An analysis of primary production in the Daly River, a relatively unimpacted tropical river in northern Australia

2005 ◽  
Vol 56 (3) ◽  
pp. 303 ◽  
Author(s):  
I. T. Webster ◽  
N. Rea ◽  
A. V. Padovan ◽  
P. Dostine ◽  
S. A. Townsend ◽  
...  
Keyword(s):  
Primary Production ◽  
Plant Biomass ◽  
Net Primary Production ◽  
Low Flow ◽  
Nutrient Concentrations ◽  
Tight Coupling ◽  
Tropical River ◽  
Rate Of Photosynthesis ◽  
Curve Method ◽  
Tropical Australia

In this paper, the dynamics of primary production in the Daly River in tropical Australia are investigated. We used the diurnal-curve method for both oxygen and pH to calculate photosynthesis and respiration rates as indicators of whole-river productivity. The Daly River has maximum discharges during the summer, monsoonal season. Flow during the dry season is maintained by groundwater discharge via springs. The study investigated how primary production and respiration evolve during the period of low flow in the river (April–November). The relationship between primary production and the availability of light and nutrients enabled the role of these factors to be assessed in a clear, oligotrophic tropical river. The measured rate of photosynthesis was broadly consistent with the estimated mass of chlorophyll associated with the main primary producers in the river (phytoplankton, epibenthic algae, macroalgae, macrophytes). A significant result of the analysis is that during the time that plant biomass re-established after recession of the flows, net primary production proved to be ~4% of the rate of photosynthesis. This result and the observed low-nutrient concentrations in the river suggest a tight coupling between photosynthetic fixation of carbon and the microbial degradation of photosynthetic products comprising plant material and exudates.

Biomass, nutrient distribution, and net production in alpine communities of the Kluane Mountains, Yukon Territory, Canada

1981 ◽  
Vol 59 (12) ◽  
pp. 2635-2649 ◽  
Author(s):  
Charles C. Grier ◽  
T. M. Ballard
Keyword(s):  
Organic Matter ◽  
Primary Production ◽  
Net Primary Production ◽  
Yukon Territory ◽  
Nutrient Concentrations ◽  
Aboveground Net Primary Production ◽  
Matter Distribution ◽  
Nutrient Distribution ◽  
Alpine Zone ◽  
Temperature Regimes

Biomass and nutrient distribution and aboveground net primary production were determined for two communities growing at 1600 m elevation and five communities growing at about 2000 m elevation in the alpine zone of the Kluane Ranges, Yukon Territory, Canada. Living biomass accumulations ranged from 183 to 1350 g/m2, whereas total organic matter accumulations ranged from 2126 to 51120 g/m2. Nutrient distribution in general reflected organic matter distribution. Highest nutrient concentrations were in leaves and fine roots. Aboveground net primary production ranged from 18.3 to 185.5 g/m2. Primary production appeared to be related most to moisture during the growing season and temperature regimes.

scholarly journals Diatoms Si Uptake Capacity Drives Carbon Export In Coastal Upwelling Systems

2016 ◽  
Author(s):  
F. Abrantes ◽  
P. Cermeño ◽  
C. Lopes ◽  
O. Romero ◽  
L. Matos ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Coastal Upwelling ◽  
Net Primary Production ◽  
Regional Scale ◽  
Global Scale ◽  
Global Ocean ◽  
Nutrient Concentrations ◽  
Organic Carbon Content ◽  
Organic Carbon Burial

Abstract. Coastal upwelling systems account for approximately half of global ocean primary production and contribute disproportionately to biologically driven carbon sequestration. Diatoms, silica–precipitating microalgae, constitute the dominant phytoplankton in these productive regions, and their abundance and assemblage composition in the sedimentary record is considered one of the best proxies for primary production. The study of the sedimentary diatom abundance (SDA) and total organic carbon content (TOC) in the five most important coastal upwelling systems of the modern ocean (Iberia-Canary, Benguela, Peru-Humboldt, California and Somalia-Oman) reveals a global-scale positive relationship between diatom production and organic carbon burial. The analysis of SDA in conjunction with environmental variables of coastal upwelling systems such as upwelling strength, satellite-derived net primary production and surface water nutrient concentrations shows different relations between SDA and primary production on the regional scale. At the global-scale, SDA appears modulated by the capacity of diatoms to take up silicic acid, which ultimately sets an upper limit to global export production in these ocean regions.

scholarly journals Assessing vegetation structure and ANPP dynamics in a grassland-shrubland Chihuahuan ecotone using NDVI-rainfall relationships

2015 ◽  
Vol 12 (1) ◽  
pp. 51-92 ◽  
Author(s):  
M. Moreno-de las Heras ◽  
R. Diaz-Sierra ◽  
L. Turnbull ◽  
J. Wainwright
Keyword(s):  
Primary Production ◽  
Vegetation Change ◽  
Chihuahuan Desert ◽  
Plant Biomass ◽  
Net Primary Production ◽  
Larrea Tridentata ◽  
Shrub Encroachment ◽  
Grass Species ◽  
Natural Habitats ◽  
Herbaceous Vegetation

