Chemical composition studies on some aquatic macrophytes in three Scottish lochs. I. Chlorophyll,ash, carbon,nitrogen and phosphorus.

The chlorophyll, ash, carbon, nitrogen and phosphorus levels in seven species of freshwater macrophytes (Juncus effusus L., Iris pseudacorus L., Carex rostrata Stokes, Glyceria maxima (Hartm.) Holmberg, Nuphar lutea (L) Sm., Polygonum amphibium L. and Schoenoplectus lacustris (L) Pallas) in three Scottish lochs of different trophic levels were studied during 1975. Mean chlorophyll levels varied from a minimum of 1.73 mg g^–1 dry weight in Balgavies Loch Juncus to 10.22 mg g^–1 dry weight for Forfar Loch Iris. Carbon contents ranged from 450 to 520 mg g^–1 ash-free dry weight. For ash, nitrogen and phosphorus, significant differences in mean concentrations were detected among plant species as well as within one plant species growing in different lochs. Positive correlations were apparent between the degree of eutrophication in the study areas and the amount of ash, phosphorus and nitrogen present in the plants growing in them.     

Chlorophyll and Primary Productivity of Some Green,Freshwater Sponges

Relationships between ash-free dry weight, viable chlorophyll a and pheopigments a were examined by linear regression analysis for non-gemmulating and gemmulated Spongilla lacustris and for an unidentified, non-gemmulating species. The primary productivity of S. lacustris was determined by both oxygen and ¹⁴C techniques and expressed on a biomass, chlorophyll a, and area basis, and the photosynthetic efficiency was calculated. The proportion of algal photosynthate excreted by the sponge was investigated, and the transfer of algal photosynthate to the sponge was examined by autoradiography.     

Epilithic biomass in an outflow stream at Potter Peninsula, King George Island, Antarctica

The epilithic biomass of an outflow stream at Potter Peninsula (King George Island, Antarctica) was studied from November 1996 to February 1997 by means of chlorophyll a concentration, dry weight and ash-free dry weight. The Autotrophic Index and the Lakatos classification were also used in order to characterize the epilithic community. Several physical and chemical parameters were analyzed. Snow and ice melt greatly increased water flow through Tres Hermanos Lake and in the stream. Chlorophyll a concentrations fluctuated between undetectable and 3.5 μg cm⁻² with a marked increase, which averaged 3 orders of magnitude, towards the end of the study period. Dry weight ranged between 299.9 and 13,118.7 μg cm⁻² and ash-free dry weight between 70.8 and 996.9 μg cm⁻². According to the Autotrophic Index and the Lakatos classification, the epilithon of the stream had a low mass with low organic component and large amount of inorganic sediment. The organic matter comprised a low proportion of chlorophyll a and a major proportion of probably detritus or bacteria, rather than fauna. Accepted: 3 June 2000     

Periphyton biomass dynamics in gravel bed rivers: the relative effects of flows and nutrients

SUMMARY. 1. Periphyton chlorophyll a and ash free dry weight (AFDW) were monitored in nine rivers to examine the relative importance of flows and nutrients for regulating periphyton biomass in gravel bed rivers. 2. Mean annual flows in the rivers ranged from 0.94 to 169 m³ s^?1, mean dissolved reactive phophorus (DRP) from 1.3 to 68 μ g 1^?1, periphytic chlorophyll a from 4.6 to 73 mg m ^?2. and AFDW from 2.8 to 16 g m^?2. 3. For eight of the nine rivers NH₄-N. DRP, total Kjeldahl nitrogen, total phosphorus and total suspended solids were correlated (P<0.01) with flow, and for seven rivers conductivity was inversely correlated (P<0.05) with flow. 4. There was a hyperbolic relationship between flows and biomass, with chlorophyll a >100 mg m ^?2 and AFDW >20 g m^?2 occurring most frequently in flows of <20 m³ s^?1. 5. Floods prevented the development of medium term (i.e. up to 2 months) maxima in biomass in five of the rivers, but maxima occurred over summer-autumn and winter-spring in the three rivers where floods were absent. 6. Chlorophyll a biomass was more resistant to flooding than AFDW. Only 5993 of the forty-six recorded floods caused chlorophyll a scouring, whereas 74% of the floods caused AFDW scouring. The efficiency of scour was more influenced by the pre-flood biomass than the magnitude of the event. 7. Biomass maxima were significantly correlated (P<0.01) with mean DRP concentration during the accrual period. Overall, up to 53% of the mean annual biomass difference between rivers was explained by the mean annual DRP concentrations. However, the high correlations between nutrient concentrations and flow indicated that the nutrient data were also carrying hydrological information and that simple causal relationships between nutrients and biomass are difficult to establish in rivers. 8. It is concluded that hydrological factors contribute at least equally with nutrients to the differences in periphyton biomass between the gravel-bed study rivers. They combined to explain up to 63.3% of the variance in biomass, compared with 57.6% for nutrients. It is recommended that periphyton data from gravel-bed rivers should always be viewed within the context of the flow history of the site, and not just as a function of nutrient concentrations.     

