The negative effects of nutrient pollution in streams, rivers, and downstream waterbodies remain widespread global problems. Understanding the cost-effectiveness of different strategies for mitigating nutrient pollution is critical to making informed decisions and defining expectations that best utilize limited resources, which is a research priority for the US Environmental Protection Agency. To this end, we modeled nutrient management practices including residue management, cover crops, filter strips, grassed waterways, constructed wetlands, and reducing fertilizer in the upper East Fork of the Little Miami River, an 892 km watershed in southwestern Ohio, United States. The watershed is 64% agriculture with 422 km of row crops contributing an estimated 71% of the system's nutrient load. The six practices were modeled to treat row crop area, and among them, constructed wetlands ranked highest for their low costs per kilogram of nutrient removed. To meet a 42% phosphorus (P) reduction target for row crops, the model results suggested that the runoff from 85.5% of the row crop area would need to be treated by the equivalent of 3.61 km of constructed wetlands at an estimated cost of US$2.4 million annually (or US$48.5 million over a 20-year life cycle). This prompted a series of projects designed to understand the feasibility (defined in terms of build, treatment, and cost potential) of retrofitting the system with the necessary extent of constructed wetlands. The practicalities of building this wetland coverage into the system, while leading to innovation in unit-level design, has highlighted the difficulty of achieving the nutrient reduction target with wetlands alone. Approximately US$1.2 million have been spent on constructing 0.032 km of wetlands thus far and a feasibility analysis suggests a cost of US$38 million for an additional 0.409 km. However, the combined expenditures would only achieve an estimated 13% of the required treatment. The results highlight the potential effectiveness of innovative design strategies for nutrient reduction and the importance of considering realistic field-scale build opportunities, which include accounting for acceptance among landowners, in watershed-scale nutrient reduction simulations using constructed wetlands.

Nutrient loads from agricultural runoff in the upper Midwest continue to contribute to Gulf Coast hypoxia and harmful algal blooms due to insufficient retention of nitrogen (N) and phosphorus (P) associated with row crop agriculture and highly productive soils. In the coming decades, much of the drainage infrastructure in this region will be rebuilt to modern design standards. At the same time, the region is developing and implementing strategies to reduce nutrient export. A group of Iowa stakeholders representing agricultural producers, land managers, and researchers met seven times in late 2018 and early 2019 and was asked to describe ecosystem service information needs that could support nutrient best management practice decisions in Iowa. The stakeholder group identified the importance and relevance of a catchment-scale (i.e., small watershed) analysis of a set of priority ecosystem services associated with agricultural tile drainage improvements and targeted water quality wetlands. Water quality wetlands are wetlands installed strategically to intercept agricultural drainage channels and receive runoff and tile drainage. These potential modifications were codified into four scenarios for literature analysis and hypothesis development including (1) a baseline, no change scenario representing the most prevalent current landscape with underperforming tile drainage infrastructure and degraded wetland functions; (2) upgrade of tile drainage infrastructure without a water quality wetland; (3) installation of a water quality wetland at the drainage district catchment scale but with no drainage improvements; and (4) a combination of adding a water quality wetland and tile drainage infrastructure upgrades at the catchment scale. Synthesizing published field-scale and modeling results across a collection of relevant studies suggests that the combined scenario of improved drainage paired with a water quality wetland may result in increased crop yields, habitat, pollination, and educational and cultural services as well as decreased global warming potential relative to the baseline scenario. Nitrate ( ) export will likely decrease in the combined scenario, depending on net agricultural export and wetland effectiveness. To better substantiate these findings, more catchment-scale research in the region is required, particularly in the areas of water quality, wetland carbon (C) sequestration, wetland habitat quality, and educational and cultural services. Additionally, research is needed to address the effect of upgrading drainage infrastructure on ecosystem services, as most reported ecosystem service effects have been for new drainage installations. Fully integrated assessments, particularly at the catchment scale, will be key to understanding how land management approaches like adding water quality wetlands and improved drainage affect both agricultural production and ecosystem services.

Pollutants can be reduced, ameliorated, or assimilated when riparian ecosystems have the vegetation, water, and soil/landform needed for riparian functions. Loss of physical form and ecological function unravels assimilation processes, increasing supply and transport of pollutants. Water quality and aquatic organisms are response measures of accumulated upstream discharges, and ultimately of changes in riparian functions. Thus, water quality monitoring often fails to identify or lags behind many causes of pollution or remediation from riparian degradation. This paper reviews the interagency riparian proper functioning condition (PFC) assessment for lotic (running water) riparian ecosystems and outlines connections between PFC and water quality attributes (sediment, nutrients, temperature, and dissolved oxygen [DO]). The PFC interaction of hydrology, vegetation, and soils/landforms influences water quality by dissipating energy associated with high waterflow, thereby reducing vertical instability and lateral erosion while developing floodplains with captured sediment and nutrients. Slowing flood water enables aquifer recharge, deposition, and plant nutrient uptake. Water-loving, densely rooted streambank stabilizing vegetation and/or wood helps integrate riparian functions to maintain channel pattern, profile, and dimension with characteristics for a diversity of habitats. A complex food web helps slow the nutrient spiral with uptake and storage. Temperature fluctuations are dampened by delayed discharges, narrower and deeper active channels, coarser substrates that enhance hyporheic interchange, and shade from riparian vegetation. After assessment and implementation, monitoring recovery of impaired riparian function attributes (e.g., streambank plant species) naturally focuses on persistent drivers of water quality and aquatic habitat. This provides timely environmental indicators of stream ecological health and water quality remediation projects or land management.

The assessment and monitoring of soil disturbance and its effect on soil quality (i.e., ability to support a range of ecosystem services) has been hindered due to the shortcomings of many traditional analytical techniques (e.g., soil enzyme activities, microbial incubations), including: high cost, long-term time investment and difficulties with data interpretation. Consequently, there is a critical need to develop a rapid and repeatable approach for quantifying changes in soil quality that will provide an assessment of the current status, condition and trend of natural and managed ecosystems. Here we report on a rapid, high-throughput approach to develop an ecological 'fingerprint' of a soil using Fourier transformed infrared (FTIR) spectroscopy and chemometric modeling, and its application to assess soil ecosystem status and trend. This methodology was applied in a highly disturbed forest ecosystem over a 19-year sampling period to detect changes in soil quality (detected via changes in spectral properties), resulting from changes in dynamic soil properties (e.g., soil organic matter, reactive mineralogy). Two chemometric statistical techniques (i.e., hierarchical clustering analysis and discriminate analysis of principal components) were evaluated for interpreting and quantifying similarities/dissimilarities between samples utilizing the entire FTIR spectra (i.e., fingerprint) from each sample. We found that this approach provided a means for clearly discriminating between degraded soils, soils in recovery and reference soils. Results from fingerprint FTIR analysis illustrate its power and potential for the monitoring and assessment of soil quality and soil landscape change.