Showing papers on "Productivity (ecology) published in 1983"

The Ecological Role of Water-Column Microbes in the Sea*

Abstract: Recently developed techniques for estimating bacterial biomass and productivity indicate that bacterial biomass in the sea is related to phytoplankton concentration and that bacteria utilise 10 to 50 % of carbon fixed by photosynthesis. Evidence is presented to suggest that numbers of free bacteria are controlled by nanoplankton~c heterotrophic flagellates which are ubiquitous in the marine water column. The flagellates in turn are preyed upon by microzooplankton. Heterotrophic flagellates and microzooplankton cover the same size range as the phytoplankton, thus providing the means for returning some energy from the 'microbial loop' to the conventional planktonic food chain.

Biological Consequences of El Niño

Abstract: Observations of the 1982-1983 El Nino make it possible to relate the anomalous ocean conditions to specific biological responses. In October 1982 upwelling ecosystems in the eastern equatorial Pacific began a series of transitions from the normal highly productive condition to greatly reduced productivity. The highly productive condition had returned by July 1983. Nutrients, phytoplankton biomass, and primary productivity are clearly regulated by the physical changes of El Nino. Evidence from 1982 and 1983 also suggests effects on higher organisms such as fish, seabirds, and marine mammals, but several more years of observation are required to accurately determine the magnitude of the consequences on these higher trophic levels.

Productivity and nutrient cycling in taiga forest ecosystems

Abstract: This paper considers the productivity and nutrient cycling in examples of the major forest types in interior Alaska. These ecosystem properties are examined from the standpoint of the control exert...

The relationship between nutrient availability, shoot biomass and species richness in grassland and wetland communities

Abstract: The relationship was studied between shoot biomass, nutrient concentration in the soil and number of species per unit area. The study was carried out in two different parts of the Netherlands, the Gelderse Vallei (east of Amersfoort) and the Westbroekse Zodden (northwest of Utrecht). Four series of vegetation and soil samples were taken: one series in grassland and wetland communities, one series in grassland communities, one series in fen communities and one series in only one wetland community. The two series in grassland communities show a negative correlation between shoot biomass and species number and a positive correlation between shoot biomass and nutrient concentration in the soil. The opposite was found in the series in the fen communities: there was a positive correlation between species number and shoot biomass and a negative correlation between shoot biomass and nutrient concentrations. The series of samples that had been taken in only one wetland community showed an optimum curve for the relation between shoot biomass and number of species. It is concluded that in the plant communities studied the species richness per unit area increases with increasing productivity at low production levels ( 400–500 g/m2).

Relationship of marsh elevation, redox potential, and sulfide to Spartina alterniflora productivity

Abstract: L'etude precise les relations entre la concentration en sulfures, le potentiel redox, l'azote ammoniacal mineral et la productivite primaire de S. alterniflora dans les marais sales de Louisiane

Halimeda biomass, growth rates and sediment generation on reefs in the Central Great Barrier Reef province

Abstract: The average biomass ofHalimeda per m2 of solid substratum increased progressively on a series of reefs situated at increasing distances from the shore in the central Great Barrier Reef. There was none on a reef close inshore, increasing to nearly 500 g m−2 total biomass (≃90% calcium carbonate) on an oceanic atoll system in the Coral Sea. The biomass measured contained 13 species ofHalimeda but was dominated by only two species,H. copiosa andH. opuntia, except on the atoll whereH. minima was dominant. Three sand-dwelling species were also present but did not occur anywhere in substantial quantities. Growth rates of the dominant species were measured bv tagging individual branch tips. A mean value of 0.16 segments d−1 was recorded but 41% of the branch tips did not grow any new segments whilst only 1% grew more than one per day. The number of branch tips per unit biomass was very constant and has been used in conjunction with growth rates and biomass to calculate productivity rates, and thence sedimentation, in the lagoon of one of the reefs. Biomass doubling time of 15 d and production of 6.9 g dry wt m−2 d−1 are considerably higher than previously reported values forHalimeda vegetation and there was little seasonal change detected over a whole year. Those values indicate annual accretion of 184.9 g m−2 year−1 ofHalimeda segment debris over the entire lagoon floor (5.9 km2) of Davies Reef, equivalent to 0.13 mm year−1 due toHalimeda alone, or 1 m every 1,892 years when other contributions to that sediment are taken into account.

