Search

The effects of different levels of nutrient input on the plankton community was investigated in a two-year controlled fertilization study of eight experimental ponds. There were four treatments, each replicated: a control, to which no fertilizer was added, and three levels of nutrient addition. Limnological parameters including phytoplankton and zooplankton densities were measured frequently during both summers and less frequently during the rest of the year. Inorganic nitrogen and phosphorus concentrations in the treated ponds increased. Phytoplankton and zooplankton density increased with treatment level but was variable. There was a limited relationship between the average chlorophyll a concentration per summer and the average cladoceran dry weight per summer. Above chlorophyll a concentrations greater than 60–70 mg/m3 other factors such as a pH zooplankton mortality effect, prevailed.

Seasonal variations in concentrations and ranges of nitrate and total phosphorus were measured in six lakes (Conesus, Canadice, Honeoye, Devil's Bathtub, Java, and Lime) of western New York. The variations may reflect the geochemistry of the area, local differences in lake hydrology and mixing characteristics, and the supply of nutrients from soil, man, and precipitation. Calculations of nutrient (P) loading were made for the six lakes in New York and compared to loading values for nine English lakes. The specific values derived from these calculations can not be considered absolute but they do indicate the relative importance of human versus edaphic contributions and provide an aid in management considerations.

Analyses of nine ionic constituents in Rostherne Mere water were made at regular intervals and five depths over a two year period. Only nitrate-nitrogen showed a regular seasonal pattern. Phosphate-phosphorus and ammonium-nitrogen increased with depth in summer. The results are discussed in relation to the origin of the nutrients, stratification and the phytoplankton of the mere. The levels of nutrients present did not appear to limit algal growth with the possible exception of nitrogen.

Water samples were collected during inundation by the tides of the littoral Spartina patens vegetation. This grass is characterized by a more or less permanent inferior layer of dead grass which is thick and uniform enough to suggest a filtering system. Water analyses demonstrated clear variation with time in P, PO4, and Mn; this variation corresponds with changes in the level of the water during high tide, as well as with the progressive inundation of the Spartina patens vegetation.

Two experiments were carried out to determine the rate of release of ions to lake water from dry grass (largely Eragrostis species) and dung from elephant, impala and buffalo. The ions released most rapidly were PO33- and K+, followed by NO3- and Ca2+ + Mg2+; the smallest increase was shown by Na+. In general, dung derived from grass released ions more rapidly than grass itself; the results are discussed in relation to ash analyses of grass and dung. The possible importance to Lake Kariba of the nutrients released by grass and dung following immersion under natural conditions is considered.

Samples of Eichornia crassipes (MART.) SOLMS were collected from the New Braunfels to Gonzales reach of the Guadalupe River, Texas. Plants were also cultured in the laboratory in media containing varying amounts of nitrate and phosphate.

The production of organic matter by phytoplankton in Sollerod So, which receives large amounts of purified sewage, has been determined at 1300 g glucose per sq. m and year. A maximum of 9.5 g per sq. m is reached per day. It is shown that the yearly production in a lake of this type presumably cannot be considerably greater as through the consumption of carbon dioxide pH will increase to such a degree that this factor becomes injurious to the plankton algae. The uptake of CO2 from the atmosphere whereby pH is lowered thus is the real limiting factor for the production of organic matter in the lake. During the height of summer between 60 and 100 g CO2 is absorbed from the atmosphere per sq. m surface per month.

Changes in the flora and fauna at Loch Leven are described. Species associated with oligotrophic conditions such as charr and desmids have declined or disappeared, and prolonged, dense algal blooms, particularly Cyanophyceae, have been a feature of recent years. Much of the macrophytic vegetation has disappeared and there have been changes in the composition of the zooplankton and benthos, several abundant species disappearing (Table II). Possible reasons for these changes are given. Die Veranderungen in der Pflanzen-und Tierwelt von Loch Leven werden beschrieben. Gattungen welche gewohnlich in oligotrophen Gewassern gefunden werden, wie Salvelinus und Desmidiaceae, sind verringert oder ganz verschwunden. In den letzten Jahren sind Cyanophyceae immer haufiger hervorgetreten. Viele hohere Pflanzen sind verschwunden und es hat sich vieles geandert in der Komposition des Zooplanktons und Benthos. Mehrere wichtige Gattungen dieser Gruppen verschwinden allmahlich. Mogliche Grunde fur diese Veranderungen werden gegeben.

