The use of a mass balance phosphorus budget for informing nutrient management in shallow coastal lakes
| Autor: | S. Waters, Jenny Webster-Brown |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Hydrology
geography Environmental Engineering geography.geographical_feature_category 010504 meteorology & atmospheric sciences Water flow Drainage basin Sediment Wetland 010501 environmental sciences Management Monitoring Policy and Law 01 natural sciences Macrophyte Retention basin Environmental Chemistry Environmental science Water quality Eutrophication 0105 earth and related environmental sciences Water Science and Technology Civil and Structural Engineering |
| Zdroj: | Journal of Hydro-environment Research. 10:32-49 |
| ISSN: | 1570-6443 |
| DOI: | 10.1016/j.jher.2015.11.002 |
| Popis: | Eutrophication has degraded ecosystem, cultural and recreational values in Lake Forsyth, a small, shallow, coastal lake in New Zealand. To inform catchment management decisions designed to prevent algal blooms and improve water quality, a sub-catchment scale, mass-balance approach to understanding the behaviour of the critical nutrient, phosphorous (P), has been taken. To determine a P budget for the lake, and identify key P reservoirs, hydrological inflows and outflows were measured over a 15 month period. These were combined with total (TP) and dissolved reactive P (DRP) concentrations in these flows, to determine the external load of P transported to the lake. Lake water was also analysed for TP and DRP concentrations, and chemical extractions were used to determine the mass and mobility of P in the lake sediments. Biomass surveys and chemical digestions were used to quantify the mass of P contained in lake macrophytes. Changes in the lake water P reservoirs were then used to assess the contribution of external P loading relative to fluxes of P from the sediment to the lake water column (internal P loading). More than 7000 kg P per year was delivered to the lake, 68% of which came from a single sub-catchment. P associated with suspended particulate material accounted for 80% of the external P load transported into the lake and 61% of the load delivered over the study period was transported during a single flood event. A reduction of 53% in the external P load is necessary to achieve a recommended areal loading guideline. As the lake has no permanent outflow, this external load and the low flushing rates have created a large legacy reservoir of P in the lake sediments with 70% of external P loads retained in the lake. It is the release of P from these lake sediments rather than fluctuations in external loading that control P concentrations in the lake water column during the blooms of nitrogen-fixing cyanobacteria. The results indicate the importance of targeting both external and internal loading processes in the catchment. The sub-catchment scale, mass-balance approach to determining a P budget and quantifying P reservoirs enable critical source areas for external P loads to be identified, and the potential efficacy of targeted interventions to reduce P sources and minimise P transport, such as wetlands and sediment retention basins, to be assessed. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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