Showing papers on "Productivity (ecology) published in 1976"

Photosynthetic rates of benthic marine algae in relation to light intensity and seasonal variations

Abstract: The effect of light intensity on rate of photosynthesis was measured at irregular intervals over a 12-month period for 22 benthic marine algae in the western Baltic Sea. In most species photosynthesis (mg O2·g dry weight-1·h-1) was highest in spring and summer, corresponding to the seasonal growth pattern of the algae. In winter all the species showed adaptation of the light compensation point. Highest productivity was shown by algae which are: short-lived annual species rather than perennials, eulittoral rather than sublittoral, and which possess sheet-like or filamentous thalli rather than coarsely branched forms. These factors are clearly inter-related.

Energetics of a Suburban Lawn Ecosystem

Abstract: A study of the energetics of a suburban lawn was conducted in 1972-73 in Walnut Creek, California USA. Several major components of the annual primary and sec- ondary production were measured, including man's role as manager and experimenter in the system. The system was extremely productive with net productivity of 1,020 g/m2 per yr compared to cornfields with productivity of 1,066 g/m2 per yr and exceeding tall grass prairie values of around 1,000 g/m2 per yr. Homopterans, with maximal values of 19 mg/M2 were plentiful; other typical grassland species, like Araneida, were scarce, representing only 1% by weight of the total invertebrate population. Food utilization per unit area by suburban birds con- siderably exceeded natural grassland bird utilization (46 kcal/m2 per yr vs. 1.01-2.33 kcal/m2 per yr); lawns are ideal foraging sites for open area adapted, flock-feeding species. Man was the dominant consumer in the community, accounting for 10% of the herbivory and nearly 100% of the scavenging. Energy inputs (labor, gasoline, fertilizer, etc.) amounted to 578 kcal/m2 per yr, equalling or exceeding corn production for a comparable net produc- tivity, but not necessarily utilitarian return.

Ecosystem and macrophyte primary production of the Fort River, Massachusetts

Abstract: Primary production and ecosystem respiration of the Fort River ecosystem, a medium size (mean discharge 1.4 m3/sec) lowland stream in central Massachusetts, U.S.A., were measured using diurnal oxygen techniques from May 1972 to November 1973. During the summer of 1973, vascular hydrophyte production was measured with a modified cropping technique. Whole ecosystem gross primary production ranged from 0.44 g O2/m2:day in winter to 6.50 g O2/m2.day in summer, and averaged 1.78 g O2/m2.day for 12 months. Mean ecosystem respiration was 3.65 g O2/m2.day for 12 months. Mean ecosystem respiration was 3.65 g O2/m2.day. Macrophyte gross production (59.9 g O2/m2.year) constitutes 9.2% of annual ecosystem productivity and 15.2% of summer primary production. Macrophytes were little grazed and entered food webs only after death, as detritus. Decomposition occurred near the site of production at relatively rapid rates, thus transport of dead macrophyte material in stream water was low. Data from this and other stream ecosystems suggest that in general, streams are only moderately productive ecosystems which depend to varying degrees on watershed-derived organic matter inputs.

Productivity of epipelic algae in tundra ponds and a lake near barrow, alaska'

Abstract: The biomass and productivity ((14)C) of epipelic benthic algae were measured in several tundra ponds and in a lake near Point Barrow, Alaska. In the ponds (50 m diam X 20 cm deep) the epipelic algae (mostly Chlorophyta and Cyanophyta) are most abundant in the upper 2 cm of sediment but their total biomass is low (0.5—1.5 g C°m(—2)) and no surface mat of cells forms, largely because of the continuous mixing of the flocculent surface sediments by a variety of benthic invertebrates. Epipelic photosynthesis is limited to a 3—mo thaw period (June through August) and has a single broad peak in mid—July of ° 200 mg C°m(—2)° day(—1). Epipelic production ranged from 10—4 g C m—2 yr—1 (1971—1973), compared to 1 g C m—2 yr—1 for the pond phytoplankton. In contrast, epipelic production in nearby Ikroavik Lake (12 km2 X 2 m deep) was only 2.3 g C°m(—2)°yr(—1) because of lower light intensities at the sediment surface, lower water temperatures, and a shorter ice—free period than in the ponds. See full-text article at JSTOR

Submergent Macrophytes: Growth Under Winter Ice Cover

Abstract: Densities of 26 submergent macrophyte species were determined in situ regularly for 3 years by individuals using self-contained underwater breathing apparatus (scuba). Although most of these species grew only during the summer, ten maintained high population densities and productivity throughout the winter. Maximum winter photosynthetic activity was 10 to 20 percent of summer rates. Extensive productivity of submergent aquatic plants under winter ice cover has not been well documented.

