RELATIONSHIP BETWEEN PHOTOSYNTHESIS AND CELL SIZE OF MARINE DIATOMS12

Three photosynthetic parameters of 7 species of marine diatoms were studied using Na₂¹⁴CO₃ at 5–8 C using log phase axenic cultures. The cell volumes of the different species varied from 70 μm³ to 40 × 10⁵μm³. The present experiment is consistent with the interpretation that the initial slope α (mg C · [mg chl a]^?1· h^?1· w^?1· m²) of photosynthesis vs. light curves is controlled by self-shading of chlorophyll a in the cell. Pm, the rate of photosynthesis at light saturation (mg C · [mg cell, C]^?1· h^?1) and R, the intercept at zero light intensity (mg C · [mg cell C]^?1· H^?1) are both dependent on the ratio of surface area to volume of cell.     

Profiling coral reef productivity and calcification using pH and oxygen electrodes

An instrument package carrying pH and oxygen electrodes and a thermister was floated across a reef flat. Using equations associated with the alkalinity anomaly technique, and by making certain assumptions, the productivity and calcification rates of the reef flat were calculated. At an average light intensity of 800 μE · m^?2 · s^?1, the average net oxygen production was 21.5 mmol O₂ · m^?2 · h^?1 and the average rate of calcification was 11.0 mmol CaCO₃ · m^?2 · h^?1. Results showed three metabolic zones within the transect which corresponded to zonation seen in an aerial photograph and confirmed by benthic surveys.     

PHOTOSYNTHESIS,DARK RESPIRATION AND DESICCATION RESISTANCE OF THE INTERTIDAL SEAWEEDS HESPEROPHYCUS HARVEYANUS AND PELVETIA FASTIGIATA F. GRACILIS12

Rates of net photosynthesis and dark respiration were determined under submersed and emerged conditions for Hesperophycus harveyanus S. & G. and Pelvetia fastigiata f. gracilis (Decne.) S. & G. Both species exhibited submersed photosynthesis-light relationships and dark respiration rates similar to those established for other closely related intertidal, fucoids. Maximal net photosynthesis of H. harveyanus (0.21 mmol O₂ g dry wt.^-1· h^-1; 0.18 mmol CO₂ g dry wt.^-1· h^-1) was similar to that of P. fastigiata f. gracilis (0.17 mmol. O₂ g dry wt.^-1· h^-1; 0.14 mmol CO₂ g dry wt. ^-1· h^-1). Light saturation occurred between 150 and 250 μE · m^-2· s^-1 for H. harveyanus and between 75 and 150 μE · m^-2· s^-1 for P. fastigiata f. gracilis; photon flux densities required for compensation were 6.4 and 9.2 μE · m^-2· s^-1, respectively. Photoinhibition was not observed for either species. The light-saturated, submersed net photosynthetic performances of both species varied significantly with temperature. Greatest photosynthetic rates were obtained at 23° C for H. harveyanus and at 18° C for P. fastigiata f. gracilis. Under emersed conditions, the maximal net photosynthetic rate and the photon flux densities required for saturation were greater for H. harveyanus (0.08 mmol CO₂ g dry wt.^-1· h^-1; 260 to 700 μE · m^-2· s^-1) than for P. fastigiata f. gracilis (0.02 mmol CO₂g dry wt.^-1· h^-1; 72 to 125 μE · m^-2· s^-1). However, for both species, emersed photosynthetic rates were much lower (14–44%) than those obtained under submersed conditions. Desiccation negatively influenced emersed photosynthesis, of both species, but H. harveyanus thalli contained more water when fully hydrated and lost water more slowly during dehydration, thus suggesting greater photosynthetic potential during field conditions of emersion.     

