Department of Aquatic Ecology, Netherlands Institute of Ecology, Wageningen, The Netherlands.
Department of Aquatic Ecology, Netherlands Institute of Ecology, Wageningen, The Netherlands; Aquatic Ecology and Water Quality Management Group, Wageningen University, The Netherlands.
Harmful Algae. 2017 Mar;63:146-153. doi: 10.1016/j.hal.2017.02.004. Epub 2017 Mar 1.
Harmful algal blooms (HABs) are globally expanding, compromising water quality worldwide. HAB dynamics are determined by a complex interplay of abiotic and biotic factors, and their emergence has often been linked to eutrophication, and more recently to climate change. The dinoflagellate Alexandrium is one of the most widespread HAB genera and its success is based on key functional traits like allelopathy, mixotrophy, cyst formation and nutrient retrieval migrations. Since 2012, dense Alexandrium ostenfeldii blooms (up to 4500cellsmL) have recurred annually in a creek located in the southwest of the Netherlands, an area characterized by intense agriculture and aquaculture. We investigated how physical, chemical and biological factors influenced A. ostenfeldii bloom dynamics over three consecutive years (2013-2015). Overall, we found a decrease in the magnitude of the bloom over the years that could largely be linked to changing weather conditions during summer. More specifically, low salinities due to excessive rainfall and increased wind speed corresponded to a delayed A. ostenfeldii bloom with reduced population densities in 2015. Within each year, highest population densities generally corresponded to high temperatures, low DIN:DIP ratios and low grazer densities. Together, our results demonstrate an important role of nutrient availability, absence of grazing, and particularly of the physical environment on the magnitude and duration of A. ostenfeldii blooms. Our results suggest that predicted changes in the physical environment may enhance bloom development in future coastal waters and embayments.
有害藻华（HABs）在全球范围内不断扩张，对全球水质造成影响。HAB 的动态受非生物和生物因素的复杂相互作用决定，其出现通常与富营养化有关，最近则与气候变化有关。甲藻属的亚历山大藻是分布最广泛的 HAB 属之一，其成功基于关键的功能特征，如化感作用、混合营养、休眠孢囊形成和营养物质回收迁移。自 2012 年以来，荷兰西南部的一条小溪中每年都会出现密集的亚历山大藻（高达 4500cellsmL）水华，该地区以集约化农业和水产养殖业为特征。我们研究了物理、化学和生物因素如何影响 A. ostenfeldii 水华动态，研究时间为连续三年（2013-2015 年）。总的来说，我们发现随着时间的推移，水华的规模有所减少，这主要与夏季天气条件的变化有关。更具体地说，由于降雨量过多和风速增加导致的低盐度，与 2015 年亚历山大藻水华延迟和种群密度降低有关。在每年内，最高的种群密度通常与高温、低 DIN:DIP 比和低摄食者密度相对应。总之，我们的结果表明，营养物质的可用性、缺乏摄食者以及特别是物理环境对 A. ostenfeldii 水华的规模和持续时间起着重要作用。我们的研究结果表明，预测的物理环境变化可能会增强未来沿海水域和港湾的水华发展。
