Hurricane Disturbance Stimulated Nitrification and Altered Ammonia Oxidizer Community Structure in Lake Okeechobee and St. Lucie Estuary (Florida)

Abstract

Nitrification is an important biological link between oxidized and reduced forms of nitrogen (N). The efficiency of nitrification plays a key role in mitigating excess N in eutrophic systems, including those with cyanobacterial harmful algal blooms (cyanoHABs), since it can be closely coupled with denitrification and removal of excess N. Recent work suggests that competition for ammonium (NH 4 +) between ammonia oxidizers and cyanoHABs can help determine microbial community structure. Nitrification rates and ammonia-oxidizing archaeal (AOA) and bacterial (AOB) community composition and gene abundances were quantified in Lake Okeechobee and St. Lucie Estuary in southern Florida (United States). We sampled during cyanobacterial (Microcystis) blooms in July 2016 and August 2017 (2 weeks before Hurricane Irma) and 10 days after Hurricane Irma made landfall. Nitrification rates were low during cyanobacterial blooms in Lake Okeechobee and St. Lucie Estuary, while low bloom conditions in St. Lucie Estuary coincided with greater nitrification rates. Nitrification rates in the lake were correlated (R 2 = 0.94; p = 0.006) with AOA amoA abundance. Following the hurricane, nitrification rates increased by an order of magnitude, suggesting that nitrifiers outcompeted cyanobacteria for NH 4 + under turbid, poor light conditions. After Irma, AOA and AOB abundances increased in St. Lucie Estuary, while only AOB increased in Lake Okeechobee. AOA sequences clustered into three major lineages: Nitrosopumilales (NP), Nitrososphaerales (NS), and Nitrosotaleales (NT). Many of the lake OTUs placed within the uncultured and uncharacterized NS δ and NT β clades, suggesting that these taxa are ecologically important along this eutrophic, lacustrine to estuarine continuum. After the hurricane, the AOA community shifted toward dominance by freshwater clades in St. Lucie Estuary and terrestrial genera in Lake Okeechobee, likely due to high rainfall and subsequent increased turbidity and freshwater loading from the lake into the estuary. AOB community structure was not affected by the disturbance. AOA communities were consistently more diverse than AOB, despite fewer

Properties of ammonia‐oxidising bacteria and archaea in a hypereutrophic urban river network

“…Additionally, seasonal algal blooms may be an important factor that could affect the temporal patterns of ammonia‐oxidising microbial communities. Some researchers suggested that ammonia‐oxidising microorganisms compete with algae and other primary producers for NH 4 + (Glibert et al., 2016; Hampel et al., 2018, 2020). In the present study, the results of water quality analysis showed that the increases in the concentrations of Chl a in the April–August months were related to the decreases in the concentrations of DIN, NH 4 + , , and in the relevant months, suggesting that summer algal blooms were possibly responsible for contributing to the decrease of ambient nutrient concentrations.…”

Dissolved organic nutrients at the interface of fresh and marine waters: flow regime changes, biogeochemical cascades and picocyanobacterial blooms—the example of Florida Bay, USA

“…As pH declined, higher concentrations of NO 3 were observed (up to 2 lM) during the drought and in the years following the storm events, in all cases being highest at the end of the dry season or early wet season. Similarly, Hampel et al (2020) observed increases in nitrification in Lake Okeechobee and St Lucie Estuary, Florida, following Hurricane Irma. Thus, if nitrification is inhibited by temperature of pH, any available NH 4…”

Long-Term Assessment of Surface Water Quality in a Highly Managed Estuary Basin

“…Levels of TN, microcystin, and toxic Microcystis strains are highly and significantly correlated across the lake and estuary gradient. In addition, the competition between cyanobacteria and nitrifiers for ammonium impacts the capacity for denitrification in the system [32,33].…”

“…Qian et al (2007) [30] assessed long-term data (1979 to 2004) of water quality constituents in major canals and found that almost all nutrient species had significantly higher concentrations in the wet than in the dry season. Studies by Hampel et al (2020) [32], Kramer et al (2018) [33], and Oehrle et al (2017) [35] demonstrated the key role of nitrogen species and salinity in toxic Microcystis blooms in the lake-estuary continuum. The South Florida Water Management District (SFWMD) and the Florida Department of Environmental Protection (FDEP) continuously assess the water quality of the estuary and the lake.…”

“…Ecological, biochemical, and flow regime studies of the St. Lucie Estuary Basin have improved the knowledge base of best management practices [25, [29][30][31] and eutrophication science [32][33][34][35]. Studies by Doering (1996) [29] and Chamberlain and Hayward (1996) [26] recommended a more stable, lower flow from canals to improve water quality and attain resource management goals.…”