Altitude and seasonal polymorphism of Keratella cochlearis (Rotifera) in lakes of the Auvergne, Central France

In July 1980 samples of the rotifer Keratella cochlearis were taken from ten lakes ranging in altitude from 630 to 1244 in above sea level. The total period of sampling was short enough to ensure that seasonal effects were negligible. The mean lorica length and mean posterior spine length showed a positive relationship with lake altitude. This indicates that the lower temperatures at higher altitudes delay the normal summer diminution in size of the lorica and the posterior spine. The conductivity of the lake waters varied from 14 to 100 μmho cm^-1 20°c^-1, but no relationship to the dimensions of K. cochlearis was found.     

The flora, fauna and water chemistry of Tagimaucia crater, a tropical highland lake and swamp in Fiji

SUMMARY. 1. Tagimaucia crater lake and swamp are located at an altitude of 820m in Taveuni, Fiji (lat. 16°S; long. 179°56'W). Rainfall exceeds evaporation in all seasons and residence time for water in the shallow lake (2.5–5.5 m deep) is only 4 days.
2. Dissolved ion concentrations are low (conductivity 14–18μScm^−lat 25°C), and the water is slightly acidic (pH 5.0–6.5 at 25°C), Median total phosphorus (0.5 gm⁻³) and total nitrogen (3.3gm⁻³) are moderately high and probably represent dissolved and suspended organic matter. Median chlorophyll a concentrations (2.5 mg⁻³) were low and indicate low phytoplankton productivity.
3. The swamp vegetation is dominated by Lepironia articulate (Retz.) Domin and algae which form floating sedge peat islands, and Pandanus taveuniensis St John and other small trees where alluvium and colluvium are infilling the margins of the crater. The surrounding slopes are forested.
4. The fauna of the lake and swamp are low in both diversity and abundance. The only aquatic vertebrates observed were Anguilla eels and cane toads, Bufo marinus L., and the only bird was the swamp harrier, Circus approximans approximate Peale. A variety of aquatic insects were observed but crustaceans and other invertebrate taxa were scarcely recorded.
5. Although the swamp and lake are otherwise undisturbed, several recently introduced plants and animals have been recorded.     

Associations and distribution of benthic nematodes in the Ethiopian Rift Valley lakes

The nematode associations in six Ethiopian rift lakes, one man-made lake, and three crater lakes were studied and related to water conductivity, lake depth and sediment particle size. The lakes investigated lie at moderate altitudes (1200–2000 m), are alkaline and vary in their conductivities. The rift lakes Abijata and Shala and the crater lakes Aranguadi, Kilotes and Chitu are soda lakes (K₂₅ > 6000 μS cm⁻¹), while the remaining five lakes and the man-made Lake Koka are within the freshwater range of conductivity (K₂₅ < 6000 μS cm⁻¹). A total of 16 species were identified including six new species. The nematode associations varied between lakes and were restricted to very few species in each lake. Most nematodes were restricted to non-saline lakes. The most dilute L. Zwai had a higher number of nematode species (12) and abundance than other lakes. The saline lakes Shala and Kilotes had nematode assemblages made up of only a single species (Mesodorylaimus macrospiculum). No nematodes were found in the hypersaline crater L. Chitu. Tobrilus africanus appeared more euryhaline than other nematodes occurring at conductivities as high as 15 000 μ S cm⁻¹ (L. Abijata). Five of the most common species (Dorylaimus sp., Monhystera stagnalis, Aphanolaimus tudoranceai, Tobrilus africanus and Actinolaimus perplexus) were associated with medium grained sand. A monthly variation in density of nematodes in L. Zwai is also shown.     

