Potential of aquatic weeds to improve water quality in natural waterways of the Zambezi catchment

Abstract One prominent effect of nutrient pollution of surface waters is the mass invasion of floating plants, which can clog waterways, disrupting human use of aquatic systems. These plants are widely vilified and motivate expensive control campaigns, but their presence may be providing a poorly recognized function in the cycling of excess nutrients. The capacity for floating plants to absorb nutrients from surface water has been understood for decades, primarily from their use in constructed wetlands for wastewater treatment. Yet, in natural settings, there has not been to date any effort to quantify whether floating plant invasions represent important pools or fluxes of nutrients relative to those of the river catchments in which they occur. We found that seasonal hydrologic cycles in the Zambezi trap and flush floating plants from river choke points, such as dams and river confluences, on an annual basis. Peak plant biomass at such choke points constitutes a proxy for estimating annual plant-bound nutrient loads. We assessed the significance of floating vegetation as nutrient sinks by comparing annual plant-bound nutrient loading to conventional river nutrient loading (dissolved and particulate) for four tributaries of the Zambezi River in Zambia. We found that the relative importance of floating vegetation was greatest in the more urbanized catchments, such as the Maramba River draining the city of Livingstone, representing approximately 30% and 9% of annual digestible phosphorus and nitrogen flux respectively. We also found plant-bound phosphorus to be important in the Kafue River (19%), draining the industrial town of Kafue and extensive sugarcane plantations. These results demonstrate the great potential of floating plants to take up excess nutrients from natural river systems. Given the importance of hydrology in the life cycle of floating vegetation, controlled dam discharges may have an important role in managing them and their water quality treatment functions.

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Mitigating Impacts of Natural Hazards on Fishery Ecosystems

Mitigating Impacts of Natural Hazards on Fishery Ecosystems ◽

10.47886/9781934874011.ch9 ◽

2008 ◽

Keyword(s):

Water Quality ◽

Nutrient Loading ◽

Water Quality Management ◽

River Estuary ◽

Chemical Properties ◽

Neuse River Estuary ◽

Estuarine System ◽

Nutrient Loads ◽

Habitat Alterations ◽

The Past

<em>Abstract</em>.—Since the mid-1990s, the U.S. mid-Atlantic region has witnessed a sudden rise in hurricane and tropical storm landfalls. In particular, eastern North Carolina has been impacted by eight hurricanes and six tropical storms in the past decade, and this relatively high frequency is forecast to continue for the next several decades. Each of the past storms exhibited unique hydrologic and nutrient loading scenarios for the Pamlico Sound, the United States’ second largest estuarine system and its largest subestuary, the Neuse River estuary. This variability represents a challenge to nutrient management aimed at protecting water quality and ensuring optimal fisheries habitat conditions. Different rainfall amounts among hurricanes led to variable freshwater and nutrient discharge and hence variable nutrient, organic matter, and sediment enrichment. These enrichments differentially affected physical and chemical properties (salinity, water residence time, transparency, stratification, dissolved oxygen), phytoplankton primary production, and phytoplankton community composition. The contrasting effects were accompanied by biogeochemical perturbations (hypoxia, enhanced nutrient cycling), benthic and planktonic habitat alterations, and possibly food web disturbances. Floodwaters from the two largest hurricanes, Fran (1996) and Floyd (1999), exerted multimonth to multiannual effects on hydrology, nutrient loads, productivity, biotic composition, and habitat condition. In contrast, relatively low rainfall coastal hurricanes like Isabel (2003) and Ophelia (2005) caused strong vertical mixing and storm surges but exhibited relatively minor hydrologic, nutrient, and biotic impacts. Both hydrologic and wind forcing are important drivers and must be integrated with nutrient loading in assessing short- and long-term ecological impacts of these storms. These climatic forcings cannot be managed but must be considered when developing water quality management strategies for these and other large estuarine ecosystems faced with increasing frequencies and intensities of hurricane activity.

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Changes in land use in the buffer zone of lake of the Mała Wełna catchment

Limnological Review ◽

10.2478/v10194-011-0043-z ◽

2012 ◽

Vol 12 (1) ◽

pp. 35-44 ◽

Cited By ~ 1

Author(s):

Mariusz Ptak ◽

Agnieszka E. Ławniczak

Keyword(s):

