Phytoplankton Population Density Research Articles

Chlorophyll a as a measure of seasonal coupling between phytoplankton and the monsoon periods in the Gulf of Oman

We present data from a long time-series study to describe the factors that control phytoplankton population densities and biomass in the coastal waters of Oman. Surface temperature, salinity, nutrients, dissolved oxygen, chlorophyll a (Chl a), and phytoplankton and zooplankton abundance of sea water were measured as far as possible from February 2004 through February 2006, at two stations along the southern coast of the Gulf of Oman. The highest concentrations of Chl a (3 mg m−3) were recorded during the southwest monsoon (SWM) when upwelling is active along the coast of Oman. However, results from our study reveal that the timing and the amplitude of the seasonal peak of Chl a exhibited interannual variability, which might be attributed to interannual differences in the seasonal cycles of nutrients caused either by coastal upwelling or by cyclonic eddy activity. Monthly variability of SST and concentrations of dissolved nitrate, nitrite, phosphate, and silicate together explained about 90% of the seasonal changes of Chl a in the coastal ecosystem of the Gulf of Oman. Phytoplankton communities of the coastal waters of Oman were dominated by diatoms for most part of the year, but for a short period in summer, dinoflagellates were dominant.

Changes in Phytoplankton Population along the Saline Gradient of the Júcar Estuary and Plume

This paper presents the results of phytoplankton counts carried out with epifluorescence at five sampling stations: two in the Júcar River Estuary and the other three in the region of freshwater influence of the Júcar River. From June 2002 to July 2003, nine sampling campaigns were carried out as a part of the EU's ECOSUD project. Two of these campaigns (the 2nd and 8th) were selected for analysis. These sampling campaigns represent two different conditions: in the 2nd campaign the discharge of the Júcar River was almost null, while in the 8th campaign it was significantly higher.Along the salinity gradient, as the influence of fresh water and nutrient loads decreases, a decrease in the population density of eukaryotic phytoplankton was observed. Typical freshwater phytoplankton groups (colonial cyanobacteria and chlorophyceae) clearly decrease in density and percentage as salinity increases. In general, picocyanobacteria exhibit the opposite behavior. The behavior pattern of groups with species adapted to fresh water and seawater is less clear. The density of these groups (diatoms and prymnesiophytes) is highest in the salt-wedge area due to nutrient accumulation. However, the densities are generally higher at the freshwater stations than in the marine environment. The vertical distribution at the estuarine stations shows clear density maximums in the interface area, which seems to have two causes: the retention of senescent phytoplankton affected by saline shock in this quiescent area and the growth of phytoplankton that exploit the accumulated nutrients.

Seasonal variations in phytoplankton populations in Ogelube Lake, a small natural West African Lake

AbstractWater samples were collected on a monthly basis at three locations along the north–south axis of the lake at 1 m depth intervals for 1 year. A sedimentation technique was used for microscopic examination of the samples. The monthly mean and seasonal phytoplankton densities were calculated. The original data were square‐root transformed, and analysis of variance performed with SPSS version 10.0. The significant treatment effects were determined using Fisher's least significance difference at the 5% probability level. The mean phytoplankton population per millilitre was very high for the entire sampling period. There was a phytoplankton bloom formation in the early rainy season, with the mean total phytoplankton population density for the rainy season (April–October) being significantly higher than that of for the dry season (November–March). A population increase was observed during the late part of the dry season to the early part of the rainy season. During the rainy season, Chlorophyceae (mostly desmids) were most abundant, followed by Cyanobacteria, Bacillariophyceae, Euglenophyceae, Dinophyceae, Cryptophyceae, Chrysophyceae and Xanthophyceae, in decreasing order of abundance. This order changed slightly in the dry season, when there was relative abundance of Bacillariophyceae over Cyanophyceae, and Dinophyceae over Euglenophyceae. The low population of Euglenophyceae indicates that the organic pollution is still low, with the predominance of desmids, indicating an oligotrophic lake condition.