Associations of rotifers in Australian crater lakes

Associations of rotifers in 12 Australian crater lakes have been compared by means of indices of similarity and diversity, and by two dimensional ordination. Four of the lakes lay on the Atherton Tableland in tropical Queensland, four were shallow saline lakes in Victoria and the remaining four were fresh lakes in the same general region as the saline lakes.
The total number of species identified was 67, but the maximum found in any one sample was 27. Salinity is an important factor reducing diversity, whilst the development of vegetation increases the diversity of the rotifer fauna. The index of diversity (a) ranged from less than one in the saline lakes to 13 in the richly vegetated Lake Euramoo.
Comparisons with the rotifers living in the open waters of crater lakes in Africa, Indonesia and Europe revealed no marked similarities between the fresh Australian lakes and these other regions, although strong similarities were found between Ausralian saline lakes and those of other regions. In general the rotiferan faunas of the Australian crater lakes resembled each other less than might be expected from the similarities found between crater lakes within other regions.     

Short-term thermal acclimation induces adaptive changes in the inner mitochondrial membranes of fish skeletal muscle

In the oxidative muscles (musculi laterales superficiales) of crucian carp Carassius carassius acclimated for 6 weeks to either 5 or 25° C, the volume density and the surface density of fibres per tissue did not differ significantly between the control and experimental groups. The correlation ratio (μ²) for these values was below 50, 39·3 and 43·9 respectively. After acclimation to 5° C, the surface density of outer mitochondrial membrane per fibre increased significantly from 0·93 to 1·23m² cm⁻³ in the summer population but dropped from 0·94 to 0·67 m² cm⁻³ in the winter population. The surface density of outer mitochondrial membrane per mitochondrion increased from 3·24 to 4·52 m² cm⁻³ in summer fish. After acclimation to 25° C, the surface density of inner mitochondrial membranes per muscle fibre decreased from 4·04 to 1·79 m² cm⁻³ in summer fish and from 3·86 to 1·07 m² cm⁻³ in winter fish. The surface density of inner mitochondrial membranes per mitochondrion increased from 14·17 to 15·60 m²cm⁻³ in summer fish but dropped from 13·91 to 10·67 m² cm⁻³ in winter fish. Correlation matrices demonstrate a negative correlation of the surface density of outer mitochondrial membrane per mitochondrion with the volume density of mitochondria per fibre and temperature, suggesting cold-induced proliferation of small mitochondria. It was concluded that short-term cold acclimation increased surface area of the inner mitochondrial membranes in summer fish.     

Antimicrobial effect and shelf-life extension by combined thermal and pulsed electric field treatment of milk

Aims:  The impact of a combined hurdle treatment of heat and pulsed electric fields (PEF) was studied on native microbiota used for the inoculation of low-fat ultra-high temperature (UHT) milk and whole raw milk. Microbiological shelf-life of the latter following hurdle treatment or thermal pasteurization was also investigated.
Methods and Results:  UHT milk was preheated to 30°C, 40°C or 50°C over a 60-s period, pulsed for 50  μ s or 60  μ s at a field strength of 40 kV cm⁻¹ or for 33  μ s at 50 kV cm⁻¹. Heat and PEF reduced the microbial count by a maximum of 6·4 log in UHT milk (50°C; 50 kV cm⁻¹, 33  μ s) compared to 6·0 log ( P  ≥ 0·05) obtained by thermal pasteurization (26 s, 72°C). When raw milk was treated with a combination of hurdles (50°C; 40 kV cm⁻¹, 60  μ s) a 6·0 log inactivation of microbiota was achieved and microbiological milk shelf-life was extended to 21 days under refrigeration (4°C) vs 14 days in thermally pasteurized milk. Native microbiota was decreased by 6·7 log following conventional pasteurization.
Conclusions:  The findings suggest that heat and PEF achieved similar inactivation of native microbiota in milk and longer stabilization of microbiological shelf-life than thermal pasteurization.
Significance and Impact of the Study:  A hurdle approach of heat and PEF could represent a valid milk processing alternative to conventional pasteurization. Hurdle treatment might also preserve native milk quality better due to less thermal exposure.     

