Distribution and feeding impact on phytoplankton of copepod in waters of western Taiwan

• Main Authors: LI-CHUN TSENG, 曾立鈞
• Other Authors: JIANG-SHIOU HWANG
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/94098794514625072125

博士 === 國立臺灣海洋大學 === 海洋生物研究所 === 96 === In order to reveal spatial communities patterns and feeding impact on phytoplankton of copepod in waters of western Taiwan. Six cruises and two seasonal monitor studies were taken in southwest East China Sea, Taiwan Strait and South China Sea from June 1998 to December 2005. The East China Sea is characterized by a complex hydrodynamic regime and high biological productivity and diversity. Copepod abundance was significantly higher in the estuary of the Yangtze River runoff mixture waters and lowest at the Kuroshio Current Region. The calanoid Parvocalanus crassirostris was the most frequently occurring and abundant species. Overall, there was a strong correspondence between the distribution of certain copepod species and water masses. Differences between the Mainland China shelf, the northern Taiwan Strait and the Kuroshio Current Region were characterized by differences in species composition and abundance. Water mass boundaries in the study area were exclusively indicated by distinct differences in species composition, emphasizing a correlation between copepod communities and water masses of the southwest East China Sea in summer. At northern Taiwan Strait, seasonal monsoons play a pivotal role in shaping species richness and diversity of plankton organisms in the water masses. Four copepod communities were distinguished prior to the advent of the northeast or southwest monsoonal winds as well as during the peak period of the respective monsoons. Studied results also reveal the influence of the Kuroshio Branch Current in the study area on copepod assemblages, with seasonal successions being determined by southwestern and by northeastern monsoonal winds. At southern Taiwan Strait, copepod assemblages were dominated by Temora turbinata which occurred in > 97 % samples with a relative abundance of 75.46 % combining all sampling cruises. The ordination diagram derived from non-metric multidimensional scaling separated samples on the basis of season and revealed that different sampling stations clustered differently during each cruise. The outfall area studied here correlates with lower copepod densities represented by a few species that show higher relative abundance in comparison with non-affected areas. Present studies provide the first example where copepod assemblages indicate useful information about environmental changes in the course of sewage disposal at a fixed outlet site. Studied of South China Sea indicated the high copepod diversity in the study area may mainly be caused by both the Kuroshio Current and the fresh water from Mainland China. Water currents in the region transport marine planktonic fauna that comprise predominantly copepod from subtropical and tropical water masses. Most species of copepods performed a common diel vertical migration, descending during daytime and ascending at night at different rates to different depth zones. There were smaller numbers of species and lower diversity indices in surface waters (2 – 0 m) as compared to depths below 50 m. In feeding studied, copepod gut contents, ingestion rates and feeding impact on phytoplankton were estimated at stations off the Pescadores Islands and South China Sea. 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 gut pigment contents were higher for larger copepods and lower for smaller ones. Feeding impact demonstrated large spatial variability ranging from 0.001% to 0.210% of the chlorophyll a standing stock. The smaller copepod fractions were responsible for most of the feeding impact, due to their numerical dominance in these coastal waters. Variables affecting copepod community feeding impact estimates are discussed.