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14C photosynthesis and pigment pattern of phytoplankton as size related adaptation strategies in alpine lakes
Abstract
The hypothesis that both photosynthesis and pigment pattern are more reflective of size related strategies than taxonomic
composition of the assemblages was tested under natural conditions in alpine lakes during fall 1999. The small size fraction
(< 10 μm) in Lake Lucerne, Mondsee and Traunsee and in an additional incubator experiment contributed 55-67 % to the total
integral of chlorophyll-a and photosynthesis per m2. The photosynthetic depression induced by UV-A in Lake Lucerne, measured during the 7th GAP-workshop, markedly increased to 65 % with PAR up to 500 μmol m-2 s-1. At super-saturating light intensities near the surface, UV-A inhibition further increased marginally to 69 %. Effects of
light acclimation and pigment adaptation on photosynthetic rates and efficiencies of phytoplankton indicated size related
strategies that were more important than the taxonomic composition of the assemblage measured in Traunsee and Mondsee. Algal
communities and small size fractions (<10 μm), that had a high maximum light utilisation coefficient (*) were adapted to low light by high ratios of chlorophyll-a to photo-protective -carotene. Algae at high solar radiation and of large size (>10 μm) were photosynthetically less efficient but high light
adapted having low ratios of chlorophyll-a to -carotene. In contrast to low light adapted small cells the high light adapted large-cells increased their relative proportion
of photo-protective carotenoids above saturating light levels. At light limitation in deeper water layers lipophilic accessory
photo-synthetic versus photo-protective pigments increased for all fractions.
Supplementary resources (3)
... Our field sample analysis confirmed overestimates of chlorophytes reported from other studies (Friedrich et al. 1998 due to their particularly high photosynthetic efficiency. Furthermore, studies have shown that a multitude of ecologically relevant features, such as the cellular content of chl a, strongly depend on the cell size of algae (Bricaud et al. 1995, Tang 1995, Teubner et al. 2001). This allometric relationship partially explains the overestimation of chlorophytes in our data set, as they have small-sized cells in Mondsee. ...
... Furthermore, the inverse relationship between DF intensity at 586 nm and seasonal light intensity and temperature predicted the significance of phycobilin-rich cryptophytes and cyanobacteria during low light and temperature periods (Gervais 1998, Vaughan et al. 2001), a plankton situation mainly occurring in autumn in Mondsee. The algal community in autumn, in particular the small-size algal fraction (2-10 lm), was shown to have a high maximum light utilization coefficient and low light saturation (Teubner et al. 2001), which was indicative of acclimation to low light intensities. ...
... The normalized DF excitation spectra highlighted the variation within photosynthetically active pigments relative to photosynthetically active chl a with seasons and depths in Mondsee. In addition, we studied the b-carotene:chl a ratio to see if this ratio might serve as a rough estimator of the balance between photoprotection and light-harvesting behavior in plankton communities analyzed by HPLC (Teubner et al. 2001, 2003, Yacobi 2003. The application of this ratio was made on three assumptions: (i) b-carotene was the almost ubiquitous photoprotective pigment in the phytoplankton, implying that algae without b-carotene (as most cryptophytes) contribute minor biovolumes; (ii) chl a measured by extraction was actually involved in light harvesting and was not enhanced by chl a derivatives through degradation processes; and (iii) chl a was the principal light-harvesting pigment in the plankton community, while other light-harvesting pigments, such as phycobiliproteins occurring in cyanobacteria and cryptophytes, were insignificant. ...
In vivo delayed fluorescence (DF) and HPLC/CHEMTAX pigment analyses were used to investigate seasonal and depth distributions of phytoplankton in a deep alpine mesotrophic lake, Mondsee (Austria). Using chl a equivalents, we determined significant relationships with both approaches. Community structure derived from pigment ratios of homogenous samples was compared with microscopic estimations using biovolume conversion factors. An advantage of the HPLC/CHEMTAX method was that it gave good discrimination among phytoplankton groups when based on a pigment ratio matrix derived from multiple regression analysis. When a single algal group was dominant, such as epilimnetic diatoms or hypolimnetic cyanobacteria in the deep chl maxima, HPLC/CHEMTAX results were significantly correlated with microscopic estimations (diatoms: r = 0.93; cyanobacteria: r = 0.94). Changes in the composition of photosynthetically active pigments were investigated with DF and benefited from excitation spectra that considered all light-harvesting pigments, which made it possible to assess the enhancement of accessory photosynthetically active pigments relative to active chl a (chl aDF672). Changes in similarity index, based on normalized DF spectra, confirmed compositional shifts observed by microscopy. At chosen wavelengths of DF spectra, 534 and 586 nm, we generally observed a significantly inverse relationship between normalized DF intensities and temperature and light along both seasonal and depth gradients. The relative increase in photosynthetically active pigments other than chl aDF672 under low light and temperature was caused by an increasing dominance of diatoms and/or phycobilin-rich cyanobacteria and Cryptophyta. DF spectra provided a more accurate picture of community pigments acclimated to light and temperature conditions than the β-carotene:chl a ratio derived from HPLC.
... Photosynthesis is interpreted as potential growth of algae and usually significantly higher than apparent growth rates calculated from the net changes in algal biomass (Tilzer, 1984;Horn and Horn, 1986;Garnier and Mourelatos, 1991). Effects of light adaptation on photosynthetic rates and efficiencies suggest that size related adaptive strategies underpin algal communities (Koschel and Scheffler, 1985;Happey-Wood, 1993;Frenette et al., 1996;Teubner et al., 2001). ...
... A pair of light and dark glass bottles (120 mL) was filled from each depth and 1 mL of 14 C-bicarbonate (4 µC = 148 k Bq) was added. Measurements were made immediately after termination of the experiments according to the protocol in Teubner et al. (2001). Ten mL of a radioactive sample was mixed with 1 mL of 1 N HCL and bubbled for 30 min (Acid Bubbling Method, Gächter et al., 1984;Schindler et al., 1972;Riemann and Jensen, 1991). ...
... These result are in agreement with laboratory measurement of photosynthetic rates of total phytoplankton assemblages from EB and VI by Weisse and Mindl (2002). We could show elsewhere for Traunsee and Mondsee, that not only photosynthesis but also the pigment pattern is subject to adaptation to the prevailing light climate (Teubner et al., 2001). High photosynthetic efficiency at low light saturation was in accordance with a high ratio of light-harvesting chlorophyll a to photo-protective β-carotene, by reducing chlorophyll content or providing photoprotective pigmentation of the light harvesting apparatus. ...
The influence of industrial tailings on the biological integrity of the phytoplankton was assessed from annual measurements of photosynthetic rates in the alpine lake Traunsee. The mean annual integral production of 21 mmol C m-2 d-1 corresponded to the oligotrophic nature of the lake. Effects of effluents were tested by comparing photosynthesis at a station close to the industrial outlet (EB) and at a reference site with a maximum depth of 190 m (VI). Between-site optical properties (vertical attenuation coefficient, euphotic depth) were statistically significant different. The euphotic zone at the impacted station was on average 2 m shallower than at the reference site, owing to turbidity emanating from the industrial plant. The adaptation to low light intensities by the algal community at this station was evident from a high maximum light utilisation coefficient (* at low light saturation (E
K). Algae at the deep reference site were photosynthetically less efficient but adapted to high light intensities. Photosynthetic adaptation to different light climates in the euphotic zone without significant quantitative biomass alterations at the impacted site gave a clear signature of biological integrity of the phytoplankton in the oligotrophic Traunsee.
... Size-scaled differences among phytoplankton are also known for the proportion of pigments in these fractions (e.g. Elser et al. 1986; Bricaud et al. 1995; Stuart et al. 1998; Teubner et al. 2001; 2003) . Smallsized phytoplankton species differ from those with larger cells in the content of Chl a per cell volume and in the ratio of lipophilic accessory photoprotective pigments to the total pool of photosynthetic pigments. ...
... The absolute values obtained in the present study are in the range of those reported for other freshwater lakes (summarized in Stockner and Antia 1986). The observed inverse relationship of specific production rates to underwater light intensity indicates low-light acclimation of this size class, which is confirmed by studies concerning size related differences in photosynthetic parameters (Platt et al. 1983; Teubner et al. 2001; Kaiblinger et al. 2006). They point out that that small-sized phytoplankters tend to have a high maximum light utilisation coefficient and low light saturation, which is indicative of acclimation to low light intensities. ...
... Large-sized phytoplankton species contain relatively higher concentrations of photoprotective carotenoids and thus have low ratios of Chl a to photoprotective ß-carotene indicative of high light acclimation (e.g. Bricaud et al. 1995; Teubner et al. 2001; 2003). In addition to pigment relationships, a higher photosynthetic efficiency via a higher light adsorbing efficiency can also be justified due to the biometry (shape) of APP cells. ...
Production rates, abundance, chlorophyll a (Chl a) concentrations and pigment composition were measured for three size classes (<2μm, 2–11μm and >11μm) of phytoplankton
from May to December 2000 in deep, mesotrophic, alpine lake Mondsee in Austria. The study focuses on differences among phytoplankton
size fractions characterised by their surface area to volume ratio ([mm2l−1: mm3l−1]), pigment distribution patterns and photosynthetic rates. Particular attention was paid to autotrophic picophytoplankton
(APP, fraction <2μm) since this size fraction differed significantly from the two larger size fractions. Among the three
fractions, APP showed the highest surface area to volume ratios and a high persistence in the pattern of lipophilic pigments
between temporarily and spatially successive samples (about 80% similarity of pigment composition between samples over seasons
and depths). The epilimnetic abundance of APP varied seasonally with an annual maximum of 180×103cellsml−1 in June (at 4–9m). The minimum (October at 12m) was more than an order of magnitude lower (4.9×103ml−1). APP peaked during autumn and contributed between 24% and 42% to the total area-integrated Chl a (10–23mgm−2) and between 16% and 58% to total area-integrated production (5–64mgm−2h−1) throughout seasons.
... Based on allometric studies, the small cells are considered as photosynthetically more efficient (e.g. [11,12]), to be well adapted because of high ratios of light-harvesting to light-protective pigments (e.g. [12]), and to have higher chlorophyll-a concentrations per unit cell volume. ...
... [11,12]), to be well adapted because of high ratios of light-harvesting to light-protective pigments (e.g. [12]), and to have higher chlorophyll-a concentrations per unit cell volume. In addition, small cells have lower respiration rates, more efficient uptake systems with relative high cell surface and densely packed intracellular cell structures (e.g. ...
The different use of P-resources between two sites in the deep oligotrophic Traunsee was studied by seasonal and vertical patterns of phytoplankton and nutrients from 12/1997 to 10/1998. The P-resources were evaluated from the proportion between the P-fractions, the dissolved reactive P (DRP), dissolved non-reactive P (DOP) and particulate organic P (PP) and from the stoichiometry between nutrients, the total N (TN), the total P (TP) and soluble reactive Si (SRSi). Significant differences between an inshore site impacted by industrial tailings (Ebensee Bay, EB) and an open water reference site (Viechtau, VI) were evident from vertical profiles of both the P-accumulation (%PP of TP) evaluated by DRP:DOP:PP and the distribution of phytoplankton assessed by Si-exhaustion (TN:TP:SRSi), but not from the seasonal patterns of phytoplankton composition, S:V ratios of the algal community or surface layer nutrient dynamics. Low TP and the stable stratification from May to September triggered the relative accumulation of epilimnetic P at VI as it was evident from both the higher portion of particulate P within TP (%PP of TP) and from the shift towards P-enrichment in nutrient stoichiometry of TN:TP:SRSi. The predominance of around 55-52% algal carbon over bacteria at the surface layer to 20m coincided spatially with the lowest Si content relative to N and P. The disturbances at the impacted site was summarised by: up to 11% less P accumulation by organisms at the surface, no stoichiometric shift towards TP in the epilimnion when compared with deeper layers and a reduction of the trophogenic zone to the top 10m. Reasons for this disturbance are seen in the unstable stratification, turbidity, higher TP and the metazoan dominated food chain. Both triple ratios, DRP:DOP:PP and TN:TP:SRSi, were sensitive indicators of the use of P-resources by plankton communities, while inorganic dissolved fractions (DIN:DRP:SRSi, DIN = dissolved inorganic N) provided only insufficient information on nutrient resources in Traunsee.
... This analysis was our first inclusion of size fractionation of the algal community to assess variation in Chl:TP. Characteristics of small phytoplankton likely contribute to an increase in Chl:TP, which include a decrease in intracellular Chl as algal cell size increases (Agustí 1991), high Chl:C ratios in small algae (Yacobi and Zohary 2010), and efficient light utilization by small algae (Teubner et al. 2001). Bioassays during one summer showed nitrogen limitation at the near-dam location (Perkins and Jones 2000), and some 45% of individual samples from these 6 sites had TN:TP ratios between 10 and 20 (n = 765), which indicates potential N-limitation (Forsberg and Ryding 1980). ...
Jones JR, Obrecht DV, Thorpe AP. 2022. Limnological characteristics of Lake of the Ozarks (Missouri, USA): long-term assessment following formation of a reservoir series. Lake Reserv Manage. XX:XXX–XXX.
Impoundment of Truman Lake in 1980 on the Osage River, above Lake of the Ozarks (LOTO), created a reservoir series. This analysis details the changes and processes over the ensuing 35 yr (1980–2014) in this large impoundment dominated by a longitudinal gradient along the mainstem. Temporal variation was determined by hydrology; seasonal mean total phosphorus (TP) ranged between 12 and 58 µg/L at the near-dam location, and hydrologic flushing during summer explained 82% of this variation. After dam closure, mineral suspended solids, attributed to channel scouring of erodible materials in the tailwater reach, declined over time, with a 50% reduction near the dam. Concurrently, organic suspended solids increased by 1 to 4%/yr in mid-reach locations, which indicates greater autotrophic production. Compared with other Missouri reservoirs, algal chlorophyll (Chl) averaged 1.6 times the value predicted from TP. Ratios of Chl:TP have increased over past decades concurrent with an increase in organic suspended solids and expansion of the ultraplankton (<11 µm) fraction of total Chl. Warm and dry conditions are associated with an increase in Chl in the ultra fraction, suggesting climate influence. A comparison with data collected prior to the closure of Truman Dam (1976–1979) provides incontrovertible evidence that light transmission has improved, and both Chl and Chl:TP have increased in LOTO. Formation of a reservoir series resulted in immediate and long-term changes in this major impoundment.
... The distinct carotenoid ratio PSC:PPC between 2-7 m and 10-12 m referred therefore mainly to the distinct phytoplankton composition between euphotic layer and the metalimnetic layer below 1% light intensity and did not show in detail the acclimatisation to underwater light climate (e.g. Descy et al., 2000;Teubner et al., 2001). Mixing in both spring and autumn led to comparable low species similarities, indicating the same rapid change of species/rapid shift of individual biovolumes during rapid nutrient turnover. ...
... Although only a small fraction of the phosphorus seems to be bio-available, this input may trigger periods of production in glacier-fed turbid lakes (Hodson, 2006;Mindl et al., 2007;Hodson et al., 2008;Sommaruga, 2015). Certain phytoplankton groups such as cryptophytes are well known to be adapted to low-light conditions because they possess a unique light-harvesting pigment complex in their photosynthetic apparatus (Gantt, Edwards & Provasoli, 1971;Spear-Bernstein & Miller, 1989;Grossman et al., 1993;Gervais, 1997) and also, Teubner et al. (2001) observed higher chl a concentrations in a smaller size fraction of algae (<10 lm) at low-light intensities. Interestingly, the cold-and lowlight-adapted green alga Koliella sp. ...
Climate warming is accelerating the retreat of glaciers and recently, many ‘new’ glacial turbid lakes have been created. In the course of time, the loss of the hydrological connectivity to a glacier causes, however, changes in their water turbidity and turns these ecosystems into clear ones.
To understand potential differences in the food‐web structure between glacier‐fed turbid and clear alpine lakes, we sampled ciliates, phyto‐, bacterio‐ and zooplankton in one clear and one glacial turbid alpine lake, and measured key physicochemical parameters. In particular, we focused on the ciliate community and the potential drivers for their abundance distribution.
In both lakes, the zooplankton community was similar and dominated by the copepod Cyclops abyssorum tatricus and rotifers including Polyarthra dolichoptera, Keratella hiemalis, Keratella cochlearis and Notholca squamula. The phytoplankton community structure differed and it was dominated by the planktonic diatom Fragilaria tenera and the cryptophyte alga Plagioselmis nannoplanctica in the glacial turbid lake, while chrysophytes and dinoflagellates were predominant in the clear one.
Ciliate abundance and richness were higher in the glacial turbid lake (∼4000–27 800 Ind L⁻¹, up to 29 species) than in the clear lake (∼570–7150 Ind L⁻¹, up to eight species). The dominant species were Balanion planctonicum, Askenasia cf. chlorelligera, Urotricha cf. furcata and Mesodinium cf. acarus. The same species dominated in both lakes, except for Mesodinium cf. acarus and some particle‐associated ciliates, which occurred exclusively in the glacial turbid lake. The relative underwater solar irradiance (i.e. percentage of PAR and UVR at depth) significantly explained their abundance distribution pattern, especially in the clear water lake. In the glacial turbid lake, the abundance of the dominating ciliate taxa was mainly explained by the presence of predatory zooplankton.
Our results revealed an unexpected high abundance and richness of protists (algae, ciliates) in the glacial turbid lake. This type of lake likely offers more suitable environmental conditions and resource niches for protists than the clear and highly UV transparent lake.
... The overall K d for PAR and spectral UV over the upper 2.5 m of both lakes was calculated as this layer was the subject of intensive studies of photosynthesis in relation to UV exposure (see Callieri et al., 2001;Köhler et al., 2001;Neale et al., 2001;and Teubner et al., 2001; all in this issue). The spectral K d measured by the PUV-500 and Satlantic showed a characteristic exponential increase in attenuation with shorter wavelengths (Fig. 7C). ...
Incident surface irradiance of photosynthetically available radiation (PAR), and ultraviolet radia- tion (UV-A and UV-B) was monitored during the GAP Workshop (8–15 September 1999) at the field stations Kastanienbaum at Lake Lucerne (434 m a.s.l.) and Piora at Lake Cadagno (1923 m a.s.l.), Switzerland, with broad band sensors (LiCOR and Macam) and multifilter spectral radio- meters (Smithsonian UV-B radiometer SR18, Satlantic and Biospherical Profilers). Calculations of clear sky spectral irradiance were performed using computer implementations of atmospheric radiative transfer models STAR and FASTRT as well as a simple two-stream model. Clear sky con- ditions prevailed at Lucerne so that detailed comparisons could be made between measured irra- diance and model predictions. Good correspondence was found for the measurements and pre- dictions. The best agreement was with the STAR model. Spectral measurements were consistent with measurements of the broad band UV-A and UV-B sensors after accounting for the manufac- turer specified spectral response. The effective center wavelength of the broad band UV-B sensor is 320 nm, despite the fact that the maximum sensitivity of the sensor is at 310 nm. A daily UV index was estimated from the midday SR18 data. An analysis of the UV-A and UV-B data at the two sites of different altitude indicates that the so called altitude effect (AE) is variable during the course of the day and usually higher for UV-B than for UV-A. Lakes Lucerne and Cadagno have moderate transparency to UV and PAR with 50 % of 320 nm irradiance penetrating to 1 m in Lake Lucerne and 0.3 m in Lake Cadagno.
... The larger relative contribution of the picoplankton size fraction to total phytoplankton photosynthesis at the low light intensity suggests that the picocyanobacteria may be adapted to low light intensities in Traunsee. A similar conclusion was reached recently for the phytoplankton size fraction <10 p,m, which included Pcy, in Traunsee and Mondsee (Teubner et al., 2001). ...
The abundance and photosynthetic activity ofpicocyanobacteria in the oligotrophic alpine lake Traunseewere measured at a station located close to the outlet ofindustrial soda waste and at a mid-lake reference stationduring spring, 1999 through to autumn, 2000.Picocyanobacterial numbers measured by flow cytometry inTraunsee (0.7–13.2 104 ml-1) were comparable tothose of other oligotrophic lakes, and there was nosignificant difference between the contaminated and thereference sampling location. Picoplankton (m)photosynthetic rates measured in vitro by the 14C-technique were significantly reduced at the contaminated siterelative to the reference station at low photosyntheticallyavailable radiation (10 E m-2 s-1), while nodifference between these two stations was found at moderatelyhigh light intensity (100 E m-2 s-1). Theinvestigation was complemented by laboratory experiments withcultured picocyanobacteria. Three Synechococcus spp.strains were exposed to water taken from either of the twoTraunsee stations and from a control station located inneighbouring Attersee. Cell-specific photosynthetic activitymeasured by 4-h in vitro incubations revealed no significantdifference among the three stations investigated. Growthrates of the same three Synechococcus spp. strains weremeasured by flow cytometry over several days in thelaboratory. One strain, in particular, was sensitive to watertaken from the contaminated site; growth rate of this strainwas significantly reduced, relative to when exposed to watertaken from the reference station. Taken together, our resultsdemonstrate that picocyanobacteria are highly sensitivebioindicators of contaminant stress. The overall impact ofthe emissions from the industrial outlet on thepicocyanobacteria was, however, relatively minor.
