Using Ecological Stoichiometry to Examine Food Web...
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Using Ecological Stoichiometry to Examine Food Web Structure in an Oligotrophic Stream Usando Estequiometría Ecológico Para Examinar la Estructura de Alimentaria en un Arroyo Oligotrófica Abstract The downstream transport and relative concentration of nutrients are thematic in driving the overall structure and function of stream ecosystems. The slightest increase in nutrient loads can result in a dramatic shift in ecosystem health, productivity, and sustainability. These potential shifts in nutrient loading rates can be a result of both natural and anthropogenic sources. Through determining the carbon (C), nitrogen (N), and phosphorus (P) concentrations of several key ecosystem components, we can determine the degree of nutrient limitation (or nutrient enrichment) at our study sites, as well as predict the relative importance of food web components. In this research project we determine the C:N:P ratios for the basal components of the Harmon Creek food web including: the water column, soil, detritus, primary producers (algae), and secondary consumers (fish). Here we present a description of ecological stoichiometry, our experimental design, and expected C:N:P ratios from three study sites along an upstream-to-downstream transect in Harmon Creek, a sandy bottomed, oligotrophic stream. We hypothesize that nutrient ratios will vary across relatively short spatial distances, with more downstream sites possessing higher nutrient concentrations and lower C:N:P ratios. El transporte del abajo corriente y la concentración relativa de nutrientes son temáticas en controlando la estructura general y la función de los ecosistemas de arroyos. Un menor crecimiento de las cargas de nutrientes puede resultar en un cambio dramático en la salud, la productividad y la sostenibilidad de los ecosistemas. Estos cambios potenciales en las cargas de nutrientes puede ser resultados de fuentes naturales y antropogénicas. A través de la determinación del carbono (C), nitrógeno (N) y fósforo (P), las concentraciones de varios componentes clave del ecosistema, podemos determinar el grado de limitación de nutrientes (o el enriquecimiento de nutrientes) en nuestros sitios de estudio, y también predecir la importancia relativa de los componentes de alimentos. En este proyecto de investigación determinamos proporción de C: N: P para los componentes de la trófica de Harmon Creek incluiendo: la columna de agua, el suelo, detritus, producores primarios, y de los consumidores secundarios. Aquí presentamos los datos preliminares de nutrientes de tres estudio de sitios a lo largo de un transecto de arriba hace abajo corriente en Harmon Creek, un fondo de arena, arroyo de oligotróficos. Estos datos preliminares muestran cómo los nutrientes pueden variar a través de distancias relativamente cortas. Esperamos que a través de repetidas muestras de estos sitios vamos a ser capaces de comprender mejor no sólo el espacio, pero la variación temporal en las concentraciones de nutrientes en el ecosistema del Harmon Creek. Christopher W. Rahlwes 1 , Jeffrey R. Wozniak 2 , and Raelynn Deaton 1 1 Department of Biological Science, Sam Houston State University, Huntsville, TX 77341 2 Texas Research Institute for Environmental Studies, Sam Houston State University, Huntsville, Texas 77340 Methods Ecological Stoichiometry 101 Literature Cited Harmon Creek Watershed Study Site 1: Headwater location at the SHSU Center for Biological Field Studies Study Site 2: Mid-creek location Study Site 3: Downstream location near the confluence of Harmon Creek and the Trinity River. This study will focus on determining the ecological stoichiometry (C:N:P ratios) of five key ecosystem components (Figure 1) found in Harmon Creek, Huntsville, TX. We will collect samples at three locations along an upstream-to-downstream transect (Figure 2). In addition, to gauge the impact of anthropogenic nutrient loading on the Harmon Creek watershed, water samples will be collected from a site immediately down stream of the Parker Creek sewage treatment plant (Figure 2). Experimental Design: To capture any spatial variability that may occur at each stream study site, each location will be partitioned into three 100m sections and a triplicate set of all ecosystem samples will be collected in each zone. All samples will be individually processed and analyzed for nutrient content and then an average value will be calculate for each component, at each site, for each sample event. This process will be replicated monthly. Field Collection of Samples: At each site we will collect samples for: water, soil, dominant algae, allochthonous detritus, and fish. Soil samples will be collected using a 60 cc soil core (~depth 10 cm). The predominant form of stream algae (e.g. green filamentous algae) will be collected using a mesh metal sieve, while fish (Black Tail Shiner, Cyprinella venusta & Red Tail Shiner, Cyprinella lutrensis) will be collected using a 3 meter seine net. Water samples will be collected in 3x rinsed dark-sided 250ml plastic Nalgene bottles. Lastly, allochthonous detritus (e.g. broad leaf deciduous leaves) will be collected at each study site. All samples will be collected in triplicate, placed in Whirl-paks and transported on ice to the Texas Research Institute for Environmental Studies (TRIES) Analytical lab for analysis. Laboratory Preparation &Analysis : At the TRIES analytical Lab, all samples will dried at 70°C, or to a constant weight. When samples are fully dried they will be homogenized using either a mortar & pestle or a mechanical grinder. Nutrient concentration (C, N, & P) will be determined will the be analyzed using a Thermo nitrogen analyzer, UIC carbon analyzer, and Spectra ICP. Harmon Creek Ecosystem Component Location C N P C:N C:P N:P Citation Water Column ELA, ON 41.7 4 0.19 10.4 219 21 Hecky et. al 1993 Water Column McLoed Bay 10.5 1.2 0.06 8.8 172 20 Hecky et. al 1993 Great Slave Lake, NT Soil ELA, ON 204 21 1.98 11.8 266 23 Hecky et. al 1993 Detritus (Eichornia crassipes) Lake Apopka, FL 2.53 0.270 88.91 41 710 - Reddy et. al 1991 Thalassia testudinum FL Keys 36.9 1.76 0.113 24.6 937.4 40.2 Fourqurean et. al ‘01 Cyprinidae ELA, Ontario 45.7 9.7 1.49 5.55 88.5 15.7 Sterner et. al 2000 Ecological stoichiometry is the study of the balance between key chemical substances in ecosystems and how the ratios of these chemicals can impact ecological interactions and processes (Sterner and Elser, 2002). The application of ecological stoichiometry allows us to track the flux of nutrients through the components of an ecosystem (Figure 1). Through comparing the nutrients of the various food web components, it is possible to determine the nutrient requirements of organisms and potentially track (e.g. in the predator/ prey scenario) a given nutrient’s origin. This process is somewhat more difficult in stream ecosystems, which possess constant flow resulting in a high level of connectedness between study sites. Here, the use of ecological stoichiometry may provide information on the origin of allochthonous nutrients to the stream and the mineralization and movement of autochthonous nutrients within the stream food web. This information can then be used to determine which nutrient is limiting (most often P or N in aquatic ecosystems) and how individual organisms maintain homeostasis throughout the ecosystem. Parker Creek Sewage Treatment Plant Learnhowtofish.com Bait-fishing.com Fourqurean, J. W., and J. C. Zieman. 2001. Nutrient content of the seagrass Thalassia testudinum reveals regional patterns of relative availability of nitrogen and phosphorus in the Florida Keys USA. Biogeochemistry 61: 229-245. Hecky, R. E., P. Campbell, and L. L. Hendzel. 1993. The stoichiometry of carbon, nitrogen, and phosphorus in particulate matter of lakes and oceans. Limnol. Ceanogr, 38(4): 709-724, Reddy, K. R., and W. F. DeBusk. 1991. Decomposition of water hyacinth detritus in eutrophic lake water. Hydrobiologia 211: 101- 109. Sterner, R. W., and N. B. George. 2000. Carbon, nitrogen, and phosphorus stoichiometry of cyprinid fishes. Ecology, 81(1): 127-140. Sterner, R. W., and J. J. Elser. 2002. Ecological Stoichiometry. Princeton University Press, Princeton, NJ. * We thank Dr. Chad Hargrave for his help in this research. We also thank Chris Kroll and Rick Lewis for field assistance Figure 1: Conceptual diagram of the key ecosystem components (depicted as ovals) of Harmon Creek considered in this experiment. Arrows represent potential points of connection (nutrient fluxes) between components. The dashes box depicts the different flow regimes that are possible in the watershed with the size of the arrow = magnitude of flow and instantaneous nutrient loading rates. Table 1: Various carbon (C), nitrogen (N), phosphorus (P) concentrations and the associated C:N:P ratios for components of aquatic ecosystems. (All data in mole:mole ratio) Filamentous green algae Allochthonous detritus (deciduous leaves) Soil core (60cc) Blacktail Shiner (Cyprinella venusta) Redtail Shiner (Cyprinella lutrensis) Figure 4 illustrates the hypothesized relationship in nutrient ratios across all study sites. Here, we hypothesize that site #1 will have the lowest nutrient concentrations and lowest quantity of food resources. This is due to the fact that it is located in a relatively pristine location, near the headwaters of Harmon Creek. Furthermore, as water flows downstream (Sites #2 & #3) we anticipate the concentration of N and P to increase (i.e. decrease in C:nutrient ratio) and the overall quantity of resource (carbon) to increase. Nested within each study site also exists the potential for independent patterns in nutrient concentrations of system components (shaded ovals in Fig. 4). Components at each site may possess modified nutrient concentrations based on local runoff (nutrient loading rates), degree of upstream nutrient processing, and varying rates of ecological processes. Through the repeated sampling of our study sites throughout the year, we hope to be able to determine how nutrient ratios and the