MEPS 534:65-78 (2015)  -  DOI: https://doi.org/10.3354/meps11404

ABSTRACT: Given the significance of planktonic copepods to marine food webs and biogeochemical cycles, information about their broad-scale community structure can enhance our understanding of the global marine ecosystem. We performed a metagenetic analysis of nuclear large subunit ribosomal DNA to determine spatial patterns in the community structure of epipelagic copepods in the tropical and subtropical Pacific. The metagenetic method was taxonomically comprehensive, avoided time-consuming morphological classification, and successfully characterized copepod communities at 19 stations in Kuroshio, the North Pacific subtropical gyre (NPSG), the eastern tropical Pacific, and the South Pacific subtropical gyre (SPSG). A total of 404 molecular operational taxonomic units (MOTUs) were obtained from 434304 quality-filtered sequence reads with a 97% similarity threshold. Using community analyses of sequence reads and MOTU compositions, we identified a distinct copepod community shoreward of the Kuroshio Current. The MOTU compositions were similar between the oceanic side of Kuroshio and the subtropical gyres; however, on the basis of sequence reads, the copepod communities were clustered in 2 groups, equator-Kuroshio and subtropical gyre. These groups were highly correlated with chl a concentrations, and primary productivity appeared to significantly determine the major distribution patterns of copepods in the tropical and subtropical Pacific. Multiple taxonomic groups co-existed in the oligotrophic subtropical gyres, where MOTU numbers and diversity indices were high, particularly in the NPSG. In addition to the large number of species with distribution peaks in the subtropical gyres, the relatively high productivity in the NPSG compared with the SPSG might favor some species with distribution peaks in the eastern tropical Pacific and Kuroshio regions, leading to the highest copepod diversity in the NPSG.

KEY WORDS: Copepoda · Metagenetics · Community structure · Diversity · Pacific Ocean