Herbivory,current velocity and algal regrowth: how does periphyton grow when the grazers have gone?

1. An experiment conducted in streamside channels was used to document the regrowth of grazed periphyton. Our objective was to determine the relative importance of current velocity, grazing duration, and grazer type in shaping the trajectory of algal and periphytic regrowth. 2. The grazing mayflies Baetis bicaudatus and Epeorus longimanus were used alone and in combination to create three grazing treatments at slow, medium and fast current (2–5, 15–20 and 30–40 cm s^?1, respectively). Duration treatments consisted of 2, 4, 6, 8, 10 days of grazing. Chlorophyll a and ash‐free dry mass (AFDM) accumulation on grazed tiles was measured (as periphytic AFDM and chlorophyll a, respectively) at 2, 4, 6, 8 and 10 days following the removal of grazers. 3. Chlorophyll a and AFDM was best predicted by interactions between current velocity, grazing duration and regrowth time. 4. The two grazer species did not differ in their effect on Chlorophyll a and AFDM during the period of periphytic regrowth that followed grazing. 5. Longer grazing duration reduced periphytic biomass, but also accelerated algal regrowth, and this growth enhancement was more pronounced at slower current velocities. 6. Data from this study suggest that herbivory can have important historical effects on periphytic accrual.     

Effects of grazing on the quantity and quality of freshwater Aufwuchs

Qualitative and quantitative measures of the Aufwuchs (scum flora) on artificial substrates in situ were used to evaluate the effects of grazing by freshwater pulmonate snails in a shallow pond in southeastern Michigan. Grazer densities of 216 snails/m² marked reduced standing crop so that after 45 days grazed substrata had 6.46 mg dry weight, 604 µg C and 4.18 µg chlorophyll a as compared to controls with 30.62 mg dry weight, 3699 µg C and 6.29 µg chlorophyll a, all on a per dm² basis.Grazing did not change carbon per mg dry matter but caused significant increases in both µg chlorophyll a (control, 0.206; and grazed, 0.649 µg chlorophyll a/mg dry weight, P < 0.01) and nitrogen (control, 8.3; and grazed, 24.2 µg N/mg dry weight, P < 0.001) after 45 days. Both abundance and diversity of the attached community was reduced by grazing from 24 taxa and 80,889 individuals/cm² on control to 8 taxa and 501 individuals/cm² on grazed substrates. Mean productivity of the Aufwuchs was significantly (P < 0.001) reduced by grazing from 76.3 µg C/(dm²·day) on control to 17.7 µg C/(dm²·day) on grazed substrata.Snails were very efficient at clearing smooth surfaces of living cells, detritus, and particulate inorganic matter. There was little evidence of selectivity except for an apparent inability to remove some of the smallest cells (e.g. Cocconeis sp.) probably for mechanical reasons.     

Biometrical relationships, energy content and biochemical composition of Neomysis mercedis from Lake Washington

Morphometric relationships, caloric content and biochemical composition of Neomysis mercedis were determined for freshly caught mysids. Strong positive correlations between telson length, carapace length, dry weight, energy content and total length are described by the equations: Ln (Dry weight) = –5.02 + 2.57^* Ln (Total Length), Telson Length = 0.13^* Total Length, and Energy (Calories) = –37.13 + 4.85^* Mean Total Length. Energy (4.92 cal mg^–1 AFDFW), ash (8.61% dry weight) and total Kjeldahl nitrogen (10.6% dry weight) content are comparable to values reported for other species. A comparison of the length-weight relationship for N. mercedis with similar equations published previously for other mysid species indicated that the predicted mean dry weight at any particular length varied among species.     

