Phytoplankton responses to reduction and elimination of submerged vegetation by herbicides and grass carp in four Florida lakes

Four central Florida lakes were monitored for 3 years to determine the effects of macrophyte reduction and elimination by grass carp and herbicide on phytoplankton populations. Clear Lake, in which grass carp were stocked after a year of baseline studies, had all macrophytes eliminated within 14 months. The density of phytoplankton increased significantly from an initial 24-month mean of 165 000 cells 1⁻¹ to a mean level of 787 900 cells 1⁻¹ in the third year. In Little Lake Fairview, stocked with grass carp in both the first and third years of study, vegetation was not eliminated until the 34th month. Phytoplankton density increased significantly from a 24-month mean of 64 200 cells 1⁻¹ to a mean of 370 200 cells 1⁻¹ in the third year. Lake Orienta, stocked with grass carp in the first year, had all vegetation eliminated within 6 months. Phytoplankton abundance did not change significantly over the course of the study (mean: 2 700 000 cells 1⁻¹). Lake Mann was treated with herbicide alone after an initial year of baseline data collection. Submerged vegetation was reduced in the second year but increased to near initial biomass levels in Year 3, with Nitella sp. replacing Hydrilla verticillata (L.f.) Royle as the dominant macrophyte. No significant yearly changes were noted in density of phytoplankton in this lake. Lake Orienta was the only lake in which the number of phytoplankton species collected differed significantly between years. Cyanophytes (notably species of Anacystis, Microcystis and Anabaena) and the diatom, Fragilaria sp., predominated in all lakes as macrophytes were removed. Most changes observed were in the direction of apparent increased trophic state. Major shifts in the phytoplankton assemblage (e.g., Shannon diversity indices and abundance) coincided with periods of maximal fluctuation in vegetation. Reversals of these tendencies were observed during prolonged stable periods of both high and low macrophute biomass.     

Response of zooplankton to the reduction and elimination of submerged vegetation by grass carp and herbicide in four Florida lakes

Thirteen physical and chemical characteristics of five softwater streams in Rhode Island, U.S.A. were examined biweekly to monthly for seventeen months. One first-order, two second-order and two third-order streams were included in the study. The mean annual temperature ranged from 9.4 °C in the spring-fed headwater stream to 14 °C in an open, third-order stream, with seasonal fluctuations of 14.5 ° to 28.0 °C. The heavily shaded first-order stream generally received less than 30% incident light at its surface throughout the year. By contrast, the other streams either were unshaded or were associated with distinct periodicity of incident light quantity due to seasonality of the tree canopy. The mean annual current velocity ranged from 22 to 100 cm s^–1 among the streams, pH ranged from 3.7 to 6.4, and specific conductance was generally less than 50 µS cm^–1. The first-order stream was associated with lowest mean annual temperature, current velocity, light penetration and nitrate, as well as relatively high and constant silica concentrations. Temperature was negatively correlated with current speed in second- and third-order streams, and temperature was also negatively correlated with light in shaded streams. There was a general pattern in all streams for decreasing pH following precipitation events. Concentrations of total phophorus, nitrate-nitrogen, ammonium-nitrogen and silica were among the lowest reported for lotic systems.     

The tolerance of grass carp, Ctenopharyngodon idella Val., to aquatic herbicides

Because grass carp may feed selectively on water plants, additional conventional methods may be necessary for effective control of aquatic vegetation. For economic reasons aquatic herbicides are most likely to be used in conjunction with grass carp within an integrated aquatic weed control programme. The acutely lethal toxicities of ten herbicides to grass carp were measured. A preliminary evaluation of the risk to these fish showed that, when used at the recommended rate, the maximum herbicide concentration likely to be found in water should cause little harm to the fish, although attention should be given to the possible inhibition of feeding.     

