Widespread human waste pollution in surface waters observed throughout the urbanized, coastal communities of Lee County, Florida, USA.

The coastal communities of Lee County, Florida, USA have grown rapidly since the 1970s. In this county, drainage ditches, canals, creeks, and the Caloosahatchee River Estuary often have high concentrations of nutrients and bacteria limiting their designated uses. Septic systems have previously been identified as a major pollution source in some areas of Lee County; therefore, this study sought to identify the extent of this issue throughout the county. To accomplish this, surface water samples were collected at 25 ditch, creek, or canal sites suspected of human waste contamination from septic systems in various drainage basins throughout Lee County during January 2020-January 2021. Water samples were analyzed for nutrients, dual stable nitrate isotopes (δ15N-NO3-, δ18O-NO3-), fecal indicator bacteria (enterococci, Escherichia coli), a molecular tracer of human waste (HF183), and chemical tracers of human waste (the artificial sweetener sucralose, pharmaceuticals). Particulate organic matter (POM) and macrophytes were also collected and analyzed for stable carbon (δ13C) and nitrogen (δ15N) isotopes, as well as elemental composition (C:N:P). To broaden the assessment of stable isotope values and C:N:P, archived macrophyte samples from 2019 were also included in analyses. Ammonium concentrations were high (> 4.3 µM) in 55 % of samples. Fecal bacteria were high in 66 % of samples. HF183 was detected in 50 % of samples and positively correlated with enterococci (r = 0.32). Sucralose concentrations were high (> 380 ng/L) in 54 % of samples, while carbamazepine was detected in 40 % of samples. Human waste N sources were indicated by δ15N > 3.00 ‰ at 44 % of sites by δ15N-NO3-, 68 % of sites by POM, and at 100 % of sites where macrophyte samples were collected. This large-scale study provides evidence of widespread human waste pollution throughout Lee County and can help guide infrastructure improvements to promote sustainable development. These findings should be applicable to urbanized regions globally that are experiencing declines in water quality and harmful algal blooms due to development with inadequate infrastructure.

Septic system-groundwater-surface water couplings in waterfront communities contribute to harmful algal blooms in Southwest Florida.

As human population growth has expanded in Southwest Florida, water quality has become degraded with an increased occurrence of harmful algal blooms (HABs). Red tide (Karenia brevis) originating offshore, intensifies in nearshore waters along Florida's Gulf Coast, and blue-green algae (Microcystis spp.) originating in Lake Okeechobee is discharged into the Caloosahatchee River. These HABs could be enhanced by anthropogenic nitrogen (N) and phosphorus (P) from adjacent watersheds. North Fort Myers is a heavily developed, low-lying city on the Caloosahatchee River Estuary serviced by septic systems with documented nutrient and bacterial pollution. To identify sources of pollution within North Fort Myers and determine connections with downstream HABs, this multiyear (2017-2020) study examined septic system- groundwater- surface water couplings through the analysis of water table depth, nutrients (N, P), fecal indicator bacteria (FIB), molecular markers (HF183, GFD, Gull2), chemical tracers (sucralose, pharmaceuticals, herbicides, pesticides), stable isotopes of groundwater (δ15N-NH4, δ15N-NO3) and particulate organic matter (POM; δ15N, δ13C), and POM elemental composition (C:N:P). POM samples were also collected during K. brevis and Microcystis spp. HAB events. Most (>80%) water table depth measurements were too shallow to support septic system functioning (<1.07 m). High concentrations of NH4+ and NOx, up to 1094 µM and 482 µM respectively, were found in groundwater and surface water. δ15N values of groundwater (+4.7‰) were similar to septic effluent (+4.9‰), POM (+4.7‰), and downstream HABs (+4.8 to 6.9‰), indicating a human waste N source. In surface water, FIB were elevated and HF183 was detected, while in groundwater and surface water sucralose, carbamazepine, primidone, and acetaminophen were detected. These data suggest that groundwater and surface water in North Fort Myers are coupled and contaminated by septic system effluent, which is negatively affecting water quality and contributing to the maintenance and intensification of downstream HABs.

Competitive Growth Assay of Mutagenized Chlamydomonas reinhardtii Compatible With the International Space Station Veggie Plant Growth Chamber.

A biological life support system for spaceflight would capture carbon dioxide waste produced by living and working in space to generate useful organic compounds. Photosynthesis is the primary mechanism to fix carbon into organic molecules. Microalgae are highly efficient at converting light, water, and carbon dioxide into biomass, particularly under limiting, artificial light conditions that are a necessity in space photosynthetic production. Although there is great promise in developing algae for chemical or food production in space, most spaceflight algae growth studies have been conducted on solid agar-media to avoid handling liquids in microgravity. Here we report that breathable plastic tissue culture bags can support robust growth of Chlamydomonas reinhardtii in the Veggie plant growth chamber, which is used on the International Space Station (ISS) to grow terrestrial plants. Live cultures can be stored for at least 1 month in the bags at room temperature. The gene set required for growth in these photobioreactors was tested using a competitive growth assay with mutations induced by short-wave ultraviolet light (UVC) mutagenesis in either wild-type (CC-5082) or cw15 mutant (CC-1883) strains at the start of the assay. Genome sequencing identified UVC-induced mutations, which were enriched for transversions and non-synonymous mutations relative to natural variants among laboratory strains. Genes with mutations indicating positive selection were enriched for information processing genes related to DNA repair, RNA processing, translation, cytoskeletal motors, kinases, and ABC transporters. These data suggest that modification of DNA repair, signal transduction, and metabolite transport may be needed to improve growth rates in this spaceflight production system.