摘要:

ABSTRACTThere are many logistic difficulties associated with studying Antarctic marine algae and, as a consequence, the taxonomic information available is far from comprehensive and any generalizations should be regarded with caution. The Antarctic marine benthic flora is characterized by a low species richness. Biogeographical characteristics of the flora are outlined. There is a high degree of endemism, possibly around 35–40%. Other major floristic elements are a group of species with a distribution extending to Tierra del Fuego and subantarctic islands, a group spread through temperate regions of the Southern Hemisphere, and a cosmopolitan group. Ecological observations show that ice has a major effect on the occurrence and distribution of algae, and ecophysiological studies indicate that Antarctic macroalgae possess various adaptations to ice, low temperatures, and strongly seasonal light conditions. Possible trends in the evolution of the Antarctic benthic marine flora, including a reduction in species richness and the origins of biogeographical links with subantarctic and temperate regions of the Southern Hemisphere, are discussed in the context of tectonic and climatic changes over the past 100 million years. A comparison is made with studies on the evolution of shallow‐water marine fa

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00897.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe distribution of the dinoflagellate genusCeratiumSchrank (Dinophyceae) in the North Atlantic and adjacent seas was studied by a combination of new observations on a large number of plankton samples collected from the northeastern Atlantic and North Sea, data from cruises off the east coast of North America and Caribbean Sea, and reports in the literature of the past 90 years. Seventy species were recorded, and their distribution was examined by several methods. Distribution maps were plotted for all species, and from these the ranges of temperature tolerance were derived. The 240 sets of data, which took the form of lists of species present in 5° latitude / longitude blocks obtained from the new work and the published material, were analyzed by clustering and ordination multivariate techniques using the programs Twinspan and Decorana.Analysis of the individual species showed that surface water temperature is the most important factor determining distribution and the number of species in a particular area. Warm water and /or low latitudes have many more species than cold waters and/or high latitudes. For example, at 5°N there are on average 23 species per block, whereas at 60° N there are only 8 species. On the basis of this work, theCeratiumspecies are divided into Group 1, Arctic‐temperate species normally only found in water of less than 15°C; Group 2, cosmopolitan species, which are found virtually everywhere and are the species most likely to form blooms or “brown water”; Group 3, intermediate species, which extend into neither the coldest nor the warmest water; Group 4, temperate‐tropical species, which have a lower temperature boundary of 5°–12° C; Group 5, warm‐temperate‐tropical species with a lower temperature boundary of 14°–15°C; and Group 6, tropical species, which are rarely found in water of less than 20° C.Analysis of the sample sites also confirmed the predominant influence of temperature, and the Atlantic Ocean was divided into four biogeographical zones of which the boundaries follow isotherms of surface water temperature. Zone 1 consists of the Arctic and subarctic area, with the southern boundary closely following the 10° mean annual temperature (MAT) line. Zone 2 is an intermediate or cold‐temperate zone, of which the southern boundary follows the winter 10° C MAT isotherm or the similarly placed summer 15° isotherm. Zone 3 is the warm‐temperate or subtropical zone, which is very broad. The southern boundary closely follows the 25°C summer isotherm. Zone 4 is the tropical zone, where water temperature is never likely to be much less than 23°C. These findings are discussed in relation to experimental work and environmental observations. We suggest that the genusCeratiumprovides an excellent tool for defining ocean currents and temperature changes and may become of

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00905.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTTo interpret flow cytometric data that are routinely obtained on natural oceanic communities, 23 strains of photosynthetic picoeukaryotes belonging to four classes (Prasinophyceae, Chlorophyceae, Pelagophyceae, and Prymnesiophyceae) and six pigment types were investigated for their light scattering in the forward and right‐angle directions, chlorophyll fluorescence, and DNA content as measured by flow cytometry. Cell she was assessed by Coulter counter, and pigment composition was measured by reverse‐phase high‐performance liquid chromatography. The size and GC% of the nuclear genome of cultured picoeukaryotes was measured from the fluorescence of DNA‐specific dyes. Using these two parameters, we could discriminate species within pigment groups. DNA staining of preserved natural samples may also prove useful in discriminating cooccurring populations in situ as long as the communities are not too complex. Using the relationships that we established between size and light‐scattering properties of the cells, we estimated equivalent diameters of picoeukaryotes in natural populations to be between 1.3 and 2 μm. Chlorophyll a content was between 6 and 16 fg·cel−1as calculated from relationships that we established between chlorophyll a content and red fluorescence of the cultured strains. With respect to size, chlorophyll a content, and pigment composition,Pelagomonassp. strains (Pelagophyceae) appeared to be the most representative of the natural communities in subtropical ocean waters. In contrast, green coccoid strains, which often outcompete other strains in culture, might only be minor contributors to thes

