Physicochemical Properties and Bacterial Diversity of Sediment in Sea Cucumber Culture Ponds under High Summer Temperatures

Abstract

This study examined the effect of aquaculture management parameters on sea cucumbers in culture ponds during high summer temperatures. The physicochemical properties of 18 sediment samples from six sea cucumber culture ponds were assessed at a high temperature (HT) and the end of the high temperature (EHT) stages of summer. High-throughput sequencing was used to analyze the bacterial community composition and diversity of the sediment in the culture pond. The results showed that total nitrogen (TN), total carbon (TC), total organic carbon (TOC), ammonia nitrogen (NH4+), total sulfur (TS), sulfate (SO42−), and sulfide (S2−) contents were the lowest in the Geziling sediments at both stages, indicating a favorable sediment environment. The TN, TC, TOC, and NH4+ contents decreased significantly in the Wulei Island sediments during the EHT stage, indicating strong self-purification capacity. The TN, TC, TOC, NH4+, TS, SO42−, and S2− were higher in the Rushankou and Xiaohongcun sediments during both stages, indicating a worse sediment environment. Alpha diversity analysis revealed increased bacterial diversity in the sediments during the HT stage when compared to that during the EHT stage. Correlation analysis between bacterial diversity and the physicochemical properties of the TN sediments had the greatest impact on bacterial diversity, followed by TOC, TC, NH4+, TS, S2−, SO42−, and NO2− (in order). Our results suggest that the physicochemical properties (TC, TOC, TN, and NH4+) of the culture pond sediment can significantly influence bacterial community composition and diversity. Management measures for aquaculture, including desilting and monthly water change, could positively affect these physicochemical properties and the bacterial community structure of the sediment. These findings will provide a reference for healthier aquaculture practices of Apostichopus japonicus under high summer temperatures.