摘要:

ABSTRACTIn dense monospecific stands of plants intraspecific competition usually results in self‐thinning, the concurrent increase in biomass and decrease in density over time. Self‐thinning may also result in a change in the spatial pattern of individuals, but so far the spatial dynamics of marine plants has not been investigated. The brown algaHimanthalia elongata (L.) S. F. Gray forms dense monospecific stands on many northern temperate rocky shores, and various attributes (including its simple form) facilitated the study of the spatial dynamics of this species.The spatial pattern of settling zygotes was examined in the laboratory. In the absence of water movement, substratum heterogeneity, and a point source, zygotes usually settled in clumps rather than randomly. Within the clumps zygotes appeared to be regularly distributed at a scale similar to the size of the zygotes themselves. Furthermore, the clumps themselves seemed to be regularly distributed. On the shore, well‐established stands of “button‐stage”Himanthaliapopulations were examined during a period of extensive growth and self‐thinning. Individual plants were initially highly regular in spatial pattern but became less so over time. The pattern of plants dying during self‐thinning was also highly regular and probably reflected existing spatial regularity. However, using a hypothesis of mortality as a random event, I found that smaller plants had a less than average survival potential, while larger plants had a greater than average chance. A consideration of the spatial pattern of plants alive at the end of the study revealed regularity at a scale of 2–7 mm but a random spatial pattern at larger scales, which might indicate a small sphere of influence of competing individuals. The best predictor of mean nearest neighbor distances in the populations was me

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1995.00851.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTThe marine algaHeterosigma carteraeHulburt (Raphidophyta) was grown in N‐limiting batch cultures using either nitrate or ammonium as the N source, at photon flux densities (PFDs) of 50, 200, and 350 μmol·m‐2·s‐1in a 12:12 h LD cycle. Carbon content could be estimated from biovolume (μg C = 0.278 × nL;R =0.98) but not reliably from pigment content. During exponential growth, ammonium‐grown cells (in comparison with nitrate‐grown cells at the same PFD) attained higher growth rates by at least 20%, contained more N, and had a lower C:N ratio, higher concentrations of intracellular free amino acids, and higher ratios of glutamine: glutamate (Gln: Glu) and asparagine: aspartate (Asn:Asp). Growth was nearly light‐saturated on ammonium at 200 μmol·m‐2·s‐1(cell‐specific growth rate of 1.2 d‐1) but probably not saturated in nitrate‐grown cells at 350 μmol·m‐2·s‐1. PFD did not affect Gln: Glu or Asn: Asp for a given N source. These results indicate that the nitrate‐growing cells were more N‐stressed than those using ammonium (which in contrast were relatively C‐stressed) and that this organism would show an enhanced competitive advantage against other species when supplied with a transi

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1995.00859.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTPhotosynthetic pigments, C, N, and P tissue composition, and photosynthetic rate were measured from April to October in the brown algaPhyllariopsis purpurascens (C. Agardh) Henry et South (Laminariales, Phaeophyta) growing at a 30‐m depth in the Strait of Gibraltar. Ir‐radiance reaching the population ranged from 13.5 to 27.5 mol.m‐2.mo‐1. The available light for this species, expressed as a percentage of the irradiance above the water, was 1.8%. Dissolved inorganic nitrogen forms, NO3‐and NH4+, were constant from April to October, whereas phosphate was depleted in August. Chlorophylladecreased from 520.0 ± 165.0 to 199.6 ± 159.9 μg.g‐1dry weight; in contrast, chlorophyll c and carotenoids did not change until September but increased threefold in October. C:N and N:P ratios changed in the same way and in the same range. They were constant until July but increased from 15–17 up to 42 (C:N) and from 14 to 40 (N:P) in October, suggesting a severe P limitation of growth of this species. The dark respiration rate and the light compensation point were constant from April to October (0.5 ± 0.1 μmol O2. m‐2.s‐1and 6.5 ± 0.2 μmol.m‐2.s‐1, respectively), whereas the maximum rate of apparent photosynthesis, light onset saturation parameter, and half saturation constant for light were maximum in April to May (3.7 μmol O2. m‐2.s‐1and 40 and 41.5 μmol.m‐2. s‐1, respectively) and October (3.6 μmol O2. m‐2.s‐1and 50 and 53.7 μmol.m‐2. s‐1, respectively). They were minimum in August (1.2 μmol O2.m‐2.s‐1and 11.3 and 12 μmol.m‐2.s‐1, respectively). These minimum figures yielded a negative carbon budget in August and 0 in September, whereas it was positive the rest of the year. Photosynthetic efficiency, estimated by the ratio between maximum apparent photosynthesis and light half saturation constant, showed a strong agreement with productivity measured by means of an independent method. These results indicate that lamina expansion