overall ecological stoichiometry of Harmon Creek varies both spatially (location along the stream) and temporally (across season & flow dynamics). Figures 3a & 3b: Generalized stoichiometric patterns relating consumer stoichiometry to resource stoichiometry. Horizontal and vertical axes are any single stoichiometric measure (e.g. [N] or C:P ratio). In Figure 3a, points on the 1:1 line represent identical stoichiometry in consumer and resources (consumer stoichiometry always matches the resource stoichiometry). The solid lines represent consumers that perform constant differential nutrient retention. In Figure 3b, strict homeostasis is defined as any horizontal line segment (modified from Sterner and Elser 2002.) Figure 2: Map of the Harmon Creek watershed including the location of our study sites (1-3), the Parker Creek sewage treatment plant, and the city of Huntsville, TX (lower left-hand corner). Andrew.cmu.edu Figure 4: Graph of the expected relationship between the C:N and C:P ratios (i.e. C:nutrient; x-axis) and the amount of carbon (resource quantity; y-axis) at the three sample sites and the sewage treatment site (PC). Each colored bar also represents the nutrient ration of water, w; soil, s; algae, a; detritus, d; and fish, f. (modified from Sterner and Elser 2002.) Potential Outcomes Homeostasis is the physiological regulation of an organism's internal environment reducing changes within the organism. In stoichiometry it results in a narrowing of chemical content of a organism compared to the resources it consumes. Elemental imbalance is the dissimilarity in nutrient content between a consumer and its food resource. If a consumer and its food resources have identical nutrient concentrations, they are perfectly in balance. The greater they differ, the greater their imbalance. It is our hope that the data collected in this project will shed light on the degree of homeostasis/elemental imbalance that is occurring in the Harmon Creek ecosystem. 3a 3b Google.com Bing.com Bing.com Bing.com Bing.com
Transcript of Using Ecological Stoichiometry to Examine Food Web...
Using Ecological Stoichiometry to Examine Food Web Structure in an Oligotrophic StreamUsando Estequiometría Ecológico Para Examinar la Estructura de Alimentaria en un Arroyo Oligotrófica
AbstractThe downstream transport and relative concentration of nutrients are thematic in
driving the overall structure and function of stream ecosystems. The slightest increase innutrient loads can result in a dramatic shift in ecosystem health, productivity, andsustainability. These potential shifts in nutrient loading rates can be a result of bothnatural and anthropogenic sources. Through determining the carbon (C), nitrogen (N),and phosphorus (P) concentrations of several key ecosystem components, we candetermine the degree of nutrient limitation (or nutrient enrichment) at our study sites, aswell as predict the relative importance of food web components. In this research projectwe determine the C:N:P ratios for the basal components of the Harmon Creek food webincluding: the water column, soil, detritus, primary producers (algae), and secondaryconsumers (fish). Here we present a description of ecological stoichiometry, ourexperimental design, and expected C:N:P ratios from three study sites along anupstream-to-downstream transect in Harmon Creek, a sandy bottomed, oligotrophicstream. We hypothesize that nutrient ratios will vary across relatively short spatialdistances, with more downstream sites possessing higher nutrient concentrations andlower C:N:P ratios.
El transporte del abajo corriente y la concentración relativa de nutrientes sontemáticas en controlando la estructura general y la función de los ecosistemas de arroyos.Un menor crecimiento de las cargas de nutrientes puede resultar en un cambio dramáticoen la salud, la productividad y la sostenibilidad de los ecosistemas. Estos cambiospotenciales en las cargas de nutrientes puede ser resultados de fuentes naturales yantropogénicas. A través de la determinación del carbono (C), nitrógeno (N) y fósforo(P), las concentraciones de varios componentes clave del ecosistema, podemosdeterminar el grado de limitación de nutrientes (o el enriquecimiento de nutrientes) ennuestros sitios de estudio, y también predecir la importancia relativa de los componentesde alimentos. En este proyecto de investigación determinamos proporción de C: N: Ppara los componentes de la trófica de Harmon Creek incluiendo: la columna de agua, elsuelo, detritus, producores primarios, y de los consumidores secundarios. Aquípresentamos los datos preliminares de nutrientes de tres estudio de sitios a lo largo de untransecto de arriba hace abajo corriente en Harmon Creek, un fondo de arena, arroyo deoligotróficos. Estos datos preliminares muestran cómo los nutrientes pueden variar através de distancias relativamente cortas. Esperamos que a través de repetidas muestrasde estos sitios vamos a ser capaces de comprender mejor no sólo el espacio, pero lavariación temporal en las concentraciones de nutrientes en el ecosistema del HarmonCreek.
Christopher W. Rahlwes1, Jeffrey R. Wozniak2, and Raelynn Deaton1
1Department of Biological Science, Sam Houston State University, Huntsville, TX 773412Texas Research Institute for Environmental Studies, Sam Houston State University, Huntsville, Texas 77340
Methods
Ecological Stoichiometry 101
Literature Cited
Harmon Creek Watershed
Study Site 1: Headwater location at the SHSU Center for Biological Field Studies
Study Site 2: Mid-creek location Study Site 3: Downstream location near the confluence of Harmon Creek and the Trinity River.
This study will focus on determining the ecological stoichiometry (C:N:P ratios) of five key ecosystem components (Figure 1) found in Harmon Creek, Huntsville, TX. We will collect samples at three locations along an upstream-to-downstream transect (Figure 2). In addition, to gauge the impact of anthropogenic nutrient loading on the Harmon Creek watershed, water samples will be collected from a site immediately down stream of the Parker
Creek sewage treatment plant (Figure 2).
Experimental Design: To capture any spatial variability that may occur at each stream study site, each location will be partitioned into three 100m sections and a triplicate set of all ecosystem samples will be collected in each zone. All samples will be individually processed and analyzed for nutrient content and then an average value will be calculate for each component, at each site, for each sample event. This process will be replicated monthly.
Field Collection of Samples: At each site we will collect samples for: water, soil, dominant algae, allochthonous detritus, and fish. Soil samples will be collected using a 60 cc soil core (~depth 10 cm). The predominant form of stream algae (e.g. green filamentous algae) will be collected using a mesh metal sieve, while fish (Black Tail Shiner, Cyprinella venusta & Red Tail Shiner, Cyprinella lutrensis) will be collected using a 3 meter seine net. Water samples will be collected in 3x rinsed dark-sided 250ml plastic Nalgene bottles. Lastly, allochthonous detritus (e.g. broad leaf deciduous leaves) will be collected at each study site. All samples will be collected in triplicate, placed in Whirl-paks and transported on ice to the Texas Research Institute for Environmental Studies (TRIES) Analytical lab for analysis.
Laboratory Preparation &Analysis: At the TRIES analytical Lab, all samples will dried at 70°C, or to a constant weight. When samples are fully dried they will be homogenized using either a mortar & pestle or a mechanical grinder. Nutrient concentration (C, N, & P) will be determined will the be analyzed using a Thermo nitrogen analyzer, UIC carbon analyzer, and Spectra ICP.
Harmon Creek Ecosystem
Component Location C N P C:N C:P N:P Citation
Water Column ELA, ON 41.7 4 0.19 10.4 219 21 Hecky et. al 1993Water Column McLoed Bay 10.5 1.2 0.06 8.8 172 20 Hecky et. al 1993
Great Slave Lake, NTSoil ELA, ON 204 21 1.98 11.8 266 23 Hecky et. al 1993Detritus (Eichornia crassipes)
Lake Apopka, FL 2.53 0.270 88.91 41 710 - Reddy et. al 1991Thalassia testudinum FL Keys 36.9 1.76 0.113 24.6 937.4 40.2 Fourqurean et. al ‘01Cyprinidae ELA, Ontario 45.7 9.7 1.49 5.55 88.5 15.7 Sterner et. al 2000
Ecological stoichiometry is the study of the balance between key chemicalsubstances in ecosystems and how the ratios of these chemicals can impact ecologicalinteractions and processes (Sterner and Elser, 2002). The application of ecologicalstoichiometry allows us to track the flux of nutrients through the components of anecosystem (Figure 1). Through comparing the nutrients of the various food webcomponents, it is possible to determine the nutrient requirements of organisms andpotentially track (e.g. in the predator/ prey scenario) a given nutrient’s origin. Thisprocess is somewhat more difficult in stream ecosystems, which possess constant flowresulting in a high level of connectedness between study sites. Here, the use ofecological stoichiometry may provide information on the origin of allochthonousnutrients to the stream and the mineralization and movement of autochthonous nutrientswithin the stream food web. This information can then be used to determine whichnutrient is limiting (most often P or N in aquatic ecosystems) and how individualorganisms maintain homeostasis throughout the ecosystem.
