Sea Cucumber Culture Pond Research Articles

Integrated metabolome–metagenome analysis provides new insights into the impacts of sea cucumber (Apostichopus japonicus) aestivation on marine sediment composition

To explore the impacts of sea cucumber aestivation on sediment composition, sediments were sampled from aestivation sites and non-aestivation sites of a commercial Apostichopus japonicus culture pond, and metabolome–metagenome integrated analysis was performed. The results showed that 1) there was no significant difference in the microbial composition of sediments between aestivation and non-aestivation sites, but the relative abundances of some bacterial species changed slightly (especially pathogenic and spoilage species); 2) altered average relative abundances of potential host bacteria of antibiotic resistance genes (ARGs) were observed; 3) compared with non-aestivation site sediments, decreased average absolute abundances of two ARGs (tetW and floR) and increased average absolute abundance of one ARG (tetM) were observed in aestivation site sediments; and 4) a total of 74 significantly differentially expressed metabolites (SDMs) were identified in aestivation sites compared with non-aestivation sites. Four SDMs were closely correlated with antibacterial activity and bacterial physiology. All data observed in this study indicate that sea cucumber aestivation does not affect sediment microbial composition but does influence the relative abundances of some bacteria species; in addition, tetM might be considered a key indicator for monitoring and indicating ARG transfer or the sediment status of sea cucumber culture ponds during aestivation. In conclusion, the observations of this study enrich our knowledge of the impacts of the physiological behavior of marine ecosystem inhabitants on their ecosystem and provide novel insights for the management of aquaculture activities.

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

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.

Characterization of the Bacterial Community in the Ecosystem of Sea Cucumber (Apostichopus japonicus) Culture Ponds: Correlation and Specificity in Multiple Media

The bacterial community is an essential component of the aquaculture pond ecosystem, which not only improves and restores the aquaculture environment but also maintains a stable ecological equilibrium with the external environment. Here, Illumina 16S rRNA sequencing was conducted to characterize the bacterial community in the ecosystem of sea cucumber Apostichopus japonicus culture ponds, as well as their correlation with overall community structures. The alpha-diversities of bacterial community among water, sediment, and the gut of A. japonicus were consistent across culture ponds from different areas. Specifically, the richness and diversity of bacterial communities were the highest in sediment, followed by the gut, and the lowest in water. The dominant bacterial community among multiple media was Proteobacteria, which occupies a large proportion of the bacterial community structure, followed by Bacteroidetes and Verrucomicrobia. Highly similar bacterial community structures were present in multiple media among different areas, which provides evidence for deterministic natural evolution. Meanwhile, there was a significant difference (p < 0.05) in the specific bacterial communities across the multiple media. The specific functions of the multiple media in the ecosystem are the main reason for the formation of different bacterial communities. This work demonstrates that bacterial communities are the result of natural evolution within the ecosystem during adaptation to the required environment.

Response of bacterial community in sea cucumber Apostichopus japonicus intestine, surrounding water and sediment subjected to high-temperature stress

During the anomalously hot summer of 2018, the water temperature in a sea cucumber culture pond reached 28–33 °C. As a result, many sea cucumbers died from the high temperature, causing huge economic losses. Currently, changes in the bacterial community of the sea cucumber culture pond ecosystem during high temperature remain largely unknown. In this study, we investigated the effects of high temperature on the community composition and function of the sea cucumber culture pond ecosystem using high-throughput sequencing. The results showed that bacterial communities in the Apostichopus japonicus intestine, surrounding water and sediment responded quickly to high temperature, as indicated by an obvious succession process of the dominant and specific bacterial community. At high temperature, the richness and diversity of the bacterial community in the water and sediment decreased significantly (P < 0.05). The richness of the bacterial community in the A. japonicus intestine was significantly increased, and several potential pathogens (Staphylococcus, Vibrio and Pseudomonas) changed in terms of their dominance, increasing the risk of disease in A. japonicus. The predictive functional profiling based on the Clusters of Orthologous Groups (COGs) database showed that the restraint of water, sediment, and the intestine bacterial community under high temperature were characterized mainly by the weakening of metabolism, environmental information processing and cellular processes, and post-translational modification, protein turnover, chaperones. The bacterial community may adapt to a high temperature by enhancing information storage and processing, amino acid transport and metabolism, and carbohydrate transport and metabolism. In the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database analysis, 64 KEGG pathways showed significant differences, which could be classified into six KEGG A classes and 23 KEGG B classes. The main differences in the KEGG pathways of the bacterial community in water, sediment, and A. japonicus intestine at high temperature were reflected in metabolism, cell motility, and environmental information processing. By changing its structure and group behavior, the bacterial community might be inhibited or adapted to the high temperature with both attributes dependent on changes in functional proteins and metabolic pathways. The findings of this study provide guidance for maintaining a healthy aquaculture environment.

