Development of filamentous green algae in the benthic algal community in a littoral sand-beach zone of Lake Biwa

Temporal changes of biomass and dominant species in benthic algal communities were investigated in a littoral sand-beach zone in the north basin of Lake Biwa from December 1999 to September 2000. Chlorophyll-a amounts of benthic algal communities per unit area of the sandy sediments rapidly increased from late April to June. Increases in biomass of the benthic algal communities are considered to result from the propagation of filamentous green algae Oedogonium sp. and Spirogyra sp. The cell numbers of filamentous green algae and chlorophyll-a amounts of benthic algal communities at depths of 30 and 50cm at a station protected by a breakwater in May were significantly higher than those of a station exposed directly to wave activity. Thus, the biomass accumulation of the benthic algal communities seems to be regulated strongly by wave disturbance. The development of filamentous green algae may contribute to the increase in biomass of the benthic algal community and to the changes in seasonal patterns of biomass in the sand-beach zone of Lake Biwa. We consider that the development of the filamentous green algal community in the littoral zone of Lake Biwa is the result of eutrophication.     

Consortia in Aquatic Ecosystems of the Transbaikalia

A survey in the basin of the Khilok River (a right tributary of the Selenga River) in 1999–2002 allowed us to reveal and describe the consortia of cyanobacteria Stratonostoc linckia f. linckia and Stratonostoc verrucosum, green alga Cladophora aegagropila, stonewort Nitella opaca, water moss Fontinalis sp., and duckweed Lemna trisulca. The relationship between the consort organisms and edificator plants can become the limiting factor in these communities. The long-term studies of the benthic communities of the Arakhlei Lake demonstrate the significance of the consortium approach in the long-term prediction of changes in the lake ecosystem.     

Successional Changes in the Microbial Community of the Alkaline Lake Khilganta during the Dry Season

Microbial processes in a shallow, saline, alkaline Lake Khilganta (Southern Siberia) were studied during the dry season. During the drought, a crust was formed on the lake surface, where low rates of production processes were observed, with predominance of anoxygenic photosynthesis at 2.3 mg C/(dm³ day). The rates of microbial processes increased after short-term rains. During this period, a thin cyanobacterial mat was formed on the bottom, in which filamentous cyanbacteria Geitlerinema spp. predominated and the rate of oxygenic photosynthesis was up to 18 mg C/(dm³ day). Subsequent water evaporation and salinity increase resulted in altered community types and their activity. Red spots emerged on the mat surface, where anoxygenic prototrophic members of the genus Ectothiorhodospira predominated. Anoxygenic photosynthesis became the main production process in microbial mats, with the rate of 60 mg C/(dm³ day). At salinity increase to 200 g/L, the water remained in small depressions on the bottom, where extremophilic green algae Dunaliella sp. predominated, and the rate of oxygenic photosynthesis was 0.877 mg C/(dm³ day). These changes in the type and activity of microbial communities is an example of succession of microbial communities in Southern Siberia saline lakes during drought.     

Factors affecting the survival and growth of bacteria introduced into lake water

The populations of Pseudomonas sp. B4, Escherichia coli, Klebsiella pneumoniae, Micrococcus flavus, and Rhizobium leguminosarum biovar phaseoli declined rapidly in lake water. The initially rapid decline of the two pseudomonads and R. phaseoli was followed by a period of slow loss of viability, but viable cells of the other species were not found after 10 days. The rapid initial phase of decline was not a result of Bdellovibrio spp., bacteriophages, or toxins in the water since Bdellovibrio spp. were not present and passage of the lake water through filters that should not have removed bacteriophages or soluble toxins led to the elimination of the rapid phase of decline. The addition of 250 g of cycloheximide and 30 g of nystatin per ml eliminated viable protozoa form the lake water, and the population of Pseudomonas sp. B4 did not fall and the decline of E. coli and K. pneumoniae was delayed or slowed under these conditions. Pseudomonas sp. L2 proliferated rapidly in lake water amended with glucose, phosphate, and NH₄NO₃, but its numbers subsequently fell abruptly; however, in water amended with cycloheximide and nystatin, which killed indigenous protozoa, the population density was higher and the fall in numbers was delayed. Of the nutrients, the chief response was to carbon, but when glucose was added, phosphorus and nitrogen stimulated growth further. Removing other bacteria by filtering the lake water before inoculation with Pseudomonas sp. L2 suggested that competition reduced the extent of response of the pseudomonad to added nutrients. We suggest that the decline in lake water of bacteria that are resistant to starvation may be a result of protozoan grazing and that the extent of growth of introduced species may be limited by the supply of available carbon and sometimes of nitrogen and phosphorus, and by predation by indigenous protozoa.     

