Vol. 52, 2013

TOccurrence characteristics of two sibling species, Pseudodiaptomus inopinus and Pseudodiaptomus poplesia (Copepoda, Calanoida, Pseudodiaptomidae), in the Mankyung River estuary, South Korea

Eun-Ok Park^1,2*, Jeffery R Cordell³ and Ho Young Soh⁴

¹Department of Oceanography, Chonnam National University, Gwangju 500-757, South Korea
²Department of Life Science, Hanyang University, Seoul 133-791, South Korea
³School of Aquatic and Fishery Sciences, University of Washington, Box 355020, Seattle, WA 98195-5020, USA
⁴Faculty of Marine Technology, Chonnam National University, Yeosu 550-749, South Korea

Abstract
Background: Abundances of two closely related Pseudodiaptomus species, Pseudodiaptomus inopinus and Pseudodiaptomus poplesia, and salinity, temperature, and chlorophyll (Chl) a levels were measured monthly at a station in the Mankyung River estuary, South Korea, through a spring tide flood-ebb series.
Results: Both species occurred mostly under mesohaline to polyhaline conditions throughout the year. P. poplesia was abundant under winter polyhaline conditions and reached its peak abundance under mesohaline conditions in spring, when the Chl a concentration was highest. P. inopinus had lower densities than P. poplesia at all salinities in spring and had peak densities under mesohaline and polyhaline conditions in November, when a second Chl a peak concentration occurred. Egg-bearing females of both P. poplesia and P. inopinus were present in spring and fall, but the ratio of gravid females of the former was higher under mesohaline and polyhaline conditions in April and May, while that of the latter was higher under polyhaline conditions in March.
Conclusions: These facts indicate that abundances of P. poplesia and P. inopinus may be controlled by Chl a concentrations and salinity conditions.

Key words: River estuary; Copepods; Salinity gradient; Chlorophyll a concentration; Co-occurrence.

*Correspondence: E-mail: ej0731@daum.net