Instituto de Ciencias de la Tierra, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile.
Departamento de Ecología y Biodiversidad, Facultad de Ecología y Recursos Naturales, Universidad Andres Bello, Santiago, Chile.
Ambio. 2019 Mar;48(3):304-312. doi: 10.1007/s13280-018-1071-6. Epub 2018 Jul 3.
In mid-2004, anthropogenically induced changes in water quality of the Río Cruces wetland, a Ramsar site located in southern Chile (ca. 40°S), enhanced the resuspension of iron-enriched sediments, which were subsequently deposited over the most abundant aquatic macrophyte of the wetland (Egeria densa Planch. 1849). This event triggered the formation of brownish, necrotic patches and increased iron contents in the leaves and stems of E. densa, which contributed to a significant demise of the plant within the wetland. In this study, we estimate the recovery time as a proxy for resilience of this macrophyte at organismal and population levels. Macro- and micro-optical characteristics, as well as iron contents in tissues of E. densa, were documented in four time windows (2004, 2008, 2012, and 2014). In addition, the size of the macrophyte population and its spatial occurrence were monitored from 2008 to 2016 across 36 study sites within the wetland. Our results suggest necrotic patches and high iron contents in E. densa persisted at least until 2008. After 2013, a significant increase in the spatial occurrence of E. densa was observed within the wetland, reaching full recovery of the population during 2015. The health of plant tissues and iron contents in leaves and stems showed recovery period close to 4 years, while the recovery of the spatial occurrence of E. densa took approximately 9 years. While the monitoring of plant health was not performed on a strict annual basis, the recovery rates estimated here are slower than those described for other macrophytes. This finding might reflect the long-lasting effects of the disturbance from 2004 and the interaction with biotic processes, such as foraging by waterbirds recolonizing the Río Cruces wetland. These results show that full recovery of E. densa was achieved through a cascade of effects starting with abiotic factors (water quality) and passing through physiological and individual levels, to finally reach the population level. A key aspect of this response is the invasive nature of the macrophyte, which likely contributed to its recovery as a consequence of improved water quality. Less successful macrophyte species in other systems may not reach the specific population recovery, and become subdominant species instead, or even be eradicated from the wetland either as the result of herbivory or due to competition with other macrophytes.
2004 年年中，人为改变智利南部（约南纬 40°）克鲁塞斯湿地的水质，使富含铁的沉积物重新悬浮，随后在该湿地最丰富的水生植物——埃杰里亚·登萨（Egeria densa Planch. 1849）上沉积。这一事件引发了棕褐色、坏死斑块的形成，并增加了埃杰里亚·登萨叶片和茎中的铁含量，导致该植物在湿地内大量死亡。在这项研究中，我们通过估算生物个体和种群的恢复时间来评估该水生植物的弹性。在四个时间窗口（2004 年、2008 年、2012 年和 2014 年），我们记录了埃杰里亚·登萨的宏观和微观光学特征以及组织中的铁含量。此外，我们还在 2008 年至 2016 年期间，在湿地的 36 个研究点监测了该水生植物的种群规模及其空间分布。我们的结果表明，埃杰里亚·登萨的坏死斑块和高铁含量至少持续到 2008 年。2013 年以后，湿地内埃杰里亚·登萨的空间分布显著增加，2015 年种群完全恢复。叶片和茎组织的健康状况以及铁含量的恢复时间接近 4 年，而埃杰里亚·登萨的空间分布的恢复时间约为 9 年。虽然对植物健康的监测不是严格按年度进行的，但这里估计的恢复速度比其他大型植物慢。这一发现可能反映了 2004 年干扰的长期影响，以及与生物过程的相互作用，例如水鸟在克鲁塞斯湿地重新出现后的觅食行为。这些结果表明，埃杰里亚·登萨的完全恢复是通过一系列从非生物因素（水质）开始，通过生理和个体水平，最终到达种群水平的影响而实现的。这种反应的一个关键方面是大型植物的入侵性质，这可能是由于水质改善而促进了其恢复。在其他系统中，不太成功的大型植物物种可能无法达到特定的种群恢复，而是成为次优势物种，甚至由于食草或与其他大型植物的竞争而从湿地中被消灭。
