Evaluation of plant extracts as aquaculture feed additives: Ecotoxicological and physiological responses in marine species

In the context of sustainable aquaculture, plant extracts are considered potential feed additives to enhance fish immunity while minimizing environmental risks. This study evaluates the ecotoxicity and physiological impacts of four plant extracts—gallnuts (Rhus chinensis), green chiretta (Andrographis paniculata), white mustard (Sinapis alba), and betel nut (Areca catechu)—on various marine species and juvenile barramundi (Lates calcarifer). The primary objective is to assess their potential as functional feed additives in aquaculture, while identifying potential environmental risks and physiological effects associated with their use. The ecotoxicological effects of these extracts were tested on model organisms at different trophic levels, including bacteria Aliivibrio fischeri, diatom Phaeodactylum tricornutum, rotifer Brachionus plicatilis, and brine shrimp Artemia salina. The 50 % effective concentration (EC₅₀) revealed a toxicity rank from least to most toxic as white mustard < green chiretta < betel nut < gallnuts. A principal component analysis (PCA) indicated that EC values (EC₅₀, EC₂₀, and EC₁₀) were the key factors distinguishing species sensitivity to the plant extracts. In the juvenile barramundi feeding trial, plant extracts were incorporated into feed at varying concentrations (0 %, 0.1 %, 1 %, and 10 %) for a 24-hour acute assay. The correlation analysis revealed that increased extract concentrations significantly inhibited red blood cell counts, nitric oxide concentration, complement component C3 concentration, aspartate aminotransferase activity, and alanine aminotransferase activity in barramundi. At the same time, serum glucose, globulin, and acid phosphatase activity exhibited varying responses in fish, depending on the extract and concentration. These physiological changes suggest that the plant extracts exert both temporary immunomodulatory and stress-alleviating effects in barramundi. These results indicate that although some plant extracts can be used as additives in aquaculture feed, their potential toxicological and physiological effects on environmental organisms should be considered before their extensive application in aquaculture.