The distribution of macroinvertebrate communities in two Portuguese rivers

SUMMARY. 1. The distribution of macroinvertebrates in two chemically different rivers of Central Portugal (Soure and Alva) was analysed.
2. In the Soure, a lowland, alkaline river (mean values for alkalinity, conductivity and pH, 101 mg I⁻¹ CaCO₃, 255 μS cm⁻¹ and 7.8, respectively), a relatively high number of individuals and low diversity (mean H '= 2.27) was found. There was considerable temporal variation in the number of individuals present.
3. In the Alva, a highland, acidic river (mean values for alkalinity, conductivity and pH. 4.8 mg 1⁻¹ CaCO₃, 22 μ S cm⁻¹ and 5.7, respectively), diversity was higher (mean H '=3.41). There were large temporal changes in the number of species present, but not in the number of individuals.
4. Similarity indices and cluster analysis identified six site-types and seventeen groups of co-occurring taxa. Some of the taxonomic groups were characteristic of one or more sites, hut others had no strong association with a particular site. Although the rivers differed considerably in terms of physico-chemistry, communities in the upper sections of the two rivers were more similar to each other, than to other communities in the same river. The way the samples of both rivers were clustered seems to indicate that community structure was influenced by factors associated with (1) within river longitudinal variation (e.g. substrate grain size), (2) water chemistry, and (3) seasonal variations (e.g. temperature, flow).     

Taxonomic composition and biomass of heterotrophic flagellates in relation to lake trophy and season

1. Taxonomic composition and abundance of heterotrophic flagellates (HF) were studied in 55 lakes with different trophy in northern Germany using a live-counting technique.
2. Mean abundances and biomasses of HF ranged from 169 cells L⁻¹ and 22 μg L⁻¹ in mesotrophic lakes to 2439 cells mL^–1 and 475 μg L⁻¹ in hypertrophic lakes, respectively. Highest values were generally observed in spring, but mesotrophic lakes showed maximum values in early summer.
3. The taxonomic composition of HF was not significantly influenced by lake trophy and season. The major fraction of HF consisted of chrysomonads and Protista incertae sedis; other important groups were choanoflagellates and bicosoecids. The size distribution of HF changed with lake trophy and season, with a higher proportion of large HF (> 10 μm) in hypertrophic lakes and in spring, respectively.
4. Correlation analyses revealed a strong negative impact of cladocerans on total HF biomass and especially on large HF. Ciliates and large bacteria (> 10 μm) were strongly positively correlated with HF biomass; small bacteria (< 2 μm) showed a weak positive correlation.
5. Analyses at the level of species and genera revealed distinct distribution patterns of some taxa. Paraphysomonas , Aulacomonas and Quadricilia as large-bodied HF showed highest abundance in hypertrophic lakes and in spring. Attached taxa (e.g. Monosiga , Salpingoeca amphoridium ) were highly abundant in late summer and autumn, whereas Spumella and Kathablepharis occurred frequently in most samples.     

Methane consumption in (hyper) saline habitats of Crimea (Ukraine)

Abstract: This paper documents methane utilization in (hyper)saline environments. Methane consumption in the Crimea basins, exhibiting salinities of 8% to 33%, was as much as 1200 pmol cm⁻³ d⁻¹. This process was mainly associated with the upper layer of sediment (microbial mat), although substantial activity was also located in adjacent water. Studies of the influence of NaCl levels on the methane consumption revealed a positive correlation between optimal salt concentration and the natural salinity of the samples selected.     

Electroporation of abalone sperm enhances sperm-DNA association

The ability of sperm from the black-footed abalone Haliotis iris to take up foreign DNA in solution has been demonstrated. The efficiency of DNA uptake is related to the conditions of electroporation, including field strength (625 V cm⁻¹, 1000 V cm⁻¹), pulse length (18.6 ms, 27.4ms) and number of pulses (1, 2), and DNA concentration (20, 100 μg ml⁻¹). Sperm motility decreased with increased field strength and pulse number. At a field strength of 625 V cm⁻¹, neither the pulse length nor pulse number enhanced DNA uptake. A 40% enhancement in DNA uptake was observed when the sperm were shocked at 1000 V cm⁻¹ with two long pulses (27.4 ms each). Linear regression analysis revealed that pulse number ( p = 0.013) and field strength ( P =0.039) were the most important factors in sperm–DNA interaction. Higher DNA concentration enhanced sperm DNA uptake irrespective of field strength, pulse length and pulse number. The optimal electroporation conditions for DNA uptake were 1000 V cm', with two pulses of 27.4 ms each, and a DNA concentration of 100 μg ml⁻¹.     

