scholarly journals Assessing interannual variability in nitrogen sourcing and retention through hybrid Bayesian watershed modeling

2021 ◽  
Vol 25 (5) ◽  
pp. 2789-2804
Author(s):  
Jonathan W. Miller ◽  
Kimia Karimi ◽  
Arumugam Sankarasubramanian ◽  
Daniel R. Obenour
Keyword(s):  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Nutrient Loading ◽  
Nutrient Management ◽  
Transport Model ◽  
Watershed Modeling ◽  
Point Sources ◽  
Low Flow ◽  
Bayesian Hierarchical ◽  
Order Of Magnitude

Abstract. Excessive nutrient loading is a major cause of water quality problems worldwide, often leading to harmful algal blooms and hypoxia in lakes and coastal systems. Efficient nutrient management requires that loading sources are accurately quantified. However, loading rates from various urban and rural non-point sources remain highly uncertain especially with respect to climatological variation. Furthermore, loading models calibrated using statistical techniques (i.e., hybrid models) often have limited capacity to differentiate export rates among various source types, given the noisiness and paucity of observational data common to many locations. To address these issues, we leverage data for two North Carolina Piedmont river basins collected over three decades (1982–2017) using a mechanistically parsimonious watershed loading and transport model calibrated within a Bayesian hierarchical framework. We explore temporal drivers of loading by incorporating annual changes in precipitation, land use, livestock, and point sources within the model formulation. Also, different representations of urban development are compared based on how they constrain model uncertainties. Results show that urban lands built before 1980 are the largest source of nutrients, exporting over twice as much nitrogen per hectare than agricultural and post-1980 urban lands. In addition, pre-1980 urban lands are the most hydrologically constant source of nutrients, while agricultural lands show the most variation among high- and low-flow years. Finally, undeveloped lands export an order of magnitude (∼7–13×) less nitrogen than built environments.

scholarly journals Assessing inter-annual variability in nitrogen sourcing and retention through hybrid Bayesian watershed modeling

2021 ◽  
Author(s):  
Jonathan W. Miller ◽  
Kimia Karimi ◽  
Arumugam Sankarasubramanian ◽  
Daniel R. Obenour
Keyword(s):  
Nutrient Loading ◽  
Nutrient Management ◽  
Transport Model ◽  
Watershed Modeling ◽  
Point Sources ◽  
Low Flow ◽  
Built Environments ◽  
Bayesian Hierarchical ◽  
Order Of Magnitude ◽  
Constant Source

Abstract. Excessive nutrient loading is a major cause of water quality problems worldwide, including in North Carolina (NC), where reservoirs and coastal systems are often subject to excessive algae and hypoxia. Efficient nutrient management requires that loading sources are accurately quantified. However, loading rates from various urban and rural non-point sources remain highly uncertain especially with respect to climatological variation. Furthermore, statistical calibration of loading models does not always yield plausible results, given the noisiness and paucity of observational data common to many locations. To address these issues, we leverage data for two large NC Piedmont basins collected over three decades (1982–2017) using a mechanistically parsimonious watershed loading and transport model calibrated within a Bayesian hierarchical framework. We explore temporal drivers of loading by incorporating annual changes in precipitation, land use, livestock, and point sources within the model formulation. Also, different representations of urban development are compared based on how they constrain model uncertainties. Results show that urban lands built before 1980 are the largest source of nutrients, exporting over twice as much nitrogen per hectare than agricultural and post-1980 urban lands. In addition, pre-1980 urban lands are the most hydrologically constant source of nutrients, while agricultural lands show the most variation among high and low flow years. Finally, undeveloped lands export an order of magnitude (~ 7–13x) less nitrogen than built environments.

Harmful algal blooms as a sink for inorganic nutrients in a eutrophic estuary

2021 ◽  
Vol 663 ◽  
pp. 63-76
Author(s):  
DA Lemley ◽  
JB Adams ◽  
JL Largier
Keyword(s):  
Coastal Waters ◽  
Harmful Algal Blooms ◽  
Phytoplankton Biomass ◽  
Algal Blooms ◽  
Nutrient Dynamics ◽  
Nutrient Loading ◽  
Positive Association ◽  
Inorganic Nutrient ◽  
Study Objective ◽  
Hydrological Variability

