Genetic structure of asexually reproducing Enteromorpha linza (Ulvales: Chlorophyta) in Long Island Sound

Heterotrophic bacterial uptake and turnover of glycolate were measured in the water column of the New York Bight apex during four seasonal cruises over almost a one-year period between May 1977 and March 1978. Glycolate turnover was most rapid in May and July, when primary productivity and estuarine runoff were high. Extremely rapid glycolate turnover times (<1 h) were detected at some stations during these months. Increased bacterial glycolate tunover did not accompany increased primary productivity in March, when water temperatures were lowest. Glycolate flux calculations indicate that the measured rates of glycolate consumption by bacteria always exceeded estimated glycolate production by phytoplankton, except in March. This excess may reflect an underestimation of phytoplankton production or the input of glycolate from other sources, such as estuarine runoff. Glycolate utilization appears to be seasonally important to bacteria in the New York Bight apex, coinciding with fluctuations in phytoplankton primary productivity.     

Phytoplankton exudate release as an energy source for the growth of pelagic bacteria

The release of dissolved organic carbon (DOC) from phytolankton during photosynthesis, and the utilization of this carbon by planktonic bacteria, was studied using ¹⁴CO₂ and selective filtration. Natural sea water samples from a coastal area of the Northern Baltic Sea were incubated in the laboratory for detailed studies, and in situ for estimation of annual dynamics. In a laboratory incubation (at +1°C) the concentration of ¹⁴C-labelled dissolved organic carbon increased for about 2 h and then reached a steady state, representing about 0. 1% of the total DOC. Labelled organic carbon in the phytoplankton and bacterial fractions continued to increase almost linearly. The continuous increase in the bacterial fraction is thought to represent almost instantaneous utilization of the DOC released from the phytoplankton during photosynthesis. As an annual average, in 4 h in situ incubations, about 65% of the labelled organic carbon was found in the phytoplankton fraction (>3 m), about 27% in the bacterial fraction (0.2 to 3 m) and the remaining 8% as DOC (<0.2 m). Large variations in these percentages were recorded. The measured annual primary production was 93 g C m^-2 (March to December), and the estimated bacterial production due to phytoplankton exudates 29 g C m^-2. This represents a release of DOC of about 45% of the corrected annual primary production of 110 g C m^-2 (assuming a bacterial growth efficiency of 0.6).     

Relationships between nucleic acid concentrations and primary production in the Catalan Sea (Northwestern Mediterranean)

We explored the relationships between classical estimators of autotrophic biomass and primary production, such as chlorophyll a concentration and ¹⁴C-fixation rates, and biochemical indices based on DNA and RNA determinations, which have been proposed as indicators of physiological state in natural plankton populations. The measurements were made during two cruises across the Catalan Front, carried out in May 1989 and February 1990, corresponding respectively, to periods of stratification and moderate mixing. DNA and RNA concentrations (measured by a double-staining fluorimetric technique) were significantly correlated with chlorophyll a in February 1990, but not in May 1989, when a marked deep chlorophyll maximum was present. Significant positive correlations between RNA concentration and primary production and between RNA: DNA and primary production were found during both surveys, probably reflecting both higher RNA concentrations per cell and enhanced bacterial and microheterotrophic growth in high primary production situations. The results support the potential usefulness, in biological oceanography, of biochemical indicators based on DNA and RNA concentrations.     

Diel variation of bacterial productivity in seagrass (Zostera capricorni) beds measured by rate of thymidine incorporation into DNA

Diurnal variations occurred in bacterial growth rates in the sediment and water column associated with seagrass (mainly Zostera capricorni Aschers) beds in Moreton Bay, Queensland, Australia. Studies were carried out in March and June 1981. Cell production rates increased by 5- to 10-fold during the morning and decreased during the afternoon. No nocturnal variation was observed. Daily bacterial cell production rate in the aerobic zones of the seagrass bed was estimated to be 43 mg C m^-2. A minimum of 100 mg C m^-2 d^-1 would be required to support the bacterial production. This represents about 10% of net primary production. The incorporation of tritiated thymidine into DNA was used to measure bacterial growth. The validity of the method is discussed.     