Abstract. Climate change and the widespread alteration of natural habitats are major drivers of vegetation change in drylands. A classic case of vegetation change is the shrub-encroachment process that has been taking place over the last 150 years in the Chihuahuan Desert, where large areas of grasslands dominated by perennial grass species (black grama, Bouteloua eriopoda, and blue grama, B. gracilis) have transitioned to shrublands dominated by woody species (creosotebush, Larrea tridentata, and mesquite, Prosopis glandulosa), accompanied by accelerated water and wind erosion. Multiple mechanisms drive the shrub-encroachment process, including exogenous triggering factors such as precipitation variations and land-use change, and endogenous amplifying mechanisms brought about by soil erosion-vegetation feedbacks. In this study, simulations of plant biomass dynamics with a simple modelling framework indicate that herbaceous (grasses and forbs) and shrub vegetation in drylands have different responses to antecedent precipitation due to functional differences in plant growth and water-use patterns, and therefore shrub encroachment may be reflected in the analysis of landscape-scale vegetation–rainfall relationships. We analyze the structure and dynamics of vegetation at an 18 km2 grassland-shrubland ecotone in the northern edge of the Chihuahuan Desert (McKenzie Flats, Sevilleta National Wildlife Refuge, NM, USA) by investigating the relationship between decade-scale (2000–2013) records of medium-resolution remote sensing of vegetation greenness (MODIS NDVI) and precipitation. Spatial evaluation of NDVI-rainfall relationship at the studied ecotone indicates that herbaceous vegetation shows quick growth pulses associated with short-term (previous 2 months) precipitation, while shrubs show a slow response to medium-term (previous 5 months) precipitation. We use these relationships to (a) classify landscape types as a function of the spatial distribution of dominant vegetation, and to (b) decompose the NDVI signal into partial primary production components for herbaceous vegetation and shrubs across the study site. We further apply remote-sensed annual net primary production (ANPP) estimations and landscape type classification to explore the influence of inter-annual variations in seasonal precipitation on the production of herbaceous and shrub vegetation. Our results suggest that changes in the amount and temporal pattern of precipitation comprising reductions in monsoonal summer rainfall and/or increases in winter precipitation may enhance the shrub-encroachment process in desert grasslands of the American Southwest.

Phytoplankton composition and constraints to biomass in the middle reaches of an Australian tropical river during base flow

2012 ◽  
Vol 63 (1) ◽  
pp. 48 ◽  
Author(s):  
S. A. Townsend ◽  
M. Przybylska ◽  
M. Miloshis
Keyword(s):  
Rapid Growth ◽  
Phytoplankton Biomass ◽  
Dry Season ◽  
Base Flow ◽  
Nutrient Concentrations ◽  
Phytoplankton Composition ◽  
Tropical River ◽  
Transport Time ◽  
Tropical Australia ◽  
High Flows

Under high flows, the biomass of riverine phytoplankton can be constrained by short transport times and advective losses. However, under slower flows and longer transport times, secondary factors and sometimes their interaction with flow may constrain phytoplankton biomass. To contribute to a wider understanding of the riverine conditions that constrain phytoplankton biomass, we tested the hypothesis that phytoplankton of the Daly River (tropical Australia) was constrained by transport time during dry-season base flow. The river is virtually undisturbed, with oligotrophic nutrient concentrations during the dry season. The most frequently occurring taxa were planktonic, rather than benthic, and dominated by the dinoflagellate Peridinium inconspicuum which has r-strategist traits that favour rapid growth in a nutrient-deficient environment. Our hypothesis was not supported because increased downstream loads of Chlorophyll a and the domination of P. inconspicuum inferred phytoplankton net growth. Instead, phytoplankton biomass was more likely to be nutrient-limited, although transport time may limit phytoplankton growth over some reaches and for specific taxa. The present study demonstrated that even in the fast-flowing middle reaches of a river (~0.4 m s–1), a population of phytoplankton can be sustained.

scholarly journals Diatoms Si uptake capacity drives carbon export in coastal upwelling systems

2016 ◽  
Vol 13 (14) ◽  
pp. 4099-4109 ◽  
Author(s):  
Fatima Abrantes ◽  
Pedro Cermeno ◽  
Cristina Lopes ◽  
Oscar Romero ◽  
Lélia Matos ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Primary Production ◽  
Coastal Upwelling ◽  
Net Primary Production ◽  
Regional Scale ◽  
Global Scale ◽  
Global Ocean ◽  
Nutrient Concentrations ◽  
Organic Carbon Content ◽  
Organic Carbon Burial

