The antagonistic relationship between chlorophyll a concentrations and the growth areas of Trapa during summer in a shallow eutrophic lake

The relationship between concentrations of chlorophyll a in an open water area and growing areas of the macrophytes Trapa spp. and Nelumbo nucifera was investigated to clarify the role of macrophytes in phytoplankton growth in summer in a eutrophic shallow sand lake, Lake Honsagata, Japan. The chlorophyll a concentrations formed peaks in June 2007 and July 2008 in summer with cyanobacterial blooms composed of mainly Microcystis, Anabaena, Phormidium, and Oscillatoria, which decreased toward August and were maintained at different annual levels. The decline of blooms in August was caused by the rapid growth of macrophytes. The composition of phytoplankton and the level of bloom development in summertime differed characteristically from year to year. Also the total vegetation area of N. nucifera and Trapa spp. showed annually marked changes. A significant negative correlation between the concentrations of chlorophyll a and the growth areas of Trapa spp. in August was detected, indicating that the floating-leaved plants, Trapa spp., produced irregular, clear and turbid water states in this shallow eutrophicated lake. These antagonistic relations are explained based on a likely scenario of allelopathic effects on the development of cyanobacteria by Trapa spp. vegetation and the nutrient absorption competition among them. Our study demonstrated the potential of Trapa spp. to control cyanobacterial blooms producing harmful toxins.     

Spatial and temporal photosynthetic compartments during summer in Antarctic Lake Kitiesh

Summary Four autotrophic compartments were recognised in Lake Kitiesh, King George Island (Southern Shetland) at the beginning of the summer in 1987: snow microalgae, ice bubble communities, phytoplankton in the water column and benthic communities of moss with epiphytes. Chlorophyll a concentration and pigment absorption spectra were obtained in these four compartments before and/or after the thawing of the ice cover. During the ice free period, carbon fixation and biomass was measured in the phytoplankton and in the benthic moss Campyliadelphus polygamus. From these measurements we conclude that the benthic moss is the most significant autotrophic component in this lake in terms of biomass, chlorophyll a content and primary productivity. The integral assimilation number (The ratio of carbon fixation per unit area to biomass per unit area) values were similar for both phytoplankton and the moss, ranging from 3.6 to 5.4 mg C (mg Chl a)^–1h^–1in phytoplankton and from 4.0 to 6.4 mgC (mg Chl a)^–1h^–1 in the benthic moss. This approach allows comparisons of carbon fixation efficiency of the chlorophyll a under a unit area between compartments in their different light environments.     

Spatial structure and ecological efficiency in the summer zooplankton of a glacial lake

In June–July of 1993 and 1995, pelagic zooplankton dynamics of aglacial lake was investigated. In those years weather conditions diffferedsubstantially. This resulted not only in a great difference in the watersurface temperature (in 1993, <17.8± 0.47 °C; in 1995, 20.4± 0.33 °C), but also in an increase in the depth of metalimnionzone in 1995 in comparison with 1993. The ecological efficiency(K_e, the ratio of secondary to primary consumer productions,was 0.28 ± 0.031 in 1993 and 0.21± 0.034 in 1995. The higherK_e was accompanied by lowering of spatial structurization,primary and secondary consumer production. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spatial distribution of zooplankton in a shallow eutrophic lake, with a discussion of its relation to fish predation

Zooplankton distribution in a small, eutrophic lake was studiedover two seasons as part of a wider analysis of the fish-planktoninteraction. Patchiness was evident at all sample spacings,but autocorrelation between adjacent samples became significantonly at mean spacings of <10 m. Patchiness could only rarelybe correlated with environmental variables in open water, butthere were consistent trends in the distribution of most taxawith respect to the shore. The limnetic assemblage within 10m of the shore showed some littoral influence in the presenceof littoral taxa and the relative paucity of euplankters. Emphasisis placed on the impact on plankton distribution of fish predation,which varies markedly in the study lake. ¹ Present address: Department of Conservation, PO Box 1493,Taupo, New Zealand     

The dynamics of vertical chlorophyll distribution in an oligomesotropbic lake

The vertical distribution of chlorophyll was examined in relationto physical and chemical parameters in oligomesotrophic LakeSamish, Washington state, during the latter half of a growingseason. A majority of chlorophyll resided in the metalimnionin late July, with metalimnetic populations dominated by diatoms(Cyclotella bodanica) and chrysophytes (Mallomonas caudata,Dinobryon sertularia). A silica gradient appeared to be mostimportant in determining the vertical position of these populations.Later in the season, segregation of nutrients and light, inthe face of a deepening epilimnion, led to transient accumulationsof phytoplankton at the top of the metalimnion. It appearedthat losses due to heterotrophic activities accentuated thelower boundary of this chlorophyll peak.     

