Effects of Nutrient Enrichment and Flood Frequency on Periphyton Biomass in Northern Ozark Streams

1992 ◽  
Vol 49 (6) ◽  
pp. 1198-1205 ◽  
Author(s):  
Kirk Lohman ◽  
John R. Jones ◽  
Bruce D. Perkins
Keyword(s):  
Nutrient Enrichment ◽  
Maximum Level ◽  
Nutrient Supply ◽  
Flood Frequency ◽  
Nutrient Concentrations ◽  
Flood Events ◽  
Chl A ◽  
Catastrophic Flood ◽  
Periphyton Biomass ◽  
Over Time

Ambient nutrient concentrations (TN and TP) and periphyton biomass (Chl a) were measured every 2 wk during March–November in 1985 and 1986 at 22 sites on 12 streams in the northern Ozarks, Missouri. Benthic Chl a was positively correlated in both years with log TN (R2 = 0.58, 0.60) and with log TP (R2 = 0.47, 0.60). When sites were grouped by the degree of enrichment and plotted over time, benthic Chl a decreased at all sites after flood events, but rebounded more rapidly at highly enriched sites. Differences in recovery following flooding were most obvious in fall 1986, when both high and moderately enriched sites exhibited similar biomass accrual patterns, reaching mean benthic Chl a of 397.4 and 321.1 mg∙m−2, respectively, within 42 d after a catastrophic flood. In contrast, average benthic Chl a at nutrient-poor sites reached a maximum level of 76.8 mg∙m−2 within 28 d after flooding, suggesting that maximum standing crops are influenced by both nutrient supply and the length of the flood-free period.

scholarly journals Patterns in nutrient limitation and chlorophyll a along an anthropogenic eutrophication gradient in French Mediterranean coastal lagoons

2010 ◽  
Vol 67 (4) ◽  
pp. 743-753 ◽  
Author(s):  
Philippe Souchu ◽  
Béatrice Bec ◽  
Val H. Smith ◽  
Thierry Laugier ◽  
Annie Fiandrino ◽  
...  
Keyword(s):  
Nutrient Limitation ◽  
Chlorophyll A ◽  
Nutrient Enrichment ◽  
Coastal Waters ◽  
Coastal Lagoons ◽  
Inorganic Nitrogen ◽  
Nutrient Concentrations ◽  
Chl A ◽  
Mediterranean Lagoons ◽  
Ecosystem Comparison

A cross-ecosystem comparison of data obtained from 20 French Mediterranean lagoons with contrasting eutrophication status provided the basis for investigating the variables that best predict chlorophyll a (Chl a) concentrations and nutrient limitation of phytoplankton biomass along a strong nutrient enrichment gradient. Summer concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) comprised only a small fraction of total nitrogen (TN) and total phosphorus (TP). On the basis of inorganic nutrient concentrations, the most oligotrophic lagoons appeared to be phosphorus-limited, with a tendency towards the development of nitrogen limitation as eutrophication increased, as evidenced by decreasing DIN:DIP ratios. A weak but significantly positive relationship was found between dissolved silicate (DSi) and Chl a, reflecting DSi accumulation in the water column along the trophic state gradient and implying a progressive shift away from potential Si limitation of phytoplankton growth. Observed concentrations of Chl a were far better explained by TN and TP than by DIN and DIP concentrations, suggesting that a total nutrient based approach is likely to be the most appropriate for managing eutrophication in Mediterranean lagoons and other coastal waters. These results give credence to the idea that marine and freshwater environments respond in a similar fashion to nutrient enrichment.

scholarly journals Root Medium Chemical Properties

1998 ◽  
Vol 8 (4) ◽  
pp. 486-494 ◽  
Author(s):  
William R. Argo
Keyword(s):  
Irrigation Water ◽  
Cation Exchange Capacity ◽  
Nutrient Management ◽  
Chemical Properties ◽  
Nutrient Supply ◽  
Exchange Capacity ◽  
Water Soluble ◽  
Nutrient Concentrations ◽  
Medium Ph ◽  
Over Time

