Can micro- or mesozooplankton control phytoplankton spring blooms in the Baltic Proper under climate warming?

在气候变暖的情况下，微型或中型浮游生物能否控制波罗的海本岸春季浮游植物的大量繁殖？

• 批准号: 426620852
• 负责人: Dr. Carolin Paul
• 金额: --
• 依托单位: Sektion Biologische Meereskunde
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/426620852?language=en
• 关键词: micro; mesozooplankton; control; phytoplankton; spring

Climate warming is predicted to increase the water surface temperature of the Baltic Sea by 2-3°C and was already up 2°C higher in 2016 compared to the long-term average (HELCOM 2017) in the Baltic Proper (Arkona and Gotland Sea). Since the late 1980s a dramatic decrease of the diatom standing stock and the change to a dominance of autotrophic dinoflagellates in the Baltic Proper have been observed. According to Wasmund et al. (2017), the only reason should be climate warming i.e. higher water temperatures. It is hypothesized that earlier development of the mesozooplankton (copepods, rotifers) and microzooplankton (ciliates, heterotrophic dinoflagellates) due to milder winter temperatures lead to intensified grazing on the early stages of the spring bloom, which are represented by small diatoms, e.g. Skeletonema marinoi, and explain its decreased abundances during the last decades. However, the described interrelations are still poorly understood and are totally unclear for the Baltic Proper. Notably, microzooplankton is not monitored in detail in the Baltic Proper and the infrequent monitoring cruises to the Baltic Proper in February, March and May still leave large gaps in the plankton biomass knowledge during spring bloom, all of which do not allow to confirm the proposed top-down scenarios. Thus, I will combine high-frequency monitoring of the whole plankton community with ship-based temperature-manipulated field experiments and culture studies to a) provide high resolution data of plankton community dynamics and b) assess the mechanistic link between increased water temperature, zooplankton community changes and the significant decrease in diatom biomass during the spring bloom in the Baltic Proper. In ship-based experiments during project cruise (April 2020), the effects of grazing will be researched by including a natural zooplankton community of only microzooplankton in one part of the experiment as well as by a community comprising micro- and mesozooplankton (natural and doubled abundance) in a second set-up under ambient and +3°C enhanced temperature regimes. A sub dilution experiment will be done to identify and select microzooplankton grazing rates. Further, with the help of monitoring (part B), the spring bloom plankton community dynamics and species composition will be researched. It should be proved if microzooplankton and mesozooplankton are already abundant in quantities able to control the diatom standing stock during phytoplankton spring bloom. Phytoplankton, microzooplankton and mesozooplankton samples will be taken at our own project cruise in the 1st half of April 2020, during IOW regular monitoring cruises (February, March, May) and in co-operation with a cruise of GEOMAR in the 2nd half of April of the same year. In laboratory experiments (part C), the effects of climate warming and key grazers will be analysed in more detail on species level using plankton cultures.

预计气候变暖将使波罗的海的水面温度升高2-3°C，与波罗的海（Arkona和Gotland海）的长期平均值（HELCOM 2017）相比，2016年已经高出2°C。自20世纪80年代末以来，硅藻现存量急剧下降，并在波罗的海海域发生了由自养甲藻占主导地位的变化。根据Wasmund等人（2017）的说法，唯一的原因应该是气候变暖，即水温升高。据推测，早期发展的中型浮游动物（桡足类，轮虫）和微型浮游动物（纤毛虫，异养甲藻）由于温和的冬季温度导致加强放牧的早期阶段的春季水华，这是由小硅藻，如海洋硅藻，并解释其减少丰度在过去的几十年。然而，所描述的相互关系仍然知之甚少，对波罗的海本身完全不清楚。值得注意的是，波罗的海地区没有对微型浮游动物进行详细监测，而且二月、三月和五月对波罗的海地区进行的不频繁的监测巡航仍然在春季水华期间的浮游生物生物量知识方面留下了很大的差距，所有这些都无法确认提出的自上而下的场景。因此，我将结合联合收割机高频监测整个浮游生物群落与船舶温度控制的现场实验和文化研究，以a）提供高分辨率的浮游生物群落动态数据和B）评估之间的机械联系水温升高，浮游动物群落的变化和硅藻生物量的显着减少在春季水华在波罗的海适当。在项目巡航期间（2020年4月）的船基实验中，将通过在实验的一部分中包括仅微型浮游动物的天然浮游动物群落以及在环境温度和+3 ° C增强温度制度下的第二个设置中包括微型和中型浮游动物（自然和加倍丰度）的群落来研究放牧的影响。将进行亚稀释实验以识别和选择微型浮游动物摄食率。此外，在监测（B部分）的帮助下，将研究春季水华浮游生物群落动态和物种组成。应该证明，如果微型浮游动物和中型浮游动物已经丰富的数量能够控制硅藻常备库存在浮游植物春季水华。浮游植物，微型浮游动物和中型浮游动物样本将在2020年4月上半月的IOW定期监测巡航（2月，3月，5月）期间在我们自己的项目巡航中采集，并与同年4月下半月的GEOMAR巡航合作。在实验室实验（C部分）中，将利用浮游生物培养在物种一级更详细地分析气候变暖和主要食草动物的影响。