Community Ecology of Stream Fishes: Concepts, Approaches, and Techniques

2010 ◽  
Keyword(s):  
Organic Matter ◽  
Water Column ◽  
Primary Productivity ◽  
Ecosystem Processes ◽  
Context Dependency ◽  
Stream Fishes ◽  
Invertebrate Communities ◽  
Disturbance Regimes ◽  
Mesocosm Experiments

<em>Abstract</em>.—Stream fishes can have strong top-down and bottom-up effects on ecosystem processes. However, the dynamic nature of streams constrains our ability to generalize these effects across systems with different disturbance regimes and species composition. To evaluate the role of fishes following disturbance, we used a series of field and mesocosm experiments that quantified the influence of grazers and water column minnows on primary productivity, periphyton structure, organic matter pools, and invertebrate communities following either scouring floods or drying of prairie streams. Results from individual experiments revealed highly significant effects of fishes, but the direction or magnitude of effects varied among experiments. Meta-analyses across experiments indicated that grazers consistently reduced the relative amount of fine benthic organic matter (FBOM) and chironomid abundance within 2 weeks after disturbances. However, effect sizes (log response ratios) were heterogeneous across experiments for algal biomass and algal filament lengths measured more than 4 weeks after a disturbance and potentially associated with system productivity and grazer densities. A similar analysis of 3–4 experiments using water column minnows only found a consistent trend of decreasing FBOM in fish treatments relative to controls when measured less than 2 weeks after disturbances and increase in gross primary productivity measured more than 4 weeks after disturbance. These results, along with those of others, were used to develop a conceptual framework for predicting the potential role of fishes in streams following disturbances (flood and drying). Both theoretical and empirical research shows that recovery of stream ecosystem processes will depend on the resilience of autotrophic and heterotrophic communities following disturbance. Fish effects may vary among functional groups but are generally predicted to be greatest during early stages of succession when algal and invertebrate communities are less complex and their biomass is low relative to fish biomass. Our analysis underscores the context dependency of consumer effects on ecosystem structure and function in nonequilibrium conditions and suggests that factors regulating fish densities and colonization of algal and invertebrate taxa need to be evaluated to predict the consequences of biodiversity loss in streams with variable or human-modified disturbance regimes.

Effects of Fe addition on sediment P dynamics in a eutrophic lake

2021 ◽  
Author(s):  
Melanie Münch ◽  
Rianne van Kaam ◽  
Karel As ◽  
Stefan Peiffer ◽  
Gerard ter Heerdt ◽  
...  
Keyword(s):  
Water Quality ◽  
Organic Matter ◽  
Surface Water ◽  
Water Column ◽  
Sediment Cores ◽  
Surface Water Quality ◽  
Water Interface ◽  
Eutrophic Lakes ◽  
Fe Addition

&lt;p&gt;The decline of surface water quality due to excess phosphorus (P) input is a global problem of increasing urgency. Finding sustainable measures to restore the surface water quality of eutrophic lakes with respect to P, other than by decreasing P inputs, remains a challenge. The addition of iron (Fe) salts has been shown to be effective in removing dissolved phosphate from the water column of eutrophic lakes. However, the resulting changes in biogeochemical processes in sediments as well as the long-term effects of Fe additions on P dynamics in both sediments and the water column are not well understood.&lt;/p&gt;&lt;p&gt;In this study, we assess the impact of past Fe additions on the sediment P biogeochemistry of Lake Terra Nova, a well-mixed shallow peat lake in the Netherlands. The Fe-treatment in 2010 efficiently reduced P release from the sediments to the surface waters for 6 years. Since then, the internal sediment P source in the lake has been increasing again with a growing trend over the years.&lt;/p&gt;&lt;p&gt;In 2020, we sampled sediments at three locations in Terra Nova, of which one received two times more Fe during treatment than the other two. Sediment cores from all sites were sectioned under oxygen-free conditions. Both the porewaters and sediments were analysed for their chemical composition, with sequential extractions providing insight into the sediment forms of P and Fe. Additional sediment cores were incubated under oxic and anoxic conditions and the respective fluxes of P and Fe across the sediment water interface were measured.&lt;/p&gt;&lt;p&gt;The results suggest that Fe and P dynamics in the lake sediments are strongly coupled. We also find that the P dynamics are sensitive to the amount of Fe supplied, even though enhanced burial of P in the sediment was not detected. The results of the sequential extraction procedure for P, which distinguishes P associated with humic acids and Fe oxides, as well as reduced flux of Fe(II) across the sediment water interface in the anoxic incubations, suggest a major role of organic matter in the interaction of Fe and P in these sediments.&lt;/p&gt;&lt;p&gt;Further research will include investigations of the role of organic matter and sulphur in determining the success of Fe-treatment in sequestering P in lake sediments. Based on these data in combination with reactive transport modelling we aim to constrain conditions for successful lake restoration through Fe addition.&lt;/p&gt;