During the summer of 1969, fourteen Guatemalan lakes were sampled, including eight in the lowland northern province of Peten and six in southern Guatemala. The majority of the Peten lakes exhibited thermal stratification and hypolimnetic oxygen depletion. In most cases, pollution tolerant bottom forms were found. Algal species and numbers in general corresponded to a subjective estimate of the degree of nutrient input to the lakes. Lyngbya was usually the organism found when blooms were noted. The lakes in the Peten are predominately calcium bicarbonate and calcium sulfate lakes, but magnesium is also high in several of them. The southern lakes were chemically more variable, with sodium being more important than in the northern lakes. Most of the southern lakes also exhibited thermal stratification and hypolimnetic oxygen depletion, with the flora and fauna dependent upon oxygen and nutrient conditions. The authors conclude that different criteria than those used to assess the trophic status of temperate lakes are needed to classify tropical lakes.

Abbot's Pond provided constrasting environments through the year which supported differing algal populations. Permanent thermal stratification and the depletion of oxygen in the hypolimnion together with accumulation of nutrients within the latter provided two distinct regions that supported different algal populations. In the photic epilimnion, Chlamydomonas, Pandorina, Scenedesmus and Stephanodiscus formed dominant populations whereas in the lower regions, to where very little light penetrated, Cryptomonas rufescens and Trachelomonas volvocina formed dominant populations. The irregular occurrence of the “other main phytoplankters” indicated that their ecological niches were smaller than those of the Diatoms and Chlorophyceae which occur each year. Chrysococcus was able to develop large populations in conditions of low turbulence and to maintain itself again in low turbulent conditions at the limit of light penetration when turbulence did increase in the upper regions of the water column. The occurrence of the small Rhodomonas appeared to be associated with high nutrient levels in the water and not with temperature of water. Similarly Trachelomonas volvocina populations were associated with high nutrient levels but in conditions of very low oxygen levels, as were C. rufescens populations. Trachelomonas volvocina var. minuta occurred for the first time in 1969 and appeared to die as the water column became more stable and nutrient levels in the epilimnion fell. Therefore, growth of algal populations of Abbot's Pond was dependent upon the physical, chemical and biological factors found within the water column.

A study was conducted to determine a physicochemical profile of a new deep-storage reservoir and to determine the influence of impoundment and thermal stratification in the reservoir on the physicochemical limnology of the parent river. The presence of thermal stratification from May through November caused the most significant change in water conditions. Of 23 parameters studied, 12 remained unchanged, 10 improved, and 2 deteriorated (Table VI). The greatest downstream changes in water conditions from those upstream from the reservoir were a decrease in temperature, an increase of ammonia, and the presence of hydrogen sulfide during the period of thermal stratification. Ammonia did not increase to a level considered to be toxic to aquatic species. It could, however, serve as a nutrient for certain species of plants and result in a change in community structure. Water tempeature downstream from the reservoir was always within the annual temperature range of the river upstream from the reservoir; however, the summer maximum in the tailrace was decreased to a temperature that could interfere wih the normal life cycle of many species.

