Cyclical Patterns and a Regime Shift in the Character of Phytoplankton Blooms in a Restricted Sub-Tropical Lagoon, Indian River Lagoon, Florida, United States

Abstract

This paper examines the character of phytoplankton blooms in a restricted sub-tropical lagoon along the Atlantic coast of central Florida. The results of the 23-year study (1997–2020) provide evidence for multiple types of variability in bloom activity, including cyclical patterns, stochastic events, and most prominently a regime shift in composition and intensity. Cyclical patterns (e.g., El Niño/La Niña periods) and stochastic events (e.g., tropical storms) influenced rainfall levels, which in turn impacted nutrient concentrations in the water column and the timing and intensity of blooms. In 2011, a major change occurred in the character of blooms, with a dramatic increase in peak biomass levels of blooms and the appearance of new dominant taxa, including the brown tide species Aureoumbra lagunensis and other nanoplanktonic species. Results of quantitative analyses reveal system behavior indicative of a regime shift. The shift coincided with widespread losses of seagrass community and reduced drift algae biomass. A combination of exceptionally low water temperatures in the winters of 2009/2010 and 2010/2011, hypersaline conditions associated with drought conditions, and high light attenuation caused by blooms appear to have contributed to the widespread and protracted decline in seagrass and drift macroalgal communities in the lagoon, leading to shifts in distribution of internal and external nutrient sources toward phytoplankton.

Spatiotemporal Patterns in the Biomass of Drift Macroalgae in the Indian River Lagoon, Florida, United States

“…28 months from July 2010 to October 2012 and 6-12 months in reaches 1, 2, and 3 during the 18 months from July 2015 to December 2016 (Phlips et al, 2021;Lasi et al, this volume). A similar response to reductions in light availability caused by phytoplankton was noted in the coastal waters off Denmark (Nielsen et al, 2002).…”

High-Resolution Spatiotemporal Dynamics of Harmful Algae in the Indian River Lagoon (Florida)—A Case Study of Aureoumbra lagunensis, Pyrodinium bahamense, and Pseudo-nitzschia

“…The appearance of a novel high biomass bloom of an unidentified nano-sized cyanobacterium in 2020 provides further evidence of the shift to more frequent high biomass blooms of smaller-celled taxa in the IRL since the 2011 "superbloom" (Phlips et al, 2015(Phlips et al, , 2020(Phlips et al, , 2021. It is important to point out that the phytoplankton assemblage is rarely monospecific during blooms of these nanoplankton taxa, often including cells with morphological characters that are not readily distinguished by transmitted light microscopy used in routine analysis.…”

“…Effects resulting from IRL HABs include low dissolved oxygen (Diaz and Rosenberg, 2008), decreases in light availability, losses of seagrass (Morris et al, 2018;Lapointe et al, 2020), fisheries closures related to toxins (Landsberg et al, 2006), and negative health effects on wildlife and shellfish resources (Gobler et al, 2013;Fire et al, 2015;Adams et al, 2019). Although blooms of harmful algae are not a recent development in the IRL, the past 10 years have exhibited a measurable shift to more frequent and higher biomass bloom events dominated by nanoand picoplankton (Phlips et al, 2021).…”

Mesozooplankton Community Dynamics and Grazing Potential Across Algal Bloom Cycles in a Subtropical Estuary

“…The estuary system consists of three connected regions: the Mosquito Lagoon, the Indian River Lagoon and the Banana River Lagoon. Phytoplankton blooms have long been observed in the IRL, but they experienced a dramatic increase in intensity and change in composition in 2011 (Phlips et al, 2021). Prior to 2011, relatively large dinoflagellates and diatoms were the dominant bloom species (Phlips et al, 2015).…”

“…However, widespread seagrass losses in 2009-2010, and extraordinarily cold winter water temperatures in 2010, were followed by blooms of small-celled species (<5 µm in diameter). In 2011, picocyanobacteria and Pedinophyceae species bloomed throughout the northern IRL, followed by repeated intense blooms of the brown tide pelagophyte Aureoumbra lagunensis, and other small-celled taxa (Phlips et al, 2021). None of these taxa were documented at such levels in the estuary prior to 2011 but have occurred repeatedly in the years since (Phlips et al, 2015(Phlips et al, , 2020Schaefer et al, 2019).…”