ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00723.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00730.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00737.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTThe responses of sea ice microalgae to variation in ambient irradiance (0 to 150 μE · m−2· s−1), temperature (–6° to + 6° C), and salinity (0 to 100 ppt) were tested to determine whether these variables act independently or in concert to influence rates of microalgal photosynthesis. The photosynthetic efficiency and maximum photosynthetic rate for sea ice microalgae increased as a function of incubation temperature between ‐6° and + 6° C. Furthermore, photosynthetic efficiency, maximum photosynthetic rate, and quantum yield were greatest at salinities between SO and 50 ppt. In contrast, the mean specific absorption coefficients were lowest near seawater salinities, and the saturating irradiance, Is, appeared to be inversely proportional to salinity. Results also suggest that the effects of salinity on the growth of sea ice microalgae are independent of those elicited by temperature or light, and that the functional relationship between salinity and light or temperature is multiplicative. This information is essential to the proper formulation of algorithms used to describe algal growth in environments where light, temperature, and salinity are changing simultaneously, such as within sea ice or within the water column at the marginal

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00746.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTCultures of the temperate estuarine diatom,Phaeodactylum tricornutumBohlin (NEPCC Clone 31), were grown under ambient intensities of ultraviolet‐A radiation (UVAR), photosynthetically active radiation (PAR), and various intensities of ultraviolet‐B radiation (UVBR; 290–320 nm). Growth rates and cell volumes were monitored for 36 d. UVBR decreased growth rates and increased cell volumes. Sensitivity of growth to UVBR increased with time. Growth rates ofP. tricornutumdecreased with increasing ratios of UVBR:UVAR

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00757.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTThein situfate of the toxic cyclic heptapeptides, the microcystins, produced by blooms ofMicrocystiswas examined at two stations in a hypertrophic Japanese lake. Microcystins were detected in all samples ofMicrocystiswith quantities varying seasonally and spatially (230–950 μg · g dry wt−1at St. 1 and 160–746 μg · g dry wt−1at St. 2) and composed of microcystin‐LR, ‐RR, and‐YR. Microcystin‐RR was the dominant toxin in most samples. A large amount of microcystin (1.1 μg · L−1) was detected in only one sample of filtered lake water. Accumulation of microcystin in zooplankton was indirectly estimated from a newly developed equation model. Large amounts of microcystin (75–1387 μg · g dry wt−1) were accumulated in the zooplankton community, which consisted of two cladocerans,Bosmina fatalisBurckhardt andDiaphanosoma brachyurumLieve, and a copepod,Cyclops vicinusUljanin, that co‐occurred with the toxicMicrocystisblooms. The maximum percent of microcystin content in zooplankton to that inMicrocystiswas 202%. Among the three species of zooplankton, onlyB. fatalisseemed to be responsible for accumulation of the microcystins becauseC. vicinusappeared to avoid contact withMicrocystiscells andD. brachyurumdid not consume colonies ofMicrocystis.Microcystins may be transferred to higher t

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00761.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTThe photosynthetic rates ofTrentepohlia odorata(L.) Martius growing on wall surfaces in Singapore changed throughout the day with a maximum in midmorning and decreasing thereafter during the day. Optimum temperature for photosynthesis was 25° C. Different levels of air humidity also affected photosynthetic rates with low relative humidity reducing the rates and efficiency of photosynthesis. Our results suggested thatT. odoratawas able to maximize its rate of photosynthesis before photoinhibitory light levels were reached and that its growth might be dependent on high levels of atmospheric relative humidity, which may serve as a source of water supply for the alga

