Exoenzimas em rações de frangos de corte

The study aimed to evaluate performance, relative weight of the small intestine, digestibility and deposition of minerals in the bone of broilers supplemented with enzymatic complex (carbohydrases and phytase) in sorghum-based diets or sorghum and millet. In the experiments based of sorghum and sorghum and millet were used 912 day-old male and female Hubbard Flex chicks (50:50) were distributed in a completely randomized design in a 2x2 factorial arrangement (Feed Control base Sorghum (Contcs); FeedReducedbase Sorghum (RedS); Feed Control base sorghum + Enzymatic Complex (Contcs + Enz);. Feed reduced base sorghum + Enzymatic Complex (RedS + Enz) in the study of feed basis of sorghum and millet the design was similar (Feed Control base sorghum + millet ( ContSM); Reduced feed based on Millet + Sorghum (RedSM); Feed Control based Sorghum + Millet + EnzimaticComplex (ContSM + Enz); Reduced Feed base Sorghum+ Millet + Enzimatic Complex (RedSM + Enz). At 35 and 42 days of age were determined performance data: feed intake (CR), body weight (BW), feed conversion (FC), viability (VIAB), relative weight of the small intestine and deposition of minerals in the bone. The digestibility was evaluated sorghum grain size (crushed and whole) with and without exoenzimatico complex. They used 32 birds, eight birds per treatment, in periods from 17 to 21 (initial) and 31 to 35 days of age (fattening). The exoenzimático complex used in feed favored the weight gain results, feed conversion and bone mineralization when compared to a control diet not added to enzymes, demonstrating its effect on non-starch polysaccharides and phosphorus phytic present as anti-nutritional factors in these diets, increasing the digestibility and supply of metabolizable energy, essential amino acids, methionine and lysine and calcium and phosphorus for bone formation. It is concluded that a safe strategy for inclusion in feed is based on the reduction of energy levels, essential amino acids, methionine and lysine and calcium and phosphorus in the expected result of the constant activity of the enzymes of this exoenzimático complex.

(Supplement 1) Selected chemical composition of Icelandic river waters and bedrock age

In this study we map the spatial distribution of selected dissolved constituents in Icelandic river waters using GIS methods to study and interpret the connection between river chemistry, bedrock, hydrology, vegetation and aquatic ecology. Five parameters were selected: alkalinity, SiO2, Mo, F and the dissolved inorganic nitrogen and dissolved inorganic phosphorus mole ratio (DIN/DIP). The highest concentrations were found in rivers draining young rocks within the volcanic rift zone and especially those draining active central volcanoes. However, several catchments on the margins of the rift zone also had high values for these parameters, due to geothermal influence or wetlands within their catchment area. The DIN/DIP mole ratio was higher than 16 in rivers draining old rocks, but lowest in rivers within the volcanic rift zone. Thus primary production in the rivers is limited by fixed dissolved nitrogen within the rift zone, but dissolved phosphorus in the old Tertiary catchments. Nitrogen fixation within the rift zone can be enhanced by high dissolved molybdenum concentrations in the vicinity of volcanoes. The river catchments in this study were subdivided into several hydrological categories. Importantly, the variation in the hydrology of the catchments cannot alone explain the variation in dissolved constituents. The presence or absence of central volcanoes, young reactive rocks, geothermal systems and wetlands is important for the chemistry of the river waters. We used too many categories within several of the river catchments to be able to determine a statistically significant connection between the chem¬istry of the river waters and the hydrological categories. More data are needed from rivers draining one single hydrological category. The spatial dissolved constituent distribution clearly revealed the difference between the two extremes, the young rocks of the volcanic rift zone and the old Tertiary terrain.

Seawater carbonate chemistry, structural and chemical characteristics of the seagrass Thalassia testudinum in an situ CO2 enrichment experiment

Seagrasses commonly display carbon-limited photosynthetic rates. Thus, increases in atmospheric pCO2, and consequentially oceanic CO2(aq) concentrations, may prove beneficial. While addressed in mesocosms, these hypotheses have not been tested in the field with manipulative experimentation. This study examines the effects of in situ CO2(aq) enrichment on the structural and chemical characteristics of the tropical seagrass, Thalassia testudinum. CO2(aq) availability was manipulated for 6 months in clear, open-top chambers within a shallow seagrass meadow in the Florida Keys (USA), reproducing forecasts for the year 2100. Structural characteristics (leaf area, leaf growth, shoot mass, and shoot density) were unresponsive to CO2(aq) enrichment. However, leaf nitrogen and phosphorus content declined on average by 11 and 21 %, respectively. Belowground, non-structural carbohydrates increased by 29 %. These results indicate that increased CO2(aq) availability may primarily alter the chemical composition of seagrasses, influencing both the nutrient status and resilience of these systems.