... The distinct carotenoid ratio PSC:PPC between 2-7 m and 10-12 m referred therefore mainly to the distinct phytoplankton composition between euphotic layer and the metalimnetic layer below 1% light intensity and did not show in detail the acclimatisation to underwater light climate (e.g. Descy et al., 2000;Teubner et al., 2001). ...
The vertical distribution pattern of algal species, chlorophylls and specific carotenoids present in the dimictic pre-alpine Ammersee (Bavaria, Germany) are given for the year 2001. A detailed taxonomic list of the phytoplankton species is recorded, along with light micrographs and detailed descriptions of the flagellates. A deep chorophyll maximum, mainly built by Planktothrix rubescens, was common in this deep mesotrophic lake. The three most dominant species among 83 identified taxa alternated seasonally and reached significant biovolumes in both the epi- and the metalimnion (Planktothrix rubescens > Ceratium hirundinella > unicellular centric diatoms > Asterionella formosa > Fragilaria spp. > Anabaena lemmermannii > Phacotus lenticularis and less frequent dominant was Rhodomonas minuta). We define a steady state phytoplankton assemblage in Ammersee as a stable community in terms of species composition and standing crop. The stability of species composition was measured by Bray-Curtis similarity between monthly samples and indicate the change of individual biovolumes of species from month to month. The stability of standing crop was evaluated by the net change of total biovolume for the same time intervals. Focussing on steady state phytoplankton assemblages we compared three spatially heterogeneous environments for vertical niche separation within the top 12 m: the euphotic epilimnion (2 and 5 m), the euphotic metalimnion (7 m) and the metalimnion below the euphotic zone with dim-light less than 1% (10 and 12 m). The definition of a steady state assemblage on both ends hold true only for metalimnetic layers at dim-light levels below 1% in Ammersee. At this metalimnetic layer more than 80% similarity in phytoplankton composition between successive monthly samples was reached, associated with almost zero net changes of total biovolume only. The greater the contribution of the three most dominant taxa to biovolume, the higher were the Bray-Curtis similarities at metalimnetic depths below the euphotic zone. Zooplankton biomass had very little effect on species assemblages in the metalimnion, while parameters related to stratification (Schmidt stability) as well as those of trophy (TP, Chl) correlated with species changes. The similarity values between successive monthly samples from all the euphotic layers never reached more than 60% and were usually significantly lower, even if biovolume net changes were around zero. Both the high fluctuations of the ratio of photosynthetic versus photo-protective carotenoids (PSC:PPC) and the statistical significance of correlations between the change of species and environmental-biotic parameters separate the euphotic layer of the top 7 m as a homogenous community from deeper strata. At all sampling depths within this euphotic zone the increase of sunshine duration was associated with an increase of the carotenoid ratio PSC:PPC, but no relationship was found for the deeper layers. The change of species in the euphotic layer was not significantly related to thermal stability, TP or the dominance structure of phytoplankton, but linked with the zooplankton biomass and therefore seemed to be top-down controlled. From our observations, we can conclude that only during stratification and only in the metalimnion below the euphotic zone steady state assemblages can be expected in the deep mesotrophic Ammersee.
The review intends to give an overview on developments, success, results of photosynthetic research and on primary productivity of algae both freshwater and marine with emphasis on more recent discoveries. Methods and techniques are briefly outlined focusing on latest improvements. Light harvesting and carbon acquisition are evaluated as a basis of regional and global primary productivity and algal growth. Thereafter, long-time series, remote sensing and river production are exemplified and linked to the potential effects of climate change. Lastly, the synthesis seeks to put the life achievements of Colin S. Reynolds into context of the subject review.
The long-term phytoplankton study in groundwater-seepage lake Alte Donau, a former side-arm of the Danube River in Vienna, covers four main lake treatment periods (1-4) from 1993 to 2014. During hypertrophic conditions with annual total phosphorus (TP) concentrations of 50-70 μg L and mean summer phytoplankton biovolume of 18-24 mm L before restoration (1), the filamentous cyanobacterium Cylindrospermopsis raciborskii was the main taxon in association with Limnothrix redekei. The drastic phosphorus reduction by chemical RIPLOX-precipitation was repeated twice (2a/b, 1995 and 1996) and resulted in a prompt drop of summer phytoplankton to 4.6 mm L in 1995 and 1.7 mm L in 1996. Non-filamentous cyanobacteria contributed here only moderately while relative high peak contributions of chlorophytes occurred. After years of re-establishment of macrophytes (3), the summer phytoplankton biovolume remained low during the period of sustained 'stable conditions' (4) with values between 0.5 and 1.5 mm L. In the long-term, phytoplankton was responding to low annual total phosphorus (10-11 μg L) which finally indicated a mesotrophic state close to oligotrophic conditions according to the lake classification scheme. The long-term median of chlorophyll-a (chl-a) content was 0.50% of wet weight phytoplankton biomass. As the phytoplankton composition shifted from a cyanobacteria dominated assemblage to a phytoplankton assemblage that was composed of taxa of various taxonomic affiliations, the chl-a content varied considerably. Chl-a content reached its lowest median value of 0.19% when cyanobacteria formed blooms contributing 77% to total phytoplankton (period 1) and was highest with 0.83% during the peak development of chlorophytes which contributed 18% to total biovolume (period 2b). The relationship between phytoplankton chl-a and TP is more robust than between phytoplankton biovolume and TP for indicating the lake's trophic state, although both response curves are statistically significant and provide roughly the same main picture of an ecosystem shift from hypertrophic in 1993 to mesotrophic in 2000 and the persistence of mesotrophic conditions for the 15 recent years. Trophic shifts were also indicated by the phytoplankton assemblage metric when comparing phytoplankton species composition between the lake treatment periods. The main picture of seasonal development of phytoplankton taxa and functional phytoplankton groups indicated that assemblages either prevailed in winter to spring or summer to autumn. Annual phytoplankton development thus seems primarily distinctive between the two half-year-cycles, namely the winter-spring and the summer-autumn period, rather than between the four seasons. While the seasonal development of phytoplankton follows the lake phenology commonly observed in temperate lakes, long-term compositional shifts of phytoplankton especially responded to the sustained reduction of TP forced by lake treatment measures in Alte Donau.
Productivity of aquatic vegetation determines the trophic level of any freshwater ecosystem. Phytoplankton photosynthetic rates are particularly relevant. Results are reported here on photosynthetic rates, primary productivity and associated parameters of phytoplankton from a polymictic, groundwater seepage lake in an urban environment before, during and after restoration measures. In addition, a simple regression model is presented to approximate daily column production from column integrated chlorophyll-a measurements. Calculated and estimates phytoplankton annual lake production is compared to production by submerged vascular plants. Results indicate that macrophytes played an essential role during the clear water phase preceding the eutrophication phase associated with intense algal productivity and vanishing submersed plant production. Internal restoration measures led to rapidly decreasing phytoplankton production and slowly re-appearing macrophytes. The rehabilitation phase following this period was characterized by declining phytoplankton productivity and re-establishing of macrophyte production. Total lake production as the sum of phytoplankton and macrophyte production declined from 626 t C to 186 t C during 1993–1996 mainly as a result of declining plankton production. During rehabilitation phytoplankton production further declined and macrophyte production regained importance. The interannual variability was ascribed to changes in the winter North Atlantic Oscillation Index. The index significantly correlated with lake production explaining 48% of the variability.
Chapter 9: The long-term phytoplankton study in groundwater-seepage lake Alte Donau, a former side-arm of the Danube River in Vienna, covers four main lake treatment periods (1-4) from 1993 to 2014. During hypertrophic conditions with annual total phosphorus (TP) concentrations of 50-70 μg L and mean summer phytoplankton biovolume of 18-24 mm L before restoration (1), the filamentous cyanobacterium Cylindrospermopsis raciborskii was the main taxon in association with Limnothrix redekei. The drastic phosphorus reduction by chemical RIPLOX-precipitation was repeated twice (2a/b, 1995 and 1996) and resulted in a prompt drop of summer phytoplankton to 4.6 mm L in 1995 and 1.7 mm L in 1996. Non-filamentous cyanobacteria contributed here only moderately while relative high peak contributions of chlorophytes occurred. After years of re-establishment of macrophytes (3), the summer phytoplankton biovolume remained low during the period of sustained 'stable conditions' (4) with values between 0.5 and 1.5 mm L. In the long-term, phytoplankton was responding to low annual total phosphorus (10-11 μg L) which finally indicated a mesotrophic state close to oligotrophic conditions according to the lake classification scheme. The long-term median of chlorophyll-a (chl-a) content was 0.50% of wet weight phytoplankton biomass. As the phytoplankton composition shifted from a cyanobacteria dominated assemblage to a phytoplankton assemblage that was composed of taxa of various taxonomic affiliations, the chl-a content varied considerably. Chl-a content reached its lowest median value of 0.19% when cyanobacteria formed blooms contributing 77% to total phytoplankton (period 1) and was highest with 0.83% during the peak development of chlorophytes which contributed 18% to total biovolume (period 2b). The relationship between phytoplankton chl-a and TP is more robust than between phytoplankton biovolume and TP for indicating the lake's trophic state, although both response curves are statistically significant and provide roughly the same main picture of an ecosystem shift from hypertrophic in 1993 to mesotrophic in 2000 and the persistence of mesotrophic conditions for the 15 recent years. Trophic shifts were also indicated by the phytoplankton assemblage metric when comparing phytoplankton species composition between the lake treatment periods. The main picture of seasonal development of phytoplankton taxa and functional phytoplankton groups indicated that assemblages either prevailed in winter to spring or summer to autumn. Annual phytoplankton development thus seems primarily distinctive between the two half-year-cycles, namely the winter-spring and the summer-autumn period, rather than between the four seasons. While the seasonal development of phytoplankton follows the lake phenology commonly observed in temperate lakes, long-term compositional shifts of phytoplankton especially responded to the sustained reduction of TP forced by lake treatment measures in Alte Donau.
