Diel changes of uptake of inorganic carbon and nitrogen by phytoplankton, and the relationship between inorganic carbon and nitrogen uptake in Lake Nakanuma, Japan

Diel changes of uptake of inorganic carbon and nitrogen wereexamined in a small freshwater lake, Lake Nakanuma, Japan, bythe ¹³C and ¹⁵N method. Experiments were earned out in spring,summer and autumn in 1984. Carbon and nitrogen uptake in thelight incubation showed maxima around noon at the three seasons.Carbon uptake ceased at night, but ammonium uptake was fairlylarge at night. In the dark incubation carbon uptake did notoccur. Ammonium uptake showed a maximum at dusk in the darkexperiments. Diel changes of nitrate uptake were less clearthan those of ammonium uptake. These results indicate that nitrogenuptake partly depended on the carbon uptake. Then, we triedto explain the diel changes of nitrogen uptake, assuming thatthe nitrogen uptake partly depends on stored carbohydrate. Thediel changes may be elucidated by the sum of three terms: oneis the term of decay of stored carbohydrate, the second is theterm which indicates cumulative increase of stored carbohydrateand the third is the term which directly depends on light.     

Seasonal and long term changes of the phytoplankton in the lake Tortum in relation to environmental factors, Erzurum, Turkey

Seasonal changes in phytoplankton community structure of the lake Tortum were studied over one year period, from March 2002 to February 2003. The collected data were compared with the data collected 21 years ago. Chlamydomonas microsphaerella, Cyclotella krammeri, C. glomerata, and Ceratium hirundinella were identified to be dominant several times during the study period. Species diversity and biomass of the phytoplankton were very low in spite of sufficient and high levels of nutrient concentrations. Maximum phytoplankton density levels were observed during summer and late autumn. Phytoplankton density was positively correlated with nutrients, temperature and pH, and it was negatively correlated with Secchi depth and dissolved oxygen. Phytoplankton growths were negatively affected from water transparency and high levels of water mass transport (circulation) and velocity in the lake.     

The phytoplankton of Lake Liddell,New South Wales: chlorophyll a concentrations,species seasonal succession,and covariation with nutrients

Samples of the phytoplankton in a freshwater lake, Lake Liddell, New South Wales (Lat: 32° 22 S, Long. 150° 1 E) were collected every 4 weeks between October 1987 and November 1988. Chlorophyll a concentrations ranged from 1.8 g 1^–1 to 9.1 g 1^–1 and were positively correlated with the following nutrient parameters: total and nett mass additions of nitrate/nitrite-N and total-N, total additions of Kjeldahl-N, and nett mass addition N-P ratios. There was no correlation between lake nutrient concentrations and chlorophyll a. Factors other than nutrient concentrations appeared to be effecting chlorophyll a concentrations as summer levels were low despite nutrient concentrations being at a maximum. In spring and summer the phytoplankton was dominated by chlorophytes, with dinoflagellates and diatoms most abundant in autumn. During winter cyanobacteria were the most abundant. The relative abundance of chlorophytes was positively correlated with in lake nitrate/nitrite-N concentrations whereas the relative abundance of cyanobacteria was negatively correlated with this parameter. Based on chlorophyll a concentrations and the phytoplankton flora Lake Liddell can be classified as mesotrophic.     

In situ measurements of uptake of inorganic carbon and nitrogen by the aquatic liverworts Jungermannia vulcanicola Steph. and Scapania undulata (L.) Dum. in an acid stream,Kashiranashigawa, Japan

