Optical properties and optical constituents of the Faroe Islands shelf and off-shelf waters,North East Atlantic

The study comprises a data set of CTD, optical properties—K ₀(PAR), c _p, a(PAR), b(PAR)—and optical constituents—Chl a, SPM, CDOM—from 72 shelf and off-shelf stations in the Faroe Islands (62°N, 7°W) North East Atlantic, in early spring 2005. Results showed that shelf waters surrounding the islands were cold and low saline, whereas off-shelf waters were warmer (~1°C) and more saline (~0.05) PSU. A pronounced oceanographic front separated the two waters, and diffuse light attenuation K ₀(PAR), beam attenuation c _p, Chl a, absorption a(PAR), and scattering coefficient b(PAR) were all significantly higher on the shelf. Analyses showed that off-shelf light attenuation K ₀(PAR) was governed by Chl a, shown by a high (r ² = 0.64) Chl a–K ₀(PAR) correlation, whereas light attenuation on the shelf was governed by both Chl a, SPM, and CDOM in combination. A Chl a specific diffuse attenuation coefficient K₀^* ( \textPAR ) K_{0}^{*} \left( {\text{PAR}} \right) of 0.056 (m² mg⁻¹ Chl a) and a Chl a specific beam attenuation ( c_\textp^* c_{\text{p}}^{*} ) of 0.27 (m² mg⁻¹ Chl a) coefficients were derived for the off-shelf. It is pointed out that Chl a is the single variable that changes over time as no rivers with high SPM and CDOM enter the shelf area. Data were obtained in early spring, and Chl a concentrations were low ~0.5 mg Chl a m⁻³. Spring bloom Chl a are about 10 mg Chl a m⁻³ and estimations showed that shelf K ₀(PAR) will increase about 5 times and beam attenuation about 10 times. The Faroe Islands shelf–off-shelf waters is a clear example where physical conditions maintain some clear differences in optical properties and optical constituents. The complete data set is enclosed.     

Development of optical criteria to discriminate various types of highly turbid lake waters

Our aim was to refine the optical classification of turbid waters in order to improve the performance of water color algorithms. Bio-optical measurements and sampling of optically active substances were performed in highly turbid lakes Taihu, Chaohu, and Dianchi, and in Three Gorges reservoir in China. Based on strong correlations between trough depths of remote sensing reflectance (R _rs(λ)) near 680 nm (denoted as TD680) and the ratios of inorganic suspended matter (ISM) to total suspended matter (TSM) concentrations, an empirical model was developed for water classification. In the 400–900 nm spectral range, different correlations between R _rs(λ), TSM and chlorophyll a (Chla) concentrations indicate discrepancies among the following ISM/TSM ranges: ISM/TSM ≤ 0.5, 0.5 < ISM/TSM < 0.8, and ISM/TSM ≥ 0.8. Corresponding findings support an important conclusion that only high ISM/TSM ratios, usually above 0.5, and using the more sensitive and stable near infrared spectral range (730–820 nm), can assure good performances of the TSM remote sensing algorithms. Meanwhile, the particulate absorption a _p(λ) and scattering b _p(λ) were strongly influenced by different ranges of ISM/TSM ratios. Typically the a _p(675) peaks became more and more vague as ISM/TSM increased, and the b _p(λ) values first decreased and then increased with a marked inflexion at ISM/TSM ≈ 0.5. The TD680 threshold values were derived to discriminate three types of turbid waters, i.e., Type 1 (TD680 ≥ 0.0082 sr⁻¹), Type 2 (0.0082 sr⁻¹ > TD680 > 0 sr⁻¹), and Type 3 (TD680 ≤ 0 sr⁻¹). This study provides a promising tool for identifying various types of highly turbid waters, and is significant for the development of class-based algorithms of water color remote sensing.     