PHOTOSYNTHESIS AND RESPIRATION OF THE CONCHOCELIS STAGE OF ALASKAN PORPHYRA (BANGIALES,RHODOPHYTA) SPECIES IN RESPONSE TO ENVIRONMENTAL VARIABLES1

Photosynthesis and respiration of three Alaskan Porphyra species, P. abbottiae V. Krishnam., P. pseudolinearis Ueda species complex (identified as P. “pseudolinearis” below), and P. torta V. Krishnam., were investigated under a range of environmental parameters. Photosynthesis versus irradiance (P–I) curves revealed that maximal photosynthesis (P_max), irradiance at maximal photosynthesis (I_max), and compensation irradiance (I_c) varied with salinity, temperature, and species. The P_max of Porphyra abbottiae conchocelis varied between 83 and 240 μmol O₂ · g dwt^?1 · h^?1 (where dwt indicates dry weight) at 30–140 μmol photons · m^?2 · s^?1 (I_max) depending on temperature. Higher irradiances resulted in photoinhibition. Maximal photosynthesis of the conchocelis of P. abbottiae occurred at 11°C, 60 μmol photons · m^?2·s^?1, and 30 psu (practical salinity units). The conchocelis of P. “pseudolinearis” and P. torta had similar P_max values but higher I_max values than those of P. abbottiae. The P_max of P. “pseudolinearis” conchocelis was 200–240 μmol O₂ · g dwt^?1 · h^?1 and for P. torta was 90–240 μmol O₂ · g dwt^?1 · h^?1. Maximal photosynthesis for P. “pseudolinearis” occurred at 7°C and 250 μmol photons · m^?2 · s^?1 at 30 psu, but P_max did not change much with temperature. Maximal photosynthesis for P. torta occurred at 15°C, 200 μmol photons · m^?2 · s^?1, and 30 psu. Photosynthesis rates for all species declined at salinities <25 or >35 psu. Estimated compensation irradiances (I_c) were relatively low (3–5 μmol · photons · m^?2 · s^?1) for intertidal macrophytes. Porphyra conchocelis had lower respiration rates at 7°C than at 11°C or 15°C. All three species exhibited minimal respiration rates at salinities between 25 and 35 psu.     

LOW THERMAL LIMIT OF GROWTH RATE OF SYMBIODINIUM CALIFORNIUM (DINOPHYTA) IN CULTURE MAY RESTRICT THE SYMBIONT TO SOUTHERN POPULATIONS OF ITS HOST ANEMONES (ANTHOPLEURA SPP.; ANTHOZOA,CNIDARIA)1

Symbiodinium californium (#383, Banaszak et al. 1993 ) is one of two known dinoflagellate symbionts of the intertidal sea anemones Anthopleura elegantissima, A. xanthogrammica, and A. sola and occurs only in hosts at southern latitudes of the North Pacific. To investigate if temperature restricts the latitudinal distribution of S. californium, growth and photosynthesis at a range of temperatures (5°C–30°C) were determined for cultured symbionts. Mean specific growth rates were the highest between 15°C and 28°C (μ 0.21–0.26 · d^?1) and extremely low at 5, 10, and 30°C (0.02–0.03 · d^?1). Average doubling times ranged from 2.7 d (20°C) to 33 d (5, 10, and 30°C). Cells cultured at 10°C had the greatest cell volume (821 μm³) and the highest percentage of motile cells (64.5%). Growth and photosynthesis were uncoupled; light‐saturated maximum photosynthesis (P_max) increased from 2.9 pg C · cell^?1 · h^?1 at 20°C to 13.2 pg C · cell^?1 · h^?1 at 30°C, a 4.5‐fold increase. Less than 11% of daily photosynthetically fixed carbon was utilized for growth at 5, 10, and 30°C, indicating the potential for high carbon translocation at these temperatures. Low temperature effects on growth rate, and not on photosynthesis and cell morphology, may restrict the distribution of S. californium to southern populations of its host anemones.     

LIGHT AND TEMPERATURE AS FACTORS REGULATING SEASONAL GROWTH AND DISTRIBUTION OF ULOTHRIX ZONATA (ULVOPHYCEAE)1

Ulothrix zonata (Weber and Mohr) Kütz. is an unbranched filamentous green alga found in rocky littoral areas of many northern lakes. Field observations of its seasonal and spatial distribution indicated that it should have a low temperature and a high irradiance optimum for net photosynthesis, and at temperatures above 10°C it should show an increasingly unfavorable energy balance. Measurements of net photosynthesis and respiration were made at 56 combinations of light and temperature. Optimum conditions were 5°C and 1100 μE·m^?2·s^?1 at which net photosynthesis was 16.8 mg O₂·g^?1·h^?1. As temperature increased above 5° C optimum irradiance decreased to 125 μE·m^?2·s^?1 at 30°C. Respiration rates increased with both temperature and prior irradiance. Light-enhanced respiration rates were significantly greater than dark respiration rates following irradiance exposures of 125 μE·m^?2·s^?1 or greater. Polynomials were fitted to the data to generate response surfaces. Polynomial equations represent statistical models which can accurately predict photosynthesis and respiration for inclusion in ecosystem models.     

