Formation of blooms by the symbiotic ciliate Mesodinium rubrum: the significance of nitrogen uptake

Mesodinium rubrum, a holotrichous ciliate that harbors endosymbioticchloroplasts, was responsible for patches of red water in thecoastal upweUing ecosystem at 15°S, Peru during March—May1977. Stations within red patches showed elevated concentrationsof paniculate nitrogen, chlorophyll a and dissolved organicnitrogen (DON), and lower concentrations of nitrate comparedwith areas where there were no ciliate blooms. These naturallyoccurring populations of M.rubrum took up nitrate, ammoniumand DON. Light was required for nitrate uptake and to a lesserextent for ammonium uptake. Dark uptake of ammonium occurredin all experiments. There was no effect of light on DON uptake.Possession of endosymbiotic chloroplasts enables this protozoanto use upwelled nitrate efficiently for development of largeblooms and concentrate into patches in the face of relativelystrong advective regimes.     

Photosynthetic pigments in the ciliate Laboea strobila from Long Island Sound, USA

Laboea sirobila Lohmann, a marine oligotrich ciliate, was presentin Long Island Sound, USA, from March through June 1984. Peakabundance occurred in mid-June, when it was estimated that 10.2x 10⁶ individuals m^–2 were present in the 37-m deep watercolumn. When preserved specimens were examined with epifluorescencemicroscopy, the photosynthetic pigments chlorophyll and phycoerythrinwere observed within chloroplasts inside the ciliate. Thesepigments were also present in Myrionecta (formerly Mesodinium)rubrum Jankowski, a photosynthetic ciliate which co-occurredwith L. strobila during the present study. Vertical profilesshowed both ciliates to be most abundant in the upper few metersof the water column, especially during periods of strong thermalstratification.     

The seasonal abundance of the phototrophic ciliate Mesodinium rubrum in Southampton Water, England

The abundance of the marine phototrophic planktonic ciliateMesodinium rubrum was monitored throughout an annual cycle attwo stations in the Southampton Water estuary. Seasonal changesin the concentration of nitrate, ammonia and phosphate weremonitored both at the inner estuary station (NW Netley) andouter estuary station (Calshot). Nutrient levels in the winterwere similar at both stations, and were diminished during sequentialdiatom blooms dominated initially by Sketetonema costatum andthen by Rhizosolenia dclicatula. Nitrate was reduced to a seasonalminimum in the outer estuary following these spring diatom blooms,but in the inner estuary was sustained >500 µg I^–1until the onset of the M.rubrum bloom. During the developmentof a visible red tide of M.rubrum in June/July at NW Netley,nutrient concentrations were considerably reduced. Cell numbersof M.rubrum varied between 2 and 3 cells ml^– during winterto >400 cells ml^–1 during the bloom at NW Netley, whereasat Calshot cell abundance did not increase above 25 cells ml^–1at any time of the year. At NW Netley, dense accumulations ofthe ciliate occurred over restricted depth intervals duringthe bloom and possible factors influencing the observed verticaldistribution of cells are considered. ¹Present address: Biology Department, Faculty of Science, AddisAbaba University, PO Box 1176, Addis Ababa, Ethiopia     

Red tide assemblage formation in an estuarine upwelling ecosystem: Ria de Vigo

Red tides are conspicuous in the upwelling system of Galicia(NW Iberian Peninsula). At present, there are conflicting hypothesesabout the generation site of these phytoplankton assemblages.It is interesting to know whether the rias can be sites of redtide formation or if they act only as accumulation sites ofpopulations advected from shelf waters. A study in the Ra deVigo, carried out during late September 1990, showed the developmentof a red tide assemblage, composed of Alexandrium affinis, Ceraiiumfusus and Gymnodinium catenaium, during a 2 week upwelling-downwellingcycle. Growth occurred at the bottom of the thermocline-topof the nutricline. Above this assemblage, a diatom assemblage(large diatoms) was blooming. Prior to the formation of thered tide, a subsurface chlorophyll maximum made up of smalldiatoms (Nilzschia f. seriaia, Chaeloceros socialis), smallflagellates (<30 µm) and small gymnodinid forms (<30µm) was observed. In the nutrient-depleted upper layer,several autotrophic and large heterotrophic dinoflagellatesdominated. It is suggested that the ratio between the velocityof upward water movement and the depth of the stratified upperlayer (flushing rate, day^–1) is the critical parameterwhich triggers active phytoplankton growth. It can be concludedthat upward water velocities of {small tilde}2.5 m day^–1and a stratified upper layer of 10 m depth (flushing rate 0.25day^–1) are the main physical constraints for red tidedevelopment.     

