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Wastewater management is a critical issue globally. In Florida, the importance of this issue is heightened by the proximity to sensitive ecosystems. Distributed wastewater treatment units (DWTU) are a recent, state-approved alternative to septic system conversions to centralized sewer infrastructure. In this study, the performance of a DWTU was tested at a new residence in Lake Hamilton, FL. A monitoring well was installed downgradient of the DWTU absorption field to establish baseline groundwater conditions prior to occupation of the residence. The residence was occupied, after which groundwater, DWTU influent, and effluent samples were collected. Many effluent parameters significantly decreased compared to influent, including ammonia (NH3; 97%), total Kjeldahl nitrogen (TKN; 95%), total nitrogen (TN; 88%), the TN:TP ratio (84%), fecal coliforms (92%), carbonaceous biochemical oxygen demand (CBOD; 96%), and total suspended solids (TSS; 96%). In the groundwater, nutrient concentrations initially increased compared to the baseline data, but eventually decreased, demonstrating that the DWTU was effective at improving quality of wastewater effluent. These systems could be especially effective in sensitive areas where advanced wastewater treatment has been mandated or is needed.

Long-term monitoring data show that hard coral cover on the Great Barrier Reef (GBR) has reduced by >70 % over the past century. Although authorities and many marine scientists were in denial for many years, it is now widely accepted that this reduction is largely attributable to the chronic state of eutrophication that exists throughout most of the GBR. Some reefs in the far northern GBR where the annual mean chlorophyll a (Chl a) is in the lower range of the proposed Eutrophication Threshold Concentration for Chl a (∼0.2–0.3 mg m–3) show little or no evidence of degradation over the past century. However, the available evidence suggests that coral diseases and the crown-of-thorns starfish will proliferate in such waters and hence the mandated eutrophication Trigger values for Chl a (∼0.4–0.45 mg m–3) will need to be decreased to ∼0.2 mg m–3 for sustaining coral reef communities.

Background Symbioses between primary producers and bacteria are crucial for nutrient exchange that fosters host growth and niche adaptation. Yet, how viruses that infect bacteria (phages) influence these bacteria-eukaryote interactions is still largely unknown. Here, we investigate the role of viruses on the genomic diversity and functional adaptations of bacteria associated with pelagic sargassum. This brown alga has dramatically increased its distribution range in the Atlantic in the past decade and is predicted to continue expanding, imposing severe impacts on coastal ecosystems, economies, and human health. Results We reconstructed 73 bacterial and 3963 viral metagenome-assembled genomes (bMAGs and vMAGs, respectively) from coastal Sargassum natans VIII and surrounding seawater. S . natans VIII bMAGs were enriched in prophages compared to seawater (28% and 0.02%, respectively). Rhodobacterales and Synechococcus bMAGs, abundant members of the S . natans VIII microbiome, were shared between the algae and seawater but were associated with distinct phages in each environment. Genes related to biofilm formation and quorum sensing were enriched in S . natans VIII phages, indicating their potential to influence algal association in their bacterial hosts. In-vitro assays with a bacterial community harvested from sargassum surface biofilms and depleted of free viruses demonstrated that these bacteria are protected from lytic infection by seawater viruses but contain intact and inducible prophages. These bacteria form thicker biofilms when growing on sargassum-supplemented seawater compared to seawater controls, and phage induction using mitomycin C was associated with a significant decrease in biofilm formation. The induced metagenomes were enriched in genomic sequences classified as temperate viruses compared to uninduced controls. Conclusions Our data shows that prophages contribute to the flexible genomes of S . natans VIII-associated bacteria. These prophages encode genes with symbiotic functions, and their induction decreases biofilm formation, an essential capacity for flexible symbioses between bacteria and the alga. These results indicate that prophage acquisition and induction contribute to genomic and functional diversification during sargassum - bacteria symbioses, with potential implications for algae growth. 1vVC6YGWLCm_DZc419o4RC Video Abstract

During the past two decades coral reefs in the greater Caribbean area have been altered by phase shifts away from corals and toward macroalgae or algal turfs. This study tested the hypothesis that because the phase shift on reefs in Jamaica and southeast Florida involved frondose macroalgae, bottom-up control via nutrient enrichment must be a causal factor. The approach was multifaceted and included measurement of near-bottom nutrient concentrations, salinity, nutrient enrichment bioassays, alkaline phosphatase assays, tissue C:N:P ratios, and tissue15N:14N(δ15N) ratios. In both locations, concentrations of dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (SRP) exceeded nutrient thresholds$(\\sim1.0 \\mu M DIN, 0.1 \\mu M SRP)$noted to sustain macroalgal blooms on Caribbean coral reefs. High seawater DIN:SRP ratios, alkaline phosphatase activity, and tissue C:P and N:P ratios of macroalgae on the carbonate-rich Jamaican reef suggested SRP limitation of productivity compared to lower values of these variables on siliciclastic reefs in Florida that suggested DIN limitation. This pattern was coroborated experimentally when SRP enrichment increased Pmax(photosynthetic capacity at light saturation) of the chlorophyte Chaetomorpha linum in Jamaica compared to DIN enrichment that increased α (the photosynthetic efficiency under low irradiance) of the deeper growing chlorophyte Codium isthmocladum in southeast Florida. Increased DIN concentrations were associated with reduced salinity on both reefs indicating submarine groundwater discharge was a significant source of DIN. Elevated δ15Nvalues of C. isthmocladum tissue further pointed to wastewater DIN as a source of nitrogen contributing to the blooms in southeast Florida.

