A Historical Perspective on Eutrophication in the Pensacola Bay Estuary, FL, USA

Abstract

In this chapter, we provide a brief description of the Pensacola Bay estuary, examining the available historical data for evidence of trends in eutrophication within the estuary. Common to many industrialized estuaries, Pensacola Bay has been subjected to unregulated point sources of nutrients and other contaminants, peaking during the 1950s and 1960s. Also, over the past 60 years, the region has experienced a fivefold increase in population in the watershed and a doubling of river nitrate concentrations. Today, the estuary exhibits classical symptoms of eutrophication, including extensive summer hypoxia, significant loss of sea grass habitat, and phytoplankton dynamics that respond strongly to seasonal and interannual variation in freshwater flow. Surprisingly, Pensacola Bay appears to have low nutrient concentrations, moderate productivity, and high water transparency, characteristics that appear to have persisted during a period of rapid human population growth. We find the lack of demonstrable changes in the distribution of phytoplankton biomass or distribution and severity of hypoxia during a period of increasing human population pressures enigmatic.

“… about 11 o’clock I saw a bay, the best I have ever seen in my life” from the diary of Juan Jordan de Reina on entering Pensacola Bay on February 6, 1686 (Dunn 1916)

Jane M. Caffrey and Michael C. Murrell

Jane and Mike met at the University of Maryland’s Horn Point Laboratory in 1989, when Mike moved from LUMCON to work as a technician. At the time, Jane was nearing completion of her Ph.D. under Michael Kemp (his first Ph.D. student!). It’s hard to say exactly what brought them together, although Mike’s chicken and sausage gumbo probably played a more important role than Jane’s pesto spaghetti. They stayed together through a whirlwind of location changes: Mike moved to the University of Washington to continue working as an Oceanographer for Evelyn Lessard and Jane took a Fulbright postdoc at the University of Aarhus under Henry Blackburn. After her exhilarating experience in Denmark, Jane moved to a postdoctoral position at the USGS in Menlo Park. So, while still separated by ~800 miles, at least they were the same time zone. Then, on Valentine’s Day 1992, Mike moved to the San Francisco Bay area in preparation for starting his Ph.D. at the University of California Santa Cruz with Mary Silver as his academic advisor and Tim Hollibaugh (SFSU) as his research advisor. Jane and Mike worked side by side on the USGS vessel, the R/V Polaris (recently retired), as Mike examined bacterioplankton and microzooplankton dynamics in North San Francisco Bay and Jane studied patterns in benthic nutrient cycling as modulated by the spring phytoplankton bloom. After her postdoc ended, Jane became a Research Oceanographer at UCSC and also Research Coordinator at the Elkhorn Slough National Estuarine Research Reserve. Following Mike’s graduation, they all (baby Amelie makes 3) moved back East where Mike took a postdoc with the EPA at the Gulf Ecology Division in Gulf Breeze, FL, which evolved into a career position. Jane began collaborations with the University of West Florida, which also evolved into an academic faculty position. Over the years, Mike has helped to develop Jane’s appreciation of microbes and plankton as discrete organisms, while Jane has helped to develop Mike’s appreciation of biogeochemical cycling and playing in the mud.