Effects of temperature and salinity on the growth of the red tide flagellates Heterocapsa circularisquama (Dinophyceae) and Chattonella verruculosa (Raphidophyceae)

Growth responses of the red tide flagellates, Heterocapsa circularisquama(Dinophyceae) and Chattonella verruculosa (Raphidophyceae),were examined with 36 different combinations of temperature(5–30°C) and salinity (10–35 PSU). Heterocapsacircularisquama did not grow at or below a temperature of 10°C.The maximum growth rate of H.circularisquama (1.3 divisionsday^–1) was obtained with a combination of 30°C and30 PSU. In contrast, C. verruculosa did not grow at 10 PSU andat temperatures of 25°C or more. The maximum growth rateof C. verruculosa (1.74 divisions day^–1) was obtainedwith a combination of 15°C and 25 PSU. A significant temperature-salinityinteraction on growth was found by factorial analysis. Basedon the physiological characteristics obtained in the presentstudy, these novel flagellates have a potential for future outbreaksof red tides in pre viously unaffected waters.     

The Growth of the Shoot Apex of Chenopodium rubrum L. Treated with a Florigenic Extract from Flowering Tobacco Plants: Preliminary Anatomical Observations

Anatomical changes in the shoot apex of Chenopodium rubrum L.treated with an extract from flowering tobacco plants and cultivatedin non-inductive conditions are described. They are comparedwith the anatomy of non-treated vegetative apices and with apicesof plants induced with a short day. Treatment with the extractresulted in both activation of cell division in the upper partof the apex and in apex elongation. Acceleration of leaf primordiainitiation and stimulation of branching took place. The effectcorresponds to the sequence of changes in photoperiodically-inducedplants but is more pronounced. Elongation following 10^–4M GA₃ treatment was of a differentnature; there was only a slight stimulation in the upper partof the apex in contrast with a strong stimulation of growthin length in the lower internodes. These preliminary resultssuggest a similarity between apical changes evoked by a stimulusproduced by short days and an exogenously applied floral stimulus.The changes differed from those caused by exogenous phytohormones. Key words: Chenopodium rubrum, florigen, shoot apex     

Phytoplankton photosynthesis parameters in central Canadian lakes

Values for two biological parameters — (i) P^B_m, the lightsaturated rate of photosynthesis per unit of chlorophyll and(ii) , the slope of the light limited part of the photosynthesisversus light curve per unit of chlorophyll — must be knownin order to be able to estimate rates of phytoplankton primaryproduction from chlorophyll data. These parameters were measuredfor periods of up to 9 years in central Canadian lakes locatedin temperate, subarctic and arctic climatic zones. Regardlessof their geographic locations, lakes where integral photosynthesiswas nutrient limited had lower values of these parameters thandid lakes where integral photosynthesis was light limited. Temperatureset an upper limit to the variability of P^B_m but was not a goodpredictor of its actual value. Year-to-year variability of photosynthesisparameters in the most intensively studied group of lakes waslarge: annual means varied by a factor of three over a 9-yearperiod. Until the sources and extent of this variability areknown, accurate production estimates can be obtained from chlorophylldata only if P^B_m and are measured in each water body and inevery year. Implications for estimating primary production fromremotely-sensed chlorophyll data are discussed.     

Ineffectiveness of cytokinin-induced chlorophyll retention in hypostomatous leaf discs