The effects of wildfire on the water chemistry of dilute,acidic lakes in southern Norway

Changes in lake water chemistry were studied for >4 years following a large wildfire in a boreal forest area in Mykland, southern Norway, an area characterized by thin and patchy, base-poor and slow-weathering soils and bedrock. Accordingly, the lakes have low acid neutralizing capacity (ANC), calculated as the difference between the total concentration of base cations ([ΣBC]) and strong acid anions ([SAA]). During the initial post-fire period, and peaking about two months after the fire, the mobilization of SAA from terrestrial to aquatic systems caused a dramatic drop in ANC. In one of the lakes, ANC dropped from about 20 to ?80 μeq L^?1, while [H⁺] and inorganic aluminum ([Al_i]) increased to 38 μeq L^?1 (pH 4.42) and 326 μg Al L^?1 (36.2 μeq L^?1 as Al³⁺), respectively. Sulfate and chloride were the predominant anions responsible for this decline in ANC, as the nitrate increase was small. After the severe chemical episode, [SAA] in the lakes declined faster than [ΣBC], and within about one year after the wildfire, ANC was back to almost pre-fire values. However, despite the fact that [SAA] also continued to decline faster than [ΣBC] the following years, no further increase in ANC was documented. The strong ionic strength decline and the increase in TOC during the same period have likely counteracted for the potential ANC increase. There were large lake-to-lake variations in water chemistry of the wildfire affected lakes. Hydrology, geology, lake residence time and the catchment area to lake area ratio are important explanatory factors.     

The destruction of aquatic vegetation by carp

The destruction of submerged vegetation by common carp, Cyprinus carpio L. is tested in six enclosures with different biomass (kg ha^?1) of carp in a marsh of the Camargue, southern France. After 71 days, a strong negative relationship was found between the biomass of carp and the amount of aquatic vegetation present in the enclosures. The results are compared with similar studies in the United States. The absence of problem of vegetation destruction by carp in Europe, in contrast to North America, may be explained by lower biomass of these populations in Europe, and by a higher weight of carp in North America.     

湖泊水位变动对水生植被的影响机理及其调控方法

水位的高低及其变动范围、频率、发生的时间、持续的时长和规律性等是影响湖泊水生植被的核心因子.水位变动有短期、年内季节性和年际变动3种,对湖泊水生植被有不同的影响机理.水位短期变动通过对水体中的悬浮物、透明度、光衰减系数等的影响而对水生植被产生作用;周期性的年内季节性和年际水位变动可对水生植被的生态适宜性产生影响,并进而改变其时空分布;长期的高水位和低水位以及非周期性的水位季节变动会破坏水生植被长期以来对水位周期性变化所产生的适应性,从而影响了植被的正常生长、繁衍和演替.植被的极端深度和物种多样性是水位调控的核心表征指标,可通过经验数据分析法、生态模型法和参照法等方法来确定湖泊的适宜水位变动范围和时间.研究对象选择、研究方法、管理中的应用以及重要环境变化所产生的影响等是今后相关研究的核心问题.     

The outcome of the invasion of Florida lakes by Daphnia lumholtzi

1. We examined 7–12 years of monthly to quarterly historical data from 15 lakes in FL, U.S.A. to determine the extent and outcome of invasion by the alien cladoceran Daphnia lumholtzi Sars. 2. The alien species was found in 10 of the 15 lakes, including Florida’s three largest lakes: Okeechobee, George and Apopka. All the surveyed lakes had resident populations of the smaller native species Daphnia ambigua Scourfield. 3. In most of the lakes, D. ambigua occurred seven to ninefold more often in plankton samples than D. lumholtzi, and at 10‐ to 100‐fold higher maximal densities. One exception was a small lake in central Florida (Lake Jesup), where D. lumholtzi attained high densities on several occasions in the 10 years of sampling. 4. In Lake Okeechobee, where data were of sufficient quality and quantity to perform statistical analyses, the results of canonical correlation analysis indicated that high densities of D. lumholtzi were correlated with lower concentrations of suspended solids, high algal biomass and higher temperature, whereas the opposite conditions were correlated with high densities of D. ambigua. 5. Based on the majority of data, D. lumholtzi has successfully invaded many lakes in Florida, yet it has not become a substantive component of the zooplankton. Additional research is needed to determine whether resources, fish predation or some other factor is responsible for this outcome of invasion.     