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00768.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTDiatoms of the family Epithemiaceae possess a unicellular nitrogen‐fixing cyanobacterial endosymbiont. We investigated the potential of extracellular nitrogen and phosphorus concentrations to affect the endosymbiont load ofRhopalodia gibbaO. Müll, andEpithemia turgidaEhr. in field and culture populations. In a growth chamber experiment, monoclonal cultures ofR. gibbawere exposed to three levels of nitrate‐nitrogen. Nutrient‐diffusing substrates were used in a lake environment to create nine microhabitats of varying nitrogen and phosphorus ratios for natural populations ofR. gibbaandE. turgida.The number of endosymbionts per diatom increased as ambient nitrogen became limiting; mean endosymbiont volume increased as nitrogen increased. The mean endosymbiont surface area: volume ratio decreased with increasing nitrogen. Total endosymbiont volume per diatom (the product of the number of endosymbionts per diatom and their individual biovolumes) did not have a simple response to increasing nitrogen. Phosphorus limitation uncoupled the relationship between endosymbiont load and nitrogen. We suspect that flexibility of the endosymbiont load can reduce the metabolic cost to the diatom if the endosymbionts are dependent on the diatom for a re

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00773.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTA simple, nondestructive physical process was developed for routinely isolating the outermost layers from female, male, and sporophyte fronds ofChondrus crispusStack‐house. Yields of pure cuticles from apical segments ranged from 0.74 to 2.35% on a dry weight basis after 5–7 d of culture. These undegraded cuticles were examined by electron microscopy (scanning and transmission electron microscopy), spectroscopy (infrared and X‐ray), and chemical means.Cuticles isolated from female or male fronds were characterized by parallel arrays of electron‐dense lamellae (typically 6–14) alternating with more electron‐transparent regions. The thickness and uniformity of these lamellae provide the physical basis for the iridescence characteristic ofC. crispusfronds. Sporophyte fronds are not iridescent. This phenomenon may be explained by the fewer electron‐dense cuticular lamellae (usually three to seven) and the fact that these lamellae anastomose freely to form a thin cuticle with a highly irregular substructure. Elements detected by X‐ray analysis, in addition to carbon and oxygen, included Mg, Br, S, and Ca in both gametophyte and sporophyte cuticles. Major features of FTIR spectra of all cuticles were absorbances due to proteins. A strong band, indicative of sulfate ester, occurred near 1250 cm−1in all cuticle preparations. Gametophyte, but not sporophyte, cuticles absorbed at 935, 846, and 800 cm−1consistent with the presence of kappa and/or iota carrageenan. Amino acid analyses showed that sporophyte and gametophyte cuticles were generally similar in gross composition. All contained proline as the principal residue together with significant amounts of cysteine, methionine, and lysine. Protein contents calculated from these analyses ranged from 37.6 to 44.4% on a dry weight basis as compared to 51.5–56.7% calculated from total nitrogen values. Up to 75% of the cuticle mass was solubilized by sodium dodecyl sulfate‐β‐mercaptoethanol. Three similar migrating bands were seen in female and male cuticle extracts on sodium dodecyl sulfate–polyacrylamide gel electrophoresis; however, none of the three weaker bands from sporophyte cuticles comigrated with those from gametophytes. Chloroform‐methanol extraction removed<3.3% of the cuticle mass, suggesting tha

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00777.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTCells of the non‐N2‐fixing cyanobacteriumPhormidium laminosum(Agardh) Gomont (strain OH‐1‐pCl1) showed doubling times of 24 h in media containing nitrate and 120 h in media without a nitrogen source. Nitrogen starvation resulted in a drastic decrease in the cellular content of chlorophyll, phycobiliproteins (phycocyanin and allophycocyanin), and other soluble proteins, although the total protein of cells was unchanged. N‐starved cells showed an exocellular layer of mucilage that rapidly increased with starvation time. The appearance of N deficiency symptoms was strongly dependent on culture conditions, and it was faster under the optimal conditions used for cell growth. The relative content of C and N of nitrate‐grown cells remained more or less constant during all growth phases (C/N ratio of ca. 5) but diminished at different rates in N‐starved cells. Cells subjected to N starvation for 48 h had a C/N ratio of more than 10. N starvation also resulted in the selective degradation of soluble poly‐peptides of masses lower than 20 kDa (which include those constituting phycobiliproteins), whereas the relative content of soluble polypeptides of greater

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1992.00786.x

出版商:Blackwell Science Inc    

年代:1992

数据来源: WILEY