Copepod community from Arctic to Antarctic: large-scale patterns of naupliar and postnaupliar distribution and abundance in the epipelagic layer revealed by citizen science

The use of citizen science and opportunity sampling during commercial or tourist voyages can provide valuable insights into the structuring of the marine plankton community in broad biogeo-graphic areas. With the goal of studying the distribution and abundance of smaller zooplankton using citizen science approach, plankton samples were collected at 33 stations spanning from the Arctic to Antarctic during the cruise of the S/V "Croatian Tern" (1994-1997), using vertical tows with a 53 mu m mesh size Nansen net in the upper epipelagic layer. In this study, we summarize the observed distribution patterns of planktonic copepods by ontogenetic stages (nauplii, copepodites, adults) and by postnaupliar assemblages (calanoids, oithonids, oncaeids, harpacticoids, cory-caeids), reporting also on the numerical ratio of nauplii to postnaupliar copepods, as an important indicator of the stability of copepod reproduction. The highest abundances of total copepods were found in the northeastern and southeastern Pacific, while the lowest values were found in the Medi-terranean Sea and Southern Ocean. Overall, the copepod community was dominated by naupliar stages, while most postnaupliar assemblages (calanoids, oithonids, and oncaeids) were dominated by copepodites. Spatially, nauplii and postnaupliar oithonids showed similar latitudinal patterns, with both assemblages dominating in high latitudes of temperate zones on both sides of the equator, while contributions of calanoids, oncaeids, and corycaeids increased at lower latitudes. The ratio of nauplii to postnauplii varied from 1.1 to 6.4, and only at five stations was it slightly < 1. Lati-tudinally, the median values of this ratio varied from 1.1 in the marginal Arctic to 3.1 in the South Pacific, with no statistically significant differences among areas. The sudden change in nauplii/postnauplii ratio could signal disturbances in the copepod community, provided that the average values are determined for all marine areas under different productivity conditions.