Primary production studies during a Gyrodinium cf. aureolum (Dinophyceae) bloom in the western English Channel

Water column production measurements were made during a bloom of the marine dinoflagellate Gyrodinium cf. aureolum in the Western English Channel in July 1987. The bloom was sampled over a period of 5 d, and primary production was measured using the oxygen light and dark bottle method and the ¹⁴C technique. The photosynthetic quotient (PQ) varied between 1.2 and 3.7. During the period sampled, the proportion of phaeopigments significantly increased (from <5 to >50%) and mixed layer dissolved oxygen saturation decreased from 133 to 114%. A model was used to determine gross water column productivity in the surface mixed layer on two days, and net production values were shown to be close to zero or slightly negative. Comparisons of production values are made with other published G. cf. aureolum bloom data.     

Productivity of bacteria and microalgae and the effect of grazing by holothurians in sediments on a coral reef flat

Bacterial productivity in sandy sediments on reef flats at Lizard Island, Great Barrier Reef was determined from the rate of incorporation of tritiated thymidine into DNA. The study was conducted during January 1982 and July 1983. A small diurnal increase occurred in sediments having a dense population of microalgae. Bacterial production was 120 to 370 mg C m^-2 d^-1 in summer on reef flats, which was equivalent to 30–40% of primary production by benthic microalgae. In winter, rates of primary production by benthic microalgae and secondary production by bacteria were about one-half to one-fifth of those in summer. There was much variation in production, due to patchiness in the distribution of benthic microbes, especially microalgae. Doubling times for the bacteria in surface sediment were 1 to 2 d in summer and 4 to 16 d in winter on the reef flats. These high productivity values for bacteria indicated that a net input of organic matter to the sediment was needed to support the growth of bacteria. Sediment bacteria thus have a very important role in transforming organic matter on the reef flats. Grazing by Holothuria atra depressed both primary production and bacterial production. It was estimated that these holothurians ate about 10 to 40% of bacterial carbon produced each day in summer, and thus have an important role in the carbon cycle. Harpacticoid copepods were numerically important components of the benthic meiofaunal community and probably had a significant impact on bacterial density as grazers.     

Fractionated phytoplankton primary production,exudate release and bacterial production in a Baltic eutrophication gradient

The distribution of phytoplankton primary production into four size fractions (>10 m, 10-3 m, 3-0.2 m and <0.2 m), the utilization of algal exudates by bacteria and the bacterial production were studied in a eutrophication gradient in the northern Baltic proper. The polluted area exhibits substantially increased nutrient, especially nitrogen, levels while only minor differences occur in salinity and temperature regimes. Total primary production was 160 g C · m^-2 · yr^-1 at the control station and about 275 g C · m^-2 · yr^-1 at the eutrophicated stations. The estimated total exudate release was 16% of the totally fixed ¹⁴CO₂ in the control area and 12% in the eutrophicated area (including the estimated bacterial uptake of exudates). The difference in¹⁴CO₂ uptake rates between incubation of previously filtered water (<3, <2, <1 m) and unfiltered water was used to estimate bacterial uptake of phytoplankton exudates which were found to contribute about half of the estimated bacterial carbon requirement in both areas. Bacterial production was estimated by the frequency of dividing cells (FDC) method as being 38 g C · m^-2 · yr^-1 at the control station and 50 g C · m^-2 · yr^-1 at the eutrophicated stations. To estimate the mean in situ bacterial cell volume a correlation between FDC and cell volume was used. The increased annual primary production in the eutrophicated area was due mainly to higher production during spring and autumn, largely by phytoplankton cells (mainly diatoms) retained by a 10 m filter. Primary production duringsummer was similarin the two areas, as was the distribution on different size fractions. This could possibly explain the similar bacterial production in the trophic layers at all stations since the bulk of bacterial production occurs during summer. It was demonstrated that selective filtration does not quantitatively separate photoautotrophs and bacteria. A substantial fraction of the primary production occurs in the size fraction <3 m. The primary production encountered in the 3-0.2 m fraction was due to abundant picoplankton (0.5 to 8 · 10⁷ ind · l^-1), easily passing a 3 m filter. The picoplankton was estimated to constitute up to 25% of the total phytoplankton biomass in the control area and up to 10% in the eutrophicated area.     

