Nutrient cycling analysis of anthropogenically influenced subtropical coastal ecosystems with a focus on pH-dependent phosphorus species compositions, distributions and transformations

由于沿海生态系统的货物和服务的价值及其日益受到人为干扰的威胁，制定可持续性建议至关重要。为了实现改善，这是必不可少的，以了解沿海养分循环的过程，特别是磷（P）的动态。为了深入了解磷循环，有必要评估磷的形态和转化，其控制相关因素和人类影响的变化。该项目调查了新西兰泰晤士河河口的营养循环。这一大型海洋海湾的沿海生态系统受到沉积物和营养物质输入的影响，由于广泛的农业集水盆地，造成明显的快速红树林在过去几十年的向海扩张。目的是确定该磷富集区的磷形态和转化控制相关的沉积物性质。这将有助于更好地理解磷污染的有害影响的原因和磷富集和形态在红树林扩张中的作用。由于沉积磷物种的pH依赖性很强，沿沿着过渡的普遍pH梯度和海洋酸化导致的营养物形态变化的不确定性，本研究将侧重于单个磷物种的pH依赖性。对于这种方法，以前开发的P物种定量的方法将被使用，同时改进。具体目标是评估（一）pH值和氧化还原电位对养分限制和磷的形态，转化和可用性的影响;（二）时间pH值的变化对磷的形态和转化的影响;（三）不同生态系统之间的磷形态差异;（四）磷的形态对磷径流，有效性和吸收的影响。结论将支持建模方法和比较与P形态评估早期的研究。

Due to the value of goods and services from coastal ecosystems and their increasing threat by anthropogenic perturbations, the development of sustainability recommendations is of immense importance. To achieve improvements, it is essential to understand processes of coastal nutrient cycling, especially of phosphorus (P) dynamics. For gaining insight into the P cycle, it is necessary to assess P speciations and transformations, their control by relevant factors and changes by human impacts. The project investigates nutrient cycling at New Zealand’s Firth of Thames. Coastal ecosystems of this large marine embayment are influenced by sediment and nutrient inputs due to an extensive agricultural catchment basin that caused obviously a rapid mangrove seaward expansion during the past decades. The aim is to determine the P speciation and transformation control of this P enriched region by relevant sediment properties. This can contribute to a better understanding of causes for detrimental effects of diffuse P pollution and the role of P enrichment and speciation in mangrove expansion. Due to the strong pH dependency of sedimentary P species, prevailing pH gradients along coastal transitions and current uncertainties of nutrient speciation changes by ocean acidification, this study will focus on the pH dependency of individual P species. For this approach, a previously developed method for P species quantification will be used and simultaneously improved. Specific objectives are to assess (i) pH and redox potential effects on nutrient limitations and on P speciation, transformation and availability; (ii) effects of temporal pH changes on P speciation and transformation; (iii) P speciation differences among different ecosystems; (iv) P speciation effects on P runoff, availability and uptake. Conclusions will be supported by modeling approaches and comparisons with P speciation assessments of earlier studies.