de Toledo Mauro B, Baulch Helen M
School of Environment and Sustainability, University of Saskatchewan, Saskatoon, SK, Canada; Global Institute for Water Security, University of Saskatchewan, 11 Innovation Blvd, Saskatoon, SK S7N 3H5, Canada.
Sci Total Environ. 2024 Nov 25;953:176012. doi: 10.1016/j.scitotenv.2024.176012. Epub 2024 Sep 3.
Sediment nutrients can be mobilized to overlying water via internal loading, which can be important to aquatic productivity. Using data from 143 Canadian lakes, we show high (~2400-fold) variation of soluble reactive phosphorus (SRP) concentrations in surficial sediment porewater, with results suggesting internal phosphorus loading (IPL) is also likely to vary widely. Consistent with past work at smaller scales, we show that lake depth, pH, trophic status, and bulk sediment Al:P and Fe:P influence porewater SRP, and IPL. Median porewater SRP concentration in lakes with high Al:P (molar ratios >10) were 4.8-fold smaller than in lakes with lower Al:P. In lakes where bulk sedimentary Fe:P molar ratios were >10 porewater SRP was 3.9-fold lower than in lakes with lower Fe:P. High pH (>7.8), along with hyper-eutrophic lakes were associated with higher porewater SRP. Finally, shallow lakes (<4 m depth) had median porewater SRP concentration 6-fold higher than deep lakes (>9 m depth). Important regional differences emerged, linked to regional variation in pH, soils, lake depth and trophic status, and paralleling areas of poor water quality. For example, median porewater SRP in lakes from the Boreal Plains and Prairies ecozones (dominated by Chernozems/Mollisols) was 64-fold and 44-fold higher than in the Boreal Shield (dominated by Podzols/Spodosols) (respectively), although we note that IPL risk is likely important across many ecozones. Using national data, we found in-lake measurements (particularly pH, and salinity) showed strong capacity in predicting porewater SRP (explaining 60-72 % of the variance in the data). Importantly, watershed predictors showed good predictive power, explaining ~50 % of variance in porewater SRP using variables including soil types, and % agriculture. Porewater SRP can be predicted with reasonable accuracy using easily measured variables, as can estimates of internal phosphorus loading, suggesting that landscape limnology holds strong potential in helping to inform lake management by informing understanding of in-lake nutrient sources.
沉积物中的养分可通过内源负荷进入上覆水体，这对水生生物生产力可能具有重要意义。利用来自143个加拿大湖泊的数据，我们发现表层沉积物孔隙水中可溶性活性磷（SRP）浓度存在很高（约2400倍）的变化，结果表明内源磷负荷（IPL）也可能有很大差异。与过去较小尺度的研究一致，我们发现湖泊深度、pH值、营养状态以及沉积物总体的铝磷比和铁磷比会影响孔隙水SRP和IPL。铝磷比高（摩尔比>10）的湖泊中孔隙水SRP的中位数浓度比铝磷比低的湖泊低4.8倍。在沉积物铁磷摩尔比>10的湖泊中，孔隙水SRP比铁磷比低的湖泊低3.9倍。高pH值（>7.8）以及富营养化湖泊与较高的孔隙水SRP相关。最后，浅水湖泊（深度<4米）孔隙水SRP的中位数浓度比深水湖泊（深度>9米）高6倍。出现了重要的区域差异，这与pH值、土壤、湖泊深度和营养状态的区域变化有关，并且与水质较差的区域平行。例如，北方平原和草原生态区（以黑钙土/软土为主）湖泊中孔隙水SRP的中位数分别比北方盾形区（以灰化土/灰壤为主）高64倍和44倍，不过我们注意到IPL风险在许多生态区可能都很重要。利用全国数据，我们发现湖泊内的测量值（特别是pH值和盐度）在预测孔隙水SRP方面表现出很强的能力（解释了数据中60 - 72%的方差）。重要的是，流域预测因子显示出良好的预测能力，使用包括土壤类型和农业占比等变量可解释孔隙水SRP中约50%的方差。利用易于测量的变量可以较为准确地预测孔隙水SRP，内源磷负荷的估算也是如此，这表明景观湖沼学在通过帮助理解湖泊内部养分来源来为湖泊管理提供信息方面具有巨大潜力。