Phytoplankton and primary production in clear-vegetated,inorganic-turbid,and algal-turbid shallow lakes from the pampa plain (Argentina)

Shallow lakes often alternate between two possible states: one clear with submerged macrophytes, and another one turbid, dominated by phytoplankton. A third type of shallow lakes, the inorganic turbid, result from high contents of suspended inorganic material, and is characterized by low phytoplankton biomass and macrophytes absence. In our survey, the structure and photosynthetic properties (based on ¹⁴C method) of phytoplankton were related to environmental conditions in these three types of lakes in the Pampa Plain. The underwater light climate was characterized. Clear-vegetated lakes were more transparent (K _d 4.5–7.7 m⁻¹), had high DOC concentrations (>45 mg l⁻¹), low phytoplankton Chl a (1.6–2.7 μg l⁻¹) dominated by nanoflagellates. Phytoplankton productivity and photosynthetic efficiency (α ~ 0.03 mgC mgChla ⁻¹ h⁻¹ W⁻¹ m²) were relatively low. Inorganic-turbid lakes showed highest K _d values (59.8–61.4 m⁻¹), lowest phytoplankton densities (dominated by Bacillariophyta), and Chl a ranged from 14.6 to 18.3 μg l⁻¹. Phytoplankton-turbid lakes showed, in general, high K _d (4.9–58.5 m⁻¹) due to their high phytoplankton abundances. These lakes exhibited the highest Chl a values (14.2–125.7 μg l⁻¹), and the highest productivities and efficiencies (maximum 0.56 mgC mgChla ⁻¹ h⁻¹ W⁻¹ m²). Autotrophic picoplankton abundance, dominated by ficocianine-rich picocyanobacteria, differed among the shallow lakes independently of their type (0.086 × 10⁵–41.7 × 10⁵ cells ml⁻¹). This article provides a complete characterization of phytoplankton structure (all size fractions), and primary production of the three types of lakes from the Pampa Plain, one of the richest areas in shallow lakes from South America. Handling editor: J. Padisak     

Estimation of periphytic microalgae gross primary production with DCMU-fluorescence method in Yenisei River (Siberia, Russia)

Periphyton (epilithon) gross primary production (GPP) was estimated using the DCMU-fluorescence method in the Yenisei River. In the unshaded littoral zone, chlorophyll a concentration (Chl a) and GPP value varied from 0.83 to 973.74 mg m⁻²and 2–304,425 O₂ m⁻² day⁻¹ (0.64–95 133 mg C m⁻² day⁻¹), respectively. Positive significant correlation (r = 0.8) between daily GPP and periphyton Chl a was found. Average ratio GPP:Chl a for periphyton was 36.36 mg C mg Chl a m⁻² day⁻¹. The obtained GPP values for the Yenisei River have a high significant correlation with values predicted by a conventional empirical model for stream periphyton. We concluded that the DCMU-fluorescence method can be successfully used for measuring of gross primary production of stream phytoperiphyton at least as another useful tool for such studies.     

The specific inherent optical properties of three sub-tropical and tropical water reservoirs in Queensland, Australia

The underwater light climate, which is a major influence on the ecology of aquatic systems, is affected by the absorption and scattering processes that take place within the water column. Knowledge of the specific inherent optical properties (SIOPs) of water quality parameters and their spatial variation is essential for the modelling of underwater light fields and remote sensing applications. We measured the SIOPs and water quality parameter concentrations of three large inland water impoundments in Queensland, Australia. The measurements ranged from 0.9 to 42.7 μg l⁻¹ for chlorophyll a concentration, 0.9–170.4 mg l⁻¹ for tripton concentration, 0.36–1.59 m⁻¹ for a _CDOM(440) and 0.15–2.5 m for Secchi depth. The SIOP measurements showed that there is sufficient intra-impoundment variation in the specific absorption and specific scattering of phytoplankton and tripton to require a well distributed network of measurement stations to fully characterise the SIOPs of the optical water quality parameters. While significantly different SIOP sets were measured for each of the study sites the measurements were consistent with published values in other inland waters. The multiple measurement stations were allocated into optical domains as a necessary step to parameterise a semi-analytical inversion remote sensing algorithm. This article also addresses the paucity of published global inland water SIOP sets by contributing Australian SIOP sets to allow international and national comparison.     

