Adaptation of growth and photosynthesis to certain temperature regimes is an indicator for the geographical distribution of Cosmarium strains (Zygnematophyceae,Streptophyta)

In contrast to the many investigations on possible relationships between climate and geographical distributions in macroalgae, there are almost no similar studies regarding microalgae. In this study we consider the potential influence of temperature on patterns of distribution of six Cosmarium strains isolated from various climate zones that have been cultured long-term (> 15 years) in a relatively low temperature–low light regime. Growth and photosynthetic parameters, obtained from PAM fluorometry, were used to estimate the physiological characteristics of the strains during and after various temperature treatments. Acclimation to constant temperature and light conditions tended to affect photosynthetic parameters more than algal growth characteristics. However, all of the Cosmarium strains demonstrated physiological responses that were consistent with their source location under both low and high temperature conditions, confirming that such responses are genetically preserved. The Cosmarium strains displayed photosynthetic capacities and levels of the onset of saturation that repeatedly exceeded values recorded for other microalgae and seaweeds, indicating that these desmid strains are adapted to high light. This observation, as well as the relatively high growth temperature optima for all of the Cosmarium strains, provides some support for Coesel's hypothesis on the origin of desmids in the tropical zone. Interestingly, the Cosmarium strains used in this study demonstrated not only adaptive characteristics in accordance with the temperature prevailing at their sampling sites, but also with regard to their evolutionary origin.     

New and interesting desmids (Zygnematales, Chlorophyceae) collected from Brazil and Argentina

The morphology and taxonomy of nine desmid taxa belonging to the three genera Closterium, Euastrum and Cosmarium are studied based on freshwater algal collections from Brazil and Argentina. They represent five new varieties (Closterium cynthia De Notaris var. minutum Kanetsuna var. nov., Euastrum attenuatum Wolle var. saitoi Kanetsuna var. nov., Cosmarium laticollum Delponte var. minutum Kanetsuna var. nov., Cosmarium pseudovariolatum Grönblad var. major Kanetsuna var. nov. and Cosmarium taxichondrum Lundell var. yamagishii Kanetsuna var. nov.), two new forms (Euastrum hypochondrum Nordstedt var. hypochondrum f. divergens Kanetsuna f. nov. and Euastrum insulare (Wittrock) Roy var. silesiacum (Gronblad) Krieger f. brasiliense Kanetsuna f. nov.) and one new status (Cosmarium pseudovariolatum Gronblad var. incrassatum (Scott et Gronblad) Kanetsuna f. elonga‐tum (Scott et Gronblad) Kanetsuna stat. nov.). In addition, a new combination (Cosmarium pseudovariolatum Gronblad var. incrassatum (Scott et Gronblad) Kanetsuna comb, nov.) is proposed.     

DIFFERENT RESPONSE MECHANISMS OF TWO PLANKTONIC DESMID SPECIES (CHLOROPHYCEAE) TO A SINGLE SATURATING ADDITION OF PHOSPHATE

Two planktonic algal species, Staurastrum chaetoceras (Schr.) G. M. Smith and Cosmarium abbreviatum Rac. var. planctonicum W. et G. S. West, from trophically different alkaline lakes, were compared in their response to a single saturating addition of phosphate (P) in a P-limited growth situation. Storage abilities were determined using the luxury coefficient R = Q_max/Q₀. Maximum cellular P quotas differed, depending on whether cells were harvested during exponential growth at μ_max (Q_max, R being 26.7 and 9.1 for C. abbreviatum and S. chaetoceras, respectively) or harvested after a saturating pulse at P-limited growth conditions (Q′_max, R being 53.5 and 20.2 for C. abbreviatum and S. chaetoceras, respectively). At stringent P-limited conditions, maximum initial uptake rates were higher in S. chaetoceras than in C. abbreviatum (0.094 and 0.073 pmol P·cell^?1·h^?1, respectively), but long-term (net) uptake rates (over ～20 min) were higher in C. abbreviatum than in S. chaetoceras (0.048 and 0.019 pmol P·cell^?1·h^?1, respectively). Before growth resumed after the onset of a large P addition (150 μmol·L^?1), a lag phase was observed for both species. This period lasted 2–3 days for S. chaetoceras and 3–4 days for C. abbreviatum, corresponding with the time to reach Q^′_max. Subsequent growth rates (over ～10 days) were 0.010 h^?1 and 0.006 h^?1 for S. chaetoceras and C. abbreviatum, respectively, being only 20%–30% of maximum growth rates. In conclusion, S. chaetoceras, with a relatively high initial P-uptake rate, short lag phase, and high initial growth rate, is well adapted to a P pulse of short duration. Conversely, C. abbreviatum, with a high long-term uptake rate and high storage capacity, appears competitively superior when exposed to an infrequent but lasting pulse. These characteristics provide information about possible strategies of algal species to profit from temporarily high P concentrations.     