Increased loadings of nitrogen (N) from fertilizers, top soil, sewage, and atmospheric deposition are important drivers of eutrophication in coastal waters globally. Monitoring seawater and macroalgae can reveal long-term changes in N and phosphorus (P) availability and N:P stoichiometry that are critical to understanding the global crisis of coral reef decline. Analysis of a unique 3-decade data set for Looe Key reef, located offshore the lower Florida Keys, showed increased dissolved inorganic nitrogen (DIN), chlorophyll a, DIN:soluble reactive phosphorus (SRP) ratios, as well as higher tissue C:P and N:P ratios in macroalgae during the early 1990s. These data, combined with remote sensing and nutrient monitoring between the Everglades and Looe Key, indicated that the significant DIN enrichment between 1991 and 1995 at Looe Key coincided with increased Everglades runoff, which drains agricultural and urban areas extending north to Orlando, Florida. This resulted in increased P limitation of reef primary producers that can cause metabolic stress in stony corals. Outbreaks of stony coral disease, bleaching, and mortality between 1995 and 2000 followed DIN enrichment, algal blooms, and increased DIN:SRP ratios, suggesting that eutrophication interacted with other factors causing coral reef decline at Looe Key. Although water temperatures at Looe Key exceeded the 30.5 °C bleaching threshold repeatedly over the 3-decade study, the three mass bleaching events occurred only when DIN:SRP ratios increased following heavy rainfall and increased Everglades runoff. These results suggest that Everglades discharges, in conjunction with local nutrient sources, contributed to DIN enrichment, eutrophication, and increased N:P ratios at Looe Key, exacerbating P limitation, coral stress and decline. Improved management of water quality at the local and regional levels could moderate N inputs and maintain more balanced N:P stoichiometry, thereby reducing the risk of coral bleaching, disease, and mortality under the current level of temperature stress.

Coral reefs are facing a constant barrage of human impacts, including eutrophication, overharvesting and climate change. While the local effects of overharvesting have been well-studied, regional nutrient loading from anthropogenic activities on land and global climate change-induced disturbances are increasing in magnitude and necessitating cross-scale multi-stressor approaches for coral reef ecology. Here, we expand on longstanding theory to develop an integrated multi-stressor framework for coral reefs. We show that: (i) The geometry of a simple, empirically motivated model suggests nutrients and harvesting can operate similarly, and synergistically, in driving shifts from coral- to algae-dominated reefs, resulting in clear context-dependent management implications; and (ii) this same geometry suggests climate-driven coral mortality can drive the presence of long transients and climate-driven alternate states, even in moderately impacted ecosystems. Reefs seemingly in a “safe space” based on individual stressors may in fact be much more susceptible to increasingly frequent storms and bleaching events in multi-stressor conditions. By integrating these findings with general ecological and theoretical concepts, we suggest that responses in benthic composition may act as “signatures of change” to multi-stressors, allowing us to develop a predictive and generalizable multi-stressor framework for coral reefs under global change. In line with this theory, we detail empirical evidence from Barbados of historical changes in reef composition and multi-stressor impacts within our framework. By bridging coral reef ecology and general ecological concepts, we can better understand ecosystem functioning and resilience in these important yet highly threatened systems.

The results from the multimillion dollar Enrichment of Nutrients on Coral Reefs Experiment (ENCORE) on One Tree Island Reef (OTIR) suggest that increased nutrient loads to coral reefs will have little or no effect on the algal growth rates and, hence, on the associated effects that increased algal growth might have on the functioning and stability of coral reefs. However, a comparison of the concentrations of nutrients within the OTIR lagoon with the proposed nutrient threshold concentrations (NTC) for coral reefs suggests that all sites, including the control sites, were saturated with nutrients during ENCORE, and, hence, one would not expect to get any differences between treatments in the algal-growth related measurements. Thus, ENCORE results provide strong support for the proposed NTCs and support the ecological principle that algal productivity and, consequently, the functioning of coral reefs are sensitive to small changes in the background concentrations of nutrients. The principal conclusion of ENCORE, namely that the addition of nutrients did not cause the “pristine” OTIR to convert from coral communities to algal dominated reefs, is contrary to the fact that there was prolific macroalgal growth on the walls and crests of the experimental microatolls by the end of ENCORE.