Nitrogen productivity of some conifers

Abstract: Nitrogen productivity, expressed as annual yield of foliage per unit of nitrogen in the foliage, is recommended for interpreting responses to changes in nitrogen availability. This index can be directly coupled to growth and is well suited for application in mathematical analyses of tree or forest growth dynamics. This paper demonstrates that the nitrogen productivity decreases predictably as biomass increases probably as a result of the reduction in irradiance as the canopy becomes more dense. For five species of conifers from northern latitudes (Piceaabies Karst., Pseudotsugamenziesii Mirb. Franco, Pinusnigra var. maritima (Ait.) Melv., Pinusresinosa Ait., and Pinussylvestris L.) nitrogen productivity is shown to decrease linearly with increasing needle biomass. For a particular species, these regressions allow for estimation of maximum needle biomass.

Qualitative and quantitative interactions between microphytobenthos and herbivorous meiofauna on a brackish intertidal mudflat

Abstract: Micro- and meiofauna are the predominant consumers of diatoms on a brackish intertidal mudflat. The impact of grazing on the benthic diatom populations was studied by field observations and feeding experiments on a few abundant members of the community. Only small fractions of the microphytobenthic biomass and production are converted by herbivores. A hypothesis is presented explaining the growth kinetics and productivity of diatom populations and the inefficient transfer of carbon into herbivore foodchains. Data on feeding rate and population dynamics of the nematode species, Eudiplogaster pararmatus, are discussed in view of the seasonal succession of edible diatom species.

The bottom‐ice microalgal community from annual ice in the inshore waters of east antarctica1

Abstract: The structure, productivity and heterotrophic potential of an extensive microalgal community growing on the underside of sea ice near the Australian Antarctic Station of Casey, are described Underwater observations made near the Australian Antarctic stations of Davis and Mawson are also reported This community develops during September, is largely suspended from the bottom surface of annual sea ice and often extends into the underlying water column as conspicuous strands up to 15 cm long The algal community structure in the strands is dominated by an unidentified tube diatom belonging to the Amphipleura/Berkeleya group and chains of a species of Entomoneis cf Amphiprora paludosa var hyperborea (Grunow) Cleve Unlike previously described bottom ice environments, a brash ice layer under the hard sea ice is absent Living cells, predominantly Nitzschia frigida Grunow, also occur in microbrine channels in the bottom 3 cm of the ice Maximal primary production rates of 81 μg C · L-1· h-1 occurred during November, then began declining near the end of December Minimal rates (28 μg C · L-1· h-1) were reached in mid-January and coincided with changes in the physical structure of the sea ice and in the stability of the water column An abundant epibacterial community associated with the microalgal strands assimilated 3H-labelled amino acids suggesting significant heterotrophic recycling of dissolved organic matter Turnover times of assimilated amino acids in the bottom ice community averaged 55 h during November while negligible turnover of these substrates occurred in the water column 15 m below the ice These bottom ice communities have higher primary productivity than typical brash ice communities; they are also accessible to marine herbivores and so may be more important to the Antarctic marine food chain than previously supposed

Productivity Gradients in Salt Marshes: The Response of Spartina Alterniflora to Experimentally Manipulated Soil Water Movement

Abstract: Increasing the subsurface drainage in a stand of intermediate-height smooth cordgrass Spartina alterniflora Loisel. caused significant increases in mean shoot height and above ground production in a single growing season, and continued through the second year of the experiment. The results 1) strongly support the hypothesis invoking a gradient in soil water movement as the major general determinant of productivity by S. alterniflora and 2) indicate factors in addition to salinity stress as possible specific regulators of salt marsh productivity.

Ecosystem processes : mineral cycling, productivity and man's influence

Abstract: D.- 1 Nutrient Allocation in Plant Communities: Mineral Cycling in Terrestrial Ecosystems.- 2 Nutrient Cycling in Freshwater Ecosystems.- 3 Nutrient Cycling in Marine Ecosystems.- 4 Modeling of Growth and Production.- 5 Productivity of Agricultural Systems.- 6 Productivity of Grassland and Tundra.- 7 Productivity of Desert and Mediterranean-Climate Plants.- 8 Productivity of Temperate, Deciduous and Evergreen Forests.- 9 Productivity of Tropical Forests and Tropical Woodlands.- 10 Phytoplankton Productivity in Aquatic Ecosystems.- 11 Effects of Biocides and Growth Regulators: Physiological Basis.- 12 Effects of Biocides and Growth Regulators: Ecological Implications.- 13 Eutrophication Processes and Pollution of Freshwater Ecosystems Including Waste Heat.- 14 Ecophysiological Effects of Atmospheric Pollutants.- 15 Ecophysiological Effects of Changing Atmospheric CO2 Concentration.- 16 Man's Influence on Ecosystem Structure, Operation, and Ecophysiological Processes.- Author Index.- Taxonomic Index.- Subject Index for Parts A-D.

