Changes in pH as a measure of photosynthesis by marine macroalgae

An automatically operated method for high precision measurements of steady-state photosynthesis by macroalgae was developed. Changes in pH and oxygen content of seawater passing the algae in a flowthrough system, could be measured with extremely high accuracy over very long periods of time. The method is especially suitable for measurements on flowthrough systems with high rates of water exchanges (i.e. short retention time), and can be used to study exchange processes for marine plants, animals and small ecosystems. Since the same measuring unit is used for several flowthrough chambers, the method is very suitable for comparisons between different species, or between differently pretreated specimens of the same species (e.g. in toxicological studies). The method was used to study the ratio: [oxygen production] to [CO₂+H⁺ uptake] at different light intensities for several macroalgae belonging to different systematic groups and from different habitats. At lower photosynthetic rates this ratio was similar for all of the algae studied (1.17±0.02). For brown algae of the fucacean family, the ratio increased by 0.08 units at higher photosynthetic rates. This increase was thought to be related to the crassulacean acid metabolism (CAM)-like strategies connected to these algae. For all other algae studied, the ratio remained constant or decreased slightly (at most by 0.04 units) at higher photosynthetic rates. The relations between the abovementioned ratio and the photosynthetic quotient are discussed on a theoretical basis.     

Observations on organic carbon utilization by photosynthetic marine microalgae

Organic carbon utilization was studied in 13 species of axenic unicellular marine algae. The compounds tested were 15 sugars, 19 acids, and 16 alcohols. Heterotrophy occurred in only three chlorophyte strains with acetate and ethanol; one strain with glucose. Mixotrophy was observed with the following compounds: glyceraldehyde, 1 species; acetate, 4 species; glycolic acid, 5 species; pyruvic acid, 9 species; caproic acid, 3 species; lactic acid, 1 species; ethanol, 3 species; glycerol, 9 species. Some ecological implications are discussed.     

A flow-through system for field measurements of production by marine macroalgae

A continuous flow-through chamber for the in situ measurement of primary production in macrophytic algae (as exemplified by Ulva lactuca) is described. Rapid mixing occurred within the chamber independent of flow rate or amount of algal tissue, so that the complete-mix reactor model of sanitary engineering was closely approximated. Field experiments with the apparatus revealed a rapid response to short-term variations in production rate as well as a close correlation between production and changing light levels. The flowthrough apparatus was compared to a closed system (the traditional bell jar approach); when the water in the latter was mixed, the two methods gave similar results for incubations not longer than several hours. However, during longer incubations, the productivity in the static system was sometimes depressed, possibly due to nutrient depletion or to abnormally high levels of oxygen. Thus, the flow-through system permits reliable measurements of macroalgal production for periods of 12 h or longer.     

Effects of oxygen and inorganic carbon concentrations on the photosynthetic quotients of marine algae

The photosynthetic quotients of the marine prymnesiophyte Pavlova lutheri and the marine dinoflagellate Glenodinum sp. were measured at different concentrations of dissolved oxygen and inorganic carbon. Dissolved oxygen concentration appeared to be the most important factor controlling the photosynthetic quotient. Photosynthetic quotients generally were between 1.0 and 1.8 at oxygen concentrations less than saturation, were approximately 1.0 at oxygen saturation, and generally were from 0.1 to 1.0 at oxygen concentrations greater than saturation. The photosynthetic quotients greater than 1.0 were not caused by lipid synthesis. They may have been partially caused by the presence of KNO₃ rather than an ammonium salt in the growth media. The lowered photosynthetic quotients at higher oxygen concentrations were probably caused by algal photorespiration.Contribution No. 202 from the Department of Biology, The Pennsylvania State University; 202 Buckhout Laboratory, University Park, Pennsylvania 16802, USA     

Long-term effects of ultraviolet radiation on growth and photosynthetic performance of polar and cold-temperate macroalgae

