scholarly journals Understanding the hydrological and physicochemical drivers of Phormidium proliferation in the Hutt and Waipoua Rivers

2021 ◽  
Author(s):  
◽  
Emily Martin
Keyword(s):  
Water Column ◽  
Inorganic Nitrogen ◽  
Fine Sediment ◽  
Sediment Deposition ◽  
Point Sources ◽  
Warning Signs ◽  
Nutrient Concentrations ◽  
Available Phosphorus ◽  
Growth Monitoring ◽  
Management Options

<p>The Hutt and Waipoua rivers are affected annually by proliferations of the potentially toxic benthic cyanobacteria - Phormidium. Ingestion of these mats has resulted in numerous dog deaths and is therefore a risk to human health. This has resulted in the establishment of warning signs at many recreational sites on these rivers during summer months. Recent research has concluded that river flow and water column nutrients are two of the primary factors regulating Phormidium growth. Proliferations tend to form in rivers where there is slightly elevated water column dissolved inorganic nitrogen, low dissolved reactive phosphorus, and during periods of stable flow. It has been hypothesised that fine sediment may provide a source of phosphorus for Phormidium. These mats ‘capture’ fine sediment suspended in the water column, which becomes incorporated into the mat matrices when motile Phormidium filaments move over the sediment. Diffusive boundary layers at the surface of the mats limit the flow of nutrients and gases between mat and bulk river water, creating conditions (for example, lower dissolved oxygen, elevated pH) conducive to the release of phosphorus from sediment.  The aim of this project was to identify why Phormidium proliferates in certain parts of the Hutt and Waipoua rivers, as well as investigate the relationship between fine sediment and mat growth. Monitoring of river data was carried out in the Hutt and Waipoua Rivers between November 2014 and May 2015. Over this period, physicochemical and hydrological data was monitored to identify the influencing factors of Phormidium abundance. During February 2015, sediment traps were deployed to determine the sedimentation rates in parallel to Phormidium cover at each site. The collected fine sediment was fractionated and analysed for biologically available phosphorus. Finally, a manipulative study using stream channel mesocosms was undertaken to provide causative evidence that fine sediment deposition influences Phormidium growth. In this three-week study, four mesocosms were deployed containing different fine sediment treatments. Biomass samples were collected at regular intervals to determine total photosynthetic biomass and Phormidium specifically.  Phormidium cover during 2014-15 was influenced by water column nitrate-nitrite nitrogen concentrations and sediment deposition. Phormidium cover was considerably lower compared to previous years, with a maximum cover of 20.7% occurring in the Hutt River during February 2015. Analysis of historical flow and nutrient data suggests that the annual variation in Phormidium proliferation over the summer months was site specific and not generally driven by flow or nutrient concentrations.  It is likely that fine sediment plays a role in providing Phormidium mats with phosphorus in the Hutt and Waipoua River. This is shown through phosphorus concentrations within Phormidium mat water, which were 200-fold higher than the bulk water column. Maximum values of sedimentation, 272.0 g/m²/day, and biologically available phosphorus (bound to sediment) 1.4 mg P g⁻¹, occurred at sites with the highest Phormidium cover, which further confirms this correlation. Furthermore, mesocosm experiments showed that Phormidium biomass increased significantly (p=0.015) with an increased amount of sediment. However, the maximum biomass of 64.75 mg/m² did not occur in the mesocosm channel with the most sediment added to it. This suggests that a deposition threshold exists due to the attenuation of light.  Findings from this research provide some insights in to management options which may help to mitigate Phormidium proliferations in the future. The data indicates that reducing sediment inputs, or resuspension of fine sediment during flood remediation works, would reduce Phormidium proliferations. Riparian planting as well as the collaboration with local councils is needed to help reduce diffuse and remaining point sources of sediment and river bed disturbance during flood protection activities. Using a combination of observational and experimental studies, this research has shown that multiple factors influence Phormidium proliferation, and has highlighted the key role that fine sediment plays. Suggestions for future studies include in-river experiments to further explore the role of fine sediment and the optimisation of mesocosms, which may also help to investigate finer scale data on causative factors such as sediment thresholds.</p>

scholarly journals Understanding the hydrological and physicochemical drivers of Phormidium proliferation in the Hutt and Waipoua Rivers

2021 ◽  
Author(s):  
◽  
Emily Martin
Keyword(s):  
Water Column ◽  
Inorganic Nitrogen ◽  
Fine Sediment ◽  
Sediment Deposition ◽  
Point Sources ◽  
Warning Signs ◽  
Nutrient Concentrations ◽  
Available Phosphorus ◽  
Growth Monitoring ◽  
Management Options

