Spring Communities Research Articles

A modification of the leaf-nets method for sampling benthic invertebrates in spring habitats

<p>The full ecological potential of spring habitats remains relatively unexplored mostly because of the lack of standardized sampling procedures and difficulties to collect representative biological samples, especially in small-sized springs. Recent studies on sampling methodologies in spring habitats indicated that a modified Surber net with a reduced frame area, reliably describes the structure and composition of spring communities. This method, however, is very invasive and may severely impact the spring, especially when a large number of samples is required. The paper presents a new quantitative method (leaf-nets) for sampling crenic invertebrates which combines a rather high efficiency with negligible impacts on spring habitat structure and biota. The effectiveness of the new methodology was tested in a medium-size rheocrene spring in Central Apennine, where spring assemblages were sampled in parallel with a modified Surber net and with the new method. Taxa richness and density were higher in the Surber net, while no between-method differences were recorded for the number of insect taxa and Simpson diversity. Furthermore, the overall functional organization of Surber net and leaf-nets assemblages was very similar. The new method sampled only 25% of the individuals cumulatively collected, but 75% of the total richness, with a good representation of the structure and the functional organization of spring assemblages. In comparison with the Surber net, the negligible loss of information of the new method is highly compensated by its minor invasivity, lower impacts on spring microhabitats and invertebrate populations and by its higher versatility. Leaf-nets could also be used to assess leaf-detritus breakdown in springs, thus allowing a better ecological characterization of these ecosystems. </p><p> </p>

Responses of phytoplankton functional groups to environmental factors in the Maixi River, southwest China

<p>The functional groups approach is an efficient way to analyze seasonal changes in phytoplankton biomass as it is based on the physiological, morphological, and ecological attributes of the species. In this study, we identified the functional groups and driving factors behind short-term succession in phytoplankton communities. We analyzed physical, chemical, and biological factors of the Maixi River in Baihua Reservoir (BHR) from August to September, 2013 (summer, phase I) and March to May, 2014 (late spring and early summer, phase II). The 226 samples collected were divided into 23 functional groups. In phase I, phytoplankton biomass ranged from 4.88 to 30.59 mg·L<sup>-1</sup>, and the group S1 (<em>Pseudanabaena limnetica</em>) had the greatest biomass. In phase II, phytoplankton biomass ranged from 2.22 to 50.61 mg·L<sup>-1</sup>, and groups Y (<em>Cryptomonas</em> sp.) and S1 (<em>P. limnetica</em>) had the greatest biomass. Dominant functional groups in the Maixi River changed from S1 + D + Y + Lo in phase I to Y + S1 in summer. Changes in the phytoplankton community varied between 0 and 0.144 day<sup>-1 </sup>in phase I and between 0.008 and 0.389 day<sup>-1 </sup>in later spring and early summer. This showed a steady-state phytoplankton community during the two phases, in which the functional groups S1 (<em>P. limnetica</em>) and Y (<em>Cryptomonas</em> sp.) were dominant.<em> Pseudanabaena limnetica</em>, <em>Synedra </em>sp., <em>Peridinium </em>sp., and<em> Cryptomonas</em> sp. were dominant during summer, contributing to 70% of the total biomass in the steady-state community, and<em> P. limnetica</em>,<em> Synedra </em>sp., <em>Cryptomonas</em> sp.,<em> </em>and <em>Chlamydomonas</em> sp. were dominant during later spring and early summer, contributing to 60% of the total biomass in the community. Groups S1, D, and Y formed easily in the Maixi River, but <em>P. limnetica</em> was the dominant species in the eutrophic conditions of the Maixi River. According to biotic and abiotic factors, we concluded that the Maixi River is hypertrophic, and water resource management should take blooms of <em>P. limnetica</em> occurring in May into account. Temperature and dissolved oxygen were the critical factors affecting the steady-state of the phytoplankton community in late spring and early summer and summer, respectively. Because the Maixi River is an important source in the BHR, its phytoplankton functional groups directly affect the ecological balance of the water environment.</p>

Effects of prescribed fire on germination and plant community of Carex cinerascens and Artemisia selengensis in Poyang Lake, China

