Can both, the MODIS Terra and Aqua be used for ocean color (Chlorophyll-a) studies, or only MODIS-Aqua should be used due to the serious issues in the blue bands of MODIS-Terra?
If you are interesting in remote sensing data for OC retrieved after January 2004 (and especially after January 2005), better do not use Terra's datasets for quantitative applications, especially for mesotrophic and eutrophic waters. However, for qualitative works it is possible to use the Terra's retrievals (for instance, comparison of chlorophyll distribution patterns at two areas during same period, or for similar works).
You can see also this comparison (especially right row of plots): http://oceancolor.gsfc.nasa.gov/ANALYSIS/PROCTEST/tt02_at10/comp_global_chl_mission.html
Yo use clorofila-a del Modis Aqua resolución 1 km para asociar numero de casos diarios de personas que enferman por una bacteria marina y la concentración de clorofila a de mi área de estudio a los cuales pertenecen esos datos de salud.