A multi-year investigation of the Temoridae (Copepoda, Calanoida) assemblage succession within the interplay waters of the northern South China Sea

Abstract

Abstract The South China Sea is the largest marginal sea in the world. The northern South China Sea has a complex hydrographic system affected by interplay waters of the Kuroshio Branch Current and the South China Sea waters. To understand the changes in the community structure of the planktonic calanoid copepod family Temoridae in relation to the interplay waters, we collected zooplankton samples in the northern South China Sea from surface waters (0 to 2 m) from November 2001 to January 2007 during 24 research cruises using a standard North Pacific zooplankton net (with a mesh size of 200 μm, a length of 1.8 m, and a mouth diameter of 0.45 m). Among a total of 253 samples, 5 species belonging to 3 genera of Temoridae were identified: Eurytemora pacifica Sato, 1913, Temora discaudata Giesbrecht, 1889, Temora stylifera (Dana, 1849), Temora turbinata (Dana, 1849), and Temoropia mayumbaensis Scott T., 1894. The 3 most abundant species were: T. turbinata (relative abundance, RA: 53.28%; mean density ± standard deviation, MD: 29.33 ± 89.53 ind. m−3), T. stylifera (RA: 36.02%, MD: 19.83 ± 145.22 ind. m−3), and T. discaudata (RA: 7.70%, MD: 4.24 ± 11.82 ind. m−3). The 3 most frequently occurring species were: T. turbinata (occurrence ratio, OR: 52.17%), T. discaudata (OR: 35.18%), and T. stylifera (OR: 9.88%). A noteworthy discovery in our samples was E. pacifica, a marine and brackish water species, collected from 3 stations located near the Kuroshio Branch Current in April 2003. This is the only month when this species was recorded during the investigation period. Variations of dominant species of Temoridae show a clear pattern of seasonal succession. The total abundance was significantly higher in the third quarter (September-November, 116.98 ± 314.49 ind. m−3) than in the fourth quarter (December-February, 24.26 ± 47.72 ind. m−3) (, one-way ANOVA). In general, the present results demonstrate that the assemblages of the Temoridae are very much structured by the water masses of the Kuroshio Current and the South China Sea.