Can clams clean up aquaculture?

Aquaculture is a rapidly growing industry, but suffers from high levels of waste. Using shellfish as part of a bioremediation system has been proposed and is becoming more popular in China. This is thought to reduce nutrient outflow into the environment by increasing microbial activity within the wastewater treatment through bioturbuation. Lukwambe et al (2018) seeks to demonstrate this is the case. They used a simple experimental design; there were two treatments, one with the clam Sinovacula constricta and the other without, as a control. Both treatments pumped water from an intensive shrimp farm for 35 days, then had a total of 3 sediment samples taken from each. These were then split into the top (0-4cm) middle (4-8cm) and bottom (8-12cm) of the sediment. Then community structure was determined using high throughput sequencing and grouping into OTUs of 97%. Enzyme activity was determined and organic matter (in the form of total organic carbon, total organic nitrogen and total phosphorus) was measured. In the clam treatment enzyme activity increased and microbial diversity increased and favoured keystone denitrifying & nitrifying taxa. Total organic carbon and nitrogen levels were lower in the experimental treatment however, whilst total phosphorus showed no significant difference overall, in the 8-12cm and 0-4cm sample there was a significant decrease. Overall this paper concludes that there was a significant difference brought about by the clams and that they appear to be a fairly effective bioremediation tool.