Seasonal and interannual variability in phytoplankton primary to copepod secondary and tertiary production for 18 years (2006–2023) in Sagami Bay, Japan
Year: 2025
Type: article
Abstract: Seasonal and interannual variations in phytoplankton primary production (PP) and in abundance, biomass, daily production rate (DPR) and food requirement of planktonic copepods (>200 µm) were investigated in the neritic area of Sagami Bay, Kanagawa, Japan, on 426 occasions from January 2006 to December 2023. Monthly/annual mean PP was 0.39–1.81 g C m−2 d−1. Copepod abundance, biomass and DPR revealed distinct seasonal variations, declining in May and remaining low in June–September, related to abiotic/biotic variables. These copepod parameters showed different interannual variations, related to anomalies of abiotic variables and climatic indices. Monthly/annual means of abundance, biomass and DPR of total copepods were 5.70×102–3.17×103 ind. m−3, 3.61–11.83 mg C m−3 and 0.38–1.28 mg C m−3 d−1, while those of depth-integrated copepod secondary (SP) and tertiary production (TP) were 0.018–0.060 and 0.003–0.012 g C m−2 d−1, respectively. Monthly/annual mean transfer efficiency of PP–SP, PP–TP and SP–TP was 1.0–9.9%, 0.2–1.6% and 8.5–22.9%, respectively. Transfer efficiencies of PP–SP and PP–TP decreased exponentially with PP, and these correlations were statistically significant. Monthly/annual mean food requirement by copepod secondary and tertiary producers was estimated to be 0.064–0.216 and 0.009–0.041 g C m−2 d−1, corresponding to 3.5–34.0% and 0.6–5.3% of PP, respectively. Estimation methods for DPR calculated by several empirical growth models were discussed, based on gross growth efficiency (i.e. the ratio of DPR to food requirement).
Source: Plankton and Benthos Research
Author: Koichi Ara
Institution: Nihon University
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: diamond
OpenAlex ID: W7081927590