Long-term effects of artificial ultraviolet radiation (UV) and natural solar radiation on growth and photosynthetic activity, as measured by chlorophyll fluorescence, were investigated in 13 different polar and cold-temperate macroalgal species. Isolates of five different species from the Arctic and Antarctic were exposed to different light treatments of photosynthetically active radiation (PAR), PAR+UVA and PAR+UVA+UVB. Eight different species collected on the island of Helgoland, North Sea, Germany, were studied in the laboratory and under natural solar radiation conditions. Increase in fresh weight and changes in photosynthetic performance were monitored over a period of 3-4 weeks. The sublittoral polar species, particularly the Antarctic red algal species Gymnogongrus antarcticus and G. turquetii, the Arctic cold-temperate brown alga Alaria esculenta and, very drastically, the Arctic-endemic Laminaria solidungula, exhibited strong inhibiting effects of artificial UVB radiation on growth. In the cold-temperate sublittoral growth of the red algae Phycodrys rubens and, to a lesser extend, Membranoptera alata was substantially inhibited by UV radiation. In contrast, eulittoral species, e.g. Fucus serratus, did not show any differences in growth with respect to artificial irradiation conditions, with or without UV radiation. In the laboratory, some individuals of the green alga Codium fragile exhibited strong morphological changes of the whole thallus, particularly under UVB exposure. In the experimental outdoor set up, growth of most of the algal species was already inhibited by the full solar UV waveband, but, apart from Polyides rotundus, no additional UVB effect could be detected. Changes of in vivo fluorescence were not always consistent with the measurable changes in growth rate, indicating that physiological processes leading to an inhibition of growth may act independently of changes in photosynthetic activity. For the polar species, a general correlation between the natural vertical distribution in the field and the individual sensitivity towards UV radiation was indicated, while for eulittoral species from Helgoland no clear relationship was found. The obtained results show that measuring growth is a good ecological parameter to monitor long-term effects of UV radiation on single macroalgal species and the possible resulting changes of whole algal communities in coastal ecosystems.     

Fatty acid composition of marine macroalgae from the Black Sea and Dardanelles

The fatty acid (FA) composition was determined in 14 species of marine macroalgae belonging to the Chlorophyta, Phaeophyta and Rhodophyta, which were collected from ?ile in the Black Sea and Kepez in the Dardanelles. Generally, polyunsaturated FAs and monounsaturated FAs were major components (50–77%). Total saturated FAs ranged from 22% to 50%, with 16?:?0 as the most abundant saturate (32–38%). Two samples of Cystoseira barbata collected from a different station had some differences from each other in their contents of 18?:?2n-6 and 18?:?3n-3 and in the 18?:?2n-6/20?:?4n-6 ratios. Green algal species had a significantly higher proportion of unsaturated FAs and a significantly lower proportion of saturated FAs than the red and brown algae. The amount of n-3 FAs was significantly higher in Ulva rigita, Chaetomorpha linum, Enteromorpha linza and Gracilaria verrucosa (8.88, 6.44, 5.31 and 5.24, respectively).     

Production of biodiesel from macroalgae by supercritical CO2 extraction and thermochemical liquefaction

We compare two different techniques for the extraction of biodiesel from macroalgae: the thermochemical liquefaction and the extraction using supercritical carbon dioxide (sc-CO₂). The first allows to use wet material, while sc-CO₂ requires dry material and uses moderate temperature and pressure so that it can be useful for the extraction of thermolabile compounds which may decompose at the temperature at which thermal methos are carried out. In both cases the extracted oil was characterized quantitatively and qualitatively. The novelty of the work is that in the literature the use of macroalgae for the production of biodiesel has not so far been described, while they are used mainly as food or other purposes.     

Influence of light and temperature on the photosynthetic rate of marine benthic diatoms

The influence of light and temperature on photosynthetic rate as measured by C¹⁴O₂-fixation of marine benthic diatoms was investigated, using both intact sediment samples (Marshall et al., 1973) and suspensions of diatoms harvested by a lenstissue technique (Eaton and Moss, 1966). After C¹⁴-incubation, sediment samples were filtered, burned in a sample oxidizer, and their activity determined in a liquid scintillation counter. Photosynthetic rate of mixed field populations is saturated by a light intensity of approximately 10,000 lux; at still higher light intensities no photoinhibition was found. In contrast to the mixed field populations, unialgal cultures of the benthic diatom Amphiprora alata Kütz. exhibited strong photoinhibition at higher light intensities (10,000 to 60,000 lux). Within a range of 4° to 20°C, the photosynthetic rate increased about 10%/C^o. No differences in photosynthetic pattern were observed between epipelic and epipsammic species.     