Plant Standing Crop and Productivity Relations in a Scirpus-Equisetum Wetland

Abstract: Plant standing crop and productivity relations were examined for an extensive marsh complex in southern Quebec, Canada. Forty—five 1—m2 plots were sampled for dry weight shoot biomass, species composition, structure (species density, diversity, height), and soil parameters including nutrient concentrations. (Ca, K, Mg, Na, N, P), pH, organic matter, and water depth. Shoot net productivity and decomposition rates were computed for 20—day intervals across the growing season. Relationships between all parameters were examined by principal components analysis. Dominant emergent species included Scirpus fluviatilis, Equisetum fluviatile, Scirpus validus, Phragmites communis, and Eleocharis palustris. For a 150—day interval, shoot net productivity averaged 6.10 g·m(—2) · day(—1) and terminal standing crop was 845 g/m2. Seasonal productivity showed a strong bimodal pattern with peaks in late July (12.90 g°m(—2) · day(—1) and midSeptember 4.73 g°m(—2) · day(—1). Species typical of deep water showed much earlier and higher peak productivity than this general pattern but net shoot productivity as of short duration. Two—thirds of annual litter production was lost by export. Complete decomposition of remaining litter occurred within the next growing season. Temperature and decomposition rate maxima coincided with peak productivity in July and decreased exponentially through October. Among edaphic parameters, soil K had the highest correlation (r = 0.49**) with standing crop while soil N had the highest correlation with shoot net primary production (r = 0.39**). Soil P correlated negatively with all production and soil nutrient parameters except soil Mg levels. It was the only nutrient with a soil concentration maximum in shallow water. Other nutrients attained maximum levels at an intermediate point on the water depth gradient. Maximum litter standing crop occurred at this point, coinciding closely with changes in soil cation levels. While shoot density and standing crop followed these trends, they coincided more closely with changes in soil anion concentrations (nitrogen, hydrogen). Sedimentation and nutrient uptake associated with high stem density and standing crop were shown to be important factors in site enrichment. Shoot net primary productivity and standing crop correlated negatively with all measures of species diversity. Variety and equitability decreased from 8.00 species and 0.96 bits/m2 in Scirpus validus stands of deep water to 2.00 species and .01 bits/m2 in shallow stands of S. fluviatilis. Sparse canopy cover and high levels of disturbance in S. validus stands made possible the coexistence of a rich variety of aquatic life forms not possible under conditions of intense competition typical of S. fluviatilis.

Productivity relations in a Carex-dominated ecosystem.

Abstract: Seasonal and total primary productivity was measured for a Carex meadow in southern Quebec, Canada. Forty-five one-meter2 plots were sampled for dry weight biomass, species composition, structure (species density, diversity, height) and soil parameters including macronutrient concentrations (Ca, K, Mg, Na, N, P), pH, organic matter, and water depth. Shoot net productivity and litter decomposition rates were computed for 20-day intervals May-September, inclusive. Relationships between all parameters were examined by principal components analysis.Dominant species included Carex lacustris, C. aquatilis, Calamagrostis canadensis, and Typha angustifolia. For a 130-day growth period, mean shoot net productivity was 6.3 g·m-2· da-1 and terminal standing crop 807 g·m-2. Terminal standing crop was very close to above ground biomass predicted by the Gorham equation based on thermal relations for Carex ecosystems and to total accumulated litter mass (779 g·m-2). Seasonal production showed a strong bimodal pattern with peak productivities in mid-June (15.3 g·m-2·da-1) and mid-July (4.3 g·m-2·da-1). Decomposition of the previous year's litter was 81% complete by late September.Soil fertility, fire incidence, and topographic position were the three most important gradients resolved by principal components analysis. The first component distinguished sediment-rich Typha angustifolia communities near open water from oligotrophic stands of Carex spp. on central areas of the meadow. Production levels correlated closely with extractable soil calcium (r=0.40**) and phosphorus levels (r=0.39**). Species diversity and stem density related inversely to productivity on this component. Fire incidence (component II) had a marked effect on species diversity due to surface scarification and removal of litter mass. Component III was a topographic gradient separating composition, and community structure.Magnesium and sodium levels decreased from upland to open water. Soil phosphorus increased markedly at water's edge related to mineral input by sedimentation. Pattern of N, P, K, and Ca coincided closely with total shoot production and litter mass levels suggesting closed biotic cycles of these elements.A model accounting for species diversity levels in Carex meadow was formulated based on the assumption that high productivity results in competitive species elimination.

Release of dissolved organic matter by photosynthesizing algae in Lake Kinneret, Israel*

Abstract: Summary The incorporation of inorganic carbon in particulate and dissolved organic matter by natural populations of photosynthesizing algae has been studied in Lake Kinneret, Israel, from August 1972 to December 1973. The release of dissolved organic material was directly related to the rates of particulate productivity. However, the percentage of extracellular release (PER) of dissolved organic compounds showed an inverse relationship with chlorophyll a concentrations. Mean PER values (for the trophogenic layer) over the experimental period were 3·7%, and were lowest during the exponential growth phase of the annual dinoflagellate bloom (mean PER = 1·9%). Highest PER were measured in deep, light-limited samples (mean = 31·7%; s.d.· 21·9%). In a dense metalimnic layer of photosynthetic sulphur bacteria (Chlorobium phaeobacterioides), PER was not as extremely high as has been reported for a similar layer in Lake Wadolek, Poland. Although the amounts of dissolved organic matter released by phytoplankton in Lake Kinneret were low, they may have significance as growth modulators and as substrates for heterotrophic organism.

Limnological studies of and primary production in temple pond ecosystems

Abstract: Three temple ponds with permanent blooms of blue green algae were highly productive. They all showed high alkalinity, hardness, electrical conductivity and pH. Organic carbon and nitrogen were highest in Sarvatheertham pond—60 to 79.6 mg./l. C and 4.10 to 7.60 mg./l. N. In Tamaraikulam it was 16.5 to 20.3 mg. C/l. and 1.03 to 1.32 mg. N/l. In Sarvatheertham, the gross production ranged from 2.85 to 20.72 g. O2/m.2/d. Self shading by blanket algae of blue greens reduced productivity in Sarvatheertham, where a persistent thermal and biochemical stratification was noted. Very high organic carbon and nitrogen contents were noted in Sarvatheertham pond. The dry weight of plankton in this pond ranged from 430 to 900 mg./l. Productivity computed from diurnal changes in alkalinity and dissolved oxygen also revealed a high rate in Ayyankulam, Tamaraikulam and Sarvatheertham in descending order. Very wide fluctuations in pH, both diurnally and depth-wise, were recorded in Sarvatheertham and to a lesser extent in the other two ponds. Photosynthetic efficiency was 4.03% in Ayyankulam, 2.09% in Tamaraikulam and 1.56% in Sarvatheertham. By the diurnal oxygen curve method, a gross primary production of 97.5 g. O2/m.2/d was recorded in Ayyankulam.

Primary production of epiphytic algae in a marsh pond

Abstract: The use of artificial substrates for the estimation of epiphytic algal production was evaluated. The primary productivity of epiphytic algae in a marsh pond (Crescent Pond, Delta Marsh, Manitoba) was estimated using a cellulose acetate substrate. Annual production, based on 14C uptake was 26.8 g C m−2 of pond surface area. Production m−2 colonizable surface area was greatest on Scirpus acutus (32.3 g C m−2 year−1), while Potamogeton pectinatus was the most significant substrate in overall pond production (1700 kg C year−1). The organic C content of the epiphytic community was related to rates of productivity.

A Comparison of Seasonal Primary Production of Mojave Desert Shrubs During Wet and Dry Years

