Structure and seasonal trophodynamics of picophytoplankton in sevastopol bay and adjacent waters (the Black Sea)

Abundance and seasonal trophodynamics (specific growth rate, daily production, and grazing mortality) of the major picophytoplankton components, Synechococcus cyanobacteria (Syn) and picoeukaryotes (Pico-E), were studied at three stations in Sevastopol Bay and adjacent coastal waters (the Black Sea) in 2014 by flow cytometry and the dilution method. Pico-E abundance was shown to increase along the nutrient and pollution gradient from the coastal waters outside the bay (annual average of 7.3 ± 5.4 × 10³ cells mL^–1) to the eastern corner of the bay (28.7 ± 11.4 × 10³ cells mL^–1), while no relation was found between the water pollution status and Syn abundance (9.9 ± 8.7 × 10³ cells mL^–1; at all the stations, n = 27). Matter flows through the communities (daily production for Syn and Pico-E 0^–16.6 and 0^–19.3 µg C L^–1 day^–1, respectively; grazing mortality for Syn and PicoE 0–3.6 and 0–21.2 µg C L^–1 day^–1, respectively) were comparable to or even exceeded their biomass stocks (>0.05–6.8 and 0.9–26.5 µg C L^–1 for Syn and PicoE, respectively), indicating high biomass turnover rates. The highest flow-to-stock ratio (up to 6 for Syn) and a significant imbalance between daily production (P) and grazing mortality (G) were observed in the most polluted and eutrophic waters of the bay in spring (Pico-E: P/G < 1) and late summer (Syn: P/G > 1). Black River inflow to the bay was hypothesized to be among the mechanisms maintaining this pronounced and long-term imbalance in the open system without any negative consequences for the picophytoplankton assemblages.     

胶州湾叶绿素a浓度及浮游植物的粒级组成

2008年2、5、8和11月对胶州湾及邻近水域中表层叶绿素a浓度和浮游植物粒级组成进行了调查.结果表明:胶州湾内和湾外表层叶绿素a年平均浓度分别为4.90和2.03 mg·m^-3;叶绿素a浓度的平面分布呈现自东北部及近岸向中部、南部及湾外递减的趋势;叶绿素a浓度季节变化明显,冬季和夏季浓度较高,春季次之,呈现温带海域双峰型的变化趋势.胶州湾浮游植物粒级组成以微型浮游植物为主,平均占叶绿素a总量的60.9%,其次是小型浮游植物,超微型浮游植物所占比例最低,与我国近海浮游植物粒级组成基本一致.与历史资料相比,微型浮游植物所占比例有所增加,超微型浮游植物所占比例降低.     

Fast microzooplankton grazing on fast-growing,low-biomass phytoplankton: a case study in spring in Chesapeake Bay,Delaware Inland Bays and Delaware Bay

Dilution experiments were performed to examine the growth and grazing mortality rates of picophytoplankton (<2 μm), nanophytoplankton (2–20 μm), and microphytoplankton (>20 μm) at stations in the Chesapeake Bay (CB), the Delaware Inland Bays (DIB) and the Delaware Bay (DB), in early spring 2005. At station CB microphytoplankton, including chain-forming diatoms were dominant, and the microzooplankton assemblage was mainly composed of the tintinnid Tintinnopsis beroidea. At station DIB, the dominant species were microphytoplanktonic dinoflagellates, while the microzooplankton community was mainly composed of copepod nauplii and the oligotrich ciliate Strombidium sp. At station DB, nanophytoplankton were dominant components, and Strombidium and Tintinnopsis beroidea were the co-dominant microzooplankton. The growth rate and grazing mortality rate were 0.13–3.43 and 0.09–1.92 d⁻¹ for the different size fractionated phytoplankton. The microzooplankton ingested 73, 171, and 49% of standing stocks, and 95, 70, and 48% of potential primary productivity for total phytoplankton at station CB, DIB, and DB respectively. The carbon flux for total phytoplankton consumed by microzooplankton was 1224.11, 100.76, and 85.85 μg C l⁻¹ d⁻¹ at station CB, DIB, and DB, respectively. According to the grazing mortality rate, carbon consumption rate and carbon flux turn over rates, microzooplankton in study area mostly preferred to graze on picophytoplankton, which was faster growing but was lowest biomass component of the phytoplankton. The faster grazing on Fast-Growing-Low-Biomass (FGLB) phenomenon in coastal regions is explained as a resource partitioning strategy. This quite likely argues that although microzooplankton grazes strongly on phytoplankton in these regions, these microzooplankton grazers are passive. Handling editor: K. Martens     

