Environmental Dredging to Remove Fine-Grained, Organic-Rich Sediments and Reduce Inputs of Nitrogen and Phosphorus to a Subtropical Estuary

2018 ◽  
Vol 52 (4) ◽  
pp. 42-57 ◽  
Author(s):  
Austin L. Fox ◽  
John H. Trefry
Keyword(s):  
Water Depth ◽  
Interstitial Water ◽  
Indian River Lagoon ◽  
Benthic Fluxes ◽  
Nitrogen And Phosphorus ◽  
Overlying Water ◽  
Fine Grained ◽  
Total Inventory ◽  
Indian River ◽  
Subtropical Estuary

AbstractEnvironmental dredging of fine-grained, organic-rich sediments, locally referred to as Indian River Lagoon (IRL) muck, have been promoted as an integral part of restoring the IRL, Florida, to a healthy ecosystem. In Turkey Creek, a tributary to the IRL, ~300 metric tons of N and ~70 metric tons of P were removed with 160,000 m3 of wet muck and sand via environmental dredging during 2016 and 2017. Within the established dredged area, muck removal efficiency was ~63%; some areas were not dredged deep enough to remove all the muck. An additional 24,000 m3 of muck located outside the dredged area were not removed due to the presence of docks and seawalls. Prior to dredging, benthic fluxes of dissolved N (as ammonium) and P (as phosphate) from sediments to the overlying water, adjusted to 25°C, averaged 11 mg N/m2/h and 2.5 mg P/m2/h, respectively. Where IRL muck was removed to expose the underlying sand or mixed sand and muck, benthic fluxes of N and P were 20- to 30-fold lower after dredging. Subsequent disturbances, including Hurricane Matthew in October 2016, redistributed residual muck, leaving the dredged area 26% muck-free. Where muck was incompletely dredged or reintroduced by slumping, fluxes returned to predredging values within 6 months as equilibrium was reestablished between sediments and interstitial water. Dredging produced a 50% increase in water depth and basin volume with positive increases in salinity and the total inventory of dissolved oxygen. This deeper basin also serves as a sediment trap that will sequester future inputs of muck and mitigate future benthic fluxes of N and P by reducing the transport of muck into the IRL.

Environmental Factors Influencing Benthic Polychaete Distributions in a Subtropical Lagoon

2018 ◽  
Vol 52 (4) ◽  
pp. 58-74
Author(s):  
Anthony Cox ◽  
Daniel Hope ◽  
M. Angelica Zamora-Duran ◽  
Kevin B. Johnson
Keyword(s):  
Indian River Lagoon ◽  
Nutrient Inputs ◽  
Polychaete Species ◽  
Fine Grained ◽  
Principle Components Analysis ◽  
Indian River ◽  
Components Analysis ◽  
Benthic Sediments ◽  
Elevated Water ◽  
Definition Of

AbstractFine-grained organic-rich sediments (FGORS) in the Indian River Lagoon (IRL), Florida, sometimes called “muck,” contain elevated water, silt-clay, and organic matter contents and are abundant as a result of anthropogenic nutrient inputs. Many polychaetes inhabit the benthic sediments of estuaries and tolerate various degrees of FGORS. FGORS composition can be variable, and its effects on infaunal life such as polychaetes may depend upon concentration and composition. The IRL Cox Muck Index (CMI) is proposed as a mechanism for assigning a single value to the complex composition of muck and found to be a useful tool for summary and comparison. CMI has negative correlations with polychaete density (R2 = 0.2, p < 0.001), richness (R2 = 0.57, p < 0.001), and diversity (R2 = 0.55, p < 0.001) based on multiple regression of principle components (PCs) derived from principle components analysis (PCA). Sediment with CMI of <1 fails to meet the definition of IRL muck in at least one parameter and is assumed capable of sustaining some metazoan life. The CMI range of 0.1‐0.2 supports the most robust polychaete community. The polychaete species Diopatra cuprea, Glycera americana, Alitta succinea, and Pectinaria gouldii persisted in the IRL above 0.6 CMI. An environmental dredging project removed muck sediments midway through this study and polychaete recovery following dredging was monitored. At one site, an area of Turkey Creek with abundant muck, the CMI was significantly reduced from 1.4 to 0.8 (p < 0.001). The developing polychaete community at these stations included G. americana and A. succinea. At the end of the study, there were increases in overall polychaete community density, richness, and diversity to 1,000 m−2, S = 3, H = 0.55, respectively.