Effect of total dissolved gas supersaturation on the survival of common carp (Cyprinus carpio) and silver carp (Hypophthalmichthys molitrix)

Flood discharge results in total dissolved gas (TDG) supersaturation downstream of a dam during the flood period. Fish suffer death from gas bubble disease (GBD) caused by TDG supersaturation. Nonetheless, current studies mainly attach importance to the survival of benthic fish affected by TDG supersaturation in the Yangtze River in China. Few studies have attempted to investigate the survival of pelagic fish influenced by TDG supersaturated water and compare the tolerance characteristics to TDG supersaturation between benthic and pelagic fish. To identify the survival of fish species that inhabit the various water layers affected by TDG supersaturation, silver carp (Hypophthalmichthys molitrix) (pelagic fish) and common carp (Cyprinus carpio) (benthic fish) were chosen to conduct an acute exposure experiment of four different TDG supersaturation levels (125%, 130%, 135% and 140%). The findings illustrated that the two fish species both exhibited evident aberrant behaviours of maladjustment in TDG supersaturated water. Obvious GBD symptoms were also found in the test fish. The survival probability of silver carp and common carp decreased with increasing levels of TDG supersaturation. The median survival time (ST₅₀) values of the silver carp exposed to four levels of TDG supersaturated water (125%, 130%, 135% and 140%) were 26.84, 7.96, 5.56 and 3.62 h, respectively, whereas the ST₅₀ values of common carp were 53.50, 26.00, 16.50 and 11.70 h, respectively. When compared with common carp, silver carp had a weaker tolerance to TDG-supersaturated water and were vulnerable to GBD. It shows that levels above 125% are not safe for common carp survival. In terms of the tolerance threshold value, silver carp merits further investigation because it showed lower tolerance to TDG than did common carp.     

Some Factors Influencing the Diversity and Species Composition of Benthic Invertebrate Communities in Twenty Arctic and Subarctic Lakes

The factors influencing the density, diversity and species composition of benthic invertebrate communities in 20 lakes in the Canadian arctic and subarctic were determined during 1975, 1976 and 1977. Despite small differences in nutrient and phytoplankton levels among the lakes, there was a strong positive correlation between these parameters and the density and diversity of the communities. Other factors, including maximum summer water temperature, lake depth and surface area had little overall effect on the communities. The densities of 2 ultra-oligotrophic chironomids (Heterotrissocladius oliveri and Micropsectra cf. groenlandica) increased markedly in cold deep lakes. However the abundance of the majority of species, most notably Procladius denticulatus, Tanytarsus sp., and Stictochironomus sp., was not effected by temperature. Other species, (Pontoporeia affinis, Monodiamesa bathyphila and Dicrotendipes nervosus) were probably restricted in their northern distribution by temperature. Surface area usually had little effect on the densities of all common species.     

Increased Benthic Algal Primary Production in Response to the Invasive Zebra Mussel (Dreissena polymorpha) in a Productive Ecosystem, Oneida Lake, New York