Action spectra and spectral quantum yield of photosynthesis in marine macroalgae with thin and thick thalli

Net photosynthesis at 10mol photons m^-2 s^-1 in each of 24 wavelengths was measured in absolute units by an O₂-electrode and corrected for dark respiration to construct action spectra for gross photosynthesis in nine species of algae, which included plants with thin and thick thalli from each of four major pigment groups. The photosynthesis of green and brown algae with thin thalli decreased in green light, but species with thick thalli from these two groups had action spectra which were almost flat, and matched the optical blackness of the thalli but did not reflect the pigment differences between the species. Among the red algae, on the other hand, there was little difference between the action spectra for thin and thick algae. Only wavelengths absorbed by the phycobilin pigments were effective in photosynthesis, even in species (e.g. Chondrus, Phyllophora) which absorbed all visible wavelengths strongly. Maximal quantum yields of 0.10 to 0.12 O₂ molecules per absorbed photon were recorded for thin green and brown algae, but thicker algae in these two groups had lower values. Red algae exhibited maximal values close to 0.10 O₂ molecules per absorbed photon, irrespective of thallus thickness or phycocyanin content, but the quantum yields of phycoerythrin-rich species in the 600 to 650 nm waveband were lower than those of phycocyanin-rich species.     

Emerson enhancement effect and quantum yield of photosynthesis for marine macroalgae in simulated underwater light fields

The contribution of enhancement to the total photosynthesis of marine macroalgae in their natural habitats was estimated by comparing the photosynthesis measured by O₂-electrode in five broad-band light fields with that predicted (on the assumption that no enhancement was occurring) from the photosynthetic action spectrum of each plant and the spectral distribution of the light fields. The excess of measured values divided by calculated values provided a measure of enhancement. Although 37% enhancement was observed for red algae in unfiltered quartz-iodine light, and 18% for green and brown algae, substantially lower values were obtained for all species in more natural light fields. In those typical of shallow coastal waters, phycoerythrin-rich red algae exhibited 15 to 20% enhancement, but little enhancement (<5%) was detected in other algae. In a green light field, representing deep coastal water, there was no significant enhancement in any species, and only green and brown algae showed any enhancement (ca 8%) in broad-band blue light, similar to that in deep oceanic waters. Quantum yields of 0.09 to 0.10 O₂ molecules per absorbed photon were recorded in most light fields for green and brown algae with thin thalli, but yields decreased in the blue light field and in species with thicker thalli. All red algae had quantum yields of about 0.08 O₂ molecules per absorbed photon, except in the blue light field, in which quantum yields were reduced by 70%.     

Evaluation of chlorophyll fluorescence, in vivo spectrophotometric pigment absorption and ion leakage as biomarkers of UV-B exposure in marine macroalgae

The photosynthetic fluorescence ratio F_v:F_m, in vivo absorption spectra and ion leakage were evaluated as biomarkers of ambient and elevated UV-B (280 to 320 nm) exposure of the intertidal alga Enteromorpha intestinalis (Chlorophyta) and the sublittoral alga Palmaria palmata (Rhodophyta). Measurements of thallus growth were also used to assess adverse biological effects. Ambient and elevated UV-B significantly inhibited photosynthesis in both species. It was shown that the F_v:F_m ratio is a sensitive, non-specific general biomarker of UV-B exposure in both species. Moreover, the in vivo absorption of what was tentatively identified as chlorophylls a and b as well as phycoerythrin and/or carotenoids, phycoerythrobilin and phycocyanin decreased in a dose-response dependent manner and was associated with a decrease in growth rate in P. palmata. The intertidal alga E. intestinalis showed a greater degree of tolerance to UV-B exposure. These results indicate that changes in the F_v:F_m ratio together with reductions in in vivo pigment absorption could provide an early quantitative warning of the detrimental effects of UV-B in marine macroalgae. Received: 16 May 1997 / Accepted: 16 July 1997     

Effects of tributyl-tin on a marine microalga, Tetraselimis suecica

Marine pollutants induce changes in microalgal metabolism. In this study effects of tributyl-tin chloride (TBTCl) on a marine microalga Tetraselmis suecica was studied. The changes induced by TBTCI on growth rate, viability and biochemicals were assessed. In acute exposure to TBTCl, EC50 estimated for 24 hr was 2.02 microg ml(-1), whereas total lethality was observed at 4 microg ml(-1). In chronic exposure to TBTCl, at higher concentrations (0.5-1 microg ml(-1)) growth rate, chlorophyll pigments, carbohydrate and protein contents were reduced. The results of this study indicate that TBTCl toxicity made drastic changes in growth and biochemical composition of T. suecica.     

