Chmura G L, Santos A, Pospelova V, Spasojevic Z, Lam R, Latimer J S
Department of Geography, (and Centre for Climate and Global Change Research), McGill University, 805 Sherbrooke St., W, Montreal, QC, Canada H3A 2K6.
Sci Total Environ. 2004 Mar 29;320(2-3):225-43. doi: 10.1016/j.scitotenv.2003.08.003.
In this study we present a novel comparison of three proxy indicators of paleoproductivity, pigments, biogenic silica (BSi), and cysts of autotrophic dinoflagellates measured in cored sediments from New Bedford Harbor, Massachusetts. In addition to detailed historical reports we use palynological signals of land clearance, changes in the ratio of centric and pennate diatoms, sedimentary organic carbon and stable carbon isotopes to constrain our interpretations. Our study spans the period from prior to European settlement to approximately 1977, during which watersheds were cleared, port development occurred and much of the coastal property became industrialized. The combined effects of nutrient loading from watershed clearance and urban sewage on the estuarine ecosystem shifted not only levels of primary production, but also the nature of the production. Our proxies show that when European colonists first arrived the estuarine production was benthic-dominated, but eventually became pelagic-dominated. Importance of water column production (by diatoms and dinoflagellates) rapidly increased as soil nitrogen was released following forest clearance. Stabilization in rates of forest clearance is reflected as a decline in production. However, population increases in the urbanizing watershed brought new sources of nutrients through direct sewage discharge, apparently again stimulating primary production. We assume that early 20th century changes in sewage discharge and introduction of heavy metals into Harbor waters caused a temporary reduction in primary production. The introduction of a new sewer outfall near the core site and changes in estuarine hydrography due to construction of a hurricane barrier across the mouth of the harbor are reflected by renewed water column production, but decreases in the population of diatoms and dinoflagellates. Fossil pigments suggest renewed water column production in the latest years recorded by our sediment core.
在本研究中，我们对马萨诸塞州新贝德福德港岩芯沉积物中测量的古生产力的三个替代指标进行了全新比较，这三个指标分别是色素、生物源二氧化硅（BSi）和自养甲藻的孢囊。除了详细的历史报告外，我们还利用土地开垦的孢粉学信号、中心硅藻和羽纹硅藻比例的变化、沉积有机碳和稳定碳同位素来限制我们的解释。我们的研究跨越了从欧洲人定居之前到大约1977年的时期，在此期间流域被开垦、港口得到发展，并且大部分沿海地区实现了工业化。流域开垦和城市污水带来的营养物质负荷对河口生态系统的综合影响不仅改变了初级生产力水平，也改变了生产的性质。我们的替代指标表明，欧洲殖民者首次到达时，河口生产以底栖生物为主，但最终变为以浮游生物为主。随着森林砍伐后土壤氮的释放，水柱生产（由硅藻和甲藻进行）的重要性迅速增加。森林砍伐速率的稳定表现为产量下降。然而，城市化流域人口的增加通过直接排放污水带来了新的营养物质来源，显然再次刺激了初级生产。我们假设20世纪初污水排放的变化以及重金属进入港口水域导致初级生产暂时减少。核心站点附近新污水排放口的引入以及由于在港口口建造飓风屏障导致的河口水文变化，表现为水柱生产的恢复，但硅藻和甲藻的数量减少。化石色素表明我们的沉积物岩芯记录的最近几年水柱生产有所恢复。
Zotero 插件