Seawater carbonate chemistry and biological processes of Emiliania huxleyi (PML B92/11) during experiments, 2011

The present study investigates the combined effect of phosphorous limitation, elevated partial pressure of CO2 (pCO2) and temperature on a calcifying strain of Emiliania huxleyi (PML B92/11) by means of a fully controlled continuous culture facility. Two levels of phosphorous limitation were consecutively applied by renewal of culture media (N:P = 26) at dilution rates (D) of 0.3 d- and 0.1 d-1. CO2 and temperature conditions were 300, 550 and 900 µatm pCO2 at 14 °C and 900 µatm pCO2 at 18 °C. In general, the steady state cell density and particulate organic carbon (POC) production increased with pCO2, yielding significantly higher concentrations in cultures grown at 900 µatm pCO2 compared to 300 and 550 µatm pCO2. At 900 µatm pCO2, elevation of temperature as expected for a greenhouse ocean, further increased cell densities and POC concentrations. In contrast to POC concentration, C-quotas (pmol C cell-1) were similar at D = 0.3 d-1 in all cultures. At D = 0.1 d-1, a reduction of C-quotas by up to 15% was observed in the 900 µatm pCO2 at 18 °C culture. As a result of growth rate reduction, POC:PON:POP ratios deviated strongly from the Redfield ratio, primarily due to an increase in POC. Ratios of particulate inorganic and organic carbon (PIC:POC) ranged from 0.14 to 0.18 at D = 0.3 d-1, and from 0.11 to 0.17 at D = 0.1 d-1, with variations primarily induced by the changes in POC. At D = 0.1 d-1, cell volume was reduced by up to 22% in cultures grown at 900 µatm pCO2. Our results indicate that changes in pCO2, temperature and phosphorus supply affect cell density, POC concentration and size of E. huxleyi (PML B92/11) to varying degrees, and will likely impact bloom development as well as biogeochemical cycling in a greenhouse ocean.

Efeitos da dieta hipoprotéica na formação e composição de estruturas dentárias: estudo experimental em ratos Wistar

Protein and caloric malnutrition has been considered one of the most concerned endemic diseases in Brazil and in the world. It has been known that depletion or reduction of proteins as far as meals are concerned can steer irreversible damages upon several organic systems. This study had as aim evaluate the effects the low-protein diet had over the formation and composition of the teeth components. 18 females and 6 males were used for the experiment. 12 from the 18 females had undertaken the low-protein diet (DH) for 03 weeks and the other 6, which remained, and those males had undertaken a controlled diet (DC) for the same period. All animals had the diets during their mating, pregnancy and lactation cycle. As soon as the offsprings had been born, 10 young males and females of each group faced a disease hood analysis to check the teeth germs of their lower fore teeth. The rest of the group had their lactation cycle normally 60 days. Then they were put to death and had their lower fore teeth removed both to be analyzed through a scanning electronic microscopy (SEM) of the structure alterations and to have their calcium checked by an atomic absorption of the phosphorus vanadate-molibdate method and by other minerals EDX method. The animals livers were removed to have their hepatic proteins analyzed as well. The histopatologic study showed that at first day of birth, all animals had their lower fore teeth come out. It was verified that 90% of the animals teeth were in an apposition and calcification period and it was possible to observe the dentin formation from 60% of the 90% already mentioned. Through the SEM method it could be realized that 90% of the animals of the DH group had their lower fore teeth easily broken and no definite shape. In this same group itself, it was also observed long micro fissures 369,66 nm ± 3,45 while the DC group had fissures of 174 nm ± 5,72. Now regarding the calcium and phosphorus concentration, it could be noticed that there was a great reduction of these components and other minerals in the DH group. Almost all minerals, except for the Cl and K, presented higher levels in the DC group enamel.The reduction of the protein input greatly influenced the offsprings´ weight and height. However the hepatic proteins had no important difference between the groups what can make one believe that those animals suffered from protein malnutrition of marasmic kind