PRODUCTIVITY OF THE FILAMENTOUS ALGA PITHOPHORA OEDOGONIA (CHLOROPHYTA) IN SURREY LAKE,INDIANA1

Biomass, akinete numbers, net photosynthesis, and respiration of Pithophora oedogonia were monitored over two growing seasons in shallow Surrey Lake, Indiana. Low rates of photosynthesis occurred from late fall to early spring and increased to maximum levels in late spring to summer (29–39 mgO₂·g^?1 dry wt·h^?1). Areal biomass increased following the rise in photosynthesis and peaked in autumn (163–206g dry wt·m^?2). Photosynthetic rates were directly correlated with temperature, nitrogen, and phosphorus over the entire annual cycle and during the growing season. Differences in photosynthetic activity and biomass between the two growing seasons (1980 and 1981) were apparently related to higher, early spring temperatures and higher levels of NO₃-N and PO₄-P in 1981. Laboratory investigations of temperature and light effects on Pithophora photosynthesis and respiration indicated that these processes were severely inhibited below 15°C. The highest P_max value occurred at 35°C (0.602 μmol O₂·mg^?1 chl a·min^?1). Rates of dark respiration did not increase above 25°C thus contributing to a favorable balance of photosynthetic production to respiratory utilization at high temperatures. Light was most efficiently utilized at 15°C as indicated by minimum values of I_k(47 μE·m^?2·s^?1) and I_c (6 μE·m^?2·s^?1). Comparison of P. oedogonia and Cladophora glomerata indicated that the former was more tolerant of temperatures above 30°C. Pithophora's tolerance of high temperature and efficient use of low light intensity appear to be adaptive to conditions found within the dense, floating algal mats and the shallow littoral areas inhabited by this filamentous alga.     

COMPARISON OF DEVELOPMENT AND PHOTOSYNTHETIC GROWTH FOR FILAMENT CLUMPS AND REGENERATED MICROPLANTLET CULTURES OF AGARDHIELLA SUBULATA (RHODOPHYTA, GIGARTINALES)

Two axenic, in vitro liquid suspension cultures were established for Agardhiella subulata (C. Agardh) Kraft et Wynne, and their growth characteristics were compared. This study illustrated how reliable routes for the development of suspension cultures of macrophytic red algae of terete thallus morphology can be achieved for biotechnology applications. Undifferentiated filament clumps of 2–8 mm diameter were established by induction of callus-like tissue from thallus explants, and lightly branched microplantlets of 2–10 mm length were established by regeneration of filament clumps. The filament clumps were susceptible to regeneration. Adventitious shoot formation was reliably induced from 40% to 70% of the filament clumps by gentle mixing at 100 rev min^?1 on an orbital shaker. The specific growth rate of the microplantlets was higher than the filament clumps in nonagitated well plate culture (4%–6% per day for microplantlets vs. 2%–3% per day for filament clumps) at 24° C and 8–36 μmol photons·m^?2·s^?1 irradiance (10:14 h LD cycle) when grown on ASP12 artificial seawater medium at pH 8.6–8.9 with 20%–25% per day medium replacement. Oxygen evolution rate vs. irradiance measurements showed that relative to the filament clumps, microplantlets had a higher maximum specific oxygen evolution rate (P_o,max= 0.181 ± 0.035 vs. 0.130 ± 0.023 mmol O₂·g^?1 dry cell mass·h^?1), but comparable respiration rate (Q_o= 0.040 ± 0.013 vs. 0.033 ± 0.017 mmol O₂·g^?1 dry cell mass·h^?1), compensation point (I_c= 3.8 ± 2.4 vs. 5.7 ± 1.2 μmol photons·m^?2·s^?1), and light intensity at 63.2% of saturation (I_k= 17.5 ± 3.9 vs. 14.9 ± 2.6 μmol photons·m^?2·s^?1). The microplantlet culture was more suitable for suspension culture development than the filament clump culture because it was morphologically stable and exhibited higher growth rates.     

