ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00889.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTLaboratory and field experiments were done hi Still‐water Cove, Carmel Bay, California, and Monterey Harbor, California, to determine the effect of photosynthetically active radiation (PAR) on the shallow (upper) limit of giant kelp,Macrocystis pyrifera(L.) C. Agardh. At shallow depths,M. pyriferadid not recruit or grow to macroscopic size from gametophytes or embryonic sporophytes transplanted to vertical buoy lines; sharp decreases in PAR with depth coincided with observed recruitment and sporophyte distributions. Shade manipulations indicated that settlement ofM. pyriferazoospores was decreased, but not prohibited, by high PAR. Postsettlement stages (gametophytes and embryonic sporophytes), however, survived only under shade. These results suggest that high PAR can inhibit the recruitment ofM. pyriferato shallow water by killing its postsettlement stages; whether or not ultraviolet (UV) radiation also inhibits recruitment was not tested. In either case, however, it appears that high irradiance (PAR and/or UV) regulates the shallow limit ofM. pyriferaprior to temperature and desiccation stresses inherent to intertidal regions. In an additional experiment, recruitment or growth of transplanted gametophytes or embryonic sporophytes ofMacrocystis integrifoliaBory also did not occur at shallow depths, suggesting that this shallow water species accesses high irradiance regions via a method other than sexual reproductio

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00903.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTNitrogen uptake studies were conducted during an aestival “brown tide” bloom in Shinnecock Bay, Long Island, New York. The same station was sampled in late July and mid‐August 1995 whenAureococcus anophagefferenscomposed>90% and 30–40% of the total cell density, respectively. Experiments were designed to examine the effect of incubation duration on the uptake kinetics, and the effect of light and temperature dependencies of NH4+, urea, and NO3−uptake. Maximum specific uptake rates (V'max) decreased in the order NH4+, urea, NO3−and were nonlinear with time for NH4+and urea, both of which exhibited an exponential decline between 1 and 10 min and then did nut significantly change for 60 min. Nitrogen uptake kinetic experiments exhibited a typical hyperbolic response for urea and NO3−. Half‐saturation constants. (Ks) were calculated to he 0.03 and 0.12 μmol · L−1for urea and NO3−; respectively, but could not be calculated for NH4+under these experimental conditions. Nutrient uptake rate versus, irradiance (NI) experiments showed that maximum uptake rates occurred at≤%of incident irradiance on both sampling dates and that values of V′max‐cell(NH4+) were on average 30% greater than V′max‐cell(urea). A7°–9°C temperature decrease in incubation temperature between the two NI experiments in August resulted in a 30% decrease in V′max‐cell(NH4+), no change in V′max‐cell(urea), and a 3–4‐fold decrease in calculated Kltvalues for both NH4+and urea. The results from these experiments demonstrate thatA. anophagefferenshas a higher affinity for NH4+and urea than for NO3−and that this particular species is adapted to use these substrates at low irradiances and concentrations. The data presented in this study are also consistent with the hypothesis thatA. anophagefferensmay be an oceanic clone that

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00907.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTTrichodesmiumsp. IMS 101, originally isolated from coastal western Atlantic waters by Prufert‐Bebout and colleagues and maintained in seawater‐based media, was successfully cultivated in two artificial media. Its characteristics of growth, nitrogen fixation, and regulation of nitrogen fixation were compared to those of natural populations andTrichodesmiumsp. NIBB 1067. Results indicate that the culture grown in artificial media had nitrogen fixation characteristics similar to those when the culture is grown in seawater‐based medium and to those ofTrichodesmiumsp. in the natural habitat. The study provides practical artificial media to facilitate the physiological studies of these important diazotrophic cyanobacteria, as well as the cultivation of otherTrichodesmiumspecies in future studies. Manipulations of the light/dark cycle were performed to determine whether or not the daily cycle of nitrogen fixation is a circadian rhythm. Cultures grown under continuous light maintained the cycle for up to 6 days. We demonstrated that the daily cycle of nitrogen fixation inTrichodesmiumsp. IMS 101 was at least partially under the control of a circardian r

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00916.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTA virus infecting the haptophytePhaeocystis pouchetii(Hariot) Lagerheim was isolated from Norwegian coastal waters in May 1995 at the end of a bloom of this phytoplankter. The virus was specific forP. pouchetiibecause it did not lyse 10 strains ofP. globosaScherffel,Phaeocystissp., andP. antarcticaKarsten. It was a double‐stranded DNA virus, and the viral particle was a polyhedron with a diameter of 130–160 nm. The virus had a main polypeptide of about 59 kDa and at least five minor polypeptides between 30 and 50 kDa. The latent period of the virus when propagated in cultures ofP. pouchetiiwas 12–18 h, and the time required for complete lysis of the cultures was about 48 h. The burst size was estimated to be 350–600 viral particles per lys