Deficiencias minerales en bovinos para carne: diagnóstico, caracterización y control

La demanda de una producción de alimentos cada vez mayor a nivel mundial sumado a la tecnificación y al ritmo acelerado del progreso de las explotaciones agropecuarias actuales hacen que el ganado deba soportar elevadas presiones de producción aumentando los requerimientos de nutrientes. Este es el caso de los minerales considerados actualmente elementos esenciales para los animales, aunque tradicionalmente fueron definidos como los nutrientes pobres de la nutrición y alimentación animal. Actualmente se ha demostrado con evidencia clínica y productiva, el importante rol metabólico de los minerales en el animal sano y productivo, como también se ha definido qué elemento mineral y porcentaje del mismo es requerido para el normal funcionamiento del organismo. Los macro-minerales (calcio, magnesio, fósforo, sodio, potasio, cloro y azufre) y los oligo-minerales (cobre, zinc, hierro, selenio, cobalto, iodo, manganeso, molibdeno y cromo) son elementos esenciales y necesarios para transformar la proteína y la energía de los alimentos en componentes del organismo o en productos animales como leche, carne, crías, piel, lana. Además, ayudan al organismo a combatir las enfermedades, manteniendo al animal en buen estado de salud. Se ha considerado a los minerales como el tercer grupo limitante en la nutrición animal, siendo a su vez, el que mayor potencial y menor costo tiene para incrementar la producción del ganado. Los minerales desempeñan funciones tan importantes como ser constituyentes de la estructura ósea y dental, de tejidos blandos y líquidos corporales. Están involucrados en el funcionamiento celular, siendo activadores de más de trescientas enzimas, constituyentes esenciales de vitaminas, hormonas y pigmentos respiratorios y facilitando la actividad de los microorganismos del rumen. Cuando el aporte de minerales en la ración no es el adecuado en calidad y/o cantidad se originan las deficiencias minerales, encuadradas dentro de las enfermedades metabólicas o enfermedades de la producción. Estas han sido informadas en casi todo el mundo y son responsables de importantes pérdidas económicas en los rodeos de bovinos para carne. Las deficiencias y/o desequilibrios minerales pueden causar los siguientes trastornos en los animales: bajo porcentaje de parición, mayor número de servicios por concepción, abortos, retenciones placentarias, incremento del intervalo entre partos, baja producción de leche, menor peso al nacimiento y al destete, menor porcentaje de destete, menor ganancia de peso, mayor incidencia de enfermedades infecciosas, fracturas espontáneas, diarrea, deformación de huesos y mortandad. Así cobra importancia el diagnóstico mediante el análisis de la sangre de los animales, del pasto y el agua que consumen y la caracterización de estas deficiencias en primarias o secundarias con el objetivo de poder realizar un control de las mismas mediante un adecuado plan de suplementación mineral acorde a las necesidades de los distintos establecimientos agropecuarios.

Desempenho de juvenis de tilápia-do-nilo alimentados com rações contendo complexo enzimático

Avaliou-se o efeito da inclusão de um complexo enzimático em dietas para tilápias-do-nilo (Oreochromis niloticus) sobre o desempenho, a composição química da carcaça e a qualidade da água. Foram utilizados 200 alevinos revertidos (4,57 ± 1,24 g), distribuídos em delineamento inteiramente casualizado em 20 tanques de 500 litros, com quatro tratamentos e cinco repetições, considerando a unidade experimental uma caixa com dez peixes. Os peixes foram alimentados com dietas contendo 0; 0,033; 0,066 ou 0,099% de complexo enzimático. As dietas foram processadas na forma peletizada e fornecidas quatro vezes ao dia, às 8, 11, 14 e 17 h. Os valores médios de pH, condutividade elétrica, oxigênio dissolvido, temperatura, fósforo total, amônia e nitrato da água de cultivo não foram influenciados pela dieta. A inclusão do complexo enzimático na dieta não afetou o ganho de peso, as taxas de sobrevivência e de crescimento específico, mas influenciou o consumo de ração e a conversão alimentar, cujos valores foram maiores nos peixes alimentados com a dieta com 0,066% de complexo enzimático. Não foram observadas diferenças nos teores de matéria seca, umidade, proteína bruta, matéria mineral, cálcio e fósforo na carcaça dos peixes, no entanto, o teor de extrato etéreo reduziu de forma linear com o aumento do nível de complexo enzimático. A utilização de complexo enzimático (amilase, protease, celulase, lipase, pectinase, xilanase, β-glucanase e fitase) no nível de 0,066% em dietas para juvenis de tilápia-do-nilo piora a conversão alimentar, mas não influencia o desempenho e a composição corporal dos peixes.

