scholarly journals From heterotrophy to autotrophy: a freshwater estuarine ecosystem recovering from hypereutrophication

2009 ◽  
Vol 6 (3) ◽  
pp. 5431-5459 ◽  
Author(s):  
T. J. S. Cox ◽  
T. Maris ◽  
K. Soetaert ◽  
D. J. Conley ◽  
S. Van Damme ◽  
...  
Keyword(s):  
Algal Blooms ◽  
Alternative Stable States ◽  
Algal Growth ◽  
Nutrient Loads ◽  
Nutrient Inputs ◽  
Stable States ◽  
Estuarine Ecosystem ◽  
High Ammonia ◽  
Estuarine Systems ◽  
Algal Growth Inhibition

Abstract. Increased organic matter and nutrient loads have induced major changes in aquatic systems, including hypoxia and algal blooms. In enclosed ecosystems these changes were often not gradual due to non-linear mechanisms. Here we report a 40 year record of eutrophication and hypoxia on an estuarine ecosystem and its recovery from hypereutrophication. We observe a paradoxical increase in chlorophyll a concentrations with decreasing nutrient inputs, and we hypothesise that algal growth was inhibited due to hypereutrophication, either by elevated ammonium concentrations, severe hypoxia or the production of harmful substances in such a reduced environment. We study the dynamics of a simple but realistic mathematical model, incorporating the assumption of algal growth inhibition. It shows an autotrophic equilibrium with low ammonia inputs, and a heterotrophic equilibrium with high ammonia inputs. At intermediate ammonia inputs it displays two alternative stable states. We conclude that the recovery of hypereutrophic riverine/estuarine systems can exhibit threshold-like behaviour.

scholarly journals A macro-tidal freshwater ecosystem recovering from hypereutrophication: the Schelde case study

2009 ◽  
Vol 6 (12) ◽  
pp. 2935-2948 ◽  
Author(s):  
T. J. S. Cox ◽  
T. Maris ◽  
K. Soetaert ◽  
D. J. Conley ◽  
S. Van Damme ◽  
...  
Keyword(s):  
Growth Inhibition ◽  
Algal Biomass ◽  
Alternative Stable States ◽  
Algal Growth ◽  
Nutrient Concentrations ◽  
Freshwater Ecosystem ◽  
Nutrient Inputs ◽  
Stable States ◽  
Estuarine Ecosystem ◽  
Algal Growth Inhibition

Abstract. We report a 40 year record of eutrophication and hypoxia on an estuarine ecosystem and its recovery from hypereutrophication. After decades of high inorganic nutrient concentrations and recurring anoxia and hypoxia, we observe a paradoxical increase in chlorophyll-a concentrations with decreasing nutrient inputs. We hypothesise that algal growth was inhibited due to hypereutrophication, either by elevated ammonium concentrations, severe hypoxia or the production of harmful substances in such a reduced environment. We study the dynamics of a simple but realistic mathematical model, incorporating the assumption of algal growth inhibition. It shows a high algal biomass, net oxygen production equilibrium with low ammonia inputs, and a low algal biomass, net oxygen consumption equilibrium with high ammonia inputs. At intermediate ammonia inputs it displays two alternative stable states. Although not intentional, the numerical output of this model corresponds to observations, giving extra support for assumption of algal growth inhibition. Due to potential algal growth inhibition, the recovery of hypereutrophied systems towards a classical eutrophied state, will need reduction of waste loads below certain thresholds and will be accompanied by large fluctuations in oxygen concentrations. We conclude that also flow-through systems, heavily influenced by external forcings which partly mask internal system dynamics, can display multiple stable states.

scholarly journals Outsized nutrient contributions from small tributaries to a Great Lake

2020 ◽  
Vol 117 (45) ◽  
pp. 28175-28182
Author(s):  
Robert J. Mooney ◽  
Emily H. Stanley ◽  
William C. Rosenthal ◽  
Peter C. Esselman ◽  
Anthony D. Kendall ◽  
...  
Keyword(s):  
Algal Blooms ◽  
Lake Michigan ◽  
Nutrient Loading ◽  
The United States ◽  
Ecological Impacts ◽  
Water Bodies ◽  
Nutrient Loads ◽  
Nutrient Inputs ◽  
Small Streams ◽  
Large Water

Excessive nitrogen (N) and phosphorus (P) loading is one of the greatest threats to aquatic ecosystems in the Anthropocene, causing eutrophication of rivers, lakes, and marine coastlines worldwide. For lakes across the United States, eutrophication is driven largely by nonpoint nutrient sources from tributaries that drain surrounding watersheds. Decades of monitoring and regulatory efforts have paid little attention to small tributaries of large water bodies, despite their ubiquity and potential local importance. We used a snapshot of nutrient inputs from nearly all tributaries of Lake Michigan—the world’s fifth largest freshwater lake by volume—to determine how land cover and dams alter nutrient inputs across watershed sizes. Loads, concentrations, stoichiometry (N:P), and bioavailability (percentage dissolved inorganic nutrients) varied by orders of magnitude among tributaries, creating a mosaic of coastal nutrient inputs. The 6 largest of 235 tributaries accounted for ∼70% of the daily N and P delivered to Lake Michigan. However, small tributaries exhibited nutrient loads that were high for their size and biased toward dissolved inorganic forms. Higher bioavailability of nutrients from small watersheds suggests greater potential to fuel algal blooms in coastal areas, especially given the likelihood that their plumes become trapped and then overlap in the nearshore zone. Our findings reveal an underappreciated role that small streams may play in driving coastal eutrophication in large water bodies. Although they represent only a modest proportion of lake-wide loads, expanding nutrient management efforts to address smaller watersheds could reduce the ecological impacts of nutrient loading on valuable nearshore ecosystems.

Anthropogenic impacts on the ecosystems of coastal lagoons: modelling fundamental biogeochemical processes and management implications

2004 ◽  
Vol 55 (1) ◽  
pp. 67 ◽  
Author(s):  
Ian T. Webster ◽  
Graham P. Harris
Keyword(s):  
Coastal Lagoon ◽  
Nutrient Loading ◽  
Anthropogenic Impacts ◽  
Coastal Lagoons ◽  
Alternative Stable States ◽  
Nitrogen Loading ◽  
Biogeochemical Model ◽  
Nutrient Loads ◽  
Stable States ◽  
Flushing Rate

This paper presents a biogeochemical model of a coastal lagoon intended to be representative of lagoons occurring along the south-east and south-west coasts of Australia. Many of these lagoons are threatened by increased nutrient loads because of land use change, by alterations to their freshwater inflows and by modification to their tidal flushing regimens. The model simulates the biogeochemical response of the lagoon to nutrient (nitrogen) loading and includes nutrient transformation processes in the sediments, as well as in the water column. The paper focuses on the response of primary producers to increasing and decreasing nutrient loads and how the response is altered by changes in the flushing rate of the lagoon with the sea. In common with lakes, the modelled lagoon exhibits alternative stable states representing macrophyte or phytoplankton dominance depending on nutrient loading and history. A third state representing severe degradation occurs when denitrification shuts down. A characteristic of Australian coastal lagoon systems is that, due to highly sporadic rainfall patterns, nutrient inflows are dominated by intermittent extreme events. The modelling demonstrates that such a loading regimen may be expected to generally increase the vulnerability of the lagoon to increasing nutrient loads. The results of the analysis presented are pertinent to several questions raised by coastal managers, such as what are the expected benefits of improving flushing by dredging and what are the consequences of altering the timing and magnitudes of the loads reaching the lagoons?

Fire Feedbacks with Vegetation and Alternative Stable States

2009 ◽  
Vol 18 (1) ◽  
pp. 159-173 ◽  
Author(s):  
Brian Beckage ◽  
Chris Ellingwood ◽  
Keyword(s):  
Alternative Stable States ◽  
Stable States ◽  
Fire Feedbacks

Water Quality Trends in Hamilton Harbour: 1987 to 1995

1996 ◽  
Vol 31 (3) ◽  
pp. 473-484 ◽  
Author(s):  
Murray N. Charlton ◽  
Robin Le Sage
Keyword(s):  
Algal Blooms ◽  
Action Plan ◽  
Secchi Depth ◽  
Water Clarity ◽  
Nutrient Loads ◽  
Hamilton Harbour ◽  
Near Shore ◽  
The Media ◽  
Park Area ◽  
Water Quality Trends

Abstract A series of water samples and Secchi depth measurements were conducted in Hamilton Harbour between 1987 and 1995. The data indicate little recent improvement in the harbour generally. Detection of real improvements may require high frequency sampling and a more extensive sample grid once a cause for improvement is in place. Some measures, such as chlorophyll and Secchi depth, approach RAP initial goals sometimes during recent years, but algal blooms still occur, which prevent attainment of satisfactory average conditions. The cause of aesthetic improvements in water clarity reported in the media was investigated with sampling along an inshore-offshore transect and intense Secchi measurements in the LaSalle Park area. The data are consistent with a transient clarifying effect of zebra mussels on structures near shore. The need to reduce nutrient loads as recommended in the Remedial Action Plan continues.

Selection of water source for water transfer based on algal growth potential to prevent algal blooms

2021 ◽  
Vol 103 ◽  
pp. 246-254
Author(s):  
Yongjun Song ◽  
Jing Qi ◽  
Le Deng ◽  
Yaohui Bai ◽  
Huijuan Liu ◽  
...  
Keyword(s):  
Algal Blooms ◽  
Algal Growth ◽  
Water Source ◽  
Water Transfer ◽  
Growth Potential ◽  
Algal Growth Potential ◽  
Selection Of

Are systems with strong underlying abiotic regimes more likely to exhibit alternative stable states?

Oikos ◽  
2005 ◽  
Vol 110 (2) ◽  
pp. 409-416 ◽  
Author(s):  
Raphael K. Didham ◽  
Corinne H. Watts ◽  
David A. Norton
Keyword(s):  
Alternative Stable States ◽  
Stable States
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