No abstract

No abstract

Due to the discharge of nutrients into the East China Sea, severe eutrophication has appeared in Hangzhou Bay. Therefore, we cultivated Gracilaria verrucosa on a large scale in the Jinshan enclosed sea with an area of 1.72 km 2 in the northern part of Hangzhou Bay to perform bioremediation. The Fengxian enclosed sea with an area of 2.3 km 2 and 50 km far from Jinshan was used as the control. The results showed that the Hangzhou Bay was severely eutrophicated before G. verrucosa cultivation. During the period of cultivation between August 2006 and July 2007, the annual growth rate of G. verrucosa was 9.42% day −1 , and the sea water quality was improved from worse than grade IV to grades II-III, with the concentration of dissolved inorganic nitrogen (DIN) and PO 4 -P significantly lower than that in the Fengxian enclosed sea (p< 0.01). The concentration of NH 4 -N, NO 3 -N, NO 2 -N, and PO 4 -P after G. verrucosa cultivation was decreased by 54.12%, 75.54%, 49.81%, and 49.00%, respectively. The density of phytoplankton in the Jinshan enclosed sea with cultivation of G. verrucosa was 6.90-126.53×10 4 cells m −3 , which was significantly lower than that in the Fengxian enclosed sea. In addition, species diversity, richness, and evenness was significantly increased after cultivation of G. verrucosa in the Jinshan enclosed sea compared with that in the Fengxian enclosed sea. The density of Skeletonema costatum, Prorocentrum micans, and Prorocentrum donghaiense, which were the usual species of red tides at the coastal sea of China, in the Jinshan enclosed sea with cultivation of G. verrucosa was significantly lower. Based on these results, if the water quality in the Jinshan enclosed sea were to be maintained at grade I (DIN ≤0.20 mg L −1 ) or II (DIN ≤0.30 mg L −1 ), 21.8 t or 18.0 t fresh weight of G. verrucosa need to be cultivated, respectively. These results indicated that largescale cultivation of G. verrucosa could play a significant role in the bioremediation of Hangzhou Bay.

No abstract

Coastal lagoons are highly productive ecosystems. However, coastal lagoons are experiencing the effects of human disturbances at an increasing rate. Bacteria are key ecological players within lagoons, yet little is known about the magnitude, patterns, and drivers of diversity in these transitional environments. In this report, a seasonal study in the Fengxian artificial lagoon (China) was conducted, along with the adjacent sea, to simultaneously explore diversity in different domains and their spatio-temporal variability.Bacterioplankton community structures of surface waters from four sites over the course of four seasons were characterized with Illumina platform sequencing technology. The results showed significant differences in bacterioplankton communities between the four sites. In addition, the results indicated a difference between the enclosed lagoon and offshore waters during the same seasons. Seasonality was shown to be more important than spatial variability in shaping assemblages. The community barplot showed that, with the exception of January which had the same dominant genus in both the enclosed lagoon and offshore water, all other seasons had different genus. Likewise, the heatmap showed that the largest dissimilarity of bacterial species diversity occurred in July between the enclosed lagoon and offshore water, while the highest similarity was in January. This result paralleled genetic studies which also showed that gene expression had not only similar seasonal but spatial changes. Canonical correspondence analysis (CCA) analysis of all water samples showed that environmental indicators of dissolved oxygen, temperature, PO 4 , NO 2 , and Chemical Oxygen Demand (COD) contributed to the variation. Bacterial communities in the lagoon are affected by temperature, dissolved oxygen and NO 2 , while the dominant bacterial communities offshore are affected by COD and PO 4 . This study provided evidence for a temporally dynamic structure of bacterial assemblages in lagoons.In this vulnerable ecosystem, there is interplay of seasonally-influenced environmental drivers that works together to shape bacterial assemblages. The goal is to identify beneficial microbial population that improved water quality in an enclosed lagoon in order to provide a new perspective for optimizing the breeding environment.PeerJ Preprints | https://doi.org/10.7287/peerj.preprints.26935v1 | CC BY 4.0 Open Access |