Water Quality ◽

Land Use ◽

Nutrient Loading ◽

Lake Management ◽

Buffer Zone ◽

Nutrient Loads ◽

Buffer Zones ◽

Nutrient Sources ◽

Forested Areas ◽

Water Pollutant

Abstract One of the most important elements in the protection of water quality is buffer zones. In order to protect water quality, appropriate management of these areas is necessary. In the paper, changes in the land use in the buffer zone of 200 m width around lakes in the Mała Wełna catchment over 20 years were analysed. For the study eight lakes larger than 50 ha were chosen. Changes in the land use within the buffer zone were studied from 1980 to 2000, based on topographic maps in the scale 1:10 000. Results show both positive and negative aspects of land changes. An increase in forested areas and grasslands through tilled land were positive aspects of these changes. On the other hand, the enhancement of suburban development in these zones caused increased probability of water pollution from these areas. Calculations of potential nutrient loading from different types of land use in these zones indicated an enhancement of nutrient sources in the lakes within the 20-year study period. However, these changes are not significant in comparison to the nutrient loads contributed by the tributaries. Our study indicated that in the case of flow lakes, more important is an improvement in water quality in the tributaries and a reduction in nutrient sources in the catchment with the purpose of reducing the input of nutrients into the lake. Management of the buffer zone is one of the issues which have to be taken into consideration in lake protection after elimination of the major water pollutant sources.

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Water quality and phytoplankton dynamics in Moreton Bay, south-eastern Queensland. II. Mathematical modelling.

Marine and Freshwater Research ◽

10.1071/mf97123 ◽

1998 ◽

Vol 49 (3) ◽

pp. 227 ◽

Cited By ~ 10

Author(s):

James McEwan ◽

Albert J. Gabric ◽

Peter R. F. Bell

Keyword(s):

Water Quality ◽

Field Data ◽

Nutrient Loading ◽

Light Availability ◽

Population Pressure ◽

Eastern Region ◽

Nutrient Loads ◽

Quality Model ◽

Moreton Bay ◽

European Settlement

A coupled hydrodynamic water-quality model of Moreton Bay was developed to enable better management of nutrient loads and to predict eutrophication-related problems. The hydrodynamic submodel was calibrated to available tidal data, and the transport submodel was calibrated to a salinity dataset. A 15-month time-series of field data was used together with historical data to calibrate and validate the water-quality submodel. Model simulations suggest that denitrification removes over half the external N inputs with about one-third exported to the open ocean. Approximately 8% of N and 20% of the P loading accumulates in the sediments. Short-term variations due to hydrodynamic effects tend to mask the seasonal cycle in phytoplankton biomass except at inshore localities. The model predictions confirm the field data that indicate that water quality in the western bay is severely affected while the better flushed eastern region remains relatively unaffected. Future increases in nutrient loading due to population pressure are predicted to extend the severely affected region eastwards. Over most of the bay, algal productivity is N-limited except for the western margins where nutrients are saturating and light availability regulates growth. Model hindcasts suggest that system-wide mean algal production has increased by a factor of ten since European settlement.

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Water quality and phytoplankton dynamics in Moreton Bay, south-eastern Queensland. I. Field survey and satellite data

Marine and Freshwater Research ◽

10.1071/mf95096 ◽

1998 ◽

Vol 49 (3) ◽

pp. 215 ◽

Cited By ~ 15

Author(s):

James McEwan ◽

Albert J. Gabric ◽

Peter R. F. Bell

Keyword(s):

Water Quality ◽

Nutrient Loading ◽

Population Expansion ◽

Water Clarity ◽

Western Boundary ◽

Nutrient Loads ◽

Moreton Bay ◽

South Eastern ◽

Temporal And Spatial Variability ◽

The Impact

The water quality of Moreton Bay, a sub-tropical estuarine embayment in south-eastern Queensland, was monitored over a 2-year period. Surveys in situ and ground-truthed satellite imagery were used to describe the temporal and spatial variability in water-quality indicators and the level of eutrophication. Strong east–west gradients in chlorophyll α and water clarity were found. During the study period fluvial discharges, which all enter on the western littoral, were below their long-term averages, and nutrient loading to the bay was dominated by point-source wastewater discharges along the western boundary. The data suggest that although the impact of nutrient loads on the bay’s eastern side is mitigated by tidal intrusion of oceanic water, the western areas are already degraded and can be considered mesotrophic to eutrophic. This part of the bay may deteriorate further with the projected future population expansion in the bay’s catchment.