Molecular identification and population differentiation of Aurelia spp. ephyrae in sea cucumber aquaculture ponds of northern China

Aurelia spp. ephyrae have been reported to form blooms in sea cucumber aquaculture ponds in the Bohai and Yellow Seas. To identify the species, we carried out a genetic analysis of Aurelia spp. ephyrae and medusae based on mitochondrial 16S rRNA gene. Samples of four Aurelia sp. ephyrae populations were collected in sea cucumber aquaculture ponds and samples of four Aurelia sp. medusae populations were collected in coastal waters. Using a BLASTn search, we found that both the ephyrae collected in the aquaculture ponds and medusae collected in coastal waters belong to Aurelia coerulea. Seventeen haplotypes were recovered from the 16S rRNA gene. The overall haplotype diversity and nucleotide diversity of the 166 A. coerulea individuals were 0.686 and 0.329%, respectively, indicating high haplotype diversity and low nucleotide diversity. Moreover, the haplotype diversity of ephyrae populations were generally lower than that of medusae populations with close sampling points. The genetic differentiation between ephyrae populations collected in the sea cucumber aquaculture ponds and A. coerulea medusae collected in coastal waters was not significant, suggesting the ephyrae populations in the sea cucumber culture ponds were part of the same genetic group as the medusae populations in the coastal waters. Phylogeographic analysis of the 16S rRNA region revealed that there was no significant correlation between the haplotypes and the geographic distribution of populations. Pairwise fixation index values showed significant genetic differentiation and limited gene flow between A. coerulea population of Weifang and other locations.

Temporal dynamics of bacterial communities in the water and sediments of sea cucumber (Apostichopus japonicus) culture ponds

Bacteria communities in the aquaculture environment have been shown to greatly influence the growth of culture species. The sea cucumber (Apostichopus japonicus) is one of the most important aquaculture species in China, with numerous economic benefits. The growth and physiological characteristics of A. japonicus exhibit remarkable seasonal variation. However, current knowledge regarding the bacterial communities in A. japonicus culture ponds and their potential roles in the regulation of A. japonicus growth and physiology remain unclear. In the present study, Illumina sequencing based on the bacterial 16S rRNA gene was used to investigate the variations in bacterial communities in the surface water and sediment of A. japonicus culture ponds for a period of 1 year. The sediments exhibited a higher diversity of bacterial communities, and a higher abundance of microorganisms involved in sulfur metabolism; however, the surface water had a higher abundance of bacterial species associated with the degradation of organic matter. Furthermore, the bacterial communities in the water column showed a “3 + 1” monthly pattern and those in the sediments exhibited a seasonal succession. The higher abundances of bacteria associated with organic pollution degradation and functions associated with bio-active compound secretion were detected in water samples collected in April, August, and December. In contrast, bacteria that are considered to be food sources for A. japonicus were more abundant in pond sediments in autumn and spring. Finally, correlation analysis demonstrated that water temperature negatively regulated the sulfur cycling efficiency of bacterial communities in sediments of A. japonicus culture ponds. This study provides an important theoretical basis for the micro-ecological regulation of pond-cultured A. japonicus.

Corrigendum: Halalkalibacillus sediminis sp. nov., isolated from sediment of sea cucumber culture pond.

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Marinospirillum perlucidum sp. nov., a novel helical bacterium isolated from a sea cucumber culture pond.