Kinetin retarded the decrease in chlorophyll content in leafdiscs from 5 species of plants with amphistomatous leaves, wherethe upper surface was exposed to air, but not in Rumex acetosera.When leaf discs were floated so that the lower surface was exposed,the effect of kinetin was less evident. Kinetin also stimulatedtranspiration in leaf discs from Nicotiana tabacum (amphistomatous),but not in leaf discs from Paederia chinensis (hypostomatous).Nor kinetin did retard chlorophyll breakdown in this specieswhen leaf discs were floated so that the stomatal surface wasin contact with the solution. The ineffectiveness of cytokininsin chlorophyll retention in leaf discs from hypostomatous leaveswas not due to reduced uptake of benzylaminopurine-¹⁴C. Chlorophyll retention was severely inhibited by coating theleaf surface with vaseline either in the presence or absenceof kinetin. Leaf discs floated on a solution exposed to CO₂-lessair retained more chlorophyll than those in normal air. Thereis thus a close relationship between stomatal opening (as measuredby stimulation of transpiration) and chlorophyll retention,as influenced by cytokinins. It is suggested that cytokinin-induced chlorophyll retentionand odier effects on leaf tissues could be mediated throughits effects on stomatal opening. (Received January 22, 1976; )     

Primary production and photoadaptation of phytoplankton in relation with tidal mixing in coastal waters

In the eastern English Channel (a coastal and shallow system),photosynthetic parameters of the pbytoplankton population weremeasured during 36 h at four depths, in a neap tide period.The vertical distilbutions of chlorophyll a (chl a), nutrients,and hydrodynamic properties were monitored during the cruise.Despite vertical homogeneity in salinity, chlorophyll a andnutrient profiles,a vertical gradient in both photosyntheticparameters (     

Further studies on ribulose-l,5-diphosphate carboxylase from Rhodopseudomonas spheroides and Rhodospirillum rubrum

Some enzymic properties of RuDP carboxylase isolated from Rhodopseudomonasspheroides and Rhodospirillum rubrum, grown under autotrophic,semi-autotrophic and heterotrophic conditions were studied.Regardless of the growing condition, the nature of the enzymefrom each respective bacterium remained unchanged. The molecularweight of R. spheroides and R. rubrum RuDP carboxylase was estimatedto be approximately 2.4x10⁵ and 8.3x10⁴, respectively. Bothenzymes require Mg⁺⁺. Their kinetic properties were also examined. ¹Part XII. Structure and Function of Chloroplast Proteins ²Supported in part by research grants from the Ministry of Educationof Japan (No. 8719), USPHS (AM. 10792-03) and the Asahi Press(Tokyo) (Received March 18, 1970; )     

Seasonal variation in the species composition of tintinnid cilates in Hiroshima Bay, the Seto Inland Sea of Japan

Seasonal changes in the species composition of tintinnid ciliateswere examined based on time-series samples taken at 2 week intervalsover a 3 year period in Hiroshima Bay, the Seto Inland Sea ofJapan. The maximum abundance of total tintinnids over the entireperiod was 5.7 x 10³ indi viduals l^– Among 32 speciesidentified, a consistent seasonal occurrence was recognizedin 22 species. The relationships between various environmentalfactors and the abundance of each species of tintinnids wereanalyzed using principal component analysis From this analysis,the abundance of many tintinnids was revealed to be associatedwith temperature, the <20 µm size fraction of chlorophylla and water column stability, but not with the <20 µmsize fraction of chlorophyll a, nor with salinity. From theseresults, tintinnid species were divided into five associationtypes: species whose abundance increased with increasing temperature,decreasing temperature, nanophytoplankton abundance, increasingwater column mixing, or increasing water stratification coupledwith low temperature.     

Growth Stage Modulates Salinity Tolerance of New Zealand Spinach (Tetragonia tetragonioides, Pall.) and Red Orach (Atriplex hortensis L.)