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Impact of biomass burning on surface water quality in Southeast Asia through atmospheric deposition: eutrophication modeling

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-7779-2010 ◽

2010 ◽

Vol 10 (3) ◽

pp. 7779-7818 ◽

Cited By ~ 2

Author(s):

P. Sundarambal ◽

P. Tkalich ◽

R. Balasubramanian

Keyword(s):

Water Quality ◽

Surface Water ◽

Atmospheric Deposition ◽

Biomass Burning ◽

Nutrient Loading ◽

Surface Water Quality ◽

Companion Paper ◽

Temporal Variations ◽

Nutrient Loads ◽

Chemical Contamination

Abstract. A numerical modeling approach is proposed for the assessment of the nutrient loading of coastal waters from atmospheric sources. The 3-D eutrophication model NEUTRO was enhanced to simulate the spatial distribution and temporal variations of nutrients, planktons and dissolved oxygen due to atmospheric nutrient loadings. It was found that nutrient loading from the atmospheric wet and dry deposition was remarkable during hazy days, the contribution being between 2 and 8 times that of non-hazy days; the smoke haze was due to biomass burning in the Southeast Asian region as discussed in a companion paper on field observations. Atmospheric nutrient loads during hazy days can lead to anthropogenic eutrophication and chemical contamination. The importance of regional smoke haze events in relation to non-hazy days to atmospheric nutrient deposition in terms of their biological responses in the coastal water of the Singapore region was investigated. The percentage increases of surface water nutrients due to atmospheric deposition during non-hazy and hazy days from seawater baseline were estimated. Model computations showed that atmospheric fluxes might account for up to 17–88% of total mass of nitrate nitrogen in the water column during hazy days and 4 to 24% during non-hazy days, which might be a relatively significant contribution into regional eutrophication. The results obtained from the modeling study could be used for a better understanding of the energy flow through the marine food web, exploring various possible scenarios concerning the atmospheric deposition of nutrients onto the coastal zone and studying their impacts on water quality.

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Effective Management of Closed Hypereutrophic Estuaries Requires Catchment-Scale Interventions

Frontiers in Marine Science ◽

10.3389/fmars.2021.688933 ◽

2021 ◽

Vol 8 ◽

Author(s):

Daniel A. Lemley ◽

Stephen J. Lamberth ◽

Warren Manuel ◽

Monique Nunes ◽

Gavin M. Rishworth ◽

...

Keyword(s):

Water Quality ◽

Community Dynamics ◽

Nutrient Loading ◽

Harmful Algal Bloom ◽

High Water ◽

Water Levels ◽

Nutrient Loads ◽

Catchment Scale ◽

Management Interventions ◽

And Shifts

Increased nutrient loading associated with rapid population growth is the leading cause of deteriorating water quality in urbanized estuaries globally. Small estuaries are particularly sensitive to changes when connection with the marine environment is restricted, or lost, because of high water retention. The temporarily closed Hartenbos Estuary (South Africa) is an example of how such pressures can culminate in a severely degraded ecosystem. Wastewater treatment work (WWTW) discharges introduce substantial volumes of freshwater (8,000 m3 d–1) and nutrient loads (38 kg DIN d–1 and 22 kg DIP d–1) into this estuary. This constant inflow has necessitated frequent artificial breaching (inducing alternating states) of the estuary mouth to prevent flooding of low-lying developments and, occasionally, to mitigate against extreme events such as fish kills and sewage spills. This study investigated the efficacy of artificial mouth breaching practices in eliciting responses in selected abiotic and biotic parameters. Microalgal (phytoplankton and benthic diatoms), benthic macrofauna and fish community dynamics were assessed in response to mouth state and water quality conditions using a seasonal monitoring programme. The hypereutrophic nature of the Hartenbos Estuary was highlighted by persistent high-biomass phytoplankton accumulations (>100 μg Chl-a l–1), extreme dissolved oxygen conditions (0.4–20.5 mg O2 l–1) and the predominance of harmful algal bloom (HAB) events comprising Nannochloropsis sp. and Heterosigma akashiwo. Artificial breaching of the mouth facilitated limited tidal exchange and occurred approximately bimonthly once water levels exceeded 1.9 m above mean sea level (MSL). Current pressures and management interventions have culminated in an ecosystem void of natural fluctuations and instead characterised by low diversity and shifts between undesirable states. This is highlighted by the near year-round dominance of only a few opportunistic species/groups tolerant of adverse conditions (e.g., Nannochloropsis sp., Halamphora coffeiformis, oligochaetes, estuarine round herring Gilchristella aestuaria, and southern mullet Chelon richardsonii). Therefore, catchment-scale interventions such as the diversion of WWTW discharges and restoration of hydrodynamic variability are management priorities for improving the health and biodiversity of small, closed microtidal systems such as the Hartenbos Estuary.

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Assessing the Market for Poultry Litter in Georgia: Are Subsidies Needed to Protect Water Quality?

Journal of Agricultural and Applied Economics ◽

10.1017/s1074070800000079 ◽

2011 ◽

Vol 43 (4) ◽

pp. 553-568 ◽

Cited By ~ 3

Author(s):

Jeffrey Mullen ◽

Ulugbek Bekchanov ◽

Berna Karali ◽

David Kissel ◽

Mark Risse ◽

...

