Variation Of Phytoplankton Community Research Articles

Winter phytoplankton community structure in three shallow temperate lakes during ice cover

The general model of seasonal phytoplankton succession in temperate lakes suggests that winter phytoplankton growth is minimal under ice-cover. However, some studies have found diverse phytoplankton communities during winter. The primary objectives of this study were to determine the species composition and the changes in the winter phytoplankton community structure under the ice. For 2 consecutive winters, phytoplankton samples were collected under ice-cover at 4 sites on 3 lakes in Arrowwood National Wildlife Refuge (ANWR), near Pingree, North Dakota. Ninety taxa were identified and enumerated. Densities of several of these taxa frequently exceeded 106 cells l−1. The winter phytoplankton communities in these lakes were dominated by flagellates, principally cryptomonads, a synurophyte (Synura uvella), small chrysophytes (Chrysococcus spp., Kephyrion spp.) and a dinoflagellate (Peridinium aciculiferum), as well as non-flagellate microchlorophytes (Monoraphidium spp., Ankistrodesmus spp., and Pseudodictyosphaerium sp.), a cyanobacterium (Gloeocapsa aeruginosa) and centric diatoms (Stephanodiscus minutulus, S. parvus and Cyclotella meneghiniana).

Eutrophication, Harmful Algal Blooms and Species Diversity in Phytoplankton Communities: Examples from the Baltic Sea

Eutrophication, Harmful Algal Blooms and Species Diversity in Phytoplankton Communities: Examples from the Baltic Sea

Herbivory in variable environments: an experimental test of the effects of vertical mixing and Daphnia on phytoplankton community structure

Phytoplankton communities in lakes are exposed to different within-season frequencies of heterogeneity in resource supply because of wind-induced vertical mixing. Effects of such heterogeneity, in conjunction with herbivory, on phytoplankton community structure have rarely been simultaneously examined, despite the fact that each factor can have large effects on phytoplankton composition and diversity. This study uses replicated oligotrophic mesocosms to examine the effects of herbivory and different scales of temporal heterogeneity in deepwater mixing. The pattern of vertical mixing alone had minor effects on phytoplankton community diversity and composition. The herbivore Daphnia caused a shift in phytoplankton composition to less edible types, based mainly on morphological features (spiny shapes and trichomes on cell walls) rather than size structure alone. Phytoplankton richness depended jointly on mixing frequency and large Daphnia biomasses. When systems were well mixed, with high encounter rates between predator and prey populations, phytoplankton community richness was lowest. By contrast, the systems that were least often mixed had highest richness. These results are related to limited encounter rates with infrequent mixing and to the availability of refuges from predation. Responses to different scales of temporal heterogeneity in these oligotrophic phytoplankton communities depend more on Daphnia feeding than on resource pulsing.

POPULATION DYNAMICS AND THE TOXICITY OF BLUE‐GREEN ALGAE IN THE NAKTONG RIVER, KOREA

Lee, J. A.1, Choi, A. R.1, Park, J. H.1 & Chung, I. K2 1Department of Environmental Science, Inje University, Kimhae 621‐749, Korea; 2Departement of Marine Science, Pusan National University, Pusan 609‐735, KoreaSeasonal and spatial variations of phytoplankton community were monitored at 16 sites along the Naktong River. Blue‐green algae appeared from May through November with dominant genera of Microcystis, Anabaena, Oscillatoria and Gomphosphaeria. Frequency and biomass of the genera became greater at lower reaches. The Microcystis were observed from May to October up to 85,750cells/ml. Six species of Microcystis were identified with morphological characteristics and M. aeruginosa was most dominant. There were significant relationships between biomass of Microcystis and NO‐3, TP and pH in water column. However, NH4+, PO4‐3 and N/P were not critical in successions to the Microcystis dominated community. Microcystis blooms were notable at water temperature higher than 25°C. Microcystis density in sediment was 3 orders of magnitude higher than water column. Anabaena density ranged up to 11,220cells/ml. Four species of Anabaena were identified and A. flos‐aquae was most dominant. Anabaena biomass was not related to temperature, NO3‐, TN, PO4‐3, TP and N/P of water column and the frequency of trichome with akinete and/or heterocyte were not related to these parameters. Microcystins were detected from May to November with yearly fluctuations. Microcystin‐RR was most dominant. Total 84.2% of algal materials with Microcystis exhibited toxicity of microcystin with maximum of 3,292μg/g dry wt. Total 12.5% of water column with Microcystis exhibited dissolved microcystin up to 3.3μg/l. Microcystin concentrations were positively related to Microcystis biomass and pH of water column. Anatoxin‐a was determined by FD‐HPLC analysis with NBD‐F and all concentrations were below the detection limit of 0.1μg/l.

Limiting Resources and the Regulation of Diversity in Phytoplankton Communities

Species diversity is a key concept in ecology, yet the mechanisms regulating diversity in most systems are not completely understood. To address this issue, we analyzed the relationship between phytoplankton diversity and limiting resources (N, P, Si, and light) over two summers in three lakes in the Yellowstone (Wyoming, USA) region. Diversity was highly variable along temporal and spatial axes within lakes. We discovered a strong positive correlation between diversity and the number of resources at physiologically limiting levels. Consistent with resource-competition theory, we found the highest diversity to occur when many resources were limiting. Conversely, the lowest diversity occurred when few resources were measured at limiting levels. Sensitivity analyses demonstrated that threshold levels of resources (below which growth is limited and above which there is saturation for the resource) appear to exist in the natural environment, and that diversity is regulated in part by absolute levels of resources available to phytoplankton in aquatic systems. Threshold levels are generally in agreement with those determined to be limiting in prior physiological experiments. Consistent with previous observations, among-lake comparisons yielded a significant negative relationship between species diversity and system productivity. This result tentatively supports the hypothesis that the proximity of individual phytoplankton plays a role in the strength of competitive interactions. Our results generally suggest that, even in dynamic environments, where equilibrium conditions are rare, resource competition among phytoplankton is a mechanism by which communities are continually structured.

Phytoplankton species diversity control through competitive exclusion and physical disturbances

Competitive exclusion theory suggests that phytoplankton species number in an assemblage at equilibrium will be limited to the number of simultaneously limiting resources, generally three or fewer. However, natural phyto‐plankton assemblages usually exhibit high species diversity, hence the concept of Hutchinson's “paradox of the plankton”. Recent works have suggested that this apparent paradox is a result of disturbances intermediate in frequency relative to the time period necessary for species succession to lead to equilibrium conditions (sensu Connell's intermediate disturbance hypothesis [IDH]). Moreover, evidence indicates that disturbances of intermediate intensities are also conducive to maintenance of high species diversity in phytoplankton communities. Using a long‐term data record from hypereutrophic subtropical Hartbeespoort Dam (South Africa) that was typically dominated by a single species, but annually subjected to physical disturbance, we demonstrate here that disturbances can indeed enhance phytoplankton species diversity. However, these data fail to support Connell's IDH per se, as moderate‐and high‐intensity disturbances yielded similarly high species diversity. These data also suggest that community resilience (the ability or time to return to predisturbed conditions) is negatively related to disturbance intensity, such that higher intensity disturbances maintained high diversity for longer periods of time relative to lower intensity disturbances.

Effects of nutrient recycling by zooplankton and fish on phytoplankton communities

In laboratory experiments we tested the hypothesis that nutrients supplied by fish and zooplankton affect the structure and dynamics of phytoplankton communities. As expected from their body size differences, fish released nutrients at lower mass-specific rates than Daphnia. On average, these consumers released nutrients at similar N:P ratios, although the ratios released by Daphnia were more variable than those released by fish. Nutrient supply by both fish and Daphnia reduced species richness and diversity of phytoplankton communities and increased algal biomass and dominance. However, nutrient recycling by fish supported a more diverse phytoplankton community than nutrient recycling by Daphnia. We conclude that nutrient recycling by zooplankton and fish have different effects on phytoplankton community structure due to differences in the quality of nutrients released.

Water Quality and Phytoplankton Communities in Intensive Shrimp Culture Ponds in Kung Krabaen Bay, Eastern Thailand

Abstract.Water quality and phytoplankton communities were studied in 20 intensive shrimp culture ponds and in the inlet and drainage canals at Kung Krabaen Bay, Eastern Thailand during the first shrimp crop of 1992. The grow‐out ponds were categorized into two groups: low stocking density (<60 PL/m2) and high stocking density (>60 PL/m2). The results showed that there were no significant differences in water quality between the two stocking density groups. Phytoplankton collected using a 60‐μm mesh net consisted of 79 genera with concentrations ranging from 1,822 to 72,527 cells/L from the first month up to the time of shrimp harvesting. Water quality deteriorated in high and low stocking density shrimp ponds, which had an influence on abundance and diversity of net phytoplankton communities. Biochemical oxygen demand and ammonia‐nitrogen were most closely related to abundance of net phytoplankton communities during the shrimp grow‐out period. Salinity, temperature, and dissolved oxygen appeared to play an important role in phytoplankton community variation in inlet and drainage canals. Phytoplankton community structure in drainage canals showed more variation than in ponds. The management implications of the results and recommendations for further studies are also considered.

Pollution-Induced Community Tolerance (PICT) in coastal phytoplankton communities exposure to copper

The toxic effect of copper to coastal phytoplankton communities was studied in 6 m3 enclosures during 15 days using the PICT (Pollution-Induced Community Tolerance) methodology. PICT, primary production, algal biomass, species composition and diversity in phytoplankton communities were measured in control enclosures and enclosures with 1, 3, 6 and 15 μg Cu l-1 added. Increased copper tolerances were induced in the enclosures with added copper and, related to the pooled mean value of the controls, the mean values for copper tolerance were significantly higher in enclosures with 1, 6 and 15 μg Cu l-1. In enclosures with 6 and 15 μg Cu l-1, photosynthetic activity was significantly depressed. Fundamental changes in taxonomic diversity and species composition occurred in enclosures with 15 μg Cu l-1. Algal biomass was not affected by the addition of copper. The distribution and concentration of copper in the enclosures showed that copper exposure was almost constant over time in the enclosures and was proportional to the amount of copper added to them. Our studies indicate that the PICT methodology is sensitive enough to detect even minor effects of copper on phytoplankton communities. The PICT measurements indicate effects from concentrations as low as 1 μg Cu l-1 in highly eutrophic coastal areas, where the bioavailability of copper is assumed to be low. Copper concentration in the fjord and control enclosures was high, about 0.5 μg Cu l-1, only a factor two below the effect concentration measured by PICT. These results are significant in view of the increased release of copper to the coastal marine environment as results of the substitution of copper-based ship paints for tri-n-butyltin (TBT) antifouling paints.

Multiple techniques for lake restoration

Lake Finjasjon is a shallow, eutrophic lake (area 1100 ha, mean depth 3 m, maximum depth 13 m) in southern Sweden. In the 1920s, the lake was clear, with a summer Secci depth of about 2 m. During the first half of the 20th century, untreated sewage from the town polluted the lake. In the 1930s, the lake began to show eutrophic characteristics, and in the 1940s, the cyanobacterium Gloetrichia echinulata dominated in summer. In 1949, the first municipal sewage treatment plant was built. The treatment was, however, insufficient, since the lake continued to be the recipient of the effluent with the result that the occurrence of cyanobacteria became more frequent. Species such as Microcystis and Anabaena caused skin rash and allergic symptoms among swimmers. The phosphorus load on Lake Finjasjon increased as the population of Hassleholm grew and reached a peak value of 65 tons annum−1 in 1965. In 1977, the sewage plant was rebuilt to include chemical flocculation, reducing the total external phosphorus load to about 5 tons annum−1. Despite this improvement the lake did not recover from its chronic and toxic cyanobacterial blooms. Phosphorus-leaking black sediments were identified as the cause of the lake’s failure to recover. Some 60% of lakebed area is covered with sediments on average 3 m thick. Dredging the sediments was started on a large scale in 1987. Five years later, 25% of the sediment area had been removed but the dredging was stopped since phosphorus continued to be released into the water from these areas. In 1992, a new restoration policy, a combination of further reduced external nutrient loading and food-web manipulation was initiated. A constructed wetland (30 ha) to reduce phosphorus and nitrogen was created in connection to the effluent from the sewage treatment plant. Protection zones along the feeder streams into Lake Finjasjon were also established. A cyprinid reduction programme by trawling was carried out between 1992 and 1994. When it started, the fish community was composed of 90–95% bream and roach. After two years of trawling, the ratio between piscivorous and planktivorous fish was 1:1. In 1994 and 1995, the transparency increased due to a considerably reduced biomass of phytoplankton and a radically altered phytoplankton community. The monoculture of Microcystis was replaced by a diverse phytoplankton community. The increased transparency made possible the development of submerged macrophytes such as Elodea, Myriophyllum and Potamogeton. The internal loading of phosphorus decreased dramatically in 1994 and 1995, possibly as a result of reduced sedimentation of phytoplankton.

