AUTHOR=Liu Huiling , Chai Xinru , Zhang Dongxu , Xu Wenjun , He Jie 

TITLE=Effect of Sinonovacula constricta on sediment microbial numbers and easily degradable organics in shrimp-crab polyculture systems

JOURNAL=Frontiers in Marine Science

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.1012893

DOI=10.3389/fmars.2022.1012893

ISSN=2296-7745

ABSTRACT=<p>To explore the influence of different densities of <italic>Sinonovacula constricta</italic> on the composition of easily degradable organic matter and related functional bacteria, four experimental ecosystems were established: three polyculture systems (PMB<sub>1</sub>, PMB<sub>2</sub>, and PMB<sub>3</sub>) of <italic>Portunus trituberculatus</italic> and <italic>Marsupenaeus japonicus</italic> with different stocking densities of <italic>S. constricta</italic> (11.6, 23.1, and 34.7×10<sup>4</sup> ind./hm<sup>2</sup>, respectively) and a polyculture system with only <italic>P. trituberculatus</italic> and <italic>M. japonicus</italic> (PM). Among the easily degradable organic components in all aquaculture systems, protein content was the highest (0.74%~0.86%), followed by carbohydrates (0.16%~0.21%) and lipids (0.06%~0.13%). In the high-density (34.7×10<sup>4</sup> ind./hm<sup>2</sup>) <italic>S. constricta</italic> mixed culture system, the contents of carbohydrates, lipids, and proteins in the sediment were significantly lower than those of the other polyculture systems. The number of cellulose-decomposing bacteria in PMB<sub>3</sub> was 3.79×10<sup>6</sup> cfu/g, which was significantly higher than that in the other systems. The number of starch-degrading bacteria and glutin-degrading bacteria was the lowest in PMB<sub>3</sub>, 1.26×10<sup>4</sup> cfu/g, and 160.00 cfu/g, respectively. The number of lipid-degrading bacteria in PMB<sub>3</sub> was 0.77×10<sup>4</sup> cfu/g, which was significantly lower than that in the other systems. The easily degradable organics content in sediment was significantly positively correlated with the corresponding functional bacteria. The results showed that mixed culture of <italic>S. constricta</italic> could reduce the content of easily degradable organics in the sediment of mariculture ponds and change the number of functional bacteria in the sediment and the availability of degradable organic sediments may determine the abundance of corresponding degradable bacteria.</p>