Increased water clarity associated with zebra mussel (Dreissena polymorpha) populations may favor benthic algal primary production in freshwater systems previously dominated by pelagic phytoplankton production. While zebra mussel-mediated water clarity effects on benthic primary production have been implicated in published reports, few production estimates are available. This study estimates benthic primary production in Oneida Lake, NY before and after zebra mussel invasion (1992), using measured photosynthetic parameters ( , α^B and β) from sampled benthic algal communities. In the summers of 2003 and 2004, primary production was measured as O₂ evolution from algal communities on hard (cobble) and soft (sediment) substrate from several depths. We also backcast estimates of benthic primary production from measurements of light penetration since 1975. Estimates of whole-lake epipelic and epilithic algal primary production showed a significant (4%) increase and exhibited significantly less interannual variability subsequent to the establishment of zebra mussels. We applied our model to two lakes of differing trophic status; the model significantly overestimated benthic primary production in a hypereutrophic lake, but there was no significant difference between the actual and predicted primary production values in the oligotrophic lake. The hypereutrophic lake had higher zebra mussel densities than Oneida (224 vs. 41 per sample respectively). Though total community respiration (measured in total darkness) was factored into our model predictions of production, our model may need modification when heterotrophic respiration is a large portion of total community metabolism.     

Bacterial communities in a crude oil gathering and transferring system (China)

Bacterial communities in crude oil and oil field production water samples from an oil gathering and transferring system in Changqing Oil field in China were investigated by 16S rRNA denaturing gradient gel electrophoresis (DGGE) analysis followed by gene cloning and sequencing. DGGE profiles showed that bacterial communities are far more rich in the water samples than that in the crude oil samples, and that bacteria related to Ochrobactrum sp. and Stenotrophomonas sp. were detected in all crude oil and oil field water samples. Bacteria related to Burkholderia sp., Brevundimonas sp., and Propionibacterium sp. were detected in the crude oil samples but not in water samples. Bacteria related to Hippea sp., Acidovorax sp., Arcobacter sp., Pseudomonas sp., Thiomicrospira sp., Brevibacterium sp., Tissierella sp. and Peptostreptococcus sp. were detected in the water samples but not in crude oil samples. Using an archaea-specific primer set, methanogens related to Methanomicrobials and Methanosarcinales were found in water samples but not in crude oil samples. The comparability of the microbial communities in the water and crude oil phase during the period of oil gathering and transferring process was 83.3% and 88.2%, respectively, indicating a stable structure of the microbial communities.     

Benthic community metabolism and trophic conditions of four South American lakes

Oxygen uptake rates of undisturbed sediment columns have been used as an integrative measure of the metabolic activities of benthic communities. Since the intensity of metabolic processes of profundal lake is dependent on the production of organic matter in the pelagic zone, oxygen uptake rates reflect the trophic condition of the whole lake. Four small lakes of central Chile, differing strongly in trophic conditions, provided a possibility to compare benthic oxygen uptake rates, under different oxygen conditions (Quiñenco, Grande, Chica and Lleulleu). Our objective was to establish the relationship between the oxygen uptake rates and bottom characteristics of lakes with different trophic conditions. At 8 mg O₂ l^-1 in the overlying water of the cores studied, the oxygen uptake rates of the sediment were: Quiñenco 51.2–56.0 mg O₂ m² h^-1 (eutrophic), Grande 41.2–46.4 mg O₂ m² h^-1 (mesotrophic), Chica 23.2–18.1 mg O₂ m² h^-1 (mesotrophic) and Lleulleu 11.7–16.0 mg O₂ m² h^-1 (oligotrophic). By exposing the sediments to different oxygen levels in the laboratory, it was found that benthic community metabolism decreased with oxygen concentrations. The slope of regression lines, relating oxygen uptake rates to oxygen concentrations, differed for the different sites investigated, closely related with the trophic conditions of the lakes. It was positively correlated with the organic matter content of the sediment of the cores (r ²= 0.78, p<0,05) and the nutrients of the bottom waters (total-P: r ²= 0.73, p<0,05; total-N: r ²= 0.73, p<0,05), and negatively with the redox potential of the sediments (r ²= 0.88, p<0,05).     

