I. Nonlinear dynamics
Being able to forecast into future is one of the ultimate goals of science. If so, conversely, forecast capability may be used effectively to examine system dynamics. Based on out-of-sample forecast skill, we employ nonlinear time series techniques to investigate system dynamics. These methods are rooted in the theory of state-space reconstruction of the system attractor. These techniques have ability to distinguish low-dimensional nonlinear dynamics from high-dimensional linear noise in natural time series. Using these nonlinear methods, we investigated potential catastrophes of ecosystems, characterized neural feedback control of flying behavior of drosophila, and determined the relative contributions of intrinsic and extrinsic processes to the regulation of biological populations. The methods are being further developed to investigate the possible abrupt ecosystem change in response to climate change. These methods were originally developed by my Ph.D. advisor George Sugihara (Scripps Institution of Oceanography, USA). An on-line portal for these techniques is developed by Christian Anderson (Scripps Institution of Oceanography, USA). We also extended these techniques to deal with parallel short ecological time series, and more exciting methods specific for ecological data are coming! top
II. Fisheries
Separating the effects of environmental variability from the impacts of fishing has been elusive but is essential for sound fisheries management. As the fisheries management policy moved toward an ecosystem approach, it is important to understand interactive effects of fishing and climate. Using 50-year long fish time series data collected from the California Cooperative Oceanic Fisheries Investigations surveys, we developed a novel approach to examine fishing effects on fish populations within the context of a changing environment by comparing exploited to unexploited populations. We found that fishing had reduced resilience of fish populations facing environmental variability and elevated boom-and-bust of exploited populations. See our research on NEWS! We continue to investigate fishing effects on age structures of exploited populations from data, theoretical and field works aspects.top
III. Biological oceanography around Taiwan
Our research in biological oceanography around Taiwan is multi-faceted. Many oceanographers work together. Our recent focuses have been on:
- Climatic effects on the Taiwan Strait ecosystem (with Chih-Shin Chen and Tai-Sheng Chiu).
- The effects of Three-Gorges Dam on the East China Sea ecosystem (with a group leaded by Gwo-Ching Gong). We are the biggest oceanographic team in Taiwan. Our works include almost everything in the East China Sea ecosystem: physics, nutrients, primary production, zooplankton dynamics, ichthyoplankton assemblages, and fisheries management as well as all these effects on biogeochemical cycling and trace elements. We anticipate huge change in this ecosystem after the Three-Gorges Dam fully functions.
- Long-term variations of ichthyoplankton communities around Taiwan (with Wen-Bin Huang, Chih-Shin Chen and Tai-Sheng Chiu).
- Long-term variations of anchovy landings of Taiwan comparing to Japan and California (with Ming-anne Lee, Chih-Shin Chen, Tai-Sheng Chiu, and Akinori Takasuka).
- The effects of dust storms on the productivity of the oligotrophic subtropical ocean (with a group leaded by Gwo-Ching Gong).top
IV. Climate change and lake ecology
Understanding synergistic effects of climate change and anthropogenic impacts is a topical issue in lake systems. Using 40-year long phytoplankton, zooplankton, and fish time series data along with physical and chemical measurements, we study the effects of climate and eutrophication in Lake Biwa, Japan. This work has been carrying out with Youichirou Sakai, Norio Yamamura (Research Institute for Humanity and Nature, Japan), Michio Kumagai, and Kanako Ishikawa, Toshiyuka Ishikawa (LBERI, Japan).
Recently, I cooperate with Fuh-Kao Shiah (Academia Sinica) to work on zooplankton ecology in the Fei-Tsui water reservoir.top
V. Community structure changes in response to disturbance
I am interested in understanding how and why community structure changes along a gradient of disturbance (e.g. pollution). This project has being carrying out together with Norio Yamamura (Research Institute for Humanity and Nature, Japan) and Takeshi Miki (Kyoto Univ., Japan), Michio Kondoh (Ryukoku Univ., Japan), and Kei Tokita (Osaka Univ., Japan). We are compiling field data and investigating patterns of community structure in response to disturbance. We aim to develop theory to explain the observed patterns. The theory and approaches can be applicable to examine environmental quality and ecosystem conservation.top
VI. Zooplankton ecology
I have been learning marine copepod taxonomy and ecology from Prof. Chang-tai Shih since my undergraduate research. I studied copepod community in relation to circulation in the Taiwan Strait as my master thesis. Advised by Prof. Tai-Sheng Chiu, I also investigated trophic relationship between fish and copepods in the Taiwan Strait. I am always amazed by the morphology and behavior of copepods. I continue to study copepod ecology in the oceans around Taiwan. In addition, together with my Ph.D. advisor, Mark Ohman (Scripps Institution of Oceanography, USA), we estimate mortality of Calanus pacificus in the southern California area and study the causes of the mortality. This is part of the Long-Term Ecological Research (LTER): California Current Ecosystem.
Recently, I am planning to develop an automatic system to obtain zooplankton community data using ZooScan and FlowCam. These are newly developed tools with great potential in aquatic research. I am also interested in size-base theory and its application in investigating ecosystem states.top
VII. Scale dependency of ecosystem behavior
Ecosystem and population behavior are both spatially and temporally scale-dependent. Identifying the correct scale of ecological problems is essential for developing conservation strategies; however, this exercise has been overlooked. Importantly, scale-dependency comes from both extrinsic (e.g. seasonal or diel variability of the environment) and intrinsic (e.g. generation or trophic level of organisms) processes. Understanding the interrelationship between these two processes is essential for identifying the correct scale. One can consider an oversimplified example: global warming. When temperature increases, quick responsive organisms (say, prey species) will shift their distribution in response to warming faster than slow responsive organisms (say, predator species). This will potentially cause trophic mismatch and disrupt ecosystem function. I am compiling both biological and environmental time series to investigate the scale-dependent phenomena of biological populations responding to environmental forcing. Three aspects will be examined: scale-dependent variability, nonlinearity, and responsiveness.top