scholarly journals Catchment land use predicts benthic vegetation in small estuaries

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4378
Author(s):  
Perran L.M. Cook ◽  
Fiona Y. Warry ◽  
Paul Reich ◽  
Ralph Mac Nally ◽  
Ryan J. Woodland
Keyword(s):  
Land Use ◽  
Human Activities ◽  
Inorganic Nitrogen ◽  
Area Ratio ◽  
Nutrient Loads ◽  
Dissolved Inorganic Nitrogen ◽  
Flushing Time ◽  
Nitrogen Loads ◽  
Eastern Australia ◽  
Benthic Vegetation

Many estuaries are becoming increasingly eutrophic from human activities within their catchments. Nutrient loads often are used to assess risk of eutrophication to estuaries, but such data are expensive and time consuming to obtain. We compared the percent of fertilized land within a catchment, dissolved inorganic nitrogen loads, catchment to estuary area ratio and flushing time as predictors of the proportion of macroalgae to total vegetation within 14 estuaries in south-eastern Australia. The percent of fertilized land within the catchment was the best predictor of the proportion of macroalgae within the estuaries studied. There was a transition to a dominance of macroalgae once the proportion of fertilized land in the catchment exceeded 24%, highlighting the sensitivity of estuaries to catchment land use.

scholarly journals Flood water quality and marine sediment and nutrient loads from the Tully and Murray catchments in north Queensland, Australia

2009 ◽  
Vol 60 (11) ◽  
pp. 1123 ◽  
Author(s):  
Jim Wallace ◽  
Lachlan Stewart ◽  
Aaron Hawdon ◽  
Rex Keen ◽  
Fazlul Karim ◽  
...  
Keyword(s):  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
Inorganic Nitrogen ◽  
Nutrient Concentrations ◽  
Large Contribution ◽  
Nutrient Loads ◽  
Nitrogen And Phosphorus ◽  
Annual Average ◽  
Nitrogen Loads ◽  
Flood Flows

Current estimates of sediment and nutrient loads from the Tully–Murray floodplain to the Great Barrier Reef lagoon are updated by taking explicit account of flood events. New estimates of flood discharge that include over-bank flows are combined with direct measurements of sediment and nutrient concentrations in flood waters to calculate the loads of sediment and nutrient delivered to the ocean during 13 floods that occurred between 2006 and 2008. Although absolute concentrations of sediment and nutrient were quite low, the large volume of water discharged during floods means that they make a large contribution (30–50%) to the marine load. By not accounting for flood flows correctly, previous estimates of the annual average discharge are 15% too low and annual loads of nitrogen and phosphorus are 47% and 32% too low respectively. However, because sediments may be source-limited, accounting for flood flows simply dilutes their concentration and the resulting annual average load is similar to that previously estimated. Flood waters also carry more dissolved organic nitrogen than dissolved inorganic nitrogen and this is the opposite of their concentrations in river water. Consequently, dissolved organic nitrogen loads to the ocean may be around twice those previously estimated from riverine data.

Quantifying potential nitrogen removal by denitrification in stream sediments at a regional scale

2004 ◽  
Vol 55 (3) ◽  
pp. 309 ◽  
Author(s):  
M. E. Bartkow ◽  
J. W. Udy
Keyword(s):  
Nitrogen Limitation ◽  
Inorganic Nitrogen ◽  
Regional Scale ◽  
Stream Sediments ◽  
Important Process ◽  
Dissolved Inorganic Nitrogen ◽  
Block Method ◽  
Streams And Rivers ◽  
Nitrogen Loads ◽  
Low Concentrations

Potential denitrification rates were measured using the acetylene block method, in sediments collected from streams in the sub-tropical, south-east Queensland region of Australia. Our aim was to estimate how much nitrogen could be removed from lotic systems by denitrification at the regional scale. Denitrification measured at 65 sites in August and September from a catchment of 22700 km2 was extrapolated to all streams and rivers in the region based on the sediment area available for denitrification. Denitrification rates ranged between 4 and 950 μmol N m–2 h–1, with most sites having rates below 150 μmol N m–2 h–1. Based on these results, the current study estimates that a total of 305 t of nitrogen could be denitrified per year from all streams and rivers in the region, representing 6% of the total annual nitrogen load from surrounding land use. During baseflow conditions, when nitrogen loads to streams are low, the proportion of nitrogen removed through denitrification would be substantially higher, in some cases removing 100% of the nitrogen load. It is proposed that denitrification is an important process maintaining low concentrations of dissolved inorganic nitrogen under baseflow conditions and is therefore likely to enhance nitrogen limitation of primary production in this region.

scholarly journals Seasonal dissolved inorganic nitrogen and phosphorus budgets for two sub-tropical estuaries in south Florida, USA

2013 ◽  
Vol 10 (2) ◽  
pp. 2377-2413
Author(s):  
C. Buzzelli ◽  
Y. Wan ◽  
P. H. Doering ◽  
J. N. Boyer
Keyword(s):  
Nutrient Loading ◽  
Inorganic Nitrogen ◽  
River Estuary ◽  
South Florida ◽  
Biogeochemical Model ◽  
Dissolved Inorganic Nitrogen ◽  
Nitrogen And Phosphorus ◽  
Tropical Estuaries ◽  
Flushing Time ◽  
Management Actions

Abstract. Interactions among watershed nutrient loading, circulation, and biogeochemical cycling determine the capacity of estuaries to accommodate introduced nutrients. Baseline quantification of loading, flushing time, export, and internal processes is essential to understand responses of sub-tropical estuaries to variable climate and nutrient loading. The goal of this study was to develop seasonal dissolved inorganic nitrogen (DIN) and phosphorus (DIP) budgets for the two estuaries in south Florida, the Caloosahatchee River Estuary (CRE) and the St. Lucie Estuary (SLE), from 2002–2008 spanning various climatic conditions. The Land Ocean Interactions in the Coastal Zone (LOICZ) Biogeochemical Model was used to generate water, salt, and (DIN and DIP) budgets. The predicted increase in internal DIN production for the CRE vs. the SLE was associated with increased external DIN loading. Water column DIN concentrations decreased and stabilized in both estuaries as flushing time increased to > 10 d. The CRE demonstrated heterotrophy or balanced metabolism across all seasonal budgets. Although the SLE was also sensitive to DIN loading, system autotrophy and net ecosystem metabolism increased with DIP loading to this estuary. This included a huge DIP consumption and bloom of a cyanobacterium (Microcystis aeruginosa) following hurricane-induced discharge in 2005. Additionally, while denitrification offered a loss pathway for inorganic nitrogen in the CRE, this potential was not evident for the smaller and more anthropogenically altered St. Lucie Estuary. Disparities between total and inorganic loading ratios suggested that management actions should examine the role of dissolved organic nitrogen (DON) in attempts to reduce both nitrogen and phosphorus inputs to the SLE. Establishment of quantitative loading limits for anthropogenically impacted estuaries requires an understanding of the inter-seasonal and inter-annual relationships for both N and P, circulation and flushing, variability in plankton community composition, and the dynamics of DON.

scholarly journals Nitrogen and Phosphorus Loads in Greek Rivers: Implications for Management in Compliance with the Water Framework Directive

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1531
Author(s):  
Konstantinos Stefanidis ◽  
Aikaterini Christopoulou ◽  
Serafeim Poulos ◽  
Emmanouil Dassenakis ◽  
Elias Dimitriou
Keyword(s):  
Water Framework Directive ◽  
Inorganic Nitrogen ◽  
Inorganic Phosphorus ◽  
Point Sources ◽  
Nutrient Concentrations ◽  
Nutrient Loads ◽  
Land Uses ◽  
Nitrogen And Phosphorus ◽  
Nitrogen Loads ◽  
Phosphorus Loads

Reduction of nutrient loadings is often prioritized among other management measures for improving the water quality of freshwaters within the catchment. However, urban point sources and agriculture still thrive as the main drivers of nitrogen and phosphorus pollution in European rivers. With this article we present a nationwide assessment of nitrogen and phosphorus loads that 18 large rivers in Greece receive with the purpose to assess variability among seasons, catchments, and river types and distinguish relationships between loads and land uses of the catchment. We employed an extensive dataset of 636 field measurements of nutrient concentrations and river discharges to calculate nitrogen and phosphorus loads. Descriptive statistics and a cluster analysis were conducted to identify commonalties and differences among catchments and seasons. In addition a network analysis was conducted and its modularity feature was used to detect commonalities among rivers and sampling sites with regard to their nutrient loads. A correlation analysis was used to identify major possible connections between types of land uses and nutrient loads. The results indicated that the rivers Alfeios, Strymonas, and Aliakmonas receive the highest inorganic nitrogen loads while the highest inorganic phosphorus loads were calculated for the rivers Strymonas, Aliakmonas, and Axios. Concerning the temporal variation of loads, inorganic nitrogen presented a peak on March and gradually declined until October when the dry period typically ends for most regions of Greece. Inorganic phosphorus loads had the highest average value in August and the lowest in October. Thus, our findings confirmed the presence of a typical seasonal variation in nitrogen loads that follows the seasonality in hydrology where high surface runoff during the wet months contribute to higher river discharges and higher nitrogen loads from the catchment. On the contrary, high phosphorus loads persisted during dry months that could be attributed to a dilution effect. Furthermore, the results imply a clear connection between agriculture and both nitrogen and phosphorus. Overall, this work presents extensive information on the nitrogen and phosphorus loads that major rivers in Greece receive that can largely aid water managers to adapt and revise basin management plans in accordance with agricultural management (e.g., which months farmers should reduce the use of fertilizers) with the purpose of meeting the environmental targets defined by the Water Framework Directive (WFD).

scholarly journals Changes of the nutrient loads of the Odra River during the last century - their causes and consequences

2008 ◽  
Vol 12 (1) ◽  
pp. 127-144 ◽  
Author(s):  
Horst Behrendt ◽  
Dieter Opitz ◽  
Agnieszka Kolanek ◽  
Rafalina Korol ◽  
Marzenna Strońska
Keyword(s):  
Point Source ◽  
Total Phosphorus ◽  
Inorganic Nitrogen ◽  
Nutrient Loads ◽  
Dissolved Inorganic Nitrogen ◽  
Total N ◽  
Odra River ◽  
Time Periods ◽  
Total P ◽  
Point Source Discharges

Changes of the nutrient loads of the Odra River during the last century - their causes and consequencesNutrient emissions by point and diffuse sources and their loads were estimated for the Odra catchment over the time period of the last 50 years by means of the model MONERIS. For nitrogen a change of the total emissions from 38 kt·a−1N in the mid of 1950s a maximum of 105 kt·a−1N in the early 1980s and a recent value of about 84 kt·a−1N were estimated for the total Odra Basin. The share of the point source discharges on the total N emissions varied between 24% (1955) and 35% (1995). The emissions from groundwater and tile drained areas represent the dominant pathway (37-56% of total N emissions) during all investigated time periods. Emissions from tile drained areas increased from the mid of 1950s to end of 1980s by a factor of 20 and reached in this period the same amount as emissions by groundwater. For phosphorus the emissions changed from 4 kt·a−1P in 1955 to 14 kt·a−1P in 1990 and a recent level of 7 kt·a−1P. Point source discharges caused between 36 to 66% of total P emissions and represent the dominant pathway for all investigated time periods. Erosion and discharges from paved urban areas and sewer systems was the dominant diffuse pathway of the total P emissions into the river system. The comparison of calculated and observed nutrient loads for the main monitoring stations along the Odra River shows that the average deviation is 12% for total phosphorus (1980-2000) and 15% for dissolved inorganic nitrogen (1960-2000). From the analysis it can be concluded that the present load of dissolved inorganic nitrogen (DIN) and total nitrogen (TN) of the Odra into the Baltic Sea is about 2.3 times higher than in the mid of 1960s. The maximum DIN load (1980s) was more than 3 times higher than in the 1960s. The change of the total phosphorus (TP) load is characterized by an increase from the 1955s to 1980 from 2 to 7 kt·a−1P (factor 2.6). Around 2000 the TP load was 4 kt·a−1which is only the double of the level of the 1955s.

scholarly journals A framework to quantify riverine dissolved inorganic nitrogen exports under changing land use pattern and hydrologic regime

2020 ◽  
Author(s):  
Zhenyu Zhang ◽  
Jr-Chuan Huang ◽  
Jinliang Huang
Keyword(s):  
Land Use ◽  
Inorganic Nitrogen ◽  
Land Use Changes ◽  
Interactive Effects ◽  
Dominant Factor ◽  
Dissolved Inorganic Nitrogen ◽  
Land Use Patterns ◽  
Land Use Pattern ◽  
Window Method ◽  
N Management

Riverine dissolved inorganic nitrogen (DIN), when elevated by human activities (e.g., land-use change), can accelerate the nitrogen cycle and downstream dispersal. However, estimating DIN export coefficients for individual land-use types can be complex due to mosaic land-use patterns and interactions between fertilizers and hydrological processes. We propose a framework that integrates an empirical model, a moving-window method with an elasticity method to quantify seasonal DIN export coefficients for each land use in the Shixi Creek catchment, southeast China. Our model showed good agreement with field observations according to root mean square error and a normalized objective function. The DIN export coefficients of farmland and forest were the highest (9.16 mg/L) and lowest (2.91 mg/L), respectively, resulting in DIN exports for farmland and forest of 1,951 kg km-2 yr-1 and 619 kg km-2 yr-1, respectively. Urbanization was a dominant factor influencing DIN export represented by the export coefficient of built-up areas with the highest elasticity and highest uncertainty. This study can shed light on how to improve riverine N management in a catchment by considering the interactive effects of climate and land use changes.

scholarly journals Inverse isolation of dissolved inorganic nitrogen yield for individual land-uses from mosaic land-use patterns within a watershed

2015 ◽  
Vol 12 (1) ◽  
pp. 449-487 ◽  
Author(s):  
Y.-T. Shih ◽  
T.-Y. Lee ◽  
J.-C. Huang ◽  
S.-J. Kao ◽  
K.-K. Liu ◽  
...  
Keyword(s):  
Land Use ◽  
Inorganic Nitrogen ◽  
Fertilizer Application ◽  
Annual Runoff ◽  
Dissolved Inorganic Nitrogen ◽  
Land Use Patterns ◽  
Strong Basis ◽  
Use Patterns ◽  
Per Capita ◽  
The Given

Abstract. This study combines the observed riverine DIN (dissolved inorganic nitrogen) export and the controlling factors (land-use, population and discharge) to inversely estimate the effective DIN yield factors for individual land-use and DIN per capita loading. A total of 16 sub-catchments, with different land-use compositions on the Danshui River of Taiwan, were used in this study. Observed riverine DIN concentrations and yields varied from 20–450 μM and 400–10 000 kg N km−2 yr−1 corresponding to the increase of urbanization gradient (e.g. building and population). Meanwhile, the transport behaviors changed from hydrological enhancement to dilution with increasing urbanization as well. Our method shows that the DIN yield factors, independent of discharge, are 12.7, 63.9, and 1381.0 μM, for forest, agriculture, and building, respectively, which equals to 444.5, 2236.5, 48 335 kg N km−2 yr−1 at the given annual runoff of 2500 mm. The agriculture DIN yield only accounts for 10% of fertilizer application indicating the complicated N cascade and possible over fertilization. The DIN per capita loading (~0.49 kg N capita−1 yr−1) which is lower than the documented human N emission (1.6–5.5 kg N capita−1 yr−1) can be regarded as an effective export coefficient after treatment or retention. A conducted scenario experiment supports the observations demonstrating the capability for assessment. We therefore, can extrapolate all possible combinations of land-use, discharge, and population density for evaluation. This can provide a strong basis for watershed management and supplementary estimation for regional to global study.

Relationships Between Soluble and Sediment Nutrient Losses, Land Use and Types of Soil in Agricultural Watersheds

1977 ◽  
Vol 12 (1) ◽  
pp. 121-134 ◽  
Author(s):  
G.H. Neilsen ◽  
A.F. Mackenzie
Keyword(s):  
Land Use ◽  
Inorganic Nitrogen ◽  
High Surface ◽  
Sediment Concentration ◽  
Chemical Oxidation ◽  
Nutrient Loss ◽  
Potassium Sulfate ◽  
Agricultural Watersheds ◽  
Nutrient Losses ◽  
Calcium Magnesium

Abstract Seven agricultural watersheds in southwestern Quebec and southeastern Ontario, ranging in area from 2,000 to 20,000 hectares, were monitored systematically during 1973–75 for soluble inorganic nitrogen, total soluble phosphorus, calcium, magnesium, potassium, sulfate-sulfur, chemical oxidation demand, discharge, suspended sediment concentration, sediment Kjeldahl nitrogen, Bray extractable phosphorus, and ammonium acetate extractable calcium, magnesium and potassium. For 1974–75, annual Kg/ha, loss rates were calculated for the soluble and sediment associated nutrients. Losses varied with nutrient and watershed, with volume of runoff being an important control of nutrient loss variation. Significant amounts of SO4−S in precipitation were suggested by an average watershed soluble N:P:S loss ratio of 10:1:92. Sediment nutrient losses were especially important for N and P, comprising over 40% of their total loss. The importance of spring snow-melt runoff was demonstrated by the high proportion of all nutrients lost at this time. Correlations of nutrient loss, land use and soils suggested that certain land uses resulted in increased stream nutrient losses while increased watershed area of soils with a high surface runoff potential was particularly conducive to increased soluble nutrient and sediment losses.

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