REMEMBER: REsponses of neotropical freshwater ecosysteMs to climatE and environMental disturBance in the Mayan Region of Mexico during the Common Era

拟议的“记住”项目将生成关于生物多样性变化以及共同时代期间恰帕斯拉坎登森林中海拔和墨西哥南部昆塔纳鲁奥低地淡水生态系统历史发展和反应的高分辨率(十年、百年)数据。我们将联合分析10个岩溶湖泊短沉积物岩芯中的摇蚊、介形虫和脂肪生物标记物，这些岩芯跨越海拔(~1000毫升)和营养状态(少营养、中营养和富营养)梯度，以推断墨西哥玛雅地区气候和环境变化的影响和原因。选定的地点和时间间隔是一项自然实验，目的是(1)研究淡水类群相对丰度的时间和空间变化，(2)估计哥伦布前时期、欧洲征服后和近代水生群落变化的幅度和速度。脂质生物标记物分析的一个重点将放在蓝藻上，因为它们经常形成有害的蓝藻水华(蓝藻水华)，通过产生肝毒素，可能对湖泊生态系统和居民产生负面影响。虽然附近其他新热带地区的一些早期研究调查了蒸发和降水平衡(E/P)的历史变化，但对过去发生的例如小冰期(LIA)期间的气温和水温变化知之甚少。因此，我们选择摇蚊和类脂古温度计(HDI26)来推断不同海拔的空气和地表水温度，因为它们代表了敏感和可靠的温度代理。为了补充这些研究，我们还将使用介形虫外壳中的氧和碳同位素值作为蒸发和降水、温度和生产力变化的替代指标，并将使用MBT‘5ME来确定年平均气温的变化。LIA之前的花粉研究报告说，大约2-3℃的“轻微”但重要的降温深刻地改变了北热带地区的陆地植物群落。然而，对水生生态系统的影响还没有得到深入的研究，这将是本研究的重点。生成的数据将使我们能够推断北热带大陆的温度和E/P变化，并将其与其他古气候档案的结果进行比较，包括洞穴、海洋沉积物和珊瑚，以了解该地区已报告但仍有待解决的不同气候信号和响应。因此，记住将(1)为在全球气候数据库中代表性较差的热带地区提供过去2000年的高分辨率温度时间序列，(2)为墨西哥南部淡水生态系统的养护和管理作出贡献。

The proposed REMEMBER project will generate high-resolution (decadal, centennial) data on biodiversity change and the historical development and response of freshwater ecosystems during the Common Era in the mid-elevations of the Lacandon Forest, Chiapas and in the lowlands of Quintana Roo, southern Mexico. We will jointly analyze chironomids, ostracodes and lipid biomarkers in 10 short sediment cores from karst lakes across an altitude (~1000 masl) and trophic state (oligo-, meso- and eutrophic) gradient to infer the effects and causes of climate and environmental change in the Maya region of Mexico. The selected locations and time intervals serve as a natural experiment to (1) study temporal and spatial changes in the relative abundance of freshwater taxa and (2) estimate the magnitude and velocity of changes in aquatic communities during the Pre-Columbian period, after European conquest, and during recent times. One focus of the lipid biomarker analyses will be placed on cyanobacteria as these frequently form harmful cyanobacterial blooms (cyanoHABs), which through the production of hepatotoxins, may negatively impact lake ecosystems and dwellers. Whereas some earlier studies in other nearby neotropical regions investigated historical shifts in the balance between evaporation and precipitation (E/P), little is known about air and water temperature changes that occurred in the past, e.g., during the Little Ice Age (LIA). Therefore, we chose chironomids and lipid paleothermometers (HDI26) to infer air and surface water temperatures at different elevations as they represent sensitive and reliable temperature proxies. To complement these lines of research, we will also use oxygen and carbon isotope values in ostracode shells as proxies for changes in evaporation and precipitation, temperature and productivity, and we will determine changes in mean annual air temperature using the MBT’5Me. Previous pollen studies for the LIA report that the “slight” but important cooling of about 2-3°C profoundly modified terrestrial plant communities in the northern Neotropics. However, the effect on aquatic ecosystems has not been investigated in depth and will be focus of this study. The generated data will enable us to infer temperature and E/P changes in the continental northern Neotropics, which will be compared with results from other paleoclimate archives, including speleothems, marine sediments and corals to understand the heterogeneous climate signals and responses that have been reported in the region but that yet remain to be resolved. Thus, REMEMBER will (1) provide high-resolution temperature time series over the last 2000 years for a tropical region that has been poorly represented in global climate databases, and (2) serve as a contribution to the conservation and management of freshwater ecosystems of southern Mexico.