||This study investigates seasonal and spatial distribution of planktonic pteropods associated with hydrographic conditions in the waters of southwestern Taiwan from December 2013 to August 2015. In total, 24 species of pteropods belonging to 10 genera and 4 families, were identified, with mean abundance, species number, and species diversity of 444 ± 182 ind/100m3, 6 ± 1, and 1.389 ± 0.112, respectively. Creseis acicula f. acicula, Creseis acicula f. clava, Limacina inflate, Creseis virgula f. virgule, and Creseis virgula f. conica were the five predominant species, together they accounted for 95.8% of the total pteropod catch.|
Sea surface temperature showed significant seasonal changes in the study area, higher in summer than in spring and winter, salinity and chl a concentration were not significantly different between seasons. The abundance of planktonic pteropods did not have ditinct seasonal changes, while species number was significantly higher in spring and summer than in winter, species diversity index was generally higher in spring. Results of cluster analysis based on hydrographic data showed that, community structure of pteropods was not significantly different between station groups within the same season, which implied that they were not affected by hydrographic condition within the season. MDS analysis of pteropods showed that, the assemblages of spring and summer were more similar with each other than with winter’s assemblage. In this study, pteropod assemblages could be classified into two species groups, the euryhaline-warm water species, are highly abundant and occur frequently, and hyperhaline-warm water species are always not abundant and occur in low frequency in the study area.
Linear regression showed that the pteropod abundance was significantly and negatively correlated with salinity, species number was significantly and negatively correlated with Chl a, and species diversity index was significantly and negatively correlated with Chl a. Creseis acicula f. acicula was significantly and negatively correlated with salinity and positively correlated with Chl a. Creseis virgula f. conica was significantly and positively correlated with sea surface temperature.