The comment by Julian (2020) criticizes aspects of our paper, “Nitrogen enrichment, altered stoichiometry, and coral reef decline at Looe Key, Florida Keys, USA.” The comment begins by misrepresenting our extensive literature review, while providing no justification for the claim of a “skewed reading.” Julian’s critique focused on methods of data handling, statistics, and spatial awareness, which we demonstrate in every case to be either irrelevant or incorrect. We provide additional supporting data that refute these claims. For example, Julian criticized the removal of data points below the method detection limits (MDLs), but when these points are included, the results do not change. Further, Julian criticized our removal of outliers, but so few points were excluded that it did not change the results of the statistical analyses. Julian also misinterpreted the methods of our correlation and stepwise regression analyses but did not dispute the Kruskal–Wallis tests of our 30-year dataset that revealed significant decadal changes. Julian’s closing paragraph is replete with misinformation and demonstrates a lack of understanding as to how increased freshwater flows associated with Everglades Restoration have led to a worsening of algal blooms and coral decline in the Florida Keys National Marine Sanctuary (FKNMS). This comment represents a smokescreen to confuse the scientific community about the physical connectivity of the Everglades basin and the FKNMS. Past water management policies based on politics, not sound science, have caused irreparable and ongoing environmental damage to sensitive coral reef communities in the FKNMS.

Nutrient enrichment continues to disrupt marine ecosystem function worldwide. Assessing eutrophication in seagrass ecosystems such as the Great White Heron National Wildlife Refuge (GWHNWR), Florida Keys is critical for protecting the diverse community that depends on the intertidal and subtidal seagrass beds. We quantified water column nutrients, chlorophyll a, tissue nutrients in macroalgae and Thalassia testudinum, and epiphyte percent cover on seagrasses on tidal flats seasonally over 1 year at three sites: Howe Key, Water Keys, and Upper Harbor Key. Water column nutrients (total nitrogen, total phosphorus, nitrate-nitrite, ammonium, dissolved inorganic nitrogen, dissolved organic nitrogen, soluble reactive phosphorus, dissolved organic phosphorus) increased from fall to winter at Water Keys. These increased nutrients coincided with a bloom of the epiphyte Spyridia filamentosa on seagrasses that exceeded 40 % cover at Water Keys and Upper Harbor Key in two consecutive seasons. Seagrasses at all sites had chronic percent cover of small epiphytes exceeding 60 %. Additionally, low δ¹³C in T. testudinum tissues at Upper Harbor Key compared to the other sites suggested variations in carbon sources across the study area. Spatial patterns in macrophyte nitrogen-tophosphorus (N:P) ratios point to sources of nutrients from the inhabited islands of the Keys and from the Gulf of Mexico. Water column total nitrogen and total phosphorus concentrations exceeded the numeric nutrient criteria for the study area suggesting that the area should be monitored closely.

Lapointe, B.E.; Herren, L.W., and Bedford, B.J., 2012. Effects of hurricanes, land use, and water management on nutrient and microbial pollution: St. Lucie Estuary, southeast Florida. Multiple hurricanes impacted southeast Florida during 2004 and 2005, producing record rainfall and large-scale stormwater runoff into the urbanized St. Lucie Estuary (SLE). To assess effects on water quality, field samples were taken in June and November 2005 and March 2006 along the SLE's three main segments: the South Fork, connected via the C-44 canal to Lake Okeechobee; the North Fork, which receives residential and agricultural runoff from the C-23 and C-24 canals; and the Middle Estuary, which flows into the Indian River Lagoon and Atlantic Ocean. Salinities were <1‰ throughout the normally brackish estuary during the 2005 samplings, but returned to near-normal levels by March 2006 in all but the South Fork. Low salinities in 2005 correlated with low dissolved oxygen, high turbidity, elevated nitrogen and phosphorus concentrations, and high fecal and total coliform counts. Highest turbidity (84.4 NTU), nitrate (37.9 µM), and total dissolved nitrogen (130.8 µM) concentrations occurred in the South Fork, whereas the highest ammonium (15.4 µM), soluble reactive phosphorus (10.5 µM), and total dissolved phosphorus (13.8 µM) concentrations occurred in the North Fork. High fecal and total coliform counts occurred in tidal creeks adjacent to dense residential areas that rely on septic tanks for on-site sewage disposal. The data suggest that increased stormwater retention, minimization of freshwater releases from Lake Okeechobee, and enhanced treatment of both stormwater and sewage are needed to mitigate future stormwater-driven water quality perturbations in the SLE.