Conceptual diagram of human and climate interactions on nutrient-enhanced productivity, harmful and noxious algal blooms, and formation of hypoxia. Positive (+) interactions designate a worsening of conditions related to algal blooms and hypoxia, and negative (−) interactions designate fewer algal blooms and lessening of hypoxia symptoms. Dashed lines indicate negative feedback processes to nutrient-enhanced production and subsequent hypoxia. Dotted line between anthropogenic activities and climate variability/climate change indicates that current climate change is driven largely by humans, but that climate change can certainly affect human activities. Modified from Rabalais et al. (2010).