School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia, Canada.
Centre for Aquaculture and Environmental Research, Science Branch, Pacific Region, Fisheries and Oceans Canada, West Vancouver, British Columbia, Canada.
PLoS One. 2019 Jul 24;14(7):e0219241. doi: 10.1371/journal.pone.0219241. eCollection 2019.
Peri-urban lakes increasingly experience intensified anthropogenic impacts as watershed uses and developments increase. Cultus Lake is an oligo-mesotrophic, peri-urban lake near Vancouver, British Columbia, Canada that experiences significant seasonal tourism, anthropogenic nutrient loadings, and associated cultural eutrophication. Left unabated, these cumulative stresses threaten the critical habitat and persistence of two endemic species at risk (Coastrange Sculpin, Cultus population; Cultus Lake sockeye salmon) and diverse lake-derived ecosystem services. We constructed water and nutrient budgets for the Cultus Lake watershed to identify and quantify major sources and loadings of nitrogen (N) and phosphorus (P). A steady-state water quality model, calibrated against current loadings and limnological data, was used to reconstruct the historic lake trophic status and explore limnological changes in response to realistic development and mitigation scenarios. Significant local P loadings to Cultus Lake arise from septic leaching (19%) and migratory gull guano deposition (22%). Watershed runoff contributes the majority of total P (53%) and N (73%) loads to Cultus Lake, with substantial local N contributions arising from the agricultural Columbia Valley (41% of total N load). However, we estimate that up to 66% of N and 70% of P in watershed runoff is ultimately sourced via deposition from the nutrient-contaminated regional airshed, with direct atmospheric deposition on the lake surface contributing an additional 17% of N and 5% of P. Thus, atmospheric deposition is the largest single source of nutrient loading to Cultus Lake, cumulatively responsible for 63% and 42% of total N and P loadings, respectively. Modeled future loading scenarios suggest Cultus Lake could become mesotrophic within the next 25 years, highlighting a heightened need for near-term abatement of P loads. Although mitigating P loads from local watershed sources will slow the rate of eutrophication, management efforts targeting reductions in atmospheric-P within the regional airshed are necessary to halt or reverse lake eutrophication, and conserve both critical habitat for imperiled species at risk and lake-derived ecosystem services.
随着流域利用和开发的增加，城郊湖泊越来越多地受到人为活动的强烈影响。库特湖是加拿大不列颠哥伦比亚省温哥华附近的一个寡营养、城郊湖泊，该湖季节性旅游、人为营养负荷和相关的文化富营养化现象显著。如果不加控制，这些累积的压力将威胁到两种濒危特有物种（海岸岭杜父鱼，库特湖种群；库特湖红大麻哈鱼）和多样化的湖泊衍生生态系统服务的关键栖息地和生存能力。我们构建了库特湖流域的水和养分预算，以确定和量化氮（N）和磷（P）的主要来源和负荷。一个稳态水质模型，根据当前的负荷和湖沼学数据进行校准，用于重建历史湖泊营养状况，并探索在现实发展和缓解情景下的湖沼学变化。库特湖的显著局部磷负荷来自于化粪池渗漏（19%）和迁徙海鸥鸟粪沉积（22%）。流域径流水对库特湖贡献了大部分总磷（53%）和氮（73%）负荷，而来自农业哥伦比亚山谷的大量本地氮贡献（占总氮负荷的 41%）。然而，我们估计，流域径流水中高达 66%的氮和 70%的磷最终源自受污染的区域大气沉降源，而湖表面的直接大气沉降则贡献了另外 17%的氮和 5%的磷。因此，大气沉降是库特湖营养负荷的最大单一来源，分别累积承担了总氮和总磷负荷的 63%和 42%。未来的模拟负荷情景表明，库特湖可能在未来 25 年内变为中营养状态，这突出表明需要尽快减少磷负荷。尽管减少当地流域来源的磷负荷将减缓富营养化的速度，但需要针对减少区域大气沉降中的磷来停止或逆转湖泊富营养化，从而保护濒危特有物种的关键栖息地和湖泊衍生生态系统服务。
