Factors that affect the growth and photosynthesis of the filamentous green algae, Chaetomorpha valida, in static sea cucumber aquaculture ponds with high salinity and high pH

Abstract

Chaetomorpha valida, dominant filamentous green algae, can be harmful to sea cucumber growth in aquaculture ponds of China. In order to understand the environmental factors affecting the growth of C. valida in sea cucumber aquaculture ecosystems, a combination of field investigations and laboratory experiments were conducted. Field surveys over one year revealed that C. valida survived in sea cucumber aquaculture ponds in salinities ranging from 24.3 ± 0.01‰ to 32.0 ± 0.02‰ and a pH range of 7.5 ± 0.02–8.6 ± 0.04. The high salinity and pH during the period of low C. valida biomass from January to May lay the foundation for its rapid growth in the following months of June to October. Many factors interact in the field environment, thus, laboratory experiments were conducted to determine the isolated effects of pH and salinity on C. valida growth. In laboratory experiments, samples were incubated under different salinity and pH conditions at 25 °C, with a light intensity of 108 μmol photon·m−2·s−1, and a photoperiod of 12 L:12 D. Results showed that salinity and pH significantly affect the growth and Fv/Fm (quantum yield of photosynthesis) of C. valida (p < 0.01). C. valida grew the longest at a salinity of 34‰ and a pH of 8.0. At 34‰ salinity, C. valida grew to 26.44 ± 5.89 cm in 16 days. At a pH of 8.0, C. valida grew to 67.96 ± 4.45 cm in 32 days. Fv/Fm was 0.635 ± 0.002 at a salinity of 32‰, and 0.550 ± 0.006 to 0.660± 0.001 at pH 7.0 to 8.5. Based on these results, we conclude that C. valida can bloom in sea cucumber ponds due to the high salinity and pH of coastal sea waters, which promote growth and maintain the photosynthetic activity of C. valida.

Effects of Chaetomorpha valida bloom development on the structure and succession of the phytoplankton community in Apostichopus japonicus culture ponds

“…since the phytoplankton population was correlated with temperature and light intensity, observations consistent with previous reports (Xing et al, 2019;Yan et al, 2014;Yunyan, Xiaorong, Bingxin, & Lanping, 2012). For bloom areas, environmental changes were more complicated because of the existence and variation of C. valida.…”

“…Our previous investigation showed that while C. valida grew in the pond all year, it thrived and bloomed from May to September, maintaining relatively low biomass in other months (Xing et al, 2019). Therefore, we conducted this field study from May to September in 2018.…”

“…Several reports have named increases in nutrient concentration as the key factor leading to rapid algal growth and blooms (Luo, Liu, & Xu, 2012;Nelson et al, 2008). Compared to the natural sea, nutrient loading in A. japonicus aquaculture system has increased , thus supporting C. valida blooms (Chi et al, 2009;Xing et al, 2019) For phytoplankton in normal areas, the nutritional conditions were adequate in the absence of C. valida, so they were not growth-limiting factors. For phytoplankton in bloom areas, competition with C. valida for nutrition forced the phytoplankton to utilize multiple forms of nitrogen (Glibert et al, 2016), so their population was positively correlated to TN concentrations.…”

“…In the past decade, Chaetomorpha valida (Cladophoraceae, Chlorophyceae), an invasive filamentous green alga, has emerged as a dominant macroalgal species that blooms frequently in A. japonicus culture ponds and causes a series of ecological effects (Chi, Wang, Luan, & Wang, 2009;Xing et al, 2019;Yunyan, Zifeng, Xiaorong, Lanping, & Delin, 2015;Zhang, Lv, et al, 2019). As phytoplankton can be very sensitive to changes in ambient conditions, in aquaculture a C. valida bloom may influence phytoplankton structure and succession either positively or negatively (Nelson et al, 2008;Valiela et al, 1997;Zhang, Xu, et al, 2013).…”

Sustainable Cultivation of Desmodesmus armatus SAG276.4d using Leachate as a Growth Supplement for Simultaneous Biomass Production and CO2 Fixation

“…Because they are photosynthetic microorganisms, the growth of microalgae is largely dependent upon the rate of photosynthesis. Photosynthetic efficiency is mostly decided on illumination conditions among other factors such as carbon dioxide concentration, temperature, pH, and nutrients (Singh and Singh 2015;Xing et al 2019). A similar result was reported by Eze et al (2018) where they found that the metabolism for the Desmodesmus sp.…”