Phytoplankton-mediated nutrient fluxes typically provide only pulsed relief to adjacent coastal waters during the productive period, with nutrient export increasing in the absence of substantial phytoplankton biomass. On the warm temperate coastline of South Africa, the Sundays Estuary is characterised by highly regulated freshwater inflow patterns, nutrient-enriched conditions, and resident harmful algal blooms (HABs). Given these attributes, the study objective was to investigate the effect of these phytoplankton blooms on fluvial inorganic nutrient dynamics. To assess uptake, we analysed inorganic nutrient (phosphate, ammonium, NOx) and phytoplankton concentrations in relation to salinity using data from 17 surveys. Property-salinity mixing diagrams and statistical analyses indicated a positive association between increasing phytoplankton biomass and decreasing NOx flux (p < 0.001), and to a lesser degree phosphate flux (p = 0.22), along the gradient from low-salinity inner estuary to high salinity outer estuary. High biomass HAB accumulations of Heterosigma akashiwo (>100 µg chl a l-1) represent significant removal of available NOx (~100%) and phosphate (>75%) during warmer conditions (>20°C). These events, together with continuous inorganic nutrient uptake during less severe bloom conditions, remove a substantial portion of annual NOx and phosphate loads (36.5 and 36.4% flux, respectively). Although this buffers inorganic nutrient loading to adjacent coastal waters, it also represents an emerging legacy pollution issue in the form of a benthic accumulation of organic material in bottom waters subject to recurrent hypoxia. Future management efforts should adopt an ecosystem-based approach centred around simultaneous restoration of hydrological variability and dual nutrient reduction strategies (N and P).

scholarly journals Spatiotemporal Distribution of Harmful Algal Flora in the Tropical Estuarine Complex of Goa, India

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Suraksha M. Pednekar ◽  
S. G. Prabhu Matondkar ◽  
Vijaya Kerkar
Keyword(s):  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Nutrient Loading ◽  
Algal Species ◽  
Spatiotemporal Variability ◽  
Algal Flora ◽  
The Past ◽  
Tropical Estuarine ◽  
Mandovi And Zuari Estuaries ◽  
Hab Species

Mandovi and Zuari estuarine complex is monsoon-influenced estuaries located along the central west coast of India. During the past few years, there has been an increase in nutrient loading specially during monsoonal runoff which is responsible for the growth of harmful algal flora. To understand occurrence and distribution of harmful algal blooms species, daily/alternate day samplings were carried out in Mandovi and Zuari estuaries during 2007-2008 and 2008-2009 periods, respectively, comprising of monsoon (June–November) and nonmonsoon (December–May). In Mandovi, total 54 HAB species with 49 in monsoon and 36 during nonmonsoon period were reported. In Zuari, total 46 HAB species with 38 in monsoon and 41 were reported during nonmonsoon period. Bray-Curtis cluster analysis based on log-transformed phytoplankton density detected seven well-defined groups revealing spatiotemporal variability. The density of the dominant harmful algal species was significantly positively correlated with nutrients, but negatively correlated with salinity. The results of the study indicate that monsoon plays an important role in occurrence and distribution of harmful algal species having direct correlation with salinity variations and nutrient loading.

scholarly journals Developing an Atlas of Harmful Algal Blooms in the Red Sea: Linkages to Local Aquaculture

2020 ◽  
Vol 12 (22) ◽  
pp. 3695
Author(s):  
Elamurugu Alias Gokul ◽  
Dionysios E. Raitsos ◽  
John A. Gittings ◽  
Ibrahim Hoteit
Keyword(s):  
Saudi Arabia ◽  
Red Sea ◽  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Large Scale ◽  
Nutrient Loading ◽  
National Level ◽  
Spatiotemporal Variability ◽  
Wastewater Management ◽  
Spatial Coverage

Harmful algal blooms (HABs) are one of the leading causes of biodiversity loss and alterations to ecosystem services. The Red Sea is one of the least studied large marine ecosystems (LMEs), and knowledge on the large-scale spatiotemporal distribution of HABs remains limited. We implemented the recently developed remote sensing algorithm of Gokul et al. (2019) to produce a high-resolution atlas of HAB events in the Red Sea and investigated their spatiotemporal variability between 2003 and 2017. The atlas revealed that (i) the southern part of the Red Sea is subject to a higher occurrence of HABs, as well as long-lasting and large-scale events, in comparison to the northern part of the basin, and (ii) the Red Sea HABs exhibited a notable seasonality, with most events occurring during summer. We further investigated the potential interactions between identified HAB events and the National Aquaculture Group (NAQUA), Al-Lith (Saudi Arabia)—the largest aquaculture facility on the Red Sea coast. The results suggest that the spatial coverage of HABs and the elevated chlorophyll-a concentration (Chl-a) (> 1 mg m−3; a proxy for high nutrient concentration), in the coastal waters of Al-Lith during summer, increased concurrently with the local aquaculture annual production over a nine-year period (2002–2010). This could be attributed to excessive nutrient loading from the NAQUA facility’s outfall, which enables the proliferation of HABs in an otherwise oligotrophic region during summer. Aquaculture is an expanding, high-value industry in the Kingdom of Saudi Arabia. Thus, a wastewater management plan should ideally be implemented at a national level, in order to prevent excessive nutrient loading. Our results may assist policy-makers’ efforts to ensure the sustainable development of the Red Sea’s coastal economic zone.

scholarly journals Nutrient Loading and Viral Memory Drive Accumulation of Restriction Modification Systems in Bloom-Forming Cyanobacteria

mBio ◽  
2021 ◽  
Author(s):  
Spiridon E. Papoulis ◽  
Steven W. Wilhelm ◽  
David Talmy ◽  
Erik R. Zinser
Keyword(s):  
Water Quality ◽  
Microcystis Aeruginosa ◽  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Nutrient Loading ◽  
Major Contributor ◽  
Content Type ◽  
Global Threat ◽  
Restriction Modification ◽  
Restriction Modification Systems

Harmful algal blooms (HABs), caused by cyanobacteria like Microcystis aeruginosa , are a global threat to water quality and use across the planet. Researchers have agreed that nutrient loading is a major contributor to HAB persistence.

scholarly journals A global scan of how the issue of nutrient loading and harmful algal blooms is being addressed by governments, non-governmental organizations, and volunteers

2019 ◽  
Vol 55 (1) ◽  
pp. 1-23
Author(s):  
Étienne Foulon ◽  
Alain N. Rousseau ◽  
Glenn Benoy ◽  
Rebecca L. North
Keyword(s):  
Water Quality ◽  
Case Studies ◽  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Nutrient Loading ◽  
Risk Mitigation ◽  
National Standards ◽  
Quality Issue ◽  
Non Governmental Organizations ◽  
The Usa

Abstract Harmful algal blooms (HABs) in aquatic ecosystems are of concern worldwide. This review deals with how jurisdictions around the world are addressing this water quality issue to inform recommendations regarding nutrient loading and HABs in Missisquoi Bay-Lake Champlain and Lake Memphremagog; transboundary lakes located in the USA and Canada that suffer from symptoms of eutrophication. A global scan of the literature resulted in the consideration of 12 case studies of large water bodies within large watersheds, excluding in-lake geoengineering approaches. Although all of the systems experience excessive nutrient loading, they vary in two key ways: sources of nutrients and manifestations of eutrophication ranging from HABs, to limited recreational uses, to the additional complexity of internal loadings and fish kills, up to drinking water shutdowns. The case studies were analyzed with respect to four categories of approaches, namely: (i) regulatory; (ii) incentive-based; (iii) risk mitigation; and (iv) outreach, engagement, and educational. We found that the management frameworks are based on integrated watershed management planning and national standards. National water quality standards, however, are not stringent enough to prevent HABs. Overall, identified case studies did not successfully remediate HABs, they simply managed them.

Role and efficacy of marine protected areas for the South African rock lobster, Jasus lalandii

2005 ◽  
Vol 56 (6) ◽  
pp. 913 ◽  
Author(s):  
Stephen Mayfield ◽  
George M. Branch ◽  
Andrew C. Cockcroft
Keyword(s):  
Protected Areas ◽  
South African ◽  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Egg Production ◽  
Marine Reserve ◽  
Rock Lobster ◽  
The South ◽  
Order Of Magnitude ◽  
St Helena