Parker Creek Sewage Treatment Plant
Learnhowtofish.com
Bait-fishing.com
Fourqurean, J. W., and J. C. Zieman. 2001. Nutrient content of the seagrass Thalassia testudinum reveals regional patterns of relative availability of nitrogen and phosphorus in the Florida Keys USA. Biogeochemistry 61: 229-245.
Hecky, R. E., P. Campbell, and L. L. Hendzel. 1993. The stoichiometry of carbon, nitrogen, and phosphorus in particulate matter of lakes and oceans. Limnol. Ceanogr, 38(4): 709-724,
Reddy, K. R., and W. F. DeBusk. 1991. Decomposition of water hyacinth detritus in eutrophic lake water. Hydrobiologia 211: 101-109.
Sterner, R. W., and N. B. George. 2000. Carbon, nitrogen, and phosphorus stoichiometry of cyprinid fishes. Ecology, 81(1): 127-140.
Sterner, R. W., and J. J. Elser. 2002. Ecological Stoichiometry. Princeton University Press, Princeton, NJ.
* We thank Dr. Chad Hargrave for his help in this research. We also thank Chris Kroll and Rick Lewis for field assistance
Figure 1: Conceptual diagram of the key ecosystem components (depicted as ovals) of Harmon Creek considered in this experiment. Arrows represent potential points of connection (nutrient fluxes) between components. The dashes box depicts the different flow regimes that are possible in the watershed with the size of the arrow = magnitude of flow and instantaneous nutrient loading rates.
Table 1: Various carbon (C), nitrogen (N), phosphorus (P) concentrations and the associated C:N:P ratios forcomponents of aquatic ecosystems. (All data in mole:mole ratio)
Filamentous green algae
Allochthonous detritus (deciduous leaves)
Soil core (60cc)
Blacktail Shiner (Cyprinella venusta)
Redtail Shiner (Cyprinella lutrensis)
Figure 4 illustrates the hypothesized relationship in nutrient ratios across all study sites. Here, we hypothesize that site #1 will have the lowest nutrient concentrations and lowest quantity of food resources. This is due to the fact that it is located in a relatively pristine location, near the headwaters of Harmon Creek. Furthermore, as water flows downstream (Sites #2 & #3) we anticipate the concentration of N and P to increase (i.e. decrease in C:nutrient ratio) and the overall quantity of resource (carbon) to increase. Nested within each study site also exists the potential for independent patterns in nutrient concentrations of system components (shaded ovals in Fig. 4). Components at each site may possess modified nutrient concentrations based on local runoff (nutrient loading rates), degree of upstream nutrient processing, and varying rates of ecological processes.
Through the repeated sampling of our study sites throughout the year, we hope to be able to determine how nutrient ratios and the overall ecological stoichiometry of Harmon Creek varies both spatially (location along the stream) and temporally (across season & flow dynamics).
Figures 3a & 3b: Generalized stoichiometric patterns relating consumer stoichiometry to resource stoichiometry. Horizontal and vertical axes are any single stoichiometric measure (e.g. [N] or C:P ratio). In Figure 3a, points on the 1:1 line represent identical stoichiometry in consumer and resources (consumer stoichiometry always matches the resource stoichiometry). The solid lines represent consumers that perform constant differential nutrient retention. In Figure 3b, strict homeostasis is defined as any horizontal line segment (modified from Sterner and Elser 2002.)
Figure 2: Map of the Harmon Creek watershed including the location of our study sites (1-3), the Parker Creek sewage treatment plant, and the city of Huntsville, TX (lower left-hand corner).
Andrew.cmu.edu
Figure 4: Graph of the expected relationship between the C:N and C:P ratios (i.e. C:nutrient; x-axis) and the amount of carbon (resource quantity; y-axis) at the three sample sites and the sewage treatment site (PC). Each colored bar also represents the nutrient ration of water, w; soil, s; algae, a; detritus, d; and fish, f. (modified from Sterner and Elser 2002.)
Potential Outcomes
Homeostasis is the physiological regulation of an organism's internal environmentreducing changes within the organism. In stoichiometry it results in a narrowing ofchemical content of a organism compared to the resources it consumes. Elementalimbalance is the dissimilarity in nutrient content between a consumer and its foodresource. If a consumer and its food resources have identical nutrient concentrations,they are perfectly in balance. The greater they differ, the greater their imbalance. It isour hope that the data collected in this project will shed light on the degree ofhomeostasis/elemental imbalance that is occurring in the Harmon Creek ecosystem.
3a 3b
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