Deciphering the ecology of key diatom taxa to understand climate-induced changes in West Greenland lakes

在整个北极地区，古湖泊学记录提供了一些记录该地区全新世生态变化速率的少数关键档案。特别是，硅藻群落（一种对环境变化反应迅速的藻类，在湖泊沉积物中留下化石）在过去150年里发生了惊人的变化，在沉积物记录中，与温暖环境有关的物种以前所未有的速度增加。然而，西格陵兰湖沉积物中硅藻组合的变化与北极其他地区不同，因为它们在整个全新世都富含这些“温暖”的水硅藻。这种差异提出了一些问题，即我们可以利用硅藻在北极推断什么，并表明有必要澄清关键硅藻类群的生态特征，以促进我们对变化驱动因素的理解。最近在高寒地区的研究表明，作为20世纪北极和高寒湖泊变暖指标的关键硅藻物种对气候引起的湖泊生态系统能量（混合深度）和物质输入（营养物质）的变化都有特殊反应。这表明，气候引起的湖泊物理和化学结构变化之间的空间和时间变量相互作用可能驱动硅藻群落的变化，但目前尚未在北极湖泊中进行测试。这项研究将把比较湖泊取样与小型和大型实验相结合，以提供关键的生态信息，从而能够从格陵兰西南部的几个现有硅藻记录中解释气候引起的生态变化。该项目的目的是确定气候驱动的营养物和水柱稳定性变化对关键硅藻类群相对丰度的影响，并将这些信息应用于现有硅藻记录，以确定这些湖泊生态系统中气候引起的变化。将对一系列湖泊进行采样，以确定控制关键硅藻物种分布的因素。将进行一项小规模实验，以评估营养物和孵育深度对这些关键硅藻物种丰度的重要性。为了评估热分层对这些硅藻的重要性，将进行一项大规模的实验（全湖操纵），该实验将通过加深夏季典型热分层的湖泊混合层来测试。这一大规模实验将是第一次对整个湖泊生态系统进行测试，以确定能量流入变化对这些北极湖泊群落结构的重要性。该项目将为缅因大学气候变化研究所的一名博士后研究员提供支持。该博士后将获得开展北极生态系统研究、指导本科生以及在气候变化多个方面的多学科研究所工作的宝贵经验。这项研究还将涉及两名本科生在项目过程中。将与来自四个国家的生态学家共同开发和教授一个以气候变化和高纬度和高海拔湖泊生态系统为重点的分布式研究生研讨会。该项目的数据将通过NOAA古气候数据库和网站以及硅藻古湖泊数据合作网站提供。

Across the Arctic, paleolimnological records provide some of the few key archives documenting rates of ecological change in this region over the Holocene. In particular, striking changes in communities of diatoms (a type of algae that responds rapidly to environmental change and leaves a fossil in lake sediments) have occurred over the last 150 years, with species generally associated with warmer conditions increasing at unprecedented rates in the sediment record. However, changes in diatom assemblages in lake sediments from west Greenland are different from those in the rest of the Arctic in that they are rich in these 'warmer' water diatoms throughout the Holocene. This difference has raised questions about what we can use diatoms to infer in the Arctic, and suggests the need to clarify the ecological traits of key diatom taxa in order to advance our understanding of drivers of change. Recent research in alpine regions reveals that key diatom species that are used as indicators of 20th century warming in both arctic and alpine lakes respond specifically to both climate-induced changes in energy (mixing depths) and mass inputs (nutrients) to lake ecosystems. This suggests that spatially- and temporally-variable interactions between climate-induced changes in the physical and chemical structure of lakes may drive diatom community changes, but this is currently untested in arctic lakes.This research will couple comparative lake sampling with both small- and large-scale experiments to provide key ecological information that will enable interpretation of climate- induced ecological changes from several existing diatom records from southwest Greenland. The objective of this project is to determine the effects of climate-driven changes in nutrients and water column stability on the relative abundances of key diatom taxa, and to apply that information to existing diatom records to determine climate-induced changes in these lake ecosystems. A suite of lakes will be sampled to determine the factors controlling the distributions of key diatom species. A small-scale experiment will be conducted to assess the importance of nutrients and incubation depth on the abundances of these key diatom species. A large-scale experiment (whole lake manipulation) will be conducted to assess the importance of thermal stratification on these diatoms, which will be tested by deepening the mixed layer of a lake that typically stratifies thermallyduring the summer. This large-scale experiment will be the first whole-lake ecosystem test of the importance of changing energy influx on the community structure of these arctic lakes.This project will provide support for a postdoctoral research associate at the Climate Change Institute at the University of Maine. The postdoctoral associate will gain valuable experience conducting arctic ecosystems research, mentoring undergraduate students, and working in a multidisciplinary institute focused on multiple aspects of climate change. This research will also involve two undergraduates over the course of the project. A distributed graduate seminar focused on climate change and high latitude and altitude lake ecosystems will be developed and taught in conjunction with ecologists from four countries. Data from this project will be made available through the NOAA paleoclimate database and website, and the Diatom Paleolimnology Data Cooperative website.