As an important freshwater lake and wetland area with international significance in biodiversity conservation, Poyang Lake is facing increasing pressure from human activities, including prescribed fire. In the present study, two representative wetland plants from Poyang Lake (Carex cinerascens and Artemisia selengensis) were selected to determine their in situ regeneration success following a prescribed winter fire. Monitoring of plant growth and species composition was carried out monthly for one year following burn treatments. Results showed that significantly higher densities of both C. cinerascens and A. selengensis were observed in the spring. Moreover, the prescribed fire had little influence on the aboveground and belowground biomasses of C. cinerascens, whereas a significant effect on A. selengensis was observed. A smaller difference in dominance values of constructive species was detected between burned and unburned plots. However, a significant increase in biodiversity was found within the burned A. selengensis community in spring. In addition, there was little difference in plant traits and community characters found between burned and unburned plots after the flooding season. Our findings suggest that the water regime is the main driving factor in regulating the ecological process of Poyang Lake, and a single prescribed fire was not sufficient to change the plant community structure, although it did have a significant influence on biomass and species composition in the season following the fire.

Пространственно-типологическая структура и организация весеннего и весенне-летнего населения птиц северного макросклона Киргизского хребта (Тянь-Шань)

Пространственно-типологическая структура и организация весеннего и весенне-летнего населения птиц северного макросклона Киргизского хребта (Тянь-Шань)

Implications of piscine predator control on the federally listed fountain darter

AbstractOne strategy for protecting the federally listed fountain darter, Etheostoma fonticola (Jordan & Gilbert), during low flow conditions is the removal of piscine carnivores [in this case, largemouth bass, Micropterus salmoides (Lacepède)]. However, headwater spring communities of the Comal and San Marcos rivers include another potential predator [red swamp crayfish, Procambarus clarkii (Girard)]. Removal of piscine carnivores could produce cascading effects by increasing crayfish consumption of benthic fish. The purpose of this study was to evaluate if piscine carnivore removal will lessen predatory pressure or induce a trophic cascade with crayfish increasing and causing declines in fountain darter. The numbers of fountain darter consumed were quantified among three predator treatments (red swamp crayfish only, largemouth bass only and red swamp crayfish and largemouth bass combined) and vegetation treatments (vegetated and non‐vegetated) at three temperature regimes (18, 22, 27°C). Vegetation had no effect on fountain darter predation. Among temperature trials, largemouth bass only and red swamp crayfish and largemouth bass combined consumed similar numbers of fountain darter, and red swamp crayfish only consumed the least numbers of fountain darter, except at 22°C. Largemouth bass did not consume more red swamp crayfish than fountain darter. Therefore, largemouth bass removal appears to be a viable option for reducing fountain darter predation during periods of low flow.

Earthquake-Related Changes in Species Spatial Niche Overlaps in Spring Communities

Species interactions between stygobites (obligate groundwater organisms) are poorly known, reflecting the difficulty in studying such organisms in their natural environments. Some insight can be gained from the study of the spatial variability in microcrustacean communities in groundwater-fed springs. Earthquakes can increase hydraulic conductivity in the recharge area of karstic aquifers and flow rates in discharge zones, thus dislodging stygobites from their original habitats to the spring outlets. Earthquakes are expected to alter species spatial niche overlap at the spring outlets, where stygobites coexist with non-stygobites living in benthic and subsurface habitats. We compared the abundance of stygobiotic and non-stygobiotic microcrustaceans in groundwater-fed springs before and after the 6.3-Mw earthquake that hit the karstic Gran Sasso Aquifer (Italy) in 2009. Pre-seismic (1997, 2005) overall niche overlaps were not different from null expectations, while post-seismic (2012) species mean niche overlaps were higher, following the redistribution of animals caused by the earthquake-triggered discharge. The reduced abundance of stygobites following their dislodgement from the aquifer and the concomitant displacement of non-stygobites led to a higher post-seismic co-occurrence of stygobites and non-stygobites. Changes in aquifer structure destroyed pre-seismic species segregation patterns by creating new or strengthening already existing interactions.

