Seasonality in Nutrients and Phytoplankton Production in Two Shallow Lakes: Waigani Lake,Papua New Guinea,and Barton Broad,Norfolk, England

Waigani Lake, near Port Moresby, Papua New Guinea and Barton Broad, Norfolk, England are both shallow lakes nutrient-enriched from sewage effluent disposal. In Waigani Lake phytoplankton biomass varied seasonally with lower levels (100-200 mg chlorophyll α m⁻³) during the wet season increasing to over 400 mg chlorophyll α m⁻³ at the end of the dry season. Secchi disc depths varied between 0. 11 and 0. 34 m. Phytoplankton productivity in Waigani Lake was very high throughout the year (range: A_max 4,370-21,000 mg O₂ m⁻³ h⁻¹) but production was lower during the wet season (range: A_max 4,370-12,700 mg O₂ m⁻³ h⁻¹). High surface productivity was recorded from August to December except on sampling days when the weather was overcast. Productivity throughout the year declined rapidly with depth. Algal biomass in Barton Broad varied from 3-10 mg chlorophyll α m⁻³ in winter but increased in spring and was very high in summer (200-500 mg chlorophyll α m⁻³). Secchi disc depth varied from 0.21 m in August 1976 to 1.76 m in December. Phytoplankton production in Barton Broad was low in winter (range: A_max 247-1,250 mg O₂ m⁻³ h⁻¹) but increased markedly in spring and summer with the highest rate (A_max 6,850 mg O₂ m⁻³ h⁻¹) being recorded in August. Surface inhibition was observed during summer except when the weather was overcast. Seasonality in nutrients and phytoplankton in Waigani Lake appear to be related to rainfall. Nutrient concentrations in Barton Broad are more closely related to phytoplankton activity which, in turn, correlates with seasonality in solar radiation.     

Limnological Studies in a Tropical Man-Made Lake (Lagartijo Reservoir) Venezuela

The purpose of this study was to evaluate the present limnological conditions of Lagartijo reservoir (North central Venezuela) and to compare them with conditions reported in early studies. Lagartijo reservoir supplies an important part of the water demand for Caracas city and wide fluctuations on water volume occur annually. Relevant physical, chemical and biological data were obtained from three sampling stations between July 1990 and April 1992. The reservoir was permanently stratified with a well defined thermocline. The main tributary (Lagartijo river), with a temperature about 6° C colder than the surface temperature of the reservoir, flows through the hypolimnion producing distinct chemical and biological properties. The average of the daily integral phytoplankton photosynthesis was 1550 mg C m⁻² d⁻¹. The present annual average of the net photosynthetic activity is about 40% lower than the reported for 1970 and corresponds to an apparent decrease in phytoplankton biomass and to the reduction of the euphotic zone. Photosynthetic activity was higher for the wet season than for the dry season. Actual chlorophyll a concentration in the euphotic zone averages 4.9 μg l⁻¹. Abundance of zooplankton was significantly decreased in comparison to 1976. Mean zooplankton biomass (dry weight) for the upper 10 m layer was 596 μg l⁻¹. Copepods accounted for most of this biomass, followed by cladocerans and rotifers. For the first time, a freshwater medusa (probably Craspedacusta sowerbyi) was collected from Venezuelan waters.     

A Compositional and Structural Analysis of Phytoplankton in Lake Khurpatal, (U.P.), India

The phytoplankton community in Lake Khurpatal (Kumaun Himalya), India, was analyzed in relation to physico-chemical variables. Phytoplankton biomass ranged from 2.7 to 20.0 g m⁻³ in the euphotic zone of the lake. Dinoflagellates monopolized the algal community with a mean annual contribution of 94.5 % to the total phytoplankton biomass. The community coefficient used to quantify the seasonal changes in algal population reflected the fact that successional episodes were not very significant, the percentage similarity among the consecutive algal samples ranging from 47.8 to 89.9 %. The phytoplankton community was characterized by low species richness, low equitability and species diversity. Various ecological characteristics of the community are discussed and the phytoplankton biomass is also compared with that of some tropical and temperate lakes.     

