picture_planetary_boundary_2_Credit-Tom-Archer-Lake-Erie-algal-bloom-P1010679-500×375 October 27, 2017 500 × 375 Planetary Boundary 2 – Eutrophication – Nitrates and Phosphates Algae bloom in Lake Eire, the first step in creating a fully dead zone. (http://www.miseagrant.umich.edu/lessons/lessons/by-broad-concept/physical-science/dead-zones/)