Understanding the dynamics of the phytoplankton spring bloom and predicting its fate and impact on marine ecosystems in the Arctic Ocean of tomorrow

了解浮游植物春季绽放的动态并预测其命运以及对未来北冰洋海洋生态系统的影响

• 批准号: RGPIN-2014-05175
• 负责人: Babin, Marcel
• 金额: $ 2.48万
• 依托单位: Université Laval
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=630208
• 关键词: Understanding; dynamics; phytoplankton; spring; bloom

In most parts of the World Ocean, the phytoplankton spring bloom (PSB) provides a large fraction of the annual primary production (PP) and, most importantly, nearly all of the new PP exportable through the food chain and toward the bottom sediments. In the Arctic Ocean (AO) the PSB often develops around the ice-edge. This highly transient phenomenon lasts about 3 weeks at any given location in the seasonal ice zone (SIZ) and accounts for most of the annual PP in the AO. The SIZ is currently increasing in size and may cover the entire AO as of the 2030s. Therefore, one may wonder whether ice-edge blooms will cover a much larger area than they used to through a significant northward expansion. If so, what will be the fate of this additional phytoplankton biomass build-up along the retreating ice cover. Will it sustain higher secondary production and trophic transfer in the pelagic food web, thus benefiting megafauna? Or will it sink rapidly and create new benthic hotspots, possibly contributing increased carbon sequestration in the sediment? The overarching goal of the present project is to understand the processes that control the Arctic PSB as it expands northward and to determine its fate in the ecosystem by investigating its related carbon fluxes. The short-term objective of this project is to understand the dynamics of the Arctic PSB and, more specifically, how it is controlled by physical and chemical properties of the upper ocean and by phytoplankton species succession during the bloom. The long-term objective is to determine the fate of the PSB in a changing AO. We hypothesize that PP at high latitudes will increase in the coming decades because of a northward expansion of the SIZ and an intensification of the phytoplankton spring bloom. Changes in the phytoplankton phenology may have profound consequence on the entire ecosystem and food chain.A PSB event will be monitored in Baffin Bay from its onset under melting ice in May to its conclusion in the SIZ in July. Relevant physical, chemical and biological properties will be described at various scales using profiling floats, gliders and an autonomous underwater vehicle, equipped with physical and bio-optical sensors. Process studies will be conducted to document phytoplankton growth, nutrient assimilation and carbon transfer through the food web and towards the sediment. Key phytoplankton species will be isolated and grown under laboratory conditions to model their species succession and response to environmental factors. We will use ocean color remote sensing to thoroughly study the Arctic PSB, the full phenology of phytoplankton biomass, as well as transient phytoplankton blooms triggered by forcing events such as shelf-break upwellings. The optical properties of seawater in the vicinity of the ice edge and their variations during the spring bloom will be used to optimize our ocean colour algorithms and we will establish a time series of pan-Arctic PP over the period for which remotely sensed ocean colour data are available. Finally, a coupled physical-biological model will be optimized to simulate the Arctic PSB and predict changes in phytoplankton communities and food web dynamics over a variety of temporal scales.The project is an unprecedented effort for gaining a mechanistic understanding of the PSB in the AO through the use of state-of-the-art field and laboratory observation technologies, remote sensing of ocean colour and sophisticated modelling tools. The Knowledge gained from this project will expand our observational capacity and knowledge of the rapid changes taking place in Arctic ecosystems.

在世界海洋的大部分地区，浮游植物春季繁殖（PSB）提供了大部分的年度初级产量（PP），最重要的是，几乎所有的新PP都可以通过食物链输出并流向底部沉积物。在北冰洋（AO）， PSB常在冰缘附近发展。这种高度瞬变的现象在季节性冰带（SIZ）的任何给定位置持续约3周，占AO年PP的大部分。该区域目前正在扩大，到本世纪30年代可能覆盖整个亚太地区。因此，人们可能会想，通过向北的显著扩张，冰边华是否会覆盖比以往更大的区域。如果是这样的话，沿着消退的冰盖堆积起来的这些额外的浮游植物的命运将会怎样呢？它能否维持更高的次生产量和中上层食物网的营养转移，从而使巨型动物受益？或者它会迅速下沉并产生新的底栖热点，从而可能增加沉积物中的碳固存？本项目的总体目标是了解控制北极PSB向北扩展的过程，并通过调查其相关的碳通量来确定其在生态系统中的命运。该项目的短期目标是了解北极PSB的动态，更具体地说，它是如何受到上层海洋的物理和化学特性以及浮游植物物种在水华期间的演代的控制的。长期目标是确定PSB在不断变化的AO中的命运。我们假设未来几十年高纬度地区的PP将会增加，这是由于SIZ向北扩展和浮游植物春季华的加剧。浮游植物物候的变化可能对整个生态系统和食物链产生深远的影响。将监测巴芬湾从5月在融化的冰下开始到7月在特别经济区结束的PSB事件。相关的物理、化学和生物特性将在各种尺度上使用剖面浮标、滑翔机和配备物理和生物光学传感器的自主水下航行器进行描述。将进行过程研究，以记录浮游植物的生长、营养物质的同化以及通过食物网向沉积物的碳转移。关键的浮游植物物种将被分离并在实验室条件下生长，以模拟它们的物种演替和对环境因素的响应。我们将利用海洋颜色遥感技术深入研究北极PSB、浮游植物生物量的完整物候，以及由陆架断裂上升流等强迫事件引发的短暂浮游植物大量繁殖。冰缘附近海水的光学特性及其在春季水华期间的变化将被用于优化我们的海洋颜色算法，我们将在遥感海洋颜色数据可用的时间段内建立泛北极PP时间序列。最后，将优化一个物理-生物耦合模型来模拟北极PSB，并预测各种时间尺度上浮游植物群落和食物网动态的变化。该项目是一项前所未有的努力，旨在通过使用最先进的实地和实验室观测技术、海洋颜色遥感和复杂的建模工具，从机制上了解AO中的PSB。从该项目中获得的知识将扩大我们对北极生态系统正在发生的快速变化的观测能力和知识。