Seasonal dynamics of siphonophores in the waters off southern and northern Taiwan
Temporal and spatial distribution in species composition and abundance of siphonophores in relation to hydrographic variables in the waters off southern and northern Taiwan were investigated from December 2003 to August 2004. In total, 48 siphonophoran species belonging to 18 genera and 7 families were recognized, with the mean abundance of 2226 ¡Ó 1228 ind./1000 m3. The abundance of siphonophores showed an obvious seasonal change, lower in December and February and higher in May and August. The six most dominant species, together they contributed to 66.5 % of the numerical total of siphonophores, were Chelophyes contorta, Bassia bassensis, Chelophyes appendiculata, Abylopsis eschscholtzi, Abylopsis tetragona and Eudoxoides mitra. The dominant siphonophoran species exhibited apparent seasonal succession. Different dominant species showed different seasonal distribution patterns and most species were dominated by sexual generation. Result of the cluster analysis of siphonophoran data revealed 2 station groups. Group¢¹was mostly composed by the stations in February and May, and group ¢º contained the stations in May and August.
Forty-two siphonophoran species belonging to seven families and nineteen genera were recognized in the waters off northern Taiwan, with the mean abundance of 7129 ¡Ó 10240 ind./1000 m3. The abundance of siphonophores displaced an apparent seasonal change, significantly higher in February and August and lower in December and May. The six most dominant species, together they contributed to 79.4 % of the numerical total of siphonophores, were Diphyes chamissonis, C. appendiculata, Muggiaea atlantica, Lensia subtiloides, B. bassensis and E. mitra. The dominant siphonophoran species showed obvious seasonal succession and different dominant species exhibited different seasonal distribution patterns. Muggiaea atlantica and L. subtiloides were dominated by polygastric stage, while other species were mostly the eudoxid generation. Result of CA of siphonophores revealed 3 station proups. Group¢¹ was primarily the stations in the northwestern waters off Taiwan waters in December, Group ¢º contained the stations in the northeastern waters off Taiwan in all seasons. Group ¢» was mainly the sations in the northwestern waters off Taiwan in February and May.
The mean species number and species diversity were always higher in southern waters than in northern waters of Taiwan, but the overall mean abundance was three times higher in the northern waters than in the southern waters. The overall mean abundance in this study showed higher in December 2003 and lower in February and May 2004. Result of the ANOVA test revealed the significant difference in siphonophoran abundance between May and August 2004 in both southern and northern stations.
The abundance of total siphonophores was not significantly correlated with water temperature, salinity and chlorophyll a. The abundance of the six most dominant species in the southern Taiwanese waters was not significantly correlated to water salinity and chlorophyll a, but the abundance of C. contorta, B. bassensis, A. eschscholtzi and C. appendiculata were apparently influenced by water temperature. The abundance of the six most dominant species in the northern Taiwanese waters exhibited different correlationships with hydrographic variables, C. appendiculata showed significantly positive correlation with chlorophyll a, B. bassensis exhibited significantly positive correlation with water temperature, salinity and chlorophyll a, while E. mitra was significantly positively correlated with salinity.
Advisor:Tzeng, Wann-Nian; Wen-Tseng Lo; Shinn-Pyng Yeh
School:National Sun Yat-Sen University
School Location:China - Taiwan
Source Type:Master's Thesis
Date of Publication:07/24/2006