Phytoplankton periodicity of the Waitaki Lakes,New Zealand

The Waitaki River system in the South Island of New Zealand includes three large glacially-formed headwater lakes, Tekapo, Pukaki and Ohau, which drain into the manmade Lake Benmore. Phytoplankton periodicity was followed from December 1975 to January 1980 as part of a study investigating possible changes in these lakes as a consequence of hydroelectric development. The phytoplankton was highly dominated by diatoms, e.g., Diatoma elongatum, Cyclotella stelligera, Asterionella formosa, and Synedra acus, but in lakes Ohau and Benmore populations of green algae occasionally developed. In all four lakes seasonal phytoplankton periodicity was observed with maximum biomass in spring and summer. In Lake Tekapo, the first lake in the chain, maximum biomass did not exceed 300 mg m^–3, but in the very turbid Lake Pukaki the maximum summer biomass ranged between 300 and 800 mg m^–3. In Lake Ohau, the least turbid lake, maximum biomass was around 1 000 mg m^–3. In the newly created Lake Benmore periodicity was less evident and summer maxima reached over 1 500 mg m^–3. The phytoplankton periodicity in these lakes is greatly influenced by seasonal patterns of turbidity from inflowing glacial silt.     

Growth, production and losses of phytoplankton in the lowland River Spree: carbon balance

1. Phytoplankton carbon assimilation and losses (exudation, dark carbon losses) as well as oxygen release and dark community respiration were measured regularly for 2 years at four stations along the lower Spree (Germany). Carbon balance of river phytoplankton was estimated using measured assimilation, metabolic losses and variations in algal carbon along a stretch of river. 2. The light/dark bottle method was modified to simulate vertical mixing. 3. Waxing and waning of phytoplankton populations dominated the load of particulate organic carbon as well as the oxygen budget of the river. 4. Phytoplankton assimilated 310–358 g C m^?2 yr^?1. A mean value of 586 mg C m^?3 day^?1 was fixed in photosynthesis, with 16.7 mg C being exuded during the day and 20.1 mg lost at night. The measured dark respiration was equivalent to only 28% of the daily gross oxygen production of the plankton community. Phytoplankton washed from upstream lakes and reservoirs was not measurably damaged by turbulent transport. 5. In spring, 18–22% of assimilated carbon was used for net biosynthesis of phytoplankton along the river course. At this time, the carbon balance of this part of the Spree was dominated by autochthonous net production. During summer, however, total carbon losses exceeded the intensive carbon assimilation. The decline of algal biomass along the river course in summer was not explicable by measurable physiological losses. The importance of sedimentation and grazing losses is discussed.     

Post‐Impoundment Biomass and Composition of Phytoplankton in the Yangtze River

Damming, and thus alteration of stream flow, promotes higher phytoplankton populations and encourages algal blooms (density >10⁶ cells L^–1) in the Three Gorges Reservoir (TGR). Phytoplankton composition and biomass were studied in the Yangtze River from March 2004 to May 2005. 107 taxa were identified. Diatoms were the dominant group, followed by Chlorophyta and Cyanobacteria. In the Yangtze River, algal abundance varied from 3.13 × 10³ to 3.83 × 10⁶ cells L^–1, and algal biomass was in the range of 0.06 to 659 mg C m^–3. Levels of nitrogen, phosphorus and silica did not show consistent longitudinal changes along the river and were not correlated with phytoplankton parameters. Phytoplankton abundance was negatively correlated with main channel discharge (Spearman r = –1.000, P < 0.01). Phytoplankton abundance and biomass in the Yangtze River are mainly determined by the hydrological conditions rather than by nutrient concentrations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Phytoplankton dynamics in the Congo River

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Nutrient-phytoplankton relationships in a tropical meromictic soda lake

Seasonal variation through one year in total nitrogen (TN), total phosphorus (TP), phytoplankton biomass, phytoplankton species composition and other environmental factors were examined in Lake Sonachi, a tropical meromictic soda lake. Mean concentrations of TN and TP were 11 000 µg N l^-1 and 100 µg P l^-1, respectively. Maximum concentrations of TN and TP occurred in the monimolimnion. Phytoplankton biomass ranged from 350 to 1260 mg m^-3. Synechococcus bacillaris, a small coccoid cyanophyte, dominated the phytoplankton. The mean chlorophyll a concentration of 37 mg · m^-3 was a modest value when compared with those of other tropical soda lakes. High TN:TP ratios indicated phosphorus limitation in the lake.     