Are phytoplankton population density maxima predictable through analysis of host and viral genomic DNA content?

Phytoplankton:virus interactions are important factors in aquatic nutrient cycling and community succession. The number of viral progeny resulting from an infection of a cell critically influences the propagation of infection and concomitantly the dynamics of phytoplankton populations. Host nucleotide content may be the resource limiting viral particle assembly. We present evidence for a strong linear correlation between measured viral burst sizes and viral burst sizes predicted from the host DNA content divided by the viral genome size, across a diversity of phytoplankton:viral pairs. An analysis of genome sizes therefore supports predictions of taxon-specific phytoplankton population density thresholds beyond which viral proliferation can trim populations or terminate phytoplankton blooms. We present corollaries showing that host:virus interactions may place evolutionary pressure towards genome reduction of both phytoplankton hosts and their viruses.

Species composition and population density of Phytoplankton of Great Bitter Lake, Suez Canal, Egypt.

The structure and dynamic of phytoplankton assemblages in Great Bitter Lakes were studied seasonally duringthe period from May 1999 to February 2000. Population density varied between112198X103 cells. l-1 in springand 2382X106 cells. l-1 in winter. In terms of cell number, Bacillariophyceae was the most important group(mean annual percentage contribution was 67%), which remained dominant throughout the study period.Cyanophyceae ranked the second abundant group (14 %) dominated in autumn and winter. The contribution ofDinophyceae and Chlorophyceae were 8.6 and 7.3% respectively. The other classes contributed with very lowshare of the total phytoplankton. The relationship between phytoplankton composition and physico-chemicalvariables was studied. CCA analysis indicated that water salinity, and temperature are the most important factorsaffecting phytoplankton distribution. The trophic status index indicated that the lake ranked betweenmesotrophic and moderately eutrophic. In winter, the lake was under blooming due to the luxuriance growth ofNitzschia pseudo delicatissima Hasle. and Phormidium sp. The impact of pollution was significantly effective inthe western side of the lake compared to the eastern one.

Phytoplankton in an Amazonian flood-plain lake (Lago Batata, Brasil): diel variation and species strategies

Phytoplankton diel variations in an Amazonian flood-plain lake (Lago Batata) were studied quarterly for 1 year, according to the hydrometric level fluctuation of the Trombetas river (39.7-47.0 m over sea level), to which the lake is permanently connected. Hydrological and hydro- graphic conditions determined mixing patterns of the water column and phytoplankton distribution. When the lake is deep (>4.0 m), sparse phytoplankton communities are found at the bottom, by thermal discontinuities, and may remain so for a short duration (days). When the lake is shallow (<4.0 m), mixing of the waters ensures a nearly even distribution of organisms throughout the water column. The weak stability of stratification is a major influence on the distribution of phytoplankton popu- lation densities in this shallow flushed lake. The highest phytoplankton densities during the second part of the day, mentioned in the literature, are observed only during decreasing water level. During the other phases of the hydrological cycle (increasing, high and low water levels), no differences in phytoplankton population density were observed throughout the diel cycle. Assemblages, or groups of descriptor species of systems having similar features, have recently been proposed. Assemblages of flushing-tolerant nano-algae (X1) and of mixing-dependent species (T, S) have shown that the physical properties of the environment were often the strongest determinants of the phytoplankton strategies.

Trophodynamic structure of a swampy bog at the clymax stage of limnological succssion I. Prmary production dynamics

Effect of emergent vegetation on the population dynamics of phytoplankton community in Matsumi-ike Bog, a typical bog at the climax stage of limnological succession, was studied. The emergent vegetation grew until August and then withered and collapsed mainly during December and January, supplying the debris of emergent plants into the water column. Population density of the predominant phytoplankton showed sinusoidal fluctuation affected primarily by the water temperature, with various lag phases due to the function of other environmental factors. Shading by the emergent vegetation shifted the initiation of phytoplankton fluctuation earlier. This fluctuation patterns was most obvious among those phytoplankton contain chlorophyll-a and -b, but non -a and-c. The population dynamics were also compared with that of Matsumi-ike Bog at premature stages without (8 yr ago) or with littoral vegetations (3 yr ago). The population density of phytoplankton with chlorophyll-b decreased but those with chlorophyll-c increased, due to the shading effect of the emergent vegetation with the limnological succession of the bog. At the climax of succession, the dynamic state of phytoplankton community has become more stable.