scholarly journals Seabed Resuspension in the Chesapeake Bay: Implications for Biogeochemical Cycling and Hypoxia

2020 ◽  
Vol 44 (1) ◽  
pp. 103-122
Author(s):  
Julia M. Moriarty ◽  
Marjorie A. M. Friedrichs ◽  
Courtney K. Harris
Keyword(s):  
Organic Matter ◽  
Chesapeake Bay ◽  
Water Column ◽  
Primary Productivity ◽  
Environmental Changes ◽  
Light Attenuation ◽  
Sediment Resuspension ◽  
Nitrogen Dynamics ◽  
Biogeochemical Model ◽  
Order Of Magnitude

AbstractSediment processes, including resuspension and transport, affect water quality in estuaries by altering light attenuation, primary productivity, and organic matter remineralization, which then influence oxygen and nitrogen dynamics. The relative importance of these processes on oxygen and nitrogen dynamics varies in space and time due to multiple factors and is difficult to measure, however, motivating a modeling approach to quantify how sediment resuspension and transport affect estuarine biogeochemistry. Results from a coupled hydrodynamic–sediment transport–biogeochemical model of the Chesapeake Bay for the summers of 2002 and 2003 showed that resuspension increased light attenuation, especially in the northernmost portion of the Bay, shifting primary production downstream. Resuspension also increased remineralization in the central Bay, which experienced larger organic matter concentrations due to the downstream shift in primary productivity and estuarine circulation. As a result, oxygen decreased and ammonium increased throughout the Bay in the bottom portion of the water column, due to reduced photosynthesis in the northernmost portion of the Bay and increased remineralization in the central Bay. Averaged over the channel, resuspension decreased oxygen by ~ 25% and increased ammonium by ~ 50% for the bottom water column. Changes due to resuspension were of the same order of magnitude as, and generally exceeded, short-term variations within individual summers, as well as interannual variability between 2002 and 2003, which were wet and dry years, respectively. Our results quantify the degree to which sediment resuspension and transport affect biogeochemistry, and provide insight into how coastal systems may respond to management efforts and environmental changes.

Ecosystem functions and the work of soft sediments

2021 ◽  
pp. 121-136
Author(s):  
Simon F. Thrush ◽  
Judi E. Hewitt ◽  
Conrad A. Pilditch ◽  
Alf Norkko
Keyword(s):  
Organic Matter ◽  
Ecosystem Services ◽  
Ecosystem Function ◽  
Ecosystem Processes ◽  
Ecosystem Dynamics ◽  
Ecosystem Metabolism ◽  
Ecosystem Functions ◽  
Habitat Creation ◽  
New Methods

This chapter describes various aspects of how we can define ecosystem function and situations ecosystem function in a continuum from ecosystem processes to services. Illustrating that functions are about connections, the chapter uses examples of productivity, organic matter decomposition, ecosystem metabolism, habitat creation and foodwebs. Changes in the contributions of function to ecosystem dynamics are considered. Sedimentary ecosystems are multifunctional, requiring the development of new methods to assess this aspect of sediments and trait-based approaches are discussed. The role of ecosystem functions in underpinning ecosystem services is described to ensure that valuation and mapping exercises do not lose sight of the foundational role of ecosystem functions.