Maintaining medium pH and nutrient concentrations at levels acceptable for growth are important for producing vigorous transplants in the shortest time. Medium chemical properties, such as cation-exchange capacity, aeration, liming materials, preplant fertilizer, irrigation-water sources, water-soluble fertilizers, and plant species, interact to affect medium pH and nutrient management. However, these chemical properties do not affect medium pH or the nutrient supply simultaneously or with equal intensity. The objective of this review is to consider key chemical properties of container media and their affects on pH and nutrient management initially and over time.

Impact of Catchment Urbanisation on Lake Macquarie (Australia)

1989 ◽  
Vol 21 (2) ◽  
pp. 205-210 ◽  
Author(s):  
B. L. Simmons ◽  
S. L. Trengove
Keyword(s):  
Nutrient Enrichment ◽  
Benthic Algae ◽  
Water Clarity ◽  
Nutrient Concentrations ◽  
Lake Area ◽  
Seagrass Beds ◽  
Coastal Lake ◽  
Aesthetic Quality ◽  
Wastewater Disposal ◽  
Coastal Lakes

Increasing urbanisation of coastal areas is leading to impacts on coastal lakes which decrease their amenity for recreation and tourism. Runoff and wastewater discharge cause siltation, impact seagrass beds and change the characteristics of open waters, affecting boating, swimming, fishing and the aesthetic quality of the locale. Management of urban development and wastewater disposal is required to minimise sedimentation and nutrient enrichment. This could include development restrictions, runoff controls and a strategy for wastewater treatment and discharge. The catchment of Lake Macquarie, a marine coastal lake, has been progressively urbanised since 1945. Urbanisation, through increased stormwater runoff and point source discharges, has caused a major impact on the lake in terms of sedimentation and nutrient enrichment. Losses of lake area and navigable waters have occurred. Accompanying problems include changes in the distribution of seagrass beds and nuisance growths of benthic algae. Since the 1950's, dry weather nutrient concentrations have increased and mean water clarity has decreased. Severe problems, as observed in other New South Wales coastal lakes, for example benthic algae in Lake Illawarra and Tuggerah Lakes, have not yet developed. Because of the lead time taken to implement policies and controls, trends should be identified and policies developed now so as to avoid nutrient buildup and development of sustained problems.

Practical Applications of Bed Scour Calculations: Two Case Studies

2014 ◽  
Author(s):  
Leif M. Burge ◽  
Laurence Chaput-Desrochers ◽  
Richard Guthrie
Keyword(s):  
Case Studies ◽  
Flood Frequency ◽  
Flood Frequency Analysis ◽  
Accurate Estimation ◽  
Pool Depth ◽  
Regional Flood Frequency Analysis ◽  
Channel Degradation ◽  
Design Depth ◽  
Bed Scour ◽  
Over Time

Pipelines can be exposed at water crossings where rivers lower the channel bed. Channel bed scour may cause damage to linear infrastructure such as pipelines by exposing the pipe to the flow of water and sediment. Accurate estimation of depth of scour is therefore critical in limiting damage to infrastructure. Channel bed scour has three main components: (1) general scour, (2) bed degradation, and (3) pool depth. General scour is the temporary lowering of the channel bed during a flood event. Channel bed degradation is the systematic lowering of a channel bed over time. Pool depth is depth of pools below the general bed elevation and includes the relocation of pools that result from river dynamics. Channel degradation is assessed in the field using indicators of channel incision such as channel bed armoring and bank characteristics, through the analysis of long profiles and sediment transport modelling. Pool depth is assessed using long profiles and channel movement over time. The catastrophic nature of bed lowering due to general scour requires a different assessment. A design depth of cover is based on analysis of depth of scour for a given return period (eg. 100-years). There are three main steps to predict general scour: (1) regional flood frequency analysis, (2) estimation of hydraulic variables, and (3) scour depth modelling. Typically, four scour models are employed: Lacey (1930), Blench (1969), Neill (1973), and Zeller (1981), with the average or maximum value used for design depth. We provide herein case studies for potential scour for pipeline water crossings at the Little Smoky River and Joachim Creek, AB. Using the four models above, and an analysis of channel degradation and pool depth, the recommended minimum depth of cover of 0.75 m and 0.142 m, respectively, were prescribed. Variability between scour models is large. The general scour model results varied from 0.45 m and 0.75 m for the Little Smoky River and 0.16 m to 0.51 m for Joachim Creek. While these models are more than 30 years old and do not adequately account for factors such as sediment mobility, they nevertheless do provide usable answers and should form part of the usual toolbox in water crossing scour calculations.