scholarly journals Mesozooplankton Community Dynamics and Grazing Potential Across Algal Bloom Cycles in a Subtropical Estuary

2021 ◽  
Vol 8 ◽  
Author(s):  
L. Holly Sweat ◽  
Hunter Alexander ◽  
Edward J. Phlips ◽  
Kevin B. Johnson
Keyword(s):  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Community Dynamics ◽  
Algal Bloom ◽  
Indian River Lagoon ◽  
Environmental Data ◽  
Brown Tide ◽  
Mesozooplankton Community ◽  
Indian River ◽  
Subtropical Estuary

Mesozooplankton, as abundant grazers of microalgae in coastal systems, have the potential to prevent or mitigate harmful algal blooms (HABs) and their effects. The Indian River Lagoon (IRL) is a subtropical estuary in eastern Florida (United States) where repeated blooms, dominated by the toxic dinoflagellate Pyrodinium bahamense, the brown tide species Aureoumbra lagunensis, pico/nano planktonic cyanobacteria and other nano-eukaryotes, have highlighted the need to better understand fluctuations in the grazing potential of mesozooplankton populations across bloom cycles. Mesozooplankton and abiotic environmental data were collected at five sites in the northern IRL system at 6-week intervals from November 2013 through June 2016. A total of 107 taxa from 14 phyla were detected. Communities varied across sites, dates and between bloom and non-bloom periods, with densities up to 338 individuals L–1. Eight taxa comprising 85–94% of the total population at each site were identified as primary potential grazers, including barnacle nauplii, cladocerans, adult copepods, gastropod veligers, larvaceans, and polychaete metatrochophores. Although abundant, the estimated grazing potential of the primary taxa, calculated from their measured densities and previously published grazing rates, suggest that mesozooplankton lack the capacity to suppress phytoplankton once they reach bloom levels. These findings illustrate the utility of monitoring data and underscore the importance of systematically evaluating algal bloom controls with a consideration for the dynamic conditions of each unique ecosystem.

scholarly journals Determination of Water Quality Characteristics and Nutrient Exchange Flux at the Sediment–Water Interface of the Yitong River in Changchun City, China

Water ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 3555
Author(s):  
Ke Zhao ◽  
Hang Fu ◽  
Qian Wang ◽  
Hai Lu
Keyword(s):  
Water Quality ◽  
Interstitial Water ◽  
Diffusion Flux ◽  
Pollution Index ◽  
Ammonia Nitrogen ◽  
Water Interface ◽  
Nitrogen And Phosphorus ◽  
Overlying Water ◽  
Nitrogen Pollutants ◽  
Exchange Flux

In this paper, the characteristics of water pollution in Yitong River were analyzed by the comprehensive pollution index method. Combined with the pore water concentration gradient method and Fick’s first law, the release characteristics of nutrients at the sediment–water interface of Yitong River (Jilin Province, China) were studied. The results showed that the distribution trend of nitrogen and phosphorus content in the overlying and interstitial water of the Yitong River was the same, and the highest values appeared at the S3 and S5 points in the urban section. The water quality was mainly affected by nitrogen pollutants in domestic sewage. The evaluation results of the water quality comprehensive pollution index showed that the pollution degree of interstitial water in urban areas was much higher than that of the overlying water, and the endogenous nitrogen and phosphorus pollutants had the risk of diffusion to the overlying water. The exchange flux analysis of ammonia nitrogen (NH4+-N), total dissolved nitrogen (TDN), and total dissolved phosphorus (TDP) in water showed that the diffusion flux of NH4+-N ranged from 0.03 to 6.52 mg·(m2·d)−1, and the sediment was the “source” of ammonia nitrogen pollutants. The range of TDN diffusion flux was −1.57 to 11.6 mg·(m2·d) −1, and the difference between points was large. The sediment was both the “source” and “sink” of nitrogen pollutants. The range of TDP diffusion flux was −0.05 to 0.22 mg·(m2·d) −1. Except for point S8, the TDP diffused from sediment into the water body. Among all the sampling points, the diffusion fluxes of NH4+-N, TDN, and TDP at the S3 point were the largest, the release rate of endogenous pollutants was the most rapid, and the pollution to the water quality was the most serious. The results are of great significance to the exchange flux of nutrients at the sediment–water interface of rivers and the prevention and control of water eutrophication. It also provides a reference for the study of nutrient exchange flux at the sediment–water interface of rivers and other surface water bodies worldwide.