Strain F3212T, Gram-stain-negative, aerobic, helical and motile bacterium, was isolated from the marine sediment collected in a sea cucumber culture pond located in Rongcheng, China. Strain F3212T grew optimally at pH 8.5, at 30 °C and in the presence of 3.0 % (w/v) NaCl. Phylogenetic analysis, based on 16S rRNA gene sequences, indicated that strain F3212T belongs to the genus Marinospirillum, clustering with M. celere, M. alkaliphilum, M. minutulum, M. megaterium and M. insulare (with 96.4, 94.6, 93.1, 92.4 and 92.1 % 16S rRNA gene sequence similarities, respectively). The chemotaxonomic properties of strain F3212T were similar to those of members of the genus Marinospirillum. Q-8 was the sole respiratory ubiquinone and the genomic DNA G+C content was 53.3 mol%. The major fatty acids were C18 : 1 ω9c, C16 : 0 and C18 : 0. The polar lipid pattern consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, an unidentifed lipid and an unidentified aminophospholipid. The average nucleotide identity scores for strains M. celere DSM 18438T and M. minutulum DSM 6287T were 74.5 and 69.4 %, respectively. The DNA-DNA homologies with M. celere DSM 18438T and M. minutulum DSM 6287T were less than 20 %. It's concluded that strain F3212T represents a new species of the genus Marinospirillum, for which the name Marinospirillum perlucidum sp. nov. is proposed. The type strain is F3212T (=KCTC 52892T=MCCC 1H00198T).

Halalkalibacillus sediminis sp. nov., isolated from sediment of sea cucumber culture pond.

A Gram-stain-positive, rod-shaped (0.3-0.4×1.2-2.0 µm), strictly aerobic and beige-pigmented bacterium, designated B3227T, was isolated from the sediment of a sea cucumber culture pond in Rongcheng, China (122.2° E 36.9° N). Its biochemical characteristics analysis revealed that the cells of this bacterium were catalase-positive and oxidase-negative. Cell growth occurred at 15-45 °C (optimum, 37 °C), pH 6.5-9.0 (pH 7.5-8.0) and in the presence of 0.0-22.0 % (w/v) NaCl (6.0-9.0 % NaCl). Phylogenetic analysis based on 16S rRNA gene sequencing indicated that strain B3227T exhibited similarities of 95.7, 95.5, 95.5 and 95.3 % to the type strains of Filobacillus milensis, Piscibacillus salipiscarius, Halalkalibacillus halophilus and Piscibacillus halophilus, respectively, and the results of physiological analyses revealed that strain B3227T was most similar to the genus Halalkalibacillus. The cells were endospore-forming and comprised an A1-γ-meso-diaminopimelic acid-type peptidoglycan. The respiratory quinone of strain B3227T was MK-7, and the dominant fatty acids were anteiso-C15 : 0 and anteiso-C17 : 0. The major polar lipids were diphosphatidylglycerol and phosphatidylethanolamine. The genomic DNA G+C content was 38.7 mol%. The average nucleotide identity values between strain B3227T and H. halophilus JCM 14192T (ANIb 69.5%, ANIm 84.2 %) and F. milensis JCM 12288T (ANIb 70.1 %, ANIm 84.1 %) were below the cut-off level (95-96 %) for species delineation. The results of kegg analysis revealed that strain B3227T could biosynthesize shikimate acid, a base compound for the formulation of the swine flu drug. Based on its morphological and physiological properties, as well as phylogenetic distinctiveness, strain B3227T should be placed into the genus Halalkalibacillus as a representative of a new species, for which the name Halalkalibacillus sediminis sp. nov. is proposed. The type strain is B3227T (=KCTC 33093T=MCCC 1H00193T).

Alteromonas sediminis sp. nov., isolated from sediment in a sea cucumber culture pond.