scholarly journals Trouble in Paradise? A comparison of 1953 and 2005 benthonic foraminiferal seafloor assemblages at the Ibis Field, offshore eastern Trinidad, West Indies

2006 ◽  
Vol 25 (2) ◽  
pp. 157-164 ◽  
Author(s):  
Brent Wilson
Keyword(s):  
Relative Abundance ◽  
Nutrient Enrichment ◽  
Abundant Species ◽  
Nutrient Supply ◽  
South American ◽  
Sufficient Time ◽  
Phytoplankton Primary Production ◽  
Environmental Perturbations ◽  
Run Off ◽  
Shrimp Farms

Abstract. Foraminiferal communities are not static, but change in response to environmental perturbations. Given sufficient time, the change will be recorded in the total (live+dead) seafloor assemblage, from which valuable information regarding environmental trends can be obtained by re-sampling assemblages at the decadal scale.The seafloor assemblage in the 5 km × 6 km Ibis Field, off southeast Trinidad, first surveyed in 1953, was re-examined in 2005. The fauna had changed markedly between the surveys. Overall increases in the proportional abundances of Uvigerina subperegrina, Ammonia pauciloculata/Rolhausenia rolhauseni and Pseudononion atlanticum indicate an increase in nutrient supply that apparently killed off Cibicidoides pseudoungerianus and Miliolinella subrotunda, and reduced the relative abundance of Hanzawaia concentrica, but did not affect the relative abundance of Cancris sagrai. As shown by similar 1953 and 2005 planktonic/benthonic foraminiferal ratios, the increased nutrient supply impacted on both surface and bottom waters.Of the six most abundant species in 2005, five showed the same general biogeographical distributions within the field in 1953 and 2005. However, whereas the proportional abundance of Uvigerina subperegrina in 1953 increased southwards, in 2005 it increased northwards.Trinidad cannot be the source for the nutrient enrichment: the island lies down-current from the Ibis Field. Sources must therefore be sought up-current and to the southeast, in the Amazon, Essequibo and Orinoco river basins, or along the South American shoreline. It is speculated that the nutrient enrichment may be a consequence of increased phytoplankton primary production associated with nitrogen-rich run-off from South American sugarcane plantations, or from flushing of organic carbon from poorly regulated sewage systems or shrimp farms in South America.

scholarly journals Analysing flood history and simulating the nature of future floods using Gumbel method and Log-Pearson Type III: the case of the Mayurakshi River Basin, India

2021 ◽  
Vol 19 (1) ◽  
pp. 43-69
Author(s):  
Aznarul Islam ◽  
Biplab Sarkar
Keyword(s):  
River Basin ◽  
Low Frequency ◽  
Flood Frequency ◽  
Flood Events ◽  
Significance Level ◽  
Type Iii ◽  
Return Probability ◽  
Pearson Type ◽  
Anderson Darling ◽  
Normally Distributed