Spatial variations of size-fractionated Chlorophyll, Cyanobacteria and Heterotrophic bacteria in the Central and Western Pacific

Geographic and vertical variations of size-fractionated (0.2–1μm, 1–10 μm, and >10 μm) Chlorophyll a (Chl.a) concentration, cyanobacteria abundance and heterotrophic bacteria abundance were investigated at 13 stations from 4^°S, 160^°W to 30^°N, 140^°E in November 1993. The results indicated a geographic distribution pattern of these parameters with instances of high values occurring in the equatorial region and offshore areas, and with instance of low values occurring in the oligotrophic regions where nutrients were almost undetectable. Cyanobacteria showed the highest geographic variation(ranging from 27×10³ to 16,582×10³cell l^-1), followed by Chl.a (ranging from 0.048 to 0.178μg l^-1), and heterotrophic bacteria (ranging from2.84×10³ to 6.50 ×10⁵ cell l^-1). Positive correlations were observed between nutrients and Chl.a abundance. Correspondences of cyanobacteria and heterotrophic bacteria abundances to nutrients were less significant than that of Chl.a. The total Chl.a was accounted for 1.0–30.9%, 35.9–53.7%, and 28.1–57.3% by the >10μm, 1–10 μm and 0.2–1 μm fractions respectively. Correlation between size-fractionated Chl.a and nutrients suggest that the larger the cell size, the more nutrient-dependent growth and production of the organism. The ratio of pheophytin to chlorophyll implys that more than half of the >10 μm and about one third of the 1–10 μm pigment-containing particles in the oligotrophic region were non-living fragments, while most of the 1–10 μm fraction was living cells. In the depth profiles, cyanobacteria were distributed mainly in the surface layer, whereas heterotrophic bacteria were abundant from surface to below the euphotic zone. Chl.a peaked at the surface layer (0–20 m) in the equatorial area and at the nitracline (75–100 m) in the oligotrophic regions. Cyanobacteria were not the principle component of the picoplankton. The carbon biomass ratio of heterotroph to phytoplankton was greater than 1 in the eutrophic area and lower than 1 in oligotrophic waters. This revised version was published online in August 2006 with corrections to the Cover Date.     

Analysis of long-term variation in phytoplankton biovolume in the northern basin of Lake Biwa

The long-term variation in phytoplankton biovolume in the northern basin of Lake Biwa was analyzed using periodic phytoplankton census data from January 1979 to December 2009. Population densities obtained from census data were transformed into biovolumes, and phytoplankton species were categorized into three size fractions: net phytoplankton (≥4,000 μm³ cell^?1, ≥ca. 20 μm in diameter), large nanophytoplankton (100–4,000 μm³ cell^?1, ca. 6–20 μm in diameter), and small nanophytoplankton (<100 μm³ cell^?1, <ca. 6 μm in diameter). Although the annual total biovolume gradually decreased over time, the total biovolumes in winter and spring were found to increase. Furthermore, a decrease in the biovolume of net phytoplankton and an increase in that of small nanophytoplankton were observed. Because of succession in the phytoplankton community, the average cell volume of the phytoplankton community decreased from 269 μm³ cell^?1 in the 1980s to 56 μm³ cell^?1 in the 2000s. Lake warming accompanied with the intensification of thermal stratification and the augmentation of wind speed were observed at Lake Biwa over the study period. Serial analysis correcting for autocorrelation revealed that oligotrophication in the epilimnion, induced by lake warming and limitation of light available for phytoplankton growth by wind-induced water mixing, was a potential factor in the succession of the phytoplankton community.     