A novel strain, U0105T, was isolated from marine sediment of the coast of Weihai, China. The bacterium was aerobic, Gram-stain-negative, oxidase-positive, catalase-positive, rod-shaped and motile. Growth was observed at salinities of 1.0-6.0 % (w/v) NaCl (optimum with 2.0-3.0 %), temperatures of 20-40 °C (optimum at 37 °C) and pH of 6.5-9.5 (optimum at pH 7.0-7.5). The isolate could not reduce nitrate to nitrite. It could hydrolyse starch and Tweens 20, 40 and 60, but not casein or cellulose. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain U0105T belonged to the genus Alteromonas, with highest sequence similarity to Alteromonas aestuariivivens KCTC 52655T (97.1 %). The average nucleotide identity value and the digital DNA-DNA hybridization value between strain U0105T and A. aestuariivivens KCTC 52655T were 69.2 % and 21.2 %, respectively. Strain U0105T was found to contain Q-8 as the sole menaquinone and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), C16 : 0 and C18 : 1ω7c as the major fatty acids. The major polar lipids were identified as phosphatidylglycerol and phosphatidylethanolamine. The G+C content of the chromosomal DNA was 45.3 mol%. The combined genotypic and phenotypic data show that strain U0105T represents a novel species of the genus Alteromonas, for which the name Alteromonas sediminis sp. nov. is proposed. The type strain is U0105T (=KCTC 62080T=MCCC 1H00299T).

Microbial communities in sea cucumber (Apostichopus japonicus) culture pond and the effects of environmental factors

This study investigated microbial community composition as well as their correlation with environmental factors of Apostichopus japonicus culture ponds in northern China by 16S rRNA gene amplicon sequencing. The results showed that microbiota richness varied consistently with diversity in the pond ecosystem. Microbiota richness and diversity were highest in sediment, followed by gut of A. japonicus and water. The dominant bacterial phylum in the pond ecosystem is Proteobacteria. Gammaproteobacteriaeria and Flavobacteria are two dominant bacterial classes in the ecosystem. There is significant difference (p < 0.05) between dominant bacterial communities at the levels of order, family and genus. There is also remarkable regional difference (p < 0.05) between microbial community composition in the pond ecosystems. Specifically, microbial community composition in Changhai and Yingkou show a high similarity, so do those of Laoting and Rushan. According to the redundancy analysis of the microbial community composition and pond environmental factors, chemical oxygen demand is the dominant environmental factor determining microbial community composition in pond water; sulphide has the greatest influence on the microbial community composition in pond sediment; the rest of environmental factors have varied influence on microbial community composition in pond ecosystems.

Alteromonas flava sp. nov. and Alteromonas facilis sp. nov., two novel copper tolerating bacteria isolated from a sea cucumber culture pond in China

Two bacterial strains, P0211T and P0213T, were isolated from a sea cucumber culture pond in China. The strains were able to resist high copper levels. These two strains were characterized at the phenotypic, chemotaxonomic, and genomic level. They were completely different colors, but the 16S rRNA genes showed 99.30% similarity. Phylogenetic analysis based on the sequences of the 16S rRNA gene and five housekeeping genes (dnaK, sucC, rpoB, gyrB, and rpoD) supported the inclusion of these strains within the genus Alteromonas, and the two isolated strains formed a group separated from the closest species Alteromonas aestuariivivens KCTC 52655T. Genomic analyses, including average nucleotide identity (ANIb and ANIm), DNA–DNA hybridization (DDH), and the percentage of conserved proteins (POCP), clearly separated strains P0211T and P0213T from the other species within the genus Alteromonas with values below the thresholds for species delineation. The chemotaxonomic features (including fatty acid and polar lipid analysis) of strains P0211T and P0213T also confirmed their differentiation from the related taxa.The results demonstrated that strains P0211T and P0213T represented two novel species in the genus Alteromonas, for which we propose the names Alteromonas flava sp. nov., type strain P0211T (=KCTC 62078T=MCCC 1H00242T), and Alteromonas facilis sp. nov., type strain P0213T (=KCTC 62079T=MCCC 1H00243T).