黄河口邻近海域浮游动物群落时空变化特征

PDF HTML阅读 XML下载 导出引用 引用提醒 黄河口邻近海域浮游动物群落时空变化特征 DOI: 10.5846/stxb201507291595 作者: 作者单位: 中科院烟台海岸带研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 中国科学院战略性先导科技专项（XDA11020405，XDA05130703）；国家自然科学基金项目（41206086） Spatial and seasonal variability of the zooplankton community in the Yellow River Estuary's adjacent sea Author: Affiliation: antai Institute of Coastal Zone Research, Chinese Academy of Sciences Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用2012年12月-2013年9月4个季度的现场调查资料研究了黄河口邻近海域浮游动物群落的时空分布特征。研究表明，黄河口邻近海域共鉴定出浮游动物70种，包括浮游幼虫19类。浮游动物优势种主要由夜光虫（Noctiluca scintillans）、小拟哲水蚤（Paracalanus parvus）、双刺纺锤水蚤（Acartia bifilosa）、拟长腹剑水蚤（Oithona similis）、强额拟哲水蚤（Paracalanus crassirostris）、近缘大眼剑水蚤（Corycaeus affinis）、强壮箭虫（Sagitta crassa）、双壳类幼体（Bivalvia larvae）、多毛类幼体（Polychaeta larvae）等种类。黄河口邻近海域浮游动物丰度夏季最高（60620个/m3），春季（31228个/m3）和秋季（21540个/m3）次之，冬季最低（7594个/m3）。不同季节浮游动物丰度的空间分布具有差异性，春季浮游动物丰度呈现出从近岸到外海降低的趋势；夏季浮游动物形成两个高丰度区，分别位于河口邻近海区和河口东部海区；秋季和冬季浮游动物丰度高值区均位于河口东部海区。浮游动物生物多样性指数均呈现从河口到外海升高的趋势，低值区位于黄河口入海口附近海区。相关性分析显示，黄河口邻近海域浮游动物丰度与海水温度显著正相关（r=0.212，P < 0.05），表明温度为影响黄河口邻近海域浮游动物丰度变化的主要因素。 Abstract:The unusual dynamic conditions in estuaries cause their zooplankton distribution, as well as the zooplankton distribution in the adjacent sea, to be spatially and temporally heterogeneous. To investigate this heterogeneity in the adjacent sea of the Yellow River Estuary, zooplankton samples were collected from there in December 2012, April 2013, June 2013, and September 2013. The samples were collected using a plankton net with mesh size 0.160 mm, while during the four cruises, environmental parameters such as seawater temperature, salinity, and chlorophyll a concentration were determined. Spearman rank correlations were used to analyze the relationship between zooplankton abundance and various environmental factors. Overall, 70 zooplankton species were identified, including 19 pelagic larvae. The copepods were the most abundant group, representing 30%, followed by hydromedusae. For the study region, the most dominant organisms were Noctiluca scintillans, Paracalanus parvus, Acartia bifilosa, Oithona similis, Paracalanus crassirostris, Corycaeus affinis, Sagitta crassa, Bivalvia larvae, and Polychaeta larvae. Among these, P. parvus, A. bifilosa, and O. similis dominated the zooplankton communities for three of the measured seasons. Furthermore, the composition of dominant species varied with seasons, with the seasonal turnover rate of dominant zooplankton species being high (67%-88%). The abundance of P. parvus averaged 9320 ind/m3 in summer, 3704 ind/m3 in autumn, 3891 ind/m3 in winter, and 165 ind/m3 in spring. For the Yellow River mouth, P. parvus reached the greatest abundance in summer, while for the eastern sea area, this occurred in autumn and winter. Furthermore, the abundance of A. bifilosa averaged 40218 ind/m3 in summer, 17815 ind/m3 in spring, and 2127 ind/m3 in winter. In spring, the abundance of A. bifilosa showed a decreasing trend from the Yellow River mouth to the outer sea area. For the Yellow River mouth, this species reached its highest abundance in summer, whereas for the eastern sea area, this occurred in winter. In addition, the abundance of O. similis averaged 4245 ind/m3 in summer, 2776 ind/m3 in spring, 1154 ind/m3 in winter, and 88 ind/m3 in autumn. In spring, O. similis reached the highest abundance in the both sides of the Yellow River mouth, while for the Yellow River mouth this occurred in summer and for the eastern sea area in winter. N. scintillans dominated the zooplankton community in spring and summer. The abundance of N. scintillans averaged 28194 ind/m3 in spring and 13679 ind/m3 in autumn. In spring, N. scintillans reached the highest abundance in the southern area of the Yellow River mouth, whereas for the eastern sea area, this occurred in autumn. Overall zooplankton abundance averaged 60620 ind/m3 in summer, 31228 ind/m3 in spring, 21540 ind/m3 in autumn, and 7594 ind/m3 in winter, while its spatial distribution varied among the four seasons. In spring, zooplankton abundance showed a decreasing trend from the Yellow River mouth to the outer sea area. In summer, zooplankton density was higher in the Yellow River mouth and the eastern sea area. The higher zooplankton abundance occurred in the eastern sea area in autumn and winter. The zooplankton community's diversity index (H') showed an increasing trend from the Yellow River mouth to the outer sea area. Finally, the zooplankton abundance had a clear positive correlation with the seawater temperature (r=0.212, P < 0.05), suggesting that for the Yellow River Estuary, seawater temperature was one of the main factors determining zooplankton abundance. 参考文献 相似文献 引证文献