AbstractFloods of the Mayurakshi River Basin (MRB) have been historically documented since 1860. The high magnitude, low-frequency flood events have drastically changed to low magnitude, high-frequency flood events in the post-dam period, especially after the 1950s, when the major civil structures (Massanjore dam, Tilpara barrage, Brahmani barrage, Deucha barrage, and Bakreshwar weir) were constructed in the MRB. The present study intends to find out the nature of flood frequency using the extreme value method of Gumbel and Log-Pearson type III (LP-III). The results show that the highest flood magnitude (11,327 m3 s−1) was observed during 1957–2009 for the Tilpara barrage with a return probability of 1.85% and the lowest (708 m3 s−1) recorded by the Bakreshwar weir during 1956–77 with a return probability of 4.55%. In the present endeavour, we have computed the predicted discharge for the different return periods, like 2, 5, 10, 25, 50,100, and 200 years. The quantile-quantile plot shows that the expected discharge calculated using LP-III is more normally distributed than that of Gumbel. Moreover, Kolmogorov–Smirnov (KS) test, Anderson–Darling (AD), and x2 distribution show that LP-III distribution is more normally distributed than the Gumbel at 0.01 significance level, implying its greater reliability and acceptance in the flood simulation of the MRB.

scholarly journals Spatiotemporal variation in global floods with different affected areas and the contribution of influencing factors to flood-induced mortality (1985–2019)

2022 ◽  
Author(s):  
Tian Liu ◽  
Peijun Shi ◽  
Jian Fang
Keyword(s):  
Influencing Factors ◽  
Large Scale ◽  
Human Life ◽  
Flood Frequency ◽  
Spatiotemporal Variation ◽  
Mountainous Area ◽  
Flood Events ◽  
Protection Measures ◽  
Flood Duration ◽  
Level Ii

AbstractFloods are great threats to human life and property. Extensive research has investigated the spatiotemporal variation in flood occurrence, while few have studied the heterogeneity in global flood events of different sizes, which may require different coping strategies and risk reduction policies. In this study, we analysed the spatiotemporal patterns of global flood events with different affected areas (classified in three levels) during 1985–2019 and examined the contribution of different influencing factors to flood-induced mortality using Geodetector. The results show that (1) the increase in global flood frequency was mainly caused by Level II and Level III floods, and the average area affected by flood events has been increasing yearly since 1985. (2) In America and Africa, the frequency of Level III floods has increased monotonically. At the same time, the frequency of Level I floods in Europe and Level II floods in Asia has increased significantly. (3) For Europe and Asia, most of the deaths occurred with Level II floods; while for America and Africa, Level III floods caused the most mortality. (4) The top three factors contributing to the spatial heterogeneity in flood-induced mortality were the affected population, GDP per capita and flood duration. The contribution of each factor varied among the different types of floods. Topographic factors (percentage of mountainous area) magnified flood-induced mortality during extreme events with heavy rainfall, especially for Level III floods. The heterogeneity in flood frequency and flood-induced mortality indicates that flood protection measures should be more targeted. In addition, the increase in large-scale floods (Level III) highlights the need for transregional cooperation in flood risk management.

Towards a better understanding of river dynamics in semi-urbanised areas: a machine learning analysis on time-series satellite images

2021 ◽  
Author(s):  
Alessio Cislaghi ◽  
Paolo Fogliata ◽  
Emanuele Morlotti ◽  
Gian Battista Bischetti
Keyword(s):  
Machine Learning ◽  
Time Series ◽  
Riparian Vegetation ◽  
Satellite Images ◽  
River Management ◽  
Machine Learning Algorithms ◽  
Flood Events ◽  
River Dynamics ◽  
Clear Cutting ◽  
Over Time

