Ž . Journal of Marine Systems 28 2001 281–301 www.elsevier.nlrlocaterjmarsys Diel vertical distribution, and herbivory of copepods in the south-western part of the Black Sea Sengul Besiktepe ) Institute of Marine Sciences, Middle East Technical UniÕersity, P.O. Box 28, Erdemli 33731 Icel, Turkey Received 4 June 2000; accepted 24 January 2001 Abstract The abundance and population structure of copepods were studied in the southwestern part of the Black Sea in May 1994, April and September 1995, April, June and September 1996. Vertical distribution and diel vertical migration of copepods were studied in April and September 1995 and June 1996. In addition, the grazing rates of three size classes of copepods—300–500, 500–1000 and 1000–2000 mm—were estimated in September 1995. The total abundance of copepods was higher in June samples due to the large contribution of the warm water species, Paracalanus parÕus. Vertical distribution appeared to be related to season, species, stages of species and the oxygen concentration in the water column. Ž . Ž . Female, copepodite V CV and copepodite IV CIV stages of Calanus euxinus and female Pseudocalanus elongatus Ž . showed strong diel vertical migration from the surface waters to the oxygen minimum zone OMZ . Copepodite stage V of C. euxinus showed seasonal migration, and was observed in diapaused phase at the OMZ in June and in September Ž . Ž . samplings. The large 1000–2000 mm and medium 500–1000 mm fractions of copepods had maximum gut fluorescence at night. Total grazing represented 32% of daily total integrated primary production. Phytoplankton carbon ingested met all three fractions of the basic metabolic requirements of the copepod community in the Black Sea. q 2001 Elsevier Science B.V. All rights reserved. Keywords: Copepods; Vertical distribution; Grazing; Black Sea 1. Introduction The Black Sea ecosystem presently faces dramatic changes in the last decades. Changes in the species composition and in phytoplankton blooms have taken place. These changes seem to be connected with the eutrophication and other types of contaminants from river, atmospheric and land based sources and new Ž invader into the ecosystem Mnemiopsis leidyi Zait- sev and Alexandrov, 1997; Mee, 1992; Kideys, 1994; ) Tel.: q 90-324-521-2406; fax: q 90-324-521-2327. Ž . E-mail address: sengul@ims.metu.edu.tr S. Besiktepe . Cociasu et al., 1996; Kovalev et al., 1998; Shiganova et al., 1998; Moncheva et al., 1998; Kideys et al., . 2000; Petruanu et al., 1999 . For the better under- standing of the conditions, some scientific researches have been conducted at national, regional and inter- national levels. One of these programs was NATO TU-Black Sea project and one of the major goals of this project was to contribute environmental and oceanographic data to the improvement of the health of the Black Sea through the application of interdis- ciplinary ecosystem models of the lower trophic levels of the biological community. Within this con- text, the aim of the present study is to report the 0924-7963r01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. Ž . PII: S0924-7963 01 00029-X