Phytoplankton dynamics in the stratified water column of Lake Bonney,Antarctica

Phytoplankton populations in perennially ice-covered Lake Bonney, Antarctica grow in a unique non-turbulent environment. The absence of turbulence generated by winds or major streams, combined with strong vertical gradients in temperature and nutrients, create vertically stratified environmental conditions that support three discrete phytoplankton populations in the east lobe of this lake. Phytoplankton biomass and photosynthesis were measured in the east lobe of Lake Bonney during the winter-spring transicion (September) to mid-summer (January). During this period, irradiance beneath the ice increased from 0.03 to 1.9 mol quanta m⁻² d⁻¹. Chlorophylla concentrations ranged from 0.03 to 3.8 μl⁻¹ within the trophogenic zone (just beneath the permanent ice cover to 20 m) and photosynthesis ranged from below detection to 3.2 μg Cl⁻¹ d⁻¹. Our results indicate: (1) phytoplankton photosynthesis began in late winter (before 9 September, our earliest sampling date); (2) maxima for phytoplankton biomass and production developed sequentially in time from the top to the bottom of the trophogenic zone, following the seasoral increase in irradiance; and (3) the highest photosynthetic efficiencies occurred in early spring, then decreased over the remainder of the phytoplankton growth season. The spring decrease in photosynthetic rates for shallower phytoplankton appeared to be related to nutrient availability, while photosynthesis in the deeper populations was solely lightdependent.     

The Seasonal Dynamics and Composition of Photosynthetic Picoplankton Communities in Temperate Lakes in Ontario,Canada

The seasonal abundance and composition of photosynthetic picoplankton (0.2-2 μm) was compared among five oligotrophic to mesotrophic lakes in Ontario. Epilimnetic picocyanobacteria abundance followed a similar pattern in all lakes; maximum abundance (2-4 × 10⁵ cells · ml⁻¹) occurred in late summer following a period of rapid, often exponential increase after epilimnetic temperatures reached 20 °C. In half of the lakes picocyanobacteria abundance was significantly correlated with temperature, while in other lakes the presence of a small spring peak resulted in a poor correlation with temperature. In all lakes there was a significant correlation between epilimnetic abundance and day of the year. Correlations with water chemistry parameters (soluble reactive phosphorus, total phosphorus, particulate C: P and C: N) were generally weaker or insignificant. However, in the three lakes with the highest spring nitrate concentrations, a significant negative correlation with nitrate was observed. During summer stratification, picocyanobacteria abundance reached a maximum within the metalimnion and at or above the euphotic zone (1% of incident light) in all lakes. These peaks were not related to nutrient gradients. The average total phytoplankton biomass ranged from 0.5 g m⁻³ (wet weight) in the most oligotrophic lake to 1.4 g m⁻³ for the most mesotrophic with picoplankton biomass ranging from 0.01 g m⁻³ to 0.3 g m⁻³. Picocyanobacteria biomass comprised 1 to 9 % of total phytoplankton biomass in late summer, but in one year for one lake represented a maximum of 56%. Other photosynthetic picoplankton (unidentified eukaryotes, Chlorella spp. Nannochloris spp.), although less abundant (10³ cells · ml⁻¹) than picocyanobacteria, represented biomass equal or greater than that of the picocyanobacteria in spring and early summer. On average, half of the photosynthetic picoplankton biomass was eukaryotic in the more coloured lakes, while in the clear lakes less than 20% was eukaryotic. Among the lakes there was a significant positive correlation between the average light extinction coefficient and the proportion of eukaryotic biomass of the picoplankton. In mesotrophic Jack's Lake, the contribution of picoplankton to the maximum photosynthetic rate ranged from 10 to 47% with the highest values in the spring (47%) and late summer (33%), as a result of eukaryotic picoplankton and picocyanobacteria respectively. Picocyanobacteria cell specific growth rates were high during July (0.6-0.8 day⁻¹) and losses were close to 80% of the growth rate. Thus, despite low biomass, photosynthetic picoplankton populations appeared to turn over rapidly and potentially contributed significantly to planktonic food webs in early spring and late summer.     