Biomass and production in polar planktonic and sea ice microbial communities: a comparative study

Algal and bacterial biomass and production were measured in the plankton, platelet ice and congelation ice communities at one station in McMurdo Sound, Antarctica during September and October 1986. Bacterial abundances and particulate organic carbon and nitrogen were 10 to 100 times greater in the plankton than in the sea ice, whereas the chlorophyll a concentrations in the plankton and sea ice microbial communities (SIMCO) were similar Rates of both light-limited and light-saturated photosynthesis and daily primary production were 2 to 6 times greater in the plankton than in the SIMCO. Bacterial growth rates ranges from 0.7 to 1.5 d^-1 in all three communities; however, because of the greater bacterial biomass in the plankton, bacterial production was 15 to 20 times higher there than in the SIMCO. These results suggest that during the early austral spring, planktonic production contributes significantly to total production in ice-covered environments.     

Bacterial production in North Sea sediments: clues to seasonal and spatial variations

Benthic bacterial production and biomass were measured at 16 stations in the North Sea covering a wide range of sediment types from the Southern Bight and the English coast to the Skagerrak. Stations were sampled in August 1991 and February 1992. The best predictor for summer/winter and spatial variations in benthic bacterial production in North Sea sediments was temperature. In winter the ranges in temperature were too small to account for the spatial variations in benthic bacterial production. The direct effect of temperature alone on bacterial production could not explain the variations. The apparent Q₁₀-values derived from the relations between bacterial growth and temperature exceeded the range in Q₁₀-values generally accepted for bacterial growth (between 2 and 3). Temperature was assumed to covary closely with substrate availability for bacteria. Due to its significant seasonality phytopigment content of the sediment (chlorophyll a and pheopigment) was found to be a better indicator of substrate availability than sediment organic matter, which did not demonstrate seasonality. Temperature and phytopigment accounted for up to 88% of the seasonal and spatial variations in bacterial production. The significant relations between bacterial production and biomass in summer coinciding with significant relations between bacterial biomass and phytopigments suggest that variations in phytopigments in the sediment may be indicators of the variability of labile components regulating bacterial production in sediments.     

滤速对慢滤池深度处理生活污水的影响

为进一步提高再生水水质,将慢滤池用于污水二级处理出水的进一步处理。选取浊度、COD、色度和细菌总数4个指标,利用实验室小试装置,研究了0.1、0.3、0.5m/h这3种滤速下慢滤池的性能。结果表明,滤速由0.1m/h升高至0.3m/h时,慢滤池出水水质略有下降。而滤速由0.3m/h升高至0.5m/h时,慢滤池出水水质下降显著。滤速小于等于0.3m/h时,慢滤出水浊度、COD、色度和细菌总数平均为0.4NTU、25.9mg/L、14.9°、5×10^3CFU/mL。慢滤对这4个指标的平均去除率分别为78.6%、36.0%、34.0%、62.3%。为获得优良的水质,建议慢滤池用于污水深度处理时,滤速宜小于0.3m/h。但实际工程中,用户对再生水水质要求不高时,则可适当增大慢滤池滤速。     

Net productivity of two cohorts of Chordaria flagelliformis (Phaeophyta) in Nova Scotia,Canada

Productivities of two cohorts of Chordaria flagelliformis (O. F. Müll.) C. Ag. were estimated from measured changes in biomass and survivorship over time. Maximum productivity during the summer growing season was 2.6 g C m^-2 d^-1. Although this figure is relatively high, the short growing season results in an annual production of only 89 g C m^-2. The significance of primary production by C. flagelliformis lies in its seasonal timing. During the summer growth period, 50% of production was recycled directly by detrital material. During the same time period, productivity and biomass losses of other seaweeds are at their lowest.     