Die Primärproduktion, im Wesentlichen der grünen Pflanzen, bildet heute in nahezu allen Ökosystemen die Grundlage jedweden Lebens auf der Erde. Sie bildet daher einen ganz wesentlichen Bestandteil der allgemeinen Ökologie. Entsprechend groß war seit langem das wissenschaftliche Interesse an der Erfassung, Analyse und dem Vergleich der Primärproduktion verschiedener Ökosysteme. Im aquatischen Bereich, speziell nach der Einführung verbesserter Messmethoden Anfang der 1950er-Jahre, hat dies zu einer kaum mehr überblickbaren Flut von Veröffentlichungen geführt. Im Verlauf der folgenden Ausführungen werden deshalb Literaturstellen meist nur beispielhaft aufgeführt. Wegen der konzeptuellen, methodischen und physiologischen Nähe der marinen Primärproduktion wird bei Zitaten keine Rücksicht auf die limnologische Natur des vorliegenden Handbuches genommen Für ein vertieftes Verständnis wird der Leser auf die zahlreichen Zusammenfassungen und die darin genannte Literatur verwiesen (Photosynthese: STEEMANN-NIELSEN (1975), HOFFMANN (1987), GEIDER & ÜSBORNE (1992), LAWLOR (1993), FALOWSKI & RAVEN (1997), LARKUM et al. (2003); Algenphysiologie: PLATT (1981), HARRIS (1978); Methoden: VoLLENWEIDER (1969), LI & MAESTRINI (1993), SCHWOERBEL (1994); Primärproduktion allgemein: GESSNER (1959), WESTLAKE et al. (1998)). Gute Übersichten über die Geschichte der Primärproduktionsforschung bieten LIETH (1975), PETERS ON (1980) und BARBER & HILTING (2002).
Inhalt
IV-9.2 Primärproduktion (autotrophe Produktion)
Produktion aquatischer Systeme
1 Grundlagen
2 Begriff und Definitionen
3 Pigmente
4 Methoden
5 Respiration
6 Produktion und Außenfaktoren
7 Photosynthetische Profile
8 Primärproduktion in Binnengewässern
9 Literatur
Seasonal changes in vertical distribution of Daphnia galeata and other zooplankters were monitored in lake Lombola (69 07′ N). Depth-habitat use, availability of edible algae and zooplankton densities were recorded to examine seasonal changes in intensity of competition between Daphnia and the other herbivores in the lake. Early in July, the exephippial generation of Daphnia aggregated near the surface, independently of body-size. In late July, when fish planktivory was expected to increase, the daphnids moved down during the day. In August, as intraspecific competition for food intensified, small and large Daphnia partitioned the water column, with larger individuals staying deeper. In September, Daphnia became dominated by large individuals, edible phytoplankton reached the seasonal minimum, and the vertical distribution of Daphnia gradually stretched out towards the surface. The observations on food availability and zooplankton densities suggest that interspecific competition intensified by the end of July. Species and stages that were most exposed to exploitative and interference competition by Daphnia were those staying deeper, because their vertical distribution overlapped more with the larger, competitively superior daphnids. These susceptible competitors included Keratella cochlearis and Synchaeta, among the rotifers, and nauplii and early copepodite stages of Cyclops scutifer. Depth-habitat use is discussed in relation to copepod development, zooplankton dynamics and predator-mediated coexistence.
Taxonomic composition and productivity of winter and spring phytoplankton in a eutrophic estuary have been investigated in order to elucidate the carbon flux under conditions of limitation by physical factors – light and temperature. In spite of the important differences in nutrients, solar radiation and water temperature between winter and spring season, mean concentrations of particulate organic carbon were equal to 13.2 and 13.0 mgC l−1, respectively. Chlorophyll a averaged at 79 μgChl l−1 in winter, that is 69% of spring. Although community respiration accounted for only 6–26% of light saturated photosynthesis, integrated net primary production of the 1.2 m deep water column was negative until April. High attenuation of the water body (Ko = 2.9 m−1) lead to a negative carbon balance (net heterotrophy) below 35 cm for all sampling dates. Thus, the high winter POC and phytoplankton values can only originate from summer or autumn primary production. This assumption was supported by a carbon loss rate of just 3% of total organic carbon per day for the whole water column. The composition of phytoplankton was very constant through both seasons: 39% Chlorophyceae, 33% Cyanobacteria and 25% Bacillariophyceae. As expected, phytoplankton was low light acclimated, having high α values (slope of light limited photosynthesis), but moderate maximum photosynthesis rates at saturating irradiances, which were heavily affected by temperature. Calculation of net carbon flux yet showed net heterotrophy of the Bodden waters in winter and early spring were caused by external physical limitation (low surface irradiance and low temperature) in combination with a high light attenuation of the water body.
The primary production of the phytoplankton is one of the most important sources of the energy input in freshwater ecosystems (Moss 1980). A broad knowledge of endogenous and exogenous control mechanisms of phytoplanktonic primary production is necessary to obtain basic information on the energy flow in the ecosystem of Lake Stechlin. Pretreatment conditions of the phytoplankton population as well as factors concerning the regulation of the overall carbohydrate metabolism of the algae and the integration of the photosynthetic products into development and growth of phytoplankton allow a better understanding of the lake metabolism as a whole (Harris 1978).
Carbon assimilation is usually measured at fairly constant light intensities. Under natural condi- tions, however, planktonic algae are moved through the water column and experience light of fluc- tuating intensity and spectral composition. They may cope with strong UV for a short residence in the upper water layer. In order to estimate the effects of UV on primary production of phyto- plankton under conditions of turbulent mixing, we compared carbon assimilation and exudation of algae incubated in UV-transparent quartz and in UV-absorbing glass bottles which were moved through different water layers. Computer-controlled elevators were used to simulate mixing depths between 2 and 14 meters. Compared to the glass bottles, particulate C assimilation in the quartz bottles was reduced by 20-30% at mixing depths between 2 and 10 m. There was no sig- nificant difference between both types of incubation bottles at a mixing depth of 14 m. Exudation was enhanced by UV near the water surface (mixing depth up to 4 m) but not in the deep-mixed samples. Our results indicate serious damage of planktonic algae by UV even under conditions of vertical mixing if the euphotic zone exceeds the mixing depth. Depression was low for circulation through the whole euphotic zone and may disappear at even deeper mixing. Our results indicate lower photoinhibition per UV dosage at fluctuating than at constant light intensities. A model pre- dicting inhibition as function of weighted irradiance spectra was adapted to describe wavelength dependent photoinhibition occurring at different mixing depths. The model results agreed very well with the inhibition rates measured under fluctuating light. These preliminary results are used to discuss the importance of UV on photosynthesis of planktonic algae in aquatic environments of different mixing depths and stabilities of stratification.
Photosynthetic pigments extracted from the particulate material of the water column of Lake Kinneret were studied throughout the periods of May 1988-June 1989, and November 1993-November 1994, by means of HPLC The temporal and vertical variation of the pigment suite found agreed with the microscopically determined phytoplankton record. The regression calculations of taxon-specific biomass with the corresponding signature pigments suggest that pigment analysis may be a useful tool for the monitoring of bloom-forming species, e.g. the dinoflagellate Peridinium gatunense Nygaard. The HPLC pigment analysis permitted the identification and quantification of chlorophyll degradation products, providing for the first time information about their composition in Lake Kinneret. Chlorophyllide a was the major detectable degradation product of chlorophyll a, varying between 1 and 9% of the chlorophyll a concentration. Other chlorophyll a derivatives appeared mostly in minor quantities. Pheophytin a was virtually lacking in all the samples Removal rates of pigments measured by sedimentation traps, indicated that the degradation of chlorophyll a via chlorophyllide a is a dynamic process that continues during the sedimentation of the phytoplankton particles.
We examined the possibility of using the acidification and bubbling method (ABM) to determine phytoplankton primary production in coastal marine environments. Our results from a number of laboratory and field experiments, suggested that (i) incubations of samples can be carried out in glass vials instead of using the normal incubation bottles, and (ii) storage of samples fixed with formalin or glutaraldehyde can be carried out for at least 8 weeks without a change in radioactivity. In the course of our work, we designed a new manifold removing excess C-14 via ABM. A linear correlation between the G24-max values obtained by the two techniques (r = 0.93) was found. On average the ABM gave values 1.8 times higher than those yielded by the particulate filtration procedure. On a square metre basis, the ABM gave values 1.4 times higher than those yielded by the particulate filtration procedure. The annual production at six marine locations was 57% higher when using the ABM. The ABM is superior to the traditional filtration procedure, because filtration artefacts are avoided, precision is improved, the dissolved primary production is included in the measurement, and the immediate amount of field work is considerably reduced.
The effects of UVB radiation on the activity of heterotrophic (HPP) and autotrophic (APP) picoplankton (0.2-2 μm) and of autotrophic assemblages >2 μm has been measured and compared. Under natural UVB irradiance in a large, deep, oligotrophic subalpine lake (Lago Maggiore, 45°55'N) with mean dissolved organic carbon (DOC) concentrations of I mg C 1-1, the microorganisms of the two size fractions were not significantly photoinhibited in their autotrophic and heterotrophic activities. The vertical attenuation coefficient (K(d)) for irradiance at 305 nm ranged from 1.45 to 1.67 during spring and summer. The mixing layer extended to a greater depth than the layer affected by UVB radiation (Z1(%) < Z(mix)), thus enabling the microorganisms living there to photoadapt. As the assimilation numbers of APP and nanoplankton were higher at 2 m depth than near the surface, we suspected that the influence of longer wavelength (UVA, photosynthetically active radiation) could be stronger than UVB in affecting the photosynthetic efficiency of natural populations. The artificial increase in UVB irradiance had a higher detrimental effect on HPP due to their smaller size, less protection and indirect effects through autotrophic cell inhibition. Picocyanobacteria were percentually more affected by UVB than nanoplankton during April due to the presence of diatoms, which are more resistant than other algal groups to solar UVB irradiance. Furthermore, picocyanobacteria had lower assimilation numbers with respect to larger phytoplankton in the quartz tubes during stratification.