An investigation of the possible health-promoting modes of action of regular- and super- doses of phytase in the broiler chicken

The overall objective of this thesis was to study the effects of regular and high (super-) doses of phytase in the gut of broilers, with the aim of documenting the mechanism of their action leading to improvements in animal health. Phytase is often supplemented to commercial broiler diets to facilitate the hydrolysis of plant phytate and release of phosphorus for utilisation. Although not the original intention of its addition, phytase supplementation leads to improvements in growth performance parameters and enhanced nutrient utilisation. Further benefits have also been observed following the addition of super-doses of phytase which are not explained by an increase in phosphorus release, and thus have been termed ‘extra-phosphoric effects’. Using diets formulated to be adequate or marginally deficient in available phosphorus (aP; forming the negative control, NC), phytase was supplemented at 1,500 and 3,000 FTU/kg phytase in the first study (both super-doses) and the partitioning of nutrients within the body was investigated. It appeared that there were some metabolic changes between 1,500 and 3,000 FTU/kg, switching between protein and fat accretion, potentially as a consequence of nutrient availability, although these changes were not reflected by changes in growth performance parameters. However, the loss of the NC treatment without phytase on day 12 limits the comparison of the phytase within the NC treatment, but does allow for comparison of each dose at adequate or low dietary aP levels. As expected, a greater degree of phytate hydrolysis was achieved with 3,000 than with 1,500 FTU/kg phytase, but changes in carcass accretion characteristics were greater with 1,500 than 3,000 FTU/kg. Using these findings and the observation that there were no further changes in the parameters measured by increasing phytase from 1,500 to 3,000 FTU/kg (aside from phytate hydrolysis), 1,500 FTU/kg phytase was selected as the super-dose to be used in subsequent studies. The next study considered the influence of regular (500 FTU/kg) and super doses (1,500 FTU/kg) of phytase from within the gut. Overall, it was observed that changes were occurring to the gut environment, which ultimately would influence the absorptive capacity and conditions for further phytate hydrolysis. Dietary treatment influenced gut conditions such as pH, intestinal morphology and bacterial populations which can subsequently influence nutrient utilisation and potential for growth. The subsequent study was designed to investigate the effects within the gut in more detail. The release of nutrients from phytate hydrolysis and their bioavailability within the digesta can influence conditions within intestine, facilitating enhanced absorption. One of the parameters investigated was the expression of genes involved in the transport of nutrients in the intestine. Overall, there were few significant dietary treatment influences on gene expression in the intestine, however there was a dose-dependent response of phytase on the expression of the jejunual divalent mineral transporter. This indicates a change in divalent mineral bioavailability in the intestine, with correlations with inositol phosphate esters (IPs) being identified. This is likely explained by the IPs produced by phytase hydrolysis and accumulating in the digesta, differing between regular and high doses of phytase. It became apparent that interactions between the products of phytate hydrolysis (IP3, IP4) and minerals in the digesta had the potential to influence the gut environment and subsequent nutrient bioavailability and overall phytase action. The final study was designed to increase the content of the IPs, and investigate the influence of phytase under these conditions. As the complete hydrolysis of phytate to myo-inositol has been reported to be beneficial due to its proposed insulin mimetic effects, myo-inositol was also supplemented to one of the diets to see if any further benefits would be observed when supplemented alongside super-doses of phytase. Neither increased concentrations of the higher IP esters (IP6, IP5 and IP4) nor myo-inositol (myo-) had any effect on broiler growth performance, however there were still apparent beneficial influences of phytase supplementation. The results suggest considerable and important interactions between minerals and IP esters within the digesta, which ultimately have the potential to influence gut conditions and thus nutrient utilisation and growth performance. Reduced concentrations of blood glucose in the high IP ester diet with additional phytase supplementation suggest some insulin-like effects of myo- production. Additionally, the lack of effect of myo- supplementation on blood glucose and insulin concentrations suggests a difference between the structure of phytase-produced myo- and supplemented myo-. Although there were no improvements in growth performance by increasing phytase from 500 to 1,500 FTU/kg, there were changes occurring at the level of the gut and expression of genes in the intestine, influencing nutrient utilisation and the partitioning of nutrients within the body. There are many factors to be considered when supplementing phytase, with dietary nutrient content and nutrient release and IP production during phytate hydrolysis having an influence on phytase action, nutrient absorption and conditions within the gut. Super-doses of phytase may be beneficial for maintaining optimal gut conditions, clearing IP esters from the digesta, reducing their potential to form complexes with minerals and other nutrients, ultimately influencing the efficiency of production.