Microbiology and chemistry of acid lakes in Florida: II. Seasonal relationships

The microstratification of the metalimnetic community in Lake Cisó was followed through the diel cycle by means of a fine sampler with syringes spaced at 3 cm intervals. Populations were sharply stratified. The uppermost part of the metalimnion was occupied by the rotifer Anuraeopsis fissa. Next, layers of the ciliate Coleps hirtus and the flagellate Cryptomonas phaseolus were found. Finally, purple sulfur bacteria appeared at the bottom part of the metalimnion. Although in lower abundances, characteristic populations of ciliates were found at each depth: Strombidium inhabited zones with oxygen, while Plagiopyla and Metopus lived at depths with sulfide. Several members of the community moved vertically about 20 cm during the diel cycle. Cryptomonas performed larger vertical migrations of 40 cm. This organism concentrated at the upper metalimnion during the day, and dispersed through the lower metalimnion during the night. At night, Cryptomonas lived in an environment without oxygen and with sulfide concentrations up to 0.6 mM.     

Effect of photosynthetic bacteria on water quality and microbiota in grass carp culture

To investigate the effects of photosynthetic bacteria as additives on water quality, microbial community structure and diversity, a photosynthetic purple non-sulfur bacteria, Rhodopseudamonas palustris, was isolated and used to remove nitrogen in the aquaculture water. The results of water quality showed that the levels of ammonia nitrogen, nitrite nitrogen, total inorganic nitrogen and total nitrogen in the treatment group were significantly lower (p < 0.05) than the nitrogen levels of the controls in an extended range. A 454-pyrosequencing analysis revealed that at the level of phylum, Proteobacteria and Firmicutes were dominant in the control group respectively, compared to the dominance of the phyla Proteobacteria, Bacteroidetes and Actinobacteria in the treatment group. The relative abundance of phyla Bacteroidetes and Actinobacteria in treatment witnessed an increase than that in the control. The results also indicated that the treatment group enjoyed a higher microbial diversity than that of the control group. Based on the oxygen requirement and metabolism, the authors observed that the water supplementation with photosynthetic bacteria could significantly decrease (p < 0.05) the number of nitrite reducer and anaerobic bacteria. Therefore, the results suggested that adding photosynthetic bacteria to water improves the water quality as it changes the microbial community structure.     

食物与水环境因子对草鱼(Ctenopharyngodon idellus C.et V)脆化过程的影响

结合生产实际,探讨了普通鲩鱼向脆肉鲩转变的过程和实质,提出用“断裂应力δρ”作为脆肉鲩脆化程度的划分标准,并实验研究了不同水温、水流速度、水化学因子和蚕豆饲料投喂量等因素对脆肉鲩生长和品质的影响。结果表明,以脆肉鲩不同部位组织热变性蛋白质的断裂应力δρ为指标的脆化程度主要由蚕豆饲料摄食量所决定,脆肉鲩养殖的良好条件为:放养规格1.50~2.00 kg/尾,放养密度150~170尾/666.7 m2,,水温在18℃以上;摄食量达到3.962~5.263 kg/kgbw时,可实现饲料系数约为6,脆化程度指标δρ为0.422~0.611 kg/cm2的合格商品脆肉鲩。水体水化学因子等环境条件只对草鱼脆化起间接辅助作用,它们通过改变草鱼的摄食量和营养(能量)转化率,影响机体正常的生理活动而导致草鱼肌肉蛋白合成与积累不同等表达出来,良好的水环境质量利于脆肉鲩养殖。普通鲩鱼脆化养殖的最佳养殖条件为适当的饲料投喂剂量(4.3kg/kgbw),适宜的水环境因子条件(水温(30±2)℃、DO≥5mg/L、pH在5.8~6.2之间)。为进一步完善脆肉鲩养殖生产操作流程,提高脆肉鲩养殖技术,合理调控投饲量和养殖水环境因子,从而提高脆肉鲩品质和养殖效益进行了讨论。     

Lime treatment and its effects on the chemistry and biota of hardwater eutrophic lakes

