Characteristics of plant trait network and its influencing factors in impounded lakes and channel rivers of South-to-North Water Transfer Project, China.

Trait-based approaches have been widely used to evaluate the effects of variable environments on submerged macrophytes communities. However, little research focused on the response of submerged macrophytes to variable environmental factors in impounded lakes and channel rivers of water transfer project, especially from a whole plant trait network (PTN) perspective. Here, we conducted a field survey designed to clarify the characteristic of PTN topology among impounded lakes and channel rivers of the East Route of South-to-North Water Transfer Project (ERSNWTP) and to unravel the effects of determining factors on the PTN topology structure. Overall, our results showed that leaf-related traits and organ mass allocation traits were the hub traits of PTNs in impounded lakes and channel rivers of the ERSNWTP, which traits with high variability were more likely to be the hub traits. Moreover, PTNs showed different structures among impounded lakes and channel rivers, and PTNs topologies were related to the mean functional variation coefficients of lakes and channel rivers. Specially, higher mean functional variation coefficients represented tight PTN, and lower mean functional variation coefficients indicated loose PTN. The PTN structure was significantly affected by water total phosphorus and dissolved oxygen. Edge density increased, while average path length decreased with increasing total phosphorus. Edge density and average clustering coefficient showed significant decreases with increasing dissolved oxygen, while average path length and modularity exhibited significant increases with increasing dissolved oxygen. This study explores the changing patterns and determinants of trait networks along environmental gradients to improve our understanding of ecological rules regulating trait correlations.

Comparative Mitogenomics of Two Sympatric Catfishes of Exostoma (Siluriformes: Sisoridae) from the Lower Yarlung Tsangpo River and Its Application for Phylogenetic Consideration.

The genus Exostoma is a group of stenotopic and rheophilic glyptosternine catfishes distributed in South and Southeast Asia. So far, comprehensive studies on mitogenomics referring to this genus are very scarce. In this study, we first sequenced and annotated the complete mitochondrial genomes of Exostoma tibetanum and Exostoma tenuicaudatum-two sympatric congeners from the lower Yarlung Tsangpo River, Tibet, China. The mitogenomes of both species contained 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, one light-strand origin of replication, and one control region, with lengths of 16,528 bp and 16,533 bp, respectively. The mitogenome architecture, nucleotide composition, and codon usage of protein-coding genes were almost identical between the two Exostoma species, although some estimated parameters varied. Phylogenetic analysis strongly supported the monophyly of Exostoma in the subfamily Glyptosternae, and Exostoma tibetanum had the closest relationship to Exostoma tenuicaudatum. The divergence time estimation demonstrated that these two species diverged approximately 1.51 Ma during the early Pleistocene, which was speculated to be triggered by the river system changes caused by the uplift of the southeastern Tibetan Plateau. Selection pressure analyses indicated that all protein-coding genes of Exostoma species underwent a strong purifying selection, while minority positive sites from NADH dehydrogenase complex genes were detected. These findings are expected to promote our understanding of the molecular phylogeny of the genus Exostoma and provide valuable mitogenomic resources for the subfamily Glyptosternae.

How does turions production of Potamogeton crispus L. respond to parental population biomass and living environment.

Turions production is the dominant means of propagation in Potamogeton crispus L. To understand how parental population and their living environmental factors influence the turions production of P. crispus L., a field research was conducted in Nansi Lake in Yellow River Flood Plain and southwestern Shandong Province, China. This study showed that P. crispus biomass and asexual turions showed an almost uniform spatial distribution pattern. Water depth, attenuation coefficient of light, sediment water content, sediment organic matter content, and pH were significantly related to P. crispus biomass, turions weight, and turions number. Single turion weight was determined only by P. crispus biomass, while turions number was simultaneously determined by P. crispus biomass and sediment water content. Turions weight mainly depended on turions number rather than single turion weight, and maternal biomass and sediment water content determined turions weight by affected turions number rather than single turion weight.

Effects of benthivorous fish disturbance on chlorophyll a contents in water and the growth of two submersed macrophytes with different growth forms under two light regimes.

Low underwater light availability and benthivorous fish-mediated disturbance are two important factors that influence the growth of submersed macrophytes. However, the combined effects of these factors remain unclear. To determine the combined effects of low light and fish-mediated disturbance on the growth of two submersed macrophytes with contrasting growth forms, i.e., Vallisneria natans and Hydrilla verticillata, we conducted an outdoor mesocosm experiment with a two-by-two factorial design. The experiment involved two fish-mediated disturbance levels (0 and 1 Misgurnus anguillicaudatus) crossed with two levels of light intensity (ambient light and a low-light environment created by culturing the macrophytes under a shelter). The results showed that the chlorophyll a (chl a) concentration in the overlying water showed no difference among treatments for each macrophyte species. The fish-mediated disturbance significantly decreased the relative growth rate (RGR) of both species in the low-light environment but showed no effects in the ambient light environment. Low light availability and/or fish-mediated disturbance led to increased plant heights of both species compared with the heights under the ambient light regime. Low light availability combined with fish-mediated disturbance significantly reduced the ramet number and soluble carbohydrate (SC) content of both species; however, the free amino acid (FAA) content was not affected. Compared to V. natans, H. verticillata exhibited a high RGR and high ramet numbers in a low-light environment combined with fish-mediated disturbance. Our results indicated that the adaptability of H. verticillata is better than that of V. natans in turbid, shallow and hydrostatic water. Fish-mediated disturbance can negatively influence submersed macrophyte recovery in lakes when light is not abundant.

Preparation of Chitosan/Alginate-ellagic Acid Sustained-release Microspheres and their Inhibition of Preadipocyte Adipogenic Differentiation.

OBJECTIVE: In this study, chitosan/alginate-ellagic acid sustained-release microspheres were prepared, and the effect of sustained-release microspheres on preadipocyte adipogenic differentiation was analyzed. METHODS: Chitosan/alginate-ellagic acid microspheres were prepared and identified by scanning electron microscopy (SEM) and infrared spectroscopy (IR). The drug release rates were measured at pH 6.8, 7.0, 7.2, 7.4 to determine sustained release of ellagic acid from microspheres. The effects of 0.1, 1, 10 mg/L chitosan/alginate-ellagic acid microsphere on 3T3-F442A preadipocyte proliferation were determined by Methyl thiazolyl tetrazolium assay (MTT), and cell morphology was checked by hematoxylin/ eosin staining (HE staining). The effect of chitosan/alginate-ellagic acid microspheres on preadipocyte adipogenic differentiation was also determined by Oil red O staining, and lipogenesis was measured by isopropanol extraction. The molecular mechanism was investigated by detecting the mRNA expression of CCAAT/enhancer binding protein alpha (C/EBPα) and peroxisome proliferatorsactivated receptor gamma (PPARγ). RESULTS: Chitosan/alginate-ellagic acid sustained-release microspheres were successfully prepared, and the inhibition of proliferation and adipogenic differentiation of preadipocytes was found to be dosedependent. The mechanism of differentiation inhibition was found to be closely related to the expression of transcription factor C/EBPα and PPARγ. CONCLUSION: Chitosan/alginate can be used as a good material to prepare ellagic acid sustained-release microspheres, and these microspheres can be used for treating the obesity.

Littoral Slope, Water Depth and Alternative Response Strategies to Light Attenuation Shape the Distribution of Submerged Macrophytes in a Mesotrophic Lake.

Light is a major limiting resource in aquatic ecosystems and numerous studies have investigated the response of submerged macrophytes to low light conditions. However, few studies have tested whether different light response strategies can also have consequences for macrophyte distribution along different littoral slopes in lakes, which are known to affect macrophyte biomass due to differences in drag forces and sediment characteristic. In this study, we tested (1) whether two macrophyte species of different growth forms (canopy-forming: Potamogeton maackianus, rosette-type: Vallisneria natans) differ in their response strategies to low light conditions and (2) how these responses influence their distribution along different basin slopes in the mesotrophic Lake Erhai, China. We hypothesized that the canopy-forming species responds to low light conditions at deeper sites by stem elongation while the rosette-type species increases its shoot chlorophyll content. As a consequence, P. maackianus should have a higher susceptibility to drag forces and thus prevail at sites with lower slopes. Sites with higher slopes should offer a niche for rosette-type species like V. natans that can better withstand drag forces. We surveyed the distribution and abundance of the two macrophyte species at 527 sampling points along 97 transects in Lake Erhai and measured their height, leaf and stem/rhizome biomass, and leaf chlorophyll a content at different water depths. Our results confirmed stem elongation as a strategy to low light conditions by the canopy-forming species P. maackianus, while V. natans produced more chlorophyll a per shoot biomass at deeper sites to tolerate shading. As hypothesized, these alternative response strategies to low light conditions resulted in a trade-off regarding the plants ability to grow at different basin slopes. P. maackianus was dominant at sites with low-moderate slope (0-4%) and low-moderate water depth (2-4 m), while sites with high basin slope (4-7%) combined with moderate-high water depth (3-5 m) were dominantly colonized by V. natans. The latter habitat thus represents a potential refuge for rosette-type macrophyte species that are often outcompeted when shading increases during eutrophication.

