Feeding habits of &lt;i&gt;Calanus sinicus&lt;/i&gt; (Crustacea: Copepoda) during spring and autumn in the Bohai Sea studied with the herbivore index

Guang-Tao Zhang,Chao-Lun Li,Song Sun,Jun Sun,Hong-Yan Zhang,Xiu-Ren Ning

doi:10.3989/scimar.2006.70n3381

Abstract

Pigment ingestion rate (PIR) and egg production rate (EPR) of the dominant copepod Calanus sinicus, as well as chlorophyll-a concentration and phytoplankton assemblages were measured in the Bohai Sea, North China in June 1997, October 1998 and May 1999. A herbivore index (H) was also calculated as the carbon specific ratio of PIR and EPR, in order to investigate its feeding habits in the spring and autumn phytoplankton bloom respectively. On average, chlorophyll-a concentration was relatively similar (1-1.34 mg m(-3)) in the three cruises, but PIR was quite different. It was 3.24 mu g C female(-1) d(-1) in October, equivalent to one half of the PIR for June and one third of the PIR for May. Average EPR was highest in May, and quite similar during the other two months. According to H values, herbivorous feeding contributed 100% of the egg production of C. sinicus in June, 82.5% in May, but only 47.8% in October. It is possible that omnivorous feeding of C. sinicus in October was induced by a prevalence of large-sized diatoms and sufficient non-phytoplankton food resources during the autumn bloom period.

Highlights

In the past 20 years, many “herbivorous” copepods were found exploiting food items other than phytoplankton, such as detritus, bacteria and protozoan (Kleppel, 1993; Harris, 1996). Copepod consumption of these non-phytoplankton items probably plays an important role in both the carbon cycling and zooplankton population dynamics
Pure diatom diets can lead to deleterious effects on copepod reproduction and development (Ban et al, 1997; Ianora et al, 2003), but in some other studies these effects can be overcome by omnivorous feeding (Ban et al, 2000; Kang and Poulet, 2000; Lacoste et al, 2001; Turner et al, 2001; Miralto et al, 2003)
We aimed to investigate the feeding habits of C. sinicus, i.e. herbivorous or omnivorous, in spring and autumn respectively, and to explain in more detail its relation with phytoplankton abundance and assemblages

Summary

Introduction

In the past 20 years, many “herbivorous” copepods were found exploiting food items other than phytoplankton, such as detritus, bacteria and protozoan (Kleppel, 1993; Harris, 1996). Copepod consumption of these non-phytoplankton items probably plays an important role in both the carbon cycling and zooplankton population dynamics. Many forms of primary production, such as dis-. Solved organic matters and tiny cells, are inaccessible to large consumers before being repackaged in the microbial food loop. Copepods are key intermediaries through which this part of primary production re-enters the main food web. Pure diatom diets can lead to deleterious effects on copepod reproduction and development (Ban et al, 1997; Ianora et al, 2003), but in some other studies these effects can be overcome by omnivorous feeding (Ban et al, 2000; Kang and Poulet, 2000; Lacoste et al, 2001; Turner et al, 2001; Miralto et al, 2003)

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Conclusion