| dc.description.abstract | Zooplankton play a critical role in carbon (C), nitrogen (N), and phosphorus (P) cycling in the ocean. There are fewer measurements of zooplankton C, N, and especially P, compared with phytoplankton and total particulate C:N:P. In this study, we measured the C:N:P in four size fractions (>2000 µm, 500-2000 µm, 250-500 µm, 64-250 µm) of zooplankton sampled using a WP-2 and ring-net from 18 stations in the North Pacific Subtropical Gyre (NPSG) and North Pacific Equatorial Countercurrent (NPEC) region. These regions cover a wide latitudinal range in temperature, nutrients, phytoplankton biomass and associated phytoplankton C:N:P. The overall median molar zooplankton C:N:P from the region is 116.4:25:1. Our data revealed significant differences in C:N:P across the four size fractions. The C:N was 2.1 (± 0.3) % higher in the 500-2000 µm size fraction compared to the overall median molar C:N, C:P was 18.5 (± 0.29) % higher in the 250-500 µm size fraction compared to the overall median molar C:P, and N:P was 15.2 (± 0.65) % higher in the 250-500 µm size fraction compared to the overall median molar N:P. The overall median zooplankton C, N, P content as a percent of dry weight from the region is 26 %, 8 %, 0.69 %. The N % dry weight was 24.1 (± 0.34) % lower in the >2000 µm size fraction compared to the overall median N % dry weight, and P % dry weight was 26.6 (± 0.37) % lower in the >2000 µm size fraction compared to the overall median P % dry weight, suggesting that gelatinous zooplankton may be a larger proportion of the mass in this size fraction. In addition, our low measurements of P as % dry weight in the >2000 µm are intermediate between P % dry weight measured from isolated gelatinous and euphausiid species from our samples. We did not observe strong changes in zooplankton C:N:P with latitude, temperature, nitrate concentration, or phytoplankton biomass (chlorophyll-a and carbon concentration) or C:N:P, however C:N in the >2000 µm and 500-2000 µm was correlated with C:N in phytoplankton. Overall, our results indicate that variability in zooplankton C:N:P is dominated by community composition, and not environmental conditions. If climate warming shifts the zooplankton community towards larger gelatinous zooplankton in the greater than 2000 µm fraction at the expense of smaller 250-2000 µm crustacean zooplankton, we may see shifts in the overall median molar C:N:P towards 125:26:1 in this region. | en_US |