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00922.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTTrichodesmium tenueWille (1904) was examined using transmission electron microscopy to determine the role of carbohydrate, phosphorus, and nitrogen storage in buoyancy regulation. Carbohydrate storage area (mean = 2.06 ± 0.61 [SE] μm2; 6.62% of total cell area) in negatively buoyant colonies (NBCs) was significantly higher (P<0.001) than in positively buoyant colonies (PBCs) (mean = 0.38 ± 0.06 μm2; 0.73%). Distinct diel periodicity of carbohydrate content was found in NBCs demonstrated by an increase from darkness to afternoon. Polyphosphate content was significantly higher (P<0.001) in NBCs, with a mean of 0.44± 0.10 μm2(1.54%), as compared to PBCs, with a mean of 0.14 ± 0.05 μm2(0.24%). Polyphosphate content increased in NBCs from morning to evening, and PBCs had a 10% decrease from morning to afternoon. Calculations indicated that averaged effects of polyphosphate on increased cell density is approximately 20% of that from carbohydrate accumulation. Density contribution due to ballast weight of carbohydrate and polyphosphate indicated that NBCs were 12 times more dense than PBCs. Mean area of cyanophycin granules (N storage) was not significantly different between PBCs and NBCs. In conclusion,Trichodesmium tenuecan regulate buoyancy by carbohydrate ballasting similar to that noted in limnetic cyanobacteria. Polyphosphate storage and possibly nitrogen storage products play a significant role in buoyancy reg

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00935.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTLipid content and lipid class composition were determined in stream periphyton and the filamentous green algaeCladophorasp. andSpirogyrasp, Sterols and phospholipids were compared to chlorophylla(chla) as predictors of biomass for stream periphyton and algae. Chlorophylla, phospholipids, and sterols were each highly correlated with ash‐free dry mass (AFDM)(r2>0.98). Stream periphyton exposed naturally to high light (HL) and low light (LL) had chlaconcentrations (μg chla‐mg−1AFDM) of 7.9± 0.7 and 12.4 ± 2.9, respectively, while the sterol concentrations of these HL and LL stream periphyton (1.6 ± 0.4) were not significantly different (P>0.05). Periphyton exposed to an irradiance of 300 μmol photons·m−2s−1in the laboratory for 60 h had 5.6 ± 0.55 μg chla·mg−1AFDM, but the same periphyton exposed to 2% incident light for the same amount of time had 11.0 ± 0.56 μg chla·mg−1AFDM. Sterol concentrations in these periphyton communities remained unchanged (1.5 ± 0.3 μg·mg−1AFDM), Similar results (i.e. changes in chlabut stability of sterol concentrations in response to irradiance changes) were also found forCladophoraandSpirogyrain laboratory experiments. Sterols can be quantified rapidly from a few milligrams of algae and appear to be a useful predictor of eukaryote biomass, whereas cellular levels of chlavary substantially with light conditions. Phospholipids (or phospholipid fatty acids) are considered to be a reliable measure of viable microbial biomass. Nevertheless, phospholipid content varied substantially and unpredictably among algae and periphyton under different light regimes. Irradiance also had a significant effect on storage lipids: HL Cladophora and HL periphyton had 2 × and 5 × greater concentrations of triacylglycerols, respectively, compared to their LL forms. HL and LL algae also differed in the concentration of several major fatty acids. These light‐induced changes in algal lipids and fatty acids have

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00943.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTWe report here on the characterization and isolation of two ecotypes ofChlorella vulgarisBeyerinck that coexist in wastewater reservoirs. One ecotype (C1) contains high amounts of chlorophyllb, is capable of autotrophic growth, and can utilize only a few organic solutes for growth. The second ecotype (C2) contains low amounts of chlorophyllb, requires vitamin B12, and can support its growth with a broad range of organic compounds. Of the two ecotypes, the latter showed slower growth rates when light was the sole source of energy. Cells of C2‐typeChlorellaattained higher photosynthetic activities than C1‐type cells at saturating irradiances. However, their low chlorophyll b content and lower light utilization efficiency suggest that C2‐typeChlorellacontains relatively low amounts of light‐harvesting antennae, a disadvantage in severely light‐limited ecosystems like wastewater reservoirs. We hypothesize that the twoChlorellatypes coexist by adopting different lifestyles: C1‐type cells rely largely on their photosynthetic potential for energy conservation and growth, whereas C2‐type cells may exploit their heterotrophic properties for