Abstract. Coastal upwelling systems account for approximately half of global ocean primary production and contribute disproportionately to biologically driven carbon sequestration. Diatoms, silica-precipitating microalgae, constitute the dominant phytoplankton in these productive regions, and their abundance and assemblage composition in the sedimentary record is considered one of the best proxies for primary production. The study of the sedimentary diatom abundance (SDA) and total organic carbon content (TOC) in the five most important coastal upwelling systems of the modern ocean (Iberia–Canary, Benguela, Peru–Humboldt, California, and Somalia–Oman) reveals a global-scale positive relationship between diatom production and organic carbon burial. The analysis of SDA in conjunction with environmental variables of coastal upwelling systems such as upwelling strength, satellite-derived net primary production, and surface water nutrient concentrations shows different relations between SDA and primary production on the regional scale. On the global scale, SDA appears modulated by the capacity of diatoms to take up silicic acid, which ultimately sets an upper limit to global export production in these ocean regions.

scholarly journals Catastrophic shifts in the aquatic primary production revealed by a small low-flow section of tropical downstream after dredging

2015 ◽  
Vol 75 (4) ◽  
pp. 804-811
Author(s):  
H. Marotta ◽  
A. Enrich-Prast
Keyword(s):  
Primary Production ◽  
Aquatic Macrophytes ◽  
Net Primary Production ◽  
Gross Primary Production ◽  
Light Attenuation ◽  
Low Flow ◽  
Flow Section ◽  
Net Heterotrophy ◽  
The Tropics ◽  
Catastrophic Shifts

Abstract Dredging is a catastrophic disturbance that directly affects key biological processes in aquatic ecosystems, especially in those small and shallow. In the tropics, metabolic responses could still be enhanced by the high temperatures and solar incidence. Here, we assessed changes in the aquatic primary production along a small section of low-flow tropical downstream (Imboassica Stream, Brazil) after dredging. Our results suggested that these ecosystems may show catastrophic shifts between net heterotrophy and autotrophy in waters based on three short-term stages following the dredging: (I) a strongly heterotrophic net primary production -NPP- coupled to an intense respiration -R- likely supported by high resuspended organic sediments and nutrients from the bottom; (II) a strongly autotrophic NPP coupled to an intense gross primary production -GPP- favored by the high nutrient levels and low solar light attenuation from suspended solids or aquatic macrophytes; and (III) a NPP near to the equilibrium coupled to low GPP and R rates following, respectively, the shading by aquatic macrophytes and high particulate sedimentation. In conclusion, changes in aquatic primary production could be an important threshold for controlling drastic shifts in the organic matter cycling and the subsequent silting up of small tropical streams after dredging events.

scholarly journals Climate change impacts on net primary production (NPP) and export production (EP) regulated by increasing stratification and phytoplankton community structure in the CMIP5 models

2016 ◽  
Vol 13 (18) ◽  
pp. 5151-5170 ◽  
Author(s):  
Weiwei Fu ◽  
James T. Randerson ◽  
J. Keith Moore
Keyword(s):  
Climate Change ◽  
Community Structure ◽  
Primary Production ◽  
Phytoplankton Community ◽  
Net Primary Production ◽  
Climate Change Impacts ◽  
Cmip5 Models ◽  
Nutrient Concentrations ◽  
Phytoplankton Community Structure ◽  
Export Production

Abstract. We examine climate change impacts on net primary production (NPP) and export production (sinking particulate flux; EP) with simulations from nine Earth system models (ESMs) performed in the framework of the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Global NPP and EP are reduced by the end of the century for the intense warming scenario of Representative Concentration Pathway (RCP) 8.5. Relative to the 1990s, NPP in the 2090s is reduced by 2–16 % and EP by 7–18 %. The models with the largest increases in stratification (and largest relative declines in NPP and EP) also show the largest positive biases in stratification for the contemporary period, suggesting overestimation of climate change impacts on NPP and EP. All of the CMIP5 models show an increase in stratification in response to surface–ocean warming and freshening, which is accompanied by decreases in surface nutrients, NPP and EP. There is considerable variability across the models in the magnitudes of NPP, EP, surface nutrient concentrations and their perturbations by climate change. The negative response of NPP and EP to increasing stratification reflects primarily a bottom-up control, as upward nutrient flux declines at the global scale. Models with dynamic phytoplankton community structure show larger declines in EP than in NPP. This pattern is driven by phytoplankton community composition shifts, with reductions in productivity by large phytoplankton as smaller phytoplankton (which export less efficiently) are favored under the increasing nutrient stress. Thus, the projections of the NPP response to climate change are critically dependent on the simulated phytoplankton community structure, the efficiency of the biological pump and the resulting levels of regenerated production, which vary widely across the models. Community structure is represented simply in the CMIP5 models, and should be expanded to better capture the spatial patterns and climate-driven changes in export efficiency.

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