Biogeochemical and climate drivers of wetland phosphorus and nitrogen release: Implications for nutrient legacies and eutrophication risk

Abstract

The dynamics and processes of nutrient cycling and release were examined for a lowland wetland-pond system, draining woodland in southern England. Hydrochemical and meteorological data were analyzed from 1997 to 2017, along with high-resolution in-situ sensor measurements from 2016 to 2017. The results showed that even a relatively pristine wetland can become a source of highly-bioavailable phosphorus, nitrogen and silicon during low-flow periods of high ecological sensitivity. The drivers of nutrient release were primary production and accumulation of biomass, which provided a carbon source for microbial respiration and, via mineralization, a source of bioavailable nutrients for phosphorus and nitrogen co-limited microbes. During high-intensity nutrient-release events, the dominant nitrogen-cycling process switched from denitrification to ammonification, and a positive-This article is protected by copyright. All rights reserved. 2 feedback cycle of phosphorus and nitrogen release was sustained over several months during summer and fall. Temperature controls on microbial activity were the primary drivers of short-term (day-today) variability in phosphorus release, with subdaily (diurnal) fluctuations in phosphorus concentrations driven by water-body metabolism. Inter-annual relationships between nutrient release and climate variables indicated 'memory' effects of antecedent climate drivers, through accumulated legacy organic matter from the previous year's biomass production. Natural flood management initiatives promote the use of wetlands as 'nature-based solutions' in climate-change adaptation, flood management, and soil and water conservation. This study highlights potential water-quality trade-offs, and shows how the convergence of climate and biogeochemical drivers of wetland nutrient release can amplify background nutrient signals by mobilizing legacy nutrients, causing water-quality impairment and accelerating eutrophication risk.

Data-Driven System Dynamics Model for Simulating Water Quantity and Quality in Peri-Urban Streams

“…Alternatively, and considering the continuous overestimation in the summer period for all associated sampling periods, a diffuse release from phosphorous stored in the streambed sediments in the summertime cannot be excluded. Such processes have been observed and described in lentic environments [85], but also in streams where phosphorous becomes available by desorption and fueled by enhanced decomposition of organic matter and lower oxygen levels at higher temperatures [56,86]. P-release from the sediment in the urban stream environment has also been documented when coupled with low DO concentrations ( [87]), although often in connection with lower NO 3 concentrations compared to the present study.…”

“…The simulations revealed, for example, an underestimation of phosphorus concentrations compared to the observed data. While unknown sources such as agricultural drainage or septic tanks cannot be excluded in peri-urban catchments and should be investigated further, several studies pointed out an enhanced release of reactive and legacy phosphorus in summer periods under low DO conditions for both mixed and single land-use streams [56,85,87]. Such a process can become an important feedback mechanism.…”

Sediment and Nutrient Retention in Ponds on an Agricultural Stream: Evaluating Effectiveness for Diffuse Pollution Mitigation

“…Our study did not undertake EPC 0 measurements for consideration of SRP removal; however, bed sediment P enrichment in ponds was measured using the sediment traps (Section 4.3). SRP retention in the ponds may also be aided by the persistently high nitrate concentrations, which can buffer the reductive dissolution of Fe and thereby limit any redox-mediated SRP release from sediment [60][61][62].…”

River metabolic fingerprints and regimes reveal ecosystem responses to enhanced wastewater treatment

“…• Demonstrates value of metabolism and nutrient monitoring for more holistic understanding of river ecosystem health. Halliday et al, 2016;Koenig et al, 2019;Rode et al, 2016;Sudduth et al, 2011;Yates et al, 2018), including nutrient cycling (Jarvie et al, 2018a(Jarvie et al, , 2020O'Donnell & Hotchkiss, 2019;Plont et al, 2020), the effects of climate and land use change (Cross et al, 2022;Griffiths et al, 2013;Gucker et al, 2009;Ledford et al, 2017;Yates et al, 2013), and as a tool in environmental management (Chowanski et al, 2020;Cohen et al, 2013;Halliday et al, 2015;Jankowski et al, 2021). Although many studies have examined the impacts of wastewater discharges and secondary and tertiary treatment on nutrient concentrations and loads (e.g., Billen et al, 2005;Carey & Migliaccio, 2009;Garnier et al, 2018;Jarvie et al, 2006), there remains a relative paucity of information on the effects of enhanced wastewater treatment on river metabolism.…”