Light and the annual variation of oxygen- and carbon-based measurements of productivity in a macrophyte-dominated river1

Abstract: Daily integrals of primary productivity were measured for 369 days in the macrophytedominated Gryde River (NW Jutland, Denmark) between July 1979 and September 1980. All seasons were distinct, with high primary productivity during summer, a gradual transition in autumn, low primary productivity in winter, and a rapid transition to summer conditions during April. Those seasons corresponded with the condition of the macrophytes, with high biomass and surface area during summer, a gradual decline in autumn, senescence during winter, and development of new shoots during April and May. The remarkably constant relationship between daily integrals of primary productivity and light (in comparison with that in rivers without macrophytes) could be described during both summer and winter by a hyperbolic equation, with more shade adaptation but less maximum photosynthesis during winter than during summer. The hyperbolic relationship held for both oxygen- and carbonbased measurements. The mean value for the photosynthetic quotient (P-Q.) was close to one, suggesting little transport of oxygen and inorganic carbon to or from roots. We could not discern effects on primary productivity of other variables such as temperature, which seemed unimportant in comparison to light.

Bioenergetic and Community Changes in Intertidal Aufwuchs Grazed by Littorina Littorea

Abstract: Grazing by Littorina littorea on Aufwuchs grown on glass substrata resulted in sub- stantial changes in the bioenergetics and community structure of the microalgae. At all grazer densities (13-504 snails/m2) standing crop biomass of the Aufwuchs was markedly reduced compared to that on control (ungrazed) substrata. Both in situ dry mass and organic carbon per square decimetre decreased as snail density increased; however, nutritional quality was improved with increase in density of grazers. Carbon per unit dry mass of Aufwuchs was higher at all grazer densities than for controls, and nitrogen per unit dry mass increased as grazer density increased. C:N ratio of the Aufwuchs decreased from 10:1 at 13 snails/m2 to 2:1 at 504 snails/m2. A computed assessment of Aufwuchs productivity based on snail intake necessary for bioenergetic maintenance derived from respiration measurements indicated that grazing at moderate levels increased microalgal productivity by 88% over control. Both microalgal abundance and richness decreased as Littorina density increased. Grazing reduced the number of taxa to 50%' of that of control Aufwuchs at low snail densities and to <30% of that of controls at high snail densities. Five taxa (including the genera Achnanthes, Nitzschia, Amphora, and Cocconeis) appeared resistant to grazing and in terms of number of cells per square centimetre comprised 73% of the cells on highly grazed substrata, compared to 7.5% on control substrata. Grazing by Littorina littorea on Aufwuchs involves ingestion of a mixture of prey; possibly only passive selectivity; bioenergetic increase in certain nutritional parameters such as proportion of or- ganic carbon, nitrogen, and possibly per unit mass productivity; and reduction in community param- eters such as abundance, richness, and diversity.

Abundance and productivity of protozoa in chalk streams

Abstract: The distribution and abundance of protozoa in two chalk streams were studied. Particular attention was given to the ciliates and amoebae associated with the dominant submerged macrophyte, Ranunculus penicillatus. Highest numbers of protozoa occurred in habitats in the stream where the current velocity was reduced. Mean standing crops of ciliates, flagellates and amoebae were 32.5, 2.9 and 2.0 mg dry wt m−2 of stream bed respectively. Estimates of production and respiration rates by field populations of ciliates and amoebae were made for one type of habitat within the streams. The results are compared with published data on the productivity of protozoa in other habitats and of other invertebrates within the chalk stream ecosystem. The limitations of such productivity estimates are discussed.

Biomass and productivity of white spruce stands in interior Alaska

Abstract: A total of 58 trees was sampled from eight stands across a large area of interior Alaska. Regression equations were developed to estimate standing aboveground biomass for 22 white spruce (Piceaglau...