Distribution of microphytobenthic biomass in Martel Inlet,King George Island (Antarctica)

The spatial and temporal variation of microphytobenthic biomass in the nearshore zone of Martel Inlet (King George Island, Antarctica) was estimated at several sites and depths (10–60 m), during three summer periods (1996/1997, 1997/1998, 2004/2005). The mean values were inversely related to the bathymetric gradient: higher ones at 10–20 m depth (136.2 ± 112.5 mg Chl a m⁻², 261.7 ± 455.9 mg Phaeo m⁻²), intermediate at 20–30 m (55.6 ± 39.5 mg Chl a m⁻², 108.8 ± 73.0 mg Phaeo m⁻²) and lower ones at 40–60 m (22.7 ± 23.7 mg Chl a m⁻², 58.3 ± 38.9 mg Phaeo m⁻²). There was also a reduction in the Chl a/Phaeo ratio with depth, from 3.2 ± 3.2 (10–20 m) to 0.7 ± 1.0 (40–60 m), showing a higher contribution of senescent phytoplankton and/or macroalgae debris at the deeper sites and the limited light flux reaching the bottom. Horizontal differences found in the biomass throughout the inlet could not be clearly related to hydrodynamics or proximity to glaciers, but with sediment characteristics. An inter-summer variation was observed: the first summer presented the highest microphytobenthic biomass apparently related to more hydrodynamic conditions, which causes the deposition of allochthonous material.     

The Status and Characteristics of Eutrophication in the Yangtze River (Changjiang) Estuary and the Adjacent East China Sea, China

Eutrophication has become increasingly serious and noxious algal blooms have been of more frequent occurrence in the Yangtze River Estuary and in the adjacent East China Sea. In 2003 and 2004, four cruises were undertaken in three zones in the estuary and in the adjacent sea to investigate nitrate (NO₃–N), ammonium (NH₄–N), nitrite (NO₂–N), soluble reactive phosphorus (SRP), dissolved reactive silica (DRSi), dissolved oxygen (DO), phytoplankton chlorophyll a (Chl a) and suspended particulate matter (SPM). The highest concentrations of DIN (NO₃–N+NH₄–N+NO₂–N), SRP and DRSi were 131.6, 1.2 and 155.6 μM, respectively. The maximum Chl a concentration was 19.5 mg m⁻³ in spring. An analysis of historical and recent data revealed that in the last 40 years, nitrate and SRP concentrations increased from 11 to 97 μM and from 0.4 to 0.95 μM, respectively. From 1963 to 2004, N:P ratios also increased from 30–40 up to 150. In parallel with the N and P enrichment, a significant increase of Chl a was detected, Chl a maximum being 20 mg m⁻³, nearly four times higher than in the 1980s. In 2004, the mean DO concentration in bottom waters was 4.35 mg l⁻¹, much lower than in the 1980s. In comparison with other estuaries, the Yangtze River Estuary was characterized by high DIN and DRSi concentrations, with low SRP concentrations. Despite the higher nutrient concentrations, Chl a concentrations were lower in the inner estuary (Zones 1 and 2) than in the adjacent sea (Zone 3). Based on nutrient availability, SPM and hydrodynamics, we assumed that in Zones 1 and 2 phytoplankton growth was suppressed by high turbidity, large tidal amplitude and short residence time. Furthermore, in Zone 3 water stratification was also an important factor that resulted in a greater phytoplankton biomass and lower DO concentrations. Due to hydrodynamics and turbidity, the open sea was unexpectedly more sensitive to nutrient enrichment and related eutrophication processes.     

Copepod community structure and abundance in a tropical mangrove estuary,with comparisons to coastal waters

Zooplankton, sampled at five stations from the upper Sangga estuary (7 km upstream) in Matang Mangrove Forest Reserve (MMFR), Malaysia, to 16 km offshore, comprised more than 47% copepod. Copepod abundance was highest at nearshore waters (20,311 ind m⁻³), but decreased toward both upstream (15,572 ind m⁻³) and offshore waters (12,330 ind m⁻³). Copepod abundance was also higher during the wetter NE monsoon period as compared to the drier SW monsoon period, but vice versa for copepod species diversity. Redundancy analysis (RDA) shows that copepod community structure in the upper estuary, nearshore and offshore waters differed, being influenced by spatial and seasonal variations in environmental conditions. The copepods could generally be grouped into estuarine species (dominantly Acartia spinicauda Mori, Acartia sp1, Oithona aruensis Früchtl, and Oithona dissimilis Lindberg), stenohaline species (Acartia erythraea Giesbrecht, Acrocalanus gibber Giesbrecht, Paracalanus aculateus Giesbrecht, and Corycaeus andrewsi Farran) and euryhaline species (Parvocalanus crassirostris Dahl, Oithona simplex Farran, and Bestiolina similis (Sewell)). Shifts in copepod community structure due to monsoonal effects on water parameters occurred at the lower estuary. Copepod peak abundance in mangrove waters could be associated with the peak chlorophyll a concentration prior to it. Evidence of copepod consumption by many species of young fish and shrimp larvae in the MMFR estuary implies the considerable impact of phytoplankton and microphytobenthos on mangrove trophodynamics.     

Relevance of bacterioplankton abundance and production in the oligotrophic equatorial Indian Ocean

Bacterioplankton abundance and production, chlorophyll a (Chl a) concentrations and primary production (PP) were measured from the equatorial Indian Ocean (EIO) during northeast (NEM), southwest (SWM) and spring intermonsoon (SpIM) seasons from 1°N to 5°S along 83°E. The average bacterial abundance was 0.52 ± 0.29, 0.62 ± 0.33 and 0.46 ± 0.19 (× 10⁸ cells l⁻¹), respectively during NEM, SWM and SpIM in the top 100 m. In the deep waters (200 m and below), the bacterial counts averaged ∼0.35 ± 0.14 × 10⁸ cells l⁻¹ in SWM and 0.39 ± 0.16 × 10⁸ cells l⁻¹ in SpIM. The 0–120 m column integrated bacterial production (BP) ranged from 19 to 115 and from 10 to 51 mg C m⁻² d⁻¹ during NEM and SWM, respectively. Compared with many open ocean locations, bacterial abundance and production in this region are lower. The bacterial carbon production, however, is notably higher than that of phytoplankton PP (BP:PP ratio 102% in SWM and 188% in NEM). With perpetually low PP (NEM: 20, SWM: 18 and SpIM: 12 mg C m⁻² d⁻¹) and Chl a concentration (NEM: 16.5, SWM: 15.0 and SpIM: 20.9 mg m⁻²), the observed bacterial abundance and production are pivotal in the trophodynamics of the EIO. Efficient assimilation and mineralization of available organics by bacteria in the euphotic zone might serve a dual role in the ultra-oligotrophic regions including EIO. Thus, bacteria probably sustain microheterotrophs (micro- and meso-zooplankton) through microbial loop. Further, rapid mineralization by bacteria will make essential nutrients available to autotrophs.     

Uptake of picophytoplankton,bacterioplankton and virioplankton by a fringing coral reef community (Ningaloo Reef,Australia)

We examined the importance of picoplankton and virioplankton to reef trophodynamics at Ningaloo Reef, (north-western Australia), in May and November 2008. Picophytoplankton (Prochlorococcus, Synechococcus and picoeukaryotes), bacterioplankton (inclusive of bacteria and Archaea), virioplankton and chlorophyll a (Chl a) were measured at five stations following the consistent wave-driven unidirectional mean flow path of seawater across the reef and into the lagoon. Prochlorococcus, Synechococcus, picoeukaryotes and bacterioplankton were depleted to similar levels (~40% on average) over the fore reef, reef crest and reef flat (=‘active reef’), with negligible uptake occurring over the sandy bottom lagoon. Depletion of virioplankton also occurred but to more variable levels. Highest uptake rates, m, of picoplankton occurred over the reef crest, while uptake coefficients, S (independent of cell concentration), were similarly scaled over the reef zones, indicating no preferential uptake of any one group. Collectively, picophytoplankton, bacterioplankton and virioplankton accounted for the uptake of 29 mmol C m⁻² day⁻¹, with Synechococcus contributing the highest proportion of the removed C. Picoplankton and virioplankton accounted for 1–5 mmol N m⁻² day⁻¹ of the removed N, with bacterioplankton estimated to be a highly rich source of N. Results indicate the importance of ocean–reef interactions and the dependence of certain reef organisms on picoplanktonic supply for reef-level biogeochemistry processes.     

Microphytobenthos production in the Gulf of Fos, French Mediterranean coast

Microphytobenthic oxygen production was studied in the Gulf of Fos (French Mediterranean coast) during 1991/1992 using transparent and dark benthic chambers. Nine stations were chosen in depths ranging from 0.5 to 13 m, which represents more than 60% of bottoms in the Gulf. Positive net microphytobenthic oxygen production was seasonally detected down to 13 m; the maximum value attained was 60 mg O₂ m⁻² h⁻¹ (0.7–0.8 g O₂ m⁻² d⁻¹) in sediments at 0.5 m depth during spring and winter. Respiration rates were maximum in the sediments located at the mussel farm (5 m), in the center of the Gulf, with 135 mg O₂ m⁻² h⁻¹ in spring (3.2 g O₂ m⁻² d⁻¹); in the other locations, it ranged from 3.3 to 58.2 mg O₂ m⁻² h⁻¹ (0.08–1.4 g O₂ m⁻² d⁻¹). Compared to phytoplankton, microphytobenthos production was higher only in the bottoms < 1 m depth. In deeper bottom waters, phytoplankton production could be absent due to light limitation, while microphytobenthos was still productive. Phytoplankton production m⁻² was generally higher than microphytobenthic production. Microphytobenthic biomass, higher than phytoplanktonic, varied from 27 to 379 mg Chl a m⁻², the maximum in the mussel farm sediments, with the minimum in sandy shallow bottoms. Pigment analysis showed that microphytobenthos consisted mainly of diatoms (Chl c and fucoxanthin) but other algal groups containing Chl b could become seasonally important. A Principal Component Analysis suggested that the main statistical factors explaining the distribution of our observations may be interpreted in terms of enrichment in phaeopigments and light; the role of Chl a appearing paradoxically as secondary in benthic production rates. Phaeopigments are mainly constituted by phaeophorbides, which indicate grazing processes. The influence of the mussel farm on the oxygen balance is noticeable in the whole Gulf.     

A comparison of phytoplankton size-fractions in Mondsee,an alpine lake in Austria: distribution,pigment composition and primary production rates

Production rates, abundance, chlorophyll a (Chl a) concentrations and pigment composition were measured for three size classes (<2 μm, 2–11 μm and >11 μm) 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 ([mm² l⁻¹: mm³l⁻¹]), pigment distribution patterns and photosynthetic rates. Particular attention was paid to autotrophic picophytoplankton (APP, fraction <2 μm) 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 × 10³ cells ml⁻¹ in June (at 4–9 m). The minimum (October at 12 m) was more than an order of magnitude lower (4.9 × 10³ ml⁻¹). APP peaked during autumn and contributed between 24% and 42% to the total area-integrated Chl a (10–23 mg m⁻²) and between 16% and 58% to total area-integrated production (5–64 mg m⁻²  h⁻¹) throughout seasons.     