The diurnal vertical migration (DVM) behaviour of three species of cryptophytes of differing size (Rhodomonas minuta var. nannoplanctica and two species of Cryptomonas) was examined in 4 m tall laboratory columns in relation to gradients of light, temperature and nutrients. Differences were found in the DVM behaviour of the three species in relation to these environmental variables. Both species of Cryptomonas were able to cross steep thermal gradients whereas Rhodomonas did not. All three species avoided high levels of irradiance, especially when the cells were phosphorus-depleted. The large species of Cryptomonas made use of vertically separated resources of light and phosphorus by migrating from the illuminated, but phosphorus-depleted, upper layer during daytime to the phosphorus-rich hypolimnion at night. The smaller species of Cryptomonas had a reverse pattern of DVM swimming upwards during darkness, indicating a strong negative geotaxis. Moreover, downward migration of this smaller Cryptomonas ceased abruptly at the thermocline giving rise to well developed mid-water maxima in contrast to the larger species. The migration speeds of the Cryptomonas species were up to 0·7 m h and cells were able to move quickly in response to environmental changes in the water column. The results demonstrate the importance of both the physiological state of the cells and the external physical and chemical conditions, particularly irradiance, as factors regulating the DVM behaviour of cryptophytes.
Variability in the chlorophyll (chl) a-specific absorption coefficients of living phytoplankton a* sub(ph) ( lambda ) was analyzed using a data set including 815 spectra determined with the wet filter technique in different regions of the world ocean (covering the chlorophyll concentration range 0.02-25 mg m super(-3)). The a* sub(ph) values were observed to decrease rather regularly from oligotrophic to eutrophic waters, spanning over more than 1 order of magnitude (0.18 to 0.01 m super(2) mg super(-1)) at the blue absorption maximum. The observed covariation between a* sub(ph) ( lambda ) and the field chl a concentration can be explained considering (1) the level of pigment packaging and (2) the contribution of accessory pigments to absorption. Empirical relationships between a* sub(ph) ( lambda ) and were derived by least squares fitting to power functions. These relationships can be used to produce a* sub(ph) spectra as a function of . Such a simple parameterization, if confirmed with further data, can be used, e.g., for refining estimates of the carbon fixation rate at global or regional scales.
The effect of solar UVB radiation on the growth and species composition of phytoplankton from a high-mountain lake (2417 m a.s.l.) was studied in situ for 16 days in two enclosures of 1 m(3), receiving either full sunlight or sunlight without UVB. A total of 20 species were identified in both enclosures, consisting mainly of dinoflagellates, chrysophytes and diatoms. During the experiment, there were no significant differences in phytoplankton species composition between the two enclosures. In both treatments, the abundance of phytoplankton increased continuously, and chlorophyll a changed by similar to 5-fold. We observed high fluctuations in the abundance of several species. However, these fluctuations occurred in both enclosures, and hence they were not related to UVB radiation. Some species were affected by daily fluctuations of radiation (UVA + photosynthetically active radiation). Cyclotella aff. gordonensis showed a robust positive correlation, whereas species of Gymnodinium were negatively correlated. For most species, the sensitivity to radiation found during the experiment was consistent with their diurnal vertical distribution in the lake. Our findings suggest that the phytoplankton from this very clear lake (10% of the surface UVB radiation at 305 nm reached 9.6 m depth) were well adapted to the high UVB radiation characteristic of high-elevation sites.
This introductory article of the special GAP issue gives an overview on general limnological characteristics of the prealpine Lakes Zürich and Lucerne and the alpine Lake Cadagno and reports on the specific situation of primary production parameters during the international GAP Workshop in mid September 1999. Furthermore, it describes methods used for water analysis and fieldwork in these lakes.¶A comparison of data related to primary production in the three lakes in September 1999 during stratification shows that (i) phytoplankton community structure varied considerably between the lakes. The dominating algae were Planktothrix rubescens in Lake Zürich, various chrysophytes and diatoms in Lake Lucerne, and Echinocoleum elegans in Lake Cadagno, (ii) the euphotic zone in Lake Lucerne was considerably deeper (app. 15m) than in the other two lakes (app. 10 m), (iii) chlorophyll a standing crop was highest in mesotrophic Lake Zürich (August: 121 mg m-2), followed by oligotrophic Lake Lucerne (August: 75, September: 34 mg m-2) and mesotrophic Lake Cadagno (August: 33, September: 25 and 14 mg m-2), and (iv) areal primary production was highest in Lake Zürich (August: 105, September: 124 mg C m-2 h-1), followed by Lake Cadagno (August: 102, September: 52 mg C m-2 h-1) and Lake Lucerne (August: 90, September: 52 mg C m-2 h-1). Physiological parameters, determined in situ from P versus I relationships, showed a lower initial slope α in Lake Lucerne (August: 0.03, September: 0.02 mg C mg-1 chl a h-1μmol-1 m2 s) than in the other two lakes (Lake Zürich in August: 0.05, in September: 0.11; Lake Cadagno in August: 0.05, in September: 0.11 and 0.28 mg C mg-1 chl a h-1μmol-1 m2 s). Lake Zürich showed the lowest AN
max (August: 2.6, September: 3.2 mg C mg-1 chl a h-1, as compared to 5.9 - 7.4 mg C mg-1 chl a h-1 in the Lakes Lucerne and Cadagno), while in Lake Cadagno the highest inhibitory effects of C-assimilation were found (highest slopes of inhibition β, 0.007-0.011, as compared to 0.0003-0.0026 in the other two lakes), due to a higher UV-exposure in this alpine lake.
The sensitivity of photosynthesis to ultraviolet radiation (UV) was assessed for phytoplankton assemblages in two Swiss lakes, pre-alpine Lake Lucerne (Vierwaldstättersee) and alpine Lake Cadagno, using both in situ and laboratory incubations. Biological weighting functions for UV inhibition of photosynthesis (BWFs) were determined in the laboratory using polychromatic exposures in a Xe-lamp based incubator. Samples were concurrently incubated in situ under UV exposed and protected bottles (profiles 0-5 m), while additional spectral treatments were carried out at the 50 % UV-B penetration depth: full spectrum, UV-A only (Mylar protected) and UV protected quartz tubes. Both particulate (> 0.2 μm) and total organic carbon incorporation were measured. Measured attenuation coefficients and incident UV spectral irradiance data was used to evaluate a BWF/photosynthesis-irradiance model (BWF/P-I) for in situ exposure conditions and compared with measurements. The BWFs showed sensitivity across the UV spectrum at similar, though somewhat lower, levels than an average BWF for marine assemblages. Relative photosynthesis in situ (UV exposed/UV excluded) was about 40 % at the surface and about 60 % at the 50 % UV-B penetration depth. Similar inhibition was predicted by the BWF/P-I model. Generally, full spectrum (UV-B and UV-A) exposure had little additional effect compared to UV-A only exposure. Reciprocal transfer of samples between lakes showed enhancement of UV effects in L. Cadagno compared to incubation of the same sample in L. Lucerne, consistent with increased UV sensitivity due to the 5°C cooler water temperature in L. Cadagno. Similarly, BWF prediction of in situ response in L. Cadagno was improved by increasing UV sensitivity according to a Q
10 of 2. Full profile calculations using the BWF/P-I model suggest stronger effects of UV on L. Lucerne compared to L. Cadagno phytoplankton due to greater sensitivity of the assemblage combined with higher overall transparency to UV relative to PAR in L. Lucerne. The BWF/P-I model was a good overall predictor of UV-dependent photosynthetic performance in these lakes.
14C uptake was measured in experimental bottles suspended at a series of fixed depths (using subsamples from one sample depth), and was compared with estimates obtained from bottles provided with vertical movement similar to that which might occur in Langmuir circulations. In most experiments, the vertically cycled bottles gave estimates of integral photosynthesis 19 to 87% higher than estimates from the control series. Evidence from laboratory experiments detailing the change in photosynthesis over time at various irradiance levels shows that a higher lightsaturated photosynthetic rate under variable light conditions could account for the enhanced integral photosynthesis found in the bottles provided with vertical movement.
This tutorial was designed for nonbiologists requiring an introduction to the nature and general timescales of phytoplankton responses to physical forcing in aquatic environments. As such, an effort was made to highlight biological markers which might assist in identifying, measuring and/or validating physical processes controlling the variability in the distribution, abundance, composition and activity of phytoplankton communities. Given the recent advances in environmental optics and remote sensing capabilities, a special emphasis was placed on the nature and utility of phytoplankton optical properties in current bio-optical modelling efforts to predict temporal and spatial variability in phytoplankton productivity and growth.
Using a ternary gradient system, over 50 carotenoids, chlorophylls and their derivatives were separated from marine phytoplankton. Only 2 pairs of carotenoid pigments (19'-butanoyloxyfucoxanthin and siphonaxanthin, and 19'-hexanoyloxyfucoxanthin and 9'-cis-neoxanthin) and 3 chlorophylls (chlorophylls c1, c2 and Mg 2,4 divinyl pheoporphyrin a5 monomethyl ester [Mg2,4D]) were not resolved. Pigment chromatograms are presented for 12 unialgal cultures from 10 algal classes important in the marine environment: Amphidinium carterae Hulbert (Dinophyceae); Chroomonas salina (Wislouch) Butcher (Cryptophyceae); Dunaliella tertiolecta Butcher (Chlorophyceae); Emiliania huxleyi (Lohmann) Hay et Mohler and Pavlova lutheri (Droop) Green (Prymnesiophyceae); Euglena gracilis Klebs (Euglenophyceae); Micromonas pusilla (Butcher) Manton et Parke and Pycnococcus provasolii Guillard (Prasinophyceae); Pelagococcus subviridis Norris (Chrysophyceae); Phaeodactylum tricornutum Bohlin (Bacillariophyceae); Porphyridium cruentum (Bory) Drew et Ross (Rhodophyceae), and Synechococcus sp. (Cyanophyceae). A chromatogram is also given of a complex mixture of over 50 algal pigments such as might be found in a phytoplankton field sample. This method is useful for analysis of phytoplankton pigments in seawater samples and other instances where separations of complex pigment mixtures are required.