Microphytoplankton of the Pitchavaram mangals, southeast coast of India: species composition and population density

Species richness of phytoplankton of the Pitchavaram mangals was high. There were 82 species constituted by 67 species of diatoms, 12 species of dinoflagellates and 3 species of bluegreen algae. The diatoms formed the bulk with 72% followed by the dinoflagellates with 15%, in which there were autochthonous (temporary and permanent) and allochthonous forms. Phytoplankton population density exhibited a wide seasonal fluctuation with the minimum during monsoon and the maximum during summer, suggesting the possible differential influence of various environmental factors.

Phases in the development of riverine plankton: Examples from the rivers Rhine and Meuse

Observations on phyto and zooplankton in two hydrographically different rivers were compared in order to discriminate phases in plankton development. Along the longitudinal axis of the River Rhine a gradual increase in the development of phytoplankton was observed, which reached its maximumca. 100 km before the river flows into its artificial sedimentation area. The development of rotifer populations was slightly retarded as compared with that of phytoplankton and highest population densities were only reached in the sedimentation area. Crustaceans developed in significant numbers, not until the river water had entered the sedimentation area. Development of zooplankton coincided here with a strong decrease in the density of phytoplankton. A similar trend in plankton development was observed in the River Meuse, although in this river the highest densities of phyto and zooplankton already occurred in its middle reaches. The differences in the timing of plankton growth in the two rivers are probably caused by differences in flow regime between both rivers. The River Rhine, which is fed by rainwater and melting of glaciers in the Alps, has a relatively constant discharge. On the other hand, the low discharge of the rain-fed River Meuse combined with an increased residence time of the water as a consequence of large numbers of weirs, allows a full cycle of plankton development long before its discharge into the sea. This phenomenon was also reflected in the silicate cycle in the Meuse, where the consumption by planktonic diatoms and the regeneration of silicate of deposits seem to be important. In contrast, in the main branches of the River Rhine only the effects of silicate consumption were detectable.

Phases in the development of riverine plankton: Examples from the rivers Rhine and Meuse

Observations on phyto and zooplankton in two hydrographically different rivers were compared in order to discriminate phases in plankton development. Along the longitudinal axis of the River Rhine a gradual increase in the development of phytoplankton was observed, which reached its maximumca. 100 km before the river flows into its artificial sedimentation area. The development of rotifer populations was slightly retarded as compared with that of phytoplankton and highest population densities were only reached in the sedimentation area. Crustaceans developed in significant numbers, not until the river water had entered the sedimentation area. Development of zooplankton coincided here with a strong decrease in the density of phytoplankton. A similar trend in plankton development was observed in the River Meuse, although in this river the highest densities of phyto and zooplankton already occurred in its middle reaches. The differences in the timing of plankton growth in the two rivers are probably caused by differences in flow regime between both rivers. The River Rhine, which is fed by rainwater and melting of glaciers in the Alps, has a relatively constant discharge. On the other hand, the low discharge of the rain-fed River Meuse combined with an increased residence time of the water as a consequence of large numbers of weirs, allows a full cycle of plankton development long before its discharge into the sea. This phenomenon was also reflected in the silicate cycle in the Meuse, where the consumption by planktonic diatoms and the regeneration of silicate of deposits seem to be important. In contrast, in the main branches of the River Rhine only the effects of silicate consumption were detectable.

Phytoplankton population density and volume as indicators of eutrophication in the eastern part of the Adriatic Sea

Population density and volume-biomass of microplankton, nanoplankton and total phytoplankton were analyzed at 14 stations along the eastern part of the Adriatic Sea. Based upon data frequency distribution, four categories of ecosystems were established in the investigated area. Criteria for ecosystem categorization and biological evaluation of eutrophication are proposed.

A stratified sampling approach to compensating for non-random sedimentation of phytoplankton cells in inverted microscope settling chambers

A pronounced “edge effect” resulting in non-random cell sedimentation is documented for standard-design inverted microscope counting chambers. Comparison of mean cell densities of two green algae from random fields in central and peripheral regions of chambers substantiate a marked peripheral settling bias. The non-random settling pattern is independent of phytoplankton cell size and population density over the ranges encountered in this analysis. If this problem is not compensated for, the magnitude of the bias is such that large errors in estimates of mean cell density/chamber can result. A stratified sampling approach is developed to minimize the error resulting from non-random settling without increasing the amount of time spent enumerating cells. Counting of random fields rather than patterned transects is strongly recommended as the standard procedure in phytoplankton studies.

Sampling designs for the estimation of phytoplankton abundance in limnetic environments

Several of the problems of devising efficient practical sampling schemes for estimating average phytoplankton population densities are described. The paper presents a stratified random sampling scheme with two stages of sub-sampling for estimating the concentration of chlorophyll a and several planktonic alga species in two experimental enclosures in Blelham Tarn in the English Lake District. In the example, the algae were always heterogeneously distributed. Though stratification reduced the estimator variance by as much as 50% for some species and sampling dates; for some other occasions and species there was no improvement over simple random sampling. The total variation in density was broken down into the various components of variance, which showed that generally there was little variation due to sub-sample and measurement effects compared to the natural remaining density variation between the sample units within each strata. This suggested that future sampling schemes in these areas might be more eff...

Limnological contrasts and anomalies in two adjacent saline lakes

Differences in physical, chemical, and biological conditions in two small (<20 ha) saline lakes less than 1 km apart in south-central British Columbia are examined. Although the lake basins are morphometrically similar, differences in their watershed geology and topography in large part may be responsible for the more saline lake showing severe and anomalous meromictic features while the less saline lake exhibits normal dimictic characteristics. Bacterial and phytoplankton population densities and production profiles of the lakes are compared along with some aspects of their zooplankton populations.

そう類生産の潜在力（ＡＧＰ）測定による博多湾における富栄養化の評価

An investigation was pursued on the eutrophication problem in Hakata Bay from June 1981 to April 1982. By the chemical analysis and the examination for Phytoplankton of the water samples collected from the surface and bottom of several stations, it was proved that eutrophication was remarkable in the eastern region of the bay.The population density of phytoplankton revealed a range of 44 to 2, 200 cells/ml in the western region, while the density frequently exceeded a level of 20, 000 cells/ ml in the central and eastern regions. Several species of diatoms and flagellates were found in the red tides developed in the bay during the investigation period.In addition, Algal Growth Potential (AGP) was determined in the water samples by the use of Skeletonema costatum and Olisthodiscus sp., and the ratio of AGP to COD value in Hakata Bay was caluculated. Thus, the range of 0.44 to 0.80 and 0.27 to 0.60 were obtained respectively by the former plankton and by the latter. In conclusion, the results obtained from the ratio suggested the fact that eutrophication more profoundly proceeds in Hakata Bay under the optimal condition of phytoplankton growth.

Effects of Differential Growth and Mortality in the Seasonal Succession of Phytoplankton Populations in Lawrence Lake, Michigan

An investigation was made of factors controlling algal succession in a small, oligotro- phic lake during summer stratification. Phytoplankton population densities, growth rates, sedimen- tation losses, and mortality due to zooplankton grazing were measured weekly. Cyclotella michigan- iana was the dominant alga through the end of June, at which time Cyclotella comensis began to increase, becoming the dominant by August. In August, high grazing pressure caused the rapid declines of both C. michiganiana and C. comensis, which were followed by an increase of Sphaer- ocystis schroeteri. The combined effect of greater growth rates and lower loss rates of C. comensis resulted in its dominance over C. michiganiana. In contrast, the C. comensis-S. schroeteri succes- sion clearly resulted from differential mortality alone. It is likely that losses due to sedimentation and/or grazing are important in many lakes and that interspecific competition may be less important in actually controlling seasonal succession.