Spatial and temporal distribution of fish and zooplankton in a shallow lake

Summary 1. We performed both a large- and a small-scale echo sounding study on the spatial and temporal distribution of fish (mainly roach, Rutilus rutilus and perch, Perca fluviatlis ), as well as a small-scale study of zooplankton distribution in the small, shallow and eutrophic Lake Hanebjerg in Denmark. In the small-scale study, sampling was conducted in open water as well as in the edge zone immediately outside two different types of vegetation.
2. Fish daytime abundances differed between the northern and the southern parts of the lake and, on a small scale, small fish aggregated in the edge zones during day, preferably outside dense emergent vegetation. Copepods avoided emergent vegetation, while cladocerans showed no habitat preference. Both small fish and cladoceran numbers were found to be higher during night than day.
3. The relative abundance (number per sample) of cladocerans in the edge zone immediately outside vegetation was negatively correlated with the relative abundance of fish in that zone. There was no correlation between cladoceran and fish abundance in open water, or between the relative abundance of copepods and fish.
4. The presence of pelagic piscivores in combination with avoidance behaviour of both fish and zooplankton is a likely explanation for the observed distribution of small fish and cladocerans in Lake Hanebjerg. Both small- and large-scale distribution patterns may be dependent on the type and distribution of complex structure in the lake. Even in a small lake, large-scale patterns may affect the interpretation of small-scale data.     

A preliminary study of oligochaetes in Poyang Lake,the largest freshwater lake of China,and its vicinity,with description of a new species of Limnodrilus

The oligochaete fauna of the largest freshwater lake of China, Poyang Lake, has never been investigated before. On the basis of a preliminary survey in the lake and its vicinity in 1997–1999, 25 species belonging to 20 genera and 5 families are recorded. Among them, one genus, Cernosvitoviella (Enchytraeidae), and two species, Bratislavia unidentata (Naididae), Potamothrix bedoti (Tubificidae), are recorded from China for the first time. Another tubificid, Limnodrilus paramblysetus sp. nov., is new to science. It is similar to L. amblysetus Brinkhurst et al., 1990 in chaetal shape but differs in having short hooded penis sheaths.     

Spatial distribution of sharks captures in the Pacific of Nicaragua and its relationship with several oceanographic variables

Between August 1995 and August 1997 long line fishing techniques and a bathythermograph were used to correlate some physical variables with the spatial distribution of four shark species in 26 fishing cruises off the Nicaraguan Pacific Coast. They were the thresher (Alopias vulpinus), blue (Prionace glaucea), gray (Carcharhinus falciformis) and hammer (Sphyra lewini). All species concentrated in the southeastern Nicaraguan Pacific, at the seasonal upwelling area of Papagayo Gulf. The range of sea surface temperatures in which the sharks were captured was 25-28 degrees C. We could clearly associate this physical parameter with shark availability. The vertical distribution of the captured sharks suggests that they occupy termocline levels above the 15 degrees C isotherm. Although these species are oceanic, the blue shark was captured in ocean waters over the 1800 m isobar, while the grey and thresher sharks where close to the continental shelf. Body length in decreasing order are: thresher (210-290 cm, SN = 21), blue (60-240 cm, SN = 13) and gray (80-200 cm, SN = 17).     

