Impact of raking and bioturbation-mediated ecological manipulation on sediment–water phosphorus diagenesis: a mesocosm study supported with radioactive signature

Abstract

The study examined the impact of raking and fish bioturbation on modulating phosphorus (P) concentrations in the water and sediment under different trophic conditions. An outdoor experiment was set to monitor physicochemical and microbiological parameters of water and sediment influencing P diagenesis. A pilot study with radioactive P was also performed under the agency of raking and bacteria (Bacillus sp.). Raking was more effective in release of P under unfertilized conditions by significantly enhancing orthophosphate (35%) and soluble reactive phosphate (31.8%) over respective controls. Bioturbation increased total and available P in sediments significantly as compared to control. The rates of increase were higher in the unfertilized conditions (17.6-28.4% for total P and 12.2 to 23.2% for available P) than the fertilized ones (6.5-12.4% for total P and 9.1 to 15% for available P). The combined effects of raking and bioturbation on orthophosphate and soluble reactive phosphate were also stronger under unfertilized state (54.5 and 81.8%) than fertilized ones (50 and 70%). The tracer signature showed that coupled action of introduced bacteria and repeated raking resulted in 59.2, 23 and 16% higher counts of radioactive P than the treatments receiving raking once, repeated raking and bacteria inoculation, respectively. Raking alone or in sync with bioturbation exerted pronounced impact on P diagenesis through induction of coupled mineralization and nutrient release. It has significant implication for performing regular raking of fish-farm sediments and manipulation of bottom-grazing fish to regulate mineralization of organic matter and release of obnoxious gases from the system. Further, they synergistically can enhance the buffering capacity against organic overload and help to maintain aquatic ecosystem health.

Deposition of shells modify nutrient fluxes in marine sediments: effects of nutrient enrichment and mitigation by bioturbation below mussel farms

“…The observed increased release of phosphate from the sediment can potentially be a consequence of the release of phosphate from phosphate-containing mucus linings of burrows, as has previously been observed for other nereidid polychaete species (Kristensen 2000). Berezina et al (2019) suggested that phosphate efflux from oxygenated sediments can be mediated by benthic animals through excretion and their bioturbation and bioirrigation, which was observed by Biswas et al (2017). In addition to this potential route for phosphate release through the mucus lining, the mucus produced by the polychaetes may also increase ammonium released from the sediment by stimulation of archaeal ammonia oxidizers as shown by Dale et al (2019).…”