Brent J. Dalzell

Linking water quality and well-being for improved assessment and valuation of ecosystem services

Despite broad recognition of the value of the goods and services provided by nature, existing tools for assessing and valuing ecosystem services often fall short of the needs and expectations of decision makers. Here we address one of the most important missing components in the current ecosystem services toolbox: a comprehensive and generalizable framework for describing and valuing water quality-related services. Water quality is often misrepresented as a final ecosystem service. We argue that it is actually an important contributor to many different services, from recreation to human health. We present a valuation approach for water quality-related services that is sensitive to different actions that affect water quality, identifies aquatic endpoints where the consequences of changing water quality on human well-being are realized, and recognizes the unique groups of beneficiaries affected by those changes. We describe the multiple biophysical and economic pathways that link actions to changes in water quality-related ecosystem goods and services and provide guidance to researchers interested in valuing these changes. Finally, we present a valuation template that integrates biophysical and economic models, links actions to changes in service provision and value estimates, and considers multiple sources of water quality-related ecosystem service values without double counting.

Evaluating the photoalteration of estuarine dissolved organic matter using direct temperature-resolved mass spectrometry and UV-visible spectroscopy

Abstract.Direct temperature-resolved mass spectrometry (DT-MS) was used to evaluate the molecular-level photodegradation of dissolved organic matter (DOM) isolated from three sites in a Chesapeake Bay subestuary (swamp- and marsh-influenced up-river, midestuarine, and bay mouth). From each site, filtered (<0.1 or <0.2 μm) water samples were irradiated in solarsimulated ultraviolet light followed by isolation of the DOM using C18-solid-phase extraction and subsequent DT-MS analysis. To provide background DOM photoreactivity data for the water samples, we also determined dissolved inorganic carbon (DIC) photoproduction and chromophoric dissolved organic matter (CDOM) photobleaching. DIC photoproduction was correlated with initial DOM light absorbance, initial dissolved organic carbon (DOC) concentration, and photobleaching. Changes in DT-MS characteristics within the extracts (in particular, the loss of an “aromatic” signal believed to be from reworked terrestrial material) were found to correlate linearly with the absorbance of the corresponding water samples. A relationship between photobleaching and DT-MS characteristics was also observed, with the upstream samples asymptotically approaching a constant “molecular-level” value as photobleaching increased. Both relationships appeared to be independent of absorbance wavelength in the ultraviolet. Following irradiation, the swamp/marsh-dominated upstream samples resembled the down-stream samples in terms of absorption spectra and MS-determined molecular-level characteristics. These shifts indicate that terrestrially-derived DOM may be more difficult to differentiate from marine DOM upon photodegradation, which has implications regarding evaluating the terrestrial impact within the marine DOM pool.

Estimating water quality effects of conservation practices and grazing land use scenarios

Conservation management practices such as reduced tillage, fertilizer management, and buffer strips are well-established means by which to control erosion and nutrient losses from fields planted in annual row crops. However, agricultural systems which include perennial plant cover, such as the perennial forages found in grazing systems, may represent an alternative way to reduce these losses. In this study, management intensive rotational grazing (MIRG) was tested as a means by which to improve water quality on highly vulnerable row crop land, compared to more traditional conservation management schemes in the south branch of the Root River Watershed (a karst-influenced watershed in Southeastern Minnesota). The effects of both sets of alternative scenarios were evaluated with a watershed-based modeling approach using the Soil and Water Assessment Tool. Alternative conservation management practices included conservation tillage, cover crops, and filter strips. Conversion of row crop production to management-intensive rotational grazing of beef cattle was selected to occur on 2.6% of the total watershed area. Both the conservation management practices and land use changes were targeted to reduce contributions of sediment and phosphorus (P) loads from cropped upland areas. Watershed-wide implementation of all conservation management practices resulted in the greatest reductions in sediment (52%) and total P (28%) loads from upland crop areas, but had the largest land area requirements to achieve these results. Cover crops or filter strips on areas of high slope also showed large cumulative reductions across the watershed and also had the greatest reductions per-unit treated area of all conservation management practices. However, changing land use from row crop production to pasture for grazing was most effective at reducing total sediment and P loads on those acres changed, reducing sediment and P by greater than 85% on targeted areas. Simulation results indicate that utilizing alternative conservation management practices or MIRG, when targeted to areas of steeper slope (greater than 4%), could appreciably reduce sediment and P loads in this watershed, with limited reductions in row crop agriculture acreage.

A High-Throughput DNA-Sequencing Approach for Determining Sources of Fecal Bacteria in a Lake Superior Estuary

Current microbial source-tracking (MST) methods, employed to determine sources of fecal contamination in waterways, use molecular markers targeting host-associated bacteria in animal or human feces. However, there is a lack of knowledge about fecal microbiome composition in several animals and imperfect marker specificity and sensitivity. To overcome these issues, a community-based MST method has been developed. Here, we describe a study done in the Lake Superior-Saint Louis River estuary using SourceTracker, a program that calculates the source contribution to an environment. High-throughput DNA sequencing of microbiota from a diverse collection of fecal samples obtained from 11 types of animals (wild, agricultural, and domesticated) and treated effluent (n = 233) was used to generate a fecal library to perform community-based MST. Analysis of 319 fecal and environmental samples revealed that the community compositions in water and fecal samples were significantly different, allowing for the determination of the presence of fecal inputs and identification of specific sources. SourceTracker results indicated that fecal bacterial inputs into the Lake Superior estuary were primarily attributed to wastewater effluent and, to a lesser extent, geese and gull wastes. These results suggest that a community-based MST method may be another useful tool for determining sources of aquatic fecal bacteria.

Perennial vegetation impacts on stream discharge and channel sources of sediment in the Minnesota River Basin

While sediment loads in streams draining agricultural landscapes have traditionally been attributed to field sources via overland flow and surface erosion, recent research has identified important nonfield sources of sediment in the Minnesota River Basin. We evaluate the impacts of altered vegetation on water budget and sediment loading in Seven Mile Creek, an agricultural watershed with important nonfield sources of sediment. Using the Soil and Water Assessment Tool (SWAT) and monitoring data for different locations, we developed an approach to account for different sediment sources and show that nonfield sediment export is strongly affected by changes in stream discharge, which is affected by vegetation impacts on water yield. This is important because many watershed-scale models are calibrated to sediment loads at the watershed outlet based on the assumption that all sediment is derived from field sources. This can lead to overestimation of erosion from field sources and unrealistic expectations for watershed-scale reductions based on some conservation practices. In Seven Mile Creek watershed under current conditions, approximately 76% of the sediment delivered to the watershed outlet originates from nonfield sources (streambanks and ravines). Relative to the current landscape, increases in perennial grasses or switchgrass (Panicum virgatum L.) cause decreases in water yield owing to differences in evapotranspiration (especially in the spring). As streamflow decreases, sediment export is disproportionately reduced from nonfield sources. These results demonstrating an interaction between evapotranspiration and streambank/ravine erosion are important for showing that nonfield sources of sediment can be important in some watersheds, and that realistic approaches for improving water quality may need to include strategies for managing water quantity.