Spatial and temporal distribution patterns of three trophic levels in a saline lake

Horizontal distribution patterns of three trophic levels wereinvestigated at Mono Lake, California, USA during the autumnsof 1980 and 1981. Coefficients of variation for Anemia monicaand grebes peaked in October of both years, whereas coefficientsof variation for phytoplankton declined from August to November.Stable population gradients were observed in the Anemia population.In contrast, grebes were very mobile and their distributionalpatterns changed between sampling dates. Anemia and phytoplanktonwere negatively correlated during 1980, but no significant correlationsoccurred in 1981. Grebes and Artemia were positively correlatedin October 1980 and 1981, suggesting active prey tracking bythe grebes. Interactions between trophic levels may have contributedto the creation and maintenance of patchiness, although theseeffects appeared to be intermittent.     

Vertical distribution of organic constituents in an Antarctic lake: Lake Vanda

Vertical distribution of organic constituents, i.e. total organic carbon (TOC), extractable organic carbon with ethyl acetate (EOC), hydrocarbons, phytol, sterols, fatty acids and phenolic acids in Lake Vanda was studied to elucidate their features in relation to the stratification of lake water and the distribution of lake organisms. The concentrations of TOC, EOC and sterols increased with depth and attained the maximum values of 25 and 1.5 mgC l^–1 and 1.4 g l^–1 in the bottom, respectively, while those of fatty acids showed the maximum value of 61 g l^–1 at a depth of 55.4 m, along with the highest value of the ratio of unsaturated (UC₁₆, uC₁₈) to saturated (C₁₆, C₁₈) acids (8.5) and with the highest carbon preference index (35). Hydrocarbons were only found in the bottom layers (60.4 and 65.9 m) and bottom sediment. These results suggest strongly that the vertical distribution of lake organisms and their activity are quite different due to depth. In the bottom warm anoxic layers the degradation of organic materials must have occurred significantly and thus refractory organic materials should be concentrated.     

Vertical distribution of organic constituents in an Antarctic lake: Lake Fryxell

Vertical distribution of organic constituents, i.e. total organic carbon (TOC), hydrocarbons, fatty acids and hydroxy acids in water and sediment samples from Lake Fryxell (77° 35 S, 163° 15 E) of southern Victoria Land, Antarctica were studied to elucidate their features in relation to stratification of the lake waters and likely distribution of microorganisms. The TOC content of the surface water (5.0 m; just below the ice cover of 4.50 m thickness) was 1.4 mg l^–1. It increased markedly with depth and attained a maximum value of 21.7 mg C l^–1 at a depth of 17.5 m, but decreased to the bottom (13.3 mg C l^–1). The high TOC content of the anoxic bottom layers (> 15 m) is attributable to the concentration of refractory organic substances over long periods following the degradation of labile organic constituents. Hydrocarbons were not found in the water column, but the major constituent of the bottom sediment was n-C_{29 : 2} alkene. Total concentrations of fatty acids in the oxic layers ( 10 m) were highest at 10.0 m and much higher than those in the anoxic layers (> 10 m), probably reflecting the phytoplankton population. The content of branched (iso and anteiso) fatty acids and 3-hydroxy acids in the anoxic layers were much greater than those in the oxic layers which would seem to reflect the distribution of bacterial abundance. The differences of organic composition between the water column and sediments imply that sinking dead organisms were quickly degraded in the lake bottom. Also, the composition of microorganisms in the water column must be very different from that in the sediments.     

Macrozoobenthic community of Poyang Lake,the largest freshwater lake of China,in the Yangtze floodplain

Poyang Lake (Poyang Hu) is located at the junction of the middle and lower reaches of the Yangtze (Changjiang) River, covering an area of 3283 km². As one of the few lakes that are still freely connected with the river, it plays an important role in the maintenance of the unique biota of the Yangtze floodplain ecosystem. To promote the conservation of Poyang Lake, an investigation of the macrobenthos in the lake itself and adjoining Yangtze mainstream was conducted in 1997–1999. Altogether 58 benthic taxa, including 22 annelids, 8 mollusks, 26 arthropods, and 2 miscellaneous animals, were identified from quantitative samples. The benthic fauna shows a high diversity and a marine affinity. The standing crops of benthos in the lake were much higher than those in the river, being 659 individuals/m² and 187.3 g/m² (wet mass) in the main lake, and 549 individuals/m² and 116.6 g/m² in the lake outlet, but only 129 individuals/m² and 0.4 g/m² in the river. The dominant group in the lake was Mollusca, comprising 63.4% of the total in density and 99.5% in biomass. An analysis of the functional feeding structure indicated that collector-filterers and scrapers were predominant in the lake, up to 42.2% and 24.7% in density and 70.2% and 29.2% in biomass, respectively, while shredders and collector-gatherers were relatively common in the river. The present study was restricted to the northern outlet and the northeast part of Poyang Lake. A scrutiny is required for the remaining areas.     