CARBON ALLOCATION IN MACROCYSTIS PYRIFERA (PHAEOPHYTA): INTRINSIC VARIABILITY IN PHOTOSYNTHESIS AND RESPIRATION1

Measurements of net photosynthesis (PS, O₂ evolution), dark respiration (R, O₂ consumption), and light and dark carbon fixation (¹⁴C) were conducted on whole blades, isolated blade discs, sporophylls, apical scimitars and representative portions of stipe and holdfast of the giant kelp Macrocystis pyrifera L.C. Ag. On a dry weight basis, highest net PS rates were observed in apical scimitar segments and whole blades (3.81 and 3.07 mgC · g dry wt^?1· h^?1, respectively), followed by sporophylls (1.42 mgC·g dry wt^?1· h^?1) and stipe segments (0.15 mgC·g dry wt^?1· h^?1). No PS capacity was observed in holdfast material. Respiration rates showed similar ranking ranging from 1.22 mgC·g dry wt^?1·h^?1 for apical scimitar to 0.18–0.22 mgC·g dry wt^?1· h^?1 for holdfast material. Considerable within blade variability in both PS and R was also found. Steepest PS and R gradients on both an areal and weight basis were found within immature blades followed by senescent and mature blade material. Highest net PS rates were associated with the blade tips ranging from 3.08 (mature blades) to 10.3 mgC·dry wt^?1·h^?1 (immature blades). Highest rates of R generally occurred towards the basal portions of blades and ranged from 1.03–1.80 mgC·g dry wt^?1·h^?1 for immature blades. The variability within and between blades was high, with coefficients of variation approaching 50%. The observed patterns can be related to the decreasing proportionment of photosynthetic tissue and increasing proportionment of structural tissue as occurs from the blade tip to the blade base. Rates of light carbon fixation (LCF) revealed longitudinal profiles similar to oxygen measurements for the different blade types, with the absolute rates being slightly lower. Patterns of dark carbon fixation (DCF) were less easily interpreted. Highest rates of DCF (0.04–0.06 mgC·g dry wt^?1·h^?1) occurred at the basal portions of immature and senescent blades. Longitudinal profiles of total chlorophyll (a + c) on both an areal and weight basis were very similar to the profiles of PS. Normalized to chlorophyll a, PS displayed an unusual longitudinal profile in immature tissue; however, such profiles for mature and senescent tissues were similar to those for PS on an areal basis. It was demonstrated that it is difficult, if not impossible, to select single tissue discs that are representative of whole blades. The metabolic longitudinal profiles reveal a characteristic developmental pattern; the previous working definitions of immature, mature, and senescent blades, based on morphology and frond position thus have a physiological basis.     

Heart rate as an indicator of metabolic rate and activity in adult Atlantic salmon, Salmo salar

Telemetered heart rate (f_H) was examined as an indicator of activity and oxygen consumption rate (VO₂) in adult, cultivated, Atlantic salmon, Salmo salar L. Heart rate was measured during sustained swimming in a flume for six fish at 10° C [mean weight, 1114 g; mean fork length (f. l.), 50·6 cm] and seven fish at 15° C (mean weight, 1119 g; mean f. l., 50·7 cm) at speeds of up to 2·2 body lengths/s. Semi–logarithmic relationships between heart rate and swimming speed were obtained at both temperatures. Spontaneously swimming fish in still water exhibited characteristic heart rate increases associated with activity. Heart rate and Vo₂ were monitored simultaneously in a 575–1 circular respirometer for six fish (three male, three female) at 4° C (mean weight, 1804 g; mean F. L., 62· cm) and six fish (three male, three female) at 10° C (mean weight, 2045 g; mean f. l., 63·2 cm) during spontaneous but unquantified activity. Linear regressions were obtained by transforming data for both f_H and Vo₂ to log values. At each temperature, slopes of the regressions between f_H and Vo₂ for individual fishes were not significantly different, but in some cases elevations were. All differences in elevation were between male and female fish. There were no significant differences in regression slope or elevation for fish of the same sex at the two temperatures and so regressions were calculated for the sexes, pooling data from 4 and 10° C. There was no significant difference in the mean ± S. D. Vo₂ between the sexes at 4° C (male, 66·0 ± 59·6 mgO₂ kg^?1 h^?1; female, 88·0 ± 60·1 mgO₂ kg^?1 h^?1) or 10° C (male, 166·2 ± 115·4 mgO₂ kg^?1 h^?1; female, 169·2 ± 111–1 mgO₂ kg^?1h^?1). Resting Vo₂ (x?± s. d.) at 4°C was 36·7 ± 8.4 mgO₂ kg^?1 h^?1, and 10° C was 72·8 ± 11·9 mgO₂ kg^?1 h^?1. Maximum Vo₂ (x?± S. D.) at 4° C was 250·6 ± 40·2 mgO₂ kg^?1 h^?1, and at 10° C was 423·6 ± 25·2 mgO₂ kg^?1 h^?1. Heart rate appears to be a useful indicator of metabolic rate over the temperature range examined, for the cultivated fish studied, but it is possible that the relationship for wild fish may differ.     

