Synergistic effects of nitrogen and phosphorous on the growth of algal cells reveled by a microfluidic platform*

A sudden growth of photosynthetic algal cells causes Harmful Algal Bloom (HAB), depleting water resources and disrupting the balance of aqua ecosystems. HAB is an emerging environmental problem acerbated by climate change and population growth. Despite the urgency of the problem, there still lacks a systematic understanding of the environmental conditions (physical, chemical, and biological) under which HABs occur. In this presentation, we studied the growth of a model algal strain, Chlamydomonas reinhardtii, under a dual concentration gradient of nitrogen (N) and phosphorous (P) and found that N and P synergistically promoted algal cell growth. Interestingly, no discernible response was observed under single nutrient gradient. We also demonstrated the potential application of the newly developed microfluidic platform that integrated the array microhabitat format with dual gradient generation, enabling fast screening of environmental factors for algal growth studies. Future investigations will include the dynamics of bacterial community under controlled environmental condition.