鄱阳湖生态经济区成立前后NDVI时空动态变化及其驱动因素

鄱阳湖生态经济区是中部地区正在加速形成的增长极之一,研究其植被变化特征可以为鄱阳湖生态经济区更合理的调控经济发展与生态保护提供支持。本研究基于2000—2017年MODIS NDVI,采用最小二乘法斜率探讨生态经济区成立前后NDVI时空变化特征,并借助相关性分析定量化研究气候因素和人为因素对NDVI变化的驱动作用。结果表明:生态经济区成立前(2000—2008年)和成立后(2009—2017年),区域植被覆盖整体均呈现增长趋势。生态经济区成立前NDVI变化趋势为0.052 10 a^-1(P<0.05),成立后NDVI变化趋势为0.025 10 a^-1(P<0.05),成立后NDVI增长出现放缓现象;空间上,成立前植被发生退化的区域主要分布在地级市和省会周围;成立后,省会和中心城市周围植被退化现象进一步加剧,同时湖区周围、区域北部以及南部农耕区植被也出现退化现象;在影响因素方面,在全区域尺度上,气候因素是NDVI变化的主导因素,气温对NDVI影响大于降水;在NDVI显著变化的区域,人类活动则是影响NDVI变化的主要因素;生态经济区成...     

Spatial distribution of the gypsy moth [Lepidoptera: Lymantriidae] and some of its parasitoids within a forest environment

Aspects of the microhabitat distributions of the gypsy moth,Porthetria dispar (L.) (Lepidoptera: Lymantriidae), and some of its parasitoids were investigated in the field by means of sticky panels and gypsy moth egg masses exposed at different heights in trees, by egg masses exposed within forested and cleared areas, and by gypsy moth pupal collections from different heights in trees.Ooencyrtus kuwanai (Howard)(Hymenoptera: Encyrtidae), Apanteles melanoscelus Ratzeburg (Hymenoptera: Braconidae), and gypsy moths were caught most frequently on stickly panels placed in upper portions of trees. In contrast,Apanteles laeviceps Ashmead, a parasitoid of cutworms, was most often caught near the forest floor.O. kuwanai attacked equally egg masses exposed at different heights in trees, but parasitized those in a clearing less often than those within the forest prosper.Brachymeria intermedia (Nees) (Hymenoptera: Chalcididae) emerged mostly from pupae collected near the tops of trees and not at all from those collected below 5 m. The results are discussed as they relate to field sampling procedures, behavioral activities of gypsy moth and parasitoid adults, and integrated control possibilities for the gypsy moth.     

The relationship between phytoplankton biovolume and chlorophyll in a deep oligotrophic lake: decoupling in their spatial and temporal maxima

The seasonal distributions of phytoplankton biovolume and chlorophylla content were monitored for 14 months in a deep oligotrophic,high mountain lake (Redó, Pyrenees). An allometric relationshipof chlorophyll with biovolume was found throughout the periodstudied, with a correlation coefficient of 0.66. However, therelationship changed with season and the taxonomic compositionof the phytoplankton. Both parameters showed a similar seasonalpattern, but differences in space and time were observed. Thechlorophyll maximum was recorded deeper and later than thatof phytoplankton biovolume. While the biovolume maximum wasrelated to an improvement in conditions for growth (nutrientinput during column mixing periods), and reflected an increasein biomass, the chlorophyll maximum was related to changes incell pigment content, and to spatial or successional trendsin species dominance. Flagellated chrysophytes predominatedat the chlorophyll maxima. Chlorophyll content per unit of phytoplanktonbiovolume fluctuated greatly throughout the year, dependingon light intensity, temperature and phytoplankton composition.Of the main groups of phytoplankton in the lake, the dinoflagellates,which dominated the summer epilimnion phytoplankton community,recorded the lowest pigment content per biovolume (which isconsistent with their size). Higher chlorophyll contents perbiovolume were found in the deep hypolimnion and during thewinter cover period associated with small cells such as somespecies of chlorococcales chlorophytes. When flagellated chrysophyteswere predominant, a broad range of chlorophyll values per biovolumewas found and there was no significant correlation between thetwo biomass indices. These findings reaffirm the need to treatphytoplankton biomass estimates with caution, in particularwhen conducting primary production studies. While our resultsshow that changes in chlorophyll content per cell occur as aphotoacclimation response along a vertical profile, they alsopoint out a component of the successional trends which appearin a phytoplankton growth phase in a lake.     

Littoral benthos of a Victorian lake and its outlet stream: Spatial and temporal variation

Abstract There have been few comparative studies of the fauna in the two major types of freshwater systems, lakes and streams, in the one locality. This study compared the faunal assemblages at two times of the year (summer and winter) on stones in three locations: the littoral zone of two shores in Lake Purrumbete (one wave-exposed and one sheltered) and riffles in the Curdies River, which flows out of the lake. The lake fauna was dominated by crustaceans, gastropods and planarians, whereas the stream fauna was dominated by insects. The most abundant lake taxa were also present, but much less abundant, in the stream. The total number of species and individuals and densities of some common species varied between the three locations and between seasons. However, no consistent pattern reflecting a difference between the two lake shores was evident. Interpretation of MDS ordinations of the lake fauna was dependent on the data standardizations applied, with increased separation of the season-location combinations when species were standardized to equal total abundances; the seasonal difference was always greatest for the exposed (cliff) shore. In contrast, MDS on the stream fauna showed seasonal differences under all standardizations. This was consistent with the high seasonal turnover of species in the stream compared with the lake. These results demonstrate that, even within a local area with similar geology and connected water bodies, lake and stream fauna from the same substratum (stones) can be markedly different. Taxa that occurred in both were more abundant in the lake, whereas seasonal differences in abundance were much greater in the stream.     

Spatial distribution and historical deposition behaviors of perfluoroalkyl substances (PFASs) in sediments of Lake Chaohu,a shallow eutrophic lake in Eastern China

Sediment samples were collected from the Chaohu Lake basin to investigate the spatial distribution and historical deposition behaviors of 17 perfluoroalkyl substances (PFASs). Concentrations of the total PFASs (∑PFASs) in limnetic sediments ranged from 0.719 to 2.429 ng/g dry weight (dw), with an average of 1.449 ng/g dw. A clear gradient in the spatial distribution was observed from west to east in surface sediments of Lake Chaohu. Perfluorooctane sulfonic acid and perfluorooctanoic acid were predominant in limnetic sediments, with an average of 0.383 and 0.275 ng/g dw, respectively. The ∑PFASs concentrations in riverine sediments were the highest in the Shiwuli River, followed by the Nanfei River. PFASs in riverine sediments indicated that industrial discharge and urban runoff played key roles in PFAS distribution and pollution levels. In vertical profiles, concentrations of the ∑PFASs and PFAS congeners in three sediment cores generally increased with decreasing depths, indicating that the input history of the ∑PFASs could be attributed to the development of industrialization and urbanization in the Chaohu Lake basin. The correlations between PFASs and sedimentary characteristics, organic carbon, nutrients and inorganic salts suggested that both hydrophobic and electrostatic effects played important roles in PFAS distribution and pollution levels in sediments of Lake Chaohu.     

