Abstract
Creseis acicula is a swimming shelled pteropod species, widely distributed in the world’s oceans. In 2020, an unprecedented bloom of C. acicula was observed in Daya Bay, and lasted from June to July. To date, there is very limited information on the physiological characteristics of this species, which is essential to understand bloom dynamics. In the present study, the physiological performances of C. acicula in response to temperature (17–35°C) and salinity (18–38 ppt) were investigated. The oxygen consumption (OCR) and calcification rates (CR) of C. acicula peaked at 32 and 26°C, respectively, while ammonia excretion rate (AER) significantly increased with increasing temperature. The thermal coefficient Q10 (respiration) of C. acicula dropped to a minimum value between 32 and 35°C, suggesting that they were in a stressful status. The O:N ratio ranged from 3.24 to 5.13, indicating that protein was the major catabolism substrate. Temperature exerted a stronger effect on the OCR and AER of C. acicula. Salinity has a more influence on CR. The preferable temperature for C. acicula ranges from 29 to 32°C, and the preferable salinity ranges from 28 to 33 ppt. Based on a comprehensive consideration, we presumed that the warmer seawater temperature around the thermal discharge area of Daya Bay nuclear power plant is a possible cause for the bloom of C. acicula.
Highlights
Creseis acicula belongs to the Pteropoda order, Cavoliniidae family, and Creseis genus
The Oxygen consumption rate (OCR) of C. acicula significantly increased with temperature and salinity values of 32◦C and 28 ppt, respectively, and decreased thereafter [one-way ANOVA, temperature: F(6,20) = 80.112, P < 0.05; salinity: F(4,14) = 5.906, P < 0.05; Figure 2]
The results of the present study suggest that C. acicula has the ability to regulate its metabolisms, e.g., respiration, ammonia excretion, and calcification rates, within a relatively broad range of water temperature and salinity
Summary
Creseis acicula belongs to the Pteropoda order, Cavoliniidae family, and Creseis genus. This pteropod is the largest in the Creseis genus. C. acicula lives in the upper portion of the water column (less than 500 m), and is abundant in the Atlantic, Indian, and Pacific Oceans (Albergoni, 1975). In Daya Bay, South China Sea, C. acicula generally appear from March to November each year, with average abundances ranging from 0.04 to 1.9 inds m−3 (Xu, 1989). A massive aggregation occurred from June to July 2020 near the thermal discharge area of Daya Bay Nuclear Power Plant (DNPP), with the highest abundance reaching 4525–5595 inds m−3 (Dai et al, 2020; Zhong et al, 2021). Large amount of C. acicula gathered around the thermal discharge area of DNPP and seriously affected the normal operation of the plant
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