Long-term study of zooplankton in the estuarine system of Ribeira Bay,near a power plant (Rio de Janeiro,Brazil)

The structure of the zooplankton community in an estuary adjacent to the Admiral álvaro Alberto Nuclear Power Plant at Angra dos Reis, state of Rio de Janeiro, Brazil was studied from 2001 through 2005. At that time, the power plant had been operating for 20 years. The results were compared with a previous study in 1991–1993. The zooplankton was sampled 4 times a year, in vertical hauls using a 150 μm net, at two fixed points near the plant’s intake and discharge sites. Temperature, salinity, and chlorophyll a were measured. The water of Ribeira Bay is warm, with salinities typical of Coastal Water and more saline waters. Zooplankton density at the discharge site (Mean: 245,434 ind m⁻³, SD: 335,358 ind m⁻³) was higher than that at the intake site (Mean: 84,634 ind m⁻³, SD: 101,409 ind m⁻³). A total of 121 mesozooplankton taxa were recorded from 2001 to 2005. Copepoda constituted the most common taxon and comprised more than 57% of the total zooplankton, followed by cladocers and gastropod larvae. A seasonal zooplankton cycle was observed only during 2004; in other years, the plankton varied only between years. Overall mesozooplankton abundance at the discharge site was similar to levels reported from the inner zone of this estuary in 1991–1993. Surface temperature was the important factor structuring the zooplankton community at the discharge site. No effect on the mesozooplankton by passage through the condensers could be discerned, and no permanent negative influence on the plankton populations could be detected. Guest editors: U. M. Azeiteiro, I. Jenkinson & M. J. Pereira Plankton Studies     

Optical fractionation of chlorophyll and primary production for coastal waters of the Southern Ocean

Our objective was to quantify the potential variability in remotely sensed chlorophyll a (Chl a) and primary productivity in coastal waters of the Southern Ocean. From data collected throughout the springs/summers of 1991–1994, we calculated the proportion of water column Chl a and primary productivity within the upper optical attenuation length (K ⁻¹ _par) and the satellite-weighted depth. The temporal variability was resolved every 2–3 days and was observed to be greater within years than between years. Three-year averages (n=223) revealed that 10.2 ± 3.6% of total Chl a and 14.8 ± 6.5% of production occurred within satellite-weighted depth in predominantly Case I waters. The average values were twice as high within K ⁻¹ _par, 24.1 ± 8% of total Chl a and 34 ± 9% of production respectively. Masked in these long-term averages are very large changes occurring on short time scales of seasonal blooms. We observed that the patterns of Chl a vertical distribution within blooms are also subject to taxonomic influence and dependent upon the physiological state of the phytoplankton. Highest proportions of water column Chl a in the first optical depth were measured during the rapid onset of surface cryptophyte blooms each year, i.e. 50% within K ⁻¹ _par and 30% above the satellite-weighted depth. Lowest fractions, 6% and 2% of biomass within K ⁻¹ _par and satellite-weighted depth respectively, were associated with peak bloom conditions independent of taxonomy. Our analyses suggest that satellite-dependent models of Chl a and subsequent chlorophyll-dependent primary production will be challenging to develop for the near-shore Southern Ocean, especially given the potentially high natural variability in the vertical distribution of Chl a driven by physical forcing, the photoadaptive abilities of polar phytoplankton, and taxonomic influences. Accepted: 27 August 1999     

The development of antenna complexes of barley (Hordeum vulgare cv. Akcent) under different light conditions as judged from the analysis of 77 K chlorophyll a fluorescence spectra

Using 77 K chlorophyll a (Chl a) fluorescence spectra in vivo, the development was studied of Photosystems II (PS II) and I (PS I) during greening of barley under intermittent light followed by continuous light at low (LI, 50 μmol m⁻² s⁻¹) and high (HI, 1000 μmol m⁻² s⁻¹) irradiances. The greening at HI intermittent light was accompanied with significantly reduced fluorescence intensity from Chl b excitation for both PS II (F685) and PS I (F743), in comparison with LI plants, indicating that assembly of light-harvesting complexes (LHC) of both photosystems was affected to a similar degree. During greening at continuous HI, a slower increase of emission from Chl b excitation in PS II as compared with PS I was observed, indicating a preferred reduction in the accumulation of LHC II. The following characteristics of 77 K Chl a fluorescence spectra documented the photoprotective function of an elevated content of carotenoids in HI leaves: (1) a pronounced suppression of Soret region of excitation spectra (410–450 nm) in comparison with the red region (670–690 nm) during the early stage of greening indicated a strongly reduced excitation energy transfer from carotenoids to the Chl a fluorescing forms within PS I and PS II; (2) changes in the shape of the excitation band of Chl b and carotenoids (460–490 nm) during greening under continuous light confirmed that the energy transfer from carotenoids to Chl a within PS II remained lower as compared with the LI plants. This revised version was published online in June 2006 with corrections to the Cover Date.     

Protein,fatty acid,and pigment content of <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> under different light regimes

The effects of irradiance and photoperiod on growth rates, chlorophyll a, β-carotene, total protein, and fatty acid content of Chlorella vulgaris were determined. The maximum growth rate (1.13 day⁻¹) was at 100 μmol photons m⁻² s⁻¹ and 16:8-h light/dark photoperiod. Chlorophyll a and β-carotene contents significantly differed under different light regimes with chlorophyll a content lower at high irradiance and longer light duration, while β-carotene showed the inverse trend. The total protein and fatty acid content also significantly differed in different light regimes; the maximum percentage of protein (46%) was at 100 μmol photons m⁻² s⁻¹ and 16:8 h photoperiod, and minimum (33%) was at 37.5 μmol photons m⁻² s⁻¹ and 8:16 h photoperiod; the total saturated fatty acids increased, while monounsaturated and polyunsaturated fatty acids decreased with increasing irradiance and light duration.     

Primary production dynamics of dominant hydrophytes in Lake Provala (Serbia)

The objective of this investigation was to analyze the primary production of the dominant hydrophytes by monitoring levels of organic matter and organic carbon and estimating photosynthetic potential via the total chlorophyll content. The survey was conducted in Lake Provala (Serbia) throughout the peak vegetation period of the year 2000. The contents of organic matter and organic carbon for Myriophyllum spicatum L. were 105.11 g m⁻² and 73.66 g m⁻², Nymphoides peltata (Gmel.) Kunt. were 95.51 g m⁻² and 45.26 g m⁻² and Ceratophyllum demersum L. were 52.17 g m⁻² and 29.75 g m⁻². Chlorophyll A (Chl a) and chlorophyll A+B (Chl a+b) pigments ranged from 1.54 mg g⁻¹(Chl a) and 2.1 mg g⁻¹(Chl a+b) in M. spicatum to 5.27 mg g⁻¹(Chl a) and 7.53 mg g⁻¹(Chl a+b) in C. demersum. At full leaf out, the latter aquatic plants exceeded 50% cover of the open water surface. All species achieved maximum growth in June, but significant differences in growth dynamics were observed. At the end of the vegetation period, these plants sink to the bottom and decompose     

Photosystem 2-activity and thylakoid membrane polypeptides of <Emphasis Type="Italic">in vitro</Emphasis> cultured chrysanthemum as affected by NaCl

Long-term (30 d) effects of 100, 200, 300, and 400 mM NaCl on photosystem 2 (PS 2)-mediated electron transport activity and content of D1 protein in the thylakoid membranes of chrysanthemum (Dendranthema grandiflorum) cultured in vitro at low irradiance 20 μmol(photon) m⁻² s⁻¹ were investigated. 100 mM NaCl increased contents of chlorophylls (Chl) a and b, carotenoids (Car; xanthophylls + carotenes), and the ratio of Chl a/b, and Car/Chl a+b. However, further increase in NaCl concentration led to the significant reduction in the contents of Chl a, and Chl b, and increase in the ratio of Chl a/b and Car/Chl a+b. NaCl treatment decreased the PS 2-mediated electron transport activity and contents of various thylakoid membrane polypeptides including D1 protein.