Growth performance of Oikopleura dioica during flood seasons in Jiaozhou Bay: Implications on early maturation favored rapid response to environmental fluctuation

Abstract

Gelatinous tunicates with rapid bloom capability are ubiquitous and important in marine ecosystems. To evaluate the rapid response of a most common appendicularian species, Oikopleura dioica, to fluctuating environmental conditions, spatio-temporal abundance, chlorophyll a concentration and body size was investigated twice a week at 5 stations in Jiaozhou Bay, a eutrophic and semi-closed embayment of China. The highest recorded O. dioica abundance was 28107 ind. m−3. Mature individuals attained body lengths ranging from 114.92 to 619.11μm. Compared with the body/gonad length relationship established in laboratory studies, the natural population in Jiaozhou Bay had greater gonad length at the same body length. The difference of gonad length between natural and laboratory specimens was -1.04–6.03μm for matures and 24.93–30.63μm for immatures at various food regimes. Body size in this study showed a significant positive correlation with chlorophyll a concentration of the size range 0.2–20μm. Considering that maturation at smaller body size and shorter generation time arising therefrom can result in higher intrinsic rates of natural population increase, it suggests that early maturation favors a rapid response of O. dioica to fleeting phytoplankton blooms. Although such response was limited to blooms of small size phytoplankton, it may help on recovery of micro-phytoplankton dominance in natural environments.