摘要:

ABSTRACTRates of net photosynthesis and dark respiration were determined under submersed and emerged conditions forHesperophycus harveyanus S.&G.andPelvetia fastigiataf.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 ofH. harveyanus (0.21 mmol O2g dry wt.‐1· h‐1; 0.18 mmol CO2g dry wt.‐1· h‐1) was similar to that of P. fastigiataf.gracilis(0.17 mmol. O2g dry wt.‐1· h‐1; 0.14 mmol CO2g dry wt.‐1· h‐1). Light saturation occurred between 150 and 250 μE · m‐2· s‐1forH. harveyanus and between 75 and 150 μE · m‐2· s‐1for P. fastigiataf.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 forH. harveyanusand at 18° C forP. fastigiataf.gracilis.Under emersed conditions, the maximal net photosynthetic rate and the photon flux densities required for saturation were greater forH. harveyanus (0.08 mmol CO2g dry wt.‐1· h‐1; 260 to 700 μE · m‐2· s‐1) than for P. fastigiataf.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, butH. harveyanusthalli contained more water when fully hydrated and lost water more slowly during dehydration, thus suggest

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00371.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTOne hundred and fifteen clonal, unialgal strains were isolated and tested for their ability to grow over a range of temperatures from 2 to 40° C. Responses of 63 strains isolated from habitats that were 6° C when sampled and 52 strains isolated from habitats that were 20° C when sampled showed trends toward increasing adaptation to cold or warm temperatures commensurate with their seasonal in situ temperatures. Based on temperature‐growth responses alone, 24% of the plankton isolates and 17% of the periphyton isolates could be perennial within the natural habitats. At 5° C, 56% of the warm water plankton isolates and 48% of the warm water periphyton isolates were incapable of growth and, therefore, probably could not be important components of the winter algal community. Likewise at 25° C, 25% of the cold water plankton isolates and 13% of the cold water periphyton isolates were incapable of growth. Thus, temperature alone probably is an important variable regulating seasonal changes in algal community structure. Pollution of these habitats by a thermal enrichment averaging + 5° C year‐round could effect a pronounced change in algal species composition because many more taxa could be perennial and more taxa would be incapable of growth during naturally war

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00380.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe morphology of the valve ofCoscinodiscus wailesiiand the development of its siliceous architecture, studied in the SEM and TEM, is compared with valve formation inThalassiosira eccentrica(Ehrenberg.) Cleve. Though the areolae‐architecture of these two species differs in such that the cribrum is proximal and the foramen distal inT. eccentrica, and inC. wailesiithe cribrum is distal and the foramen proximal, the formation of their complex loculate system is similar, displacing a centrifugal growth pattern with respect to the valve, and a proximal to distal, sequentially. During base layer formation a hitherto undescribed rib system outlines the prospective areolae. The vertical differentiation is in principle the same as inT. eccentricaand also the cribra are formed centripetally in relation to the areolae in both species. The location of the cribra at the proximal or distal side, therefore, seems to be of minor importance for the sequence of silica deposition. Variation in girdle bands is discussed with respect to cell division. The prophasic nuclear migration from the interphase position to the girdle bands, where mitosis is performed, seems to be necessary for triggering the formation of the unilateral cleavage furrow that later forms a cleavage ring with excentric position. The divided nuclei migrate with the ingrowing cleavage furrow to the center of the newly created protoplasmic surfaces to initiate valve formatio

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00387.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe metabolic fate of photosynthetically‐fixed CO2was determined by labeling samples ofMerismopedia tenuissimaLemmerman for 30 min with NaH14CO3and analyzing its incorporation into low molecular weight compounds, polysaccharide and protein. In N‐ and P‐sufficient cultures, relative incorporation into protein increased as the irradiance used during the labeling period was decreased to 20 μE · m‐2s‐1. This pattern was found for cells grown at irradiances of either 20 or 180 μE · m‐2· s‐1, although incorporation into protein was greater in cultures grown at the higher irradiance. In N‐limited continuous cultures, relative incorporation into protein was low, independent of growth rate, and the same for samples tested at 20 or 180 μE · m‐2· s‐1irradiance. In contrast,14C incorporation into protein by P‐limited cultures increased as growth rate increased, and at relative growth rates greater than 0.25, the incorporation was greater at 20 than at 180 μE · m‐2· s‐1. However, the total RNA content and maximum photosynthetic rate of the cultures was the same at all growth rates tested. The interaction between nutrient concentration and light intensity was studied by growing‐limited continuous cultures at the same dilution rate, but different irradiances. Relative incorporation into protein was highest in cultures grown at 20 μE · m‐2· s‐1, in which the relative growth rate was 0.4. These results suggest that photosynthetic carbon metabolism may respond to relative growth r