Picophytoplankton abundance in the Velikaya Salma strait,White Sea

In July-August 2009, the abundance of picophytoplankton (Pico) in the Velikaya Salma strait varied from 3.4 × 10⁶ to 19.4 × 10⁶ cells/L, while its biomass (B) was 0.8–3.3 mg C/m³. In August 2010, Pico abundance was significantly higher (up to 216 × 10⁶ cells/L and 36.8 mg C/m³). Pico consisted mainly of cyanobacteria. It constituted 13 (2009) to 28% (2010) of the total phytoplankton biomass. In April 2010, Pico numbers varied from 0.1 × 10⁶ to 0.22 × 10⁶ cells/L and its biomass was 0.05–0.28 mg C/m³. Picoeukaryotes were predominant. Pico constituted not more than 2.7% of the phytoplankton biomass. In the ice column, the integrated Pico abundance was 430 × 10⁶ cells/m² and the integrated biomass was 365 μg C/m².     

Abundance of picophytoplankton in the halocline of a meromictic lake, Lake Suigetsu, Japan

Numerous (0.5 to 4.8 × 10⁵ cells/ml), small phytoplankton (smaller than 0.5–1 × 1–2 μm in cell size, picophytoplankton) were distributed in the halocline (depth 2–12 m, 4–14 practical salinity units) of the saline meromictic lake, Lake Suigetsu (35°35′ N, 135°52′ E), located in the central part of the coast of Wakasa Bay along the Japan Sea in Fukui Prefecture, Japan. Vertical distribution of phytoplankton revealed that the maximum number of picophytoplankton was always observed near or a little deeper than the oxic-anoxic boundary layer (depth 5–6 m); they were dominant phytoplankton in the water layer deeper than the oxic-anoxic boundary from July to late September 2005. Spectral analysis of autofluorescence emitted from the particle fractions smaller than 5 μm measured with a spectrofluorometer and from individual cells measured with a microscope photodiode array detector revealed that the major component of picophytoplankton was phycoerythrin-rich, unicellular cyanobacteria (picocyanobacteria). Eukaryotic phytoplankton about 2.5 μm in diameter were also found, but the numbers were low. Fluorescence intensity of chlorophyll a at 685 nm (room temperature) emitted from the particle fractions smaller than 5 μm was increased by the addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. These observations indicated that at least some picophytoplankton had a functional photosystem II in the halocline where sulfide, the potential inhibitor of oxygenic photosynthesis, was always present. The large abundance together with their physiological potency suggest that picophytoplankton are one of the important primary producers in the halocline of Lake Suigetsu. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Nutrient uptake and primary productivity in an urban estuary: using rate measurements to evaluate phytoplankton response to different hydrological and nutrient conditions

The northern San Francisco Estuary (nSFE) is an urban estuary supplied with anthropogenic nutrient inputs, yet spring blooms are uncommon and phytoplankton biomass is low. The low levels of chlorophyll (<5 µg L^?1) have likely contributed to declines in several native fishes, and there is a need to evaluate the conditions that could allow for increased phytoplankton. Increased ammonium (NH₄) loads have been hypothesized to modulate the magnitude of blooms in nSFE (the “NH₄ hypothesis”) as a result of inhibition of phytoplankton NO₃ uptake that limits access to the greater nitrogen (N) pool of nitrate (NO₃). This hypothesis, tested in enclosures, but not in the field until now, is that lack of access to NO₃ limits primary production and consequently the accumulation of chlorophyll. Here, we test this in the field with the following aims: (1) to observe the uptake response of phytoplankton in different flow and N loading conditions, (2) determine whether the sequence of uptake rates suggested by the “NH₄ hypothesis” occurs and (3) obtain depth-integrated nutrient uptake rates to better constrain published criteria for bloom formation. Weekly measurements of NH₄ and NO₃ uptake, and primary production rates were made during spring 2011–2012, along with nutrient and chlorophyll concentrations during two contrasting hydrological conditions of high vs low freshwater flow. In conditions with high freshwater flow (maximum of 2405 m³ s^?1), there were lower nutrient concentrations than with low/normal flows (e.g., NO₃ of 10 µmol L^?1 compared to 30 µmol L^?1), with low N uptake and primary production rates. With low flow (maximum of 1304 m³ s^?1), there was elevated chlorophyll and blooms occurred, especially in shallow well-lit shoals where chlorophyll reached 60 µg L^?1. The higher levels of chlorophyll and primary productivity resulted from uptake of ambient NO₃ by phytoplankton, and f-ratios >0.5. This was enabled by phytoplankton uptake of NH₄ to below inhibitory levels, as proposed by the “NH₄ hypothesis.” The depth-integrated uptake rate data were used to refine a model that yields flow and nutrient concentration criteria necessary for bloom formation and confirmed that washout flows were the most useful predictor of blooms. Understanding the interaction of phytoplankton biomass with nutrient variability requires evaluating changes in C and N uptake rates and river flow. These dynamic changes are central to understanding why some urban estuaries have lower productivity than expected, and would be difficult to evaluate using biomass data alone. This study points to the importance of treating inorganic N separately as NH₄ and NO₃ rather than lumping together as DIN and to use rate process data as a mechanistic way to understand, predict and minimize cultural eutrophication impacts.     

Growth and photophysiological responses of two picoplanktonic Minutocellus species,strains RCC967 and RCC703 (Bacillariophyceae)

Reaching up to 50% of the total biomass in oligotrophic waters and armed with a set of ecological and biological properties related to their small size, picophytoplankton (<3.0?µm) are a good model to address ecophysiological questions regarding phytoplankton biodiversity. Two picoplanktonic diatoms, one isolated from an upwelling ecosystem in the Pacific Ocean (Minutocellus sp., strain RCC967), and another from oceanic waters in the Indian Ocean (Minutocellus sp., strain RCC703) were used to test hypotheses on the functional relation between ecological niche adaptation and photosynthetic regulation capacity and efficiency. Cultures were subjected to five sine light climates, each one set to peak at a different photon flux density, respectively 10, 50, 100, 250 and 500?µmol photons m^?2?s^?1. Growth rate, photosynthesis, non-photochemical fluorescence quenching, pigment composition, and particulate organic carbon and nitrogen content were followed daily for 5 days. Growth rate and physiological response curves were different in the two species, in agreement with their distinct habitats of origin. Such differences could be related to the diverse photoacclimative strategies displayed by the two species, revealing a clear adaptive divergence despite their close taxonomic relationship. Photoacclimative strategies of the two picoplanktonic diatoms are discussed in the light of functional diversity and ecosystem adaptation.     

Temporal and spatial patterns in the distribution and abundance of pico, nano and microphytoplankton in an upland lake

SUMMARY. 1. An investigation of the seasonal and depth distribution of populations of autotrophic picoplankton (0.2–2 μm), nanophytoplankton (>2<20 μm) and larger microalgal plankton (>20μm) was carried out over 2¹/₂ years, 1988–90, in Llyn Padarn, a mesotrophic upland lake in North Wales. 2. Cell numbers of picophytoplankton ranged from <10² to >10⁶ cells cm^?3. Maximum numbers of nanoplankton were c. 10⁴ cells cm^?3 and the greatest abundance of microalgal plankton, diatoms, reached 12 × 10³ cells cm^?3. 3. Three types of picoalgae were distinguished: coccoid to oval Synechococcus—Synechocystis, the rod-shaped Synchecococcus capitatus Bailey-Watts & Komárek and Chlorella minutissima Fott & Nováková, with maximum numbers of 1.2 × 10⁶, 37.8 × 10³ and 44.1 × 10³ cells cm^?3, respectively. 4. Picophytoplankton exhibited periods of exponential growth: the first in spring, and the second in August—September with an intervening population minimum in early to midsummer. Specific rates of population increase for picophytoplankton were low, with minimum apparent generation times of 3.8 days in summer 1989. 5. Nanophytoplankton included seven species of phytoflagellates and two non-motile species. These algae were present for about 10 months in each year exhibiting a fluctuation in population density of 10^2?-10³ cells cm^?3. 6. There were spring and autumn maxima in chlorophyll a concentrations in the lake water corresponding to the growth of planktonic diatoms. Maximum total biomass concentration was 35 mg m^?3 chlorophyll a, whereas pico, nano and microphytoplankton had individual maxima of 7.7, 8.4 and 31.0 mg m^?3 chlorophyll a, respectively. Picophytoplankton often contributed > 60% of the total algal chlorophyll a in the epilimnion. 7. The growth patterns and seasonal periodicities of the three size-categories of planktonic algae in Llyn Padarn were distinct. Picophytoplankton persist throughout much of the year with periods of very low abundance, < 100 cells cm^?3, occurring in winter and midsummer. Thus for much of the year, there was a large inoculum of these cells in the lake to initiate growth leading to the population maxima in spring and late summer. Nanoplankton populations, a diverse assemblage, fluctuated in numbers over the period February–November; no population decline in midsummer comparable to picophytoplankton was observed. The larger microphyloplankton exhibited classical seasonal periodicity, namely diatom growth in spring and late summer–autumn with growth of large-celled chlorophytes in the intervening summer period.     

