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Vol. 47 No. 4, 2008
Copepod Gut Contents, Ingestion Rates, and Feeding Impacts in Relation to Their Size Structure in the Southeastern Taiwan Strait
Li-Chun Tseng1, Ram Kumar2, Hans-Uwe Dahms1,Qing-Chao Chen3, and Jiang-Shiou Hwang1,*
1Institute of Marine Biology, National Taiwan Ocean University, Keelung 202, Taiwan
2Department of Zoology, Acharya Narendra Dev College, University of Delhi, Delhi 10007, India
3South China Sea Institute of Oceanology, Chinese Academy of Science, Guangzhou 510301, China
Li-Chun Tseng, Ram Kumar, Hans-Uwe Dahms, Qing-Chao Chen, and Jiang-Shiou Hwang (2008) Copepod
gut contents, ingestion rates, and grazing impact on phytoplankton were
estimated at 19 sampling stations off the Penghu Archipelago (the
Pescadores), in the Taiwan Strait during the summer monsoon
season. Copepods were collected on board the Ocean Research Vessel
III of the National Science Council within the upper 5 m by horizontal
tows using a NORPAC 4.5-m-long conical net with a 1 m opening diameter
and a 333 μm mesh size. The gut fluorescence method was used to
estimate in situ ingestion rates and clearance rates of copepods.
The abundance and species composition of copepods varied among sampling
stations. A size-fractionation approach was applied, and the gut
pigment contents and ingestion rates were estimated in 3 size
categories (small, < 1 mm; medium, 1-2 mm; and large, > 2
mm). Results showed that gut pigment contents were higher for
larger copepods and lower for smaller ones. Estimates of the
copepod grazing impact showed that < 1% of the total phytoplankton
standing stock was grazed daily during the early summer monsoon
period. Grazing impact for the 23 most abundant taxa, which
accounted for up to 90% of all copepods counted at each station,
demonstrated large spatial variability ranging 0.001%-0.210% of the
chlorophyll a standing stock. The highest grazing impact was
recorded at station 18, a coastal station situated in the Penghu
Channel, southwest of Penghu I., whereas the lowest impact was recorded
at station 11 near the center of the Strait, northeast of Penghu
I. The smaller copepod fractions were responsible for most of the
grazing impact, due to their numerical dominance in these coastal
waters. Variables affecting copepod community grazing impact
estimates are discussed.
Key words: Taiwan Strait, Copepod, Gut contents, Feeding, Trophic ecology.
*Correspondence: Fax: 886-2-24629464. E-mail:Jshwang@mail.ntou.edu.tw
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