Protected areas for the South African rock lobster, Jasus lalandii, were sampled by using divers, traps and ringnets at sites within and adjacent to four protected areas (St Helena Bay, Saldanha Bay and Table Bay rock lobster sanctuaries and the Betty’s Bay marine reserve), over two years. Virtually no rock lobsters were found in St Helena Bay sanctuary, probably because of periodic harmful algal blooms. Abundance was greater in Saldanha Bay sanctuary than in adjacent fished areas, but only once in two years. Sizes were, however, larger in this sanctuary than the fished areas. By an order of magnitude, fewer and smaller rock lobsters were caught within the Table Bay sanctuary than in adjacent areas. Only at Betty’s Bay were rock lobster sizes and abundance consistently greater inside than outside the reserve. Fecundity was similar among sites, with females in protected areas contributing no more to egg production than would be expected by the proportional area occupied by protected areas. Rock lobsters do benefit from protection in Betty’s Bay reserve, but the west coast sanctuaries appear poorly located and seemingly contain large areas of unsuitable substrate. They clearly need relocation to be effective.

scholarly journals Model-based analysis of nutrient retention and management for a lowland river

2005 ◽  
Vol 2 (6) ◽  
pp. 2549-2579 ◽  
Author(s):  
D. Kneis ◽  
R. Knoesche ◽  
A. Bronstert
Keyword(s):  
Nutrient Loading ◽  
Nutrient Management ◽  
Transport Model ◽  
Nutrient Retention ◽  
Late Summer ◽  
Phosphorus Release ◽  
Lowland River ◽  
Nutrient Inputs ◽  
Nitrogen And Phosphorus ◽  
External Nutrient

Abstract. In the context of the European Water Framework Directive options for improving the water quality of the lowland river Havel (Germany) were assessed. The lower section of this river is actually a polytrophic river-lake system suffering from high external nutrient loading and exhibiting significant in-river turnover. In order to gain a better understanding of present conditions and to allow integrated scenarios of nutrient management to be evaluated the catchment models SWIM and ArcEGMO-Urban were coupled with a simple, newly developed nutrient TRAnsport Model (TraM). Using the TraM model, the retention of nitrogen and phosphorus in a 55 km reach of the Lower Havel River was quantified and its temporal variation was analyzed. It was examined that about 30% of the external nitrogen input to the Lower Havel is retained within the surveyed river section. A comparison of simulation results generated with and without consideration of phosphorus retention/release revealed that summer TP concentrations are currently increased by 100–200% due to internal loading. Net phosphorus release rates of about 20 mg P m−2 d-1 in late summer were estimated for the Havel lakes. Scenario simulations with lowered external nutrient inputs revealed that persistent phosphorus limitation of primary production cannot be established within the next decade. It was shown that a further reduction in nitrogen concentrations requires emissions to be reduced in all inflows. Though the TraM model needs further extension it proved to be appropriate for conducting integrated catchment and river modeling.

scholarly journals Extreme rainfall drives early onset cyanobacterial bloom

FACETS ◽  
2020 ◽  
Vol 5 (1) ◽  
pp. 899-920
Author(s):  
Megan L. Larsen ◽  
Helen M. Baulch ◽  
Sherry L. Schiff ◽  
Dana F. Simon ◽  
Sébastien Sauvé ◽  
...  
Keyword(s):  
Extreme Precipitation ◽  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Nutrient Loading ◽  
Climate Models ◽  
Cyanobacterial Bloom ◽  
Extreme Rainfall ◽  
Precipitation Event ◽  
Precipitation Frequency ◽  
Extreme Precipitation Events

The increasing prevalence of cyanobacteria-dominated harmful algal blooms is strongly associated with nutrient loading and changing climatic patterns. Changes to precipitation frequency and intensity, as predicted by current climate models, are likely to affect bloom development and composition through changes in nutrient fluxes and water column mixing. However, few studies have directly documented the effects of extreme precipitation events on cyanobacterial composition, biomass, and toxin production. We tracked changes in a eutrophic reservoir following an extreme precipitation event, describing an atypically early toxin-producing cyanobacterial bloom and successional progression of the phytoplankton community, toxins, and geochemistry. An increase in bioavailable phosphorus by more than 27-fold in surface waters preceded notable increases in Aphanizomenon flos-aquae throughout the reservoir approximately 2 weeks postevent and ∼5 weeks before blooms typically occur. Anabaenopeptin-A and three microcystin congeners (microcystin-LR, -YR, and -RR) were detected at varying levels across sites during the bloom period, which lasted between 3 and 5 weeks. These findings suggest extreme rainfall can trigger early cyanobacterial bloom initiation, effectively elongating the bloom season period of potential toxicity. However, effects will vary depending on factors including the timing of rainfall and reservoir physical structure.

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