Dataset: Benthic microalgal photopigment concentrations from nearshore shelf waters off Charleston, SC from June 2018 to August 2021

Samples for Benthic microalgal photopigment analysis were collected by SCUBA divers from the R/V Trinity in nearshore waters of Charleston, SC using 1 square centimeter x 10 centimeter (cm) plastic core tubes gently pushed into the sediment to minimize disruption of the surface layers. Tubes were capped and carefully removed from the sediment. Ten cores were obtained randomly within a 1 square meter area at select locations for each sample date. The upper 1 centimeter of the core was extruded, frozen at -80 degrees Celsius, and analyzed within 30 days after collection. Sediments were dried and sieved for grain size analysis.

High-performance liquid chromatography (HPLC) was used to determine chemosystematic photosynthetic pigments. Samples were lyophilized for 24 hours at -50 degrees Celsius, placed in 90 percent acetone (1 milliliter), sonicated on ice for 30 seconds, and extracted at -20 degrees Celsius for 18 to 20 hours. Filtered extracts: 0.45 micrometers, 250 microliters were injected into a Shimadzu 10AD HPLC equipped with a monomeric (Rainin Microsorb-MV, 0.46 x 10 centimeters, 3 micrometers) and a polymeric (Vydac 201TP54, 0.46 x 25 centimeters, 5 micrometers) reverse-phase C18 column in series. A nonlinear binary gradient of 80 percent methanol: 20 percent 0.50 M ammonium acetate and 80 percent methanol:20 percent acetone was the mobile phase (Pinckney et al. 1996, 2001). Absorption spectra and chromatograms (440 ± 4 nanometers) were acquired using a Shimadzu SPD-M10av photodiode array detector. Pigment peaks were identified by comparison of retention times and absorption spectra with pure carotenal and chlorophyll standards (DHI, Denmark). The synthetic carotenoid β-apo-8'-carotenal (Sigma) was used as an internal standard.