Findley Lake is a dimictic, oligotrophic, subalpine lake located in the western Cascade Mountains, Washington. The lake is snow covered for most of the year so that the growing season was 3.5 months in 1971 and 4.5 months in 1972. Rapid melt of the lake's snow cover in summer allowed the sudden development of a phytoplankton productivity maximum (as measured by the 14C tracer method) of 86 mg m−2 hr−1 and a peak of 48 mg chlorophyll a per m1 within two weeks of surface clearing in 1972, followed by a rapid decline of productivity and biomass. Annual production (between 10 October, 1971 and 21 October, 1972) was 36 g/m2 in the 27.5 m water column. Autotrophic carbon assimilation during the snow-covered period was insignificant. The total production for the lake in 1972 was 530 kg carbon. The concentration of available nitrogen (NO2 + NO3 + NH3 as N) at 15 m ranged from 12 to 76 mg/m3 while PO4-P ranged from 0.5 to 8.3 mg/m3. In vitro nutrient enrichment experiments with natural phytoplankton communities from the lake indicated that while N and P together were growth limiting, P alone produced a growth response while N alone did not. Contributions to production from net-, nanno-, and ultraplankton were determined by fractional filtration of 14C-labeled phytoplankton samples. The nannoplankton, dominated by diatoms, accounted for 58% to 94% of productivity.

Nitella hookeri A. BR., a native charophyte of the Rotorua lakes in the North Island of New Zealand, was investigated in terms of its nutrient requirements under laboratory culture in non-arenic conditions. Optimum growth in phosphate, nitrate, ammonia, iron and magnesium occurred at 20 mg l−1 or lower. Higher concentrations of these ions were markedly inhibitory to growth when compared with the optimum. Calcium and potassium gave growth at higher levels and over a wider range of concentrations. Sulphate and sulphur-amino acids do not promote growth above the levels of the basal medium (1.2 mg l−1 sulphur as SO2−4). Amino acids did not appear to provide a nitrogen source for the plant. The optimum phosphate concentration was one thousand times higher than previously reported values. This may be due to the presence of arsenic in the vegetative propagules used from Lake Rotoiti. Iron toxicity effects may have resulted from the presence of EDTA. The results are considered in relation to the known levels of nutrients present in lake waters. Only phosphorus appears directly correlated with the natural distribution of the plant but it is suggested that anaerobic lake substrates may contribute iron and ammonia to the plants and further explain their distribution.

Muds from 12 types of soils were used as the only source of phosphorus in cultures of Scenedesmus dimorphus. Some muds supported as much algal growth as was obtained with 0.075 to 0.5 mg/1 of phosphorus, while little or no growth occurred in cultures which contained other muds as a source of phosphorus. Algal growth was correlated with the fractions of soil phosphorus which were extracted with the following solutions; I — the phosphorus — free nutrient solution, II — 0.05N HCl plus 0.025N H2SO4, III — 0.002N H2SO4 plus 3 g/l of K2SO4, and IV — 0.1N HCl plus 0.03N/NH4F. Additions of phosphorus to the soils prior to their use as muds increased the suitability of some as sources of phosphorus, but for others the added phosphorus was so tightly bound to the soil that little or none was available to S. dimorphus. The findings indicate that the type of soil in a pond will likely have a large influence on the efficiency of fertilization with phosphate fertilizers.

Lake McIlwaine is a tropical eutrophic impoundment in Rhodesia. The normal oxygen and temperature patterns are described, and the effect of flood water on these patterns is discussed. Several important chemical parameters are described, and the effects of lake-level fluctuations and stratification are outlined. There is a brief discussion on the effects of eutrophication in tropical lakes, and some indication is given of measures being taken to reduce nutrient input to Lake McIlwaine.

1. The conditions of existence of an astatic type of water in Madras was investigated for 28 months. 2. The reservoir gets its water from a catchment area containing a very low or ‘nil’ percetage of cultivable land; and the water is most turbid and reddish coloured. About 60 % of the phytoplankton consists of Desmids. 3. Pearsall's conclusion that the stage of evolution of the lake basin must be regarded as being the fundamental factor affecting the distribution of phytoplankton for lakes of the temperate region appears to be true in the case of this reservoir in Madras. 4. Blue-green algae also occur at a later stage when the organic content is higher and nutrient substances of biological significance are lower in the reservoir.