The response of two speciality vegetable crops, New Zealandspinach (Tetragonia tetragonioides Pall.) and red orach (Atriplexhortensis L.), to salt application at three growth stages wasinvestigated. Plants were grown with a base nutrient solutionin outdoor sand cultures and salinized at 13 (early), 26 (mid),and 42 (late) d after planting (DAP). For the treatment saltconcentrations, we used a salinity composition that would occurin a typical soil in the San Joaquin Valley of California usingdrainage waters for irrigation. Salinity treatments measuringelectrical conductivities (EC_i) of 3, 7, 11, 15, 19 and 23 dSm^-1were achieved by adding MgSO₄, Na₂SO₄, NaCl and CaCl₂to thebase nutrient solution. These salts were added to the base nutrientsolution incrementally over a 5-d period to avoid osmotic shockto the seedlings. The base nutrient solution without added saltsserved as the non-saline control (3 dS m^-1). Solution pH wasuncontrolled and ranged from 7.7 to 8.0. Both species were saltsensitive at the early seedling stage and became more salt tolerantas time to salinization increased. For New Zealand spinach,the salinity levels that gave maximal yields (C_max) were 0,0 and 3.1 dS m^-1and those resulting in a 50% reduction of biomassproduction (C₅₀) were 9.1, 11.1 and 17.4 dS m^-1for early, midand late salinization dates, respectively. Maximal yield ofred orach increased from 4.2 to 10.9 to 13.7 dS m^-1as the timeof salinization increased from 13, to 26, to 42 DAP, respectively.The C₅₀value for red orach was unaffected by time of salt imposition(25 dS m^-1). Both species exhibited high Na⁺accumulation evenat low salinity levels. Examination of K-Na selectivity dataindicated that K⁺selectivity increased in both species withincreasing salinity. However, increased K-Na selectivity didnot explain the increased salt tolerance observed by later salinization.Higher Na-Ca selectivity was determined at 3 dS m^-1in New Zealandspinach plants treated with early- and mid-salinization plantsrelative to those exposed to late salinization. This correspondedwith lower C_maxand C₅₀values for those plants. Lower Ca uptakeselectivity or lower Ca levels may have inhibited growth inyoung seedlings. This conclusion is supported by similar resultswith red orach. High Na-Ca selectivity found only in the early-salinizationplants of red orach corresponded to the lower C_maxvalues measuredfor those plants. Copyright 2000 Annals of Botany Company New Zealand spinach, Tetragonia tetragonioides Pall., red orach, Atriplex hortensis L., salinity, stage of growth, ion accumulation, selectivity, plant nutrition     

Effects of vertical-horizontal coupling on the horizontal distribution of chlorophyll a

The distributions of chlorophyll a and salinity were sampledon successive days along horizontal transects in central LongIsland Sound. Changes in the variance spectra over a periodof three days following a wind event suggest that there wasan input of variance at wave numbers of the order 6 ? 10^–3radians per meter. There was an associated increase in coherencysquared between chlorophyll and salinity. During this periodvertical structure in both chlorophyll and salinity was reestablished.It appears that horizontal structure was generated by the interactionof this vertical structure with a vertical shear in horizontalcurrents at semidiurnal and lower frequencies and possibly byshort period internal waves with frequencies near the V?is?l?frequency.     

Seasonal variations of bacterial abundance and biomass and their relation to phytoplankton in the hypertrophic tropical lagoon Cienaga Grande de Santa Marta, Colombia

The seasonal development of bacteria was studied in the hypertrophiccoastal lagoon Ciénaga Grande de Santa Marta (Caribbeancoast of Colombia). This large but only 1.5 m deep lagoon issubject to strong seasonal variations of salinity from almostfully marine (April/May) to brackish conditions in October/November.Chlorophyll ranged from 6 to 182 µg L^–1, and grossprimary production amounted to 1690 g C m^–2 per year.Total bacterial number (TBN) ranged from 6.5 to 90.5 x 10⁹ cellsL^–1 and bacterial biomass (BBM) from 77 to 1542 µgC L^–1, which are among the highest ever reported for naturalcoastal waters. Neither TBN nor BBM varied significantly withsalinity, phytoplankton or seston concentrations. Only the bacterialmean cell volume showed a significant relation to salinity,being highest (0.066 µm³) during the period of increasingand lowest (0.032 µm³) during decreasing salinity. Bacterialprotein accounted for 24% (19–26%) and phytoplankton proteinfor 57% (53–71%) of total seston protein. The ratio (annualmean) of bacterial carbon to phytoplankton carbon was 0.44 (range0.04–1.43). At low phytoplankton abundance [chlorophylla (Chl a) < 25 µg L^–1], bacterial carbon wasalmost equal to phytoplankton biomass (i.e. the mean ratio was1.04). In contrast, at Chl a > 100 µg L^–1, BBMwas low compared to phytoplankton biomass (the mean ratio was0.16). In general, BBM varied less than phytoplankton biomass.Most probably, the missing correlation between bacterial andphytoplankton variables was due to (i) organic material partlyderived from allochthonous sources serving as food resourcefor bacteria and (ii) a strong resuspension of bacteria fromthe sediment caused by frequent wind-induced mixing of the veryshallow lagoon.     

