Optimization of photosynthesis, growth, and biochemical composition of the microalga Rhodomonas salina—an established diet for live feed copepods in aquaculture

Abstract

The cryptophyte Rhodomonas salina is widely used as feed for copepod cultures. However, culturing conditions to obtain high-quality algae have not yet been efficiently optimized. Therefore, we aimed to develop a cultivation protocol for R. salina to optimize its nutritional value and provide technical recommendations for later large-scale production in algal photobioreactors. We studied photosynthesis, growth, pigments, fatty acid (FA) and free amino acid (FAA) composition of R. salina cultured at different irradiances (10-300 μmol photons m −2 s −1 ) and nutrient availability (deficiency and excess). The optimal range of irradiance for photosynthesis and growth was 60-100 μmol photons m −2 s −1 . The content of chlorophylls a and c decreased with increasing irradiance while phycoerythrin peaked at irradiances of 40-100 μmol photons m −2 s −1 . The total FA content was maximal at optimal irradiances for growth, especially under nutrient deficiency. However, highly unsaturated fatty acids, desired components for copepods, were higher under nutrient excess. The total FAA content was highest at limiting irradiances (10-40 μmol photons m −2 s −1 ) but a better composition with a higher fraction of essential amino acids was obtained at saturated irradiances (60-140 μmol photons m −2 s −1 ). These results demonstrate that quality and quantity of FA and FAA of R. salina can be optimized by manipulating the irradiance and nutrient conditions. We suggest that R. salina should be cultivated in a range of irradiance 60-100 μmol photons m −2 s −1 and nutrient excess to obtain algae with high production and a balanced biochemical composition as feed for copepods.

Influence of Salinity on Growth and Phycoerythrin Production of Rhodomonas salina

“…According to previous studies, nutrient availability, and irradiance are two environmental factors responsible for Rhodomonas sp. growth (Chaloub et al, 2015;Lafarga-De la Cruz et al,2006;Vu et al, 2015). Both factors directly influence microalgae growth during the logarithmic phase.…”

“…In this experiment setup, the nutrient availability in the culture medium is considered as nutrient deficiency culture (Vu et al, 2015). The R. salina growth was depending on the nutrient availability since Marraskuranto et al/Squalen Bull.…”

“…According to several studies, PE production from Rhodomonas sp. is inf luenced by nitrate concentration, photon flux density (light intensity), and temperature (Bartual, Lubián, Gálvez, & Niell, 2002;Chaloub, Motta, de Araujo, de Aguiar, & da Silva,, 2015;da Silva, Lourenco, & Chaloub, 2009;Vu et al, 2015). Compared to chlorophyll, other pigments or accessories pigments, i.e.…”

Testing the yield of a pilot‐scale bubble column photobioreactor for cultivation of the microalgaRhodomonas salinaas feed for intensive calanoid copepod cultures

“…The cryptophyte R. salina was obtained as strain K‐1487 from the Scandinavian Culture Collection of Algae and Protozoa (SCCAP). The stock culture of R. salina was grown in the laboratory at Roskilde University (RUC) at standard conditions as described by Vu et al (). The cultures were maintained under a continuous irradiance of 80 μmol photons m −2 s −1 photosynthetically active radiation (PAR) in a climate room at 20°C.…”

The effects of temperature and photoperiod on egg hatching success, egg production and population growth of the calanoid copepod, Acartia grani (Calanoida: Acartiidae)

“…Food quantity is known to affect egg production rate (Zhang et al., ), whereas food quality mainly affects hatching success (Guisande, Rivero & Maneiro, ). A. grani adults used in our experiments were fed Rhodomonas , an algal diet widely used as feed for copepod cultures (Vu et al., ) and normally high in EPA compared with DHA (Støttrup et al., ). Even though no chemical analysis was performed on the microalgae fatty acid and amino acid composition, it is possible that an imbalance of these essential elements could have affected females' reproductive characters and, consequently, egg hatching success (Tang & Dam, ).…”