Dynamic distribution of Spatial during mouse spermatogenesis and its interaction with the kinesin KIF17b

The Spatial gene is expressed in highly polarized cell types, such as epithelial cells in the thymus, neurons in the brain and germ cells in the testis. In this study, we report the characterization and distribution of Spatial proteins during mouse spermatogenesis. Besides Spatial-epsilon and -delta, we show that the newly described short isoform Spatial-beta is expressed specifically in round spermatids. Using indirect immunofluorescence, we detected Spatial in the cytosol of the early round spermatid. By the end stages of round spermatids, Spatial is concentrated at the opposite face of the acrosome near the nascent flagellum and in the manchette during the elongation process. Finally in mature sperm, Spatial persists in the principal piece of the tail. Moreover, we found that Spatial colocalizes with KIF17b, a testis-specific isoform of the brain kinesin-2 motor KIF17. This colocalization is restricted to the manchette and the principal piece of the sperm tail. Further, coimmunoprecipitation experiments of native proteins from testis lysates confirmed Spatial-KIF17b association through the long Spatial-epsilon isoform. Together, these findings imply a function of Spatial in spermatid differentiation as a new cargo of kinesin KIF17b, in a microtubule-dependent mechanism specific to the manchette and the principal piece of the sperm tail.     

Depth distribution of microbial diversity in Mono Lake,a meromictic soda lake in California

We analyzed the variation with depth in the composition of members of the domain Bacteria in samples from alkaline, hypersaline, and currently meromictic Mono Lake in California. DNA samples were collected from the mixolimnion (2 m), the base of the oxycline (17.5 m), the upper chemocline (23 m), and the monimolimnion (35 m). Composition was assessed by sequencing randomly selected cloned fragments of 16S rRNA genes retrieved from the DNA samples. Most of the 212 sequences retrieved from the samples fell into five major lineages of the domain BACTERIA: alpha- and gamma-Proteobacteria (6 and 10%, respectively), Cytophaga-Flexibacter-Bacteroides (19%), high-G+C-content gram-positive organisms (Actinobacteria; 25%), and low-G+C-content gram-positive organisms (Bacillus and Clostridium; 19%). Twelve percent were identified as chloroplasts. The remaining 9% represented beta- and delta-Proteobacteria, Verrucomicrobiales, and candidate divisions. Mixolimnion and oxycline samples had low microbial diversity, with only 9 and 12 distinct phylotypes, respectively, whereas chemocline and monimolimnion samples were more diverse, containing 27 and 25 phylotypes, respectively. The compositions of microbial assemblages from the mixolimnion and oxycline were not significantly different from each other (P = 0.314 and 0.877), but they were significantly different from those of chemocline and monimolimnion assemblages (P < 0.001), and the compositions of chemocline and monimolimnion assemblages were not significantly different from each other (P = 0.006 and 0.124). The populations of sequences retrieved from the mixolimnion and oxycline samples were dominated by sequences related to high-G+C-content gram-positive bacteria (49 and 63%, respectively) distributed in only three distinct phylotypes, while the population of sequences retrieved from the monimolimnion sample was dominated (52%) by sequences related to low-G+C-content gram-positive bacteria distributed in 12 distinct phylotypes. Twelve and 28% of the sequences retrieved from the chemocline sample were also found in the mixolimnion and monimolimnion samples, respectively. None of the sequences retrieved from the monimolimnion sample were found in the mixolimnion or oxycline samples. Elevated diversity in anoxic bottom water samples relative to oxic surface water samples suggests a greater opportunity for niche differentiation in bottom versus surface waters of this lake.     

Parameterization of chlorophyll a-specific absorption coefficients and effects of their variations in a highly eutrophic lake: a case study at Lake Kasumigaura, Japan

The chlorophyll a-specific absorption coefficient ( a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) ) in a highly eutrophic lake can show characteristics distinct from that in the ocean due to the differences in the structure and composition of phytoplankton. In this study, investigated the variation of a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) in Lake Kasumigaura, a highly eutrophic lake in Japan, in association with the package effect and the effect of accessory pigments, and carried out the parameterization of a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) . Although a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) did not vary spatially, it did show significant temporal variation, with a particularly high value after spring-bloom. This high a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) in spring was attributed to a lower package effect and a higher proportion of carotenoid than the other samples. Although the value of a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) was correlated with the concentration of chlorophyll-a (Chl-a), the correlation coefficient was lower than those reported in the ocean. Some lake-water samples showed variations of the package effect and the effect of accessory pigments that were independent of the concentration of Chl-a, and these independent variations resulted in the weak correlation between a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) and the concentration of Chl-a. Together, these results suggest that the factors controlling a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) in highly eutrophic lakes are distinct from that in ocean samples.