Abundance, frequency of dividing cells and growth rates of Synechococcus sp. (cyanobacteria) in the stratified Northwest Mediterranean Sea

The abundance, frequency of dividing cells and growth ratesof the planktonic cyano bacteria Synechococcus sp. during thesummer of 1995 and 1996 were estimated in the Northwest MediterraneanSea to test whether depth-dependent growth rates of this speciesexplain its dominance in the deep chlorophyll maximum (DCM)layer formed during summer thermal stratification in the NWMediterranean, compared to the surface layer. Abundance at theDCM layer (50–70 m) was up to two orders of magnitudegreater than that at the surface, with values ranging from 1.7to 13x10⁶ cells I-¹ and from 4 to 175 x 10⁶ cells I-¹ at thesurface and in DCM waters, respectively. Gross growth rates,however, were much higher at the surface than in the DCM layer(surface: 0.76–1.07 day DCM: 0.30–0.47 day-¹ Thehigher gross growth rates at the surface layer were supportedby a higher frequency of dividing cells (surface: 0.09–0.24;DCM: 0.01–0.12). The negative correlation between theabundance or standing stock and growth rates of these planktonicpicocyanobacteria points to losses, and not growth rate, asthe main control on the abundance of Synechococcus. Althoughwe provide some evidence that grazing alone may be able to accountfor these losses, further, direct determinations are clearlyneeded to elucidate the regulation of the abundance of Synechococcusin the NW Mediterranean.     

The Effects of {delta}-Aminolevulinic Acid and Inhibitors of RNA and Protein Synthesis on Phytochrome Mediated Chlorophyll Accumulation in Sorghum bicolor

In 5-d-old etiolated seedlings of Sorghum bicolor, 12 h of darknessafter 5 min in red light eliminated a lag before the accumulationof chlorophylls in subsequent continuous white light. Increasingthe dark period to 24 h and 36 h, increased the rate of chlorophyllaccumulation in the later stages of greening. Exogenous -aminolevulinicacid neither completely removed the lag, nor increased the rateof chlorophyll accumulation. Cycloheximide (25 µg ml^–1)and 6-methyl purine (5.0 µg ml^–1), given continuouslyor only until the 12 h dark period following the red light irradiation,restored the lag and decreased the rate of chlorophyll accumulation.D-threo-chloramphenicol (400µg ml^–1) also decreasedthe rate of chlorophyll accumulation but did not restore thelag. Addition of these inhibitors even 12 h after red lightirradiation decreased the rate of chlorophyll accumulation.Rifampicin (Rifamycin SV, 400 µg ml^–1) did not havesuch effects. Key words: Chlorophylls, Phytochrome, -Aminolevulinic acid, Sorghum bicolor     

Effects of Light on Degradation of Chlorophyll and Proteins during Senescence of Detached Rice Leaves

Regulatory effects of light on senescence of rice leaves wereinvestigated by measuring degradation of chlorophyll and proteinsin leaf segments which had been kept in the dark or under illuminationwith light of different intensities and colors. When leaveshad been left in total darkness for three days at 30°C,there was an initial long lag that lasted for one whole dayand then chlorophyll was rapidly degraded in the second andthird days. Breakdown of chlorophyll was strongly retarded bycontinuous illumination with white light of intensity as lowas 0.5 µmol photons m^–2 s^–1 but the effectof light decreased at intensities above 10 µmol photonsm^–2 s^–2. The initial lag and subsequent degradationof chlorophyll in the dark were little affected by illuminationwith red or far red light at the beginning of dark treatment.However, a brief illumination with red light at the end of thefirst and/or second day significantly suppressed degradationof chlorophyll during subsequent dark periods and the effectof red light was nullified by a short irradiation with far redlight. Thus, degradation of chlorophyll is regulated by phytochrome.Thylakoid membrane proteins and soluble proteins were also largelydegraded during three days in the dark. Degradation of membraneproteins such as the apoproteins of light-harvesting chlorophylla/b proteins of photosystem II and chlorophyll a-binding proteinsof reaction center complexes showed a long lag and was stronglysuppressed by illumination with weak white light. Thus, theloss of chlorophyll can be correlated with degradation of chlorophyll-carryingmembrane proteins. By contrast, light had only a weak protectingeffect on soluble proteins and ribulose-1,5-bisphosphate carboxylase/oxygenaserapidly disappeared under illumination with weak white light.Thus, breakdown of thylakoid membrane and soluble proteins aredifferently regulated by light. Artifacts which would be introducedby detachment of leaves were also discussed. ¹ Present address: Department of Applied Biology, Faculty ofScience and Technology, Science University of Tokyo, Yamazaki,Noda-shi, Chiba, 278 Japan. ² Present address: Department of Life Science, Faculty of Science,Himeji Institute of Technology, Harima Science Park City, Hyogo,678-12 Japan.     

