Monitoring of SARS-CoV-2 RNA in wastewater: A surveillance tool to foresee infection's evolution in the Mexican Caribbean.

The study aims to determine SARS-CoV-2 RNA in sewage of Cancun wastewater treatment plants, the main touristic destination of Mexico, and to estimate the infected persons during the sampling period. SARS-CoV-2 RNA traces were detected in the inlet of the five plants during almost all the sampling months. However, there is no presence of SARS-CoV-2 RNA traces in the effluent of the five WWTPs during the study period. ANOVA analysis showed differences in the concentrations of RNA traces of SARS-CoV-2 between the sample dates, but no differences were found from one WWTP to another. Estimated infected individuals by Markov chain Monte Carlo simulation are higher (between 77% and 91%) than the cases reported by the health authority. Wastewater monitoring and the estimation of infected individuals are a helpful tool, because estimation provides early warning signs on how broadly SARS-CoV-2 is circulating in the city, and led to the authorities to take measures wisely. PRACTITIONER POINTS: There is no presence of SARS-CoV-2 RNA traces in the effluent of the facilities, suggesting the effectiveness of treatment. Surveillance of viral RNA concentrations at treatment plants revealed presence in the influent of five plants Estimated infected individuals by MCMC simulation are higher than cases reported by health authority Environmental surveillance approach in wastewater influent is helpful to identify the clusters and to take informed decisions.

Lead tolerance of Laguncularia racemosa is associated to high proline accumulation and high antioxidant capacities.

Mangrove forests are threatened by the continuous discharge of inorganic pollutants and studies show that coasts receive high levels of heavy metals, from which lead (Pb) is one of the most persistent and toxic. In the present study, lead accumulation capacity, as well as its toxicological effects and tolerance mechanisms, such as proline accumulation and increased antioxidant capacity were evaluated in two contrasting mangrove species: Avicennia germinans and Laguncularia racemosa. Six-month-old plants were exposed to different concentrations of lead nitrate (0, 75, 150, and 300 µM) and samples of roots and leaves were taken from all treatments at different times during a 30d exposure period. Both species accumulated Pb in their tissues mainly in the roots, but L. racemosa had a greater capacity to accumulate Pb than A. germinans. Nevertheless, lead exposure caused less leaf chlorosis, lower reduction in the efficiency of photosystem II, lower reduction of daily photosynthetic rates, and lower electrolyte leakage in L. racemosa than in A. germinans. In line with those results, L. racemosa, in response to Pb exposure, accumulated more proline and showed higher antioxidant capacity than A. germinans, in both roots and leaves. Altogether, L. racemosa might be more suitable for restoration purposes, as it is not only capable of accumulating more Pb in its tissues but also shows greater tolerance to the stress caused by lead.

Copper accumulation in the aquatic fern Salvinia minima causes more severe physiological stress than zinc.

Copper (Cu) and zinc (Zn) have a high demand in the industry. However, these ions, at high concentrations, can cause severe damage to both fauna and flora. Phytoremediation has gained international importance because its relatively low cost and it is environmentally friendly. The aim of the present study was to evaluate the capacity of Salvinia minima of accumulating Cu and Zn from aqueous solutions of various external concentrations (20, 40 and 80 µmol L-1 of CuSO4 and ZnSO4, separately). In addition, to estimate the effect of exposure of S. minima plants to those metals, on various physiological parameters (growth potential, maximum quantum efficiency of PSII, electrolyte leakage: as a cell membrane integrity index). S. minima was able of accumulating more Zn than Cu in its tissues, reaching values of 6.96 mg Cu g-1 dry weight (DW) and 19.6 mg Zn g-1 DW when exposed to 80 µM of each metal during 96 h, that were stored mainly at roots. Despite accumulating less Cu in its tissues, Cu had more severe reductions in various physiological parameters than Zn (in maximum quantum efficiency, integrity of cell membranes, and growth). We conclude that this species can be useful in the phytoremediation for copper and zinc in relatively short time, as maximum accumulation occurred within the first 24 h. However, in the long term, the accumulation of such metals is accompanied by a negative impact in the appearance, physiology, and growth of this plant species, which was more severe for copper exposure than for zinc.

Recruitment and Succession in a Tropical Benthic Community in Response to In-Situ Ocean Acidification.

Ocean acidification is a pervasive threat to coral reef ecosystems, and our understanding of the ecological processes driving patterns in tropical benthic community development in conditions of acidification is limited. We deployed limestone recruitment tiles in low aragonite saturation (Ωarag) waters during an in-situ field experiment at Puerto Morelos, Mexico, and compared them to tiles placed in control zones over a 14-month investigation. The early stages of succession showed relatively little difference in coverage of calcifying organisms between the low Ωarag and control zones. However, after 14 months of development, tiles from the low Ωarag zones had up to 70% less cover of calcifying organisms coincident with 42% more fleshy algae than the controls. The percent cover of biofilm and turf algae was also significantly greater in the low Ωarag zones, while the number of key grazing taxa remained constant. We hypothesize that fleshy algae have a competitive edge over the primary calcified space holders, coralline algae, and that acidification leads to altered competitive dynamics between various taxa. We suggest that as acidification impacts reefs in the future, there will be a shift in community assemblages away from upright and crustose coralline algae toward more fleshy algae and turf, established in the early stages of succession.