<p>The Hutt and Waipoua rivers are affected annually by proliferations of the potentially toxic benthic cyanobacteria - Phormidium. Ingestion of these mats has resulted in numerous dog deaths and is therefore a risk to human health. This has resulted in the establishment of warning signs at many recreational sites on these rivers during summer months. Recent research has concluded that river flow and water column nutrients are two of the primary factors regulating Phormidium growth. Proliferations tend to form in rivers where there is slightly elevated water column dissolved inorganic nitrogen, low dissolved reactive phosphorus, and during periods of stable flow. It has been hypothesised that fine sediment may provide a source of phosphorus for Phormidium. These mats ‘capture’ fine sediment suspended in the water column, which becomes incorporated into the mat matrices when motile Phormidium filaments move over the sediment. Diffusive boundary layers at the surface of the mats limit the flow of nutrients and gases between mat and bulk river water, creating conditions (for example, lower dissolved oxygen, elevated pH) conducive to the release of phosphorus from sediment.  The aim of this project was to identify why Phormidium proliferates in certain parts of the Hutt and Waipoua rivers, as well as investigate the relationship between fine sediment and mat growth. Monitoring of river data was carried out in the Hutt and Waipoua Rivers between November 2014 and May 2015. Over this period, physicochemical and hydrological data was monitored to identify the influencing factors of Phormidium abundance. During February 2015, sediment traps were deployed to determine the sedimentation rates in parallel to Phormidium cover at each site. The collected fine sediment was fractionated and analysed for biologically available phosphorus. Finally, a manipulative study using stream channel mesocosms was undertaken to provide causative evidence that fine sediment deposition influences Phormidium growth. In this three-week study, four mesocosms were deployed containing different fine sediment treatments. Biomass samples were collected at regular intervals to determine total photosynthetic biomass and Phormidium specifically.  Phormidium cover during 2014-15 was influenced by water column nitrate-nitrite nitrogen concentrations and sediment deposition. Phormidium cover was considerably lower compared to previous years, with a maximum cover of 20.7% occurring in the Hutt River during February 2015. Analysis of historical flow and nutrient data suggests that the annual variation in Phormidium proliferation over the summer months was site specific and not generally driven by flow or nutrient concentrations.  It is likely that fine sediment plays a role in providing Phormidium mats with phosphorus in the Hutt and Waipoua River. This is shown through phosphorus concentrations within Phormidium mat water, which were 200-fold higher than the bulk water column. Maximum values of sedimentation, 272.0 g/m²/day, and biologically available phosphorus (bound to sediment) 1.4 mg P g⁻¹, occurred at sites with the highest Phormidium cover, which further confirms this correlation. Furthermore, mesocosm experiments showed that Phormidium biomass increased significantly (p=0.015) with an increased amount of sediment. However, the maximum biomass of 64.75 mg/m² did not occur in the mesocosm channel with the most sediment added to it. This suggests that a deposition threshold exists due to the attenuation of light.  Findings from this research provide some insights in to management options which may help to mitigate Phormidium proliferations in the future. The data indicates that reducing sediment inputs, or resuspension of fine sediment during flood remediation works, would reduce Phormidium proliferations. Riparian planting as well as the collaboration with local councils is needed to help reduce diffuse and remaining point sources of sediment and river bed disturbance during flood protection activities. Using a combination of observational and experimental studies, this research has shown that multiple factors influence Phormidium proliferation, and has highlighted the key role that fine sediment plays. Suggestions for future studies include in-river experiments to further explore the role of fine sediment and the optimisation of mesocosms, which may also help to investigate finer scale data on causative factors such as sediment thresholds.</p>

Nutrient pollution at the lower reaches of Mediterranean coastal rivers in Israel

2000 ◽  
Vol 42 (1-2) ◽  
pp. 147-152 ◽  
Author(s):  
B. Herut ◽  
N. Kress ◽  
H. Hornung
Keyword(s):  
Inorganic Nitrogen ◽  
Agricultural Runoff ◽  
Point Sources ◽  
Industrial Wastes ◽  
Nutrient Concentrations ◽  
Contamination Level ◽  
Nutrient Load ◽  
Nutrient Loads ◽  
Discharge Data ◽  
Coastal Rivers

This study represents the first attempt to evaluate the nutrient load introduced into the coastal waters by the rivers along the Mediterranean coast of Israel. Measurements of nutrient concentrations (phosphate, ammonium, nitrate, nitrite, silicic acid) at two or three stations along the lower river reaches (11 rivers) were carried out annually from 1990 up to 1998. Combining the nutrient concentrations with the monthly riverine discharges we assessed the nutrient load. In general, most of the coastal rivers contain high nutrient contamination level, compared to the criteria adopted by NOAA (USA) for coastal river estuaries. The high degree of contamination is attributed to extreme low natural flow combined with the discharge of domestic and industrial wastes, and with agriculture runoff. In terms of nutrient concentrations, the Kishon River is the most polluted, followed by the Soreq, Poleg and Alexander Rivers. The preliminary estimate is that the coastal rivers transport between ~2000 to 6000 tons of dissolved inorganic nitrogen (DIN) and between ~250–800 tons of dissolved inorganic phosphorus (DIP) to the sea. An additional 3500 and 3000 tons of DIN and DIP, respectively, are supplied through the Kishon River. The load of the Poleg River is unknown (no discharge data) but expected to be significant based on nutrient concentration measured. The total load of the coastal rivers constitutes a major component among the other land-base point sources such as the Gush Dan outfall. Our estimate probably represents minimal values, as it does not include diffused input of agricultural runoff nor the riverine particulate and dissolved organic nutrient loads (which are unknown).

Influence of climate,geology and humans on spatial and temporal nutrient geochemistry in the subtropical Richmond River catchment, Australia

2001 ◽  
Vol 52 (2) ◽  
pp. 235 ◽  
Author(s):  
Lester J. McKee ◽  
Bradley D. Eyre ◽  
Shahadat Hossain ◽  
Peter R. Pepperell
Keyword(s):  
Water Quality ◽  
Land Use ◽  
Agricultural Land ◽  
Anthropogenic Impacts ◽  
Inorganic Nitrogen ◽  
Point Sources ◽  
Nutrient Concentrations ◽  
Wet Season ◽  
Nitrogen And Phosphorus ◽  
River Catchment

Water quality was monitored on a spatial and temporal basis in the subtropical Richmond River catchment over two years. Nutrient concentrations varied seasonally in a complex manner with highest concentrations (maximum =3110 µg N L – 1 and 572 µg P L –1 ) associated with floods. However, median (444 µg N L – 1 and 55 µg P L – 1 ) concentrations were relatively low compared with other parts of the world. The forms of nitrogen and phosphorus in streams varied seasonally, with greater proportions of inorganic nitrogen and phosphorus during the wet season. Minimum nutrient concentrations were found 2—3 months after flood discharge. With the onset of the dry season, concentration increases were attributed to point sources and low river discharge. There were statistically significant relationships between geology and water quality and nutrient concentrations increased downstream and were significantly related to population density and dairy farming. In spite of varying geology and naturally higher phosphorus in soils and rocks in parts of the catchment, anthropogenic impacts had the greatest effects on water quality in the Richmond River catchment. Rainfall quality also appeared to be related both spatially and seasonally to human activity. Although the responses of the subtropical Richmond River catchment to changes in land use are similar to those of temperate systems of North America and Europe, the seasonal patterns appear to be more complex and perhaps typical of subtropical catchments dominated by agricultural land use.

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 Land Uses, Altitude and Texture Effects on Soil Parameters. A Comparative Study in Two Districts of Nagaland, Northeast India

Agriculture ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 171
Author(s):  
Gaurav Mishra ◽  
Rosa Francaviglia
Keyword(s):  
Soil Properties ◽  
Soil Texture ◽  
Soil Parameters ◽  
Available Phosphorus ◽  
Land Uses ◽  
Management Options ◽  
Available N ◽  
P Content ◽  
Significant Difference ◽  
Soc Stocks

Northeast (NE) India is a typical tropical ecosystem with a luxuriant forest vegetation cover, but nowadays forests are under stress due to exploitation and land use changes, which are known to affect soil health and productivity. However, due to a scarcity of data, the influence of land uses and altitude on soil properties of this peculiar ecosystem is poorly quantified. This study presents the changes in soil properties in two districts of Nagaland (Mon and Zunheboto) in relation to land uses (forest, plantation, jhum and fallow jhum), altitude (<500 m, 500–1000 m, >1000 m) and soil texture (coarse, medium, fine). For this, a random soil sampling was performed in both the districts. Results indicated that soil organic carbon (SOC) stocks and available potassium (K) were significantly influenced by land uses in the Mon district, while in Zunheboto a significant difference was observed in available phosphorus (P) content. SOC stocks showed an increasing trend with elevation in both districts. The influence of altitude on P was significant and the maximum concentration was at lower elevations (<500 m). In Mon, soil texture significantly affected SOC stocks and the available N and P content. The variability in soil properties due to land uses, altitudinal gradients and textural classes can be better managed with the help of management options, which are still needed for this ecosystem.

Spatial Patterns and Drivers of Soil Chemical Properties in a Typical Hickory Plantation

2021 ◽  
Author(s):  
Mengjiao Sun ◽  
Enqing Hou ◽  
Jiasen Wu ◽  
Jianqin Huang ◽  
Xingzhao Huang
Keyword(s):  
Random Forest ◽  
Soil Nutrients ◽  
Spatial Patterns ◽  
Abiotic Factors ◽  
Soil Nutrient ◽  
Parent Material ◽  
Mean Annual Precipitation ◽  
Nutrient Concentrations ◽  
Available Phosphorus ◽  
Mean Annual Temperature

Abstract Background: Soil nutrients play critical roles in regulating and improving the sustainable development of economic forests. Consequently, an elucidation of the spatial patterns and drivers of soil nutrients in these forests is fundamental to their management. For this study, we collected 314 composite soils at a 0-30 cm depth from a typical hickory plantation in Lin 'an, Zhejiang Province, China. We determined the concentrations of macronutrients (i.e., soil organic carbon, hydrolyzed nitrogen, available phosphorus, and available potassium) and micronutrients (i.e., iron, manganese, zinc, and copper.) of the soils. We employed random forest analysis to quantify the relative importance of soil-forming factors to predict the soil nutrient concentrations, which could then be extrapolated to the entire hickory region. Results: Random forest models explained 61%–88% of the variations in soil nutrient concentrations. The mean annual temperature and mean annual precipitation were the most important predictor of soil macronutrient and micronutrient concentrations. Moreover, parent material was another key predictor of soil available phosphorus and micronutrient concentrations. Mapping results demonstrated the importance of climate in controlling the spatial distribution of soil nutrient concentrations at finer scales, as well as the effect of parent material, topography, stand structure, and management measures of hickory plantations. Conclusions: Our study highlights the biotic factors, abiotic factors, and management factors control over soil macronutrient and micronutrient concentrations, which have significant implications for the sustainability of soil nutrients in forest plantations.

scholarly journals Impact of the Kuroshio intrusion on the nutrient inventory in the upper northern South China Sea: insights from an isopycnal mixing model

2013 ◽  
Vol 10 (10) ◽  
pp. 6419-6432 ◽  
Author(s):  
C. Du ◽  
Z. Liu ◽  
M. Dai ◽  
S.-J. Kao ◽  
Z. Cao ◽  
...  
Keyword(s):  
South China Sea ◽  
Water Column ◽  
South China ◽  
Water Mass ◽  
Northern South China Sea ◽  
Mixing Model ◽  
Nutrient Concentrations ◽  
Kuroshio Intrusion ◽  
China Sea ◽  
The Kuroshio

Abstract. Based on four cruises covering a seasonal cycle in 2009–2011, we examined the impact of the Kuroshio intrusion, featured by extremely oligotrophic waters, on the nutrient inventory in the central northern South China Sea (NSCS). The nutrient inventory in the upper 100 m of the water column in the study area ranged from ∼200 to ∼290 mmol m−2 for N + N (nitrate plus nitrite), from ∼13 to ∼24 mmol m−2 for soluble reactive phosphate and from ∼210 to ∼430 mmol m−2 for silicic acid. The nutrient inventory showed a clear seasonal pattern with the highest value appearing in summer, while the N + N inventory in spring and winter had a reduction of ∼13 and ∼30%, respectively, relative to that in summer. To quantify the extent of the Kuroshio intrusion, an isopycnal mixing model was adopted to derive the proportional contribution of water masses from the SCS proper and the Kuroshio along individual isopycnal surfaces. The derived mixing ratio along the isopycnal plane was then employed to predict the genuine gradients of nutrients under the assumption of no biogeochemical alteration. These predicted nutrient concentrations, denoted as Nm, are solely determined by water mass mixing. Results showed that the nutrient inventory in the upper 100 m of the NSCS was overall negatively correlated to the Kuroshio water fraction, suggesting that the Kuroshio intrusion significantly influenced the nutrient distribution in the SCS and its seasonal variation. The difference between the observed nutrient concentrations and their corresponding Nm allowed us to further quantify the nutrient removal/addition associated with the biogeochemical processes on top of the water mass mixing. We revealed that the nutrients in the upper 100 m of the water column had a net consumption in both winter and spring but a net addition in fall.

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