Landscape Sciences, Department of Environment and Science, PO Box 5078, Brisbane, Queensland 4001, Australia; Australian Rivers Institute, Nathan Campus, Griffith University, 170 Kessels Road, Nathan, Brisbane, Queensland 4111, Australia.
Landscape Sciences, Department of Environment and Science, PO Box 5078, Brisbane, Queensland 4001, Australia; Australian Rivers Institute, Nathan Campus, Griffith University, 170 Kessels Road, Nathan, Brisbane, Queensland 4111, Australia.
Sci Total Environ. 2018 Sep 15;636:1416-1427. doi: 10.1016/j.scitotenv.2018.04.334. Epub 2018 May 5.
Sediments delivered to freshwater and marine environments can make important contributions to the aquatic bioavailable nutrient pool. In the Great Barrier Reef (GBR) catchments, particulate nutrients comprise an important fraction of the end of catchment loads; however, their contribution to the bioavailable nutrient pool is not well understood. This research determined which particulate nutrient parameters are the best indicators of the potential effect of fine sediment (<10 μm) on phytoplankton growth. Surface and subsurface sediments were lab-generated to cover a wide spectrum of particulate nutrient bioavailability from key soil types, land uses and erosion processes (hillslope and gully) in a wet and a dry tropics catchment of the GBR. Phytoplankton bioassays were used to assess freshwater and marine phytoplankton responses to sediments. The best indicators were selected by regressing measurements of phytoplankton growth against nutrient bioavailability parameters measured on the sediments. The selected indicator equations included organic carbon (C) pools for both fresh and marine water, highlighting the role of bacteria in mediating nutrient availability for phytoplankton. The equations also included various fractions of particulate nitrogen (N) (differentiating the adsorbed ammonium-N from the particulate organic N), and the ratios of C to N, which indicate the lability of the organic matter present in the sediment. Dissolved reactive phosphorus was also an important indicator in freshwater. The indicators performed better in assessing bioavailability potential than traditional methods to monitor particulate nutrients, e.g., particulate N and particulate phosphorus. Phytoplankton bioassays indicated that nutrients in sediment can promote phytoplankton growth, with nutrient bioavailability depending not only on sediment load, but also sediment characteristics associated with its parent soil. These characteristics vary with soil type, land use and erosion process. Findings will help prioritize erosion control to catchment areas which are most likely to contribute large amounts of bioavailable particulate nutrients to the GBR.
输送到淡水和海洋环境的沉积物可以为水生生物可用营养物库做出重要贡献。在大堡礁（GBR）集水区，颗粒营养物是末端集水区负荷的重要组成部分；然而，它们对生物可用营养物库的贡献尚不清楚。本研究确定了哪些颗粒营养参数是衡量细沉积物（<10μm）对浮游植物生长潜在影响的最佳指标。从 GBR 干湿两季集水区的关键土壤类型、土地利用和侵蚀过程（山坡和沟壑）中生成了表面和次表面沉积物，以涵盖广泛的颗粒营养物生物可利用性范围。利用浮游植物生物测定法来评估淡水和海洋浮游植物对沉积物的反应。通过将浮游植物生长的测量值与沉积物上测量的营养物生物可利用性参数进行回归，选择最佳指标。所选指标方程包括淡水和海水的有机碳（C）池，突出了细菌在介导浮游植物营养物质可用性方面的作用。该方程还包括各种颗粒氮（N）分数（区分吸附氨氮与颗粒有机氮），以及 C 与 N 的比值，这表明沉积物中存在的有机物的不稳定性。溶解态可反应磷在淡水中也是一个重要指标。与传统监测颗粒营养物的方法（例如颗粒氮和颗粒磷）相比，这些指标在评估生物可利用性潜力方面表现更好。浮游植物生物测定表明，沉积物中的营养物质可以促进浮游植物生长，营养物质的生物可利用性不仅取决于沉积物负荷，还取决于与母土相关的沉积物特征。这些特征随土壤类型、土地利用和侵蚀过程而变化。研究结果将有助于优先控制侵蚀，优先考虑那些最有可能向大堡礁输送大量生物可用颗粒营养物的集水区。
