Research Progress in Area 1 方向 ( 一 ) 課題進展 97 Abstract Plankton are unseen heroes in marine ecosystems with their irreplaceable roles in carbon sequestration and biogeochemical cycling and mediation of climate changes. Studying how plankton respond to environment changes at different time-scale is essential to understand and predict the impacts of climate changes. Prof. Liu leads a group with particular focus on plankton ecology and climate changes. They conducted a series of research including time seriesmonitoring, field and laboratory experiments. They mainly focus on the responses of the key functional groups (i.e., primary producers, nitrogen fixers and zooplankton) to the warming and other associated environmental stressors, covering both coastal and oceanic ecosystems. Research Activities and Progress • Proved “thermal adaptation compensation” in natural phytoplankton assemblages (Fig. 1); • Analyzed 18 years of historical phytoplankton and environmental data in Pearl River Estuary; • Studied the interactive effect of temperature elevation and P limitation on a marine diazotroph. • Studied the adaptation mechanisms of Synechococcus in mesoscale eddies; • Studied the role of gut microbes in zooplankton adaptation to poor prey quality and toxic nanoparticles; • Explored how the biogenic silica content of diatoms affects copepod grazing behaviors. Key Findings • We found “hotter is partially better” in natural phytoplankton communities. The short-term temperature sensitivity within communities was higher than that across communities; • Diatom/Dino ratio will further increase with increasing anthropogenic input and warming in subtropical urbanized estuarine ecosystem; • P limitation in diazotroph was relieved with elevated temperature through various temperaturedependent economic strategies of P metabolism; • Different abilities of organic nutrient utilization and chromatic acclimation explained the different distributions of the understudied subcluster 5.2 and 5.3 Synechococcus; • Gut microbes played important roles in helping zooplankton relieve N- and P-limitation and toxic effects of silver nanoparticles; • Nano-structure and chemical properties determine the mechanical strength of the diatom frustules, and subsequently influence copepod grazing behaviors. Other research activities: • Our team organized a research cruise, with 24 scientists from 8 laboratories on board, to the Pearl River Estuary and the South China Sea during the summer of 2021; • Our study on the diatom/dinoflagellate ratio under warming and increasing anthropogenic input gained extensive media attention and coverage, which increased the public awareness of marine environmental protection in Hong Kong. Research Output Publication 13 Trained personnel 19 Response and Adaptation of Marine Plankton Communities to Environmental Stresses in a Warming Ocean Prof. Hongbin Liu The Hong Kong University of Science and Technology Fig 1. "hotter is partially better" (Liu et al., 2021. L&O letters)
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