1. Growth of the floating aquatic weed, Salvinia, in sterile culture was exponential for at least 2 weeks under standardized conditions. 2. Increase in light intensity or in CO2 resulted in increases in growth rate, but did not extend the exponential period of growth. 3. This aquatic plant, like many others, discriminates against calcium relative to strontium. 4. In culture Salvinia exhibited luxury consumption of N and P. 5. Because of high C/N ratios, Salvinia may not be a favorable source of animal food, but might be useful in nutrient removal schemes. 6. In sterile culture, S. molesta produced fewer leaves than S. minima, but maintained a significant increase in leaf area and dry weight. This may be correlated with the ability of the first species to rapidly spread over tropical waterways.

1. Hartbeespoort Dam is eutrophic with a low transparency — a condition which has developed during the past 25 years. 2. Is is monomictic with complete circulation during the winter months, often resulting in low dissolved oxygen concentrations throughout the dam. 3. The nutrient component of the water is obtained directly from the Jukskei-Crocodiel River and to a lesser degree from the Magalies River. 4. Rises in pH in the epilimnion were mainly caused by the photosynthetic activity of the algae in the presence of moderately basic water. 5. The bottom sediments in the deeper portion of the dam underwent rapid anaerobiasis after the establishment of a thermocline and oxyclinic in summer. 6. The density of the fauna in the bottom sediments decreases rapidly with the establishment of the hypolimnion. 7. The sediments are rich in iron and during summer there was an increase in the ferrous component. The soluble and acid soluble phosphorous increases in the hypolimnion after a winter minimum. 8. Silica content is comparable with productive water masses in other parts of the world. 9. The faunal associations are typical of other moderately basic and highly productive waters in the same geographical region of South Africa.

A total of 88 taxa were noted in these samples, of which there were 44 diatoms, 41 pyrrhophyceans, 2 cyanophyceans and 1 silicoflagellate. Totals of 37 and 38 different phytoplankters were observed during cruises E46K-67-68 and E1-C-70, respectively, with 58 species noted in the extensive samplings of E 5013-68-69. A diatomaceaous flora predominated in each series of collections. The phytoflagellates were well represented, but in low numbers. The overall phytoplankton concentrations were low for each of the areas studied during these three January cruises. Even the preliminary data on the coccolithophore concentration does not indicate a major development at this time of the year. Generally, phytoplankton counts were lowest at stations most distant from the island complex and especially in the shallow waters that passed between the islands, directly from the north Atlantic into the Caribbean Sea. Results from the 1969 and 1970 collections west of the Lesser Antilles correspond closely to the findings reported by Hargraves et al. (1970). There was considerable diversity of phytoplankton species, but they were present in low numbers. They have related this condition to the low nutrient concentrations in the oceanic waters of the Lesser Antilles region.

The relationship between growth of aquatic plants and their nutrient supply is poorly understood, because of the lack of suitable models which could be tested in the field. The purpose of this research was to learn if the Michaelis-Menten expression describes the relationship between the uptake of NH4 by Ceratophyllum and the concentration of NH4 in solution.

The study of both the physical and chemical water characteristics of the Nile and its tributaries in the Sudan (south of Khartoum) was carried out. The main changes along the White Nile are due to tributary contribution especially that of the riverain swamps and River Sobat. The Gazal has no effect due to its negligible contribution to the White Nile. The influence of the Zeraf, although showing marked characteristics, is restricted to 50–80 km north its mouth. This is due to its low discharge and it is being diluted with the Sobat water. The study of Bahr el Gazal showed a significant longitudinal succession of this tributary where the water characteristics of its upper reaches differ considerably from those at Lake No. At the Gazal mouth a decrease in the dissolved phosphates, silicon, iron and chlorides takes place. The water of Bahr el Jebel, as it passes through the Zeraf, becomes enriched with nutrient salts which account for the dense plankton population of this tributary. As the water passes through the swamps at the ‘sudd’ region depletion of its oxygen and sulphate content takes place. The characteristics of the water at the swamps affect the animal life and may be important factors in the distribution of animals living in these waters. The influence of Jebel Aulia dam on the water characteristics was studied and results show that significant modifications take place during the seasonal storage of water. The effect of the water hyacinth (Eichhornia crassipes Sol ms.) on the hydrobiology of the Nile was pointed out. The marked decrease of the nitrate nitrogen at Jebel Aulia basin may be partly attributed to its uptake by this plant; especially the reservoir provides ideal conditions for the spread of Eichhornia. The stunted growth of the water hyacinth was recorded at the upper reaches of Bahr el Gazal. This could not be explained due to the low salt content or low pH of the Gazal as Eichhornia is widely spread and shows maximum growth at the Sobat which has more or less the same salt content, pH, oxygen content and alkalinity.

A limnological study of seventeen man-made lakes has been made. Thermal features showed absence of stable thermal stratification. Cognisable thermocline did not exist. The South-Western reservoirs with low nutrient and salt content were very poor in productivity, but the high alkaline reservoirs were also not very productive. Some reservoirs with lower alkalinity, hardness and total solids developed algal blooms and were highly productive. Bhavanisagar and Stanley reservoirs with optimal levels of dissolved salts and alkalinity-hardness were fairly productive. Reservoirs with organic soils were better in productivity than those with higher silica content (Hope Lake, Poondi Reservoir, Vaigai etc.) Dissolved oxygen depletion in the bottom was characteristic of productive waters. Total oxygen depletion occurred in some of them but in a few depletion was rare and not of great severity. Klinograde curves were characteristic of productive reservoirs. Even when the bottom waters were low in or were devoid of dissolved oxygen the outflow from this level picked up oxygen within a short distance of 100 m. Effect of water replacement on plankton production is discussed. Primary production in the reservoirs has been compared and discussed. It is the silt-laden turbid waters that are poor in production. Water releases could be manipulated to assist spawning of fishes and for amelioration of pollution downstream.

The introduction of excess nutrients along with other pollutants into natural waters is causing significant changes in these aquatic environments. One of the common changes resulting from nutrient additions is an excessive growth of algae and aquatic weeds . In the past, various bioassay systems have been suggested for monitoring aquatic environments for potential algal productivity . (FITZGERALD, 1968, 1969 ; OSWALD & GAONKAR, 1969 ; POTASH, 1956 ; SKULBERG, 1964 ; STROM, 1933) . Recently there has been an attempt to standardize assay procedures so that results from different laboratories may be readily compared . The Provisional Algal Assay Procedures (PAAP), BUELTMAN et al., (1969) were developed by a joint industry/government task force as a first step in this standardization. Three tests are listed in these procedures

Water samples were collected from Lake Jackson, near Tallahassee, Florida, and enriched with N, P, N + P, and Si in the laboratory in April, 1969 and January, 1970. After time intervals of 3 and 6 days in April, and 13 days additionally in January, phytoplanktonic algae in the cultures were enumerated as to species composition and cell numbers with an inverted plankton microscope. Controls, to which no nutrients were added, were also maintained to determine changes arising from culture-room conditions.

This study describes seasonal variation in the numbers of planktonic organisms in relation to hydrological changes in a flood-controlled reservoir at Ibadan, Nigeria. Results of fortnightly estimations of water-level, temperature, transparency, and oxygen content have been presented. The reservoir is thermally stratified for most of the year but the periodic flooding following heavy rainfall and the occasional breakdown of the periodic flooding following heavy rainfall and the occasional breakdown of the thermal stratification by winds during the dry season dominate the habitat, causing regular seasonal fluctuation in plant nutrients and the transparency of the water.

1. The presence of two yearly plankton growth peaks is confirmed. Development of the plankton is correlated with environmental conditions such as transparency, temperature, dissolved gases, nutrients, pH, alkalinity, conductivity etc. 2. At the Mogran, rotifers outnumber crustaceans; both are at equilibrium at Shagara and the reverse occurs at Jebel Aulia. This may result from mixing of Blue and White Nile waters. 3. The presence of Tropodiaptomus processifer, T. kraepelini, T. orientalis, Brachionus caudatus, Anabaenopsis circularis and Closterium leibleinii at the Mogran and a little distance further south also indicates the influence of the Blue Nile waters on the White Nile.

Ecological problems arising as a result of rapid growth of S. natans Hoffim in some lakes of Kashmir have been studied. High viability of spores coupled with rapid vegetative propagation seem to be responsible for the spread of the weed. Lake channels protected from wind by a canopy of trees are the most favourable situations in which Salvinia produces a thick mat. Water in these channels is rich in nutrients. Oxygen poor layers of water beneath the mat are detrimental for insect and fish life. Besides, the changing light conditions have profound influence on the submerged vegetation. The most common associates of Salvinia are Hydrocharis dubia and Ceratophyllum demersum.

Polluted water flowing over stabilized and active deposits is purified in 3 ways. 1. Physical adsorption and biochemical degradation. 2. Biochemical processes in deposits over which water flows can be quantitatively complete since, unlike conventional systems, they do not depend on the nutrients contained in the pollution load itself, but take place in the sediment where supply of available food can become less easily unbalanced or exhausted than the food contained in the pollution. Thus, if a polluted water is allowed to flow through and over an active stabilized sediment, degradation may become one hundred percent. 3. In contrast to existing opinions, bottom deposits of maturation ponds and natural waters are anaerobic or semi-aerobic systems which supplement the aerobic processes regarding the removal of carbon by gassification as CH4, nitrogen as N2 and possibly sulphur as H2S. Our conventional concept of pond systems being purely aerobic has to be revised since even in aerobic systems, processes taking place in the bottom deposits, are anaerobic.

The longitudinal succession of physical and chemical water characteristics in the White Nile is described, and some seasonal differences are outlined. Most successional changes are due to tributary contributions, of which the discharge from Lake Albert is particularly important, and to riverain swamps, especially in the south Sudan. Swamp effects include a partial deoxygenation and depletion of phosphate and sulphate, of which the first two vary considerably with season. The origin and extent of changes in plant nutrients, and in physical factors affecting plant growth, are discussed with reference to the growth of planktonic algae in the lower river region.

The elemental composition of E. crassipes falls within the range of elemental values reported for other aquatic and terrestrial plants. Concentrations of macronutrients in water hyacinth biomass were not correlated with environmental levels of these nutrients. E. crassipes produces large, dense stands and dominates biogeochemical cycles in many aquatic ecosystems.

An attempt has been made to find out the productivity and periodicity of the phytoplankton in relation to the physical and chemical characteristics of the river Ganges, between ‘University Ghat’ and ‘Raj Ghat’ at Varanasi. The observations were taken during a single year (i.e., March 1957 to March 1958). The chemical analyses of the water and estimates of the number of phytoplankton were made on samples collected fortnightly. The phytoplankton has proved to be eutrophic and polymixic in nature. Diatoms formed the largest bulk, blue-greens being the second major constituent while the green algae formed the third in order of abundance with, however, large number of species. A definite phytoplankton periodicity has been noticed and found to be seasonal in character. Correlations between the phytoplankton periodicity and population maxima, with the habitat factors revealed depletion of nutrients like, nitrogen, phosphate, silica, carbon, magnesium and sulphates. Changes in the phytoplankton populations were clearly evident more in relation to physical than to chemical conditions of the water. Changes in water-level, transparency and temperature affected the growth of the phytoplankton. High alkalinity and buffering capacity resulted in preferential growth of diatoms and blue-green algae. Rich phosphates and silicates coupled with moderate nitrogen contents were responsible for high phytoplankton yields in summer and winter seasons. The abundance of blue-greens may be due to the higher values of pH, temperature, dissolved organic matter, phosphate, nitrogen, and relatively high values of dissolved oxygen. Green algae showed a wide range of adaptability but could not develop in any abundance.