Society relies on streams and rivers to perform valuable ecosystem services, yet streams in human-developed landscapes typically have altered ecosystem structure and function compared to streams in more natural settings. Aging and obsolete water infrastructure is a critical, global problem threatening freshwater systems and compromising economic stability, human welfare, and the environment. Globally, local resource managers are tasked to address environmental and human-health concerns associated with aging and obsolete water infrastructure using limited financial resources. Nevertheless, we have a limited understanding of how waste streams may differentially effect ecosystem structure and function through space and time—water-infrastructure decisions at the local level may have large ecological and socioeconomic impacts downstream. Research in the Capps Labe will generate information relevant to supporting local decision-making pertaining to wastewater treatment and other water infrastructure decisions throughout the globe.
Research in river ecosystem ecology has demonstrated the importance of how upstream (e.g., the River Continuum Concept), lateral (e.g., Flood Pulse), and local (e.g., functional processing zones) conditions influence metabolic processes in rivers and the relationships between aquatic communities and food resources. A rich body of work has also demonstrated the potential impact consumers can have on mediating the flow of energy and elements across habitat boundaries, but much less attention has been given to understanding the impact anthropogenically-mediated subsidies can have on energy and elemental cycling within streams and rivers. As human population continues to grow and the world continues to urbanize, a paradigm shift in how ecologists consider the impacts of human waste in freshwaters is needed to accurately describe ecosystem structure and function in rivers, and to predict how freshwater structure and function will change with increasing anthropogenic pressures. Collectively, these projects will generate some of the data needed to support this shift in our thinking, and will inform our understanding of spatial and temporal variation in the factors mediating riverine productivity respiration, and nutrient cycling in temperate and tropical watersheds. Some of the on-going projects and our local, national, and international collaborations are described below.
Capps, K. A., Bateman McDonald, J. M., Gaur, N., & Parsons, R. (2020). Assessing the socio-environmental risk of onsite wastewater treatment systems to inform management decisions. Environmental Science & Technology, 54: 14843-14853. https://doi.org/10.1021/acs.est.0c03909
Capps, K. A. (2019). Wastewater infrastructure and the ecology and management of freshwater systems. Acta Limnologica Brasiliensia 31. http://dx.doi.org/10.1590/s2179-975×3719
Capps, K. A., Bentsen, C. N., & Ramírez, A. (2016). Poverty, urbanization, and environmental degradation: urban streams in the developing world. Freshwater Science 35: 429-435. https://doi.org/10.1086/684945
Cease, A. J., Capps, K. A., Gates, K. K., McCrackin, M. L., & Nidzgorski, D. A. (2015). Consumer‐driven nutrient dynamics in urban environments: the stoichiometry of human diets and waste management. Oikos 124: 931-948. https://doi.org/10.1111/oik.02391
Roy, A. H., Capps, K. A., El-Sabaawi, R. W., Jones, K. L., Parr, T. B., Ramírez, A., … & Wenger, S. J. (2016). Urbanization and stream ecology: diverse mechanisms of change. Freshwater Science 35: 272-277. https://doi.org/10.1086/685097
Anthropogenically-Derived Subsidies in Temperate and Tropical Systems
Award Abstract #1941555
NSF CAREER: THE IMPACTS OF ANTHROPOGENICALLY-DERIVED SUBSIDIES ON FRESHWATER ECOSYSTEMS
Rivers and streams provide important services, such as drinking water, fisheries, and recreational opportunities. Yet, the integrity of rivers and streams throughout the globe is compromised by pollution from aging and obsolete wastewater infrastructure. Currently, there is limited understanding of how human waste affects stream communities and ecosystem processes. The project will integrate field observations, experiments, and modelling, to advance our understanding of how rivers and streams are affected by wastewater infrastructure, and will provide new insights into interactions between civil and environmental engineering and ecosystem science. This CAREER award will support the training and development of high school students, graduate students, and a postdoctoral researcher.
Understanding the spatial and temporal variation in the factors influencing riverine structure and function is essential to predict how fresh waters will respond to continued anthropogenic change. This CAREER award will couple field observations with field- and lab-based experiments and modelling, to examine: 1) spatial and temporal variation in the quality, quantity, and relative volume of wastewater entering river systems, 2) the effects of wastewater on seasonal and annual patterns of metabolic processes flowing waters, 3) the influence of interactions between wastewater and ambient nutrient concentrations on trophic relationships and on the tissue and mineralization stoichiometry of consumers, and 4) the extent to which consumers transport wastewater-derived energy and elements to resource-limited systems within river networks. The award will integrate wastewater discharge into a spatial subsides framework to support more accurate predictions for how wastewater structures aquatic communities and alters biogeochemical processes in river networks. Moreover, the award will generate the data needed to compare seasonal and annual patterns in riverine metabolic processes in large, tropical rivers. The research will also test how flexibility in the trophic and stoichiometric traits of consumers governs the role they play in biogeochemical cycling under variable environmental conditions. Educational modules and service-learning projects in introductory environmental science and advanced ecology courses will be developed. High school students will be trained in stream ecology and provided internships with the local government and freshwater conservation organizations. Additionally, this research will have important management implications, as governments throughout the globe are challenged to fix wastewater effects on water quality, human health, and biodiversity.
Nacional de Ciencia y Tecnología (CONACYT), México (217368): Metabolismo del ecosistema en ríos tropicales: la influencia de la estacionalidad hidrológica y las presiones humanas (Ecosystem metabolism in tropical rivers: the influence of hydrological seasonality and human pressures).
Lead PIs: MM Castillo, M Cazanelli, El Colegio de la Frontera Sur (ECOSUR), México. Co-PIs: W. Arévalo Frías (UJAT), K. Capps, A. (UGA), Jarquín Sánchez (ECOSUR), M Mendoza Carranza (ECOSUR), A. Mesa Jurado (ECOSUR), D. Ramos Muñoz (ECOSUR), R. Rodies Hernández (ECOSUR), A. Ulseth (SHSU)
Ecosystem metabolism is an integrative measure of river functioning because it considers autotrophic and heterotrophic processes in different riverine habitats. Metabolism is the balance between gross primary productivity (GPP) and ecosystem respiration (ER) showing temporal and longitudinal variation in a river network. Most metabolism studies have been conducted in temperate streams using dissolved oxygen measurements during short time periods. However, recent development of sensors that can measure and record oxygen concentrations for longer periods have contributed to identify temporal patterns in metabolism in temperate streams and rivers. Despite these advances, larger rivers, particularly those located in the tropics are less understood. In contrast to temperate rivers, temperature and irradiance are relatively stable through the year in tropical systems, and hydrological seasonality may play a much more important role governing GPP and ER. Human activities, such as dam construction and land use change, are expected to affect metabolic regimes by altering the timing and intensity of GPP and ER. Fluctuations in GPP and ER associated with hydrological seasonality and responses to human pressures may influence temporal and spatial variation in the quality and quantity of energy available to support aquatic food webs. Thus, our objective is to evaluate the responses of ecosystem metabolism to hydrological seasonality and anthropogenic pressures in tropical rivers and how these responses influence energy sources and food webs.
Anthropogenic subsidies (i.e., human waste) may be an important source of nutrients, especially in nutrient-limited systems. Relationship between nitrate and soluble reactive phosphorus (SRP) concentrations from the water column (ambient; white) and in wastewater discharge (subsidy; black) entering the Grijalva (○) and Usumacinta (□) basins. In general, phosphorus concentrations of subsidies are higher than ambient phosphorus concentrations and they are a consistently rich source of phosphorus. Modified from Capps 2019.