2009年春季长江口及其邻近水域浮游植物——物种组成与粒级叶绿素a

于2009年4月在长江口及其邻近水域采集浮游植物水样,用Utermöhl方法进行初步分析,同时进行叶绿素a粒级分离研究,并采用典范对应分析讨论了浮游植物优势物种与各环境因子的关系.本次调查共鉴定浮游植物3门46属64种（不包括未定名种）,其中硅藻33属45种（不包括未定名种）,甲藻12属18种（不包括未定名种）,定鞭藻1属1种,硅藻在细胞丰度和物种丰富度上占有优势.浮游植物的生态类型主要以温带近岸种为主,优势物种为多尼骨条藻（Skeletonema dohrnii）、具槽帕拉藻（Paralia sulcata）、菱形海线藻（Thalassionema nitzschioides）、尖刺伪菱形藻（Pseudo-nitzschia pungens）、颗粒直链藻狭型变种（Melosira granulata var angustissima）、柔弱伪菱形藻（Pseudo-nitzschia delicatissima）和柔弱几内亚藻（Guinardia delicatula）,同时调查区也出现少数的半咸水种和大洋种.调查区浮游植物细胞丰度介于0.3～13447.7 cells·ml^-1,平均为1142.385 cells·ml^-1,硅藻的细胞丰度显著高于甲藻.细胞丰度高值区位于调查区的中部偏北区域,以多尼骨条藻为主.垂向上在表层出现最大值,随着深度的增加丰度降低.调查区的Shannon多样性指数和Pielou均匀度指数的平面分布基本一致,并且与细胞丰度呈镶嵌分布,即在细胞丰度高的调查区中北部较低.表层叶绿素a浓度介于0.34～29 g·L^-1,平均为3.30 g·L^-1.叶绿素a的高值区主要位于调查区的中部偏北区域,其分布趋势与浮游植物和硅藻细胞丰度的分布基本一致.主要粒级组分为小型浮游植物（microphytoplankton）,而其他靠近外海一侧的站位则以微型浮游植物（2～20 μm, nanophytoplankton）和超微型浮游植物（<2 μm, picophytoplankton）为主.与环境因子的典范对应分析（CCA）表明,春季长江口影响最优势物种多尼骨条藻分布的主要因素为硝酸盐、pH和微型浮游动物,而包括甲藻在内的其他各物种则主要受盐度、磷酸盐和硅酸盐影响.本次调查浮游植物定量研究方法与以往不同,在长江口今后需要加强骨条藻的个体生态学研究.     

Purification and characterization of a thermally stable yellow laccase from <Emphasis Type="Italic">Daedalea flavida</Emphasis> MTCC-145 with higher catalytic performance towards selective synthesis of substituted benzaldehydes

A laccase from the culture filtrate of white rot fungus Daedalea flavida MTCC-145 has been purified and characterized. The method involved concentration of the culture filtrate by ultrafiltration and an anion exchange chromatography on diethylaminoethyl (DEAE) cellulose. The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and native polyacrylamide gel electrophoresis (native PAGE) both gave single protein bands indicating that the enzyme preparation was pure. The molecular mass of the enzyme determined from SDS-PAGE analysis was 75.0 kDa. Purification fold was 21.5 while recovery of the enzyme activity was 11.52%. Using 2,6-dimethoxyphenol, diammonium salt of 2,2'-[azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid)] and 3,5-dimethoxy-4-hydroxybenzaldehyde azine as substrates, the Km, kcat, and k _cat/K _m values of the laccase were found to be 440 µM, 6.45 s^–1, 1.47 × 10⁴ M^–1 s^–1; 366 µM, 6.45 s^–1, 1.76 × 10⁴ M^–1 s^–1; and 226 µM, 6.45 s^–1, 2.85 × 10⁴ M^–1 s^–1, respectively. The pH and temperature optima were 4.5 and 50°C, respectively. The enzyme was most stable at pH 5.0 when exposed for 1 h. The purified laccase has yellow color and shows no absorption band around 610 nm characteristic of blue laccases. The enzyme transforms toluene and substituted toluenes to corresponding benzaldehyde and substituted benzaldehydes in the absence of mediator molecules with higher catalytic efficiency as compared to other known laccases.     

Uptake of inorganic and organic nutrient species during cultivation of a Chlorella isolate in anaerobically digested dairy waste

A natural assemblage of microalgae from a facultative lagoon system treating municipal wastewater was enriched for growth in the effluents of an anaerobic digester processing dairy waste. A green microalga with close resemblance to Chlorella sp. was found to be dominant after multiple cycles of sub‐culturing. Subsequently, the strain (designated as LLAI) was isolated and cultivated in 20× diluted digester effluents under various incident light intensities (255–1,100 µmoles m^?2 s^?1) to systematically assess growth and nutrient utilization. Our results showed that LLAI production increased with increasing incident light and a maximum productivity of 0.34 g L^?1 d^?1 was attained when the incident irradiance was 1,100 µmoles m^?2 s^?1. Lack of growth in the absence of light indicated that the cultures did not grow heterotrophically on the organic compounds present in the medium. However, the cultures were able to uptake organic N and P under phototrophic conditions and our calculations suggest that the carbon associated with these organic nutrients contributed significantly to the production of biomass. Overall, under high light conditions, LLAI cultures utilized half of the soluble organic nitrogen and >90% of the ammonium, orthophosphate, and dissolved organic phosphorus present in the diluted waste. Strain LLAI was also found to accumulate triacylglycerides (TAG) even before the onset of nutrient limitation and a lipid productivity of 37 mg‐TAG L^?1 d^?1 was measured in cultures incubated at an incident irradiance of 1,100 µmoles m^?2 s^?1. The results of this study suggest that microalgae isolates from natural environments are well‐suited for nutrient remediation and biomass production from wastewater containing diverse inorganic and organic nutrient species. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1336–1342, 2016     

Role of phytoplankton size distribution in lake ecosystems revealed by a comparison of whole plankton community structure between Lake Baikal and Lake Biwa

The influence of the size distribution of phytoplankton on changes in the planktonic food web structures with eutrophication was examined using natural planktonic communities in two world-famous lakes: Lake Baikal and Lake Biwa. The size distribution of phytoplankton and the ratio of heterotrophic to autotrophic biomass (H/A ratio), indicating the balance between primary production and its consumption, were investigated in the lakes of different trophic status. The results revealed that microphytoplankton (>20μm) in mesotrophic Lake Biwa, and picophytoplankton (<2μm) or nanophytoplankton (2–20μm) in oligotrophic Lake Baikal, comprised the highest proportion of the total phytoplankton biomass. The H/A ratio was lower in Lake Biwa (<1) than in Lake Baikal (>1). The low H/A ratio in Lake Biwa appeared to be the consequence of the lack of consumption of the more abundant microphytoplankton, which were inferior competitors in nutrient uptake under oligotrophic conditions but less vulnerable to grazing. As a result, unconsumed microphytoplankton accumulated in the water column, decreasing the H/A ratio in Lake Biwa. Our results showed that food web structure and energy flow in planktonic communities were greatly influenced by the size distribution of phytoplankton, in conjunction with bottom-up (nutrient uptake) and top-down (grazing) effects at the trophic level of primary producers.     

Effects of glaciers on nutrient concentrations and phytoplankton in lakes within the Northern Cascades Mountains (USA)

We compared nitrate concentrations, phytoplankton biomass, and phytoplankton community structure in lakes fed by glacier melt and snowmelt (GSF lakes) and by snowmelt only (SF lakes) within North Cascades National Park (NOCA) in Washington State, USA. In the U.S. Rocky Mountains, glacier melting has greatly increased nitrate concentrations in GSF lakes (52–236 µg NO₃–N L^?1) relative to SF lakes (1–14 µg NO₃–N L^?1) and thereby stimulated phytoplankton changes in GSF lakes. Considering NOCA contains approximately one-third of the glaciers in the continental U.S., and many mountain lakes that receive glacier meltwater inputs, we hypothesized that NOCA GSF lakes would have greater nitrate concentrations, greater phytoplankton biomass, and greater abundance of nitrogen-sensitive diatom species than NOCA SF lakes. However, at NOCA nitrate concentrations were much lower and differences between lake types were small compared to the Rockies. At NOCA, nitrate concentrations averaged 13 and 5 µg NO₃–N L^?1 in GSF and SF lakes, respectively, and a nitrate difference was not detectable in several individual years. There also was no difference in phytoplankton biomass or abundance of nitrogen-sensitive diatoms between lake types at NOCA. In contrast to the Rockies, there also was not a significant positive relationship between watershed percent glacier area and lake nitrate at NOCA. Results demonstrate that biogeochemical responses to global change in Western U.S. mountain lake watersheds may vary regionally. Regional differences may be affected by differing nitrogen deposition, climate, geology, or microbial processes within glacier environments, and merit further investigation.     

Artificial seeding of the green seaweed Monostroma for cultivation

In Japan, the green seaweed Monostroma is an important source of humanfood. Monostroma nitidum Wittrock (Japanese name: hitoegusa) is cultivated in brackish waters and estuaries of central to southern Japan. The green seaweed Monostroma grows in the brackish water area in the upper part of the intertidal zone in the warm waters. Artificial seed culture began with the collection of many gametes in April. The resultant zygotes were allowed to adhere to plastic settlement boards (20 cm long and 10 cm wide). The zygoteboards were then cultured in tanks (1 ×2 ×0.5 m) with fertiliser in a controlled growth room (10–87 μmol photon m^-2s^-1). The cultivated zygotes on the board in the indoor tanks gradually increased in size from 10 to 40 μm in diameter during May to early August. Zygote growth became slowed at the end of August. The zygotesmatured in early September, and the plates were transferred into culture tanks in a dark room for dark treatment. Maturation of the zygote was promoted by providing dark conditions for two weeks. The production of a concentrated zoospore solution from the mature blades was achieved by adding fresh water at temperature 2–3 °C above that of the seeding vats. Zoospores were released in large numbers when exposed to strong irradiance of 100 μmol photon m^-2 s^-1 for 30 min. The zygotes produced flat unicellular fronds at the germling stage. The technology of artificial seed culture and zoospore release from the zygotes is based mainly on these experiments. This revised version was published online in August 2006 with corrections to the Cover Date.     

Characteristics of plankton communities in Chinese integrated fish ponds: effects of excessive grazing by planktivorous carps on plankton communities

Biomass and production of plankton communities were investigated in two Chinese integrated fish culture ponds in August, Dianshanhu Pond (with high density of planktivorous carp) and Pingwang Pond (with low density of planktivorous carp). The plankton communities were composed of rotifers, protozoans, phytoplankton (<40 µm) and bacteria. The large phytoplankton (>40 µm), cladocerans and copepods were rare because of grazing pressure by the carp. The density or biomass of bacteria (1.93 × 10⁷ and 2.20 × 10⁷ cells ml^–1 on average in Dianshanhu and Pingwang Ponds, respectively), picophytoplankton (24.6 and 18.5 mg m^–3 Chla on average) and rotifers (5372 and 20733 ind. 1^–1 on average) exceeded the maximum values reported for natural waters.The average [³H]thymidine uptake rates were 694 and 904 pmoles 1^–1 h^–1 (13.4 and 20.6 µgC 1^–1) and the bacterial production by the >2 µm fraction amounted 21–28% of total [³H] thymidine uptake rate in both ponds. The mean chlorophylla concentrations were 59.1 and 183 mg m^–3 in Dianshanhu and Pingwang Ponds, respectively. 82.4% and 65.3% of the total Chla was contributed by the <10 µm nano- and picophytoplankton in each pond, respectively. In particular, the picophytoplankton contribution amounted 41.2% of thtal Chla in Dianshanhu Pond. Primary production was 2.5 and 3.4 gC m^–2 d^–1 in each pond, respectively, and >50% of production was contributed by picophytoplankton. The mean biomasses of protozoa were 168 µg 1^–1 and 445 µg 1^–1 and those of rotifers were 763 µg 1^–1 and 1186 µg 1^–1 in Dianshanhu and Pingwang Ponds, respectively. The ecological efficiencies expressed in terms of the ratios of primary production to zooplankton production were 0.22 and 0.31, for the two ponds.     