Calcium phosphate flocs and the clarification of sugar cane juice from whole of crop harvesting

Sugar cane biomass is one of the most viable feedstocks for the production of renewable fuels and chemicals. Therefore, processing the whole of crop (WC) (i.e., stalk and trash, instead of stalk only) will increase the amount of available biomass for this purpose. However, effective clarification of juice expressed from WC for raw sugar manufacture is a major challenge because of the amounts and types of non-sucrose impurities (e.g., polysaccharides, inorganics, proteins, etc.) present. Calcium phosphate flocs are important during sugar cane juice clarification because they are responsible for the removal of impurities. Therefore, to gain a better understanding of the role of calcium phosphate flocs during the juice clarification process,the effects of impurities on the physicochemical properties of calcium phosphate flocs were examined using small-angle laser light scattering technique, attenuated total reflectance Fourier transformed infrared spectroscopy, and X-ray powder diffraction. Results on synthetic sugar juice solutions showed that the presence of SiO2 and Na+ ions affected floc size and floc structure. Starch and phosphate ions did not affect the floc structure; however, the former reduced the floc size, whereas the latter increased the floc size. The study revealed that high levels of Na+ ions would negatively affect the clarification process the most, as they would reduce the amount of suspended particles trapped by the flocs. A complementary study on prepared WC juice using cold and cold/intermediate liming techniques was conducted. The study demonstrated that, in comparison to the one-stage (i.e., conventional) clarification process, a two-stage clarification process using cold liming removed more polysaccharides (≤19%),proteins (≤82%), phosphorus (≤53%), and SiO2 (≤23%) in WC juice but increased Ca2+ (≤136%) and sulfur (≤200%)

Phosphorus nutrition and tolerance of cotton to water stress I. Seed cotton yield and leaf morphology

Seed cotton yield and morphological changes in leaf growth were examined under drying soil with different phosphorus (P) concentrations in a tropical climate. Frequent soil drying is likely to induce a decrease in nutrients particularly P due to reduced diffusion and poor uptake, in addition to restrictions in available water, with strong interactive effects on plant growth and functioning. Increased soil P in field and in-ground soil core studies increased the seed cotton yield and related morphological growth parameters in a drying soil, with hot (daily maximum temperature >33°C) and dry conditions (relative humidity, 25% to 35%), particularly during peak boll formation and filling stage. The soil water content in the effective rooting zone (top 0.4 m) decreased to -1.5 MPa by day 5 of the soil drying cycle. However, the increased seed cotton yield for the high-P plants was closely related to increasing leaf area with increased P supply. Plant height, leaf fresh mass and leaf area per plant were positively related to the leaf P%, which increased with increasing P supply. Low P plants were lower in plant height, leaf area, and leaf tissue water in the drying soil. Individual leaf area and the water content of the fresh leaf (ratio of dry mass to fresh mass) were significantly dependent on leaf P%.

Potential Application of Adsorptive Media to Enhance Phosphorus Uptake in Stormwater Basins and Wetlands at Lake Tahoe : literature review. Report to the University of California Davis Tahoe Research Group