Abstract: Estimates of net primary productivity were made for five major shrub species in the northern Mojave Desert during 2 years of contrasting moisture regimes using harvest and gas exchange techniques. Production increased by 224% (harvest) to 260% (gas exchange) in 1973 over 1972. Production gains varied among species depending on whether the species was favored by the cool, moist spring of 1973. Lycium andersonii and L. pallidum, which have high photosynthetic rates and start growth in the early spring, showed the greatest increases. Larrea tridentata and Krameria parvifolia, species adapted to growing under warmer, drier conditions, exhibited the smallest changes in production. Ambrosia dumosa, which has high photosynthetic rates but responds more favorably to warmer spring temperatures than the Lycium species, had moderate production gains. Reasons for the different estimates obtained by these two methods are discussed. INTRODUCTION The determination of primary productivity in terrestrial ecosystems is a necessary but difficult step in providing information on the basic. energy or carbon input into biological systems. Productivity estimates are important for predictive models of a general nature in ecosystem analysis. In general, two methods have been used for net primary production estimates. The first method is a direct harvest technique in which whole plants or samples are clipped throughout the growing season, dried and weighed, and productivity calculated on dry weight per unit area. The second method involves measuring the total CO2 or carbon exchange per weight of photosynthetic organs, and calculating productivity as carbon or biomass fixed minus respiratory losses. There have been several measurements of net primary production and biomass in deserts made by the harvest and other methods (Burk and Dick-Peddie, 1973; Chew and Chew, 1965; Pearson, 1965; Rodin and Bazilevich, 1967). Measurements of CO2 exchange rates in desert plants have been made in the Negev Desert (Lange et al., 1969) and in the North American deserts (Bamberg et al., 1975; Caldwell, 1972; Patten and Dinger, 1969; Strain, 1969, 1970; Strain and Chase, 1966). Attempts at relating some of these gas exchange rates to production are only now being done. The US/IBP Desert Biome is currently obtaining production estimates from several sites in the western United States. 1 Present address: EG&G Environmental Consultants, 9025 E. Kenyon Avenue, Denver, Colorado 80237. 2 Present address: University of Idaho, Research and Extension Center, Route 1, Kimberly, Idaho 83341.

Habitat-Related Patterns of Productivity of the Foliaceous Reef Coral, Pavona Praetorta Dana

Abstract: Reef corals contain mutualistic symbiotic zooxanthellae which photosynthesize and translocate photosynthate to the animal partner, although the animal is capable of tentacular feeding and other heterotrophic activities (Goreau, et al., 1971; Muscatine, 1973; Trench, 1974; Porter, 1974; Muscatine and Porter, 1976). Many workers have examined the photosynthesis of reef corals (McCloskey, et al., 1976) but habitat acclimation has generally been ignored.

The Effect of Current on Periphytic Productivity as Determined Using CARBON-14

Abstract: Productivity measurements of organisms attached to artificial substrates ranged from 6.5 to 7.6 mg C/m/sup 2//hr and were 17 to 65 percent greater in stirred bottles (simulated flow) than under static conditions. Carbon-14 was used to determine the effect of current on the primary productivity of these organisms in six artificial streams at the Flowing Streams Laboratory on the Savannah River Plant (U.S. Energy Research and Development Administration, Aiken, South Carolina, U.S.A.). Seasonal changes in dominant organisms were monitored from June 1973 to March 1974. Estimates of productivity, accumulated biomass, and levels of chlorophyll ..cap alpha.. were compared for possible correlation. Production of chlorophyll ..cap alpha.. ranged from 50 to 381 mg/m/sup 2/, and accumulated biomass ranged from 45 to 181 g/m/sup 2/ on the artificial substrates (glass microscope slides) during the period of study. Productivity of attached organisms was generally an order of magnitude greater than productivity of phytoplankton or tychoplankton. The consistently higher productivity in simulated flowing systems than in static systems tends to cast some doubt on values obtained when lotic communities have been enclosed or isolated in chambers or bottles wthout inducing a current or stirring action.

Organism-Sediment Relationships

Abstract: Productivity in the surface waters of the sea is closely linked with water-sediment-organism processes at the benthic boundary.

Influence of Sediment Inflow on Phytoplankton Primary Productivity in Lake Tahoe (California‐Nevada)

Abstract: Light, nutrient concentrations and phytoplankton photosynthesis were studied in a Lake Tahoe sediment plume during maximum spring runoff. They were compared with conditions in clear lake waters not influenced by inlets. In the plume, nutrient concentrations increased in proportion to sediment density whereas light transmission of water was reduced with little effect on the spectral composition except for red light. Light inhibition of photosynthesis at the lake surface was less pronounced in the plume than in clear water and light limitation occurred more rapidly in deeper layers. Evidence from both lake experiments and laboratory bioassays suggests that iron had the greatest stimulatory effect on both photosynthetic activity and biomass growth at maximum sediment densities near the stream inlet. Because of less surface inhibition, photosynthetic light energy utilization efficiency was usually higher in the sediment plume which occurred in relatively shallow areas near the shore. In order to estimate overall effects of enhanced turbidity associated with nutrient loading on Lake Tahoe's primary productivity, profiles taken in shallow areas near the lakeshore were extrapolated to the maximum depth of photosynthesis. Light limitation would cause decreasing productivity, but nutrient stimulation would make this effect less pronounced. The overall effect would depend on the extent of sediment loading relative to nutrient loading.

