School of Sciences, Psychology and Sport, Federation University Australia, Mt. Helen, VIC, 3350, Australia.
Water, Environment and Agriculture Program, Department of Infrastructure Engineering, The University of Melbourne, Victoria, 3010, Australia.
Sci Rep. 2020 Jul 31;10(1):12955. doi: 10.1038/s41598-020-69829-8.
Large rivers, including the Murray River system in southeast Australia, are disturbed by many activities. The arrival of European settlers to Australia by the mid-1800s transformed many floodplain wetlands of the lower Murray River system. River impoundment and flow regulation in the late 1800s and, from the 1930s, resulted in species invasion, and elevated nutrient concentrations causing widespread eutrophication. An integrated palaeoecology, and palaeo-and-modern food web approach, incorporating mixing models, was undertaken to reveal changes in a regulated wetland (i.e. Kings Billabong). The lack of preserved sediment suggests the wetland was naturally intermittent before 1890. After this time, when used as a water retention basin, the wetland experienced net sediment accumulation. Subfossil cladocerans, and δC of Daphnia, chironomid, and bulk sediment, all reflected an early productive, likely clear water state and shifts in trophic state following river regulation in the 1930s. Food web mixing models, based on δC and δN in subfossil and modern Daphnia, fish, and submerged and emergent macrophytes, also indicated a shift in the trophic relationships between fish and Daphnia. By the 1970s, a new state was established but a further significant alteration of nitrogen and carbon sources, and trophic interactions, continued through to the early 2000s. A possible switch from Daphnia as a prey of Australian Smelt could have modified the food web of the wetland by c. 2006. The timing of this change corresponded to the expansion of emergent macrophytes possibly due to landscape level disruptions. The evidence of these changes suggests a need for a broader understanding of the evolution of wetlands for the management of floodplains in the region.
大型河流，包括澳大利亚东南部的墨累河流域，受到许多活动的干扰。19 世纪中叶欧洲移民的到来，改变了墨累河流域下游许多洪泛平原湿地。19 世纪后期的河道蓄水和流量调节，以及从 20 世纪 30 年代开始的物种入侵和营养物质浓度升高，导致了广泛的富营养化。本研究采用古生态学、古-现代食物网方法，结合混合模型，揭示了一个受调控湿地（即金斯塘）的变化。由于缺少保存完好的沉积物，表明该湿地在 1890 年前是自然间歇性的。在此之后，当作为一个水保留池使用时，湿地经历了净沉积物积累。亚化石介形类动物、δC 的溞类、摇蚊和总沉积物，都反映了一个早期的生产力、可能是清澈的水状态，以及 20 世纪 30 年代河流调节后的营养状态变化。基于亚化石和现代溞类、鱼类、沉水和挺水植物的 δC 和 δN 的食物网混合模型，也表明了鱼类和溞类之间的营养关系发生了转变。到 20 世纪 70 年代，建立了一个新的状态，但直到 21 世纪初，氮和碳源以及营养相互作用的进一步显著改变仍在继续。澳大利亚胡瓜鱼作为猎物的转变，可能在 2006 年左右改变了湿地的食物网。这种变化的时间与可能由于景观水平干扰而扩张的挺水植物的时间相对应。这些变化的证据表明，需要更广泛地了解湿地的演变，以管理该地区的洪泛平原。
