Table of Contents

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

Zooplankton samples were collected on NGA-LTER cruises along the Seward Line and within PWS during the summer, spring, and fall of 2018-20 aboard the R/V Sikuliaq, R/V Tiglax or the R/V Woldstad. During spring and summer cruises copepods were collected using a Quad net, a modified CalVet net (0.25 m mouth diameter, 1 m cylinder and 1.5 m cone), of 150-µm mesh hauled vertically from 100 m during the day, then live sorted and imaged. During summer 2019, animals were also collected during the night in the drogue net (0-200 m) of a towed Midi Multinet (0.25 m²) (Hydro-Bios, Germany), equipped with 500-µm mesh nets, and live sorted and imaged the following morning. The towed Multinet fished five discrete depth layers including: 0-20, 20-40, 40-60, 60-100, and 100-200 m. During summer 2020, we employed a vertically-hauled Midi Multinet of 150-µm mesh (fished during the day) for these same strata that were live-sorted and imaged immediately after collection to improve specimen quality. During summer and fall of all years at one or two deep-water Seward Line stations, and one or two PWS stations, we also fished the vertically-hauled Multinet at four additional depths: 200-300, 300-400, 400-600 and 600-1200 m (or 600-720 for PWS). A flowmeter installed in each net quantified the volume of water filtered. We targeted Neocalanus flemingeri, Neocalanus plumchrus and Neocalanus cristatus for sorting, staging, and imaging from each of these strata.

Up to 60 individuals of each stage for each species were analyzed, if present. The Neocalanus specimens were selected individually from homogenized temperature-regulated subsamples using a ladle or wide-bore plastic pipette. Only living, apparently undamaged individuals with intact lipid sacs were sorted and imaged using a Leica MZ16 microscope with either a Spot 4Mpx, Jenoptik 8Mpx, or Spot 12Mpx digital camera. Depending on stage and species, just prior to imaging three to fifteen animals were placed in a chilled embryo dish then water was reduced so animals shifted onto their sides (with gentle manipulation as needed). For every magnification setting, a calibration scale bar was added to the images. In cases where availability of animals was limited, animals with compromised lipid sacs were imaged to establish prosome length only. The calibrated images were later analyzed using Spot Software (V4.7 or 5.3) for determination of the prosome length (measured as maximum) and prosome width (measured from top of prosome to base of maxillipeds), the lipid sac length (measured from most anterior point to most posterior point), and lipid sac width (measured starting at the point closest to the base of the maxillipeds (ventral point) to most dorsal point). Animals that showed signs of compromised lipid sacs upon image inspection were only measured for prosome length. Adobe Photoshop (version CS6) was utilized to measure lipid sac area using the quick select tool to help demarcate the perimeter of the lipid sac. The number of pixels within the perimeter of the lipid sac was converted to area (mm²) using the pixel-to-µm calibration associated with each image.

To calculate lipid sac volume, we first assumed the lipid sac to be a cylinder. We used the measured lipid sac length and the measured lipid sac area to find the average diameter of the cylinder (i.e. area divided by length) in order to account for the varying height and shape of the lipid sac. We then used this average diameter to estimate the volume of the lipid sac.  Body volume wa calcualted at a oblate spheroid from prosome length and prosome height.

Species List:

Scientfic_Name, Lifesciences Identifier (LSID)
Neocalanus flemingeri, urn:lsid:marinespecies.org:taxname:353708
Neocalanus plumchrus, urn:lsid:marinespecies.org:taxname:196772
Neocalanus cristatus, urn:lsid:marinespecies.org:taxname:104470

BCO-DMO Data Manager Processing Notes:
* Data from source file lipid.data.final 2024.csv were imported into the BCO-DMO data system. csv downloads of these data will have the name "936158_v1_neocalanus-lipids-and-morphometrics.csv."
* Parameters (column names) renamed to comply with BCO-DMO naming conventions. See https://www.bco-dmo.org/page/bco-dmo-data-processing-conventions

* ISO_DateTime_UTC column added. Converted from DateTime (Alaska local time AKST/AKDT in excel numeric format) to human readable date in ISO 8601 format timestamp with timezone (UTC as Z).

* decimals in columns (LipidArea, AdjustedHeight, LipidVolume, BodyVolume, Lipid_percent_BodyVolume) greater than 4 decimal places were rounded to 4 decimal places.

* Missing data in the BCO-DMO system displays as a blank (null values) by default and will vary depending upon the file format downloaded (blank in csv files, NaN in .mat matlab files, etc).

NSF Award Abstract:
The sub-arctic Pacific sustains major fisheries with nearly all commercially important species depending either directly or indirectly on lipid-rich copepods (Neocalanus flemingeri, Neocalanus plumchrus, Neocalanus cristatus and Calanus marshallae). In turn, these species depend on a short-lived spring algal bloom for growth and the accumulation of lipid stores in order to complete an annual life cycle that includes a period of dormancy. The intellectual thrust of this project measures how the timing and magnitude of algal blooms affect preparation for dormancy using a combination of field and experimental observations. The Northern Gulf of Alaska - with four calanid species that experience dormancy, steep environmental gradients, well-described phytoplankton bloom dynamics, and a concurrent NSF-LTER program - provides an unusual opportunity to identify the factors that affect dormancy preparation. Education and outreach plans are integrated with the research. Educational efforts focus on interdisciplinary opportunities for undergraduate, graduate and post-doctoral trainees. The project will generate content for existing graduate and undergraduate courses. U. of Alaska Fairbanks and U. Hawaii at Manoa are Alaska Native and Native Hawaiian Serving Institutions, and students from these groups will be recruited to participate in the project. Because fishing is a major industry in the Gulf of Alaska, outreach will communicate the role copepods play in marine ecosystems using the concept of a dynamic food web tied to production cycles.

Diapause (dormancy) and the accompanying accumulation of lipids in copepods have been identified as key drivers in high latitude ecosystems that support economically important fisheries, including those of the Gulf of Alaska. While the disappearance of lipid-rich copepods has been linked to severe declines in fish stocks, little is known about the environmental conditions that are required for the successful completion of the copepod's life cycle. A physiological profiling approach that measures relative gene expression will be used to test two alternative hypotheses: the lipid accumulation window hypothesis, which holds that individuals enter diapause only after they have accumulated sufficient lipid stores, and the developmental program hypothesis, which holds that once the diapause program is activated, progression occurs independent of lipid accumulation. The specific objectives are: 1) determine the effect of food levels during N. flemingeri copepodite stages on progression towards diapause using multiple physiological and developmental markers; 2) characterize the seasonal changes in the physiological profile of N. flemingeri across environmental gradients and across years; 3) compare physiological profiles across co-occurring calanid species (N. flemingeri, Neocalanus plumchrus, Neocalanus cristatus and Calanus marshallae); and 4) estimate the reproductive potential of the overwintering populations of N. flemingeri. The broader scientific significance includes the acquisition of new genomic data and molecular resources that will be made publicly available through established data repositories, and the development of new tools for routinely obtaining physiological profiles of copepods.

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.

NOTE: Petra Lenz is a former Principal Investigator (PI) and Andrew Christie is a former Co-Principal Investigator (Co-PI) on this project (award #1756767). Daniel Hartline is the PI listed for the award #1756767 and is now a former Co-PI on this project.