<p>River channels and floodplains have been highly modified over the last 70 years to mitigate flood risk and to gain lands for agricultural activities, settlements and soft infrastructures (e.g., cycle paths). River engineering measures simplified the geomorphologic complexity of river system, usually from braided or wandering channels to highly-confined single-thread channel. Meanwhile, rivers naturally adjust and self-organise the geomorphologic function as response of all the disturbances (e.g., flood events, river-bed degradation, narrowing, control works) altering sediment and water transfer, exacerbating bank erosion processes and streambank failures, and exposing bare sediment that can be subsequently colonized by pioneer species. In this context, river management has to address river dynamics planning sustainable practices with the aim to combine hydraulic safety, river functionality, and ecological/environmental quality. These actions require the detection of river processes by monitoring the geomorphological changes over time, both over the active riverbank and the close floodplains. Thus, remote sensing technology combined with machine learning algorithms offers a viable decision-making instrument (Piégay et al., 2020).</p><p>This study proposes a procedure that consists in applying image segmentation and classification algorithms (i.e., Random Forest and dendrogram-based method) over time-series high resolution RGB-NIR satellite-images, to identify the fluvial forms (bars and islands), the vegetation patches and the active riverbed. The study focuses on three different reaches of Oglio River (Valcamonica, North Italy), representative of the most common geomorphic changes in Alpine rivers.</p><p>The results clearly show the temporal evolution/dynamics of vegetated and non-vegetated bars and islands, as consequence of human and natural disturbances (flood events, riparian vegetation clear-cutting, and bank-protection works). Moreover, the procedure allows to distinguish two stages of riparian vegetation (i.e., pioneer and mature vegetated areas) and to quantify the timing of colonization and growth. Finally, the study proposes a practical application of the described methodology for river managers indicating which river management activity (including timing, intensity and economic costs) is more appropriate and sustainable for each studied reach.</p><p> </p><p>References: Piégay, H., Arnaud, F., Belletti, B., Bertrand, M., Bizzi, S., Carbonneau, P., Dufour, S., Liébault, F., Ruiz‐Villanueva, V. and Slater, L.: Remotely sensed rivers in the Anthropocene: state of the art and prospects, Earth Surf. Process. Landf., 45(1), 157–188, https://doi.org/10.1002/esp.4787, 2020.</p>

scholarly journals Tidal and seasonal forcing of dissolved nutrient fluxes in reef communities

2019 ◽  
Vol 16 (9) ◽  
pp. 1921-1935 ◽  
Author(s):  
Renee K. Gruber ◽  
Ryan J. Lowe ◽  
James L. Falter
Keyword(s):  
Mass Transfer ◽  
Nutrient Supply ◽  
Tidal Range ◽  
Nutrient Concentrations ◽  
Nutrient Fluxes ◽  
Flow Measurements ◽  
Uptake Rates ◽  
Reef Communities ◽  
Flow Speeds ◽  
Strong Control

Abstract. Benthic fluxes of dissolved nutrients in reef communities are controlled by oceanographic forcing, including local hydrodynamics and seasonal changes in oceanic nutrient supply. Up to a third of reefs worldwide can be characterized as having circulation that is predominantly tidally forced, yet almost all previous research on reef nutrient fluxes has focused on systems with wave-driven circulation. Fluxes of dissolved nitrogen and phosphorus were measured on a strongly tide-dominated reef platform with a spring tidal range exceeding 8 m. Nutrient fluxes were estimated using a one-dimensional control volume approach, combining flow measurements with modified Eulerian sampling of waters traversing the reef. Measured fluxes were compared to theoretical mass-transfer-limited uptake rates derived from flow speeds. Reef communities released 2.3 mmol m−2 d−1 of nitrate, potentially derived from the remineralization of phytoplankton and dissolved organic nitrogen. Nutrient concentrations and flow speeds varied between the major benthic communities (coral reef and seagrass), resulting in spatial variability in estimated nitrate uptake rates. Rapid changes in flow speed and water depth are key characteristics of tide-dominated reefs, which caused mass-transfer-limited nutrient uptake rates to vary by an order of magnitude on timescales of ∼ minutes–hours. Seasonal nutrient supply was also a strong control on reef mass-transfer-limited uptake rates, and increases in offshore dissolved inorganic nitrogen concentrations during the wet season caused an estimated twofold increase in uptake.

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