Isolating Key Contributors of Microbial Biofloc to Litopenaeus vannamei Growth: Can Shrimp Consume, Digest, and Receive Supplemental Nutrition From Common Biofloc Microbes?
Zero-exchange, microbial biofloc-based, intensive shrimp culture systems are a new, more environmentally responsible approach to shrimp aquaculture. The diverse biofloc microbe community within these systems recycles nutrients and provides supplemental nutrition to shrimp. In order to better understand how biofloc community composition affects shrimp growth, individual microbe species representative of common taxa within biofloc were tested for their dietary availability and effect on Pacific white shrimp Litopenaeus vannamei. The microbes tested, which included two diatom species, a eustigmatophyte, and a cyanobacterium, were grown as monocultures and concentrated as feed supplements. Microbe-supplemented custom-made feeds and a control feed were then fed to 30 replicate aquaria of shrimp at 69 shrimp m⁻² for 35 days. Microbial supplements did not enhance or inhibit shrimp growth, feed conversion ratio, or survival when offered as feed supplements. Although below-threshold supplement concentration may have caused this result, treatment effect may have been masked by overall poor shrimp growth in the experimental system. A second experiment tested the ability of L. vannamei to consume each of the four microbe species from suspended monoculture and digest the cells. Each of 160 replicate shrimp were starved for 24 hours and placed in a flask of each monoculture for time increments of either 15, 30, 60, or 90 minutes. Stomach and intestine samples were then taken and assessed for chlorophyll a concentration and number of intact microbe cells using fluorometry and microscopy, respectively. Both assessment methods indicated that shrimp were able to readily consume and digest suspended diatoms, but could not readily consume or digest the eustigmatophyte or cyanobacterium. Behavioral observation of shrimp and scanning electron microscope evaluation of feeding appendages indicated that a filter-feeding behavior may explain differential consumption of microbes. Studies like these may aid in the development of more efficient, economical, and sustainable shrimp aquaculture.
Whiteleg shrimp -- Feeding and feeds; Whiteleg shrimp -- Nutrition; Whiteleg shrimp -- Growth; Shrimp culture