Temperature response of photosynthetic light‐ and carbon‐use characteristics in the red seaweed Gracilariopsis lemaneiformis (Gracilariales,Rhodophyta)

The red seaweed Gracilariopsis is an important crop extensively cultivated in China for high‐quality raw agar. In the cultivation site at Nanao Island, Shantou, China, G. lemaneiformis experiences high variability in environmental conditions like seawater temperature. In this study, G. lemaneiformis was cultured at 12, 19, or 26°C for 3 weeks, to examine its photosynthetic acclimation to changing temperature. Growth rates were highest in G. lemaneiformis thalli grown at 19°C, and were reduced with either decreased or increased temperature. The irradiance‐saturated rate of photosynthesis (P_max) decreased with decreasing temperature, but increased significantly with prolonged cultivation at lower temperatures, indicating the potential for photosynthesis acclimation to lower temperature. Moreover, P_max increased with increasing temperature (~30 μmol O₂ · g^?1FW · h^?1 at 12°C to 70 μmol O₂ · g^?1FW · h^?1 at 26°C). The irradiance compensation point for photosynthesis (I_c) decreased significantly with increasing temperature (28 μmol photons · m^?2 · s^?1 at high temperature vs. 38 μmol photons · m^?2 · s^?1 at low temperature). Both the photosynthetic light‐ and carbon‐use efficiencies increased with increasing growth or temperatures (from 12°C to 26°C). The results suggested that the thermal acclimation of photosynthetic performance of G. lemaneiformis would have important ecophysiological implications in sea cultivation for improving photosynthesis at low temperature and maintaining high standing biomass during summer. Ongoing climate change (increasing atmospheric CO₂ and global warming) may enhance biomass production in G. lemaneiformis mariculture through the improved photosynthetic performances in response to increasing temperature.     

Regulation of the induction of bicarbonate uptake by dissolved CO2 in the marine diatom, Phaeodactylum tricornutum

Physiological properties of photosynthesis were determined in the marine diatom, Phaeodactylum tricornutum UTEX640, during acclimation from 5% CO₂ to air and related to H₂CO₃ dissociation kinetics and equilibria in artificial seawater. The concentration of dissolved inorganic carbon at half maximum rate of photosynthesis (K_0·5[DIC]) value in high CO₂‐grown cells was 1009 mmol m ^{? 3} but was reduced three‐fold by the addition of bovine carbonic anhydrase (CA), whereas in air‐grown cells K_0·5[DIC] was 71 mmol m ^{? 3}, irrespective of the presence of CA. The maximum rate of photosynthesis (P_max) values varied between 300 and 500 μ mol O₂ mg Chl ^{? 1} h ^{? 1} regardless of growth pCO₂. Bicarbonate dehydration kinetics in artificial seawater were re‐examined to evaluate the direct HCO₃ ^? uptake as a substrate for photosynthesis. The uncatalysed CO₂ formation rate in artificial seawater of 31·65°/_oo of salinity at pH 8·2 and 25 °C was found to be 0·6 mmol m ^{? 3} min ^{? 1} at 100 mmol m ^{? 3} DIC, which is 53·5 and 7·3 times slower than the rates of photosynthesis exhibited in air‐ and high CO₂‐grown cells, respectively. These data indicate that even high CO₂‐grown cells of P. tricornutum can take up both CO₂ and HCO₃ ^? as substrates for photosynthesis and HCO₃ ^? use improves dramatically when the cells are grown in air. Detailed time courses were obtained of changes in affinity for DIC during the acclimation of high CO₂‐grown cells to air. The development of high‐affinity photosynthesis started after a 2–5 h lag period, followed by a steady increase over the next 15 h. This acclimation time course is the slowest to be described so far. High CO₂‐grown cells were transferred to controlled DIC conditions, at which the concentrations of each DIC species could be defined, and were allowed to acclimate for more than 36 h. The K_0·5[DIC] values in acclimated cells appeared to be correlated only with [CO_2(aq)] in the medium but not to HCO₃ ^? , CO₃^{2 ?} , total [DIC] or the pH of the medium and indicate that the critical signal regulating the affinity of cells for DIC in the marine diatom, P. tricornutum, is [CO_2(aq)] in the medium.     

