A Voyage Through the Arctic Post #6

Deploying bongo nets. Credit: Mabel Baldwin-Schaeffer/NOAA Fisheries.

On September 16th, we wrapped up the plankton sampling portion of the mission. However, the oceanographic work continues. My daily routine included actively documenting information at each sampling station. The scientific team collects information, meticulously recorded on a logger. It includes:

• gear type (net type and mesh size)
• tow performance (good/fail)
• purpose (surveying of plankton/physical environment)
• flowmeter revolutions (to estimate the volume of water filtered by the net)
• tow time
• samples collected (e.g., the labeled numbers for reference and analysis)

The oceanography team deploys the CTD (Conductivity, Temperature, and Depth) to collect water samples and monitor temperature at the same location while we looked at the phytoplankton and zooplankton. Measurements, include conductivity (a measure of the water's ability to conduct electricity), temperature, and depth, provide crucial information about the water column's physical and chemical properties. Additionally, samples are taken to estimate chlorophyll (a measure of the phytoplankton in the water), nutrients (helps with many things including understanding conditions to support phytoplankton), salinity, and oxygen, which are all vital for understanding the marine ecosystem.

Collecting water samples from a CTD bottle. Credit: Mabel Baldwin-Schaeffer/NOAA Fisheries.Yellow jar holds samples from large net and the pink jar holds samples from a small net. Credit: Mabel Baldwin-Schaeffer/NOAA Fisheries.

At each station, the plankton tow is performed 10 meters off the benthos (seafloor):

• The net design consists of two large and two small nets, each with a flowmeter at the center to measure the volume of water that has passed through during the tow.
  • Large net: 60-centimeter diameter; mesh size of 505 microns
  • Small net: 20-centimeter diameter; mesh size of 153 microns
• The net is deployed at predetermined locations using a winch off the vessel's starboard side. It is quickly lowered, assisted by an attached 50-kilogram weight, and brought back to the surface at a slower speed, taking approximately 6 to 8 minutes to complete the deployment and retrieval.
• Each net has a cod end attached to the end of the net that collects the plankton during the tow. Upon surfacing, the net is sprayed to wash all the organisms into the cod end. The next step is preservation-a process during which the sample is further screened using a sieve, a mesh strainer separating unwanted elements. Formaldehyde is then added to the samples to preserve them for later analyses.
• Samples from both the large and small nets are collected and preserved.
• A COD form is completed for every station and every haul.

The information is then entered into a computer software application. The software is designed to organize and manage the data, and it is then used to sync with other sample information. Once the data is entered, it is carefully reviewed for accuracy and completeness before being stored in a secure database for future reference and analysis.

Front of bongo net. Credit: Mabel Baldwin-Schaffer/NOAA Fisheries.Back of the bongo nets. Credit: Mabel-Baldwin-Schaeffer/NOAA Fisheries.One sample from cod end of a net. Credit: Mabel Baldwin-Schaeffer/NOAA Fisheries.Spraying the bongo net after a tow. Credit: Mabel Baldwin-Schaffer/NOAA Fisheries.Sieves of various sizes. Credit: Mabel Baldwin-Schaeffer/NOAA Fisheries.

Sample and mooring sites on this cruise are as old as 30, providing a valuable time series of measurements that scientists can use to monitor climate change and provide critical information to support fisheries management in Alaska.

This cruise has 69 stations spaced approximately 10 miles apart. This spacing allows scientists to cover a wide area comprehensively and understand things like the plankton distribution across the Bering Sea. Find a map of the working area with more information here.

Database information and plankton samples will be shipped to the National Marine Fisheries Research Institute in Szczecin, Poland, where experts at itsPlankton Sorting and Identification Centerwill process, identify, and count the types of plankton. Zooplankton are analyzed for lipid content and the presence of harmful algal bloom toxins. Experts also identify larval and juvenile fish from the nets using DNA analysis. The NOAA Science Centers have collaborated with the National Marine Fisheries Research Institute for 31 years.

Biological Oceanographer David Kimmel, who is leading the plankton team on this survey, emphasizes the critical role of plankton data. "Plankton data are critical to understanding the food web base," said Kimmel. "Zooplankton are prey items for larval and juvenile fish, seabirds, and marine mammals. The information we gather on this survey will be used to help understand the current status of the ecosystem and provide important information for ecosystem-based fisheries research. This includes Ecosystem Status Reports and Ecological and Socioeconomic Profiles for key fish species in Alaska. These reports are presented to the North Pacific Fishery Management Council each year."

Sample from cod end of a net. Credit: Mabel Baldwin-Schaeffer/NOAA Fisheries.David Kimmel capturing zooplankton images. Credit: Mabel Baldwin-Schaeffer/NOAA Fisheries.David Kimmel conducting a Rapid Zooplankton Assessment. Credit: Mabel Baldwin-Schaeffer/NOAA Fisheries.

Please also visit our Facebook Live Event, Focusing On the Base of the Food Web, where EcoFOCI scientists will take you on a virtual tour of their Ichthyoplankton (larval fish) Laboratory.

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