Spatial patterns in aquatic vegetation composition and environmental covariates along chains of lakes in the Kokemäenjoki watershed (S. Finland)

The diversity and community structure of macrophyte vegetation was studied in 50 boreal lakes forming several upper reaches of lake chains around Lammi, southern Finland. Water chemical parameters and morphometry of the basins were included in a multivariate analysis. Floating-leaved vegetation was the dominant growth form, followed by emergent plants. In downstream lakes, the dominance of floating-leaved macrophytes declined, and emergent species increased in abundance. Species richness was highest in larger lakes, with a wider range of littoral habitats than smaller lakes. Electrical conductivity (range 18–151 mS cm⁻¹, 25 °C) of the water correlated well with patterns in diversity among lakes, but this was not the case for nutrient concentrations. As a whole, morphometrical characteristics of lake basins showed better correlations with vegetation structure than any of the measured chemical parameters. The macrophyte vegetation of neighbouring lake chains differed considerably, depending on the surrounding landscape properties, water quality of the lakes and immigration history of plant species.     

EFFECTS OF ENVIRONMENTAL CONDITIONS ON GROWTH AND LIPID ACCUMULATION IN NITZSCHIA COMMUNIS (BACILLARIOPHYCEAE)

Microalgae from natural saline habitats in the southwestern United States were isolated and screened for rapid growth potential and ability to store intracellular neutral lipid, a precursor for renewable liquid fuel sources. After preliminary screening of isolated strains, Nitzschia communis (Rabenhorst) was selected for optimization of growth rate and lipid yield. Nitzschia communis was subjected to two media types (SERI I, II) with different major ion compositions designed to mimic natural saline groundwater aquifers in the arid Southwest. Growth rates were determined through 4 days of logarithmic growth, followed by 2 days of physiological stress (nitrogen deprivation) and subsequent measurement of neutral lipid accumulation. Poststress intracellular neutral lipid increases were documented by utilizing the fluorochrome Nile Red with fluorometric analysis and epifluorescent microscopy. Growth rate was slightly higher in SERI Type I medium, whereas lipid yield was higher in SERI Type II medium. Rapid growth and appreciable lipid yields were observed over a broad range of temperatures (20°–30° C) and specific conductances (10–70 mS·cm⁻¹). The highest lipid yields were observed at elevated conductances (between 40 mS·cm⁻¹ and 70 mS·cm⁻¹). Substitution of individual salt concentrations from SERI Type II into SERI Type I medium indicated that increased lipid yield in Type I medium was associated with a reduction in MgCl₂ concentration.     

Zooplankton associations in some Ethiopian crater lakes

SUMMARY. 1. The zoopiankton associations in five crater lakes in Ethiopia were examined in April 1984. The two least alkaline lakes had the most diverse zoopiankton.
2. The large diaptomid copepod Lovenula africana was present in the lakes with alkalinities between 10 and 63 meq l⁻¹, but was absent from Lake Chitu (239 meq l⁻¹).
3. The contribution of the zoopiankton to the nocturnal deoxygenation of Lake Aranguadi is negligible.     