Effect of l-arginine,casein hydrolysate,banana powder and sucrose on growth and solasodine production in shoot cultures of Solanum laciniatum

The addition of l-arginine, casein hydrolysate, banana powder and the reduction of the concentration of sucrose in the media could increase the solasodine content in the shoot cultures of Solanum laciniatum. No linear correlations between growth index, chlorophyll content and solasodine content were observed, however a positive linear correlation between solasodine productivity and chlorophyll content occurred in these shoot cultures.Abbreviations Ch chlorophyll content - DW dry weight - fl flask - FW fresh weight - GI growth index - LOD limit of detection - LOQ limit of quantitation - SDc solasodine content - SDp solasodine productivity - w week     

Comparative photosynthetic studies of Ecklonia cava (Laminariales,Phaeophyta) bladelets with and without zoosporangial sori

Photosynthetic rates were compared between Ecklonia cava bladelets with and without zoosporangial sori sampled from the subtidal zone (about 5 m deep) in Nabeta Bay, Shimoda, Japan. Photosynthetic rates of bladelets were lower in the sorus portion than in the non-sorus portion on the basis of area, dry weight and chlorophyll a. Respiration rates were higher in the sorus portion than in the non-sorus portion on the basis of area and chlorophyll a, whereas they were almost the same on a dry weight basis. The differences were mainly due to a large difference in dry weight per unit bladelet area between the sorus and the non-sorus portion. Light compensation points were higher in the sorus portion than in the non-sorus portion.     

Covariance Analysis of Chlorophyll Distribution in the Sundays River Estuary,Eastern Cape

Summary

An analysis of covariance performed on chlorophyll a distribution data from the Sundays River estuary identified five persistent water masses with significantly different chlorophyll a contents. These corresponded to different hydrodynamic regions within the estuary. The relationship between salinity and chlorophyll a was used to identify a transition zone between the low-salinity upper estuary and the brackish riverine inflow. Chlorophyll a concentrations ranged from <6 μg 1^?1 near the mouth to >100 μg 1^?1 in the middle and upper reaches. High variance of chlorophyll a data in this region was the result of temporal chlorophyll a fluctuations in two time scales. The first related to the daily ebb/tide and the second to the lunar spring/neap tidal cycle. Unlike its importance in larger and deeper estuaries, light played only a minor role in the horizontal distribution of chlorophyll a. The presence of a chlorophyll a maximum in the turbid low salinity region is explained in terms of the relatively constant photic depth/mixed depth ratio along the estuary and the high residence time of water in this region.     

Culture of the marine phytoplankter,Dunaliella tertiolecta,with light-dark cycles

Summary Dunaliella tertiolecta was grown in continuous culture, maintained by a single daily dilution to a constant cell concentration, with photoperiods of duration 3 to 18 hours. Illumination was provided with filtered tungsten light having a maximum intensity at 580–590 m. Average intensity at the culture surface was maintained at 0.05 cal/cm²xmin. Temperature was regulated at 20° C. Daily cell production and the fraction of cells dividing daily are reported for each of the photoperiods. Cyclic diurnal variations were noted in cell pigment content, cell volume and photosynthetic rate. Corresponding variations in cell carbon/chlorophyll a ratios were small and may be unimportant for the estimation of biomass from chlorophyll a in field work. An equation for calculating daily growth rate in continuous light, from light absorption by cell chlorophyll a, derived previously, was modified to include the influence of providing light in discrete photoperiods.Supported by U. S. Atomic Energy Commission, Contract AT(11-1)-34 Project 108.     

Pheopigment dynamics,zooplankton grazing rates and the autumnal ammonium peak in a Mediterranean lagoon

The dilution technique was used to estimate chlorophyll and pheopigment, net and gross production as well as zooplankton grazing over a 12-month period in a coastal lagoon in Southern France. Chlorophyll a (Cha) based gross growth rates of phytoplankton ranged from undetectable in February to 2.6 day⁻¹ in June, corresponding to 3.8 divisions per day. Cha-based grazing rates ranged from undetectable in February to 1.1 d⁻¹ in June. The seasonal growth pattern of picoplankton was similar to that of the whole community, with a peak in July, corresponding to four divisions per day. Grazing processes represented from 20 to 150% of the phytoplankton daily growth, and the grazing pressure was stronger on small phytoplankton cells than on larger cells. Gross growth rates of phytoplankton were related to zooplankton grazing rates, and both were related to water temperature. Mesozooplankton which escaped sampling or oysters had to be also invoked as additional sinks for the primary production. In the fall, pheopigment concentrations greater than chlorophyll concentrations coincided with high ammonium levels in the water column. Pheopigment a production rates were highly correlated to chlorophyll -based microzooplankton grazing rates. The pheopigment a to chlorophyll a ratio was correlated with ammonium concentrations and could be used an index of the balance between ammonium supply (degradation) and demand (uptake by phytoplankton). In addition, pheopigment degradation rates in absence of grazing could be related to irradiance, indicating photo-degradation of these compounds.     