In situ uptake of inorganic carbon and nitrogen by the aquatic liverworts Jungermannia vulcanicola Steph. and Scapania undulata (L.) Dum. was measured in an acid stream, Kashiranashigawa, Japan. The uptake activities were similar in the both species. The activities were highest at the tip of shoots, and decreased gradually towards the base. Carbon uptake at the tip in the light was 10.4 × 10^–4 for J. vulcanicola and 8.1 × 10^–4 g C g dry wt^–1 h^–1 1 for S. undulata. Ammonium was effectively incorporated into the shoots, and the uptake activity at the tip was between 1.9 × 10^–5 and 5.8 × 10^–5 g N g dry wt^–1 h^–1. Nitrate uptake was smaller than ammonium uptake. The ratio of dark to light uptake in ammonium uptake experiments was larger than that in carbon uptake experiments. These results suggest that the liverworts use ammonium as a major nitrogen source, and that ammonium uptake was less dependent on light than carbon uptake.     

Long-term phytoplankton changes in a shallow hypertrophic lake,Albufera of Valencia (Spain)

A long-term phytoplankton study was carried out in the Albufera of Valencia, a shallow hypertrophic lake (surface area 21 km², mean depth 1 m, total inorganic nitrogen load 155 g m^-2 y^-1, total inorganic phosphate load 15 g m^-2 y^-1) from 1980 to 1988. The lake functions as a reservoir for the surrounding rice cultivation. From 1940's to 1988, its phytoplankton assemblage has been altered from a mesotrophic to a hypertrophic character, as consequence of the increasing pollution. For 1980–88, annual variations in the phytoplankton were less pronounced than seasonal changes. The hypertrophic and morphometric features of the lake favoured the stability of the phytoplankton assemblage and chlorophyll a levels during the study period. Seasonal and horizontal distribution of the total phytoplankton abundance and biomass were highly influenced by the hydrological cycle of the lagoon. Compared with other shallow nutrient rich lakes, the Albufera of Valencia is similar to the shallow hypertrophic lakes of the Netherlands.     

Phosphate uptake capacity of summer phytoplankton of the Loosdrecht Lakes in relation to phosphorus loading and irradiance

Summer populations of the phytoplankton of the Loosdrecht Lakes were enclosed in laboratory scale enclosures (LSE), supplied with 7.5 g P.l^–1.d^–1 and 105 g P.l^–1.d^–1, respectively. The maximum initial phosphate uptake rate (V_m) was related to irradiance and primary production. At phosphate uptake saturating light-irradiance V_m values up to 4 times the V_m values in the dark were measured.The phosphate uptake capacity per unit dry weight remained more or less constant throughout the experiments in the LSE receiving the lower amount of phosphorus, and declined in the LSE receiving the higher amount of phosphorus. Within the range of V_m values measured (<10 g P.mg DW^–1.h^–1 or 1,3 g P. g chla ^–1.h^–1), the growth rate of the phytoplankton was not influenced by alterations in phosphorus availability.     

Inorganic carbon uptake by phytoplankton in Vineyard Sound,Massachusetts. II. Comparative primary productivity and nutritional status of winter and summer assemblages

Using time-course, natural-light incubations, we assessed the rate of carbon uptake at a range of light intensities, the effect of supplemental additions of nitrogen (as NH₄⁺ or urea) on light and dark carbon uptake, and the rates of uptake of NH₄⁺ and urea by phytoplankton from Vineyard Sound, Massachusetts from February through August 1982. During the winter, photoinhibition was severe, becoming manifested shortly after the start of an incubation, whereas during the summer, there was little to no evidence of photoinhibition during the first several hours after the start of an incubation. At light levels which were neither photoinhibiting nor light limiting, rates of carbon uptake normalized per liter were high and approximately equal during winter and summer (22–23 μg C·l^?1 · h^?1), and low during spring (<10 μgC·l^?1· h^?1). In contrast, on a chlorophyll a basis, rates of carbon fixation were as high during spring (15–20μg C·μg Chl a^?1·h^?1), when concentrations of chlorophyll a were at the yearly minimum (<0.5 μg · l^?1) as during the summer, when chlorophyll a concentrations were substantially higher (0.8–1.3 μg · l^?1). Highest rates of NH₄⁺ and urea uptake were observed during summer, and at no time of the year was there evidence for severe nitrogen deficiency, although moderate nitrogen nutritional stress was apparent during the summer months.     