Microbial and classical food webs: A visit to a hypertrophic lake

Abstract: Plankton community structure and fluxes of carbon for bacteria (production and bacterivory) were investigated in the urban, hypertrophic Lake Rodó (Uruguay) using a short time interval for sampling (5–15 d) during one year. The lake sustains a high phytoplankton biomass (up to 335 μg l⁻¹ chlorophyll a ) always dominated by the filamentous cyanobacteria Planktothrix agardhii . The zooplankton community was numerically dominated by rotifers and ciliates; cladocerans were rare during most of the year. The rotifer abundance was very high (up to 10⁵ individual l⁻¹), the bacterivorous Anuraeopsis fissa being the most abundant species. Predation rates of heterotrophic nanoflagellates (HNF) on bacteria (range: 31–130 bacteria HNF⁻¹ h⁻¹) were higher than those reported in the literature for field studies. A carbon budget showed that HNF can consume on average 91 and 76% of the bacterial carbon production in summer and winter, respectively. Bacterial turnover times are the lowest reported until now from field conditions (5 to 42 h). Consequently, bacterial carbon production was extremely high (72 to 1071 μg C l⁻¹ d⁻¹). Bacterial production was positively correlated to bacterial abundance but the relationship was significantly improved by the inclusion of temperature (82% variability explained). My results support the general trend for increased bacterial production with increasing trophic status, and suggest a lower energy transfer efficiency to higher trophic levels in hypertrophic lakes due to the many trophic interactions involved.     

Factors related to gizzard shad and the threadfin shad occurrence and abundance in Florida lakes

Gizzard shad Dorosoma cepedianum were collected in 23 and threadfin shad D. petenense were collected in 22 of the 60 Florida lakes sampled. Logistic regression equations were 94% effective for predicting gizzard shad occurrence from chlorophyll and lake surface area, and 84% effective for predicting threadfin shad occurrence from lake surface area and lake volume inhabited (PVI). Occurrence of both shad species was related positively to lake size. In lakes where gizzard shad or threadfin shad were collected, shad density and biomass of both shad species were related positively to chlorophyll. Gizzard shad populations were generally vulnerable to predation in lakes, with the per cent of gizzard shad ≤200mm L _T values exceeding 60% with few exceptions. Effects of gizzard shad and threadfin shad on fish community dynamics may be confined to relatively large (>100 ha) and fertile (chlorophyll >20–30μg l⁻¹) Florida lakes.     

宁波市游览性湖泊浮游轮虫的群落结构及生物多样性

2006年10月至2007年7月,调查了宁波市东钱湖(Ⅰ、Ⅱ站)、月湖(Ⅲ、Ⅳ站)和日湖(Ⅴ、Ⅵ站)三个游览性湖泊浮游轮虫的群落结构及其生物多样性。共发现浮游轮虫21种,以月湖轮虫的密度(3287ind.·L^-1)和生物量(0.884mg·L^-1)为最高,日湖轮虫的Margalef多样性指数0.917为最高,东钱湖轮虫的群落指标均最低。东钱湖轮虫优势种为暗小异尾轮虫(Trichocerca pusilla);月湖和日湖轮虫第一优势种均为针簇多肢轮虫(Polyarthra trigla)。浮游轮虫生物多样性指数随着水体碱性环境的加剧而呈极显著地下降(r=-0.545,n=24,p<0.01),月湖和日湖的浮游轮虫生物多样性指数也随轮虫密度的增加而极显著地下降(r=-0.668,n=16,p<0.01)。     

PHYSIOLOGICAL RESPONSES TO TEMPERATURE AND IRRADIANCE IN SPIROGYRA (ZYGNEMATALES, CHAROPHYCEAE)1

Spirogyra Link (1820) is an anabranched filamentous green alga that forms free-floating mats in shallow waters. It occurs widely in static waters such as ponds and ditches, sheltered littoral areas of lakes, and stow-flowing streams. Field observations of its seasonal distribution suggest that the 70-μm-wide filament form of Spirogyra should have a cool temperature and high irradiance optimum for net photosynthesis. Measurements of net photosynthesis and respiration were marie at 58 combinations of tight and temperature in a controlled environment facility. Optimum conditions were 25°C and 1500 μmol photons m⁻² s⁻¹, at which net photosynthesis averaged 75.7 mg O₂ gdm⁻¹ h⁻¹. Net photosynthesis was positive at temperatures from 5° to 35°C at most irradiances except at combinations of extremely low irradiances and high temperatures (7 and 23 μmol photons m⁻² s⁻¹ at 30°C and 7, 23, and 35 μmol photons m⁻² s⁻¹ at 35°C). Respiration rates increased with both temperature and prior irradiance. Light-enhanced respiration rates were significantly greater than dark respiration rates following irradiances of 750 μmol photons m⁻² s⁻¹ or greater. Polynomials were fitted to the data to generate response surfaces; such response surfaces can be used to represent net photosynthesis and respiration in ecological models. The data indicate that the alga can tolerate the cool water and high irradiances characteristic of early spring but cannot maintain positive net photosynthesis under conditions of high temperature and low light (e.g. when exposed to self-shading ).     