Zooplankton species diversity in Lake St. Clair,Ontario, Canada

Zooplankton species diversity and selected chemical parameters were investigated at three stations in Lake St. Clair, Ontario, Canada, from 15 June–26 August, 1971. Primary productivity and zooplankton species diversity were greatest at stations 1 and 2 which were enriched by the Thames River drainage. No significant correlation between total zooplankton diversity and chlorophyll a was found, however, within the Cladocera and Copepoda, positive correlations with chlorophyll a, reactive silicate and nitrate were shown at stations 2 and 3. Rotifer species diversity showed negative correlation with chlorophyll a, nitrate and reactive silicate.     

Algal biomass dynamics during colonization of artificial islands: experimental results and a model

Algal biomass during colonization of polyurethane foam islands (5.1 cm × 7.6 cm × 7.6 cm) was approximated by measuring chlorophyll a levels on islands after exposure periods of 1, 2, 3, 4, and 6 weeks at six locations in a small lake in central Tennessee, USA. Chlorophyll, ash-free dry weight, and concurrent environmental data were collected for two colonization periods: one in late winter and spring (Set 1), a second in summer (Set 2).During Set 1 algal biomass levels, as indicated by chlorophyll a, showed a sharp rise initially, but Set 2 islands exhibited a lag period of 7 to 12 days before a rapid increase in algal biomass was noted. Equilibrium chlorophyll a values were similar for both sets. High levels of phaeopigments were found at Stations 2, 3, and 4 during Set 2 resulting in large corrections in chlorophyll a readings. Ash-free dry weight values increased steadily through each colonization period.A model of biomass accumulation during colonization was constructed postulating three major processes — photosynthesis, respiration, and passive accumulation — which were modulated by three environmental factors — light, temperature, and plankton chlorophyll a levels. For simulations parameter values were taken from the literature where possible. Additional parameter values were set and literature values adjusted when the model was tuned to Set 2 data. A simulation with the tuned model using Set 1 environmental input resulted in a good prediction of equilibrium values, but a misinterpretation of initial values. The discrepancy between model predictions and data was alleviated when the passive accumulation rate was increased demonstrating the dependence of biomass values early in colonization on passive accumulation from the plankton.     

Relations between Photosynthetic Pigment Accumulation and Microsporogenesis in Secale, Triticale, and Secalotriticum

The accumulation of photosynthetic pigments in underflag and flag leaves as well as the process of microsporogenesis in lines of tetraploid Secale, hexaploid Triticale, and hexaploid Secalotriticum were studied. Significant positive correlations were found between the amounts of chlorophyll a (Chl a), carotenoids (Car), Chl a/b ratio, and the normal proceeding of meiosis. High probability of paternal type of inheritance of specifities of meiosis of pollen mother cells and variation in photosynthetic pigments during plant transition from the stalk-shooting to heading stage were demonstrated.     

Epiphytes from a deep-water characean meadow in an oligotrophic New Zealand lake: species composition,biomass and photosynthesis

1. The epiphytic flora of a characean meadow in Lake Coleridge, a deep, oligotrophic lake on the South Island of New Zealand, was dominated by diatoms, particularly Eunotia pectinalis and Achnanthes minutissima. The meadows occupied a depth range from 5 to 30 m. Adnate taxa predominated at all depths below 5 m, while increased taxonomic diversity at 5 m resulted from an increased abundance of erect taxa, including chlorophytes and stalked diatoms. 2. Seasonal changes in epiphyte biomass were followed using artificial substrata and by estimating epiphyte chlorophyll a concentration on host plants. The latter required development of a novel technique utilizing the consistent relationship between fucoxanthin and chlorophyll a concentrations in the epiphyton. Epiphyte chlorophyll a on host plants varied with depth and host species between 0.1 and 0.3 mg g^–1 dry weight. Maximum epiphyte biomass was at 10–15 m depth. At depths of 15 m and less, epiphyte chlorophyll a reached a maximum of ≈ 200–300 mg m^–2 in mid-summer, while at greater depths maximum biomass was less and coincided with a period of clear water in spring. 3. Photosynthetic carbon fixation was estimated from photosynthesis–radiation curves and estimates of radiation flux at sampling depths. At depths greater than 10 m, variability of the vertical extinction coefficient of lake water rather than seasonal fluctuations in incident radiation were responsible for determining the temporal pattern of production. Chlorophyll a-specific photosynthesis was estimated to peak in summer at 5 m (8 mg mg^–1 day^–1), and in spring at all other depths. 4. Annual epiphyte production was estimated as 27 g C m^–2 year^–1 at 5 m depth, falling to 15 g C m^–2 year^–1 at 15 m and 1 g C m^–2 year^–1 at 30 m. Areal biomass changes tended to be temporally but not quantitatively coupled to estimated in situ photosynthesis, and we hypothesize that epiphyte biomass may have been controlled by grazing gastropod snails.     