Keyword(s):

Water Quality ◽

Poultry Litter ◽

Focused Attention ◽

Water Protection ◽

Nutrient Loads ◽

Transportation Model ◽

Synthetic Fertilizer ◽

Protection Goals ◽

Subsidy Program ◽

The Relationship

Concerns about nutrient loads into our waters have focused attention on poultry litter applications. Like many states with a large poultry industry, Georgia recently designed a subsidy program to facilitate the transportation of poultry litter out of vulnerable watersheds. This paper uses a transportation model to examine the necessity of a poultry litter subsidy to achieve water protection goals in Georgia. We also demonstrate the relationship between diesel and synthetic fertilizer prices and the value of poultry litter. Results suggest that a well-functioning market would be able to remove excess litter from vulnerable watersheds in the absence of a subsidy.

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Effects of Different Fish Diets on the Water Quality in Semi-Intensive Common Carp (Cyprinus carpio) Farming

Water ◽

10.3390/w13091215 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1215

Author(s):

László Berzi-Nagy ◽

Attila Mozsár ◽

Flórián Tóth ◽

Dénes Gál ◽

Zoltán Nagy ◽

...

Keyword(s):

Water Quality ◽

Common Carp ◽

Cyprinus Carpio ◽

Nutrient Loading ◽

Fish Meal ◽

Pond Water ◽

Long Term Effects ◽

Plant Oil ◽

Common Carp Cyprinus Carpio ◽

Carp Cyprinus Carpio

Semi-intensive common carp (Cyprinus carpio) farm technology uses several feed types affecting the growth performance; however, we know less about their long-term effects on water quality. Herein, we evaluated the effects of three commonly used feeds—moderate levels of fish meal and fish oil feed (FF), plant meal and plant oil feed (PF), and cereal feed (CF) on the nutrient (total nitrogen (TN), total phosphorus (TP) and organic matter (OM)) content of the pond water. The experiment was carried out over three consecutive years from juveniles to market-sized fish. The type of feed affected the net yields, but generally, it did not affect the water quality. The year of sampling, however, was a significant factor affecting TN, TP, and OM, whose concentrations decreased during the three years. Our findings highlight that the age of the stocked fish on water quality has a more pronounced effect than the nutrient profile of the supplementary feed. Additionally, the plant-based feed could provide comparable net yields as the fish meal-based feed without additional nutrient loading in the water column, reinforcing the sustainability of alternative feeds in semi-intensive carp farming.

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Suggestions for a Modified Approach Towards Implementation and Assessment of Ganga Action Plan and Other Similar River Action Plans in India

Water Quality Research Journal ◽

10.2166/wqrj.2003.039 ◽

2003 ◽

Vol 38 (4) ◽

pp. 607-626 ◽

Cited By ~ 5

Author(s):

Vinod Tare ◽

Purnendu Bose ◽

Santosh K. Gupta

Keyword(s):

Water Quality ◽

River Water ◽

Public Perception ◽

Nutrient Loading ◽

Action Plan ◽

Public Support ◽

Uttar Pradesh ◽

River Water Quality ◽

Point Sources ◽

Action Plans

Abstract In India, the implementation of river-cleaning operations through River Action Plans (RAPs) conventionally focuses on a reduction in concentrated or point sources of organic loading to the river, and is assessed by monitoring the consequent improvement in river water quality. However, in the case of Indian rivers or river stretches having substantial background pollution due to distributed or non-point loading of organic matter and nutrients, elimination of point sources of pollution may not substantially impact or improve river water quality. It is suggested that implementation of River Action Plans in India under such circumstances must be conducted using a multi-tier approach. The initial emphasis in such cases should be on the selection of priority stretches of the river, where pollution control will have maximum beneficial impact on the citizens, and interception and diversion of all concentrated or point loads of pollution from these stretches. In addition, measures to minimize non-point pollution and visible pollution to the river and initiation of riverfront restoration and development projects are necessary in these priority stretches. Such measures would result in aesthetic improvements, increase the beneficial uses of the river and its surroundings, and generate favorable public perception towards RAPs, though they may not be sufficient to enhance the river water quality to the desired levels. However, as a result of the above actions, public support for funding more expensive and longer-term river cleaning schemes, resulting in comprehensive reduction in organic and nutrient loading to the river from point and non-point sources all along its length, may be generated. The need for this alternative methodology for implementation and assessment of RAPs in India has been illustrated by taking the example of the Ganga Action Plan (GAP) and assessment of its implementation near the city of Kanpur in the state of Uttar Pradesh, India, as a test case.

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