Sub-obliterative effects of mine-tailing on marine infaunal benthos

Abstract: The effect of mine-tailing on benthic productivity in a threshold inlet was explored by studies on the polychaete Ammotrypane aulogaster Rathke, 1843. Ammotrypane was chosen as an indicator species of potentially reduced production in the area fringing total benthic obliteration due to its abundance (up to 1017 m−2) at the time of the surveys.

A Model of the Spatial Structure and Productivity of Phytoplankton Populations during Variable Upwelling Off the Coast of Oregon

Abstract: : During the season favorable for coastal upwelling off the western boundary of continents, the local circulation is strongly influenced by occasional wind events of several days' duration. Variability in the wind stress affects the rate of upwelling and ultimately the local biological productivity. To investigate the relationship between wind events and primary production off the coast of Oregon in August 1973, a time-dependent, numerical model of the upwelling circulation was coupled to a complex model of primary and secondary productivity. Primary productivity is a function of nutrient concentration, light intensity and temperature. Advection by a two-cell, upwelling circulation is the major physical mechanism leading to mesoscale patchiness in the phytoplankton, zooplankton, detritus and nutrient fields. The numerical model predicts a phytoplankton and detritus plume for which considerable observational evidence exists. Model predictions of daily primary production during intermittent upwelling are paradoxically comparable to production during strong upwelling. A new formulation for herbivore egestion as a function of food availability is proposed.

Relationships Between Sediment Chemistry and Postglacial Production Rates in a Small Canadian Lake

Abstract: In a chemical investigation of the sediments of a small meromictic lake in southwestern Ontario, Canada, the hypolimnion had evidently become increasingly reductive over most of the postglacial as the lake gradually filled in The ratio of phosphorus to organic matter tended to fall, suggesting that an increasing proportion of precipitated phosphorus had become mobile and re-available to the lake's ecosystem Productivity, as inferred from fossil pigment analysis, tended to increase over the postglacial, and there is no evidence for a prolonged period of trophic equilibrium Maximum production rates were correlated with efficient phosphorus diagenesis The lake evidently became meromictic around 900 BP (before present) and this was associated with a sulphide producing monimolimnion and decreased productivity Cultural practices in the watershed around 140 BP increased inorganic sedimentation and further reduced productivity

The Photosynthetic Capacity of the Phytoplankton in the Waters of a Coral Reef

Abstract: Phytoplankton are relatively scarce in surface waters in a region of the Great Barrier Reef near Lizard Island. The phytoplankton sampled have a high rate of photosynthetic efficiency (1.2 millimoles CO2 fixed per milligram chlorophyll a per hour), although between 30 and 50% of the total carbon fixed may be excreted in soluble form. The rate of photosynthetic CO2 fixation into the particulate fraction is sensitive to varying levels of oxygen, suggesting the existence of a photorespiratory mechanism, a factor which might significantly influence the photosynthetic productivity of the algae in these tropical waters.

Biological productivity of hybrids and strains of yeast cultures of different ploidy

Abstract: Ploidy and productivity of yeast strains and hybrids obtained by crossing various industrial races were studied. Biological productivity of yeast cultures increases with ploidy as was found by comparing biological productivity (biomass accumulation) in haploids, diploids, triploids, and tetraploids. Possible factors causing an insignificant decrease in productivity of some tetraploids as compared to triploids are discussed.

The Ecology of Honey Creek: Temporal Patterns of the Travertine Periphyton and Selected Physio-Chemical Parameters, and Myriophyllum Community Productivity

Abstract: Quantitative estimates of periphyton seasonal and spatial changes were made at nine stations in an Arbuckle Mountain limestone stream using a colorimetric method. Periphyton was most abundant at the unshaded, upstream stations and had autumnal and vernal blooms. Temporal changes in the periphyton were related to day length, temperature, rainfall, discharge, alkalinity, and pH. Myriophyllum community primary productivity, estimated by the diel oxygen curve method, was low, 1.96, 2.14, and 2.22 g/m /day, and productivity/ respiration ratios were consistently less than 1.

Biological and Chemical Evaluation of the Aquatic Environment of Selected Undeveloped Kentucky Lake Embayments

Abstract: This report describes research involving biological and chemical analysis of two undeveloped embayments on Kentucky Lake, namely Anderson and Vickers Bays. Field and laboratory studies were made to assess current biotic standing crops, limnological conditions, levels of inorganic and organic pollutants in the embayments.