Seasonal and developmental variation in feeding by the copepod Calanus sinicus in the Yellow Sea

Abstract

We investigated feeding by Calanus sinicus in the Yellow Sea over four seasons in 2019–2022 using the gut pigment method. Studying the feeding of copepods is important for understanding processes within food webs, but little is known about the feeding ecology of C. sinicus, a major consumer of primary production in the Yellow Sea. The seasonal mean ingestion rate of C. sinicus was 16.6–42.1 for copepodite stage I (CI), 24.1–41.8 for CII, and 32.7–58.5 ng chl ind.−1 d−1 for CIII, with different seasonal fluctuations in each stage. The seasonal mean ingestion rate was 45.8–114.4 for CIV, 50.2–189.3 for CV, 96.9–438.9 for females, and 69.8–132.3 ng chl ind.−1 d−1 for males, with higher values in spring and lower values in summer. The combined grazing impacts of C. sinicus from the CI to adult stages were 1.66%, 1.43%, 2.04%, and 0.65% in spring, summer, autumn, and winter, respectively. The ingestion rate of later developmental stages from CIV to adults was positively related to chlorophyll-a concentration rather than water temperature or salinity, according to a redundancy analysis. These results suggest that C. sinicus population in the Yellow Sea actively feeds on phytoplankton in spring and that most of the grazing impact is attributed to females.