scholarly journals River regulation alters drivers of primary productivity along a tropical river-estuary system

2011 ◽  
Vol 62 (2) ◽  
pp. 141 ◽  
Author(s):  
M. A. Burford ◽  
A. T. Revill ◽  
D. W. Palmer ◽  
L. Clementson ◽  
B. J. Robson ◽  
...  
Keyword(s):  
Primary Production ◽  
Primary Productivity ◽  
Light Attenuation ◽  
River Estuary ◽  
River Regulation ◽  
Tropical River ◽  
Seasonal Flow ◽  
Freshwater Zone ◽  
High Concentrations ◽  
Downstream Flow

Worldwide, rivers continue to be dammed to supply water for humans. The resulting regulation of downstream flow impacts on biogeochemical and physical processes, potentially affecting river and estuarine productivity. Our study tested the hypothesis that primary production in the downstream freshwater reaches of a dammed river was less limited by light and nutrients relative to downstream estuarine primary production. In a tropical dryland Australian river estuary, we found that water-column primary productivity was highest at freshwater sites that had lowest light attenuation. Nitrogen may also have limited primary productivity. Below the freshwater zone was a region of macrotidal mixing with high concentrations of suspended soil particles, nutrients and chlorophyll a, and lower but variable primary productivity rates. Light controlled productivity, but the algal cells may also have been osmotically stressed due to increasing salinity. Further downstream in the estuary, primary productivity was lower than the freshwater reaches and light and nutrient availability appear to be a factor. Therefore the reduced magnitude of peak-flow events due to flow regulation, and the resulting decrease in nutrient export, is likely to be negatively impacting estuarine primary production. This has implications for future development of dams where rivers have highly seasonal flow.

Assessment of heavy metal pollution in surficial sediments from a tropical river-estuary-shelf system: A case study of Kelantan River, Malaysia

2017 ◽  
Vol 125 (1-2) ◽  
pp. 492-500 ◽  
Author(s):  
Ai-jun Wang ◽  
Chui Wei Bong ◽  
Yong-hang Xu ◽  
Meor Hakif Amir Hassan ◽  
Xiang Ye ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Metal Pollution ◽  
Heavy Metal Pollution ◽  
River Estuary ◽  
Surficial Sediments ◽  
Tropical River ◽  
System A

Quantum yield of the marine benthic microflora of near-shore coastal Penang, Malaysia

2005 ◽  
Vol 56 (7) ◽  
pp. 1047 ◽  
Author(s):  
A. McMinn ◽  
S. Sellah ◽  
W. A. Wan Ab. Llah ◽  
M. Mohammad ◽  
F. Md. Sidik Merican ◽  
...  
Keyword(s):  
Primary Production ◽  
Suspended Solids ◽  
Euphotic Zone ◽  
Water Clarity ◽  
Quantum Yields ◽  
Chl A ◽  
Near Shore ◽  
High Concentrations ◽  
A Minor ◽  
Reduced Water

Benthic microalgal communities often contribute more than 30% of the primary production of shallow coastal and estuarine areas. At Muka Head Penang (Pulau Pinang) and the Songsong Islands (Pulau Songsong), Kedah, Malaysia, high concentrations of suspended solids and phytoplankton biomass (10.6 mg Chl a m−3) has reduced water clarity such that the euphotic zone of these areas is less than 2 m and 3 m deep respectively. The benthic microalgal communities, which were composed of the diatom genera Cocconeis, Fragilaria, Paralia and Pleurosigma, had a low biomass, had low maximum quantum yields (0.325 ± 0.129), were poorly adapted to their light environment and were constantly light limited. These characteristics suggest that the benthic microalgal communities were likely to have made only a minor contribution to the total primary production of the area.

scholarly journals Primary production sensitivity to phytoplankton light attenuation parameter increases with transient forcing

2017 ◽  
Vol 14 (20) ◽  
pp. 4767-4780 ◽  
Author(s):  
Karin F. Kvale ◽  
Katrin J. Meissner
Keyword(s):  
Primary Production ◽  
Net Primary Production ◽  
Light Attenuation ◽  
Climate Scenario ◽  
Sensitivity Study ◽  
Climate Forcing ◽  
Deep Time ◽  
Underwater Light Field ◽  
Attenuation Parameter ◽  
Biogeochemical Models

Abstract. Treatment of the underwater light field in ocean biogeochemical models has been attracting increasing interest, with some models moving towards more complex parameterisations. We conduct a simple sensitivity study of a typical, highly simplified parameterisation. In our study, we vary the phytoplankton light attenuation parameter over a range constrained by data during both pre-industrial equilibrated and future climate scenario RCP8.5. In equilibrium, lower light attenuation parameters (weaker self-shading) shift net primary production (NPP) towards the high latitudes, while higher values of light attenuation (stronger shelf-shading) shift NPP towards the low latitudes. Climate forcing magnifies this relationship through changes in the distribution of nutrients both within and between ocean regions. Where and how NPP responds to climate forcing can determine the magnitude and sign of global NPP trends in this high CO2 future scenario. Ocean oxygen is particularly sensitive to parameter choice. Under higher CO2 concentrations, two simulations establish a strong biogeochemical feedback between the Southern Ocean and low-latitude Pacific that highlights the potential for regional teleconnection. Our simulations serve as a reminder that shifts in fundamental properties (e.g. light attenuation by phytoplankton) over deep time have the potential to alter global biogeochemistry.

scholarly journals Fish assemblage in a dammed tropical river: an analysis along the longitudinal and temporal gradients from river to reservoir

2010 ◽  
Vol 8 (3) ◽  
pp. 599-606 ◽  
Author(s):  
Bianca de Freitas Terra ◽  
Alex Braz Iacone dos Santos ◽  
Francisco Gerson Araújo
Keyword(s):  
Fish Assemblage ◽  
Transitional Zone ◽  
Assemblage Structure ◽  
Fish Assemblage Structure ◽  
Wet Season ◽  
Tropical River ◽  
Longitudinal Gradient ◽  
Species Overlap ◽  
Seasonal Flow ◽  
Paraíba Do Sul River

We analysed changes in the fish assemblage structure along a longitudinal gradient of the Paraíba do Sul River and Funil Reservoir. We tested the hypothesis that shifts from lotic to lentic environment affect the richness and structure of the assemblage which are modulated by seasonal rainfall changes. Standardised monthly samplings were carried out from October 2006 to September 2007 in four zones: 1) river upstream from the reservoir; 2) upper part of the reservoir; 3) lower part of the reservoir, and 4) river downstream from the reservoir. Fishes were caught using gillnets deployed for 15 hours. We collected a total of 4550 specimens, representing 35 species and 5 orders. The highest richness and diversity were recorded in zone 2, the transitional zone between river and reservoir. In this ecotone, lotic and lentic species overlap. Greater abundance and biomass was recorded in the river upstream from the reservoir (zone 1); however, there are no differences between the zones in the structure of assemblages during the wet season. During the dry season, the assemblage structure is more differentiated between zones, although no differences in abundance and biomass occur. The seasonal flow of the river is the major driving factor to influence the fish assemblage structure along the longitudinal gradient from the river to the reservoir.

scholarly journals Seabed Resuspension in the Chesapeake Bay: Implications for Biogeochemical Cycling and Hypoxia

2020 ◽  
Vol 44 (1) ◽  
pp. 103-122
Author(s):  
Julia M. Moriarty ◽  
Marjorie A. M. Friedrichs ◽  
Courtney K. Harris
Keyword(s):  
Organic Matter ◽  
Chesapeake Bay ◽  
Water Column ◽  
Primary Productivity ◽  
Environmental Changes ◽  
Light Attenuation ◽  
Sediment Resuspension ◽  
Nitrogen Dynamics ◽  
Biogeochemical Model ◽  
Order Of Magnitude

AbstractSediment processes, including resuspension and transport, affect water quality in estuaries by altering light attenuation, primary productivity, and organic matter remineralization, which then influence oxygen and nitrogen dynamics. The relative importance of these processes on oxygen and nitrogen dynamics varies in space and time due to multiple factors and is difficult to measure, however, motivating a modeling approach to quantify how sediment resuspension and transport affect estuarine biogeochemistry. Results from a coupled hydrodynamic–sediment transport–biogeochemical model of the Chesapeake Bay for the summers of 2002 and 2003 showed that resuspension increased light attenuation, especially in the northernmost portion of the Bay, shifting primary production downstream. Resuspension also increased remineralization in the central Bay, which experienced larger organic matter concentrations due to the downstream shift in primary productivity and estuarine circulation. As a result, oxygen decreased and ammonium increased throughout the Bay in the bottom portion of the water column, due to reduced photosynthesis in the northernmost portion of the Bay and increased remineralization in the central Bay. Averaged over the channel, resuspension decreased oxygen by ~ 25% and increased ammonium by ~ 50% for the bottom water column. Changes due to resuspension were of the same order of magnitude as, and generally exceeded, short-term variations within individual summers, as well as interannual variability between 2002 and 2003, which were wet and dry years, respectively. Our results quantify the degree to which sediment resuspension and transport affect biogeochemistry, and provide insight into how coastal systems may respond to management efforts and environmental changes.

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.

Nutrient and Energy Cycles in an Estuarine Oyster Area

1966 ◽  
Vol 23 (11) ◽  
pp. 1635-1652 ◽  
Author(s):  
Fukuzo Uyeno
Keyword(s):  
Primary Production ◽  
Prince Edward Island ◽  
River Estuary ◽  
Carbon Assimilation ◽  
Microbial Abundance ◽  
Bay Area

The nutrient circulation and microbial abundance of oyster-producing waters in the Malpeque Bay area, Prince Edward Island, were followed at two stations through an open season, and the efficiency of carbon assimilation and dissimilation was estimated. Part of the organic fall-out evidently entered the water again in the spring as nutrient salts, but a certain portion was not returned and this represented a net loss from the ecosystem. The nutrient circulation at a station located in a saltwater pond was more efficient than at a station located in a river estuary. In the pond, mineralization was 31% of primary production, largely by mud bacteria; in the estuary it was 17%, about equally by mud and water organisms.

Primary Productivity of Southern Indian Lake before, during, and after Impoundment and Churchill River Diversion

1984 ◽  
Vol 41 (4) ◽  
pp. 591-604 ◽  
Author(s):  
R. E. Hecky ◽  
S. J. Guildford
Keyword(s):  
Light Intensity ◽  
Primary Production ◽  
Water Column ◽  
Primary Productivity ◽  
Phosphorus Deficiency ◽  
Light Environment ◽  
Phytoplankton Production ◽  
Light Penetration ◽  
The Mean ◽  
Chlorophyll Concentrations

The primary productivity of seven regions of Southern Indian Lake and neighboring Wood Lake was measured during open-water seasons from 1974 to 1978. The lake had regional differences in chlorophyll concentrations and daily rates of integral primary production in 1974 and 1975 prior to impoundment of the lake. Regions receiving Churchill River flow tended to have higher chlorophyll concentrations and production rates than those regions marginal to the flow. Impoundment of the lake resulted in higher efficiencies of primary production in all regions, as indicated by higher light-saturated rates of carbon uptake per unit chlorophyll and by higher initial slopes of the hyperbolic light response relation of the phytoplankton. Many large basins of the lake had light penetration reduced by high concentrations of suspended sediment from eroding shorelines, while other areas had relatively unchanged light penetration. The increased efficiency of carbon fixation per unit chlorophyll resulted in higher rates of integral production in those regions where light penetration was not greatly affected. Daily rates of integral primary production in lake regions where light penetration had decreased markedly were not significantly different after impoundment because efficiencies of light utilization were higher. Comparison of the mean water column light intensities for those turbid regions with the values of Ik (light intensity at the onset of light saturation) for phytoplankton indicated that these turbid regions are now light deficient on average. Phosphorus deficiency, as indicated by alkaline phosphatase activity per unit ATP, which was present before impoundment, has been eliminated as the mean water column light intensity declined below 5 mEinsteins∙m−2∙min−1. The light environment of a new reservoir can be a significant determinant of integral production, and predicting the consequences of impoundment on phytoplankton production requires accurate prediction of the light environment.

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