Year-around survey and manipulation experiments reveal differential sensitivities of soil prokaryotic and fungal communities to saltwater intrusion in Florida Everglades wetlands.

Global sea-level rise is transforming coastal ecosystems, especially freshwater wetlands, in part due to increased episodic or chronic saltwater exposure, leading to shifts in biogeochemistry, plant- and microbial communities, as well as ecological services. Yet, it is still difficult to predict how soil microbial communities respond to the saltwater exposure because of poorly understood microbial sensitivity within complex wetland soil microbial communities, as well as the high spatial and temporal heterogeneity of wetland soils and saltwater exposure. To address this, we first conducted a two-year survey of microbial community structure and bottom water chemistry in submerged surface soils from 14 wetland sites across the Florida Everglades. We identified ecosystem-specific microbial biomarker taxa primarily associated with variation in salinity. Bacterial, archaeal and fungal community composition differed between freshwater, mangrove, and marine seagrass meadow sites, irrespective of soil type or season. Especially, methanogens, putative denitrifying methanotrophs and sulfate reducers shifted in relative abundance and/or composition between wetland types. Methanogens and putative denitrifying methanotrophs declined in relative abundance from freshwater to marine wetlands, whereas sulfate reducers showed the opposite trend. A four-year experimental simulation of saltwater intrusion in a pristine freshwater site and a previously saltwater-impacted site corroborated the highest sensitivity and relative increase of sulfate reducers, as well as taxon-specific sensitivity of methanogens, in response to continuously pulsing of saltwater treatment. Collectively, these results suggest that besides increased salinity, saltwater-mediated increased sulfate availability leads to displacement of methanogens by sulfate reducers even at low or temporal salt exposure. These changes of microbial composition could affect organic matter degradation pathways in coastal freshwater wetlands exposed to sea-level rise, with potential consequences, such as loss of stored soil organic carbon.

Tropical cyclones cumulatively control regional carbon fluxes in Everglades mangrove wetlands (Florida, USA).

Mangroves are the most blue-carbon rich coastal wetlands contributing to the reduction of atmospheric CO2 through photosynthesis (sequestration) and high soil organic carbon (C) storage. Globally, mangroves are increasingly impacted by human and natural disturbances under climate warming, including pervasive pulsing tropical cyclones. However, there is limited information assessing cyclone's functional role in regulating wetlands carbon cycling from annual to decadal scales. Here we show how cyclones with a wide range of integrated kinetic energy (IKE) impact C fluxes in the Everglades, a neotropical region with high cyclone landing frequency. Using long-term mangrove Net Primary Productivity (Litterfall, NPPL) data (2001-2018), we estimated cyclone-induced litterfall particulate organic C (litter-POC) export from mangroves to estuarine waters. Our analysis revealed that this lateral litter-POC flux (71-205 g C m-2 year-1)-currently unaccounted in global C budgets-is similar to C burial rates (69-157 g C m-2 year-1) and dissolved inorganic carbon (DIC, 61-229 g C m-2 year-1) export. We proposed a statistical model (PULITER) between IKE-based pulse index and NPPL to determine cyclone's impact on mangrove role as C sink or source. Including the cyclone's functional role in regulating mangrove C fluxes is critical to developing local and regional climate change mitigation plans.

Composition of Prokaryotic and Eukaryotic Microbial Communities in Waters around the Florida Reef Tract.

The Florida Keys, a delicate archipelago of sub-tropical islands extending from the south-eastern tip of Florida, host the vast majority of the only coral barrier reef in the continental United States. Abiotic as well as microbial components of the surrounding waters are pivotal for the health of reef habitats, and thus could play an important role in understanding the development and transmission of coral diseases in Florida. In this study, we analyzed microbial community structure and abiotic factors in waters around the Florida Reef Tract. Both bacterial and eukaryotic community structure were significantly linked with variations in temperature, dissolved oxygen, and total organic carbon values. High abundances of copiotrophic bacteria as well as several potentially harmful microbes, including coral pathogens, fish parasites and taxa that have been previously associated with Red Tide and shellfish poisoning were present in our datasets and may have a pivotal impact on reef health in this ecosystem.

Understanding the occurrence and distribution of emerging pollutants and endocrine disruptors in sensitive coastal South Florida Ecosystems.

Environmental exposure risk to different xenobiotics, which can potentially alter the function of the endocrine system, remains a great health and safety concern for aquatic species and humans. Steroid hormones, pharmaceuticals and personal care products (PPCPs) have been identified as important aquatic contaminants due to their widespread occurrence in surface waters and their endocrine disrupting properties. Heavily populated areas in South Florida not served by municipal wastewater collection present an unexpected high risk of anthropogenic contaminants to nearby coastal systems through surface runoff and groundwater flow. Previous studies in South Florida have been largely concentrated on assessing the relevance of the fate and transport of inorganic nutrients, heavy metals and pesticides with regulatory criteria. Therefore, a significant gap exists in assessing occurrence, distribution and biological significance of the presence of human related organic contaminants in natural surface waters. In this study, we have developed a fast and sensitive online solid-phase extraction followed by liquid chromatography-high resolution mass spectrometry (SPE-LC-HRMS) method using a Q-Exactive system for the determination of the occurrence and distribution of selected wastewater tracers/indicators, recalcitrant PPCPs and steroid hormones in South Florida surface waters. Seasonal and spatial variations of these contaminants were monitored from 2017 to 2019. The presence of total coliforms and E. coli were also evaluated in order to further assess water quality. Correlations between hormones and anthropogenic tracers were explored to better elucidate the sources, pathways and exposure risks to these contaminants. Caffeine, sucralose, Diethyl-m-toluamide (DEET) and carbamazepine were frequently detected in the water samples, which is indicative of extensive wastewater intrusion impacting the surface water. Estrone (E1), 17-ß-estradiol (E2), and 17-α-ethynylestradiol (EE2) levels found in surface water raises concern of potential endocrine disruption effects in the aquatic ecosystem. Hazard quotient has been calculated to identify areas with high ecological risks to aquatic organisms.

Analyzing and comparing complex environmental time series using a cumulative sums approach.

Cumulative sums (Cusums) are a simple, efficient statistical method developed for process control and increasingly used to determine underlying features of time series. Here, two useful applications of Cusums to environmental time series are presented: Cusums in the time domain and plotting Cusum-transformed variables against non-transformed variables to extract meaning in the context of driver-response relationships. These statistical analyses are simple to conduct and provide valuable information about trends, patterns and thresholds of time-series over time and in relation to potential driver variables. In addition, this work investigates the robustness of the Cusum transform to various characteristics of environmental time series that challenge conventional statistical methods. In summary, this work presents: •Cusum methods to derive meaning from complex environmental time series.•Effects of common time series issues on the Cusums method.•Application to real-world datasets.

Biogeochemical classification of South Florida's estuarine and coastal waters.

South Florida's watersheds have endured a century of urban and agricultural development and disruption of their hydrology. Spatial characterization of South Florida's estuarine and coastal waters is important to Everglades' restoration programs. We applied Factor Analysis and Hierarchical Clustering of water quality data in tandem to characterize and spatially subdivide South Florida's coastal and estuarine waters. Segmentation rendered forty-four biogeochemically distinct water bodies whose spatial distribution is closely linked to geomorphology, circulation, benthic community pattern, and to water management. This segmentation has been adopted with minor changes by federal and state environmental agencies to derive numeric nutrient criteria.