Vertical Variations in Bacterial Community Composition and Environmental Factors in the Culture Pond Sediment of Sea Cucumber Apostichopus Japonicus

Lv, X.; Yu, P.; Mao, W., and Li, Y., 2018. Vertical variations in bacterial community composition and environmental factors in the culture pond sediment of sea cucumber Apostichopus japonicus. In: Wang, D. and Guido-Aldana, P.A. (eds.), Select Proceedings from the 3rd International Conference on Water Resource and Environment (WRE2017). Journal of Coastal Research, Special Issue No. 84, pp. 69–76. Coconut Creek (Florida), ISSN 0749-0208.The bacterial communities in culture pond sediments play important roles in the decomposition of organic matter, the release of nutrients and conservation of water quality. To explore the vertical variations in the microbial communities and environmental factors in the sediment accumulation of the sea cucumber (Apostichopus japonicus Selenka) culture pond, microbial community compositions were determined by high-throughput sequencing and environmental factors were measured using samples collected at different sediment depths. A total of 113,161 high-quality reads and 17,317 operational taxonomic units (OUTs) were obtained from different sediment samples. The results showed that the sediment of culture ponds has the characteristics of high organic matter, nitrogen, and sulfur contents and low phosphate contents. The bacterial richness was higher in the surface layer of the sediment. In total, 31 phyla were identified, among which the Proteobacteria, Acidobacteria, Bacteroidetes, Chloroflexi, Planctomycetes, Gemmatimonadetes and Nitrospirae were the dominant phyla in the sediment. Principle component analysis (PCA) showed that total-phosphate, salinity, NH4+, pH and PO43− were the main factors that influenced the microbial communities. This study will deepen our understanding of aquaculture environmental regulation and provide theoretical guidance for the exploitation of probiotics.

Artificial reefs for sea cucumber aquaculture confirmed as settlement substrates of the moon jellyfish Aurelia coerulea

In coastal areas with a high intensity of human activities, expansion of artificial structures may enhance Aurelia spp. blooms because these constructions may provide additional substrates for the settlement and proliferation of the polyps. In the present study, the possible occurrence and distribution of Aurelia coerulea ephyrae and polyps were investigated in sea cucumber (Apostichopus japonicus) culture ponds that contain huge amounts of artificial structures. Our results showed that A. coerulea ephyrae were widely distributed in the A. japonicus culture ponds along the Bohai and Yellow Seas. Furthermore, underwater photography revealed that polyps of A. coerulea mainly occurred on the undersides of the artificial reefs made by plastic sunshade nets, tiles and substrate cages. The artificial reefs may decrease the time A. coerulea planulae spend settling, provide more hidden, calm and shady places for the settlement and proliferation of A. coerulea planulae, and thus were suitable substrates for the moon jellyfish A. coerulea. Our study suggests that the A. japonicus culture ponds may act as nursery grounds for the jellyfish A. coerulea and may potentially enhance the blooms of this species in the coastal waters along the Bohai and Yellow Seas.

Robiginitalea sediminis sp. nov., isolated from a sea cucumber culture pond.

A Gram-stain negative, aerobic, non-motile, orange and rod/coccoid-shaped bacterium, designated O458T, was isolated from sediment collected from a sea cucumber culture pond located in Rongcheng, Shandong province, China (122°14'E, 36°54'N). Comparative analysis of 16S rRNA gene sequences revealed that strain O458T is a member of the genus Robiginitalea and is closely related to Robiginitalea biformata (95.7% sequence similarity) and Robiginitalea myxolifaciens (94.9%). Its DNA G+C content was 55.2mol%. The strain grew at temperatures between 15 and 45°C (optimum 33°C), from pH 6.5 to 8.5 (optimum pH 7.0-7.5) and between 1.0 and 6.0% (w/v) NaCl (optimum 2.0%). Strain O458T was found to contain menaquinon-6 (MK-6) as the only respiratory quinone, iso-C15:0, iso-C17:0 3-OH and Summed feature 1 (iso-C15:1 H and/or iso-C13:0 3-OH) as the major fatty acids. The major polar lipids were phosphatidylethanolamine (PE) and four unidentified lipids (L1, L2, L3 and L4). On the basis of the results of the phylogenetic and phenotypic analyses it is suggested that strain O458T represents a novel species of the genus Robiginitalea, for which the name Robiginitalea sediminis sp. nov. is proposed. The type strain is O458T (=KCTC 52898T=MCCC 1H00190T).

