Dataset: Chlorophyll a and flow cytometry data from bi-weekly vertical profiles in Resurrection Bay, AK from January to March of 2023 from bi-weekly vertical profiles in Resurrection Bay, AK from January to March of 2023

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).