Productivity of cordgrass,Spartina alterniflora, estimated from live standing crops, mortality, and leaf shedding in a Virginia salt marsh

Abstract: Net annual productivity of tall and medium form cordgrass,Spartina alterniflora, was estimated by a new clip sampling method in a sloping foreshore salt marsh at Wallops Island, Virginia. This method measured live standing crops only, to avoid problems of measuring dead biomass inherent in other methods. Losses from live standing crops by shoot mortality and by leaf shedding were estimated from these measurements and added separately to production of live tillers and of live culms. This allowed quantification of various components of production.Spartina tillering in different zones of the marsh produced 62 to 211 g dry weight per m2 per yr. Tiller mortality removed 37 to 106 g per m2 per yr from live standing crops. Culms produced 348 to 1,132 g per m2 before flowering and die-back. Culm mortality removed 28 to 246 g per m2 before flowering. Leaf shedding removed an additional 83 g per m2 in tall formSpartina. Altogether, net annual productivity These estimates are much higher than previous estimates of productivity and standing crops inSpartina marshes nearby.

An assessment of the phytoplankton biomass and primary productivity of Parakrama Samudra, a shallow man-made lake in Sri Lanka

Abstract: Phytoplankton biomass was assessed from microscopic counts and from measurements of chlorophyll-a. Figures ranged from 2 to 35 mg FW 1-1(FW, fresh weight) and from 5 to 105 µg Chl-a 1-1, respectively. The phytoplankton assemblage is dominated by blue-green algae (Anabaenopsis raciborskii, Lyngbya circum- creta, Microcystisspp.) and diatoms (Melosira granulata). In addition, various green algal species occur in low numbers. OnlyMonoraphidiumexhibits higher numbers. Primary productivity, assessed by both the14C technique and the oxygen light and dark bottle method, ranged from 3.8 to 14.7 g O2m-2day-1. Most of the productivity can be attributed to the algal fraction smaller than 33 µm. Photosynthetic efficiency was highest in the afternoon as a result of greater phosphorus availability because of increased phosphatase activity. Community respiration (0.002-0.400 mg O21-1h-1) was stimulated by light and is not a constant fraction of photosynthesis. Specific rates per unit chlorophyll-a were high. Photosynthesis is, to a great extent, controlled by light and phosphorus availability. Newly formed biomass is exploited by zooplankton (mainly rotifers) and herbivorous fish (mainlySarotherodon mossambicus). Biomass levels in the reservoir are largely affected by the flow-through, which is dependent on irrigation management activity.

Freshwater aquatic plant biomass production in Florida.

Abstract: About 8% (1.2 million ha) of the total surface area of Florida is occupied by freshwater. Many of these water bodies are eutrophic. Nutrients present in these water bodies can be potentially used to culture aquatic plants as a possible feedstock for methane production. This paper summarizes the results of known research findings on biomass production potential of freshwater aquatic plants in Florida and identifies key research needs to improve the quality and quantity of biomass yields. Among floating aquatic plants, biomass yield potential was in the order of water-hyacinth > water lettuce > pennywort > salvinia > duckweed > azolla. Pennywort, duckweed, and azolla appear to perform well during the cooler months compared to other aquatic plants. Among emergent plants, biomass yield potential was in the order of southern wild rice > cattails > soft rush > bulrush. Cultural techniques, nutrient management, and environmental factors influencing the biomass yields were discussed. 68 references.

Total Dissolved Solids as a Predictor of Lake Biomass and Productivity

Abstract: Total dissolved solids (TDS) and chlorophyll a were not related in 25 lakes which were all off the Precambrian Shield. Both on-shield and off-shield lakes were included in the previous reports whic...

Productivity, detritus flux, and nutrient cycling in a Carex lyngbyei tidal marsh

Abstract: Net annual primary production of a sedge Carex lyngbyei dominated tidal marsh in the Fraser River estuary, British Columbia, Canada was 634 g ash-free dry weight (AFDW) per m2 per yr (687 g dry weight per m2 per yr). Mean maximum shoot elongation during the short (May to August) growing season was 1.88 cm per day from overwintering shoots. The maximum aboveground standing crop of 690 g AFDW per m2 represented only 25% of the total below-ground biomass, which appears to be controlling most of the critical life history processes of the sedge marsh. An estimate of 14 percent of the aboveground standing crop was lost through leaching of dissolved organic carbon from the growting plant. Aboveground tissue losses, which were negligible during the growing season, occurred primarily via translocation in autumn and tidal export during the winter. In situ measurements showed that of the original maximum standing crop, approximately 38%, 37%, and 25% were lost by downward translocation, tidal export, and sediment burial, respectively. Based on changes in above and belowground nutrient pools, rapid spring (May to late June) uptake rates of 109 mg N per m2 per day and 23.0 mg P per m2 per day by shoots were followed by downward translocation rates of 44.8 mg N per m2 per day and 12.2 mg P per m2 per day during late June to the end of August. Aboveground leaching rates were estimated as 23.9 mg N per m2 per day and 7.8 mg P m2 per day and belowground uptake rates as 100 mg N per m2 per day and 26 mg P per m2 per day; root uptake occurred primarily after late June. Nutrient levels in decomposing litter more than doubled over the winter period showing a pattern of nutrient enrichment characteristic of marsh ecosystems. *** DIRECT SUPPORT *** A01BY023 00004

Heterotrophic Bacterial Biomasses, Activities, and Productivities Within The Fraser River Plume

Abstract: Most of the microorganisms within the silt-laden Fraser River water are bacteria, the majority of which are attached to detritus and suspended silt However, within surface water of the Strait of Georgia bacteria constitute only about 4% of the microbial biomass; most are free-living Within the plume, which results when the freshwater of the Fraser River mixes with the seawater of the Strait of Georgia (salinity of about 27‰ and containing mainly phytoplankton) stimulations of bacterial glucose heterotrophic activity and productivity occur throughout the year Bacterial production is a relatively greater proportion of the total microbial, ie both algal and bacterial production, in the winter than in the spring or fall Preliminary evidence indicates that the stimulation of bacterial activity and productivity may be, at least partially, due to entrainment of nitrate and phosphate-rich deep water of the Strait of Georgia into the Fraser plumeKey words: Fraser plume, bacteria, production, heterotrophic a

Bacterial biomass and productivity in sediments, stromatolites, and water of hamelin pool, shark bay, Western Australia

Abstract: Heterotrophic bacterial biomass and growth rates were examined in stromatolites formed from four different types of benthic cyanobacterial mats. Bacteria in algal mats were counted using direct microscopy and biomass was estimated from the numbers of bacteria. Heterotrophic bacterial growth rates were estimated from the rate of incorporation of tritiated thy‐midine into DNA. Pustular mat, which occurs in the upper in‐tertidal zone, contained relatively few bacteria in the surface layers (0–5 mm), having about 0.2 x 106 cells mm‐3, or 20 mgC m‐2 per millimetre depth. Other mats in the lower intertidal and subtidal zones had from 1 x 106 cells mm‐3 to 8 x 106 cells mm‐3. Heterotrophic bacterial productivities were 2.1 to 5.0 mgC m‐2 h‐1. Turnover times were an average of 1 day in the sandy sediment and 5 days in the colloform mat. Although these results are minimum estimates, they indicate that heterotrophic bacteria contribute substantially to the carbon cycle in stromatolites, by utilizing about ...

Biomass distribution and productivity in a poplar plantation.

Abstract: The distribution of biomass in various tree components and productivity of a 8 years old plantation of Populus deltoides have heen discussed. The total biomass is of the order of 86 tonnes/ha of which 83 per cent is being contributed by the above-ground parts and 17 per cent by the roots.

Plankton productivity and biomass in a tributary of the upper Chesapeake Bay. I. Importance of size-fractionated phytoplankton productivity, biomass and species composition in carbon export

Abstract: Phytoplankton productivity, community composition and biomass were determined over a nine-month period in brackish waters of the lower Gunpowder River, a tributary of Chesapeake Bay. Primary productivity followed expected seasonal magnitudes for temperate estuaries with rates exceeding 142·4 mg C m−3 h−1 in July through September 1979 and minimum rates of 1·6 mg C m−3 h−1 in February 1980. Annual primary production was estimated at 45·5 gC m−2. Cell numbers were highest in August, September and November with cyanophytes dominating the planktonic algae. Primary productivity, chlorophyll concentrations and cell densities were dominated by nanoplanktonic forms (< 10 μm) through-out the study. Phytoplankton carbon calculated from cells volumes exceeded nutritional requirements of the pelagic herbivores in all months suggesting a mean daily export (to the bay or sediments) of 1607 mg C m−3 d−1.