A global assessment of carbon flux in the world ocean is one of the major undertakings of the Joint Global Ocean Flux Study (JGOFS). This has to be undertaken using historical in situ data of primary productivity. As required by the temporal and spatial scales involved in a global study, it can be conveniently done by combining, through appropriate models, remotely sensed information (chlorophyll a, temperature) with basic information about the parameters related to the carbon uptake by phytoplanktonic algae. This requires a better understanding as well as a more extended knowledge of these parameters which govern the radiative energy absorption and utilization by algae in photosynthesis. The measurement of the photosynthetic response of algae [the photosynthesis (P) versus irradiance (E) curves], besides being less shiptime consuming than in situ primary production experiments, allows the needed parameters to be derived and systematically studied as a function of the physical, chemical and ecological conditions. The aim of the present paper is to review the significance of these parameters, especially in view of their introduction into models, to analyze the causes of their variations in the light of physiological considerations, and finally to provide methodological recommendations for meaningful determinations, and interpretation, of the data resulting from P versus E determinations. Of main concern are the available and usable irradiance, the chlorophyll α-specific absorption capabilities of the algae, the maximum light utilization coefficient (α), the maximum quantum yield (Φm), the maximum photosynthetic rate (P(m)) and the light saturation index (E(k)). The potential of other, non-intrusive, approaches, such as the stimulated variable fluorescence, or the sun-induced natural fluorescence techniques is also examined.
On the occasion of the workshop of the group on aquatic primary productivity (GAP) held in Konstanz (1982), 14C-uptake rates were determined by two widely used, well-established procedures. In order to avoid any variation in the results
caused by manipulation of the samples, subsamples for both determinations were withdrawn from the same bottles. The acid-bubbling
method (ABM) yielded results which exceeded those of the filtration method by about 30%. Excretion of 14C labelled dissolved organic matter was negligibly small and therefore cannot account for the observed differences. Based
on available information also other possible explanations discussed can Likely be dismissed. Hence additional effort is needed
to identify and eliminate possible shortcomings in either method.
Phytoplankton photosynthetic responses were studied in two basins of an oligotrophic lake (Québec, Canada). which are characterized by the absence (shallow Basin 1) and presence (deeper Basin 2) of seasonal thermal stratification. Size-fractionated photosynthesis was used to characterize changes in phytoplankton characteristics during periods of seasonal mixing and stratification. Seasonal variations of P max showed size-related differences, with maximum values in July for the picoplankton and in November for the nanoplankton. Similar patterns of variability in α and l k were observed for the two size fractions throughout the season. However, size-related differences in the magnitudes of l k indicate that the picoplankton have lower light requirements than the nanoplankton to saturate photosynthesis and can sustain large variations of irradiance in the surface layer during their growth season. Tight inverse correlations between in situ irradiance and α, at the seasonal scale, indicate that the two size fractions respond to lower irradiance by increasing their photosynthetic efficiencies. P max and α are strongly correlated for the two size fractions, which suggests that biochemical processes controlling these two parameters are closely coupled. Hydrodynamics may influence photosynthesis differently for pico- and nanoplankton. Picoplankton in Basin 1 are adapted to higher irradiance than those in the euphotic zone of Basin 2, as shown by their lower α and higher l k during most of the study period, which may be explained by more frequent exposure to high irradiance through mixing in the shallowest basin. Vertically changing photosynthetic parameters in Basin 2 show that both pico- and nanoplankton were photoadapted as a function of depth. The size-related pattern of residence in the water column coupled to the turbulence regime in the epilimnion may be responsible for size-related differences in photoadaptation.
Dark uptake of inorganic 14C by offshore plankton was measured at two depths at 36 stations in the Atlantic Ocean from 52°S to 26°N, mainly along 30°W. The samples were incubated for 2 h with and without inhibition of biological activity with HgCl 2 . In addition, six time course experiments were performed. The mean dark uptake rate varied from 0.68 to 4.82 (µmol C m−3 h−1 over the transect and showed a significant positive relationship with chlorophyll a. The dark uptake was usually >5% of the maximum photosynthetic capacity ( P m), and higher values relative to P m were associated with low values of P m and not with high absolute dark values. A linear relationship between dark uptake and P m was found with a background value (y-axis intercept) of 0.51 (µmol C m−3 h−1 and a slope of 0.77% of P m. A major fraction of the dark signal, 66–80% of the total signal, persisted in bottles treated with HgCl2, indicating that most of the dark signal was independent of biological activity. Time course experiments showed a linear dark uptake with time for the first hours, whereafter the uptake ceased. At stations with low concentrations of inorganic nitrogen [>1 (µmol (NH 4 ++NO 3 −)], a second stage was observed after 3–8 h, probably due to an increase in bacterial activity. The results suggest three mechanisms for the dark value in short-term incubations in oligotrophic waters. A background value independent of biomass and incubation time which was the dominant part of the dark signal in samples with very low phytoplankton biomass (>0.3 p-g Chi a 1“). Another important part was residuals of 14C associated with plankton, probably adsorbed to compounds inside the cells. This fraction was dominant in short-term incubations at chlorophyll concentrations >0.3 p.g Chi a H. Active uptake by living cells (total minus ‘HgCl2 uptake‘) was only a minor part of the dark signal in short-term incubations, but dominated at longer incubation time (>3–9 h), probably driven by an increase in bacterial activity. A significant enhancement of the non-photosynthetic uptake of 14C was observed in light, probably associated with a carbon-concentrating mechanism in phytoplankton or light stimulation of β-carboxylation activity. The results strongly suggest that dark values should be subtracted from the light uptake. This correction is particularly important when photosynthetic rates are low, e.g. at low light or in short-term incubations where a time-zero background becomes a significant part of the total uptake in light.
A high-performance liquid chromatography (HPLC) method is presented with which a direct determination of the phytoplankton
biomass is possible. By correlating over 100 samples investigated with HPLC as well as microscopically, it has been shown
that phytoplankton biomass is described very accurately by determining the concentration of accessory pigments. In contrast
to earlier studies, we made a direct correlation of marker pigments with biovolume and did not consider the ratio of marker
pigment to chlorophyll a. Determination of the dominating class in each lake succeeded with correlation coefficients > 0.90,
and even 0.96 against total biovolume. Because of the large number of samples, statistical proof indicates that algal marker
pigments are better indicators for phytoplankton biomass than chlorophyll a. This HPLC method is ideal for large-scale monitoring because of its suitability for routine analysis and its extensive sample
throughput. The procedure is applicable to different natural waters, from oligotrophic to highly eutrophic. Because of the
simultaneously performed analysis of chlorophyll a, the succession of existing data is ensured.
Phytoplankton structure and dynamics of four eutrophic lakes of Berlin were studied in 1992. The biomass change of relevant classes - Cyanophyceae, Bacillariophyceae, Cryptophyceae, and Chlorophyceae - is well represented by HPLC-analysis of photosynthetic lipophilic pigments simultaneously carried- out. Nevertheless, an estimation of algal class biovolumes or phytoplankton composition, on the basis of chromatographically recorded pigment data is restricted to a semi-quantitative consideration. Different pigment amounts in individual species of the same algal class or varying marker pigment/chlorophyll-a ratios are discussed as a reason for the misleading pigment-based quantification of phytoplankton dynamics. However, the analysis of the obtained data points to the possibility of using HPLC-aided pigment determinations in connection with microscopic cell counting for a detection of variable physiological states under field conditions; provided that mass developments of algae are dominated by a single species as common in eutrophic lakes. For time periods with dominating Planktothrix agardhii or Microcystis spec. a positive correlation was found between their content of the cyanophyte specific pigment echinenone and increasing nitrogen availability. In contrast, no relations could be detected between the changing fucoxanthin content of Aulacoseira spec. and any of the measured environmental parameters (nutrient concentrations or light climate).
The lipophilic photosynthetic pigments in Limnothrix redekei, Planktothrix agardhii (cyanobacteria), Stephanodiscus minutulus, Synedra acus (diatoms), Scenedesmus acuminatus, and Scenedesmus armatus (chlorophycean) all isolated from an eutrophic lake were quantitatively determined by HPLC. The algae were grown semi‐continuously under nutrient sufficient conditions at 20°C at a 12/12 h light/dark cycle with constant irradiance or with simulated natural light fluctuations as well as at a 6/18 h light/dark cycle with constant irradiance, all at the same daily light exposure.The zeaxanthin and the myxoxanthophyll contents of cyanobacteria were not influenced by fluctuating light, a short photoperiod or a different sampling time. The chlorophyll b/a ratio, the lutein/chlorophyll a ratio, and the neoxanthin content of chlorophycean as well as the chlorophyll c/a and the fucoxanthin/chlorophyll a ratio of diatoms were only slightly influenced by these factors. Therefore in some cases marker pigment contents and in other cases marker pigment/chlorophyll a ratios may be more useful for quantifying the relative importance of different taxonomic groups in natural phytoplankton. Simulated natural light fluctuations or the length of the photoperiod only slightly influenced the pigment content or the marker pigment/chlorophyll a ratio.
Concerns about stratospheric ozone depletion have stimulated interest in the effects of UVB radiation (280-320 nm) on marine phytoplankton. Research has shown that phytoplankton photosynthesis can be severely inhibited by surface irradiance and that much of the effect is due to UV radiation. Quantitative generalization of these results requires a biological weighting function (BWF) to quantify UV exposure appropriately. Different methods have been employed to infer the general shape of the BWF for photoinhibition in natural phytoplankton, and recently, detailed BWFs have been determined for phytoplankton cultures and natural samples. Results show that although UVB photons are more damaging than UVA (320-400 nm), the greater fluxes of UVA in the ocean cause more UV inhibition. Models can be used to analyze the sensitivity of water column productivity to UVB and ozone depletion. Assumptions about linearity and time-dependence strongly influence the extrapolation of results. Laboratory measurements suggest that UV inhibition can reach a steady-state consistent with a balance between damage and recovery processes, leading to a non-linear relationship between weighted fluence rate and inhibition. More testing for natural phytoplankton is required, however. The relationship between photoinhibition of photosynthesis and decreases in growth rate is poorly understood, so long-term effects of ozone depletion are hard to predict. However, the wide variety of sensitivities between species suggests that some changes in species composition are likely. Predicted effects of ozone depletion on marine photosynthesis cannot be equated to changes in carbon flux between the atmosphere and ocean. Nonetheless, properly designed studies on the effects of UVB can help identify which physiological and ecological processes are most likely to dominate the responses of marine ecosystems to ozone depletion.
