Programa de Pós-graduação em Ecologia de Ambientes Aquáticos Continentais, Universidade Estadual de Maringá, Maringá, PR, Brazil.
Departament of Oceanography and Limnology, Universidade Federal do Rio Grande do Norte, Natal, RN 59014-002, Brazil.
Sci Total Environ. 2024 May 10;924:171621. doi: 10.1016/j.scitotenv.2024.171621. Epub 2024 Mar 11.
A positive feedback loop where climate warming enhances eutrophication and its manifestations (e.g., cyanobacterial blooms) has been recently highlighted, but its consequences for biodiversity and ecosystem functioning are not fully understood. We conducted a highly replicated indoor experiment with a species-rich subtropical freshwater phytoplankton community. The experiment tested the effects of three constant temperature scenarios (17, 20, and 23 °C) under high-nutrient supply conditions on community composition and proxies of ecosystem functioning, namely resource use efficiency (RUE) and CO fluxes. After 32 days, warming reduced species richness and promoted different community trajectories leading to a dominance by green algae in the intermediate temperature and by cyanobacteria in the highest temperature treatments. Warming promoted primary production, with a 10-fold increase in the mean biomass of green algae and cyanobacteria. The maximum RUE occurred under the warmest treatment. All treatments showed net CO influx, but the magnitude of influx decreased with warming. We experimentally demonstrated direct effects of warming on phytoplankton species sorting, with negative effects on diversity and direct positive effects on cyanobacteria, which could lead to potential changes in ecosystem functioning. Our results suggest potential positive feedback between the phytoplankton blooms and warming, via lower net CO sequestration in cyanobacteria-dominated, warmer systems, and add empirical evidence to the need for decreasing the likelihood of cyanobacterial dominance.
一个正反馈循环，其中气候变暖增强了富营养化及其表现形式（例如蓝藻水华），最近受到了关注，但它对生物多样性和生态系统功能的影响还不完全清楚。我们进行了一项具有高度复制性的室内实验，使用了一个物种丰富的亚热带淡水浮游植物群落。该实验测试了在高养分供应条件下，三种恒定温度情景（17、20 和 23°C）对群落组成和生态系统功能指标（即资源利用效率（RUE）和 CO 通量）的影响。32 天后，变暖降低了物种丰富度，并促进了不同的群落轨迹，导致中温下绿藻占优势，高温下蓝藻占优势。变暖促进了初级生产力，绿藻和蓝藻的平均生物量增加了 10 倍。最高温度处理下的最大 RUE 出现。所有处理均显示净 CO 流入，但随着变暖，流入量减少。我们通过实验证明了变暖对浮游植物物种分选的直接影响，对多样性有负面影响，对蓝藻有直接的积极影响，这可能导致生态系统功能发生潜在变化。我们的结果表明，浮游植物水华和变暖之间存在潜在的正反馈，在以蓝藻为主、温度较高的系统中，净 CO 固存减少，这增加了减少蓝藻优势的必要性的经验证据。