Nutrient enrichment of Cabo Frio (Brasil) sea water for phytoplankton mass production

Natural phytoplankton of Cabo Frio area was grown in 42 m-deep artificially upwelled seawater enriched with increasing concentrations of nitrogen or phosphorus. Respective values allowing maximum biomass, maximum uptake of initial reserve and maximum yield coefficient are rather conflicting. Notwithstanding, respective values of 75 μg at 1⁻¹ nitrogen and 5 μg at 1⁻¹ phosphorus, and therefore N:P = 15, appeared to be the best compromise for initial nutrient levels.     

Distribution of phytoplankton community in Kotor Bay (south-eastern Adriatic Sea)

The goal of this paper was to explain variability of phytoplankton in a shallow coastal area in relation to physico-chemical parameters. Temporal variability and composition of phytoplankton were investigated in the Kotor Bay, a small bay located in the south-eastern part of the Adriatic Sea. Samplings were performed weekly from February 2008 to January 2009 at one station in the inner part of the Kotor Bay, at five depths (0 m, 2 m, 5 m, 10 m, 15 m). Phosphates, nitrites and nitrates ranged from values under the level of detection to the maximum values of 1.54, 1.53 and 23.91 μmol l⁻¹, respectively. The phytoplankton biomass — represented by chlorophyll a concentration — ranged from 0.12 to 6.78 mg m⁻³, reaching a maximum in summer. Diatoms were present throughout the whole sampling period, reaching the highest abundance in March (3.42×10⁵ cells l⁻¹at surface). The peak of dinoflagellates in July (2.2×10⁶ cells l⁻¹ at surface) was due to a single species, Prorocentrum micans. The toxic dinoflagellate Dinophysis fortii occurred at a concentration of 2140 cells l⁻¹ in May. The present results of phytoplankton assemblages and distribution provide valuable information for this part of the south-eastern Adriatic Sea where data is currently absent.     

Carbon dynamics in the 'grazing food chain' of a subtropical lake

Studies were conducted over a 13 month period at four pelagicsites in eutrophic Lake Okeechobee, Florida (USA), in orderto quantify carbon (C) uptake rates by size-fractionated phytoplankton,and subsequent transfers of C to zooplankton. This was accomplishedusing laboratory ¹⁴C tracer methods and natural plankton assemblages.The annual biomass of picoplankton (<2 µm), nanoplankton(2–20 µm) and microplankton (<20 µm averaged60, 389 and 100 µg C 1^–1 respectively, while correspondingrates of C uptake averaged 7, 51 and 13 µg C1^–1h^–1. The biomass of microzooplankton (40–200 µm)and macrozooplankton (<200 µm averaged 18 and 60 µgC 1^–1, respectively, while C uptake rates by these herbivoregroups averaged 2 and 3 µg C 1^–1 h^–1. Therewere no strong seasonal patterns in any of the plankton metrics.The ratio of zooplankton to phytoplankton C uptake averaged7% over the course of the study. This low value is typical ofthat observed in eutrophic temperate lakes with small zooplanktonand large inedible phytoplankton, and indicates ineffectiveC transfer in the grazing food chain. On a single occasion,there was a high density (<40 1^–1) of Daphnia lumholrzii,a large-bodied exotic cladoceran. At that time, zooplanktoncommunity C uptake was <20 µg C 1^–1 h^–1and the ratio of zooplankton to phytoplankton C uptake was near30%. If D.lumholrzii proliferates in Lake Okeechobee and theother Florida lakes where it has recently been observed, itmay substantially alter planktonic C dynamics.