A CARBON BUDGET FOR THE AUTOTROPHIC CILIATE MESODINIUM RUBRUM1

Extensive blooms of the autotrophic ciliate Mesodinium rubrum (Lohmann) occurred in the Peru coastal upwelling region at 15°S latitude in March through May 1977 and contributed significantly to the organic productivity of the region. From observations made during the JOINT-II oceanographic expedition, a budget of the carbon flux of these unusual photosynthetic organisms can be constructed. The light dependent C fixation was determined with short (1 h) incubations because of the organisms' sensitivity to confinement and rapid nutrient exhaustion. Maximum photosynthesis occurred at 50% of incident light with a maximum rate of particulate C synthesis of 2187 mg C · m^?3· h^?1. The specific carbon uptake rates were also high with a maximum light saturated value of 16.8 mg C ·(mg chl a)^?1· h^?1. The rate of excretion of dissolved organic C at the productivity maximum ranged from 16.1 to 181.1 mg C · m^?3· h^?1. The range of percent excretion was 1.8–12.5% the total C fixed, similar to the range found in both motile and nonmotile phytoplankton assemblages. Respiration, determined by the decrease in particulate C in the dark, averaged 4.6% of the previously fixed photosynthetic C · h^?1. M. rubrum actively took up amino acids and naturally occurring dissolved organic carbon. The C budget for this ciliate indicates that the daily contribution to the particulate food chain is large, although not as great as is indicated by short incubations. The contribution of M. rubrum to the productivity and elemental fluxes of upwelling and coastal ecosystems has been seriously underestimated.     

PRIMARY PRODUCTION OF CRUSTOSE CORALLINE RED ALGAE IN A HIGH ARCTIC FJORD1

Crustose coralline algae occupied ～1%–2% (occasionally up to 7%) of the sea floor within their depth range of 15–50 m, and they were the dominant encrusting organisms and macroalgae beyond 20 m depth in Young Sound, NE Greenland. In the laboratory, oxygen microelectrodes were used to measure net photosynthesis (P) versus downwelling irradiance (E_d) and season for the two dominant corallines [Phymatolithon foecundum (Kjellman) Düwel et Wegeberg 1996 and Phymatolithon tenue (Rosenvinge) Düwel et Wegeberg 1996] representing> 90% of coralline cover. Differences in P‐E_d curves between the two species, the ice‐covered and open‐water seasons, or between specimens from 17 and 36 m depth were insignificant. The corallines were low light adapted, with compensation irradiances (E_c) averaging 0.7–1.8 μmol photons·m ^{? 2}·s ^{? 1} and light adaptation (E_k) indices averaging 7–17 μmol photons·m ^{? 2}·s ^{? 1}. Slight photoinhibition was evident in most plants at irradiances up to 160 μmol photons·m ^{? 2}·s ^{? 1}. Photosynthetic capacity (P_m) was low, averaging 43–67 mmol O₂·m ^{? 2} thallus·d ^{? 1} (～250–400 g C·m ^{? 2} thallus·yr ^{? 1}). Dark respiration rates averaged ～5 mmol O₂·m ^{? 2} thallus·d ^{? 1}. In ice covered periods, E_d at 20 m depth averaged ～1 μmol photons·m ^{? 2}·s ^{? 1}, with daily maxima of 2–3 μmol photons·m ^{? 2}·s ^{? 1}. During the open water season, E_d at 20 m depth averaged ～7 μmol photons·m ^{? 2}·s ^{? 1} with daily maxima of ～30 μmol photons·m ^{? 2}·s ^{? 1}. Significant net primary production of corallines was apparently limited to the 2–3 months with open water, and the small contribution of corallines to primary production seems due to low P_m values, low in situ irradiance, and their relatively low abundance in Young Sound.     