Seasonal variability of intertidal bacterial metabolism and growth efficiency in an exposed sandy beach during low tide

Benthic gross primary production (GPP) and community respiration (BCR) were regularly measured on sandy beach sediment during low tide in a megatidal ecosystem. These measurements were assessed during 2 years in situ within a benthic chamber simultaneously with bacterial production (BP). Results suggested that community respiration in Wimereux sandy beach sediments was probably dominated by bacterial respiration and that the estimated benthic bacterial growth efficiency (BGE) was highly variable. Although temperature significantly controlled both BP and BCR during low tide at the annual scale, the temperature effect on BGE was not significant. The instability and sediment erosion caused by the wave action and the tidal cycle were thus thought to influence the BGE. Since the sampling site is regularly affected by Phaeocystis foam deposit (enhancing the BCR and decreasing the BGE), and since GPP rates were highly variable and supported by high assimilation numbers (i.e., >1 mgC mgChla ⁻¹ h⁻¹), phytoplankton organic matter deposit following the immersion of the study site was thought to explain the BGE variability.     

Phytoplankton carbon dynamics during a winter-spring diatom bloom in an enclosed marine ecosystem: primary production,biomass and loss rates

Phytoplankton production, standing crop, and loss processes (respiration, sedimentation, grazing by zooplankton, and excretion) were measured on a daily basis during the growth, dormancy and decline of a winter-spring diatom bloom in a large-scale (13 m³) marine mesocosm in 1987. Carbonspecific rates of production and biomass change were highly correlated whereas production and loss rates were unrelated over the experimental period when the significant changes in algal biomass characteristic of phytoplankton blooms were occurring. The observed decline in diatom growth rates was caused by nutrient limitation. Daily phytoplankton production rates calculated from the phytoplankton continuity equation were in excellent agreement with rates independently determined using standard ¹⁴C techniques. A carbon budget for the winter bloom indicated that 82.4% of the net daytime primary production was accounted for by measured loss processes, 1.3% was present as standing crop at the end of the experiment, and 16.3% was unexplained. Losses via sedimentation (44.8%) and nighttime phytoplankton respiration (24.1%) predominated, while losses due to zooplankton grazing (10.7%) and nighttime phytoplankton excretion (2.8%) were of lesser importance. A model simulating daily phytoplankton biomass was developed to demonstrate the relative importance of the individual loss processes.     

Development of symbiotic bacterial bioluminescence in a nearshore cephalopod,Euprymna scolopes

The small neritic cephalopod Euprymna scolopes possesses a large glandular light organ that contains the symbiotic luminous bacterium Vibrio fischeri. Adult and immature E. scolopes were caught in the evening with dip nets in shallow water along the shore of Kanohe Bay, Oahu, Hawaii, during late February 1984. The initiation of the symbiosis was investigated by rearing the cephalopods either in seawater taken from aquaria containing adult E. scolopes or in seawater with reduced bacterial concentrations due to filtration or due to absence of adults. Light production was measured during early development. Bioluminescence was not detected in E. scolopes immediately after hatching. Most individulas of E. scolopes that hatched into seawater containing, or previously exposed to, adults produced light within 24 h. Individuals that hatched into filtered seawater did not produce light. The data suggest that each generation aquires an infection from free-living bacteria rather than from the egg, and that light production is dependent on the nutritional state of the host. Access to an initial inoculum of free-living, luminous bacteria seems to be critical for establishing a successful symbiosis.     

Early onset of vegetation growth vs. rapid green-up: impacts on juvenile mountain ungulates

Seasonal patterns of climate and vegetation growth are expected to be altered by global warming. In alpine environments, the reproduction of birds and mammals is tightly linked to seasonality; therefore such alterations may have strong repercussions on recruitment. We used the normalized difference vegetation index (NDVI), a satellite-based measurement that correlates strongly with aboveground net primary productivity, to explore how annual variations in the timing of vegetation onset and in the rate of change in primary production during green-up affected juvenile growth and survival of bighorn sheep (Ovis canadensis), Alpine ibex (Capra ibex), and mountain goats (Oreamnos americanus) in four different populations in two continents. We indexed timing of onset of vegetation growth by the integrated NDVI (INDVI) in May. The rate of change in primary production during green-up (early May to early July) was estimated as (1) the maximal slope between any two successive bimonthly NDVI values during this period and (2) the slope in NDVI between early May and early July. The maximal slope in NDVI was negatively correlated with lamb growth and survival in both populations of bighorn sheep, growth of mountain goat kids, and survival of Alpine ibex kids, but not with survival of mountain goat kids. There was no effect of INDVI in May and of the slope in NDVI between early May and early July on juvenile growth and survival for any species. Although rapid changes in NDVI during the green-up period could translate into higher plant productivity, they may also lead to a shorter period of availability of high-quality forage over a large spatial scale, decreasing the opportunity for mountain ungulates to exploit high-quality forage. Our results suggest that attempts to forecast how warmer winters and springs will affect animal population dynamics and life histories in alpine environments should consider factors influencing the rate of changes in primary production during green-up and the timing of vegetation onset.     

Variability and its effect on the 24h chlorophyll budget of a small marine basin

In an intensive study (lasting 25 h) of the production, export and grazing of phytoplankton in a small marine basin, it was found that 58% of the production (11% of the total standing stock) was lost by exchange with the sea and 34% was consumed by grazing of zooplankton. The measured production of phytoplankton could be balanced, to within a few percent, against grazing, export, and a small, measured, net change in the total standing stock of the basin. Large variations were observed in concentrations of chlorophyll and zooplankton at the mouth of the basin over the 25 h period. These variations were associated with changes in the height of the tide, but were about 2^1/2 h out of phase with it. Strong negative correlations were observed between chlorophyll and transport, such that only 35% of the chlorophyll exported was exchanged via the mean flow, while 65% was exchanged via the fluctuations. The correlation was even more striking with zooplankton, for which virtually all the export was associated with the fluctuations in the transport. Time series observations in the centre of the basin revealed considerable short-term variability in both chlorophyll and zooplankton, but the variations were smaller than those observed at the mouth of the basin, and the phase lag with the tide was longer. The variability studies enable suggestions to be made about more economical design of sampling programs, but illustrate the difficulty of providing verification data for any continuous model of primary production in such a basin.Bedford Institute Contribution No. 231.Canadian Contribution to IBP No. 97.     

Bacterioplankton in the coastal euphotic zone: Distribution,activity and possible relationships with phytoplankton

Bacterioplankton were studied in the euphotic zone of the Southern California Bight, USA, with special attention to biological factors affecting bacterial distribution and activity. Measurements were made of bacterial abundance, thymidine incorporation into acid insoluble material, primary production (particulate and dissolved), chlorophyll, phaeopigments, total microbial ATP, particulate organic carbon and nitrogen, dissolved organic carbon, dissolved primary amines, and glucose and thymidine turnover rates. The data were analyzed by pairwise rank correlations with significance tested at the P<.005 level. Bacterial abundance and thymidine incorporation both declined progressively with increasing distance from shore (to 100 km); similar trends occurred for the phytoplankton, with several stations having subsurface maxima. Bacterial abundance, thymidine incorporation, and thymidine and glucose turnover rates were all significantly correlated to each other, suggesting they are comparable as relative measures of bacterial activity. Thymidine incorporation per cell, an indicator of specific growth rate, was not correlated to bacterial abundance, suggesting density independent specific growth rates. Bacterioplankton growth rate was evidently influenced more by the standing stock of phytoplankton than by the primary production of the phytoplankton. Thus, bacterial growth may possibly be stimulated by leakage of dissolved organic matter not so much from healthy photosynthesizing cells as from phytoplankton being disrupted and incompletely digested during predation by the zooplankton and nekton.     

Strong variability in bacterioplankton abundance and production in central and western Bay of Bengal

With large influx of freshwater that decreases sea-surface salinities, weak wind forcing of <10 m s⁻¹ and almost always warm (>28°C) sea-surface temperature that stratifies and shallows the mixed layer leading to low or no nutrient injections into the surface, primary production in Bay of Bengal is reportedly low. As a consequence, the Bay of Bengal is considered as a region of low biological productivity. Along with many biological parameters, bacterioplankton abundance and production were measured in the Bay of Bengal during post monsoon (September–October 2002) along an open ocean transect, in the central Bay (CB, 88°E) and the other transect in the western Bay (WB). The latter representing the coastal influenced shelf/slope waters. Bacterioplankton abundances (<2 × 10⁹cells l⁻¹) were similar to those reported from the HNLC equatorial Pacific and the highly productive northern Arabian Sea. Yet, the thymidine uptake rates along CB (average of 1.46 pM h⁻¹) and WB (average of 1.40 pM h⁻¹) were less than those from the northwestern Indian Ocean. These abundances and uptake rates were higher than those in the oligotrophic northwestern Sargasso Sea (<7 × 10⁸ cells l⁻¹; av 1.0 pM h⁻¹). Concentrations of chlorophyll a (chl a), primary production rates and total organic carbon (TOC) were also measured for a comparison of heterotrophic and autotrophic production. In the WB, bacterioplankton carbon biomass equaled ∼ 95% of chl a carbon than just 31% in the CB. Average bacterial:primary production (BP:PP) ratios accounted for 29% in the CB and 31% in the WB. This is mainly due to lower primary productivity (PP) in the WB (281 mg C m⁻² d⁻¹) than in the CB (306 mg C m⁻² day⁻¹). This study indicates that bacteria–phytoplankton relationship differs in the open (CB) and coastal waters (WB). Higher abundance and contrastingly low bacterial production (BP) in WB may be because of the riverine bacteria, brought in through discharges, becoming dormant and unable to reproduce in salinities of 28 or more psu. Heterotrophic bacteria appear to utilize in situ DOC rather rapidly and their carbon demand is ∼50% of daily primary production. It is also apparent that allochthonous organic matter, in particular in the western Bay, is important for meeting their carbon demand.     

In situ grazing rate of the copepod population in the western subarctic North Pacific during spring

Time series sampling with a multi-layer plankton sampler was carried out in the western subarctic North Pacific during spring 1991. Neocalanus cristatus, N. flemingeri and Eucalanus bungii dominated and accounted for 88.5% of the copepod population in volume. Neocalanus spp. were distributed in the upper mixed layer, while E. bungii was mainly distributed between 120 and 300 m throughout the day and night. In contrast, Metridia pacifica, Pleuromamma scutullata and Gaetanus simplex showed clear diel vertical migration. Grazing activities were estimated simultaneously by gut fluorescence. Nocturnal grazing was observed for diel migrating species. Neocalanus spp. did not have a diel feeding rhythm and had relatively low gut fluorescence. E. bungii was considered to be dormant during the observation period. The estimated grazing rate of the copepod population on phytoplankton was 1.4 to 2.0% of the primary production while the metabolic requirement was 8.3 to 12.4% of the primary production. These facts suggest that the copepod population was unimportant as primary consumers and that microzooplankton plays a much more important role in sustaining low standing stock of phytoplankton and a high nutrient concentration in the western subarctic Pacific Ocean.     

Mechanisms of production and fate of organic phosphorus in the northern Adriatic Sea

In the period from 1980 to 1984 organic phosphorus, nutrients, primary production rates (¹⁴C), chlorophyll a (chl a) standing crops, and basic oceanographic parameters were measured during 23 cruises at six stations in the open waters of the northern Adriatic Sea. These waters are significantly influenced by polluted Po River discharge. Organic phosphorus was correlated with several parameters which characterize phytoplankton activity and organic matter decomposition processes. In the late winter-spring period, organic phosphorus is produced during phytoplankton blooms. It is hypothesized that microzooplankton grazing is the main factor increasing the organic phosphorus concentrations in summer (up to 1.1 mol 1^-1). Fall and winter had much lower values (below 0.3 mol 1^-1) due to remineralization processes and an increased water mass exchange between the northern and central Adriatic regions. The direct contribution of organic phosphorus by freshwater discharge was not found to be significant. The higher organic phosphorus concentrations that can occur in low salinity waters are most likely due to their increased capability to support primary production.