A mat-forming cyanobacterium (Phormidium murayi West and West) isolated from an ice-shelf pond in Antarctica was grown under white light combined with a range of UVA and UVB irradiance. The 4-day growth rate decreased under increasing ultraviolet (UV) radiation, with a ninefold greater response to UVB relative to UVA. In vivo absorbance spectra showed that UVA and to a greater extent UVB caused a decrease in phycocyanin/chlorophyll a and an increase in carotenoids/chlorophyll a. The phycocyanin/chlorophyll a ratio was closely and positively correlated to the UVB-inhibited growth rate. Under fixed spectral gradients of UV radiation, the growth inhibition effect was dominated by UVB. However, at specific UVB irradiances the inhibition of growth depended on the ratio of UVB to UVA, and growth rates increased linearly with increasing UVA. These results are consistent with the view that UVB inhibition represents the balance between damage and repair processes that are each controlled by separate wavebands. They also underscore the need to consider UV spectral balance in laboratory and field assays of UVB toxicity. 49 refs., 6 figs.
Three marine diatom species (Cyclotella sp., Nitzschia closterium and Thalassiosira nordenskioldii) were exposed to a range of daily doses of ultraviolet B radiation (UVBR: 280-320 nm). The lowest UVBR treatments (<2000 J m(-2) d(-1), DNA weighted biologically effective dose, normalised at 300 nm: daily BED(DNA 300 nm) resulted in decreased division rates, volume enlargement and elevated cellular protein and pigment content levels. The highest UVBR treatments (between 2000 and 3800 J m(-2) d(-1) daily BED(DNA 300 nm)) resulted in complete growth inhibition, accompanied by only minor changes in protein, pigments and cell volume. Recovery of cell division after UVBR exposure was decreasingly successful with increasing UVBR dose rates. Ultrastructural examination of exposed Cyclotella cells indicated that high UVBR levels induced plasmolysis and disorientation of cell organelles. Lower levels (<2000 J m(-2) d(-1) daily BED(DNA 300 nm)) seemed to cause an increase in volume and the amount of chloroplasts. The results support the notion conceived earlier that UVBR causes DNA damage, an arrest in the S or G2 phase of the cell cycle, and consequently growth without cell division.
An investigation of the diurnal variation in productivity and contribution to production of populations of autotrophic picoplankton (0.2-2.0 μm), nanoplankton (>2 <20 μm) and microplankton (>20 μm) was carried out at monthly intervals, from May to October 1989, in Llyn Padarn a mesotrophic upland lake in North Wales. Maximum rates and contributions to production of the lake by autotrophic picoplankton occurred during mid-late summer, with the highest average daily contribution from picoplankton (64%) recorded in September at 4 m depth. Diurnal variation in contributions from picoplankton was pronounced, with greatest input, recorded at the end of the day, during the period of picoplankton dominance in mid-late summer. Maximum contribution from picoplantkon (86% of total, 9.2 mg C m-3 h-1) was recorded in September. Nanoplankton primary production was of greatest significance in June and July, although levels were lower than for picoplankton in subsequent months. Contributions via nanoplankton increased with depth in the lake at this time, reaching a maximum of 78% of the total at the end of the day at 9 m depth in early July. At this time, diurnal variation in contributions via nanoplankton was considerable, with maximum photosynthesis generally at the end of the photoperiod at depths of 4 and 9 m. Microplankton made the greatest impact on primary production during the mixed water conditions of spring and autumn, and at these times did variation in production was less than those of both pico and nanoplankton during summer thermal stratification. Photosynthetic capacity was lower for picoplankton than for nanoplankton and microplankton; the highest values were 5, 33 and 51 mg C (mg chl a)-1) h-1) for pico-, nano- and microplankton, respectively. The photosynthetic efficiency of all three size categories of phytoplankton increased with depth. Maximum values were similar for all phytoplankton groups, between 75 and 131 mg C (mg chl a)-1) E-1) m2 but mean levels of photosynthetic efficiency for the 6 months were lower for picoplankton than for nano- or microplankton. Rates of carbon fixation per cell for picoplankton spanned three orders of magnitude, varied considerably diurnally and reached maximum values of 484 fg C(cell)-1) h-1) in the afternoon in near-surface waters in the early stages of exponential population growth in July. During the population maximum of picoplankton in August and September, maximum daily values of carbon fixation per cell, assimilation number and photosynthetic efficiency were all recorded at the end of the day. The seasonal and diurnal patterns of production of the three size categories of planktonic algae in Llyn Padarn were distinct. During spring, microplankton (mainly diatoms) were the dominant primary producers. As thermal stratification developed, nanoplankton were the major contributors to phytoplanktonic production, particularly in the deeper regions of the euphotic zone. Picoplankton made the greatest contribution to production in August and September, exhibiting maximum input towards the end of the light cycle. Diatoms became the major photosynthetic plankton in the mixed water conditions prevalent in Uyn Padarn in October.
The effect of ultraviolet A (UVA) on growth and photosynthetic rate was studied in diatoms (Melosira spp.) of the phytoplankton of a eutrophic lake and a cultured green alga Chloretla ellipsoidea. The cells were incubated under photosynthetically active radiation (PAR) (−UVA) or PAR + UVA conditions (+UVA). Growth of
C.ellipsoidea was retarded under +UVA, as shown by an increase in the lag period, but the rate of exponential growth was almost the same
in + and −UVA conditions. The photosynthetic rate was depressed markedly by UVA in Chlorella cells grown under −UVA. In contrast, cells grown in +UVA showed only slight inhibition by UVA and after exposure to UVA for
6 days there was no inhibition. During the growth experiment, the cellular chlorophyll a content was higher in +UVA than +UVA grown cells. A similar effect was observed in diatoms from the eutrophic Lake Suwa.
In vivo fluorescence with (Fa) and without 3-(3,4-dichloropheny)-l,l-dimethyl urea (DCMU) (Fb) and the photosynthetic rate were measured for C.ellipsoidea and the diatoms for 5 h under + and −UVA conditions. Soon after C.ellipsoidea had been subjected to +UVA, Fb and Fa / Fb decreased quickly and reached minima after 40 min and 1 h, respectively. The suppressed in vivo fluorescence resumed and full recovery was achieved after 4 h. This suggests that reactivation of the photosystem is acquired
under prolonged exposure to UVA. A similar shift of Fa + Fb, but no change in Fb, was found in diatoms by exposure to UVA. Changes in photosynthetic oxygen evolution by C.ellipsoidea under +UVA were similar to changes in Fa + Fb. Degradation of chlorophyll a extracted in methanol was enhanced by UVA. The rate of degradation by UVA was independent of temperature from 15 to 34°C,
suggesting a photochemical reaction. The results indicate that C.ellipsoidea and Melosira spp. acclimatize to prolonged UVA exposure by reactivation of the photosystem and enhanced cellular chlorophyll a synthesis. The ecological importance of these results to phytoplankton productivity in natural aquatic environments is discussed.
Acidification and bubbling was found superior to membrane-filtration for post-incubation treatment of 14C-productivity samples. The method eliminates errors associated with filtration. Results are compared with those of conventional and corrected filtration procedures, and application of the method is discussed.
The importance of algae, both as a contribution to the understanding of living things and in practical terms, hardly needs stressing today. Despite the previous emphasis on photosynthesis research in land plants there is now a large corpus of work on algae. This chapter intends to bring much of the dispersed literature together, so as to achieve an integrated framework from which conclusions can be drawn to further stimulate research. Organisms from the borderline of groups loosely called prokaryotes, plants, and animals have been discussed along with how the majority of algae are influenced by the light climate properties. The structure and function of the photosynthetic membrane have been described. Various kinds and levels of light harvesting available to algae are reviewed briefly. A more detailed analysis of some biochemical and biophysical aspects of light harvesting are also given. Light is essential to all photosynthetic autotrophs. But it is only to the extent that light is limiting to growth that light-harvesting strategies become important. It is therefore necessary to consider under what conditions light does become limiting for algal growth. Strategies of light harvesting are discussed in terms of general ecological, taxonomic, morphological, and cytological aspects. The chapter looks into photosynthetic pigments, reaction centre complexes, and pigment protein (light-harvesting) complexes with details of the principles of light harvesting in light of quantum chemistry and transfer of excitation energy, structure and function, distribution of excitation energy between the photosystems, and interaction of the light-harvesting apparatus with other photosynthetic processes.
Allometric relations between physiological processes and cell volume and surface area are combined with the variable-internal-stores model of growth to predict the ability of hypothetical phytoplankton to compete for phosphorus at equilibrium. The analysis shows that for spherical cells, smaller cells are better competitors than large ones. For cells that are very elongated in shape, however, large cells are often better competitors than small ones. The cells predicted to be the best competitors compare favorably in size and shape with the species observed to dominate in phosphorus-limited chemostats at equilibrium.
ABSTRACTA mat-forming cyanobacterium (Phormidium mur-rayi West and West) isolated from an ice-shelf pond in Antarctica was grown under white light combined with a range of UVA and UVB irradiances. The 4-day growth rate decreased under increasing ultraviolet (UV) radiation, with a ninefold greater response to UVB relative to UVA. In vivo absorbance spectra showed that UVA and to a greater extent UVB caused a decrease in phycocyanin/ chlorophyll a and an increase in carotenoids/chlorophyll a. The phycocyanin/chlorophyll a ratio was closely and positively correlated to the UVB-inhibited growth rate. Under fixed spectral gradients of UV radiation, the growth inhibition effect was dominated by UVB. However, at specific UVB irradiances the inhibition of growth depended on the ratio of UVB to UVA, and growth rates increased linearly with increasing UVA. These results are consistent with the view that UVB inhibition represents the balance between damage and repair processes that are each controlled by separate wavebands. They also underscore the need to consider UV spectral balance in laboratory and field assays of UVB toxicity.
1. Lake Titicaca is a large, high altitude (3810 m a.s.l.) tropical lake (16°S, 68°W) that lies on the border of Bolivia and Perú, receiving high fluxes of ultraviolet radiation (UVR) throughout the year. Our studies were conducted during September of 1997 with the main objective of studying the impact of solar UVR upon phytoplankton photosynthesis.
2. Water samples were taken daily and incubated in situ (down to 14 m depth) under three radiation treatments to study the relative responses to PAR (Photosynthetic Available Radiation, 400–700 nm), UV-A (320–400 nm), and UV-B (280–320 nm) radiation.
3. Photosynthetic inhibition by UVR in surface waters was about 80%, with UV-A accounting for 60% and UV-B for 20%; the inhibition by high levels of PAR was less than 20%. The inhibition due to UVR decreased with depth so that there were no significant differences between treatments at 8.5 m depth.