Polaribacter tangerinus sp. nov., isolated from sediment in a sea cucumber culture pond.

A Gram-stain-negative, aerobic, non-motile, coccoid, ovoid or rod-shaped, and orange-pigmented bacterial strain, designated WS2-14T, was isolated from sediment collected from a sea cucumber culture pond located in Rongcheng, Shandong province, PR China (122° 14' E, 36° 54' N). Strain WS2-14T grew optimally at 28 °C and pH 7.0-7.5, and was able to tolerate salt concentrations of 0.5-6.0 % (w/v) NaCl. Strain WS2-14T was characterized chemotaxonomically as possessing menaquinone-6 (MK-6) as the major respiratory quinone, as well as iso-C13 : 0, iso-C15 : 0 3-OH and iso-C15 : 0 as the predominant fatty acids. The DNA G+C content of strain WS2-14T was 31.2 mol%. The major polar lipids were phosphatidylethanolamine, one unidentified phospholipid, one unidentified aminolipid and three unidentified lipids. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain WS2-14T was phylogenetically related to members of the genus Polaribacter and was closely related to Polaribacter haliotis, Polaribacter atrinae and Polaribacter sejongensis with 97.7, 97.4 and 97.0 % sequence similarities, respectively. On the basis of its phenotypic and chemotaxonomic properties, as well as phylogenetic analyses, strain WS2-14T was considered to represent a novel species of the genus Polaribacter, for which the name Polaribactertangerinus sp. nov. is proposed. The type strain is WS2-14T (=KCTC 52275T=MCCC 1H00163T).

Effect of tea saponin on ephyrae and polyps of the moon jellyfish Aurelia sp.1.

The moon jellyfish (Aurelia sp.1) is thought to be a nuisance for the sea cucumber aquaculture, which commonly occur in the sea cucumber (Apostichopus japonicus) culture ponds of the Yellow Sea, China. To develop an appropriate method to control Aurelia sp.1 blooms, the toxic effects of tea saponin on Aurelia sp.1 ephyrae and polyps were tested in laboratory experiments. Our results revealed that tea saponin caused significant morphological changes, behavioral abnormality and mortality in Aurelia sp.1 ephyrae and polyps in 24 h and 48 h exposure experiments. The 24 h and 48 h median lethal concentrations (LC50) values of tea saponin for Aurelia sp.1 ephyrae were 1.9 and 1.1 mg L-1 respectively, while the LC50 value for Aurelia sp.1 polyps was 0.4 mg L-1 after 24h and 48 h of exposure to tea saponin. Comparison with literature results of tea saponin on A. japonicus indicates that the resistance of A. japonicus to tea saponin is 12–18 times greater than that of Aurelia sp.1 ephyrae. Therefore, the appropriate tea saponin dosage for the control of Aurelia sp.1 should be paid enough attention in order to minimize possible damage for sea cucumber. We suggest that the recommended level of tea saponin to eradicate Aurelia sp.1 ephyrae and polyps in sea cucumber culture ponds be lower than 1.35 mg L-1.

Aquimarina rubra sp. nov., isolated from sediment of a sea cucumber culture pond.

A Gram-stain-negative, non-motile, rod-shaped, red-pigmented, facultatively anaerobic bacterium, designated SS2-9T, was isolated from sediment collected from a sea cucumber culture pond located in Rongcheng, Shandong province, China. Cells of strain SS2-9T were approximately 0.3-0.5 µm in width and 1.5-6.0 µm in length. The strain was able to grow at 10-37 °C, at pH 6.5-8.5 and in the presence of 0.5-6.0 % (w/v) NaCl. It grew optimally at 28 °C and in the presence of 2.0 % (w/v) NaCl. The DNA G+C content was 34.5 mol% and the sole respiratory quinone was menaquinone 6 (MK-6). The predominant cellular fatty acids were C15 : 0, iso-C15 : 1 G, iso-C15 : 0 and iso-C17 : 0 3-OH. The major polar lipids were phosphatidylethanolamine, an unidentified phospholipid, two unidentified aminolipids and four unidentified lipids. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain SS2-9T was phylogenetically related to members of the genus Aquimarina and was closely related to Aquimarina amphilecti 92VT (97.29 % similarity). On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain SS2-9T was considered to represent a novel species of the genus Aquimarina, for which the name Aquimarina rubra sp. nov. is proposed. The type strain is SS2-9T (=KCTC 52274T=MCCC 1H00142T).

