Table of Contents

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

Sample collection and sorting

Copepods were collected in Prince William Sound, Alaska in the summer and fall of 2019 during the Northern Gulf of Alaska Long Term Ecological Research (NGA LTER) cruises (https://nga.lternet.edu/). Females “PWS2/June” were collected on June 30th, 2019 at the sampling site PWS2 (Latitude 60° 32.1’N; Longitude 147° 48.2’W) (R/V Sikuliaq, cruise number: SKQ201915S), and the “Pleiades/September” females were collected on September 12th  and 13th, 2019 at PWS2 and near the Pleiades Islands (Latitude 60° 16.7’N; Longitude 147° 59.2’W) (M/V Tiglax, cruise number: TGX201909). Copepods were collected with a Midi MultiNet (0.25 m2 mouth area; 150 μm mesh nets) towed vertically from near the bottom to the 163 surface at 0.5 m/sec (PWS2: 798 m; KIP2: 588 m). Upon retrieval, net samples were immediately diluted using filtered seawater collected from depth and kept between 4-6°C to minimize thermal stress. All females selected for the experiments were sorted under a dissecting microscope. Females were placed in groups of three into 750 mL Falcon tissue-culture flasks and incubated under dim light in an incubator for up to 4.5 weeks. Experimental emperatures were at or below deep-water temperatures in Prince William Sound (temperature settings: 4°C for June and 6°C for September). A subset of females was used in the DNA replication experiments; the remaining females were imaged for measurements of prosome length and lipid sac area (see related dataset  https://www.bco-dmo.org/dataset/908514).

Experimental design

For the timeline, sets of females were removed from the incubation flasks for imaging and/or incubations in low concentrations of 5-Ethynyl-2’-deoxyuridine (EdU). Individuals that were imaged as well as incubated in EdU are identified in the dataset and provide identifications used in the related dataset.  

Lipid sac and prosome length imaging 

A total of 204 females were imaged for body measurements, with 31 of these females being also part of EdU experiments. Live females were placed in a chilled embryo dish with a small drop of seawater. Females were imaged laterally at 32x magnification using a Leica MZ16 microscope equipped with a 12 MPx Spot Insight camera. Using ImageJ light images were analyzed manually for three measurements: prosome length in mm, area of the lipid sac in mm2, and area of the prosome in mm2. Prosome length was measured by placing a line from the anterior to posterior tip of the prosome, measurements were rounded to the nearest 0.1 mm. Lipid sac and prosome area were measured by outlining their perimeters. Total lipid content in milligrams (mg) was estimated using the area of the lipid sac (equation: TL=0.197A1.38, where A is the lipid sac area and TL is total lipid). This relationship was established by comparing lateral images of the lipid sac to gas-chromatographic lipid measurements of three Calanus spp. that generated an equation that used lipid sac area as a proxy for lipid content. Measured areas of the lipid sac and prosome were also used to compute a lipid fullness percentage (lipid sac area/prosome sac area × 100).

A supplemental file with information such as LSID from the WoRMS taxonomy site is included for the collected species Neocalanus flemingeri.

Add Latitude and Longitude columns with values from the “Methods and Sampling” section of the dataset page. Convert lat and lon to decimal degrees with 4 digit precision.

PWS2 lat 60.535 and lon -147.8033
Pleiades Lat 60.2783 and lon -147.9867

Rename column headers by replacing spaces with underscores and removing ? and () characters.

Remove units from column headers since the units will be noted in the parameters section on the dataset page.

Capitalize the first letter of each full month name in the Collection_month column.

Reformat dates from %m/%d/%Y to %Y-%m-%d

Rearrange the columns so that the Station, Latitude, Longitude, Date_collected and Collection_month columns come before experiment data.

The next columns give information about EdU incubation.

And the remaining columns give information about the imaging measurements.

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.