1. The main focus of this study was to investigate the effects of single and multiple moderate doses of lime (slaked lime, Ca(OH)₂, and/or calcite, CaCO₃) on eutrophic hardwater lakes. This information would contribute to strategies to manage phytoplankton and macrophyte biomass in eutrophic lakes.
2. Water chemistry and biota were monitored for up to 7 years after initial lime treatment and results were compared with reference systems.
3. Complementary studies investigated the effect of lime on macrophytes in ponds, irrigation canals and microcosm experiments.
4. When water pH was kept within its natural range (≤ 10), single and multiple lime applications to lakes and ponds controlled macrophyte biomass, without negatively affecting invertebrate communities.
5. Single lime treatments at moderate dosages of lakes and ponds resulted in variable and mostly temporary changes in chlorophyll a (chl a ) and phosphorus (P) concentration. Although sediment P release was reduced in single-dose lakes during the first winter following treatment, reductions appeared temporary.
6. Multiple treatments of lakes and ponds were effective at reducing both chl a and P concentrations over longer periods. Mean winter P release rate was also reduced after initial treatment.
7. In laboratory studies, sediment cores were incubated with eight different treatments to assess P release. Redox-sensitive treatments were no more effective at lowering total P concentration in overlying water than some redox-insensitive treatments. Lime reduced total P concentrations, but was not as effective as treatments with alum.
8. The use of lime in managing macrophyte and phytoplankton biomass in shallow, hardwater lakes and ponds may be preferable over other treatments, because lime is economical and non-toxic as long as pH is kept within a natural range.     

Characterizations of four toll‐like receptor 4s in grass carp Ctenopharyngodon idellus and their response to grass carp reovirus infection and lipopolysaccharide stimulation

In this study, the subcellular localization, tissue distribution and response to grass carp reovirus (GCRV) infection and lipopolysaccharide (LPS) stimulation of four grass carp Ctenopharyngodon idellus toll‐like receptor 4 (tlr4) genes were investigated. All four genes were constitutively expressed in all tissues studied, but the subcellular localization and tissue exhibiting the highest expression differed for each protein. Following GCRV infection, all the four tlr4s were upregulated in all tissues examined, and stimulation of C. idellus kidney (CIK) cells with LPS resulted in downregulation of all four tlr4s. These results provide a foundation for further investigation of tlr4 genes in bony fishes.     

The relationships of vegetation to surface water chemistry and peat chemistry in fens of Alberta,Canada

The relationships between vegetation components, surface water chemistry and peat chemistry from 23 fens in boreal Alberta, Canada, substantiate important differences along the poor to rich fen gradient. Each of the three fen types have their own characteristic species. The extreme-rich fens are characterized by Calliergon trifarium, Drepanocladus revolvens, Scirpus hudsonianus, S. cespitosus, Scorpidium scorpioides, and Tofieldia glutinosa. Moderate-rich fens are characterized by Brachythecium mildeanum, Carex diandra, Drepanocladus vernicosus, D. aduncus, and D. polycarpus. Poor fens are characterized by Carex pauciflora, Drepanocladus exannulatus, Sphagnum angustifolium, S. jensenii, and S. majus. Moderate-rich fens have fewer species in common with poor fens than with extreme-rich fens, while species richness is highest in the moderate-rich fens and lowest in poor fens. Variation in vascular plant occurrence appears to be more associated with nutrient levels, while bryophytes are more affected by changes in acidity and mineral elements. Based on chemical criteria, the three fen types are clearly separated by surface water pH, calcium, magnesium, and conductivity, but are less clearly differentiated by the nitrogen and phosphorus components of the surface waters. Moderate-rich fens are chemically variable both temporally and spatially, whereas poor fens and extreme-rich fens are more stable ecosystems. Whereas components of alkalinity-acidity are the most important factors that distinguish the three fen types in western Canada, nutrient concentrations in the surface waters generally do not differ appreciably in the three fen types.     

Multivariate analysis of diatoms and water chemistry in Bolivian saline lakes

Diatom assemblages are described from surface sediments in thirteen salt lakes located in the southern Bolivian Altiplano. Factor analysis of correspondences and cluster analysis are used to classify the diatom assemblages. New methods are proposed to establish the qualitative and quantitative relationships between diatom floras and ecological parameters. Diatom assemblages are linked more to the ionic elements than to the salinity, pH, depth, temperature or elevation. Environmental variables are divided into three modalities which allow considerations of many different variables not under the same units.     

