Lipid and reproductive cycles of bluegills (Lepomis macrochirus) exposed to 35 years of elevated environmental temperatures

1. We studied bluegills to compare how thermal perturbation affected lipid dynamics and reproductive cycles of fish from heated (Pond C) and normothermic (Par Pond) sites.

2. Bodies of bluegills contained over 90%, and gonads and livers 10% of the non-polar lipids.

3.Overall, the percent body lipids of bluegills from the heated pond was twice as high (12.4%) as that of Par Pond bluegills (6.6%).

4. During a prolonged reactor down period, when both ponds were normothermic, body lipids of bluegills from Pond C and Par Pond increased at a rate of approximately 3 and 1% of body mass per week, respectively.

5. Juveniles from Pond C had higher percent stored lipids than did adult males or females.

6. Lipid cycling in Par Pond bluegills was seasonal, whereas Pond C bluegill lipid cycles corresponded to long reactor down periods.     

Responses of the Phytoplankton Community of a Tropical Reservoir (São Paulo,Brazil) to the Enrichment with Nitrate,Phosphate and EDTA

The effects of artificial enrichment with nitrate, phosphate and EDTA on the phytoplankton community were studied in the Lobo Reservoir (São Paulo, Brazil). After 14 days of in situ incubation, the amounts of suspended matter and chlorophyll a, the numbers of cells and the carotene/chlorophyll ratio were determined. The addition of nitrate and phosphate to water samples produced significant effects on the chlorophyll a and cell counts, while EDTA acted only on the cell production. Both nitrate and phosphate, when analysed individually, caused a decrease in the value of the carotene/chlorophyll ratio. A synergistic effect of the addition of EDTA and N on the suspended matter was observed.     

The Effect of Theoretical Retention Time on the Hydrodynamics of Deep River Valley Reservoirs

The one‐dimensional numerical simulation model of reservoir hydrodynamics, DYRESM, is used to examine the effects of Retention Time (RT) on reservoir stratification. The model is verified using data from 3 years of high flow (short retention time, RT), on two reservoirs in the Czech Republic. The verified model was used to make a systematic series of simulations with varying RT, outlet location and inflow temperature in order to gauge the affect on heat budgets, temperature stratification, flows and mixing in deep valley reservoirs. The prototype examples corresponded to two temperate and one subtropical reservoir. The results show important effects of RT on reservoir hydrodynamics up to RT = 200, but a leveling off for RT > 400. Temperature stratification and hydrodynamic conditions are shown to be very sensitive to the inflow temperature and outlet depth. Results indicate that the energy released by large inflows is a major factor in determining the degree of mixing, and hence lower RT values lead to a weaker stratification in general. However, the height of withdrawal can have a significant impact on overall temperature and hence stratification. For example, large withdrawals from a deep outlet can lead to a reservoir with warmer average temperature by removing large amounts of cooler bottom water. Similarly, surface withdrawals may remove warmer water leading to a cooler average temperature. These effects are moderated by inflow temperatures and surface heat exchanges. In this paper an attempt is made to quantify these effects and come up with some general rules of thumb as to how different management strategies might influence the reservoir's average structure.     

鄂西三峡库区大老岭珍稀树木群落特征研究

在群落数量特征、群落层次频度、群落物种多种性等３个层次上对分布在宜昌大老岭国家森林公园保护区的光叶珙桐（Ｄｕｖｉｄｉａ ｉｎｖｏｌｕｃｒａｔａ ｖａｒ ｖｉｌｍｏｒｉｎｉａｎａ）、领春木（Ｅｕｐｔｅｅｌｅａ ｐｌｅｉｏｓｐｅｒｍａ）、紫茎（Ｓｔｅｗａｒｔｉａ ｓｉｎｅｎｓｉｓ）、白辛（Ｐｔｅｒｏｓｔｙｒａｘ ｐｓｉｌｏｐｈｙｉｌａ）等珍稀群落进行了定性和定量的研究,弄清了群落群成、结构、揭示了群落     

Some characteristics of a pike Esox lucius L. population in an Irish reservoir

A study of a stocked upland reservoir trout fishery, using gill nets, revealed the presence of a large stock of pike and poor trout numbers. The overall growth rate of pike was slow. Two year-classes of pike dominated, but the broad age and length frequency ranges, and the high average weight of individuals were indicative of an unexploited stock. Higher than normal water levels during the spawning period and into the summer period in both 1985 and 1986, coincided with the dominant pike year-classes recorded several years later. This revised version was published online in July 2006 with corrections to the Cover Date.     

Studies on the hydrochemistry of Kangimi reservoir, Kaduna State, Nigeria

The physicochemical characteristics of Kangimi reservoir were investigated monthly at two stations of the reservoir between July 1998 and September 1999. This was done to determine if acceptable water quality standards are being maintained in the reservoir and to assess if the water could maintain a thriving fishery. All the physicochemical parameters investigated fell within the range of allowable standards for potable waters according to the World Health Organization ( WHO, 1993 ). Alkalinity, conductivity, nitrate‐nitrogen and phosphate phosphorus showed significantly higher (P < 0.05) values during the rains, which was associated with surface runoff, whereas dissolved oxygen, hardness, transparency and chlorophyll‐a showed significantly higher values (P < 0.05) during the dry season. The reservoir was indicated to be oligotrophic. The biological significance of these findings are discussed.     

The phytoplankton community of a eutrophic reservoir

The dynamics of the phytoplankton community of a eutrophic reservoir are described for a two year period. Fifty-eight species were recorded, 25 of them common. Bacillariophyta dominated during the winter and early spring and Chlorophyta during late spring, to be replaced by a bloom of Cyanophyta. The mean and peak biomass of phytoplankton was 8.6 mg 1^–1 and 40.8 mg 1^–1 in 1981, and 8.3 mg 1^–1 and 37.6 mg 1^–1 in 1982. Temperature accounted for 67.3% and pH for 8% of the variation in total phytoplankton biomass over the two year period, using a multiple regression technique.Both horizontal and vertical patchiness, measured as an index of mean crowding, were recorded in the reservoir. Horizontal aggregations were associated with spring blooms of Chlorophyta and summer blooms of Cyanophyta, while vertical aggregations were most marked during the summer bloom of Cyanophyta. Concentrations of phytoplankton were influenced by wind, the prevailing southwesterly wind accumulating algae in the northeasterly arm of the reservoir during much of the year.     

Chironomidae communities of the near-shore zone in Zegrzyńsky Reservoir,Poland

The structural differences in chironomid communities of the near-shore zone in Zegrzyski Reservoir corresponded to variations in sediments composition. Sandy bottom areas covered by a thin layer of mud were inhabited mostly byPolypedilum, Cryptochironomus andGlyptotendipes larvae.Cladotanytarsus andStictochironomus were often the most numerous in the shallower zone (0.2–0.5 m). Predatory Tanypodinae were found most commonly on the sandy bottom covered by well mineralized plant debris and loose silt. Extremely high numbers and biomass ofChironomus andGlyptotendipes larvae occupied the clay bottom covered by a thick layer of mud. On the basis of developmental stage distribution it was found that at least three generations ofChironomus andGlyptotendipes occurred during the study period (April–October 1988). The combined production estimate for these two taxa exceeds any reported for Chironomidae in lentic or lotic habitats.     

The spatial distribution of Borrelia burgdorferi-infected Ixodes ricinus in the Connemara region of County Galway,Ireland

Studies were carried out in the Connemara area of County Galway in the west of Ireland in order to determine the abundance and distribution of the tick, Ixodes ricinus and the prevalence of its infection with Borrelia burgdorferi. The tick was very abundant locally, in particular when associated with cattle, sheep and enclosed red deer. Large numbers of ticks not only occurred on the pastures, but also on adjacent roadside verges. No infections with B. burgdorferi could be demonstrated when nymphal ticks were sampled from central areas of the pastures, suggesting that livestock and red deer are probably not significant reservoirs of the spirochaete. Small numbers of infected nymphal and adult ticks were associated with hedges, dry stone walls, the margins of woodland adjoining infested pastures and in woodland from which livestock were excluded. Woodmice (Apodemus sylvaticus) were most numerous in such habitats and the majority were infected with B. burgdorferi.     

Effets de la mise en eau du réservoir Desaulniers (Territoire de la Baie de James) sur le zooplancton d'une rivière et d'une tourbière reticulée

This paper presents the results of an investigation which lasted three years, on the effects of impounding a river on its zooplankton community. Forty zooplankton samples were collected from the Desaulniers River and from a string bog (53°35N, 77°35W) in 1976 before impoundment. Sampling was also conducted in 1977 (331 samples) and 1978 (153 samples) during and after impoundment. The population dynamics of zooplankton show different patterns in 1977 and 1978. The main impacts of impoundment on the river and the bog communities are the increase of the population density, particulary of Rotifera and Copepoda, the increase of the number of species of Rotifera and the increase of the diversity indices based on numbers and biomass. These changes are observed at each sampling station. The total biomass increases in lotic stations but decreases in the string bog because the density and the biomass of Cladocera increases in the river but drops in the bog. Results are compared to those obtained in natural lakes and bog of the same area and to those published in other studies.

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Effets de la mise en eau du réservoir Desaulniers (Territoire de la Baie de James) sur le zooplancton d'une rivière et d'une tourbière reticulée