CHLOROPHYLL AMOUNT AS AN INDICATOR OF MATTER PRODUCTIVITY IN BIO-COMMUNITIES

The data of chlorophyll amounts in diverse bio-communities arecompiled and discussed with reference to matter production. The chlorophyll amount in euphotic zone of lakes and oceanswas less than 1 g/m², mostly less than 0.1 g/m². In phytoplanktonblooms it was ca. 0.1–1 g/m². Large values of 5–20g/m² were obtained in the outdoor mass cultures of Chlorella,in which the high population density and chlorophyll contentof the alga were observed. In terrestrial higher plant communitiesthe chlorophyll amount (ca. 1–10 g/m²) was usually higherthan in aquatic phytoplankton communities. The largest (13.3g/m²) was obtained with an evergreen gallery forest in Thailand.The chlorophyll amount of desert bio-community could be expectedto be as high as that in water blooms. The maximum chlorophyll amount in bio-communities seems to attainup to 20 g/m² when the conditions are favorable. ¹ Dedicated to Prof. H. TAMIYA on the occasion of his 60th birthday. (Received December 25, 1962; )     

Green Light Drives CO2 Fixation Deep within Leaves

Maximal ^l4CO₂-fixation in spinach occurs in the middle of thepalisade mesophyll [Nishio et al. (1993) Plant Cell 5: 953],however, ninety percent of the blue and red light is attenuatedin the upper twenty percent of a spinach leaf [Cui et al. (1991)Plant Cell Environ. 14: 493]. In this report, we showed thatgreen light drives ¹⁴CO₂-fixation deep within spinach leavescompared to red and blue light. Blue light caused fixation mainlyin the palisade mesophyll of the leaf, whereas red light drovefixation slightly deeper into the leaf than did blue light.¹⁴CO₂-fixation measured under green light resulted in less fixationin the upper epidermal layer (guard cells) and upper most palisademesophyll compared to red and blue light, but led to more fixationdeeper in the leaf than that caused by either red or blue light.Saturating white, red, or green light resulted in similar maximal¹⁴CO₂-fixation rates, whereas under the highest irradiance ofblue light given, carbon fixation was not saturated, but itasymptotically approached the maximal ¹⁴CO₂-fixation rates attainedunder the other types of light. The importance of green lightin photosynthesis is discussed. ¹Supported in part by grants from Competitive Research GrantsOffice, U.S. Department of Agriculture (Nos. 91-37100-6672 and93-37100-8855).     

Respiratory electron transport system (ETS) activity in Spanish reservoirs: relationships with nutrients and seston

We examined the relationship between potential respiration rates,as measured by electron transport system (ETS) activity, standardizedat a defined temperature (ETS2O). and nutrients and sestonicparticles in a set of 101 Spanish reservoirs spannin a widerange of limnological characteristics. ETS activity ranged from0.009 to 31 31 µmol e^- 1^–1 h^–1 Among the nutrients,it was significantly correlated only with phosphorus, and onlyduring the stratification period. During this period, the bestregressor of ETS2O was the concentration of chlorophyll a (Chla),whereas during the mixing period the best regressor was particulateorganic nitrogen (PON), suggesting a greater contribution ofnon-algal sestonic particles to total metabolism. Both the meanETS20:PON ratio and the mean Chla:PON ratio increased systematicallywith increasing PON, indicating a lower relative contnbutionof detrital particles to total seston as trophic state increased.In contrast, the mean ETS20:Chla ratio was constant across therange of Chla. Vertical profiles of ETS2O. Chla and PON weremore coherent during the stratification period. when subsurfaceand metalimnetic peaks were frequent, than during the mixingperiod.