Bioassessment of Four Karst Springs at Hobbs State Park – Conservation Area with a Focus on Diving Beetle (Dytiscidae: Hydroporinae) Species of Concern

Four springs were surveyed at Hobbs State Park-Conservation Area to provide an initial bioassessment and to determine occurrences of two endemic predaceous diving beetles of concern, Heterosternuta sulphuria and Sanfilippodytes sp. Habitat in the four spring runs were dominated by bedrock and gravel substrate with heavy accumulations of leaf litter. Thirty-three taxa representing 11 orders were collected from the four springs. Non-insect taxa included Oligochaeta, Physidae, and Isopoda, and predominant insect orders included Ephemeroptera, Coleoptera, Diptera, and Trichoptera. The total number of taxa across springs ranged from seven to 19, with total abundances ranging from 39 to 86 individuals. No individual taxon occurred across all four springs. Percent tolerant organisms and the Hilsenhoff Biotic Index showed that spring communities were dominated by taxa tolerant to organic pollution, likely because of low flows and heavy accumulations of leaves. Predators were the dominant functional group followed by shredders. The endemic, predaceous diving beetle Heterosternuta sulphuria was collected from two springs and Sanfilippodytes sp. was collected from three springs. One spring contained the largest number of Sanfilippodytes sp. individuals recorded among all other aquatic habitats surveyed to date. Findings highlight the importance of spring systems at Hobbs State Park Conservation Area for endemic-species conservation, while information on the invertebrate community provides a baseline for future monitoring and comparison.

Microbial diversity and autotrophic activity in Kamchatka hot springs.

Microbial communities of Kamchatka Peninsula terrestrial hot springs were studied using molecular, radioisotopic and cultural approaches. Analysis of 16S rRNA gene fragments performed by means of high-throughput sequencing revealed that aerobic autotrophic sulfur-oxidizing bacteria of the genus Sulfurihydrogenibium (phylum Aquificae) dominated in a majority of streamers. Another widely distributed and abundant group was that of anaerobic bacteria of the genus Caldimicrobium (phylum Thermodesulfobacteria). Archaea of the genus Vulcanisaeta were abundant in a high-temperature, slightly acidic hot spring, where they were accompanied by numerous Nanoarchaeota, while the domination of uncultured Thermoplasmataceae A10 was characteristic for moderately thermophilic acidic habitats. The highest rates of inorganic carbon assimilation determined by the in situ incubation of samples in the presence of 14C-labeled bicarbonate were found in oxygen-dependent streamers; in two sediment samples taken from the hottest springs this process, though much weaker, was found to be not dependent on oxygen. The isolation of anaerobic lithoautotrophic prokaryotes from Kamchatka hot springs revealed a wide distribution of the ability for sulfur disproportionation, a new lithoautotrophic process capable to fuel autonomous anaerobic ecosystems.

COMPARATIVE ANALYSIS OF EPILITHIC DIATOM ASSEMBLAGES OF SPRINGS AND STREAMS IN THE KONJUH MOUNTAIN (BOSNIA AND HERZEGOVINA)

UDK: 574.587:582.26/.27(234.422 Konjuh)&#x0D; Springs are recognized as hotspots for freshwater biodiversity conservation. The study objective was to analyze and compare the biodiversity of epilithic diatom communities of spring and stream habitats in the Konjuh Mountain (B&amp;H). The measuring of basic water physical and chemical parameters and diatom sampling were carried out during summer and autumn period in 2013.&#x0D; Diatom assemblages were collected from 10 locations: (i) five locations were placed in small mountain springs that flow into headwater streams, where another 5 localities were placed. Diatoms were collected by scrubbing the rocks using standard methodology. Relative diatom cell abundances were established by counting up to 400 frustules on permanent slides prepared in Naphrax.&#x0D; Spring habitats were more diverse in diatoms (H' loge =1.67 average) in comparison with headwater stream habitats (H' loge=1.15 average), which was confirmed by t-test (t=2.79; p=0.013). The similarities of community structure from different habitats were investigated by non-metric multidimensional scaling, on the Bray-Curtis similarity matrix in software package Primer 6.&#x0D; Using Permutational Manova test, a different diatom composition was proved between spring and stream communities (Pseudo F=2.66, p=0.012), while the seasonal difference in the community structure was not confirmed (F=0.586, p=0.876). The most abundant and frequent species in spring habitats were: Achnanthidium minutissimum (Kützing) Czarnecki, Cocconeis pseudolineata (Geitler) Lange-Bertalot, Gomphonema pumilum var. elegans E.Reichardt &amp; Lange-Bertalot, Meridion circulare (Greville) C.Agardh and Planothidium lanceolatum (Brébisson ex Kützing) Lange-Bertalot. The most frequent and abundant species in headwater stream habitats were: Achnanthidium minutissimum (Kützing) Czarnecki, Cocconeis placentula var. euglypta (Ehrenberg) Grunow, Cocconeis placentula var. lineata (Ehrenberg) van Heurck and Cymbella tridentina Lange-Bertalot, M.Cantonati &amp; A.Scalfi.&#x0D; In comparison with streams habitats, the springs are heterogeneous with specific diatom composition due to more stable water flow. Although the springs cover very small areas, the diversity of species that inhabit them must not be neglected in planning the use of these natural resources.

The Shifts of Diazotrophic Communities in Spring and Summer Associated with Coral Galaxea astreata, Pavona decussata, and Porites lutea.

The coral holobiont often resides in oligotrophic waters; both coral cells and their symbiotic dinoflagellates possess ammonium assimilation enzymes and potentially benefit from the nitrogen fixation of coral-associated diazotrophs. However, the seasonal dynamics of coral-associated diazotrophs are not well characterized. Here, the seasonal variations of diazotrophic communities associated with three corals, Galaxea astreata, Pavona decussata, and Porites lutea, were studied using nifH gene amplicon pyrosequencing techniques. Our results revealed a great diversity of coral-associated diazotrophs. nifH sequences related to Alphaproteobacteria, Deltaproteobacteria, and Gammaproteobacteria were ubiquitous and dominant in all corals in two seasons. In contrast with the coral P. decussata, both G. astreata and P. lutea showed significant seasonal changes in the diazotrophic communities and nifH gene abundance. Variable diazotroph groups accounted for a range from 11 to 49% within individual coral samples. Most of the variable diazotrophic groups from P. decussata were species-specific, however, the majority of overlapping variable groups in G. astreata and P. lutea showed the same seasonal variation characteristics. Rhodopseudomonas palustris- and Gluconacetobacter diazotrophicus-affiliated sequences were relatively abundant in the summer, whereas a nifH sequence related to Halorhodospira halophila was relatively abundant in spring G. astreata and P. lutea. The seasonal variations of all diazotrophic communities were significantly correlated with the seasonal shifts of ammonium and nitrate, suggesting that diazotrophs play an important role in the nitrogen cycle of the coral holobiont.

Comparison on soil organic carbon within two typical wetland areas along the vegetation gradient of Poyang Lake, China

Poyang Lake is an important wetland with international significance in biodiversity conservation and local carbon cycle. A study was conducted to investigate the effects of vegetation communities on seasonal and spatial variations of soil organic carbon (SOC) and dissolved organic carbon (DOC) in two dominant wetlands (dish-shaped pit wetland and delta wetland) of Poyang Lake, China. Results revealed significant variations of SOC and DOC along the vegetation gradient. Maximum accumulation of SOC and DOC was produced in Phragmites community, and the minimum ones in Phalaris community both in spring and in autumn. In comparison with delta wetland, dish-shaped pit wetland obtained higher SOC within the same vegetation type, which indicated that soils of dish-shaped pit wetland had greater capacity to store carbon. Compared with SOC, DOC represented stronger seasonal variations with great increase in autumn, which suggested that DOC was more sensitive to hydrology processing. Furthermore, significant variations of SOC and DOC were closely related to vegetation biomass both in spring and in autumn. Moreover, elevation and gradient also affected the distributing pattern of organic carbon suggesting significant influence of topography characteristics on the carbon pool.

Diversity in a Polymicrobial Community Revealed by Analysis of Viromes, Endolysins and CRISPR Spacers.

The polymicrobial biofilm communities in Mushroom and Octopus Spring in Yellowstone National Park (YNP) are well characterized, yet little is known about the phage populations. Dominant species, Synechococcus sp. JA-2-3B'a(2–13), Synechococcus sp. JA-3-3Ab, Chloroflexus sp. Y-400-fl, and Roseiflexus sp. RS-1, contain multiple CRISPR-Cas arrays, suggesting complex interactions with phage predators. To analyze phage populations from Octopus Spring biofilms, we sequenced a viral enriched fraction. To assemble and analyze phage metagenomic data, we developed a custom module, VIRITAS, implemented within the MetAMOS framework. This module bins contigs into groups based on tetranucleotide frequencies and CRISPR spacer-protospacer matching and ORF calling. Using this pipeline we were able to assemble phage sequences into contigs and bin them into three clusters that corroborated with their potential host range. The virome contained 52,348 predicted ORFs; some were clearly phage-like; 9319 ORFs had a recognizable Pfam domain while the rest were hypothetical. Of the recognized domains with CRISPR spacer matches, was the phage endolysin used by lytic phage to disrupt cells. Analysis of the endolysins present in the thermophilic cyanophage contigs revealed a subset of characterized endolysins as well as a Glyco_hydro_108 (PF05838) domain not previously associated with sequenced cyanophages. A search for CRISPR spacer matches to all identified phage endolysins demonstrated that a majority of endolysin domains were targets. This strategy provides a general way to link host and phage as endolysins are known to be widely distributed in bacteriophage. Endolysins can also provide information about host cell wall composition and have the additional potential to be used as targets for novel therapeutics.

Ecological provinces of spring phytoplankton in the Yellow Sea: species composition

Phytoplanktonic ecological provinces of the Yellow Sea (31.20°–39.23°N, 121.00°–125.16°E) is derived in terms of species composition and hydrological factors (temperature and salinity). 173 samples were collected from 40 stations from April 28 to May 18, 2014, and a total of 185 phytoplanktonic algal species belonging to 81 genera of 7 phyla were identified by Utermohl method. Phytoplankton abundance in surface waters is concentrated in the west coast of Korean Peninsula and Korea Bay, and communities in those areas are mainly composed of diatoms and cyanobacteria with dominant species of Cylindrotheca closterium, Synechocystis pevalekii, Chroomonas acuta, Paralia sulcata, Thalassiosira pacifica and Karenia mikimotoi, etc. The first ten dominant species of the investigation area are analyzed by multidimensional scaling (MDS) and cluster analysis, then the Yellow Sea is divided into five provinces from Province I (P-I) to Province V (P-V). P-I includes the coastal areas near southern Liaodong Peninsula, with phytoplankton abundance of 35 420×103–36 163×103 cells/L and an average of 35 791×103 cells/L, and 99.84% of biomass is contributed by cyanobacteria. P-II is from Shandong Peninsula to Subei coastal area. Phytoplankton abundance is in a range of 2×103–48×103 cells/L with an average of 24×103 cells/L, and 63.69% of biomass is contributed by diatoms. P-III represents the Changjiang (Yangtze River) Diluted Water. Phytoplankton abundance is 10×103–37×103 cells/L with an average of 24×103 cells/L, and 73.14% of biomass is contributed by diatoms. P-IV represents the area affected by the Yellow Sea Warm Current. Phytoplankton abundance ranges from 6×103 to 82×103 cells/L with an average of 28×103 cells/L, and 64.17% of biomass is contributed by diatoms. P-V represents the cold water mass of northern Yellow Sea. Phytoplankton abundance is in a range of 41×103–8 912×103 cells/L with an average of 1 763×103 cells/L, and 89.96% of biomass is contributed by diatoms. Overall, structures of phytoplankton community in spring are quite heterogeneous in different provinces. Canonical correspondence analysis (CCA) result illustrates the relationship between dominant species and environmental factors, and demonstrates that the main environmental factors that affect phytoplankton distribution are nitrate, temperature and salinity.

Assessment of nonselective elimination effects in rodent communities by methods of geometric morphometrics

Methods of geometric morphometrics and population phenogenetics have been used to evaluate morphogenetic rearrangements in two sympatric species of Myodes voles (M. glareolus Schreb. 1780 and M. rutilus Pall. 1779) from syntopic populations recovering after exposure to local “ecological vacuum” created as a result of rodent extermination in a natural focus of hemorrhagic fever in the southern taiga subzone of the Udmurt Republic. The model used in the study simulates the situation that arises upon nonselective elimination of rodent populations and communities in spring and their subsequent recovery. Analysis of variation in the size and shape of the mandible and in a complex of 30 nonmetric cranial characters has revealed similar (parallel) and species-specific morphogenetic and epigenetic changes occurring during the recovery of local rodent community. Species-specific differences in the pattern of change in the parameter characterizing within-group morphological disparity in the mandible shape (MNND) have been revealed between the dominant species (M. glareolus) and the subdominant species competing with it for territory (M. rutilus). Different reactions of close Myodes species in the course of filling the ecological vacuum are considered as a result of reduction in the level of competition for the subdominant species and a compensatory increase of morphological disparity in the dominant species under conditions of low density and incomplete composition of the community, in accordance with Chernov’s (2005) ecological compensation principle.

Bacterial communities in Arctic first-year drift ice during the winter/spring transition.

Horizontal and vertical variability of first-year drift-ice bacterial communities was investigated along a North-South transect in the Fram Strait during the winter/spring transition. Two different developmental stages were captured along the transect based on the prevailing environmental conditions and the differences in bacterial community composition. The differences in the bacterial communities were likely driven by the changes in sea-ice algal biomass (2.6-5.6 fold differences in chl-a concentrations). Copiotrophic genera common in late spring/summer sea ice, such as Polaribacter, Octadecabacter and Glaciecola, dominated the bacterial communities, supporting the conclusion that the increase in the sea-ice algal biomass was possibly reflected in the sea-ice bacterial communities. Of the dominating bacterial genera, Polaribacter seemed to benefit the most from the increase in algal biomass, since they covered approximately 39% of the total community at the southernmost stations with higher (>6 μg l(-1) ) chl-a concentrations and only 9% at the northernmost station with lower chl-a concentrations (<6 μg l(-1) ). The sea-ice bacterial communities also varied between the ice horizons at all three stations and thus we recommend that for future studies multiple ice horizons be sampled to cover the variability in sea-ice bacterial communities in spring.

Analysis of the metatranscriptome of microbial communities of an alkaline hot sulfur spring revealed different gene encoding pathway enzymes associated with energy metabolism.

Alkaline sulfur hot springs notable for their specialized and complex ecosystem powered by geothermal energy are abundantly rich in different chemotrophic and phototrophic thermophilic microorganisms. Survival and adaptation of these organisms in the extreme environment is specifically related to energy metabolism. To gain a better understanding of survival mechanism of the organisms in these ecosystems, we determined the different gene encoding enzymes associated with anaerobic pathways of energy metabolism by applying the metatranscriptomics approach. The analysis of the microbial population of hot sulfur spring revealed the presence of both aerobic and anaerobic organisms indicating dual mode of lifestyle of the community members. Proteobacteria (28.1%) was the most dominant community. A total of 988 reads were associated with energy metabolism, out of which 33.7% of the reads were assigned to nitrogen, sulfur, and methane metabolism based on KEGG classification. The major lineages of hot spring communities were linked with the anaerobic pathways. Different gene encoding enzymes (hao, nir, nar, cysH, cysI, acs) showed the involvement of microbial members in nitrification, denitrification, dissimilatory sulfate reduction, and methane generation. This study enhances our understanding of important gene encoding enzymes involved in energy metabolism, required for the survival and adaptation of microbial communities in the hot spring.

