Evaluating food quality of Arthrospira platensis for culturing Daphnia magna

Abstract Arthrospira is a filamentous cyanobacterium, rich in proteins and bioactive compounds, which is dietary supplement for human and animals. However, the contribution of this “superfood” on the life history traits of zooplankton is poorly addressed. We conducted Daphnia magna growth experiment using Arthrospira platensis comparing it with Chlamydomonas reinhardtii as quality food, to evaluate the nutritional adequacy of A. platensis for rearing daphnids. The trichomes of A. platensis was fragmented using a bead crusher for easier ingestion by the daphnids. The growth experiments revealed that A. platensis alone did not support both survival and growth of D. magna, but the daphnid survival increased after the addition of 20% C. reinhardtii. When A. platensis was supplemented with 50% and more of C. reinhardtii, however, growth was better than to those daphnids exclusively fed on C. reinhardtii. This suggests that A. platensis have some nutritional limitations essential for daphnids survival and growth instead of less digestibility or toxicity. Carbon (C) to Phosphorus (P) ratio (C:P = 46) of A. platensis was far below the threshold for daphnid growth (C:P = 116). This implies that P limitation is unlikely in A. platensis as feed for daphnids. Although the lack of some essential biochemicals such as sterols and polyunsaturated fatty acids may be a more plausible explanation, a small addition of A. platensis to standard microalgal foods would result in better growth of zooplankton, including daphnids.