directly from a real-time readout.

2021 Cruises

May 12-13:          Superior cruise R/V Blue Heron (BH21-02)
July 12-14:           Erie cruise R/V Gibraltar III
Aug 8-15:             Superior cruise R/V Blue Heron (BH21-09)
Aug 24-28:           Erie cruise R/V Blue Heron (BH21-10)
Oct 11-13:            Erie cruise R/V Gibraltar III
Oct 18-20:            Superior cruise R/V Blue Heron (BH21-20)

2022 Cruises

May 25-27:          Superior cruise R/V Blue Heron (BH22-05)
May 31-June 2:   Erie cruise R/V Gibraltar III
July 5-7:               Erie cruise R/V Gibraltar III
July 12-14:           Superior cruise R/V Blue Heron (BH22-11)
Aug 14-16:           Lake Superior cruise R/V Blue Heron (BH22-15)
Aug 20-24:           Lake Erie cruise R/V Blue Heron (BH22-15)
Oct 3-5:                Erie cruise R/V Gibraltar III
Oct 10-12:            Superior cruise R/V Blue Heron (BH22-26)

2023 Cruises

May 23-25:         Superior cruise R/V Blue Heron (BH23-04)
May 31-June1:    Erie cruise R/V Gibraltar III
July 6-9:               Superior cruise R/V Blue Heron (BH23-07)
July 12-13:          Erie cruise R/V Gibraltar III
Aug 15-17:          Superior cruise R/V Blue Heron (BH23-10)
Aug 21-25:          Erie cruise R/V Blue Heron (BH23-10)
Oct 10-13:           Superior cruise R/V Blue Heron (BH23-21)

2024 Cruises

May 1-16:           Erie cruise R/V Gibraltar III

In exporting the raw data, the 1m binned data from the SeaBird Model 911 plus CTD profiler was used, but it was not processed beyond converting the ASC2.asc files into usable Excel formatting.

- Imported "CyanosNSF Great Lakes Master Spreadsheet.xlsx", sheet 1 into the BCO-DMO system
- Renamed parameter names to comply with BCO-DMO guidelines, removing special characters and units
- Combined year and month into Year_Month in ISO 8601 format
- Combined Year_Month and day into Date in ISO 8601 format
- Combined Date and time into ISO_DateTime_UTC in ISO 8601 format
- Remove extra temporal fields
- Replaced comma with period on row 1387 of Chlorophyll_a_RFU
- Exported file as "967649_v1_ctd_sonde_great_lakes.csv"

NSF Award Abstract:
The Great Lakes hold about 20% of the freshwater on Earth and have been increasingly impacted by human activities in recent decades. Lake Erie suffers from large, annually recurring, toxic cyanobacterial blooms in summer, whereas Lake Superior experiences smaller, localized cyanobacterial blooms after storm events. Cyanobacterial blooms have harmful ecological, human health, and economic implications. These blooms are a global phenomenon, observed in lakes and oceans, and can lead to low oxygen conditions and the production of toxins, both of which can be harmful for ecosystems. Understanding how different types of cyanobacteria influence nutrient cycling remains a major knowledge gap. This project aims to provide a deeper understanding of the long-term state of the Great Lakes ecosystem. The research approach combines new and established methods. Project results and implications will be shared with local and regional water interests in partnership with the Pittsburgh Collaboratory for Water Research, Education, and Outreach, the Great Lakes Commission Harmful Algal Blooms Collaborative, and the Lake Erie Area Research Network. Education is a central part of this project and training opportunities target next generation of scientists, including postdoctoral, graduate, and undergraduate students. The students and postdoc will receive state-of-the-art training in the rapidly developing fields of biogeochemistry and geomicrobiology, while working with an interdisciplinary team of scientists.

This study will examine nitrogen cycling, phytoplankton community composition, and the nitrogen isotopic composition of chloropigments in order to evaluate cyanobacterial productivity in the modern Laurentian Great Lakes as well as the historical record of cyanobacterial blooms over the past several hundred years. The nitrogen isotope composition of chloropigments is expected to provide a powerful new proxy for understanding primary productivity and the relative importance of cyanobacteria to export production and nitrogen cycling. This proxy would be valuable not only for management of modern systems but has important implications for increasing our understanding of the role of cyanobacteria throughout Earth history. This project would test this molecular isotopic proxy in contemporary aquatic ecosystems to assess its efficacy for: (1) determining the relative contributions of cyanobacteria vs eukaryotic algae (e.g., diatoms) to primary production; (2) evaluating export production of cyanobacterial productivity (including blooms); and (3) constraining historical cyanobacteria productivity in the sedimentary record. Comparison of a system characterized by eutrophication and seasonal cyanobacterial blooms (Lake Erie) with one characterized by picocyanobacteria productivity, but the near-absence of large-scale cyanobacterial blooms (Lake Superior), will provide information about the range of impacts that cyanobacteria can have on carbon and nitrogen cycling. Further information regarding nitrogen cycling will be derived from analysis of solid and dissolved nitrogen species throughout the annual cycle, as well as seasonal studies of sediment processes to measure associated sediment nitrogen removal rates through different processes.

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.