Phosphorus removal by wetlands and basins in Lake Tahoe may be improved through designing these systems to filter storm water through media having higher phosphorus removal capabilities than local parent material. Substrates rich in iron, aluminum and calcium oftentimes have enhanced phosphorus removal. These substrates can be naturally occurring, byproducts of industrial or water treatment processes, or engineered. Phosphorus removal fundamentally occurs through chemical adsorption and/or precipitation and much of the phosphorus can be irreversibly bound. In addition to these standard media, other engineered substrates are available to enhance P removal. One such substrate is locally available in Reno and uses lanthanum coated diatomaceous earth for arsenate removal. This material, which has a high positive surface charge, can also irreversibly remove phosphorus. Physical factors also affect P removal. Specifically, specific surface area and particle shape affect filtration capacity, contact area between water and the surface area, and likelihood of clogging and blinding. A number of substrates have been shown to effectively remove P in case studies. Based upon these studies, promising substrates include WTRs, blast furnace slag, steel furnace slag, OPC, calcite, marble Utelite and other LWAs, zeolite and shale. However, other nonperformance factors such as environmental considerations, application logistics, costs, and potential for cementification narrow the list of possible media for application at Tahoe. Industrial byproducts such as slags risk possible leaching of heavy metals and this potential cannot be easily predicted. Fly ash and other fine particle substrates would be more difficult to apply because they would need to be blended, making them less desirable and more costly to apply than larger diameter media. High transportation costs rule out non-local products. Finally, amorphous calcium products will eventually cementify reducing their effectiveness in filtration systems. Based upon these considerations, bauxite, LWAs and expanded shales/clays, iron-rich sands, activated alumina, marble and dolomite, and natural and lanthanum activated diatomaceous earth are the products most likely to be tested for application at Tahoe. These materials are typically iron, calcium or aluminum based; many have a high specific surface area; and all have low transportation costs. (PDF contains 21 pages)

Suitability of commercially available Bacillus probiotics on growth, survival and production of black tiger shrimp (Penaeus monodon Fab.)

Different forms of Bacillus probiotics was assessed in the earthen ponds on tiger shrimp (Penaeus monodon) culture. The experiment was designed with three different treatments depending on the mode of application (T1=oral probiotics; T2=spreading probiotics and T3=oral+ spreading probiotics). The shrimp was cultured for 120 days with the stocking density of 6-PL/m².Oral probiotics in the respective ponds were supplied with feeds. Whereas, spreading probiotics was applied to the pond water during pond preparation at 30, 60 and 90 days of culture period. Results of the experiment revealed that, all forms of Bacillus probiotic had effective role to keep the culture environment friendly in terms of mineralization of organic matter, nitrogen and phosphorus content in bottom sediment; holding of water transparency in a congenial state, increasing the density of planktonic biomass and boosting the THB-Vibrio ratio in water and sediment with insignificance (p>0.05) difference between different treatments. Whilst, spreading form of Bacillus pro biotic showed higher weight gain (27.58±1.18g), survival rate (70.75±8.54%) and production (1167.66±109.62 kg/ha) and expected lower FCR (1.81 ±0.06) values with significant difference (p<0.01) with others methods of application, indicated its superiority in tiger shrimp culture.

ROLE OF PHOSPHORUS CYCLING IN ALGAL METABOLISM AND ALGAL SUCCESSION IN LAKE DONGHU, CHINA

The role of phosphorus cycling in algal metabolism was studied in a shallow lake, Donghu, in Wuhan using the methods of measuring cell quota C, N and P, and calculating nutrients uptake rate by algal photosynthesis. The mean daily phosphorus uptake rate of phytoplankton varied between 0.04-0.11 and 0.027-0.053 g/m2/d in station I and station II respectively. The turnover time of phosphorus in phytoplankton metabolism ranged from 0.75-5.0 days during 1979-1986. The available P was 0.176 (+/- 0.156) g/m3 (mean +/- SD) in 1982 and 0.591 (+/- 0.24) g/m3 in 1986. The relationship between P/B ratio (Y) and TP (X: mg/l) was described by the following regression equation Y = 1.163 + 0.512logX (r = 0.731, P < 0.001). The dynamics of algal biomass and algal species succession were monitored as the indicators of environmental enrichment. The small-sized algae have replaced the blue-green algae as the dominant species during 1979-1986. The small-sized algae include Merismopedia glauca, Cryptomonas ovata, Cryptomonas erosa, several species Cyclotella. There has been drastic decrease in algal biomass and an obvious increase in P/B ratio. A nutrient competition hypothesis is proposed to explain the reason of the disappearance of blue-green algae bloom. The drastic change in algal size and the results in high P/B ratio (reaching a maximum mean daily ratio of 1.09 in 1986) may suggest a transition of algal species from K-selection to r-selection in Lake Donghu.