报告摘要：
Global climate change is predicted to reduce nutrient fluxes into the photic zone, particularly in tropical and subtropical ocean gyres, while the occasional major storms will result in increased nutrient pulses. In this study the nutrient and phytoplankton dynamics have been determined at a new time-series station in the southeastern Levantine basin of the P depleted Eastern Mediterranean Sea (EMS) over 4.5 years (2017-2022). Our results predict that climate change in the EMS will result in increased periods of nutrient and phytoplankton depletion (Famine) interrupted by short periods of Mesotrophy (Feast) caused by major storms.
Conventional methods of determining nutrient limitation in this P depleted oligotrophic system were problematic. In-situ measurements of nitrate: phosphate ratio at times gave artificially high ratios because Phosphate was always at or close to limit of detection (LoD) due to rapid uptake by cyanobacteria into their periplasm. This resulted in unexpected results during our CYCLOPS Lagrangian P addition experiment in 2003, in which Chlorophyll decreased as a result of increased plankton grazing. The conventional 48h nutrient limitation experiments with Chlorophyll as the endpoint always showed N&P colimitation because Chlorophyll was formed and stored while growth which depends on P to form DNA was delayed. Using a combination of observations including a nutrient limitation experiment with APA as the endpoint, we found that the ecosystem was P limited in winter and gradually changed to N&P colimitation in summer as both N and P were lost from the photic zone. In summer the organisms produced APA to try to increase the bioavailable P pool by breaking down DOP.
报告人简介：
Micheal David Krom教授，海洋生物地球化学家，1971年获得剑桥皇后学院自然科学硕士学位，1976年获得爱丁堡大学格兰特地质研究所低温地球化学博士学位。2000年起至2015年任职为英国利兹大学地球科学学院环境与海洋地球化学教授，此后其任职为以色列海法大学海洋科学学院教授。Micheal David Krom教授主要从事大气尘埃、自然和污染水域以及近期沉积物中的养循环研究，其重点关注水生和沉积系统中的养分循环（P、N和Fe）的生物地球化学过程，研究区域不限于海洋环境。其致力于了解自然过程，以便识别和减轻人为变化的影响。其主要成果发表在Science, PNAS, Environmental Science and Technology, Geochim Cosmochim Acta, Water Research, Global Biogeochemical Cycles, Limnology and Oceanography, Progress in Oceanography, Analyst, Deep-Sea Research ll, American Journal of Science等国际重要的学术期刊上。