scholarly journals The Roles of Resuspension, Diffusion and Biogeochemical Processes on Oxygen Dynamics Offshore of the Rhone River, France: A Numerical Modeling Study

2016 ◽  
Author(s):  
Julia M. Moriarty ◽  
Courtney K. Harris ◽  
Christophe Rabouille ◽  
Katja Fennel ◽  
Marjorie A. M. Friedrichs ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Organic Matter ◽  
Oxygen Consumption ◽  
Water Column ◽  
Bottom Boundary Layer ◽  
Water Interface ◽  
Bottom Boundary ◽  
Rhône Delta ◽  
Oxygen Dynamics

Abstract. Observations indicate that seabed resuspension of organic material and the associated entrainment of porewater into the overlying water can alter biogeochemical fluxes in some environments, but measuring the role of sediment processes on oxygen and nutrient dynamics is challenging. A modeling approach offers a means of quantifying these fluxes for a range of conditions, but models have typically relied on simplifying assumptions regarding seabed-water column interactions. Thus, to evaluate the role of resuspension on biogeochemical dynamics, we developed a coupled hydrodynamic, sediment transport, and biogeochemical model (HydroBioSed) within the Regional Ocean Modeling System (ROMS). This coupled model accounts for processes including the storage of particulate organic matter (POM) and dissolved nutrients within the seabed; entrainment of this material into the water column via resuspension and diffusion at the sediment-water interface; and biogeochemical reactions within the seabed. A one-dimensional version of HydroBioSed was then implemented for the Rhone Delta, France. To isolate the role of resuspension on biogeochemical dynamics, this model implementation was run for a two-month period that included three resuspension events; also, the supply of organic matter, oxygen and nutrients to the water column was held constant in time. Consistent with time-series observations from the Rhone Delta, model results showed that resuspension increased the diffusive flux of oxygen into the seabed by increasing the vertical gradient of oxygen at the seabed-water interface. This enhanced supply of oxygen to the seabed allowed seabed oxygen consumption to increase, primarily through nitrification. Resuspension of POM into the water column, and the associated increase in remineralization, also increased oxygen consumption in the bottom boundary layer. During these resuspension events, modeled rates of oxygen consumption increased by up to factors of ~ 2 and ~ 8 in the seabed and bottom boundary layer, respectively. When averaged over two months, the intermittent cycles of erosion and deposition led to a 20 % increase of oxygen consumption in the seabed, as well as a larger increase of ~ 200 % in the bottom boundary layer. These results imply that observations collected during quiescent periods, and biogeochemical models that neglect resuspension or use typical parameterizations for resuspension, may underestimate net oxygen consumption at sites like the Rhone Subaqueous Delta. Local resuspension likely has the most pronounced effect on oxygen dynamics at study sites with a high oxygen concentration in the bottom boundary layer, only a thin seabed oxic layer, and abundant labile organic matter.

scholarly journals The roles of resuspension, diffusion and biogeochemical processes on oxygen dynamics offshore of the Rhône River, France: a numerical modeling study

2017 ◽  
Vol 14 (7) ◽  
pp. 1919-1946 ◽  
Author(s):  
Julia M. Moriarty ◽  
Courtney K. Harris ◽  
Katja Fennel ◽  
Marjorie A. M. Friedrichs ◽  
Kehui Xu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Oxygen Consumption ◽  
Water Column ◽  
Water Interface ◽  
Regional Ocean Modeling System ◽  
Biogeochemical Models ◽  
Rhône Delta ◽  
Rhone Delta ◽  
Oxygen Dynamics