PHYSIOLOGICAL VARIATION AND ELECTROPHORETIC BANDING PATTERNS OF GENETICALLY DIFFERENT SEASONAL POPULATIONS OF SKELETONEMA COSTATUM (BACILLARIOPHYCEAE)1

Clones of Skeletonema costatum (Grev.) Cl. isolated from Narragansett Bay, R.I., during different seasons were grouped according to their electrophoretic banding patterns. The growth rates, pg chlorophyll · cell^?1, carbon uptake · cell^?1· h^?1, and carbon uptake · pg chl^?1· h^?1 were measured at 20°C, in a 14:10 h L:D cycle at 180 μE · m^?2· s^?1. Statistically significant sources of variation were found among groups of clones in growth rate, pg chl · cell^?1, and carbon uptake · pg chl^?1· h^?1. It was concluded that there is a significant relationship between the physiological characteristics of clones isolated from populations in different seasons and patterns of genetic variation inferred from the electrophoretic studies. However, genetic diversity detected by banding patterns tends to underestimate the total genetic diversity in natural populations. The groups of clones most common in summer bloom populations had significantly higher growth rates, lower values of pg chl · cell^?1, and higher rates of carbon uptake · pg chl^?1· h^?1 at 20°C than did the group of clones most common in winter bloom populations. However, differences among groups in these parameters at 20°C alone cannot account for the seasonal cycling of genetically variable populations of Skeletonema in Narragansett Bay. The range of growth rates among clones of this species is 0.1–5.0 divisions · d^?1 under a single set of temperature and light conditions. Chlorophyll concentrations range from 0.2–1.7 pg chl · cell^?1 and carbon uptake · pg chl^?1· h^?1 varies by a factor of 7 among clones. The range of physiological variation in this species means that it is difficult to use laboratory studies of single clones to analyze the responses of natural populations of Skeletonema.     

Modelling the inhibitory effect of copper sulfate on the growth of Penicillium expansum and Botrytis cinerea

Aims: This study aimed to investigate the effect of copper sulfate (from 0 to 8 mmol kg^?1) on radial growth rate and lag time of two moulds responsible for vine grapes spoilage: Penicillium expansum strain 25·03 and Botrytis cinerea, strains BC1 and BC2. Methods and results: A new model was developed to describe tailing and shoulders in the inhibition curves. Because of tailing, the minimum inhibitory concentration (MIC), was not defined as the concentration at which no growth was observed, but as the concentration at which the lag time was infinite. The concentrations at which μ = μ_opt/2, (Cu₅₀), were in the range of 2·2–2·6 mmol kg^?1. Radial growth rate of P. expansum and the reciprocal of the lag time were linearly correlated (r = 0·84). In contrast, in the range 0–4 mmol kg^?1, an inhibition of growth of B. cinerea was observed whereas germination remained unaffected (i.e. the lag time was constant). In the range 4–8 mmol kg^?1, the radial growth rate of B. cinerea was almost constant (c. 1 mm day^?1), but germination was inhibited (i.e. the lag time was increased). Conclusions: The MIC values were 4·7 mmol kg^?1 for P. expansum, 8·2 and 7·3 mmol kg^?1 for B. cinerea strain BC1 and BC2, respectively, demonstrating that some isolates of these moulds are resistant to copper. Significance and Impact of the Study: Copper concentrations at 4 mmol kg^?1 would be sufficient to control the development of these isolates, but the toxicity of copper should be extended to other isolates and evaluated in vineyards.     

Enzymatic synthesis of new aromatic and aliphatic esters of flavonoids using Candida antarctica lipase as biocatalyst

