Abstract
Coastal areas support multiple important resource uses including recreation, aquaculture, and agriculture. Unmanaged cattle access to stream corridors in grazed coastal watersheds can contaminate surface waters with fecal-derived microbial pollutants, posing risk to human health via activities such as swimming and shellfish consumption. Improved managerial control of cattle access to streams through implementation of grazing best management practices (BMPs) is a critical step in mitigating waterborne microbial pollution in grazed watersheds. This paper reports trend analysis of a 19-year dataset to assess long-term microbial water quality responses resulting from a program to implement 40 grazing BMPs within the Olema Creek Watershed, a primary tributary to Tomales Bay, USA. Stream corridor grazing BMPs implemented included: (1) Stream corridor fencing to eliminate/control cattle access, (2) hardened stream crossings for cattle movements across stream corridors, and (3) off stream drinking water systems for cattle. We found a statistically significant reduction in fecal coliform concentrations following the initial period of BMP implementation, with overall mean reductions exceeding 95% (1.28 log10)—consistent with 1—2 log10 (90–99%) reductions reported in other studies. Our results demonstrate the importance of prioritization of pollutant sources at the watershed scale to target BMP implementation for rapid water quality improvements and return on investment. Our findings support investments in grazing BMP implementation as an important component of policies and strategies to protect public health in grazed coastal watersheds.
Highlights
Society expects coastal areas to simultaneously support multiple resource uses
Fecal-derived microbial pollutants discharged from various sources in coastal watersheds can contaminate surface waters and pose a significant human health risk via activities such as swimming and shellfish consumption [1,2,3,4]
Multi-use coastal regions across the globe (e.g., United Kingdom [7], Scotland [8], New Zealand [9], Canada [10,11], and China [12]) have documented public health concerns surrounding fecal-derived microbial pollutants associated with agricultural activities taking place in coastal watersheds
Summary
Fecal-derived microbial pollutants discharged from various sources in coastal watersheds can contaminate surface waters and pose a significant human health risk via activities such as swimming and shellfish consumption [1,2,3,4]. Managerial control of cattle access to stream corridors is a critical step in mitigating waterborne microbial pollution in grazed watersheds. To safeguard water quality conditions throughout the Tomales Bay Watershed, state, and federal regulatory programs require managers to minimize microbial pollutant discharges from grazing livestock to tributary streams. PRNS, natural resources management and conservation organizations, and regulatory agencies have collaborated to increase managerial control of cattle access to streams feeding Tomales Bay [24,25]. This dataset provides a unique opportunity to assess stream zone grazing BMP effectiveness for microbial water quality improvement at the spatial and temporal scales that conservation programs are commonly implemented. [21,26,27]
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