Vertical structure and photosynthetic activity of Lake Shira phytoplankton

This study was conducted to analyse vertical dynamics of phytoplankton distribution in Shira Lake during the summer stratification regime. From late June to September phytoplankton in Shira Lake were stratified with the maximum in the lower part of the thermocline, at a depth of 8–12 m, with a chlorophyll concentration up to 23 g and biomass up to 5 mg l^–1. Maxima of chlorophyll and biomass of cyanobacteria and green algae were in different layers. From June to September a major part of chlorophyll a was in green algae, while under ice – in cyanobacteria. The variable fluorescence proves high photosynthetic activity of algae in the depth assemblage. Epifluorescent analysis disclosed that additional light-harvesting pigments were better developed in cells from the depth maximum. The maximum of gross primary production calculated from fluorescence corresponded to the depth maximum of phytoplankton. Primary production over a season was 2.7 gO₂ m^–2. Formation mechanisms of the depth maximum of phytoplankton are discussed in this paper.     

Effects of nutrient addition on phytoplankton in Lake Nakanuma,Japan I. Changes in biochemical components

Effects of nutrient conditions on biochemical components (sugars and amino acids) of phytoplankton were examined in Lake Nakanuma in Japan. Phosphate, ammonium and silicate were added to water samples collected at 0 m, which were incubated for 15 days in situ. Chlorophyll a in phosphate-added samples increased much more than that in other samples. Total amino acids and total neutral sugars in phosphate-added samples also increased more than those in other samples. The increase of total amino acids and chlorophyll began faster than that of total neutral sugars during the first 5 days of incubation. Total neutral sugars in the phosphate-added samples increased rapidly after 8 days. The composition of amino acids did not change so much. However, the composition of neutral sugars changed according to the different nutrient addition. Phosphate-added samples changed greatly during the incubation. These changes were explained at least partly by changes in nutrient conditions. Addition of limiting nutrients decreased glucose content, whereas depletion of nutrients increased the content. This study indicates that measurements of the biochemical components contribute to the analysis of effects of nutrients on phytoplankton in natural waters.     

Ecological studies of phytoplankton in Tai Tam Bay,Hong Kong

Of the 141 phytoplankton species found during the sampling period, the Bacillariophyceae was the most important group and included 70% of the total number of species; the Dinophyceae comprised a smaller percentage (28%) of the taxa; and only 3 chrysophyte species occurred throughout the study period. In terms of numbers of individuals, the Bacillariophyceae remained as the dominant group and contained 97% of the total numbers whereas the Dinophyceae represented only 3% of the total phytoplankton population.The most dominant diatom species was Thalassiosira allenii Takano which constituted 35% of the Bacillariophyceae group whereas the most abundant dinoflagellate was Prorocentrum gracile Schutt which represented 40% of the total Dinophyceae numbers.Chlorophyll a levels varied from 0.40 to 32.31 mg m^–3 at the surface and from 0.33 to 33.91 mg m^–3 at the bottom.Seasonal trends of phytoplankton abundance and chlorophyll a concentration were observed in the survey area with generally high peaks in summer and low values during winter months. Such variations can be attributed to the interactions between, and changes of, various environmental parameters, such as temperature, salinity and nutrient availability (particularly silicate).     

Seasonal changes in neutral sugars and amino acids of particulate matter in Lake Nakanuma,Japan

Amino acids and neutral sugars in particulate matter were measured weekly from April in 1987 to March in 1988 in Lake Nakanuma, Japan. Changes in concentrations of total amino acids and total neutral sugars corresponded to those of chlorophylla. The composition of amino acids varied little seasonally and vertically. On the contrary, the composition of neutral sugars changed seasonally and vertically. We discuss the relationship between the changes in the biochemical components and environmental factors.     

Zooplankton induced decrease in inorganic phosphorus uptake by plankton in an oligotrophic lake

Experiments conducted on samples collected from a large oligotrophic lake revealed the following: (1) excretion rates of PO _inf4 ^sup3– by single Daphnia thorata were below detection (5 pmol animal^–1 min^–1) in 20 ml of oligotrophic lake water over a period of 10 min, (2) experimental addition of D. thorata to 20 ml aliquots of lake water decreased community-wide microbial uptake of PO _inf4 ^sup3– on two occasions (as measured by ³²PO _inf4 ^sup3– incorporation), and (3) the presence of D. thorata increased uptake by organisms smaller than 1µm, and decreased uptake by large phytoplankton. The specific mechanism for these responses remains unclear, but the results imply that when phytoplankton larger than 1µm encounter cm scale patches of water recently occupied by Daphnia they may experience decreased PO _inf4 ^sup3– availability rather than elevated concentrations of PO _inf4 ^sup3– caused by excretion. We show that ³²P uptake experiments using natural plankton assemblages can be influenced by the presence or absence of large zooplankton, and that neither grazing, turbulence, nor PO _inf4 ^sup3– excretion can account for this influence.     

The effect of environmental parameters and cyanobacterial blooms on phytoplankton dynamics of a Portuguese temperate Lake

The increasing occurrence of cyanobacterial blooms in freshwaters is of great concern due to the ability of many cyanobacteria to produce cyanotoxins. In the present work, the eutrophied Vela Lake (Central Portugal), used for recreational purposes and as a water source for agriculture, was monitored every fortnight between 2000 and 2001. Phytoplankton diversity and densities were measured and correlated to environmental parameters. A seasonal phytoplanktonic succession was observed and it was mainly correlated with conductivity, temperature, total suspended solids and nutrients availability (particularly phosphorus). Diatoms were dominant during winter months (inferior temperatures and higher nutrients availability) followed by green algae in early spring and then cyanobacteria from late spring until early autumn (less nutrient availability and higher temperatures). A massive cyanobacterial bloom of Aphanizomenon flos-aquae occurred early in May 2001 and was preceded by the lowest nitrogen levels measured in the water during all the study period. At the time of this bloom senescence, dissolved oxygen was severely depleted and a massive death of ichthyofauna was recorded. A Microcystis aeruginosa bloom was also detected in July 2001 and it occurred following a rapid decrease in abundance of green algae and diatoms. By considering not only the environmental parameters but also the occurrence of cyanobacterial blooms as explanatory variables in a canonical correspondence analysis, the variance explained for the phytoplanktonic assemblage during the study period was increased in about 7% achieving a total of 61.0%, indicating a correlation that may be due to the known competitive advantage and/or allelopathy of the bloom-forming cyanobacteria towards microalgae.     

Detecting presence of phytoplankton groups with non-specific pigment signatures

The use of pigment ratios and sizefractionation was investigated fordetecting the presence of phytoplanktongroups with non-specific pigmentsignatures. These groups includeprymnesiophytes, chlorophytes,prasinophytes and cyanobacteria. Prasinophytes without the diagnosticpigment prasinoxanthin could be identifiedby calculating ratios ofprasinoxanthin/chlorophyll b andlutein/chlorophyll b on data setsfrom two Danish estuaries. Furthermore,these pigment ratios could be used toexclude the presence of chlorophytes, andratios of zeaxanthin/chlorophyll brevealed that cyanobacteria wereoccasionally present. This information isimportant when selecting whichphytoplankton groups to load in the CHEMTAXprogram for calculating the chlorophylla biomass of the individualphytoplankton groups. Subtypes ofprymnesiophytes were detected by sizefractionations on samples from a mesocosmexperiment. The size fractionations,although time-consuming and not alwaysfeasible, and the pigment ratiocalculations proved to be able to providethe desired information as to whichphytoplankton groups to load in the CHEMTAXprogram.     

Daily changes in nitrate uptake and metabolism in Capsicum annuum

The diurnal pattern of nitrate uptake by Capsicum annuum L. cv. California Wonder in a constant environment is described by a Fourier harmonic, with the maximum uptake in the middle of the photoperiod and the minimum in the middle of the dark period. Comparison of the uptake pattern with that of nitrate reductase (EC 1.6.6.1.) activity suggests against a direct control of one process by the other. This was confirmed by the observation that the pattern of nitrate reductase activity was not altered by restricting nitrate uptake to one hour per day. Translocation of ¹⁵N from the roots is much greater in the lightperiod than in the dark period. Reduction of ¹⁵N in the leaves occurs in the lightperiod but very little is reduced in the dark period. Amino acid levels showed marked daily fluctuations but in the roots neither amino acids, sucrose, fructose, glucose nor malate showed fluctuations. The amino acid composition of roots and leaves differed: glutamine+glutamate were relatively more important in leaves than in roots whereas alanine was a more important constituent of roots than of leaves.Abbreviation NR nitrate reductase     

Cyanobacterial blooms and water quality in Greek waterbodies

The cyanobacterial species composition of nine Greek waterbodies of different type and trophic status was examined during the warm period of the year (May–October). Cyanobacterial water blooms were observed in all waterbodies. Forty-six cyanobacterial taxa were identified, 11 of which are known to be toxic. Eighteen species are reported for the first time in these waterbodies, 8 of which are known to produce toxins. Toxin producing species were found in all of the waterbodies and were primarily dominant in bloom formations (e.g., Microcystis aeruginosa, Anabaena flos-aquae, Aphanizomenon flos-aquae and Cylindrospermopsis raciborskii). Cosmopolitan species (e.g., M. aeruginosa), pantropic (e.g., Anabaenopsis tanganyikae) and holarctic species (e.g., Anabaena flos-aquae) were encountered. Shallow, eutrophic waterbodies had blooms dominated by Microcystis species and were characterized by phytoplankton association M. Anabaena and Aphanizomenon species of association H were dominant in waterbodies with low dissolved inorganic nitrogen and thermal stratification in the summer. Total cyanobacterial biovolumes (CBV) ranged from 7 to 9,507 cm³ m⁻³ and were higher than Alert Level 2 and Guidance Level 2 (10 cm³ m⁻³; World Health Organization; WHO) in seven of the waterbodies. Chlorophyll a concentrations ranged from 6 to 90,000 mg m⁻³ and were higher than Alert Level 2 and Guidance Level 2 (50 mg m⁻³; WHO) in eight of the waterbodies. There is also an elevated risk of acute toxicosis (Guidance Level 3; WHO) in five waterbodies. Water of an undesirable quality, hazardous to humans and animals occurs in several Greek waterbodies.     

A comparison of three methods of measuring phytoplankton biomass on a daily and seasonal basis

Three methods of measuring phytoplankton biomass (microscopic counting, electronic particle counting and determination of chlorophyll a concentration) were compared on both a daily (4 days) and a seasonal basis, in Charnwood Water, a small English freshwater lake. Correlations among measures were generally poor within days. However, good correlations were achieved among all methods on a seasonal basis. Seasonal correlations, in particular those between total particle numbers from particle counting and algal numbers from microscope, were affected by the degree of stability of the water column, with different relationships being found for mixed periods compared to stratified periods. These differences were related to an increased amount of particulate matter affecting the total particle numbers estimate during mixed periods. Other workers have found better relationships among these phytoplankton biomass methods within short periods, but there appears to be considerable variability among lakes. Therefore, it is recommended that the most appropriate method be evaluated on a individual lake basis, depending on the aims of the study.     