Recent Changes in the Phytoplankton of Lake Michigan Near Chicago

Daily counts show that during the years 1972-75, phytoplankton population density near the Chicago shoreline of Lake Michigan averaged 50% lower than during the preceding 4 years, and lower than in any 4-year period since 1953-56. The decrease from 1968-71 to 1972-75 resulted mainly from large decreases in the spring and fall maxima of diatoms. Proportionally, by far the greatest decreases were in Stephanodiscus binderanus and other Stephanodiscus species. Fragilaria, Asterionella, and Tabellaria decreased, while there was a statistically insignificant increase in Melosira. Very small populations of flagellates and green algae were not significantly different in the two periods; Blue-green algae increased in abundance, but remained a very small fraction of the total phytoplankton. The changes suggest a partial reversal of cultural eutrophication in this region of Lake Michigan, although other explanations cannot be ruled out.

The digital simulation of river plankton population dynamics

This paper deals with the development of a mathematical model for and the digital simulation in Fortran IV of phytoplankton and zooplankton population densities in a river using previously developed rate expressions. In order to study the relationships between the ecological mechanisms involved, the simulation parameters were varied illustrating the response of the ecosystem to different conditions, including those corresponding to certain types of chemical and thermal pollution. As an investigation of the accuracy of the simulation methods, a simulation of the actual population dynamics of Asterionella in the Columbia River was made based on approximations of conditions in that river. Although not totally accurate, the simulation was found to predict the general annual pattern of plankton growth fairly well and, specifically, revealed the importance of the annual velocity cycle in determining such patterns. In addition, the study demonstrates the usefulness of digital simulations in the examinations of certain aquatic ecosystems, as well as in environmental planning involving such examinations.

The digital simulation of river plankton population dynamics

This paper deals with the development of a mathematical model for and the digital simulation in Fortran IV of phytoplankton and zooplankton population densities in a river using previously developed rate expressions. In order to study the relationships between the ecological mechanisms involved, the simulation parameters were varied illustrating the response of the ecosystem to different conditions, including those corresponding to certain types of chemical and thermal pollution. As an investigation of the accuracy of the simulation methods, a simulation of the actual population dynamics of Asterionella in the Columbia River was made based on approximations of conditions in that river. Although not totally accurate, the simulation was found to predict the general annual pattern of plankton growth fairly well and, specifically, revealed the importance of the annual velocity cycle in determining such patterns. In addition, the study demonstrates the usefulness of digital simulations in the examinations of certain aquatic ecosystems, as well as in environmental planning involving such examinations.

The seasonal phytoplankton cycles of two saline lakes in central Washington1

Soap Lake and Lake Lenore occupy adjacent basins in the Lower Grand Coulce, Washington, but show several strong limnological contrasts despite correspondence in rates and trends of heat storage. Seasonal events in the dynamics of phytoplankton and zooplankton populations generally coincide with different phases in thermal behavior of the lakes. Both lakes show a dramatic summer decline in phytoplankton population density, with spring and fall periods of more intense activity. In Soap Lake, which stratifies thermally in summer, a dense algal population is established in the metalimnion. The summer phytoplankton minima in both lakes coincide with maximum development of zooplankton populations, although there is no conclusive evidence that zooplankton grazing actually limits phytoplankton growth. The seasonal phytoplankton cycles may be more closely dependent on nutrient depletion in surface waters, and oxygen inhibition of photosynthesis might also be implicated. Close agreement was evident in 14C productivity measurements for both lakes, but these may have been affected by oxygen inhibition in light and dark bottles. Both lakes, however, are highly productive, and productivity estimates are comparable with those obtained for soda lakes elsewhere.