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00403.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe typical morphology ofMonostroma oxyspermum(Kütz.) Doty is lost in axenic culture. In synthetic media of the ASP type, it grows as a colony‐like mass composed of round cells with numerous rhizoids. Such a mass is a fragile structure which falls apart upon shaking, or slight touch, into small cell‐groups and single cells or cells with a long rhizoid. Only temporary saccate or monostromatic fronds appear and reach 1–2 mm in length when grown in enriched seawater media, but disintegrate and become a colony‐like mass. The typical morphology is easily restored by adding at specific intervals filtrates of bacterial cultures and supernatant medium from axenic brown and red algal cultures to the basal medium (ASP7), or by reinfecting theMonostromawith an appropriate bacterial flora. Furthermore, the typical morphology in also maintained by bialgal cultures betweenMonostromaand other axenic strains of various species of seaweeds except the species belonging to the Chlorophyceae.Monostromathus appears to utilize some substances released by most species of brown and red algae for its typical growth. Active substances released by bacteria, brown and red algae have not yet been identified and purified. However, it is demonstrated that in axenic cultures many species of seaweeds produce active extracellular substances which play an important role in growth and Morphogenesis of other species of

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00409.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe fatty acid, sterol and chlorophyll composition of the calcified, unicellular algaThoracosphaera heimii(Lohmann) Kamptner are reported. The presence of 4,23,24‐termethyl‐5α‐cholest‐22E‐en‐3β‐ol (dinosterol), 4,23,24‐trimethyl‐5α‐cholest‐22E‐en‐3‐one (dinosterone) and the predominance of C18, C20and C22unsaturated fatty acids, including the acid 18:5ω3, indicates thatT. heimiiis a dinoflagellate. The fatty acid: sterol ratio (1.3), is typical of dinoflagellates. The geochemical significance of dinosterone, the high relative concentration of 4‐desmethyl‐5α‐stanols and the role of 23‐methyl‐5α‐cholest‐22E‐en‐3β‐ol in the bi

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00416.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTPhosphoenolpyruvate carboxykinase was purified to electrophoretic homogeneity from the brown alga.Ascophyllum nodosum(L.) le Jol. Its molecular mass was 60 kDa as determined by gel filtration. The pH optimum of the carboxylating reaction was 7.9 and the apparent Kmfor PEP4, ADP and HCO3‐were 0.036, 0.0116 and 50 mol · m‐3, respectively. Rates of light and dark carbon fixation are also reported forA. nodosumapices and it is shown that rates of in vitro PEPCK activity would account for the observed rate of dark fixation. The physiological role of PEPCK is discussed in relation to light‐independent carbon fi

