Calcium carbonate and phosphorus interactions in inland waters

Phosphorus, an element essential to all life, is impacted by calcium carbonate (CaCO₃) co-precipitation and dissolution dynamics across aquatic ecosystems. Changes to climate, hydrology, and eutrophication, coupled with differences in terminology related to naming CaCO₃-producing ecosystems (i.e., chalk, carbonate, karst, travertine), point to the urgency and challenges in understanding this portion of the phosphorus cycle. Forms of CaCO₃ vary across inland aquatic ecosystems, from “whiting events” in open waters to massive travertine or tufa formations to cemented layers on basal resources. And, across lakes, streams, and wetlands, periphyton mats and microbialites may form in photic regions. These biogenic carbonate structures beg the question: if aerobic photosynthesis promotes CaCO₃ precipitation, but CaCO₃ precipitation sequesters P, is this a challenge or opportunity for organisms? This review considers that question and others to better characterize this unexpectedly dynamic and influential portion of a major biogeochemical cycle.