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1995.00867.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTExperiments were undertaken in a recirculating flume to determine the relationships among water velocity, thallus area, drag, and the probability of thallus breakage or detachment in the foliose green algaUlva lactucaL. In all specimens tested to breaking point, thalli detached from their bivalve substrates as a result of stipe breakage rather than in midthallus or by holdfast detachment. There was no relationship between thallus size and drag at which detachment occurred. Rather, the probability of detachment was normally distributed about a mean drag of 0. 70 N (95% confidence limits 0.55–0.85 N). Average breaking stress of stipes was 345 kN.m‐2(95% cl 250–485 kN.m‐2). Similar results were obtained in field experiments where the horizontal force required to detach thalli was measured directly as 0.93 N (95% cl 0.69–1.15 N). Drag coefficients of plants were not constant with water velocity but increased up to 0.4 m.s‐1, declining exponentially at velocities above this. Empirical relationships were established between coefficient of drag and Reynold's number and, hence, among drag, thallus area and water velocity. These relationships permitted estimation of mean water velocity at which plants of a given area w

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1995.00875.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTEight diatom species(Chaetoceros pseudocurvisetusMang., Stephanodiscus hantzschiiGrun., Skeletonema costatum (Grev.) Cleve, Asterionella formosaHass., Thalassiosira nordenskioeldiiCleve, Detonula confervacea (Cleve) Gran, Chaetocerossp., andNitzschia frigidaGrun.) were isolated from various temperature environments ranging from temperate to the Arctic, and their growth responses to temperature were determined. Each species grew over a different temperature range. The lower and upper limits of each species varied from −1.8° to 20° C and from 2° to 30° C, respectively. The width of the growth range of each species. also varied from 3.8° to 25° C, and the growth of these species was observed, as a whole, between a wide temperature range from −1.8° to 30° C.Within the growth temperature ranges, the growth rate of each species increased with temperature until reaching a maximum, which was followed by a steep decrease up to the upper limit of the growth range. As a result, each species showed a maximum rate at the temperature very near to the upper limit, which was generally higher than the isolation temperature. The specific growth rates were compared among the eight species. The interspecific maximum rate at each temperature exhibited an exponential increase with a Q10=1.48. The relative growth rates of each species were calculated by normalizing the specific growth rates with the interspecific maximum rate at each respective temperature. The higher relative growth rates tended to occur at the isolation temperature of each species, suggesting that temperature is a significant control on species distribution

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1995.00880.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTCases of larvae and pupae from six caddisfly (Insecta, Trichoptera) genera in three families from North America were observed to contain pieces of freshwater rhodophyte thalli. Seven genera of Rhodophyta, representing 13 species and 35 populations, were observed in this association. Four of the 25 species ofBatrachospermumwere incorporated into cases ofOchrotrichia (Hydroptilidae) andAgrypnia (Phryganeidae). Two of the three freshwater species ofBostrychiawere used byOchrotrichialarvae. BothCompsopogon coeruleus (Balbis) Mont. andC. prolificusYadava et Kumano were present in the cases ofHydroptial (Hydroptilidae) andOchrotrichia; Compsopogonopsis leptocladus (Mont.) Krishnamur‐thy was observed in the cases ofHydroptila.The more cartilaginous thalli ofLemanea fluviatilis (L.) C. Ag. andTuomeya americana (Kütz.) Papenfuss were used by the brachycentrid larvae ofBrachycentrusandMi‐crasema. LemaneaandParalemaneaspp. were also in the cases ofDibusa angataRoss (Hydroptilidae). The architecture of each caddisfly case was studied with light and scanning electron microscopy. Strips of algae were fit together in a transverse, concentric, or spiralled fashion. Based on transmission electron micrographs, cortical cells ofLemaneaandTuomeyain the cases ofBrachycentrusandMicrasemaappeared to be healthy with intact chloroplasts and typical batrachospermalean pit plugs. Geographic distributions of each rhodophyte‐caddisfly association are