安徽省某酸性矿山废水坑湖中细菌群落的垂向分布特征及其影响因素

【目的】探究酸性矿山废水(acid mine drainage,AMD)坑湖中细菌群落沿垂向不同水深的分布规律及与环境因子之间的相互作用。【方法】采用16SrRNA基因高通量测序技术,对安徽省某AMD坑湖中6条采样垂线不同水深深度的细菌群落进行调查,同时测定水质理化指标,使用统计学软件分析细菌和地化参数间的联系。【结果】AMD坑湖中水质特征及细菌群落结构出现明显分层现象,自上而下溶解氧降低而pH和多种金属离子浓度增加,微生物群落结构发生变化,多样性和部分物种的丰度增大。细菌群落组成上,表层水域以Proteobacteria (Alpha、Gammaproteobacteria)和Acidobacteria占据主导地位;中下层水域则由Firmicutes、Acidobacteria、Actinobacteria、Gammaproteobacteria和Patescibacteria等共同主导。统计分析结果表明,TN、DO、ORP、pH、Fe、Mn、Al和Zn与嗜酸细菌丰度显著相关,是细菌空间分布的主要限制因素。【结论】AMD坑湖中水质理化特征和细菌群落分布在垂向空间上存在显著差异,群落的...     

Microbial community analysis in crab ponds by denaturing gradient gel electrophoresis

In order to investigate the role of microbial community in aquatic ecology and biogeochemical cycles, the bacterial community in crab ponds was investigated and the effects of aeration and season on the bacterial community were also assessed. Total DNAs from the water samples were amplified with universal primers and the amplicons were then resolved by denaturing gradient gel electrophoresis. Bands from the resulting profiles were excised and sequenced. Cluster analysis of the resulting profiles showed that the microbial community was affected by aeration and season. The microbial community between the surface and bottom of the water was very similar. A total of fifteen bands were obtained in this study. Three of them were 91–99% similar to uncultured bacterium clones. Three were 95–99% similar to uncultured Verrucomicrobia bacteria. Three were 97–100% similar to Actinobacterium sp.. Two were similar to Candidatus Limnoluna rubra with similarity 96 and 99%, respectively. Four were 99% similar to Rhodococcus sp., 100% similar to Sporosarcina sp., 100% similar to Stenotrophomonas sp., and 98% similar to Hydrogenophaga sp., respectively. The concentrations of dissolved oxygen, total nitrogen, total phosphorous, nitrite, and ammonia and pH values were significantly affected by season while only the pH value and the concentrations of dissolved oxygen and total nitrogen were significantly affected by aeration.     

Colonization and succession of benthic macroinvertebrates in Arcadia Lake,a South-Central USA reservoir

Colonization and succession of benthic macroinvertebrates in Arcadia Lake, an urban reservoir, were studied for four years. Physicochemical conditions including water temperature, dissolved oxygen concentrations, pH, specific conductance, and Secchi disc depth were also recorded. Colonization of the reservoir occured fairly rapidly through a sequence of three invasions. The first, and most significant, colonists were primarily facultative species already present in streams and ponds that were inundated by the impoundment. Later arrivals tended to be limnophilic species that probably came from other bodies of water. Of 30 species encountered in a pre-impoundment collection, only six were still present three years following impoundment. Thirty-three additional benthic macroinvertebrates species invaded the area following impoundment. Dominant taxa in the reservoir included Dero nivea, Limnodrilus sp., Chaoborus punctipennis, Chironomus sp., and Procladius sp. Pollutants accumulating in this urban reservoir, including metals and pesticides, and siltation probably have kept benthic populations relatively low and possibly reduced potential species diversity.     

The organic carbon budget of a shallow arctic tundra lake on the Tuktoyaktuk Peninsula,N.W.T., Canada

The organic carbon cycle of a shallow, tundra lake (mean depth 1.45 m) was followed for 5 weeks of the open water period by examining CO₂ fluxes through benthic respiration and anaerobic decomposition, photosynthesis of benthic and phytoplankton communities and gas exchange at the air-water interface. Total photosynthesis (as consumption of carbon dioxide) was 37.5 mmole C m^–2 d^–1, 83% of which was benthic and macrophytic. By direct measurement benthic respiration exceeded benthic photosynthesis by 6.6 mmole C m^–2 d^–1. The lake lost 1.4 × 10⁶ moles C in two weeks after ice melted by degassing C0₂, and 6.8 mmole C m^–2 d^–1 (1.5 × 10⁶ moles) during the remainder of the open water period; 2.2 mmole C m² d^–1 of this was release Of CO₂ stored in the sediments by cryoconcentration the previous winter. Anaerobic microbial decomposition was only 4% of the benthic aerobic respiration rate of 38 mmole C m^–2 d^–1. An annual budget estimate for the lake indicated that 50% of the carbon was produced by the benthic community, 20% by phytoplankton, and 30% was allochthonous material. The relative contribution of allochthonous input was in accordance with measurement of the ¹⁵N of sedimented organic matter.     

Paleopigment evidence of competition between phytoplankton and a cyanobacterial algal mat in a meromictic lake near Toronto,Ontario Canada

Crawford Lake, a meromictic lake located near Toronto, Canada, was cored to determine if algal pigments preserved in its sediments would make it possible to infer past changes in lake productivity over the last five hundred years. From 1500 to 1910 A.D. the sediments display extremely high levels of oscillaxanthin and myxoxanthophyll while chlorophyll derivatives and total carotenoids were relatively low. As the lake became increasingly more eutrophic in the latter part of the twentieth century, this relationship reversed itself. Competition for light between the deep dwelling cyanobacteria in the algal mat on the lake's bottom (8–14 m) and phytoplankton in the overlying surface layers of the water column (5–7 m) was attributed to the observed reduction in oscillaxanthin and myxoxanthophyll as Crawford Lake eutrophied. Because the major cyanobacteria in Crawford Lake are benthic mat forming Lyngbya and Oscillatoria, and not phytoplankton, competition for light with the overlying phytoplankton is critical in determining the total quantity of oscillaxanthin and myxoxanthophyll preserved in the lake's profundal sediments. These findings have major implications for the use of cyanobacterial pigments as indicators of lake trophic status in lakes where benthic algal mats are present.     

Gut content analysis of Gammarus lacustris from a Siberian lake using biochemical and biophysical methods

We studied the gut contents of Gammarus lacustris from the littoral of Shira lake, a Siberian salt lake, by microscopic analysis in conjunction with measuring of fluorescence of chlorophyll and composition of fatty acids. Gammarus ingested primarily fresh seston, probably settled on the bottom. Additionally, the amphipods obtained essential polyunsaturated fatty acids of 3 family by selectively consuming bottom sediment particles. A considerable part of the ingested seston comprised cells of Botryococcus sp., which passed the intestinal tract in living form and their photosynthetic activity increased. This viable gut passage was likely one of the causes of bloom of Botryococcusin the littoral. Unlike a number of literature data, there was no selective digestion of any fatty acid species, including polyunsaturated acids, in the intestinal tract.     

Diversity of Prokaryotes in Planktonic Communities of Saline Sol-Iletsk lakes (Orenburg Oblast,Russia)

Prokaryotic diversity was studied in the planktonic communities of six Sol-Iletsk lakes (Orenburg oblast, Russia) varying in salinity level using the Illumina technology of high-throughput sequencing. The extremely halophilic archaea of the phyla Euryarchaeota and Nanohaloarchaeota, as well as the bacterial phylum Bacteroidetes predominated in the communities of lakes with salinity of 285–300‰. Representatives of the phyla Bacteroidetes and Actinobacteria, as well as of the class Gammaproteobacteria were predominant in the lakes with salinity 110?180‰. A bloom of Cyanobacteria was observed in Bol’shoe Gorodskoe Lake (10‰ salinity). The dominant OTUs in the lakes with high salinity were represented by archaea Halonotius sp., uncultured Nanohaloarchaea, and bacteria Salinibacter sp. In the lakes with medium salinity level the dominants included gammaproteobacteria Spiribacter sp., alphaproteobacteria Roseovarius sp., flavobacteria Psychroflexus sp., unidentified archaea of the family Haloferacaceae, actinobacteria Pontimonas sp. and Rhodoluna sp. In the lake with low salinity level cyanobacteria of the genus Planktothrix were predominant. Effect of salinity on prokaryotic taxonomic richness, composition, and diversity in planktonic communities of the studied lakes was demonstrated.     

Some ecological aspects of Lake Qarun,Fayoum, Egypt. Part II. Production of plankton and benthic organisms

Distribution and abundance of phyto-, zooplankton and benthic organisms in Lake Qarun were investigated during the period from January 1974 to December 1977.Average number of phytoplankton cells was 152,300 cells/L and its biomass was 0.365 g/C/m³; average number of zooplankton was 31.44 × 10³/m³ and its biomass was 194.19 mg/m³. The average number of benthic fauna was 19889/m² and its biomass was 400.22 g/m² (dry wt.). Therefore, Lake Qarun may be considered as a highly eutrophic body of water.Freshwater planktonic species, that used to inhabit the lake, such as Diaptomus salinus and the cladoceran Moina salinarum, disappeared completely when the salinity of the lake water reached 30–34 However, some Rotatoria were able to withstand the high salinity. The new composition of the zooplankton community shows that the marine zooplankton species include not only Acartia latisetosa and Cirripedia nauplii, but also other species such as Polychaeta, Obelia medusae, etc.The benthos of Lake Qarun is characterised by an intensive growth of few species. The major part (i.e. 93.54% by weight) of bottom fauna in the lake is Mollusca, mainly Cerastoderma glaucum (69·84% by weight).     

Interrelation between plankton and benthos in the littoral algal community of Lake Yunoko,Central Japan

To ascertain the floristic interaction between phytoplankton and benthos in the littoral, the composition of each community was investigated and the effect of the substrata on the benthic communities was also examined.The main component of the benthic algal population wasFragilaria pinnata followed byF. pinnata var.lancettula. Although the dominant species of the plankton in the upper layers were similar to those in the limnetic, and those immediately above the bottom contained species of benthic origin, the similarity index of C implied high similarity between these two plankton layers. This index was developed by Morishita (1959) to measure the degree of overlap of component species between two communities. The value of C distributes from 0 to 1. The closer the value approaches 1, the more the communities are similar.For the dominant species, a significant difference was observed between the phytoplankton and benthic communities and in addition, C values indicated low overall similarity in the composition of the communities. These results suggest that there is little interrelation between phytoplankton and benthos even in the shallow littoral zone.     

Progress of eutrophication and change of chironomid fauna in Lake Yamanakako,Japan

Benthic macroinvertebrate distribution was studied on April 9, 1994, and March 2, 2003, in Lake Yamanakako. The average density of the benthic community for the entire lake was 3168ind.m^–2, comprising principally oligochaetes (41.0%) and chironomids (59.0%) in 1994. In 2003, the benthic community for the entire lake was 1847ind.m^–2, principally consisting of oligochaetes (69.9%) and chironomids (30.1%). In 1994, the larval density of Propsilocerus akamusi was 3.5 times that of Chironomus nipponensis and in 2003 the figure was 5.7 times. However, the larval biomass of P. akamusi was 2.1 times greater than that of C. nipponensis in 1994 and 2.8 times greater in 2003. The larval density of Tanypodinae decreased drastically, by about 12-fold, from 1994 to 2003. P. akamusi larvae were particularly abundant at the lake center in 1994, but they inhabited the entire lake bottom in 2003. P. akamusi density was closely related to water depth and ignition loss. C. nipponensis larvae also showed the widest distribution pattern in 2003, whereas their larvae had inhabited the northeastern parts and the lake center in 1994. Recently, the number of C. nipponensis larvae in Lake Yamanakako is tending to decrease, whereas that of P. akamusi larvae is increasing, suggesting ongoing eutrophication.     

Estimation of bottom ammonium affinity in the New Caledonia lagoon

Ammonium affinity of New Caledonia lagoon benthic communities was measured during the course of 33 in situ enrichment experiments, in order to estimate the contribution of benthos to ammonium fluxes. Ammonium chloride was injected into enclosures pushed into the sediment, in order to obtain a concentration of 20–22 mol l^-1 in the enclosed water which approximated the interstitial water content. Ammonium kinetic uptake was then followed for two hours. Grey-sand bottom displayed the highest affinity for ammonium, but white-sand and muddy bottom affinity was of the same order of magnitude. Macrophytes, and microphytes (when macrophytes are absent), account for the bulk of ammonium bottom uptake. As a result, grey-sand bottoms with their dense macrophyte cover represent a sink for water column nitrogen and play a key role in nutrient cycling of the lagoon. Correspondence to: G. Boucher