Nutrient Requirement and Growth of a Synechococcus Species Isolated from Lake Balaton

A pico sized Synechococcus species isolated from Lake Balaton was studied in batch and continuous cultures. This picocyanobacterium had a pH optimum at 8.5 and a temperature optimum at 28-30°C. The I_k value for growth was 52 μEinstein m⁻² S⁻¹, the maximum growth rate 2.27 d⁻¹, the half saturation Constant of growth 1.2 μg PO₄-P I⁻¹ and the minimal cell quota 1.74 nig P g dry weight⁻¹. The dry weight of cells showed a minimum, the chlorophyll-a/biomass ratio a maximum as a function of growth rate. Above the quota of 3.4 fg P Cell⁻¹ significant amounts of non-reactive dissolved Phosphorous were released.     

Primary Productivity and Activity Coefficients of the Phytoplankton of a Mesotrophic Soft-Water Lake (Piburger See,Tirol, Austria)

Phytoplankton primary production was measured using the ¹⁴C method once per month from 1973 through 1976 as part of an intensive ecosystem study of a small eutrophic soft-water lake, under restoration since 1970. Relationships among phytoplankton production, species composition, chlorophyll a content, bacteria, zooplankton and a variety of abiotic environmental factors have been studied. Productivity normally showed one peak in spring and another in summer, whereas a minimum was reached under the ice cover in February or March. Maximum production rates in the depth profile ranged from 3 to 144 mg C · m⁻³ · d⁻¹, integral production from 6 to 510 mg C · m̄⁻² · d⁻¹. Species of Cyanophyceae, Dinophyceae, Chlorophyceae and Chrysophyceae dominated alternately and showed significant differences in the level and variation of photosynthetic activity. Maximum activity was observed in summer. A high biomass increase during late winter and spring despite low primary productivity resulted from the immigration of the dominant blue-green alga, Oscillatoria limosa, from the sediment. Energy efficiency increased not only with depth in the light-limited parts of the euphotic zone but at all depths during bad weather conditions and during the decrease of irradiance in autumn.     

Biomass size spectra of net plankton in the adjacent area near the Yangtze River Estuary in spring

Based on data from survey carried out in spring 2005, the biomass size spectra of net plankton were explored in the adjacent sea of Yangtze River Estuary. Results revealed an approximately continuous size distribution of plankton individuals, from phytoplankton (5–250 μm cell^?1 in equivalent sphere diameter (ESD), 15 pg–146 ng C cell^?1) to zooplankton (120 μm–2 cm ESD, 115 ng–7.5 mg C ind^?1). The normalized spectra (carbon scale) were linear with slope ranged from –0.889 to –0.445, and intercept ranged from 12.866 to 16.863 (all stations together, slope = –0.606, intercept = 19.448), indicating strong deviations from the ideal value (slope = –1.22) of a steady pelagic ecosystem. Correlation analysis presented that intercept and regression coefficient of net plankton size spectra had significant relationship with plankton biomass size diversity.     