4. The amount of inhibition per unit energy received by phytoplankton indicates that even though there was a significant inhibition of photosynthesis due to UVR, species in Lake Titicaca seem to be better adapted than species in high latitude environments.
5. The cellular concentration of UV-absorbing compounds, a possible mechanism of photoadaptation, was low in phytoplanktonic species. However, they were abundant in zooplankton, suggesting a high rate of bioaccumulation through the diet.
The effect of UV-B radiation on growth of marine phytoplankton was investigated in relation to DNA damage induced by a range of biologically effective doses (BEDs). Emiliania huxleyi (Prymnesiophyceae) was chosen as a model organism of the ocean's phytoplankton because of its importance in global biogeochemical cycling of carbon and sulphur, elements that influence the world's climate as components of the trace gases carbon dioxide (CO2) and dimethylsulfide (DMS). A marine diatom, Cyclotella, was studied for its capacity to repair the DNA damage, quantified as thymine dimers by the application of a monoclonal antibody against these photoproducts. DNA repair was shown to be complete after just a few hours of exposure to visible light; the repair rate increased with PAR intensity. E. huxleyi appeared to be most sensitive to UV-B radiation: growth was already affected above a dose of 100 J m-2 d-1 (biologically effective radiation, weighted with Setlow's DNA action spectrum), probably through effects on the cell cycle related to damage to nuclear DNA: mean specific growth rates were inversely correlated with thymine dimer contents in cells. Near the ocean's surface UV-B radiation conditions that induce the changes observed by us in cultures can be expected during the growing season of phytoplankton, not only in the tropics but also at higher latitudes. Nevertheles, blooms of species such as E. huxleyi are often excessive in the field. It is suggested that exposure duration of cells near the surface of the ocean can be shorter than our artificial 3 h in the laboratory due to vertical mixing, a phenomenon that is typical for the ocean's upper 50–100 m. When mixing reaches depths greater than the layer where most UV-B is attenuated, negative effects on cells through UV-A-induced inhibition of photosynthesis may prevail over DNA damage, the action spectrum of which has been shown to be limited to the UV-B part of the spectrum. Moreover, the radiation wavelengths that induce DNA damage repair (UV-A and visible) are attenuated vertically much less than UV-B. The photobiological situation in the upper ocean is much more complicated than on land, and effects of UV radiation on plankton biota can only be modelled realistically here when both the spectrally differential attenuation in the UV and visual part of the spectrum and the rate of vertical mixing are taken into account. Action spectra of both damage and repair of DNA and of photosynthesis inhibition of representative microalgal species are the second conditio sine qua non if we want to predict the effect of stratospheric ozone depletion on marine phytoplankton performance.
Dynamic aspects of algal photosynthesis are set against the background of physical water motions which change the light experienced by the phytoplankton. These time-dependent photosynthetic responses are reviewed in relation to the proposition that phytoplankton primary production may be incorrectly estimated by the commonly used static incubation of light and dark bottles for periods significantly longer than the response-time of phytoplankton to changing light. This proposition is supported by the clear overlap between the timescales which characterize water motions and the timescales reported for the complex responses of algae to changing light. Empirical studies comparing static and dynamic incubations have been inconclusive, as have models incorporating some representation of the dynamic photosynthetic response to changing light. These results reflect weaknesses in the simple formulations used to describe photosynthesis in relation to irradiance, the simplicity of physical schemes used to generate changes in irradiance with time, and a lack of data (field and laboratory) on dynamic responses of microalgae to changing light. The quantitative significance of many physiological mechanisms is not known in relation to their effect on photosynthesis.
The effect of ultraviolet radiation on diel changes and depth profiles of phytoplankton photosynthesis was studied in four
temperate freshwater lakes. Photosynthetic oxygen production was determined by incubating lake water in light and dark bottles
under various weather conditions. Half the light bottles were wrapped with sheets of vinyl chloride film to exclude light
with wavelengths shorter than 400 nm. The inhibition of photosynthesis due to UV-A (320–400 nm) was observed during most of
the daytime and was very strong around noon on both sunny and cloudy days. On sunny days, when the surface waters of the highly
eutrophic Lake Suwa and Senzoku Pond were dominated by denseMicrocystis populations, cumulative daily production at the surface, estimated from the incubation of bottles from which UV-A was excluded
by the vinyl film, were about double the rates obtained from glass bottles in which UV-A was present. The UV-A inhibition
was detected from the surface toca 20 cm depth in hypereutrophic lakes and at depths greater than 50 cm in mesotrophic lakes. Analysis of the photosynthesis-irradiance
(P-I) relationship obtained in the present study shows β, a parameter that describes photo-inhibition, is higher in the presence
of UV-A than in its absence. This indicates that UV-A is the major cause of photo-inhibition of phytoplankton photosynthesis.
Both in situ primary production and biomass (chlorophyll α) of fractionated phytoplankton (<64,μ, <25 μm and < 10 μm) were studied in 10 Canadian Shield lakes to elucidate the spatial and temporal variability of the contribution of size fractions to the biomass and primary production of the phytoplankton community. Mean summer biomass and production of each size fraction varied significantly between lakes. Within lakes, temporal variation was low for biomass but great for production. However, temporal variation can be considered of minor importance during the sampling period, as compared to the spatial variation between lakes. Algae from the < 10 μm size fraction were the most important in biomass (41-65 %) and production (23-69%). The temporal trends for both phytoplankton variables thus generally followed closely that of the < 10 μm size fraction. Among the physical, chemical and morphometric variables of the studied lakes, water transparency (Secchi disk), total phosphorus, lake volume, lake area, and mean depth gave the best correlations with phytoplankton variables.
Analysis of data in the literature relating to microalgal adaptations to different photon flux densities indicates that different algal classes have significantly different light requirements for growth and photosynthesis. Although there is some variability within each class, dinoflagellates and blue-green algae generally photosynthesize and grow best at low photon flux densities. Diatoms also tend to be able to grow at very low photon flux densities (growth for some species has been reported at less than 1 μE m−1 s−2). Comparison of the photon flux densities at which photoinhibition occurs in dainoflagellates and diatoms suggests that the former often experience photoinhibition at comparatively low irradiances. In contrast, diatoms often can tolerate relatively high light environments. This tolerance of a large absolute range of photon flux densities may, in part, explain why diatoms are often associated with spring blooms. Green algae
In principle, allometric relationships for algal growth can be applied to biomass size spectra to yield estimates of primary productivity. In practice, reported values of the scaling exponent of algal growth are variable, perhaps reflecting differences in the expression of cell size or phyletic differences or small sample size. The present study established the relationship between algal growth and size with a larger set of literature data than has been used previously, and assessed the effects of expression of cell size and of gross taxonomic differences on that relationship. I was able to collect a data set consisting of 127 observations of daily growth rate and cell size from three algal divisions (Chlorophyta, Chrysophyta, Pyrrophyta) and five classes (Bacillariophyceae, Chlorophyceae, Chrysophyceae, Dinophyceae and Prymnesiophyceae). Growth rate (μ, in divisions day−1) varies with cell carbon content (pg C cell−1) as μ = 3.45C−0.21. The size effect (as reflected by the exponent) is smaller if algal size is expressed as cell volume, reflecting changes in cell composition with size. The exponent is not affected by taxonomic affiliation, but growth rates of Pyrrophyta and Dinophyceae (a class within Pyrrophyta) were significantly lower than those of other divisions and classes. However, pyrrophytes have such a small size range in this data set that no meaningful growth-size relationship can be developed for that group alone.
Data from three cruises (Arabesque 1 and 2 cruises in the Arabian Sea and the Vancouver Island cruise) were examined to assess the importance of species composition and accessory pigments in modifying specific absorption coefficients. The three cruises differed widely in their phytoplankton assemblages with small cells dominating the Arabesque 2 cruise and large diatoms the Vancouver Island cruise. Absorption spectra from each cruise were decomposed into 13 Gaussian bands representing absorption by the major chlorophylls and accessory pigments. The maximum specific peak height $${P}_{m}^{*}$$ for each Gaussian band was obtained by regressing Gaussian peak heights against the concentration of the pigment responsible for the absorption band. This relationship was generally non-linear and was fitted with a rectangular hyperbolic function. Changes in the maximum specific peak heights between cruises reflect changes in the packaging effect, which were most apparent at Gaussian bands of high absorption (400–490 nm), but were close to zero at the Gaussian band centered around 623 nm, associated with chlorophyll a (Chl a). The maximum specific peak height of this Gaussian band, $${P}_{m}^{*}$$ (623), may be used to obtain reliable estimates of Chl a for any phytoplankton assemblage, unaffected by variations caused by the package effect. Comparing the Arabesque 2 peak heights with the Vancouver data, an apparent flattening effect of 0.42 at 440 nm and 0.62 at 676 nm was found for the Vancouver data relative to the Arabesque 2 data (assuming a zero flattening effect for the latter). Multiple linear regression analysis suggested that 29–42% of the variability in the specific absorption coefficient of phytoplankton at 440 nm was due to changes in pigment composition, while the remaining 58–71% was due to changes in the package effect. An inverse relationship was found between the proportion of non-photosynthetic pigments (NPC) and ambient Chl a concentration, suggesting that small cells (generally found in oligotrophic waters) had higher proportions of photoprotective pigments.
The impact of u.v.-A (315–400 nm) on phytoplanktonic C-assimilation has been studied in situ and in the laboratory under artificial light. Water samples from Lake Lucerne were placed in DURAN-glass bottles and incubated either covered or uncovered with u.v. absorbing transparent tubes. Exposure to u.v.-A clearly inhibited 14C-assimilation in the uncovered samples both in situ and in the laboratory. Variations in visible light intensity and filtering of u.v.-B selectively demonstrated small inhibition of 14C-assimilation. U.v.-A inhibition of productivity is the major factor in the well known depression in productivity for surface waters.
Vergleichende Untersuchungen zur Primärproduktion im Neusiedlersee. O2, 14 C und Experimente mit künstlicher Zirkulation
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Changes in the lipophilic photosynthetic pigment contents of different Microcystis aeruginosa strains in response to growth irradiance
- P Woitke
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Woitke, P., K. Hesse and J.-G. Kohl, 1997. Changes in the lipophilic photosynthetic pigment contents of different Microcystis aeruginosa strains in response to growth irradiance. Photosynthetica 33 (3-4): 443-453.
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