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00950.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTChanges in colony size (cell number per colony) ofAsterionella FormosaHass. were experimentally evaluated in relation to water temperature using two types of clones having colony sizes of four or eight cells. The clones were isolated from two different temperate freshwater lakes. Both clones showed the same general trend with changing temperature. Most of the colonies were normal in size at low temperatures, but colony size was twice as large at high temperatures. Variable colony sizes were present at low percentages. Colony separation occurred at the oldest connection within the colony after cell division. Culture experiments showed that the rates of specific growth and colony separation were balanced except for a rather short period of time when the temperature was changed. Optical and scanning electron micrography did not show any distinctive morphological structure at the point of connection except for porelli and mucilage pads. Seasonal changes in colony size ofA. formosaobserved in a freshwater lake are discussed based on these temperature results.

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00955.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe motile freshwater dinoflagellateGymnodinium bogorienseKlebs., which forms dense blooms in Jezre'el Valley water reservoirs (Israel) appears to be physiologically suited to exploit stratified environments, where it outcompetes all other phytoplankton types. The dense summer blooms (“red tides”) were found to be nitrogen‐limited. The algae's competitive advantage, however, cannot result from superior uptake capabilities: its Ks(μmol NH4·L−1) for NH4was higher and its Vmaxμmol NH4·mg chlorophyll a−1·h−1) was lower than other phytoplankton types commonly occurring in the region. The competitive advantage ofG. bogorienseprobably stems from other physiological capabilities: dark ammonia and phosphorus assimilation and the ability to undertake diel vertical migration cycles between the upper photic water layers during the day and nutrient‐rich deeper layers at night. These findings confirm the vertical nutrient retrieval hypothesis in migra

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00964.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTPhaeodactylum tricornutumandChaetocerossp. (Badllariophyceae),Isochrysis galbana(clone T‐Iso) andPavlova lutheri(Prymnesiophyceae),Nannochloris atomus(Chlorophyceae),Tetraselmissp. (Prasinophyceae), andGymnodinumsp. (Dinophyceae) were cultured at different extents of nutrient‐limited growth: 50 and 5% of μmax. The lipid content of the algae was in the range 8.3–29.5% of dry matter and was generally higher in the Prymnesiophyceae than in the Prasinophyceae and the Chlorophyceae. Increasing extent of phosphorus limitation resulted in increased lipid content in the Bacillariophyceae and Prymnesiophyceae and decreased lipid content in the green flagellatesN. atomusandTetraselmissp.The fatty acid composition of the algae showed taxonomic conformity, especially for the Bacillariophyceae, where the major fatty adds were 14:0, 16:0, 16:1, and 20:5n‐3. These fatty acids were dominant also in the Prymnesiophyceae together with 22:6n‐3. An exception wasI. galbana, in which 18:1 was the major monounsaturated fatty add and 20:5n‐3 was absent. The fatty acids ofN. atomusandTetraselmissp. varied somewhat, but 16:0, 16:1, 18:1, 18:3n‐3, and 20:5n‐3 were most abundant.Gymnodinumsp. contained mainly 16:0, 18:4n‐3, 20: 5n‐3, and 22:6n‐3. An increased level of nutrient limitation (probably phosphorus) resulted in a higher relative content of 16:0 and 18:1 and a lower relative content of 18:4n‐3, 20:5n‐3, and 22:6n‐3. The nutrient limitation probably reduced the synthesis of n

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00972.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe nature of transient ammonium uptake by the macroalgaUlva lactuca L.was studied from the depletion of ammonium after single additions of ammonium to batch cultures. The experiments were carried out by the application of two different experimental setups: the “multiple flask” and the “perturbation” techniques. Uptake rate was nonlinear with time, and three distinct, succeeding phases of uptake were identified: 1) “surge” uptake, i.e. transiently enhanced uptake that lasted for a few hours only, followed by 2) “internally” controlled uptake, a relatively constant phase occurring at high substrate concentrations, and finally 3) the “externally” controlled uptake phase, which was substrate‐dependent and occurred at low substrate concentrations. Surge uptake occurred over a broad range of substrate concentrations but was concentration‐dependent and, so, equalled externally controlled uptake rates at substrate concentrations below 3–10 μM. The transient nature of ammonium uptake rate seemed related to rapid changes in small intracellular pools of inorganic nitrogen or amino acids rather than to changes in total N content of the algae. The transient nature of ammonium uptake has important implications for the measurement of uptake rates when either of the two standard methods, the multiple flask and the perturbation technique, are used, and I recommend that a combination of the two methods be used for

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1994.00980.x

出版商:Blackwell Science Inc    

年代:1994

数据来源: WILEY