Effects of planktivorous and benthivorous fish on organisms and water chemistry in eutrophic lakes

The effects of planktivorous and benthivorous fish on benthic fauna, zooplankton, phytoplankton and water chemistry were studied experimentally in two eutrophic Swedish lakes using cylindrical enclosures. In enclosures in both lakes, dense fish populations resulted in low numbers of benthic fauna and planktonic cladocerans, high concentration of chlorophyll, blooms of blue-green, algae, high pH and low transparency. In the soft-water Lake Trummen, total phosporus increased in the enclosure with fish, but in the hard-water Lake Bysjön total phosphorus decreased simultaneously with precipitation of calcium carbonate. Enclosures without fish had a higher abundance of benthic fauna and large planktonic cladocerans, lower phytoplankton biomass, lower pH and higher transparency.The changes in enclosures with fish can be described as eutrophication, and those in enclosures without fish as oligotrophication. The possibility of regulation of fish populations as a lake restoration method is discussed.This paper was presented at the XXth SIL Congress in Copenhagen in 1977.     

Microbiology and chemistry of acid lakes in Florida: I. Effects of drought and post-drought conditions

Short term changes in acid loading and dissolved organic carbon (DOC) content were studied in relation to water column bacteria of ten acid lakes on the Katharine Ordway Preserve, Florida. Five clear oligotrophic lakes and five dark dystrophic lakes were sampled during and after a drought period in July and September, 1985. Water column bacterial densities, light extinction, chlorophyll a, DOC, pH, dissolved oxygen, nutrients, and other chemical variables were measured. Significant positive correlations existed among DOC, chlorophyll a, pH, and water column bacterial densities during the drought period.There were no significant changes in water column bacterial densities or pH of clear lakes in the post-drought period, despite a 4.6 fold increase in acid loading from rainfall. A 3 fold increase of DOC, a decline in pH, and decreased bacterial densities in dark lakes suggested inhibition of bacteria by DOC and pH. A decrease in the relationship of DOC to bacterial numbers in all lakes was also noted. The correlations among DOC, chlorophyll a, and pH were no longer significant.Using data from both time periods significant polynomial regressions were observed between DOC and bacterial density and DOC and chlorophyll a. Maximum bacterial numbers occurred at 20 mg C 1^–1 of DOC. Above this bacterial numbers decreased also suggesting an inhibitory effect of DOC. Because pH was lower after DOC had increased in the dark lakes, the increase in acid conditions may have enhanced this inhibitory effect. The short term effects of DOC on the dark-lake bacteria greatly exceeded the influence of acid loading on clear-lake bacteria.     

Food consumption, growth and survival of grass carp Ctenopharyngodon idella Val at four salinities

Grass carp were raised in 227-1 indoor tanks at 3,5,7 and 9%osalinities and 18·5 and 29·5°C temperatures at a density of five fish per tank. Growth rate did not differ under these conditions. Food consumption was similar between temperatures at a given salinity but differed among the salinities with most food intake at the 5%o salinity. An average of 40% of grass carp survived for 180 or more days.     

Spring fen vegetation and water chemistry in the Western Carpathian flysch zone

In the western part of the Carpathian flysch zone, aquifers host several springwater chemistry types. Four vegetation types, distinguished along the poor-rich gradient (tufa-forming and peat forming brown moss fens, moderately rich and poorSphagnum fens), have been compared with respect to the main habitat factors. Water calcium and magnesium concentrations, pH and conductivity as well as the soil organic carbon content were the properties measured that showed the strongest correlation with the main vegetation gradient (the poor-rich gradient). Further, significant differences in iron, sodium, potassium, sulphate and phosphate concentrations were also found between pairs of related vegetation types. The range of calcium concentrations is wide (2–300 mg/l). The calcium concentration in tufa-forming springs is higher than values usually reported from northern and western Europe. Tufa formation is influenced not only by high calcium concentrations, but also by the total chemical composition of springwater and both climatic and topographic conditions. There is a great excess of cations over Cl⁻ and SO ₄ ²⁻ , balanced by HCO ₃ ⁻ and CO ₃ ²⁻ in springs with the most intense tufa precipitation. Unusually high calcium concentrations combined with high iron concentrations were found in peat-forming brown moss fens. RichSphagnum-fens with calcitolerantSphagnum species are distinctively low in phosphates. The Western Carpathian poor fens dominated bySphagnum flexuosum have water and soil calcium concentrations comparable to those reported from rich fens of some other areas. The springwater of these fens are rich in iron, phosphates and sulphates. The poorest spring fens withSphagnum fallax, S. magellanicum, S. papillosum andS. auriculatum are not only poor in calcium, but also in iron, sodium and potassium.