Characterization of the affinity for nitrogen, uptake kinetics, and environmental relationships for Prorocentrum minimum in natural blooms and laboratory cultures

During the late spring and early summer of 1998, an extensive bloom of the dinoflagellate Prorocentrum minimum (>93% of phytoplankton cell density) developed in several tributaries of the Chesapeake Bay, USA. In January 1999, a bloom of mixed dinoflagellates (Heterocapsa rotundata, H. triquetra and P. minimum, with P. minimum forming 21% of total phytoplankton cells and 39% of the total biovolume) developed in the mesohaline Neuse Estuary, North Carolina, USA. During these blooms, experiments were carried out to characterize the nitrogen uptake kinetics of these assemblages with ¹⁵N isotopic techniques. Four nitrogenous substrates (NO₃⁻, NH₄⁺, urea, and a mixed amino acids substrate) were used to determine uptake rate and substrate preference. Rates of nitrogen uptake were also measured in P. minimum cultures grown on varying growth nitrogen substrates. The calculated kinetic parameters determined for the P. minimum-dominated field assemblages and the cultures indicated a preference for NH₄⁺. NH₄⁺ was also the primary nitrogen source supporting the blooms. In addition, a high affinity for urea was also found, and urea contributed significantly to the Neuse Estuary bloom. Furthermore, results showed that the regulation of uptake for each of the substrates was different: strong positive relationships between affinity and temperature were found for NH₄⁺ and amino acids, while a negative response was found for NO₃⁻, and very little response to temperature was noted for urea. These differences suggest that a diversity of nitrogen uptake mechanisms may aid the development and maintenance of P. minimum blooms.     

Temporal dynamics and spatial variation of algae in relation to hydrology and sediment characteristics in the Okefenokee Swamp,Georgia

In a 20-month study, phytoplankton and periphyton chl a, and dry mass of macroscopic algal aggregates in four marshes and a lake within the Okefenokee Swamp (Georgia, USA) were comparable to other wetlands and lake littoral areas. Chlorophyll levels in two marshes were inversely related to water level and phytoplankton at three marshes developed unimodal maxima following macrophyte dieback. Standing stocks in a vernally inundated marsh were greater than a nearby marsh which was permanently inundated; chlorophyll levels displayed longer blooms in the inundated marsh during periods of low rainfall or after drought. Field dynamics, sediment sorption characteristics and algal bioassays suggest that evaporative drawdown stimulates algae by release of nutrients from exposed peat, while high water levels reduce nutrient release from sediments and disperse phytoplankton through flushing. Equilibrium phosphate concentrations of sediments and algal levels were higher at an abandoned rookery than a nearby non-rookery area, indicating nutrient enrichment from residual guano deposits.     

Relationship between bacterioplankton and phytoplankton community dynamics during late spring and early summer in Lake Taihu, China

The relationship between bacterioplankton and phytoplankton community compositions was investigated from April to June, 2005 with samples taken at five different stations in Lake Taihu, China. Bacterioplankton and phytoplankton community compositions as determined by denaturing gradient gel electrophoresis of polymerase chain reaction amplified bacterial 16S rRNA gene fragments (PCR-DGGE) and microscopic examination, respectively, revealed a high degree of diversity. In total, 43 unique bands were identified amongst the DGGE profiles, and 29 dominant phytoplankton populations were observed. The DGGE profiles were clustered into two distinct groups. These two clusters were closely associated with two dominant phytoplanktons, Ulothrix sp. and Microcystis spp., as observed on April 19, May 27 and June 27, 2005, respectively. The relationship between bacterioplankton and phytoplankton community compositions was investigated using Canonical Correspondence Analysis (CCA) with the Shannon-Wiener diversity index of phytoplankton community (Hp), the total cell abundance of phytoplankton (N) and the relative abundance of Microcystis spp. (M) as the variables. The CCA results indicated a 30.9 % correlation coefficient, suggesting a high degree of correlation between bacterioplankton and phytoplankton community compositions.