Interannual and Seasonal Patterns of Estuarine Phytoplankton Diversity in Galveston Bay, Texas, USA

Few studies have undertaken multi-year measures of diversity changes in estuarine phytoplankton communities. In this communication, we show the utility of photopigment-based diversity measures to quantify changes in community composition over 10 years (1999-2009) in Galveston Bay, Texas. Over a 10-year period, there were no discernable long term trends in diversity. However, annual and seasonal diversity showed significant differences between years and higher diversity during summer and fall months. The processes driving these changes could not be determined using simple linear correlations with a variety of physical and chemical parameters. This result suggests that the regulation of phytoplankton community structure over broad spatiotemporal scales in Galveston Bay is likely due to the complex interaction of multiple (non-linear) factors at scales smaller than the ecosystem level. Understanding these complex interactions is a key to developing realistic estuarine health bioindicators and mechanistic ecosystem-level models for estuarine phytoplankton community-composition dynamics. The photopigment diversity index provides one useful approach for quantifying phytoplankton community composition over broad spatiotemporal scales and assessing the stability of estuarine ecosystems.