Abstract. Observations indicate that resuspension and associated fluxes of organic material and porewater between the seabed and overlying water can alter biogeochemical dynamics in some environments, but measuring the role of sediment processes on oxygen and nutrient dynamics is challenging. A modeling approach offers a means of quantifying these fluxes for a range of conditions, but models have typically relied on simplifying assumptions regarding seabed–water-column interactions. Thus, to evaluate the role of resuspension on biogeochemical dynamics, we developed a coupled hydrodynamic, sediment transport, and biogeochemical model (HydroBioSed) within the Regional Ocean Modeling System (ROMS). This coupled model accounts for processes including the storage of particulate organic matter (POM) and dissolved nutrients within the seabed; fluxes of this material between the seabed and the water column via erosion, deposition, and diffusion at the sediment–water interface; and biogeochemical reactions within the seabed. A one-dimensional version of HydroBioSed was then implemented for the Rhône subaqueous delta in France. To isolate the role of resuspension on biogeochemical dynamics, this model implementation was run for a 2-month period that included three resuspension events; also, the supply of organic matter, oxygen, and nutrients to the model was held constant in time. Consistent with time series observations from the Rhône Delta, model results showed that erosion increased the diffusive flux of oxygen into the seabed by increasing the vertical gradient of oxygen at the seabed–water interface. This enhanced supply of oxygen to the seabed, as well as resuspension-induced increases in ammonium availability in surficial sediments, allowed seabed oxygen consumption to increase via nitrification. This increase in nitrification compensated for the decrease in seabed oxygen consumption due to aerobic remineralization that occurred as organic matter was entrained into the water column. Additionally, entrainment of POM into the water column during resuspension events, and the associated increase in remineralization there, also increased oxygen consumption in the region of the water column below the pycnocline. During these resuspension events, modeled rates of oxygen consumption increased by factors of up to  ∼  2 and  ∼  8 in the seabed and below the pycnocline, respectively. When averaged over 2 months, the intermittent cycles of erosion and deposition led to a  ∼  16 % increase of oxygen consumption in the seabed, as well as a larger increase of  ∼  140 % below the pycnocline. These results imply that observations collected during quiescent periods, and biogeochemical models that neglect resuspension or use typical parameterizations for resuspension, may underestimate net oxygen consumption at sites like the Rhône Delta. Local resuspension likely has the most pronounced effect on oxygen dynamics at study sites with a high oxygen concentration in bottom waters, only a thin seabed oxic layer, and abundant labile organic matter.

Conclusions on the role of salt-affected soils in primary succession on the Tanana River floodplain, interior Alaska

1993 ◽  
Vol 23 (5) ◽  
pp. 1015-1018 ◽  
Author(s):  
K. Van Cleve ◽  
J. Yarie ◽  
L.A. Viereck ◽  
C.T. Dyrness
Keyword(s):  
Organic Matter ◽  
Plant Community ◽  
Ecosystem Processes ◽  
Future Research ◽  
Ecosystem Structure ◽  
River Floodplain ◽  
Interior Alaska ◽  
Floodplain Ecosystems ◽  
Salt Affected Soils

Results of the study of salt-affected soils on the Tanana River floodplain in interior Alaska raised a number of key issues that are important to resolve with future research in this fluvial environment. The results emphasized the prominent role of plant succession in ecosystem structure and function in northern boreal forests. For example, alder plays a crucial role in organic matter and nitrogen dynamics in floodplain ecosystems. This plant species has an impact on ecosystem processes in successional stages beyond its period of dominance on the floodplain. The potential facilitative nature of nitrogen accumulation, mediated by alder, to plant community development during and subsequent to the alder phase of succession should be examined in future studies. Organic matter chemistry and soil temperature appeared to be more important controls of soil processes than high soil salt content. Moreover, secondary plant chemicals may play a role in determining rates of soil nitrification in these floodplain ecosystems. The importance of ion balance to plant nutrition and primary production in salt-affected soils is an important topic for future research. Groundwater may be a unique source of water and nutrients to floodplain plant communities. The magnitude of water flux to the rooting zone in relation to terrace elevation and river level and its importance to plant growth is a significant consideration in the semiarid environment of interior Alaska. The established plant community indicates which species are successful in this environment. Optimum species-terrace combinations may exist that maximize productivity through use of unique moisture and nutrient supplies associated with a shallow water table. Results of this work suggested that new research initiatives are crucial to advance the fundamental understanding of controls of ecosystem processes and as a base of information to support forest resource management.

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