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00421.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe adaptive significance of a life‐history strategy, expressed as divergent morphological forms, was examined for the heteromorphic algaScytosiphon lomentaria.Successional studies were performed by physically clearing mature, temporally‐constant intertidal communities on San Clemente I., California. At week six, after clearing, complanate thalli dominated the successional plots (mean cover = 23.5%) and began to decline as the cylindrical form became abundant. The latter attained its peak cover (82.3%) at week 13, whereupon it too began a precipitous reduction. The crustose ralfsioid form appeared surprisingly early (4–13 wks) in trace amounts but did not achieve its greatest cover (85.0%) until week 43. The ranking from high to low primary productivity (cylindrical form = 8.1 mg C · g dry. wt‐1·h‐1, complanate form = 6.5 mg, crustose form = 0.5 mg) corresponded closely with the data for photosynthetic vs. structural components (cylindrical = 92.3% pigmented, complanate = 65.3%, crustose = 32.0%). This finding indicates that selection in the crust form, which is more readily accessible to epilithic grazers, has tended to increase allocation of materials to nonpigmented structural tissue at the expense of photosynthetic tissue and reduced production rates. The results for thallus losses to urchin grazing over 48 h were complanate form = 82.7% lost, cylindrical = 81.4% and crustose = 16.2%, which correlates with the calorific contents of the three forms (i.e. complanate = 4.97 kcal · ash‐free g dry wt.‐1, cylindrical = 4.46 kcal and crustose = 3.55 kcal). The crustose form had tougher thalli (26 g · mm‐2to penetrate thallus) than either the complanate form (12 g) or the cylindrical form (15 g). It is likely that opposing selective factors have resulted in the evolutionary divergences observed in algae with heteromorphic life histories. Previous work may have overemphasized the selective role of grazing because the crustose form is also adapted to withstand physical forces (sand‐scouring, burial and wave‐shearing) or as an overwintering stage under physiological

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00425.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe structure, productivity and heterotrophic potential of an extensive microalgal community growing on the underside of sea ice near the Australian Antarctic Station of Casey, are described. Underwater observations made near the Australian Antarctic stations of Davis and Mawson are also reported. This community develops during September, is largely suspended from the bottom surface of annual sea ice and often extends into the underlying water column as conspicuous strands up to 15 cm long. The algal community structure in the strands is dominated by an unidentified tube diatom belonging to theAmphipleura/Berkeleyagroup and chains of a species ofEntomoneiscf.Amphiprora paludosavar.hyperborea(Grunow) Cleve. Unlike previously described bottom ice environments, a brash ice layer under the hard sea ice is absent. Living cells, predominantlyNitzschia frigidaGrunow, also occur in microbrine channels in the bottom 3 cm of the ice. Maximal primary production rates of 81 μg C · L‐1· h‐1occurred during November, then began declining near the end of December. Minimal rates (2.8 μg C · L‐1· h‐1) were reached in mid‐January and coincided with changes in the physical structure of the sea ice and in the stability of the water column. An abundant epibacterial community associated with the microalgal strands assimilated3H‐labelled amino acids suggesting significant heterotrophic recycling of dissolved organic matter. Turnover times of assimilated amino acids in the bottom ice community averaged 55 h during November while negligible turnover of these substrates occurred in the water column 1.5 m below the ice. These bottom ice communities have higher primary productivity than typical brash ice communities; they are also accessible to marine herbivores and so may be more important to the Antarctic marine food chain than pr

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00431.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe feasibility of estimating phytoplankton carbon and RNA concentrations from measurements of ATP and chlorophylla(chla)concentrations was studied using chemostat populations of the marine diatomThalassiosira weissflogii(Grunow) Fryxell&Hasle(= T. fluviatilisHustedt). C:ATP and RNA:ATP ratios were studied for six additional marine species in batch culture representing five classes of phytoplankton. Statistical analyses revealed that both the growth rate and the factor limiting growth (NO3‐, NH4+, PO43‐or light) could alter C:ATP, RNA: ATP, C:chlaand RNA:chlaratios by amounts which were large compared to measurement error. An analysis of variance of the batch culture results indicated that both species and the source of inorganic nitrogen (NO3‐, or NH4+) had a significant effect on C:ATP and RNA:ATP ratios. Light had less of an influence on C:ATP and RNA:ATP ratios than on C:chlaand RNA:chlaratios, and for this reason we feel that phytoplankton C and RNA concentrations can be estimated with greater reliability from ATP than from chlameasurements. The range of C:ATP and RNA:ATP values found forT. weissflogiiunder a variety of growth conditions was similar to that for the six additional species grown in batch culture, suggesting that this range of values is indicative of the extremes likely to occur in living cells. Our results and additional data in the literature indicate that phytoplankton C and RNA concentrations can be estimated to within a factor of two by multiplying ATP concentrations by 311 and 35, respectively, in N limited systems, and by 341 and 36, respectively in PO43‐limited

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00439.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY