Coastal eutrophication, the process by which excessive nutrients accumulate in waters resulting in large algal blooms, is becoming a problem of global concern and has serious socioeconomic and socio-ecological impacts.  This is of concern because eutrophication is directly linked to the frequency and severity of harmful algal blooms (HABs) and development of hypoxia (i.e., water with little to no oxygen).  The nutrients that drive eutrophication are commonly derived from the land (e.g., agricultural runoff, sewage discharge, industrial pollution) and carried to the coast ocean by rivers, runoff, submarine groundwater discharge, and direct sewage discharge etc.  Anthropogenic changes (i.e., climate change and changes in land use), which impact nutrient transfer to the coastal ocean, also influence the occurrence and severity of HABs.  Now, eutrophication is not a new problem and its link to the influx of terrestrially derived nutrients is well known.  Despite this, the problem is growing and mitigation techniques such as reducing fertilizer use so that rivers transport fewer nutrients to the coastal ocean do not always help.  Clearly, some parts of the puzzle are missing.  Addressing this knowledge gap is crucial for managing eutrophication and, consequently, mitigating impacts related to HABs.