Lara E. Stuthmann1, Leona Ritter von Stein 3,4 , Karin Springer2, Andreas Kunzmann1
1 Leibniz Centre for Tropical Marine Research, Fahrenheitstraße 6, 28359 Bremen, Germany
2 Marine Botany, University of Bremen, Bibliothekstraße 1, 28359 Bremen, Germany
3 Helmholtz Centre for Ocean Research Kiel (GEOMAR), Duesternbrooker Weg 20, 24105 Kiel, Germany
4HanseGarnelen AG, Herrenweide 6, 25348 Glückstadt, Germany
Sea grapes (Caulerpa lentillifera) are edible macroalgae valued for their nutritional benefits and special texture. This alga is of high demand in Asia and cultivated among others in Vietnam. Land-based culture of tropical shrimp Litopenaeus vannamei in recirculation aquaculture systems (RASs) is popular in Germany and a simultaneous culture with other species, like sea grapes, could lead to a more efficient resource use and provision of tropical sea vegetables to European customers. Therefore, we explore the potential to use L. vannamei process water for fertilization of C. lentillifera. The process water was diluted to reach five nitrate treatments (artificial seawater, low, medium, high, pure process water, with ~2, 48, 144, 720, 14400 µmol L-1, respectively) and different NO3–/ PO43- ratios (28, 5) through additional PO43- feralizations, following literature suggestions. Sea grapes at nitrate treatments medium and high, independently of the PO43- fertilization, showed significantly higher relative growth rates than other nitrate treatments. As well as a larger share of economically valuable frond thallus parts, compared to stolons. Additionally, photosynthesis, amino acid (AA) pattern and total hydrolysable AA (THAA) amount were influenced by nitrate treatments. A two-way ANOVA revealed a significant effect of nitrate treatment and the interaction with PO43- fertilization (p < 0.05) on THAA, with PO43- fertilized medium and all high treatments showing the highest THAAs. The preliminary results revealed that sea grape fertilization with L. vannamei process water could increase the algae’s quality and growth, initiating a discussion for a simultaneous culture of both species in intensive RASs.