Table of Contents

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

Samples were collected in Resurrection Bay within the inner basin at RES2.5 (60° 1.5’ N, 149° 21.5’ W; 298 m deep) at approximately biweekly intervals aboard the R/V Nanuq between January 5th and March 24th, 2023. Collection and sample processing are described in detail in Block (2024). Water was collected at discrete depths (surface, 10, 20, 30, 40, 50, 150, and 280 m) using 4-L Niskin Bottles. Two casts were required to collect all water samples, since only six Niskin bottles were mounted on an SBE55 rosette. Water samples were stored in dark Nalgene bottles in a cooler.

Chlorophyll α samples were size fractionated to estimate the chlorophyll α contribution of pico- and nano-phytoplankton (< 20 µm size fraction) and larger phytoplankton (including diatoms plus larger photosynthetic dinoflagellates) (> 20 µm size fraction) at 10-m intervals from the surface to 50 m for each sample time point. Polycarbonate (47-mm diameter, 20-μm pore size) and glass fiber (25-mm diameter, 0.7-μm pore size) filters were used to size fractionate 250 mL samples using a serial filtration vacuum manifold system (Strom et al., 2016). Filters were extracted in 90% acetone for 24 hours in the dark at -20°C. Fluorescence was measured using a Turner 10-AU fluorometer using the acidification method (Strom et al., 2016). Fluorescence measurements were converted to estimated chlorophyll α concentrations (µg/L) (Lorenzen, 1966). Integrated chlorophyll α (mg/m2) was calculated using trapezoidal integration (Strom et al., 2016).

Synechococcus, photosynthetic picoeukaryotes, and heterotrophic bacterial abundances were measured using flow cytometry at 8 depths (surface, 10, 20, 30, 40, 50, 150, and 280 m). Samples (1 ml) from each depth were preserved with paraformaldehyde to a final concentration of 0.5%, frozen initially at -40°C, and later transferred to -80°C until batch analysis. Samples were thawed, stained with Hoechst 34580 (1 μg/mL final concentration), and analyzed with a Beckman Coulter CytoFLEX S flow cytometer (Selph, 2021). Data were processed using FlowJo software (version 10.8.2). Synechococcus and picoeukaryote abundances were converted to carbon biomass using cellular carbon content estimates appropriate for the region (200 and 1,490 fg C per cell, respectively) (Strom et al., 2016).

Flow cytometry data were processed using FlowJo software (version 10.8.2). Synechococcus and picoeukaryote abundances were converted to carbon biomass using cellular carbon content estimates appropriate for the region (200 and 1,490 fg C per cell, respectively) (O’Hara, 2023, Strom et al. 2016).

* Sheet 1 of submitted file "NaupProj2023_chla_flowc_BCODMO.csv
" was imported into the BCO-DMO data system for this dataset. Values "NA" imported as missing data values.   Table will appear as Data File: 954173_v1_chl-a-flow-cyto.csv (along with other download format options).

Missing Data Identifiers:
* In the BCO-DMO data system missing data identifiers are displayed according to the format of data you access. For example, in csv files it will be blank (null) values. In Matlab .mat files it will be NaN values. When viewing data online at BCO-DMO, the missing value will be shown as blank (null) values.

NSF Award Abstract
Global climate change and associated extreme weather events are increasingly impacting marine communities at all trophic levels and leading to shifts in the timing of life history events. This project is investigating the annual restart of the spring zooplankton community in the Gulf of Alaska in order to determine the timing of species-specific recruitment and growth. Zooplankton are small pelagic animals that are a critical link between microalgae and protozoans and higher levels in the food web including economically important fishes, birds and marine mammals. While their abundances and species composition have been documented over part of the annual cycle between late spring and fall, this project focuses on winter and early spring. The project integrates traditional methods with modern molecular approaches to characterize the diversity, development, feeding and physiology of zooplankton, especially the early developmental stages of copepods (small crustaceans). The goal is to determine which species are there, how many are present and where they are in the water column, and to reveal indicators of their health. Broader impacts include research training for three graduate students and at least four undergraduates in biological oceanography and physiological ecology. Outreach activities are focusing on broadening the public’s understanding of plankton ecology. An illustrated zooplankton guide for the Gulf of Alaska and plankton module for school teachers and students is being produced in collaboration with the Center for Alaskan Coastal Studies. Other plans include sponsorship of nature-drawing workshops on zooplankton and the production of an Art & Science traveling exhibit.

This project is tracking zooplankton population abundances, species composition and developmental stages through the spring restart in a high-latitude fjord in the northern Gulf of Alaska. While the entire zooplankton community is being characterized, the main focus is on the difficult-to-assess early developmental stages of copepods, which dominate the late spring biomass in the region. Three central hypotheses guide the research: 1) high abundances of copepod nauplii are present before any measurable increases in food in surface waters; 2) species diversity increases between winter and spring, with nauplii from large lipid-rich capital-breeding species appearing first, followed by those from income- and hybrid-strategy species and finally nauplii that emerge from dormant eggs; 3) prior to the appearance of food resources, nauplii from capital-breeding species conserve resources by delaying development and entering a state of dormancy in the second and third naupliar stages. The project entails intensive depth-stratified field sampling to characterize the wild community, in combination with laboratory experiments on nauplii to determine their responsiveness to food. The prey are being characterized by measuring chlorophyll a, dietary and prey community DNA sequencing and flow cytometry to establish diversity and abundances. Size-fractionated zooplankton samples are being analyzed using microscopy and community DNA sequencing to ascertain species diversity, developmental stage distribution and abundances. Feeding activity is being measured using dietary DNA sequencing of nauplii followed by comparisons with the prey field. Dormancy in nauplii is being determined by differential gene expression of target genes (RT-qPCR) and high-throughput sequencing of mRNA of individuals (transcriptomics) and community samples (meta-transcriptomics). Short-term and long-term effects of food availability on dormancy, development and growth are being quantified in laboratory experiments. Broader impacts are focused on training of students in interdisciplinary research and state-of-art techniques, and public outreach to introduce plankton ecology to broader audiences.