Metabolic responses of Lemna minor to lead ions I. Growth, chlorophyll level and activity of fermentative enzymes

Duckweed Lemna minor L. was grown on Wang culture medium supplemented with lead ions for 24 hours. Metal was tested at 1.5, 3 and 6 mg·dm⁻³ concentrations. The growth of Lemna minor was inhibited by lead ions, but the dry to fresh weight ratio increased as the concentration of Pb²⁺ in the medium increased. With increased concentrations of Pb ions, the contents of chlorophyll a and chlorophyll b in roots and fronds were correspondingly lower in comparision with the control. The effect of lead upon activities of some glycolitic and fermentative enzymes in roots of duckweed was examined. The activity of pyruvate kinase decreased with increasing lead concentrations, but cytosolic malate dehydrogenase behaved in an opposite manner. The lowest concentration of Pb stimulated alcohol dehydrogenase; phosphoenolopyruvate carboxylase activity was maintained at relatively constant values at all tested lead concentrations.     

Algal pigment diversity in coastal sediments from Kerguelen (sub-Antarctic Islands) reflecting local dominance of green algae,euglenoids and diatoms

Summary High Performance Liquid Chromatography analysis of algal pigments from inter- and subtidal (deep and shallow) sediments from the Kerguelen Islands showed clear differences in the pigment composition at the different stations. High concentrations of chlorophyll c and fucoxanthin were present at all locations, indicating significant diatom densities, chlorophyll b was detected at all sites. At one station the other green algal pigments were also present; here green algae contributed more to chlorophyll a concentrations than diatoms, as estimated by using pigment ratios and microscopic observations. At another location chlorophyll b was associated with a high concentration of diadinoxanthin, indicating an abundance of euglenoids. This indicates that chemotaxonomy can be powerful tool in microphytobenthos studies since enumeration of living cells are difficult as many algae are attached to sediment particles (epipsammic algae). Ways of diagenesis, carotenoid degradation and the role of grazing are briefly mentioned. Phaeophorbide a-like pigments were the most significant chlorophyll a degradation products, with concentrations up to 110 g · g^–1 dry weight sediment, i.e. 10 times the chlorophyll a concentration. Some taxonomic estimations, based on pigments ratios, and their limits, are discussed.     

The occurrence of haemoglobin and hydrogenase in nodules of twelve Casuarina-Frankia symbiotic associations

Seedlings of Casuarina cunninghamiana Miq., C. equisetifolia L. and C. glauca Sieber growing in N-deficient potting mix were inoculated with Frankia sp. from each of 4 different sources. After ca 4 months, plants were harvested and nodules from the 12 Casuarina-Frankia combinations evaluated for (1) concentrations of haemoglobin (measured as CO-reactive haem) and (2) occurrence of hydrogenase. The aim was to determine if these factors were related to nitrogen accumulation and biomass production. There were marked host-Frankia source interactions with up to 10-fold differences in plant dry weight and 50-fold differences in the efficiency of nitrogen fixation (as estimated by N₂ accumulated mg^?1 nodule dry weight). Differences in plant growth and nitrogen accumulation were apparently related to nodule specific activity, because the 12 associations had similar nodulation characteristics, e.g. time for nodulation to occur. The concentration of haemoglobin in Casuarina nodules ranged from 0 to 27 nmol haem (g FW)^?1. There was a strong linear correlation between concentrations of haemoglobin and dry weights of the whole plants (r=0.77, 0.92 and 0.97, P≤0.05) for C. cunninghamiana, C. equisetifolia and C. glauca symbiotic associations, respectively. However, the linear correlation between concentration of haemoglobin and nitrogen content of whole plant was lower (r=0.60, 0.64 and 0.71, P≤0.05) for the three Casuarina symbioses, respectively, and there was only a poor correlation between haemoglobin concentration in nodules and the rate of nitrogen accumulation on nodule weight basis. This indicates that haemoglobin concentration is not the sole physiological determinant of nitrogen fixation in Casuarina. All the Casuarina-Frankia symbiotic associations studied also showed the presence of a hydrogen uptake enzyme. The activity of the enzyme ranged from 5.1 to 34.1 μmol H₂ (g FW)^?1 h^?1, and hydrogen uptake was not correlated with plant dry weight, nitrogen content or the rate of nitrogen fixation. Hydrogen evolution could not be detected in any of the associations.