Primary Production and Effects of Enrichment with Nitrate and Phosphate on Phytoplankton in the Barra Bonita Reservoir (State of São Paulo,Brazil)

Primary productivity of the phytoplankton was evaluated by the ¹⁴C and dissolved oxygen methods in December 1981 at the Barra Bonita Reservoir (São Paulo State, Brazil). The primary production varied between 0.17 to 14.51 mg C m⁻³h⁻¹ at 4 and 0 m depth, respectively. About 57 to 94% of the photosynthetic activity was due to phytoplankton > 50 μm. The highest value of assimilation rate (3.36 mg C mg Chl⁻¹h⁻¹) was found in the surface water. Dissolved nutrient concentrations were very high and consisted mainly of nitrate. Light penetration was low, the aphotic zone accounting for about 90% of the water column. Enrichment with nitrate and phosphate showed that both N and P stimulated the production of biomass (chlorophyll a), mainly due to the addition of phosphate. The enrichment experiment also indicated that phosphate addition has a significant stimulatory effect on the growth of Melosira sp. The limiting effect of light penetration on photosynthetic activity is more severe than that of nutrients.     

Seasonal and Interannual changes of chemical characteristics and phytoplankton in a mountain lake of the Eastern Italian Alps (Lake Calaita,Trentino)

Measurements at Lake, Calaita, a small mountain lake located at 1605 m. a.s .l. in a metamorphic catchment area in the south of the Trentino Region (Northern Italy), have revealed great seasonal variations in the chemical characteristics and phytoplankton community during the ice free period in 1992 and 1993. The acidity present in wet precipitations (H⁺, NH₄⁺) was neutralised within the drainage basin by mineral dissolution which led to an increase of basic cations and alkalinity in the runoff. The dilution during periods of higher discharge, e.g. in spring and autumn, resulted in low values of alkalinity (up to 60 μeq 1⁻¹), pH (mostly <6.7) and conductivity (<8 μS cm⁻¹, 20°C). In summer, the decrease in runoff caused higher alkalinity (>10 μeq 1⁻¹), pH (6.9–7.4) and conductivity values (up to 30 μS cm⁻¹). The phytoplankton showed a major development in summer (with biovolume values of up to 7000 mm³ m⁻³), two different taxa being dominant in 1992 (Oocystis cf. lacustris) and 1993 (Synedra sp.). Unpredictable climatic conditions have a strong influence on the physical stability of the lake, which makes it more difficult to explain the evolution of the phytoplankton community as opposed to deeper lakes.     

Production and Utilization of Dissolved Organic Carbon During in situ Phytoplankton Photosynthesis Measurements

Rates of phytoplankton photosynthesis, extracellular release of dissolved organic carbon, and production or utilization of dissolved organic carbon during in situ incubation were measured in a soft-water Vermont lake during summer thermal stratification. Phytoplankton photosynthesis rates were frequently in the range of 300–600 mg C m⁻² of lake surface day⁻¹; extracellular release of previously fixed organic carbon was generally in the range of 20–75% of the carbon incorporated into cell biomass, as determined by gas-phase radio-analysis. Rates of increase or decrease in total dissolved organic carbon occurring in light and dark incubated phytoplankton samples, during brief (4 hour) in situ measurements, indicate that a significant fraction of the total dissolved organic carbon „pool”︁ is probably labile and rapidly being cycled.     

Indirect effect of different fish communities on nutrient chlorophyll relationship in shallow hypertrophic water quality reservoirs

Effects of different fish communities on the proportion of different nitrogen and phosphorous forms and the amount of phytoplankton (chlorophyll a) were examined in two consecutive years (1992–1993) in three Hungarian shallow water reservoirs (Cassette and outer reservoir of the Kis–Balaton Water Protection System, and Marcali reservoir). Possible interactions between nutrient concentrations and the amount of phytoplankton in these reservoirs were also examined. Considerable differences in the proportions of different nutrient forms were observed between the three test sites, which could be explained by the presence of different fish stocks in these reservoirs. In the Cassette, the fish biomass necessary for a water quality improvement was around 50 kg ha⁻¹. Phytoplankton biomass was controlled by the zooplankton, consequently chlorophyll a concentrations decreased considerably, while those of dissolved nutrients significantly increased. In the outer reservoir, phytoplankton was controlled bottom-up, since the 250 kg ha⁻¹ fish biomass was larger than the critical value due to the high proportion of planktivorous species. Chlorophyll a concentrations were high, and nutrients were mainly in particulate form (in algal cells). In the Marcali reservoir, the recently introduced silver carp population could not control fully the phytoplankton. The biomass of phytoplankton decreased only slightly, while its composition changed considerably. Although biomanipulation with silver carp is suitable for ceasing cyanobacterial blooms, reduction of the amount of planktivorous fish seems to be a more adequate method for increasing water transparency, rather than introduction of phytoplankton feeding fish.

     

Organic Carbon Flux to a Large Salt Lake: Pyramid Lake,Nevada, USA

Energy flux to a large, deep, salt lake from phytoplankton, periphyton and macrophyte primary production as well as fluvial transport and wind-transported terrestrial vegetation and dust were quantified. Average areal phytoplankton net photosynthesis was 511 mg C m⁻² d⁻¹. Highest rates were during water-blooms of the bluegreen alga, Nodularia spumigena. Although areal daily net photosynthesis by periphyton in Pyramid Lake was comparable to other salt lakes, annual carbon influx by periphyton was small due to the lake's graben morphology and moderate euphotic depth (mean, 11.9 m). Macrophytes were uncommon and, therefore a minor source of energy. Truckee River is the only major fluvial discharge to Pyramid Lake and dissolved organic carbon was the principal organic carbon fraction in river water. Large upstream water diversions coupled with several drought years resulted in an average fluvial organic carbon load of only 7.3 g Cm⁻²y⁻¹ or 4% of median phytoplankton net photosynthesis. Tumbleweeds were the most common terrestrial plant material observed in Pyramid Lake comprising a maximum projected importance of 6% of total annual carbon input. Windborne dust represented < .1% of annual carbon input. Phytoplankton primary production is the predominant energy source to Pyramid Lake, accounting for over 80% of annual carbon influx. The relative magnitude of autochthonous and allochthonous vectors to the annual carbon budget of this desert salt lake are comparable to those of the few other large lakes for which detailed energy input budgets have been calculated.     

Phytoplankton biomass and primary productivity of of Lake Leake and Tooms Lake,Tasmania

Phytoplankton biomass and primary productivity were studied in two lakes in eastern Tasmania. Low standing crops (7–746 and 42–180 mm³m⁻³ for Lake Leake and Tooms Lake respectively) and low primary productivity (approx. 9 g C m⁻² yr⁻¹ for both lakes) indicate extreme oligotrophy. During a period when biomass remained constant in Lake Leake the hourly assimilation rate in constant light conditions varied seasonally, indicating physiological adjustment by the algae (“light adaptation”). The relationships between plankton biomass and carbon assimilation are discussed.     

Composition and Productivity of the Benthic Macroinvertebrate Community of a Subtropical Reservoir

Physical-chemical conditions, phytoplankton productivity, community structure and productivity of the macroinvertebrate benthic community were determined during 1976–77 in a subtropical reservoir. Physical-chemical results revealed high nitrate and phosphate concentrations with highest values in the riverine segment. Large phytoplankton populations were present during most of the year. Phytoplankton productivity was high, producing an annual mean of 87 mg C · m⁻³ · h⁻¹ (12 hours light day). High turbidity in the riverine segment limited phytoplankton productivity during winter and spring. Macrobenthos was dominated by chironomids (Chironomus, Procladius, Coelotanypus and Tanypus) and oligochaetes (Limnodrilus). The annual mean benthic population was estimated at 1,626 · m⁻² with a mean dry weight of 0.66 g · m⁻². Mean benthic species diversity was 1.80. A lacustrine-riverine community gradient was revealed. Benthic productivity was 6.8 g · m⁻² · yr⁻¹ (dry weight) with a P: B ratio of 10. A low correlation was observed between benthic and phytoplankton productivity, and between phytoplankton standing crop and benthic macroinvertebrate numbers throughout the reservoir. Algal food supplies had little impact on the benthic community which was composed predominately of species which fed mostly on organic detritus. Stressful conditions caused by low dissolved oxygen concentrations probably inhibited development of the benthic community throughout the reservoir during summer months, while high sedimentation rates limited development in the head waters.