Seasonal variation of phytoplankton community in Thale Sap Songkhla, a lagoonal lake in southern Thailand

The phytoplankton in Thale Sap Songkhla was investigated at 2–3 month intervals from August 1991 to October 1993. The abundance of phytoplankton ranged from 1.4×106 to 1.3×109 cells m−3. A total of 6 divisions with 103 genera were identified as Bacillariophyta: 49 genera, Chlorophyta: 21 genera, Pyrrhophyta: 15 genera, Cyanophyta: 12 genera, Chrysophyta: 3 genera and Euglenophyta: 3 genera. Although phytoplankton abundance was distinctly greater in the first year of study (August 1991–June 1992) than in the second year (August 1992–October 1993), their patterns are similar: 2 peaks yearly. The peaks of phytoplankton occurred in the heavy rainy season (northeast monsoon) and the light rainy season (southwest monsoon). The main bloom was found during December–January, with a predominance of blue-green algae (e.g. Aphanizomenon andPhormidium) and green algae (e.g. Eudorina). Their species composition also increased, an effect of the large amount of rainfall resulting in low salinity during the northeast monsoon. The minor bloom was produced by diatoms during June–July when water salinity was moderate to seawater. Both phytoplankton numbers and species composition were high. However, unpredictably heavy rainfall during the southwest monsoon period may reduce diatom production due to rapid immediate replacement by blue-green species. Besides salinity concentration, a low total nitrogen: total phosphorus (TN: TP) ratio tended to support the growth of blue-green algae. The diversity of phytoplankton was lowest in the heavy rainy period.

Long term study on the influence of eutrophication, restoration and biomanipulation on the structure and development of phytoplankton communities in Feldberger Haussee (Baltic Lake District, Germany)

Feldberger Haussee provides a classic example of eutrophication history of hardwater lakes in the Baltic Lake District (Germany) and of changes in their algal flora during the 20th century. The lake originally was regarded as slightly eutrophic. A process of drastic eutrophication from the 1950s until the end of the 1970s caused mass developments of blue-green and green algae. A restoration program was started in the 1980s to improve the water quality of the lake using both diversion of sewage outside the catchment area, and biomanipulation by altering the fish community. This restoration program led to positive changes in the lake ecosystem. Direct effects of biomanipulation resulted in an increase of herbivorous zooplankton, a decrease of phytoplankton biomass, and an increase of water transparency. The recovery of Feldberger Haussee also may have been indirectly enhanced by an increase in nutrient sedimentation as a consequence of intensified calcite precipitation, decrease in phosphorus remobilization due to a pH-decrease, increased NIP-ratio, and recolonization of the littoral zone by macrophytes. This paper concentrates on the long term development of the phytoplankton community as a response to changes in the food web structure as well as to alterations in the chemical environment of the algae. Both are reflected in four major stages passed by the algal assemblage between 1980 and 1994: (1) From 1980-summer 1985 dense green algal populations were found indicating similar conditions as in the 1970s during the period of maximum eutrophication. (2) A diverse phytoplankton community during summer 1985–1989 showed the first effects of a recovery. (3) From 1990–1992 the phytoplankton was characterized by ungrazeable filamentous blue-green algae first of all as a response to increased herbivory of zooplankton on edible species and to increasing N/P-ratios. (4) Finally, the algal species diversity increased in 1993 and 1994 whereas the phytoplankton biomass decreased showing the success of the combined restoration measures.

Interannual phytoplankton dynamics of a hypertrophic African lake

Phytoplankton species composition and abundance were recorded weekly or biweekly for nearly 7 years in a hypertrophic lake (Hartbeespoort Dam, South Africa), together with a range of physical and chemical parameters. A total of 73 species were recorded, of which only 20 were occasionally abundant, and only 5 became dominant (>50% of total biomass) at least once (Microcystis aeruginosa, Oocystis lacustris, Aulacoseira (= Melosira) granulata, Cyclotella meneghiniana, Carteria cordiformis). The earlier years of the study (1982-1986) were drought years characterized by low water levels (10-15 m below the level at full supply), excess supply of nutrients at all times of the year, and overwhelming dominance of Microcystis aeruginosa. This K-selected species proved to be well adapted to withstand the range of environmental conditions throughout summer, fall and winter but it declined in spring each year when a fast successional episode followed. Several small-celled chlorophytes, diatoms and cryptophytes appeared and disappeared until Oocystis lacustris became dominant for a few weeks, to be replaced by M. aeruginosa early in the summer. During the following rainy years (late 1986 to 1988), the lake re-filled. Major washout losses, concomitant with a considerable decline in surface water phosphorus concentrations and elevated TN/TP ratios, apparently led to the reduction in the abundance of M. aeruginosa. Its bloom extended over a smaller portion of the year in 1986 and 1987, and disappeared in May 1988, permitting the development of a more diverse phytoplankton community subject to control by zooplankton grazing. This long-term phytoplankton record from Hartbeespoort Dam demonstrates the key role of a dominant species in controlling community composition and diversity in hypertrophic lakes. Stable environments lead to low-diversity and high-biomass phytoplankton assemblages dominated by K-strategists, while disruptions of suitable strength and frequency allow for the development and maintenance of higher species diversity.

Wide-spread occurrence and clonal variation in viruses which cause lysis of a cosmopolitan, eukaryotic marine phytoplankter Micromonas pusilla

Seven clonal isolates of viruses which cause lysis of the eukaryotic, naked, photosynthetic flagellate Micrornonas pusilla (Prasinophyceae) were isolated from the coastal waters of New York, Texas, California and British Columbia, as well as the oligotrophic waters of the central Gulf of Mexico. The viruses are large polyhedrons (ca 115 nm dia.) lacking tails, and are morphologically similar to a previously described virus (MPV) which lnfected M. pusilla. Restriction fragment analysis of the DNA from these clones using EcoRI revealed unique banding patterns, demonstrating that each of the clones (including 3 that were isolated from the same water sample) were genetically different. Summation of the 17 to 26 visible fragments from the restriction digests, for each of the clones, yielded estimated genome sizes of 77 to 110 kilobase pairs. In contrast. only 4 different types of viruses could be recognized based on the molecular weights of the major proteins. In field samples the concentrations of vlruses causing lysis of M. pus~lla were found to be spatially and temporally variable, ranging from < 20 to 4.6 x 106 infective units I' Our results demonstrate that thls genetically diverse but morphologically similar group of viruses is widespread in nature. As viral infections propagate rapidly when host density is high, the presence of these viruses may place constraints on the maximum density that M. pusilla could reach in nature. I f viruses infecting other phytoplankton taxa are similarly w~despread then they are probably a major factor maintaining diversity in phytoplankton communities, and are also likely important players in nutrient and energy cycling.

A phytoplankton bloom and associated processes observed with a long-term moored system in antarctic waters

A moored system was designed for monitoring both longand short-term temporal variations in phytoplankton communities. It consisted of a chlorophyll buoy, a current meter and a sequential, multiple-sampling sedment trap, set at depths of 52. 57 and 120 m. respectively. The system was deployed at 7Oo11.54'S, 2418.68'E in Breid Bay, Antarctica, from 28 December 1985 to 13 February 1986. A total of 1127 hourly data sets and 12 trap samples were obtained. Equivalent chlorophyll a concentration fluctuated mainly in the range 0.69 to 5.60 yg 1-l; values tended to decrease toward early February. Tides caused the depth of the buoy to vary between 51 0 and 52.9 m. A strong positive correlation was found between chlorophyll a level and water temperature and indicates a possible advective water movement in the Bay. Vertical flux of particulate pigments showed a marked increase in mid-January, 3.5 to 10.5 d after an increase was observed In surface chlorophyll. Sediment samples were dominated by intact cells of Thalassiosira antarctica throughout the period of observation.

Effective Solvents and Extraction Periods Employed in Phytoplankton Carotenoid and Chlorophyll Determinations

Using high-performance liquid chromatography (HPLC), we showed that spectrophotometric determinations of algal lipophilic pigments are often biased by the choice of extraction solvent. Several commonly used extraction solvents and extraction periods were tested on diverse phytoplankton species isolated from the Neuse River, NC. Extraction solvents included 100% acetone, 90% acetone – 10% distilled deionized water (DDW), 50% acetone – 50% methanol, and 90% methanol – 10% DDW. Extraction efficiencies varied significantly among genera. For the diatom Cyclotella meneghiniana, at least three solvents extracted all lipophilic pigments with equal efficiency, but 50:50 acetone–methanol was clearly superior for the chlorophycean Chlorella vulgaris. A host of differences in extraction efficiencies and extraction times were observed when we compared eukaryotic with prokaryotic (blue-green algae) phytoplankton. We were unable to find a single extraction technique that could consistently provide quantitative and uniform pigment yields from diverse phytoplankton communities. Nevertheless, HPLC techniques can be rapidly and routinely employed to determine appropriate extraction protocols for lipophilic pigments of interest in specific aquatic ecosystems.

Ecological studies of phytoplankton in the Waikato River and its catchment

Most of the main streams and lakes of the Waikato catchment were surveyed for phytoplankton in April 1974 and February 1975; 69 genera (118 species) of phytoplankton were identified. Phytoplankton density increased going downstream along the Waikato River and the diversity of phytoplankton communities increased with distance from the river mouth. An explosive increase in algal density in the centre of Lake Ohakuri was found in both surveys. The increase was believed to be associated with an increase of nutrients and a shift from river to lake environment in this part of the river system. Diatoms dominated the Waikato River and most of its tributaries. Blue‐green algae formed blooms in the lowland lakes. Green algae were common, but were never dominant in any locality. The seasonal succession of some major species in the lower Waikato River (i.e., at Ngaruawahia, Rangiriri, and Tuakau) was determined from September 1973 to August 1974. Most species were most abundant in summer. Phytoplankton density was positively correlated with temperature and negatively with nitrate concentration. Flow rate may exert an overall control on phytoplankton growth in the Waikato River.

Microplankton diversity indices as indicators of eutrophication in the northern adriatic sea

Phytoplankton community diversity indices are used to characterize the effects of eutrophication in the Northern Adriatic Sea. A derived Shannon diversity frequency spectrum provided a single biological quantification which allowed an interpretation of temporal and regional differences and which can also be used to evaluate future changes in species diversity. The data base comprised a 4+ year time series involving 300 taxa.

Species Diversity in Lacustrine Phytoplankton. I. The Components of the Index of Diversity from Shannon's Formula

Seasonal observations on the diversity of phytoplankton communities were made in three lakes in Wisconsin. Extremes in nutrient availability and morphometry in the lakes yielded a range in diversity indexes calculated from Shannon's formula. Examination of the relative importance of the two components in the index indicated that the variability of the index can in large part be attributed to the component of equitability as expressed in the 10 to 15 most abundant species. It appears that with additional species, the positive effect of the component of species richness is countered by the negative effect of the equitability component. Species of low abundance appear to have a minor effect on the index of diversity. The response of the components is discussed in terms of interactions, relationships, and problems associated with estimating the diversity of indefinitely large communities.