Seed Germination Indicates Adaptive Transgenerational Plasticity in a Submerged Macrophyte.

Adaptive transgenerational plasticity is an important evolutionary strategy in plants. We investigated the resource allocation strategy in sexual reproduction and performed an in situ seed germination experiment of Potamogeton maackianus to reveal their responses to different water depths. Later, we discussed the biased adaptability to the maternal habitat in this species. We found a positive correlation between sexual and asexual reproduction in water depths from 1.0 m to 3.0 m, such a correlation failed to occur in 4.0 m water depth. These results indicate that the trade-off between sexual and asexual reproduction should only be expected in a stressful habitat, where resource acquisition is limited. For trade-off between quantity and quality of sexual units in different water depths, P. maackianus tends to produce more but lower quality sexual reproductive units in shallow water, and fewer but higher quality sexual units are found in deep water. The total germination percentage of seeds of P. maackianus was relatively poor, less than 46.65% in all of the treatments. The maximum germination percentage of seeds from 1.0 m, 2.0 m, 3.0 m, and 4.0 m water depths are 14.4%, 17.75%, 25.51%, and 46.65%, respectively. Seeds with higher germination percentage were from deeper water depths. The most interesting result was that the maximum final germination percentage occurred only when treatment water depth was the same as collection water depth. Our result showed that the variations in germination characters of the studied species appear to be based partly on the effects of maternal environmental factors. Our findings proved the adaptive transgenerational plasticity in P. maackianus, which will play an important role in evolutionary response to the selection of water depths.

Root-foraging behavior ensures the integrated growth of Vallisneria natans in heterogeneous sediments.

The present study was carried out to determine the efficacy of root foraging and the physiological response of Vallisnaria natans grown in heterogeneous sediments. V. natans was cultivated in two homogeneous and two heterogeneous sediments. The results suggested that V. natans grown in heterogeneous sediments presented a significantly higher root proportion in its total biomass, exhibited root foraging, and grew well, as indicated by a total biomass, ramet number, and plant height very close to those of plants grown in nutrient-rich clay sediment. Moreover, the more sensitive physiological response of the roots than the stems or the leaves to sediment nutrients suggested that root foraging occurred, and the approached values between the two heterogeneous sediments and the homogeneous clay sediment indicated that V. natans could satisfy its nutrient requirements via root foraging. The results may be useful in the recovery of macrophytes that remodel part (rather than all) of the substrate and can potentially improve habitats that are unsuitable for plant growth.

Eutrophication strengthens the response of zooplankton to temperature changes in a high-altitude lake.

To assess whether and how zooplankton communities respond to variations in temperature and how these assemblages change with eutrophication, we performed a large-scale, monthly survey from August 2011 to July 2012 to determine the seasonal and spatial variations in these communities in a high-altitude lake. A detrended correspondence analysis and a path analysis demonstrated that temperature and chlorophyll a were important factors influencing zooplankton. The path diagram showed that Daphnia was negatively affected directly by chlorophyll a and indirectly by temperature, whereas Bosmina was directly and positively affected by temperature. Daphnia spp. decreased in both absolute and relative biomass during warm seasons, whereas Bosmina spp. showed the opposite trend. Moreover, the lowest Daphnia spp. biomass was observed in the southern region, which was the most eutrophic. Our results indicate that increasing temperatures will continue to shift the dominant genus from Daphnia to Bosmina, and this change will be exacerbated by eutrophication. In addition, the zooplankton of Lake Erhai have shifted to smaller species over time as temperature and eutrophication have increased, which implies that zooplankton succession to small cladocerans may be markedly accelerated under further climate change and the increased eutrophication that has been observed in recent decades.