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1995.00889.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTPhotosynthetic activity, chloroplast enzymes, and poly‐peptides were compared in green and red (ketocarotenoid‐containing) cultures of the microalgaHaematococcus pluvialisFlotow. Green cultures, grown at 80 μmol pho‐tons.m‐2. s‐1in an acetate‐containing medium, had a mean generation time of 27 h. Ketocarotenoid accumulation was induced by transfer of green cultures to PO4‐deficient medium and exposure to 250 μmol photons.m‐2.s‐1. Under these conditions, there was no increase in cell number, and the cultures turned red. Relative amounts of enzymes and thylakoid polypeptides in red and green cells were ascertained by immunoprobing with standardization on a chlorophyll (Chl) basis. In red cultures, the level of cytochromefwas greatly decreased (<1% of green cell level), which is expected to greatly impair the linear electron flow from photosystem (PS) II to PS I. Also, the levels of apoproteins in red cells, namely, of CPI, D2, CP47, LHC I, and ribulose‐1, 5‐bisphosphate carboxylase were reduced to 15, 18, 29, 48, and 80%, respectively, of those in green cells. Only adenosine triphosphate syn‐thase exhibited no significant change in the two types of cultures. The respiration rate of red cultures was much higher (100 μmoles O2. mg Chl‐1.h‐1) than that of green cells (16 μmoles O2. mg Chl‐1.h‐1). Conversely, net O2evolution (at Pmaxin green cultures was 80 μmoles O2. mg Chl‐1.h‐1but was —40 μmoles O2. mg Chl‐1.h‐1in red cultures. PS II activity was demonstrated in broken cells of both green and red cultures, showing activity of 40 and 15 μmoles DCPIP‐mg Chl‐1.h‐1(with DPC as electron donor), respectively. In contrast, PS I activity measured by the Mehler reaction showed that red rather than green cells had a greater activity (64 vs. 46 μmoles O2. mg Chl‐1.h‐1, respectively). Thus, in spite of the decline of O2evolution in red cells, the photosystems were still functional. We postulate that the decline of O2, evolution in red cells is largely attributable to an increase in the respiration rate and the impairment of linear electron flow from PS II to PS I and, to s

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1995.00897.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTThe response of carbonic anhydrase (CA) activity inPeridinium gatunenseNygaard, the natural bloom‐forming dinoflagellate in Lake Kinneret, to diel and seasonal variations in environmental conditions was characterized under controlled laboratory experiments. Simulated diel cycles demonstrated large changes in the ambient concentration of dissolved CO2and parallel changes in CA activity. The CA activity depended on the total concentrations of inorganic carbon (C1) and in particular on the dissolved CO2. Lowering theC1concentrations resulted in a large increase in CA activity within several hours. Light and photosynthesis were both required for the induction of CA activity. Under CO2‐limited conditions, the dependence of the photosynthetic rate on CA (estimated from the ratio of photosynthetic rates in the presence or absence of CA inhibitors) was greater inP. gatunensethan in other eukaryotic microalgae. This points to the ecological significance of CA in photosynthetic carbon uptake mechanisms of a large, dominant alga in a natural ecosys

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1995.00906.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTSeventeen clones of the toxic, epiphytic‐benthic dinoflagellateProrocentrum lima (Ehrenberg) Dodge isolated from three separate sites on the reef flats of Heron Island, Australia, were acclimated under the same set of environmental conditions. Morphological features examined for each clone included cell surface configuration, size, and dry weight. Physiological and biochemical features determined for each clone included reproduction rates, pigments (chlorophylla,chlorophyll c2, peridinin, and other xanthophylls), toxins (okadaic acid and methyl‐okadaic acid), and macromolecular compounds (total protein, lipid, and carbohydrate). Variation in morphological features and reproduction rates of clones within and between sites was minimal and not significant. Also, variation in biochemical features within an individual site was low, but pronounced differences existed among sites, the most notable of which was toxin content (okadaic acid and methyl‐okadaic acid). The greatest difference in biochemical features was between clones isolated from the southern site and clones isolated from the northern and southeastern sites. Results of a cluster analysis of clonal characters support the view that these two groups represent distinct genotypes. We suggest that these groups originated from separate seed sources and that the genetic integrity of each is maintained through asexual reprodu

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1995.00914.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

ABSTRACTThe effect of dissolved oxygen partial pressure on the accumulation of astaxanthin in the green algaHaematococcus lacustris (Gir.) Rostaf (UTEX16) was studied in N‐limited continuous chemostat cultures. The steady‐state astaxanthin content measured against culture volume, cell number, and biomass dry weigh ofHaematococcus cultureswas proportional to the dissolved O2partial pressure in the culture medium, over the range of 0–50% O2The steady‐state biomass dry weight concentrations remained at between 0.52 and 0.57 g. L‐1over the range of dissolved O2partial pressure studied. Steady‐state cell densities at dissolved O2partial pressures above the air saturation level (1.13–1.58 × 105cells.mL‐1) were about half of that measured at lower dissolved O2partial pressures (2.42–2.63 × 105cells.mL‐1). Both biflagellated zoospores and nonmotile aplanospores were found at steady state. The fraction of nonmotile cells was higher at dissolved O2partial pressures above the air saturation level (94.44–98.01%) than at dissolved O2partial pressure below the air level (

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1995.00922.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY