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Oscar Iribarne - One of the best experts on this subject based on the ideXlab platform.
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Effects of Spartina Wrack on Surface-Active Arthropod Assemblage Under Different Environmental Contexts in Southwest Atlantic Salt Marshes
Estuaries and Coasts, 2019Co-Authors: Diana I Montemayor, Alejandro D. Canepuccia, Juan Farina, Mariana Addino, Macarena Valiñas, Oscar IribarneAbstract:Large amounts of tidally accumulated detritus (i.e., wrack) are an important source of disturbance affecting different abiotic and biotic characteristics in Salt Marshes, which could in turn affect the macrofauna assemblage. The purpose of this study was to evaluate the importance of wrack disturbance in Southwest Atlantic (SWA) Salt Marshes and its effects on the surface-active arthropod assemblage under different environmental contexts. By sampling the most important SWA Salt Marshes (from 36° 19′ S to 41° 01′ S), we found that wrack is a widespread disturbance in this region, present in all the Salt Marshes and periods sampled. However, the biomass and type of wrack ( Spartina alterniflora vs. S. densiflora ) vary according to the species that dominates each Salt marsh. At two of these sites (Bahia Blanca (BB), 38° 59′ S and San Clemente (SC), 36° 19′ S), chosen because they represent the two Salt marsh types in the SWA region (dominated by Spartina alterniflora or S. densiflora ), we performed a field experiment by manipulating the presence and absence of wrack and conducting field samplings of sediment organic matter content and water content. We found that wrack affects surface arthropod assemblage but that this effect was not consistent for the different Salt Marshes: in BB, it changed the surface-active arthropod assemblage (shifted towards more detritivorous taxa) and increased the number of total individuals but had no effect on the number of species or diversity. At SC, wrack had no effect on any of the parameters evaluated. We suggest that the type of wrack in each Salt marsh modulates the amount of organic matter content in the sediment: BB had wrack of better nutritional quality (dominated by S. alterniflora ) and in turn had greater organic matter content in the sediment of wrack zones than in no-wrack zones, while in SC (dominated by S. densiflora ), there is no differences between the two zones. We also suggest that depending on the original surface-active arthropod assemblage, those modifications will either favor (BB) or not favor (SC) wrack colonization by the surface-active arthropod assemblage. Moreover, considering that SWA wrack has different compositions and that the biomass differs among the different Salt Marshes, we expect wrack effects in the SWA, and probably in other regions, to be site-specific.
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Influence of Grasshopper Herbivory on Nitrogen Cycling in Northern Gulf of Mexico Black Needlerush Salt Marshes
Estuaries and Coasts, 2017Co-Authors: Diana I Montemayor, Eric L Sparks, Oscar Iribarne, Just CebrianAbstract:Herbivory is a common process in Salt Marshes. However, the direct impact of marsh herbivory on nutrient cycling in this ecosystem is poorly understood. Using a 15N enrichment mesocosm study, we quantified nitrogen (N) cycling in sediment and plants of black needlerush (Juncus roemerianus) Salt Marshes, facilitated by litter decomposition and litter plus grasshopper feces decomposition. We found 15 times more 15N recovery in sediment with grasshopper herbivory compared to sediment with no grasshopper herbivory. In plants, even though we found three times and a half larger 15N recovery with grasshopper herbivory, we did not find significant differences. Thus, herbivory can enhance N cycling in black needlerush Salt Marshes sediments and elevate the role of these Salt Marshes as nutrient sinks.
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crab bioturbation and herbivory may account for variability in carbon sequestration and stocks in south west atlantic Salt Marshes
Frontiers in Marine Science, 2016Co-Authors: Paulina Martinetto, Diana I Montemayor, Juan Alberti, Cesar Serra Bonifacio Costa, Oscar IribarneAbstract:Coastal vegetation plays an important role for climate change mitigation. Compared with terrestrial ecosystems, coastal vegetation shows higher rates of atmospheric CO2 uptake and a more efficient retention of carbon (C) in sediments. Salt Marshes present the highest values as C binders, although a global estimation of these values is still pending due to regional gaps in the records predominantly from the southern hemisphere. There are no clear patterns or dominant processes with enough evidence to account for the observed variability, suggesting that context dependent processes are likely greatest influencers on C storage. Salt Marshes in the South West Atlantic (SWA) coast are densely populated by the intertidal burrowing and herbivore crab Neohelice (=Chasmagnathus) granulata. Many ecological processes related to C transformation occurring in these Salt Marshes are influenced by crab activities, either through bioturbation or via herbivory. We hypothesize that N. granulata could have a significant role in the capacity of SWA Salt Marshes to bind C. Reduction of plant biomass, increased aerobic decomposition in the sediment and facilitation of erosion are some of the multiple effects exerted by N. granulata that can directly and indirectly modify the capacity of Salt Marshes to bind C. Here, we compiled information available regarding C sequestration and accumulation in SWA coastal Salt Marshes and propose a hypothetical model including the mechanisms mediated by N. granulata that interfere the transformation paths of C in Salt Marshes. The data suggest that mechanisms that are top-down regulated, negatively affect C accumulation in the form of aboveground biomass especially in Salt Marshes dominated by Spartina alterniflora. While, mechanisms mediated by bioturbation can negatively (increasing oxygenation and thus facilitating aerobic degradation) affect as well as positively (increasing retention of macrodetritus) affect the accumulation of C, the latter being of greater magnitude in Spartina densiflora Salt Marshes.
Sergio Fagherazzi - One of the best experts on this subject based on the ideXlab platform.
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efficient tidal channel networks alleviate the drought induced die off of Salt Marshes implications for coastal restoration and management
Science of The Total Environment, 2020Co-Authors: Zezheng Liu, Sergio Fagherazzi, Chengjie Xie, Xiaojun She, Baoshan CuiAbstract:Massive die-off in Salt Marshes is one of the most common examples of widespread degradation in marine and coastal ecosystems. In Salt Marshes, tidal channel networks facilitate the exchange of water, nutrients, sediments and biota with the open marine environments. However, quantitative analyses of the role of channel networks in alleviating vegetation die-off in Salt Marshes are scarce. Here we quantified the spatial-temporal development of marsh vegetation die-off in the northern Liaodong Bay by analyzing aerial images before, during, and after a drought (from 2014 to 2018). We found that Suaeda salsa Marshes have recently experienced large-scale die-off. The extent of vegetation die-off increases with increasing distance from the channel network. Moreover, our results suggested that efficient tidal channel networks (high drainage density, low mean unchanneled path length) can mitigate die-off at the watershed scale. We presented possible abiotic & biotic processes in channel networks that explain this spatial dynamic. Our study highlights the importance of efficient tidal channel networks in mitigating die-off and enhancing the resistance of Marshes to droughts, and call for incorporating theses dynamics in coastal restoration and management.
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How waves shape Salt Marshes
Geology, 2014Co-Authors: Nicoletta Leonardi, Sergio FagherazziAbstract:We present high-resolution field measurements of five sites along the United States Atlantic Coast, and cellular automata simulations, to investigate the erosion of marsh boundaries by wave action. According to our analysis, when Salt Marshes are exposed to high wave energy conditions their boundaries erode uniformly. The resulting erosion events follow a Gaussian distribution, yielding a relatively smooth shoreline. On the contrary, when wind waves are weak and the local marsh resistance is strong, jagged marsh boundaries form. In this case, erosion episodes have a long-tailed frequency magnitude distribution with numerous low-magnitude events, but also high-magnitude episodes. The logarithmic frequency magnitude distribution suggests the emergence of a critical state for marsh boundaries, which would make the prediction of failure events impossible. Internal physical processes allowing Salt Marshes to reach this critical state are geotechnical and biological, and related to the nonhomogeneity of Salt Marshes whose material discontinuities act as stress raisers.
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Fluxes of water, sediments, and biogeochemical compounds in Salt Marshes
Ecological Processes, 2013Co-Authors: Sergio Fagherazzi, Patricia L Wiberg, Stijn Temmerman, Eric Struyf, Yong Zhao, Peter A RaymondAbstract:Tidal oscillations systematically flood Salt Marshes, transporting water, sediments, organic matter, and biogeochemical elements such as silica. Here we present a review of recent studies on these fluxes and their effects on both ecosystem functioning and morphological evolution of Salt Marshes. We reexamine a simplified model for the computation of water fluxes in Salt Marshes that captures the asymmetry in discharge between flood and ebb. We discuss the role of storm conditions on sediment fluxes both in tidal channels and on the marsh platform. We present recent methods and field instruments for the measurement of fluxes of organic matter. These methods will provide long-term data sets with fine temporal resolution that will help scientists to close the carbon budget in Salt Marshes. Finally, the main processes controlling fluxes of biogenic and dissolved silica in Salt Marshes are explained, with particular emphasis on the uptake by marsh macrophytes and diatoms.
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self organization of shallow basins in tidal flats and Salt Marshes
Journal of Geophysical Research, 2007Co-Authors: Andrea Defina, Sergio Fagherazzi, Luca Carniello, Luigi DalpaosAbstract:[1] Shallow tidal basins such as the Venice Lagoon, Italy, are often characterized by extensive tidal flats and Salt Marshes that lie within specific ranges of elevation. Tidal flats lie just below the mean sea level, approximately between −0.6 and −2.0 meters above the mean sea level (m a.m.s.l.), whereas Salt Marshes lie at an average elevation higher than mean sea level (i.e., between +0.1 and +0.5 m a.m.s.l.). Only a small fraction of the tidal basin area has elevations between −0.6 and +0.1 m a.m.s.l. This occurrence suggests that the morphodynamic processes responsible for sediment deposition and erosion produce either tidal flats or Salt Marshes but no landforms located in the above intermediate range of elevations. A conceptual model describing this evolutionary trend has recently been proposed. The model assumes that the bimodal distribution of bottom elevations stems from the characteristics of wave induced sediment resuspension and demonstrates that areas at intermediate elevations are inherently unstable and tend to become either tidal flats or Salt Marshes. In this work, the conceptual model is validated through comparison with numerical results obtained with a two-dimensional wind wave-tidal model applied to the Lagoon of Venice, Italy. Both the present and the 1901 bathymetries of the Venice Lagoon are used in the simulations and the obtained numerical results confirm the validity of the conceptual model. A new framework that explains the long-term evolution of shallow tidal basins based on the results presented herein is finally proposed and discussed.
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critical bifurcation of shallow microtidal landforms in tidal flats and Salt Marshes
Proceedings of the National Academy of Sciences of the United States of America, 2006Co-Authors: Sergio Fagherazzi, Luca Carniello, Luigi Dalpaos, Andrea DefinaAbstract:Shallow tidal basins are characterized by extensive tidal flats and Salt Marshes that lie within specific ranges of elevation, whereas intermediate elevations are less frequent in intertidal landscapes. Here we show that this bimodal distribution of elevations stems from the characteristics of wave-induced sediment resuspension and, in particular, from the reduction of maximum wave height caused by dissipative processes in shallow waters. The conceptual model presented herein is applied to the Venice Lagoon, Italy, and demonstrates that areas at intermediate elevations are inherently unstable and tend to become either tidal flats or Salt Marshes.
Kai Jensen - One of the best experts on this subject based on the ideXlab platform.
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Long-term invasion dynamics of Spartina increase vegetation diversity and geomorphological resistance of Salt Marshes against sea level rise
Biological Invasions, 2020Co-Authors: Dirk Granse, Sigrid Suchrow, Kai JensenAbstract:The cordgrass Spartina anglica C.E. Hubbard ( Poaceae ) is an invasive transformer in many Salt marsh ecosystems worldwide. Relatively little is known about the capacity of Spartina to accelerate Salt marsh succession and to protect Salt Marshes against sea level rise. We analyzed long-term changes in vegetation and elevation in mainland Salt Marshes of the European Wadden Sea in Schleswig-Holstein, Germany, to estimate the impact of non-native Spartina on the geomorphological resistance of Salt Marshes to sea level rise and on changes in species diversity. From 1989 to 2019, the Spartina -zone shifted and expanded upwards to elevations of the high marsh zone and Spartina increased in frequency in several Salt marsh vegetation communities. At sites where Spartina dominated the vegetation already three decades ago, elevation and species diversity increased with a higher rate compared to sites lacking Spartina . The median change rates reached for elevation MHT +8.6 versus +1.5 mm per year, for species richness +3 versus $$\pm$$ ± 0 species per three decades, and for evenness +0.04 versus −0.08 per three decades, regarding plots with versus without former Spartina dominance, respectively. Invasion of Salt Marshes by Spartina and its continued, long-term presence were associated with increased elevation and species diversity in the face of sea level rise.
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wave attenuation over coastal Salt Marshes under storm surge conditions
Nature Geoscience, 2014Co-Authors: Iris Moller, Matthias Kudella, Franziska Rupprecht, T Spencer, Maike Paul, Bregje K Van Wesenbeeck, Guido Wolters, Kai Jensen, Tjeerd J Bouma, Martin MirandalangeAbstract:Salt Marshes protect coastlines against waves. Wave flume experiments show that marsh vegetation causes substantial wave dissipation and prevents erosion of the underlying surface, even during extreme storm surge conditions.
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Wave attenuation over coastal Salt Marshes under storm surge conditions
Nature Geoscience, 2014Co-Authors: Iris Moller, Matthias Kudella, Franziska Rupprecht, T Spencer, Maike Paul, Bregje K Van Wesenbeeck, Guido Wolters, Kai Jensen, Tjeerd J Bouma, Martin Miranda-langeAbstract:Salt Marshes protect coastlines against waves. Wave flume experiments show that marsh vegetation causes substantial wave dissipation and prevents erosion of the underlying surface, even during extreme storm surge conditions. Coastal communities around the world face an increasing risk from flooding as a result of rising sea level, increasing storminess and land subsidence^ 1 , 2 . Salt Marshes can act as natural buffer zones, providing protection from waves during storms^ 3 , 4 , 5 , 6 , 7 . However, the effectiveness of Marshes in protecting the coastline during extreme events when water levels are at a maximum and waves are highest is poorly understood^ 8 , 9 . Here we experimentally assess wave dissipation under storm surge conditions in a 300-metre-long wave flume tank that contains a transplanted section of natural Salt marsh. We find that the presence of marsh vegetation causes considerable wave attenuation, even when water levels and waves are highest. From a comparison with experiments without vegetation, we estimate that up to 60% of observed wave reduction is attributed to vegetation. We also find that although waves progressively flatten and break vegetation stems and thereby reduce dissipation, the marsh substrate remained stable and resistant to surface erosion under all conditions. The effectiveness of storm wave dissipation and the resilience of tidal Marshes even at extreme conditions suggest that Salt marsh ecosystems can be a valuable component of coastal protection schemes.
Diana I Montemayor - One of the best experts on this subject based on the ideXlab platform.
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Effects of Spartina Wrack on Surface-Active Arthropod Assemblage Under Different Environmental Contexts in Southwest Atlantic Salt Marshes
Estuaries and Coasts, 2019Co-Authors: Diana I Montemayor, Alejandro D. Canepuccia, Juan Farina, Mariana Addino, Macarena Valiñas, Oscar IribarneAbstract:Large amounts of tidally accumulated detritus (i.e., wrack) are an important source of disturbance affecting different abiotic and biotic characteristics in Salt Marshes, which could in turn affect the macrofauna assemblage. The purpose of this study was to evaluate the importance of wrack disturbance in Southwest Atlantic (SWA) Salt Marshes and its effects on the surface-active arthropod assemblage under different environmental contexts. By sampling the most important SWA Salt Marshes (from 36° 19′ S to 41° 01′ S), we found that wrack is a widespread disturbance in this region, present in all the Salt Marshes and periods sampled. However, the biomass and type of wrack ( Spartina alterniflora vs. S. densiflora ) vary according to the species that dominates each Salt marsh. At two of these sites (Bahia Blanca (BB), 38° 59′ S and San Clemente (SC), 36° 19′ S), chosen because they represent the two Salt marsh types in the SWA region (dominated by Spartina alterniflora or S. densiflora ), we performed a field experiment by manipulating the presence and absence of wrack and conducting field samplings of sediment organic matter content and water content. We found that wrack affects surface arthropod assemblage but that this effect was not consistent for the different Salt Marshes: in BB, it changed the surface-active arthropod assemblage (shifted towards more detritivorous taxa) and increased the number of total individuals but had no effect on the number of species or diversity. At SC, wrack had no effect on any of the parameters evaluated. We suggest that the type of wrack in each Salt marsh modulates the amount of organic matter content in the sediment: BB had wrack of better nutritional quality (dominated by S. alterniflora ) and in turn had greater organic matter content in the sediment of wrack zones than in no-wrack zones, while in SC (dominated by S. densiflora ), there is no differences between the two zones. We also suggest that depending on the original surface-active arthropod assemblage, those modifications will either favor (BB) or not favor (SC) wrack colonization by the surface-active arthropod assemblage. Moreover, considering that SWA wrack has different compositions and that the biomass differs among the different Salt Marshes, we expect wrack effects in the SWA, and probably in other regions, to be site-specific.
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Influence of Grasshopper Herbivory on Nitrogen Cycling in Northern Gulf of Mexico Black Needlerush Salt Marshes
Estuaries and Coasts, 2017Co-Authors: Diana I Montemayor, Eric L Sparks, Oscar Iribarne, Just CebrianAbstract:Herbivory is a common process in Salt Marshes. However, the direct impact of marsh herbivory on nutrient cycling in this ecosystem is poorly understood. Using a 15N enrichment mesocosm study, we quantified nitrogen (N) cycling in sediment and plants of black needlerush (Juncus roemerianus) Salt Marshes, facilitated by litter decomposition and litter plus grasshopper feces decomposition. We found 15 times more 15N recovery in sediment with grasshopper herbivory compared to sediment with no grasshopper herbivory. In plants, even though we found three times and a half larger 15N recovery with grasshopper herbivory, we did not find significant differences. Thus, herbivory can enhance N cycling in black needlerush Salt Marshes sediments and elevate the role of these Salt Marshes as nutrient sinks.
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crab bioturbation and herbivory may account for variability in carbon sequestration and stocks in south west atlantic Salt Marshes
Frontiers in Marine Science, 2016Co-Authors: Paulina Martinetto, Diana I Montemayor, Juan Alberti, Cesar Serra Bonifacio Costa, Oscar IribarneAbstract:Coastal vegetation plays an important role for climate change mitigation. Compared with terrestrial ecosystems, coastal vegetation shows higher rates of atmospheric CO2 uptake and a more efficient retention of carbon (C) in sediments. Salt Marshes present the highest values as C binders, although a global estimation of these values is still pending due to regional gaps in the records predominantly from the southern hemisphere. There are no clear patterns or dominant processes with enough evidence to account for the observed variability, suggesting that context dependent processes are likely greatest influencers on C storage. Salt Marshes in the South West Atlantic (SWA) coast are densely populated by the intertidal burrowing and herbivore crab Neohelice (=Chasmagnathus) granulata. Many ecological processes related to C transformation occurring in these Salt Marshes are influenced by crab activities, either through bioturbation or via herbivory. We hypothesize that N. granulata could have a significant role in the capacity of SWA Salt Marshes to bind C. Reduction of plant biomass, increased aerobic decomposition in the sediment and facilitation of erosion are some of the multiple effects exerted by N. granulata that can directly and indirectly modify the capacity of Salt Marshes to bind C. Here, we compiled information available regarding C sequestration and accumulation in SWA coastal Salt Marshes and propose a hypothetical model including the mechanisms mediated by N. granulata that interfere the transformation paths of C in Salt Marshes. The data suggest that mechanisms that are top-down regulated, negatively affect C accumulation in the form of aboveground biomass especially in Salt Marshes dominated by Spartina alterniflora. While, mechanisms mediated by bioturbation can negatively (increasing oxygenation and thus facilitating aerobic degradation) affect as well as positively (increasing retention of macrodetritus) affect the accumulation of C, the latter being of greater magnitude in Spartina densiflora Salt Marshes.
Andrea Defina - One of the best experts on this subject based on the ideXlab platform.
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self organization of shallow basins in tidal flats and Salt Marshes
Journal of Geophysical Research, 2007Co-Authors: Andrea Defina, Sergio Fagherazzi, Luca Carniello, Luigi DalpaosAbstract:[1] Shallow tidal basins such as the Venice Lagoon, Italy, are often characterized by extensive tidal flats and Salt Marshes that lie within specific ranges of elevation. Tidal flats lie just below the mean sea level, approximately between −0.6 and −2.0 meters above the mean sea level (m a.m.s.l.), whereas Salt Marshes lie at an average elevation higher than mean sea level (i.e., between +0.1 and +0.5 m a.m.s.l.). Only a small fraction of the tidal basin area has elevations between −0.6 and +0.1 m a.m.s.l. This occurrence suggests that the morphodynamic processes responsible for sediment deposition and erosion produce either tidal flats or Salt Marshes but no landforms located in the above intermediate range of elevations. A conceptual model describing this evolutionary trend has recently been proposed. The model assumes that the bimodal distribution of bottom elevations stems from the characteristics of wave induced sediment resuspension and demonstrates that areas at intermediate elevations are inherently unstable and tend to become either tidal flats or Salt Marshes. In this work, the conceptual model is validated through comparison with numerical results obtained with a two-dimensional wind wave-tidal model applied to the Lagoon of Venice, Italy. Both the present and the 1901 bathymetries of the Venice Lagoon are used in the simulations and the obtained numerical results confirm the validity of the conceptual model. A new framework that explains the long-term evolution of shallow tidal basins based on the results presented herein is finally proposed and discussed.
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critical bifurcation of shallow microtidal landforms in tidal flats and Salt Marshes
Proceedings of the National Academy of Sciences of the United States of America, 2006Co-Authors: Sergio Fagherazzi, Luca Carniello, Luigi Dalpaos, Andrea DefinaAbstract:Shallow tidal basins are characterized by extensive tidal flats and Salt Marshes that lie within specific ranges of elevation, whereas intermediate elevations are less frequent in intertidal landscapes. Here we show that this bimodal distribution of elevations stems from the characteristics of wave-induced sediment resuspension and, in particular, from the reduction of maximum wave height caused by dissipative processes in shallow waters. The conceptual model presented herein is applied to the Venice Lagoon, Italy, and demonstrates that areas at intermediate elevations are inherently unstable and tend to become either tidal flats or Salt Marshes.