The rotifer communities of acid-stressed lakes of Maine

The structure of the rotifer community in relation to lake pH, trophic status, the type of planktivore assemblage and the crustacean community was assessed in a survey of 23 lakes ranging in pH from 4.4 to 7.3, and in a study of two lakes — one acidic, the other circumneutral — during two summers. In both investigations the number of rotifer species encountered per sample was strongly reduced with pH. Although the reason for this is not clear acid-stress, the ultraoligotrophic nature of the acidic lakes, and competitive interactions with crustacean zooplankters may all have played a role. More importantly the ecological significance of this relationship is not known. The rotifer Keratella taurocephala was a principle species in the most acidic lakes, while several common rotifers were notably absent from these lakes. Although rotifer abundance was correlated with lake pH, the results of this study indicate that rotifer abundance is not a result of lake pH per se, but of lake trophic status and interactions with the crustacean community.     

Diel and seasonal physico-chemical fluctuations in a small natural West African lake

SUMMARY. 1. The waters of Opi Lake were very dilute (15–24 μS cm⁻¹at 25°C) and somewhat acid (pH 6.0–6.5), probably a result of the highly leached lateritic soils in its small drainage basin.
2. Annual minimum water temperatures were recorded during the early dry season, not during the rainy season as has been observed in most other West African water bodies. This was attributed to the influence of the Harmattan winds on the lake and the absence of pronounced rainy season flooding, as might occur in reservoirs.
3. A diel cycle of daytime thermal stratification and complete or near-complete night-time destratification occurred throughout the year.
4. During the dry season, when prevailing winds were strong and lake depth shallow, night-time destratification was accompanied by deep circulation. In the rainy season, when prevailing winds were weak and lake depth was greatest, deep vertical circulation apparently did not take place, as evidenced by anoxia in near-bottom waters. This is the reverse of the pattern seen in many tropical lakes.     

Oxygen consumption by eggs and larvae of striped mullet, Mugil cephalus, in relation to development, salinity and temperature

Oxygen consumption rates during embryonic and the first 38 days of larval development of the striped mullet were measured at 24° C by differential respirometry. Measurements were obtained at the blastula, gastrula and four embryonic stages, and at the yolk-sac, preflexion, flexion and post-flexion larval stages.
Oxygen uptake rates of eggs increased linearly from 0.024 μl O₂ per egg h^-1 (0·323 μl O₂ mg^-1 dry wt h^-1) by blastulae to 0·177 μlO₂ per egg h^-1 (2·516 μlO₂mg ¹dry wth^-1) by embryos prior to hatching. Respiration rates did not vary significantly among four salinities (20,25, 30, 35%₀).
Larval oxygen consumption increased in a curvilinear manner from 0·243 μl O₂ per larva h^-1 shortly after hatching to 18·880 μl O₂ per larva h^-1 on day 38. Oxygen consumption varied in direct proportion to dry weight. Mass-specific oxygen consumption rates of preflexion, flexion, and postflexion larvae did not change with age (10·838 μl O₂ mg ¹dry wt h^-1).
Larval oxygen consumption rates did not vary significantly among salinities 10–35%. Acute temperature increases elicited significant increases in oxygen consumption, these being relatively greater in yolk-sac larvae ( Q₁₀ = 2·75) than in postflexion larvae ( Q₁₀ = 1·40).