COMPETITION FOR PHOSPHORUS AMONG PLANKTONIC DESMID SPECIES IN CONTINUOUS-FLOW CULTURE1

When grown under stringent P limitation, affinity for P uptake and growth in Staurastrum pingue Teil. and Staurastrum chaetoceras (Schr.) G. M. Smith (both originating from eutrophic lakes) were of the same magnitude, whereas these parameters for Cosmarium abbreviatum Rac. var. planctonicum W. & G. S. West (isolated from a meso-oligotrophic lake) were significantly higher in value. On the other hand, at all growth rates tested, maximum P uptake rates were lower in C. abbreviatum than in the two Staurastrum species. The outcome of competition between either Staurastrum species and C. abbreviatum in mixed chemostats under different levels of continuous P limitation was in agreement with what could be predicted from the species-specific affinity parameters: Staurastrum was outcompeted at dilution rates lower than 0.012 h^?1, calculated to correspond with external inorganic P concentrations lower than 0.02 μM P, but won out at higher dilution rates. When P was added in two pulses of 2.5 μmol · L^?1 a week instead of continuously, S. chaetoceras outcompeted C. abbreviatum at a slow rate. When P was supplied as a daily pulse of 0.7 μmol · L^?1, a stable coexistence of S. chaetoceras and C. abbreviatum was established, Staurastrum predominating the culture in cell numbers at ca. 85%. The results show that P uptake and growth characteristics of the three species can predict the outcome of competition under various P-limited conditions. Specific growth kinetic parameters as found in this study may also explain distribution patterns of the species observed in the field.     

SEASONAL CHANGES IN THE PROXIMATE AND FATTY ACID COMPOSITION OF SOME NATURALLY GROWN FRESHWATER CHLOROPHYTES1

The protein content of the filamentous Cladophora glomerata (L.) Kz., Ulothrix zonata (Web, & Mohr) Kz. and Spirogyra sp., collected from natural populations for 1 year, averaged 8.0–12.4% of the total dry weight; whereas, the corresponding levels of lipid, cellulose and ash were 11.9–16.1%, 10.0–17.8% and 14.6–24.0%, respectively. Mean values for carbohydrates, estimated by difference, ranged from 32.8 to 56.0%. The colonial Scenedesmus dimorphus (Turp.) Kz. and the unicellular Cosmarium laeve Rab., on the other hand, contained more protein, lipid and carbohydrate (estimated by difference) averaging 13–15.0%, 22.5–25.9% and 415–46.8%, respectively, and less cellulose (7.5–9.8%) and ash (8.2–9.8%). A consistent pattern of seasonal variation in the proximate composition was not normally evident for any species, reflecting the influence of several environmental parameters on the algae. Cladophora contained the greatest amount of phospholipid averaging; 10% by weight of total lipid with the smallest quantity (5%) in Scenedesmus. The predominant phospholipid fatty acid in all species was C_18:1 followed by C_18:2, C_18:3 and C_16:1 in Cladophora, Ulothrix and Spirogyra, and C_16:1, C_18:2 and C_16:0 in Scenedesmus and Cosmarium. Oleic (C_18:1) and hexadecanoic (C_16:1) acids were predominant in the neutral lipids of all the algae, followed by C_16:0, C_18:2 and C_18:3. The concentration of the different fatty acids of each Species varied considerably during the year with the proportion of C_16:0 and C_16:1, usually rising and that of C_18:1 failing during the colder months.     

黑龙江扎龙国家级自然保护区鼓藻类植物中国新记录

于2011年5月(春季)、7月(夏季)和10月(秋季),先后3次对黑龙江扎龙国家级自然保护区进行鼓藻类植物调查,并对采集到的57份标本进行鉴定。结果发现,有6个分类单位为鼓藻类植物中国新记录,隶属于5个属,分别为:微小胶球鼓藻(Cosmocladium pusillum Hilse),中凹鼓藻(Cosmarium medioretusum Coesel),近前膨胀鼓藻锥形变种(Cosmarium subprotumidum var.pyramidale Coesel),双孢辐射鼓藻美国变种[Actinotaenium diplosporum var.americanum(West et West)Teiling],双臂角星鼓藻优美变种[Staurastrum bibrachiatum var.elegans(West et West)Prescott],冠毛多棘鼓藻钩状变种波兰变型(Xanthidium cristatumvar.uncinatumf.polonicumGutwingski)。     

COMPETITION FOR PHOSPHORUS BETWEEN DESMIDS1

During competition for phosphate in continuous cultures, Cosmarium subcostatum Nord. routinely displaced Staurastrum paradoxum Meyer. The rate of displacement was independent of cell density between 100 and 6000 cells mL^?1. This suggests that competition for nutrients is important over a wide range of naturally occurring cell densities. C. subcostatum had higher saturated rates of phosphate uptake but also higher half saturation values for uptake. As a result, the two desmids were similarly able to take up phosphate at low concentrations. The competitive advantage of C. subcostatum lay in its greater yield per unit of phosphorus. Growth of the two algae in shared medium in a dual-chamber chemostat had no effect on uptake or yield characteristics.     

大兴安岭阿尔山沼泽鼓藻类中国新记录

大兴安岭阿尔山是我国沼泽分布最集中的地区之一,其中鼓藻类植物十分丰富。2004年7月,2005年8月、10月和2006年5月,作者先后4次在该地区采集标本共260号,在对标本鉴定过程中,发现有中国新记录鼓藻10个分类单位,隶属于4个属,包括8种2变种:厚皮鼓藻加厚变种Cosmarium pachydermumvar.incrassatum、穿孔鼓藻C.perforatum、伸长鼓藻C.protractum、具齿角星鼓藻Staurastrum denticulatum、不等角星鼓藻S.dispar、分叉角星鼓藻具螺纹变种S.furcigerumvar.armigera、近阿维角星鼓藻S.subavicula、近十字角星鼓藻S.subcruciatum、超凡叉星鼓藻Staurodesmus insignis和孟它凹顶鼓藻Euastrum montanum。     

中国鼓藻目新资料

本文报道浙江省东钱湖和西湖鼓藻目8个属的1个新种、3个新变种、20个中国新记录种及变种。