Enzymatic acylation of rutin and esculin with aromatic, aliphatic and aryl-aliphatic acids using Candida antarctica lipase in tert amyl alcohol as solvent was investigated under low water content. Whatever the acyl donor used, the conversion yields and initial rates for esculin were higher than for rutin. For a given flavonoid, the performance of these reactions depended on the acyl donor structures. For aliphatic acids, conversion yields and initial rates of both flavonoids were respectively in the ranges of 68–90% and of 9.5×10^?2–72×10^?2 mmol l^?1 h^?1. For aromatic acids, the reaction occurred only with the aryl subgroup (cinnamic, hydrocinnamic, 3,4-dihydroxyhydrocinnamic and 4-hydroxyphenyl acetic acids) and was drastically influenced by the presence of side chain and substitution patterns of the aromatic ring. Except for hydrocinnamic acid (75%, 23.4×10^?2 mmol l^?1 h^?1), with these acids the conversion yields and initial rates were lower and in the range of 10–45% and of 0.7×10^?2 to 12.1×10^?2 mmol l^?1 h^?1. Unsaturation of the side chain of the hydrocinnamic acid decreased the esculin conversion rate from 75 to 13% and initial rate from 23.4 to 1.76×10^?2 mmol l^?1 h^?1. The presence of hydroxyl or nitro-groups on the aromatic ring of the aryl aliphatic acid also reduced conversion yields and initial rates. Even without a spacer, the non-phenolic ring acid (quinic acid) was reactive and lead to conversion yields of about 20 and 23% respectively for rutin and esculin.     

PHYSIOLOGICAL INDICATORS OF NUTRIENT DEFICIENCY IN CLADOPHORA (CHLOROPHYTA) IN THE CLARK FORK OF THE COLUMBIA RIVER,MONTANA1

Cellular nutrient concentrations and nutrient uptake rates of Cladophora glomerata (L.) Kuetzing were determined during summer and fall in 1989–1990 at a site on the upper Clark Fork of the Columbia River, Montana. Both physiological tests indicated that Cladophora growth is likely to be limited by nitrogen during late summer-early fall. Maximum uptake rates of ammonia-N and nitrate-N were 5935–6991 and 507–984 μg · g DW^?1· h^?1, respectively, during July–October when dissolved inorganic nitrogen (DIN) concentrations in the river were less than 10 μg · L^?1. During November-December, when DIN was 72–376 μg · L^?1, maximum ammonia-N uptake was 1137–1633 μg · g DW^?1· h^?1 and maximum nitrate-N uptake was 0–196 μg · g DW^?1· h^?1. Cellular nitrogen during summer–early fall was 0.78–1.80% of Cladophora dry weight, frequently at or below 1.1%, a level suggested as a critical minimum N concentration for maximum growth. In contrast, cellular P was 0.18–0.36% of dry weight, 3–6 times the suggested critical P concentration of 0.06%. Molar ratios of cellular N:P (< 16:1) and DIN: SRP (< 4:1) during late summer-early fall also indicated potential N limitation. Cellular N and P from Cladophora collected from a second site influenced by a municipal wastewater discharge in 1990 displayed similar seasonal trends. At both sites, seasonal fluctuations in DIN were closely tracked by changes in cellular N, Cellular P, however, increased through the growing season despite declining levels of SRP in the river.     

Seasonal nitrate physiology of Macrocystis integrifolia Bory

Ambient sea-water nitrate and tissue nitrogen (ethanol soluble nitrate and amino acids, as well as total nitrogen) of Macrocystis integrifolia Bory were monitored over a 2-yr period in Bamfield, Vancouver Island, British Columbia. Sea-water nitrate varied from a high of 12 μmol · 1^?1 (individual values as high as 23 μmol · 1^?1 were recorded) in late winter to below detection limits for most of the summer. Tissue nitrate and total nitrogen paralleled the ambient nitrate levels and showed summer minima and winter maxima (from 0 to 70 μmol · g fresh wt^?1 for nitrate and from 0.8 to 2.9% of dry wt for total N). The nitrate uptake capacity was inversely proportional to tissue nitrate concentration and, furthermore, was much higher for subapical surface blades (60–70 nmol · cm^?2 · h^?1) than for older, deeper blades (5–10 nmol · cm^?2 · h^?1). Nitrate uptake by subapical blade disks in summer is apparently higher in dark (1.0–1.7 μmol · g fresh wt^?1 · h^?1) than in light (0.6–1.3 μmol · g fresh wt^?1 · h^?1) and the data obtained in 36–108 h experiments indicate nitrate pool sizes of 30–90 μmol · g fresh wt^?1. These pools are $\text{2}\text{3}$ to nearly full in winter. Ammonium does not inhibit nitrate uptake. It is taken up and apparently utilized much faster than nitrate and it may well be an important source of nitrogen for marine macrophytes.