Light quality and concentration of proteins,RNA, DNA and photosynthetic pigments in two species of marine plankton algae

Chlorophyll, protein, DNA and RNA concentrations in cultures ofCyclotella nana (Hustedt) andDunaliella tertiolecta (Butcher) were higher in blue light and lower in green light than in white light of the same intensity. Total carotenoid concentrations were highest in green light. Total pigment concentrations were highest in cells grown in blue light, lowest in those from green light. The relative changes in pigment concentrations associated with differences in spectral composition of the radiation are comparable to those often observed in phytoplankton from various depths in stratified natural water. Light adaptation in algae as a response to light quality is suggested. The chemical composition of plankton algae can be expected to vary considerably with depth.     

SO_2和NO_2胁迫对红花荷等植物光合生理影响及抗性评价

为探讨红花荷（Rhodoleia championii）等12种园林植物抗SO2和NO2污染能力,以1～2年生实生苗为材料,通过人工气候室的盆栽实验,研究不同SO2和NO2混合气体胁迫对园林植物苗木光合参数和相对叶绿素含量的影响,并利用隶属函数法及系统聚类分析法对其抗SO2和NO2污染能力进行了综合评价。结果表明,植物叶片净光合速率、气孔导度、蒸腾速率和相对叶绿素含量基本上随着SO2和NO2胁迫的加剧而逐渐降低,但水分利用效率受净光合速率和蒸腾速率变化的影响规律不明显。综合隶属函数和聚类分析可知,红花荷和红千层（Callistemon rigidus）抗污染能力强,杜鹃红山茶（Camellia azalea）和粉红羊蹄甲（Bauhinia blakeana）抗污染能力较强,红花银桦（Grevillea robusta）和无忧树（Saraca divespierre）抗污染能力中等,大叶紫薇（Lagerstroemia speciosa）、金花风铃木（Tabebuia chrysantha）和腊肠树（Cassia fistula）抗污染能力较弱,而本地火焰木（Spathodea nilotica）、复羽叶栾树（Koelreuteria bipinnata）和樱花（Prunus serrulata）抗污染能力弱。研究结果为火电厂、陶瓷厂、钢铁厂、石化厂等重度酸污染地区植物选择提供参考。     

Enigmatic marine ecosystem metabolism measured by direct diel ΣCO2 and O2 flux in conjunction with DOC release and uptake

In an attempt to evaluate CO₂ changes as an index of net ecosystem metabolism, CO₂ and dissolved organic carbon (DOC) by infrared (IR) analysis and O₂ by the Winkler method were followed over 12 diel cycles in a salt marsh, a simulated estuarine ecosystem, and the mixed layer of the northwestern Caribbean Sea. Each ecosystem exhibited replicable diel cycles, net production during the photoperiod, and a significant inverse correlation between CO₂ and O₂ changes. Daily rates of system production and respiration calculated from CO₂, however, exceeded those from O₂ by 1.5 to 3.5 fold in nearshore waters and by 2 to 6 fold in the open ocean. Net total system apparent production based on O₂ and CO₂, respectively, were 2 345 and 3 604 mg C m^-3d^-1 for the salt marsh, 348 and 625 mg C m^-3d^-1 for the estuarine ecosystem, and 53 and 306 mg C m^-3d^-1 for the oceanic ecosystem, both parameters exceeding ¹⁴C data in the literature for similar environments by one to two orders of magnitude. The IR CO₂ productivity estimates are compatible with the diel cycles in DOC. In the marsh and Caribbean Sea, maxinium DOC concentrations were usually observed in the evening following a gradual accumulation during the photoperiod, while minimal values occurred in the early morning. In all ecosystems the average net release of DOC lagged CO₂ uptake and O₂ production and represented 22.7 and 43.3% of the carbon fixed as estimated from CO₂ uptake and O₂ production, respectively. If the consistently higher CO₂ measurements are not a systematic error nor due to atmospheric diffusion, then diel variation in O₂ and CO₂ may not always be quantitatively coupled due in part to habitat-dependent factors such as the nonphotosynthetic incorporation of CO₂ and chemosynthetic removal of O₂.     

Decomposition of perfluorooctanoic acid by microwaveactivated persulfate: Effects of temperature, pH, and chloride ions

Microwave-hydrothermal treatment of persistent and bioaccumulative perfluorooctanoic acid (PFOA) in water with persulfate (S₂O ₈ ^2? ) has been found effective. However, applications of this process to effectively remediate PFOA pollution require a better understanding on free-radical scavenging reactions that also take place. The objectives of this study were to investigate the effects of pH (pH = 2.5, 6.6, 8.8, and 10.5), chloride concentrations (0.01?C0.15 mol·L^?1), and temperature (60°C, 90°C, and 130°C) on persulfate oxidation of PFOA under microwave irradiation. Maximum PFOA degradation occurred at pH 2.5, while little or no degradation at pH 10.5. Lowering system pH resulted in an increase in PFOA degradation rate. Both high pH and chloride concentrations would result in more scavenging of sulfate free radicals and slow down PFOA degradation. When chloride concentrations were less than 0.04 mol·L^?1 at 90°C and 0.06 mol·L^?1 at 60°C, presence of chloride ions had insignificant impacts on PFOA degradation. However, beyond these concentration levels, PFOA degradation rates reduced significantly with an increase in chloride concentrations, especially under the higher temperature.     

Effects of detrital non-native and native macroalgae on the nitrogen and carbon cycling in intertidal sediments

The decay of non-native and native seaweed mixing may modify sediment biogeochemistry and organic matter transfers within benthic food webs according to their composition and biomass. The non-native species Sargassum muticum was deliberately added to the sediment of an intertidal sandflat at different biomass and mixed to the native species Ulva sp. and Fucus vesiculosus. The sediment porewater was then ¹³C and ¹⁵N enriched to test whether both detrital diversity and biomass influenced the transfer of porewater carbon and nitrogen to the sediment and to the macrofauna consumers. More ¹⁵N-nitrogen was mobilized to sediments and macrofauna when the 3-species detrital mixing was buried, probably because this mixing provided species-specific compounds such as polyphenols due to the presence of S. muticum and F. vesiculosus, as well as large amounts of nitrogen due to the presence of Ulva. Our study revealed the importance of detrital diversity and non-native seaweeds for the nitrogen cycling in the benthic food web.     

Values of net compensation irradiation and their dependence on photosynthetic efficiency and respiration in marine unicellular algae

Daily compensation irradiation for net photosynthetic rates (ΣI _comp) of Skeletonema costatum (Greville) Cleve, Chaetoceros ceratosporum Ostenfeld, Nitzschia sp., Thalassiosira nordenskiöldii Cleve, and Chroomonas salina (Wislouch) Butcher were measured during 1979 to obtain values for use in ecological models describing compensation and critical depths of marine phytoplankton. Batch cultures of these unicellular algae were exposed to temperatures and photoperiods varying from 6° to 15°C and 8.4 to 16.0 h, conditions typical of surface water in Saanich Inlet, a fjord in Vancouver Island, British Columbia, Canada. Results obtained with S. costatum and T. nordenskiöldii provided estimates of ΣI _comp varying between 1.8 and 13 J cm^-2 d^-1, from which a mean value of 7.0 J cm^-2 d^-1 was calculated for use in ecological models with neritic phytoplankton. No seasonal variation in compensation irradiation was noted because photosynthetic efficiencies, which increased as division rates increased, were balanced by respiration rates, which increased as temperature increased. Results obtained with Chaetoceros ceratosporum, Nitzschia sp., and Chroomonas salina were difficult to interpret, because respiration rates were stimulated and depressed by light, respectively, for the first two species and the last one. This light effect was greatest when cells grew under conditions of low temperature and short photoperiod. Also, under winter and spring conditions, cells of Nitzschia sp. appeared to fix CO₂ in the dark and with low irradiances by mechanisms other than photosynthesis.