scholarly journals Dynamic Interception Effect of Internal and External Nitrogen and Phosphorus Migration of Ecological Ditches

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2553
Author(s):  
Yuyang Liu ◽  
Songmin Li ◽  
Xiaoling Wang ◽  
Yuchen An ◽  
Ruonan Wang
Keyword(s):  
Microbial Communities ◽  
Concentration Gradient ◽  
Interstitial Water ◽  
Nitrogen And Phosphorus ◽  
Overlying Water ◽  
Absorption Function ◽  
Effective Measure ◽  
Ammonium N ◽  
The Matrix ◽  
Bottom Mud

The “ecological ditch” (eco-ditch) is an effective measure used to alleviate agricultural non-point-source pollution. However, information is lacking about the continuous transport characteristics of internal and external nitrogen and phosphorus in the interstitial water of the bottom mud of these ditches and overlying water under dynamic continuous inflow conditions. Understanding of the effect of matrix dams and microbial communities inside eco-ditches on the continuous transport characteristics of the N and P therein needs to be improved. To determine the interception effects of eco-ditches on the transfer of endogenous and exogenous N and P, an eco-ditch combining plants and a matrix dam was built to explore the transport distribution characteristics of N and P in the intermittent water and overlying water in the bottom of the eco-ditch and in the bottom of the soil ditch. We compared and analyzed the composition characteristics of the microbiological communities along the ecological and soil ditches. The research results showed that: (1) The concentration gradient between the interstitial water and the overlying water in the soil ditch is the main reason for the transport and diffusion of pollutants. However, in eco-ditches, the absorption function of plant roots and the differences between the structures of the microbial communities destroy the correlation of this concentration gradient diffusion, especially the effect on ammonium N; (2) a large number of mycelia adhere to the surface of the matrix dam in an eco-ditch, and are conducive to the adsorption and purification of pollutants in the water; (3) Proteobacteria, Chloroflexi, Actinomycetes, and Acidobacteria were the main bacterial groups in the ditches. The aquatic plants in the eco-ditch changed the microenvironment of the sediment, and both the microbial diversity and abundance along the eco-ditch were higher than in the soil ditch.

Contemporary issues in watershed and water quality modeling for eutrophication control

1998 ◽  
Vol 37 (3) ◽  
pp. 93-102
Author(s):  
Robert V. Thomann ◽  
Lewis C. Linker
Keyword(s):  
Coastal Waters ◽  
Water Quality Modeling ◽  
Significant Decline ◽  
Suspension Feeding ◽  
Watershed Model ◽  
Nitrogen And Phosphorus ◽  
Overlying Water ◽  
Chesapeake Bay Watershed ◽  
Eutrophication Control ◽  
Quality Modeling

Three issues are discussed: controllability of nonpoint nutrient loadings using watershed models; the sometimes counter intuitive results from eutrophication models from nutrient controls for coastal waters; and the potential significant interaction of improvement in habitat for suspension feeding bivalves. For the Chesapeake Bay watershed model, and for Limit of Technology (LOT) controls, a 16% and 45% reduction in nitrogen and phosphorus, respectively, is calculated. For the Bay, it is concluded that removal of phosphorus only is less effective than nitrogen in improving bottom water DO because of differential transport of nitrogen downstream. For the Delaware estuary, a significant decline in phytoplankton chlorophyll has been observed in the absence of any nutrient controls but in the presence of improved DO. A simple model is offered that hypothesized an increase in benthic bivalve filtration of overlying water as a result of improvement in DO.

Dynamics of microcystins and saxitoxin in the Indian River Lagoon, Florida

Harmful Algae ◽  
2021 ◽  
Vol 103 ◽  
pp. 102012
Author(s):  
Abdiel E. Laureano-Rosario ◽  
Malcolm McFarland ◽  
David J. Bradshaw ◽  
Jackie Metz ◽  
Rachel A. Brewton ◽  
...  
Keyword(s):  
Indian River Lagoon ◽  
Indian River
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