Succession and seasonal variation in epilithic biofilms on artificial reefs in culture waters of the sea cucumber Apostichopus japonicus

Periphytic biofilms in aquaculture waters are thought to improve water quality, provide an additional food source, and improve the survival and growth of some reared animals. In the Asia- Pacific region, particularly in China, artificial reefs are commonly used in the commercial farming of sea cucumbers. However, few studies have examined the epilithic biofilms on the artificial reefs. To gain a better understanding of the succession of epilithic biofilms and their ecological processes in sea cucumber culture waters, two experiments were conducted in culture waters of the sea cucumber Apostichopus japonicus in Rongcheng, China, using artificial test panels. On the test panels of succession experiment, more than 67 species were identified in the biofilms. On the test panels of seasonal variation experiment, more than 46 species were recorded in the biofilms. In both experiments, communities of epilithic biofilms were dominated by diatoms, green algae and the annelid Spirorbis sp. In the initial colonization, the dominant diatoms were Cocconeis sp., Amphora spp. and Nitzschia closterium in June, which were succeeded by species of Navicula, Cocconeis and Nitzschia (July to September), and then by Licmophora abbreviata, Nitzschia closterium and Synedra spp. in the following months. A diatom bloom in the autumn and filamentous green algae burst in the summer were also observed. Ecological indices well annotated the succession and seasonal changes in epilithic communities. Multidimensional scaling (MDS) analysis found significant differences in diatom community composition among months and seasons. Fast growth of biofilms was observed in the summer and autumn, whereas the biomass of summer biofilms was largely made up of filamentous green algae. Present results show that the components of epilithic biofilms are mostly optimal foods of A. japonicus, suggesting that biofilms on artificial reefs may contribute important nutritional sources for sea cucumbers during their growth seasons. Future works should include quantitative determination of the contribution of epilithic biofilms to the diet of A. japonicus, potential roles of epilithic biofilms in regulating the water quality of sea cucumber ponds, and the regulation of epilithic biofilms in sea cucumber culture ponds.

Kordiimonas sediminis sp. nov., isolated from a sea cucumber culture pond

A marine bacterium, designated strain N39(T), was isolated from a sediment sample collected at a sea cucumber culture pond in Weihai, China. Cells of strain N39(T) were observed to be Gram-stain negative, facultatively anaerobic, motile rods showing catalase and oxidase negative reactions. Strain N39(T) was found to grow optimally at pH 8.0-8.5, 35-37°C and in the presence of approximately 3.0% (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain N39(T) belongs to the genus Kordiimonas in the family Kordiimonadaceae, appearing closely related to Kordiimonas lacus JCM 16261(T) (95.9%), Kordiimonas aquimaris MEBiC06554(T) (95.1%), Kordiimonas gwangyangensis JCM 12864(T) (94.2%) and Kordiimonas aestuarii 101-1(T) (93.8%). Ubiquinone 10 (Q-10) was found to be the major respiratory quinone. The dominant cellular fatty acids were identified as iso-C17:1 ω9c, iso-C17:0, iso-C15:0 and C17:1 ω6c. The predominant polar lipids were found to be phosphatidylglycerol, phosphatidylethanolamine and diphosphatidylglycerol. The DNA G+C content of strain N39(T) is 50.8%. On the basis of genotypic, chemotaxonomic and phenotypic data, strain N39(T) is concluded to represent a novel species within the genus Kordiimonas, for which the name Kordiimonas sediminis sp. nov. is proposed. The type strain is N39(T) (=KCTC 42590(T)=MCCC 1H00112(T)).