Species-rich meta-communities of the diatom order Thalassiosirales in the Arctic and northern Atlantic Ocean

The marine planktonic diatom order Thalassiosirales are used as climate proxies with reported characteristic temperate and Polar species. However, a systematic analysis of the genetic variability and species limits is lacking. Here, we combined molecular and morphological approaches to identify Thalassiosirales from 7 Beaufort Sea sea-ice samples and 27 water-column samples collected from across the Canadian Arctic at different times of the year and the Scotia Shelf, North Atlantic in spring. While many species were found in both oceanic regions, there were two distinct Thalassiosirales communities: the first from sea ice and ice-influenced water columns and the second Arctic late summer and North Atlantic spring communities. Thalassiosirales formed genetically coherent Boreal-Arctic meta-communities, inclusive of intra-specific variants. Genetic similarity between the Arctic and North Atlantic meta-communities would be reinforced by counter-clockwise dominant surface current systems. Local patterns of spatial and temporal distributions of planktonic thalassiosiroids were best explained by latitudinal gradients and phosphate and silicate concentrations, suggesting that climate-mediated changes in Arctic and North Atlantic hydrography could have a marked effect on species distribution. Our analysis also revealed a need for taxonomic revision of several species complexes reported from the region before they can be reliably used as bio-indicators.

Effects of winter severity on spring phytoplankton development in a temperate lake (Lake Erken, Sweden)

Phytoplankton seasonal succession has been linked to a variety of serial environmental changes, especially weather- and climate-induced physical forcing. This study compared spring phytoplankton dynamics after winters of different severity (cold, normal, and warm) in Lake Erken, Sweden. The spring diatom bloom was dominated by different functional groups: group A (centric diatoms 5–10 μm) after cold winters, B (centric diatoms >15 μm) after normal winters, and P (Aulacoseira granulata, Fragilaria crotonensis) after warm winters. Our results suggest that weather-related processes were the primary external drivers accounting for differences in spring phytoplankton dynamics in Lake Erken. Spring phytoplankton are influenced by overwintering species from the last autumn that can initiate the following spring bloom. Average taxonomic distinctness of the spring community was assessed using a new biodiversity measurement that incorporates taxonomic relatedness information. This value was lower than expected after warm and cold winters, which had winter air temperature 1°C deviation from an average value calculated over 21 years. Such winters increased the level of disturbance or stress to the lake, resulting in a spring with less diverse phytoplankton by narrowing the niche for species with various ecological requirements.

Temporal and Spatial Dynamics of Archaeal Communities in Two Freshwater Lakes at Different Trophic Status.

In either eutrophic Dianchi Lake or mesotrophic Erhai Lake, the abundance, diversity, and structure of archaeaplankton communities in spring were different from those in summer. In summer, archaeaplankton abundance generally decreased in Dianchi Lake but increased in Erhai Lake, while archaeaplankton diversity increased in both lakes. These two lakes had distinct archaeaplankton community structure. Archaeaplankton abundance was influenced by organic content, while trophic status determined archaeaplankton diversity and structure. Moreover, in summer, lake sediment archaeal abundance considerably decreased. Sediment archaeal abundance showed a remarkable spatial change in spring but only a slight one in summer. The evident spatial change of sediment archaeal diversity occurred in both seasons. In Dianchi Lake, sediment archaeal community structure in summer was remarkably different from that in spring. Compared to Erhai Lake, Dianchi Lake had relatively high sediment archaeal abundance but low diversity. These two lakes differed remarkably in sediment archaeal community structure. Trophic status determined sediment archaeal abundance, diversity and structure. Archaeal diversity in sediment was much higher than that in water. Water and sediment habitats differed greatly in archaeal community structure. Euryarchaeota predominated in water column, but showed much lower proportion in sediment. Bathyarchaeota was an important component of sediment archaeal community.