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00923.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTTo better determine the ecological role of motility in pennate diatoms, we quantitatively characterized several motility and adhesion properties of four species of motile pennate diatoms(Craticulasp.,Pinnulariasp.,Nitzschiasp., andStauroneissp.)isolated from the same freshwater pond. Using computer‐assisted video microscopy, we measured speed, size/shape, functional adhesion, path curvature, and light sensitivity for these species, each of which shows a distinctive set of motile behaviors. The average speeds ofStauroneis, Pinnularia, Nitzschia, andCraticulacells are 4.6, 5.3, 10.4, and 10.0 μm · s−1, respectively.CraticulaandNitzschiacells move in a relatively straight path (1 day forNitzschiaandStauroneis.Direction reversal at light/dark boundaries, which appears to be the main contributor to diatom Phototaxis, is most responsive forCraticula, Pinnularia, andNitzschiaat wavelengths around 500 nm.CraticulaandNitzschiacells are the most sensitive in the photophobic response, with over 60% of these cells responding to a 30‐1x light/dark boundary at 500 nm, whereasPinnulariacells are only moderately responsive at this irradiance, showing a maximal response of approximately 30% of cells at 450 nm.Stauroneiscells, in contrast, had a maximal photosensitive response at 700 nm, suggesting that this cell type may use a different response mechanism than the other three cell types. In addition,CraticulaandPinnulariashow a net movement out of the light spot when illuminated at 650 nm, whereasStauroneisshows a net movement out of the light spot when illuminated at 450 nm. Such quantitative characterizations of species‐specific responses to environmental stimuli should give us a firm foundation for future studies analyzing the behavior of interspecies diatom competition for limited light or nutrie

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00928.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTWhen grown under stringent P limitation, affinity for P uptake and growth inStaurastrum pingueTeil. andStaurastrum chaetoceras(Schr.) G. M. Smith (both originating from eutrophic lakes) were of the same magnitude, whereas these parameters forCosmariumabbreviatum Rac. var.planctonicumW.&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 inC. abbreviatumthan in the twoStaurastrumspecies. The outcome of competition between eitherStaurastrumspecies andC. abbreviatumin mixed chemostats under different levels of continuous P limitation was in agreement with what could be predicted from the species‐specific affinity parameters:Staurastrumwas 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−1a week instead of continuously,S. chaetocerasoutcompetedC. abbreviatumat a slow rate. When P was supplied as a daily pulse of 0.7 μmol · L−1, a stable coexistence ofS. chaetocerasandC. abbreviatumwas established,Staurastrumpredominating 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 obser

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00939.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTChironomid larvae incorporate pieces of freshwater red algae into their cases from a wide geographic range in North America, extending from southern Canada to central Mexico. The Rhodophyta used in this process represent two orders (Acrochaetiales and Batrachospermales), five genera(Audouinella, Batrachospermum, Lemanea, Paralemanea, andSirodotia), and 14 species from 21 locations. Three genera from the chironomid subfamily Orthocladiinae make these cases: Cardiocladius, Eukiefferiella, andOrthocladius.TheEukiefferiella claripennisgroup was the most frequently observed infrageneric taxon using red algae in its cases. The cases were tubular in shape with longitudinally oriented strips of algae held together by silken threads. Some of the cases constructed withBatrachospermumandSirodotiaalso had several lateral branches of the alga radiating from the tube.

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00949.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTGrowth ofEuglena gracilis ZPringsheim under photoheterotrophic conditions in a nitrogen‐deprived medium resulted in progressive loss of chloroplastic material until total bleaching of the cells occurred. Biochemical analysis and ultrastructural observation of the first stages of the starvation process demonstrated an early lag phase (from 0 to 9 h) in which cells increased in size, followed by a period of cell division, apparently supported by the mobilization of some chloroplastic proteins such as the photosynthetic CO2‐fixing enzyme ribulose‐1,5‐bisphosphate carboxylase/oxygenase. The degradation of the enzyme started after 9 h of starvation and was preceded by a transient concentration of this protein in pyrenoidal structures. Protein nitrogen and photosynthetic pigments as well as number of chloroplasts per cell decreased during proliferation through mere distribution among daughter cells. However, after 24 h, when cell division had almost ceased, there was a slow but steady decline of photosynthetic pigments. This was paralleled by observable ultrastructural changes including progressive loss of chloroplast structure and accumulation of paramylon granules and lipid globules in the cytoplasm. These findings reinforce the role of chloroplastic materials as a nitrogen source during starvation ofE. gracilisin a carbon‐rich medium. The excess of ribulose‐1,5‐bisphosphate carboxylase/oxygenase acts as a first reservoir that, once exhausted, is superseded by the generalized disassembly of the photosynthetic structures, if the adverse environment persists m

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00953.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTTo identify processes that might account for differences in growth rates of rhodophytes under constant and dynamic light supply, we examined nonequilibrium gas exchange by measuring time courses of photoinduction, loss of photoinduction, and respiration rates immediately after the light–dark transition. Using the rhodophyte speciesPalmaria palmata(Huds.) Lamour andLomentaria articulata(Huds.) Lyngb., we compared the effects of growth‐saturating constant photon flux density (PFD) (95 μmol photons · m−2· s−1) to those of a dynamic light supply modeled on canopy movements in the intertidal zone (25 μmol photons · m−2· s−1background PFD plus light flecks of 350 μmol photons · m−2· s−1, 0.1 Hz). The time required forP. palmataandL. articulatato be fully photoinduced was not affected by the dynamics of light supply.L. articulatarequired only 6 min of illumination with either fluctuating or constant light to be completely induced compared to 20 min forP. palmata.The latter species also lost photoinduction more rapidly than didL. articulatain the dark. There was no significant decline in photoinduction state for either species at the background PFD. The time courses of respiration after illumination with constant and fluctuating light were significantly different forP. palmatabut not forL. articulatawhen the total photon dose was equal. In general, gas exchange ofP. palmataappeared to be particularly sensitive to the temporal distribution of light supply whereas that ofL. articulatawas sensitive to the amplitude of variations, being photoinhibited at high PFD. These results are discussed in terms of the different mechanisms of inorganic carbon acquis

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00963.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY