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The anthropogenic deterioration of aquatic ecosystems affects water resources due to agricultural malpractices, pollution from domestic septic tanks, recreational activities, and poor watershed management, among other factors. This study examines the management of Las Curias Reservoir, San Juan, Puerto Rico, after the 2016 arrival of the invasive aquatic fern Salvinia molesta. In September 2019, a community-led initiative introduced the Cyrtobagous salviniae weevil, an effective biological control agent for S. molesta, and commenced a mechanical removal campaign using an aquatic harvester. Limnological sampling (September 2019 to September 2022) and drone flights were employed to measure physicochemical and floating plant cover changes, respectively, in the reservoir. Monitoring of weevils in the reservoir demonstrated rapid establishment and dispersal, which resulted in visible damage including browning of plants and eventually sinking of entire mats. From 23 July 2019, the reservoir surface was predominantly covered by salvinia, occupying an area of 17.7 ha (100% coverage). This coverage decreased to 12.6 ha (71%) by 29 January 2021. By 12 August 2022, the coverage had been substantially reduced to just 1.1 ha, representing only 6% of the reservoir surface. In 2022, the reservoir recorded an average dissolved oxygen concentration of 2.4 mg L−1 (±0.0, n = 144), the highest in the study period and indicative of ecosystem recovery. After three years of control efforts, dissolved oxygen, pH, and specific conductance returned to levels recorded prior to Salvinia molesta introduction. This ecosystem recovery, a first in Puerto Rico, could be attributed to early use of mechanical control and the long-term impact of biological control. [ABSTRACT FROM AUTHOR]

Pelagic Sargassum beaching events are a global environmental issue that have caused increasing detrimental effects to coastal ecosystems since the 1970s. The 2015 pelagic Sargassum bloom in the Atlantic and the Caribbean caused significant impacts to coastal ecological communities in these areas. In enclosed systems, such as bays and lagoons, the Sargassum impacts could be particularly problematic due to the longer water residence times. An example of such an ecosystem is Laguna Grande bioluminescent lagoon, Puerto Rico. This lagoon slowly exchanges water with the ocean through a narrow channel (average about 5 m across), which results in the accumulation of the bioluminescent dinoflagellate Pyrodinium bahamense and other planktonic organisms. In this study we describe the 2015 pelagic Sargassum accumulation event in Laguna Grande, and report associated changes in the phytoplanktonic composition. Before this event, other studies conducted between 2003 and 2013 reported mean densities of P. bahamense ranging from 14,492 to 28,202 cells/L. However, the P. bahamense population was absent from the lagoon during the 2015 Sargassum influx. After the entrance of large quantities of pelagic Sargassum into the lagoon, accompanied with other marine algae and sea grasses, the macrophytes remained inside and began to decompose. Thirteen phytoplankton taxa not previously observed inside the lagoon were detected after the entrance of the macrophytes. We hypothesize that the changes in the phytoplanktonic composition in the lagoon were caused by altered water quality conditions following the entrance of the pelagic Sargassum and other macrophytes. [ABSTRACT FROM AUTHOR]

Exposure to the anthropogenic chemicals known as endocrine disrupting compounds (EDCs) may result in negative biological effects. Low levels of EDCs in the environment aggravate the problem as exposure is constant. Urban areas concentrate pollution as greater volumes are released from human activities. Water for public supply is particularly vulnerable as the sewage treatment facilities may not eliminate EDCs. The goal was to assess estrogenicity and effectiveness of removal of phthalates in primary and tertiary wastewater treatment facilities in urban cities in the tropical island of Puerto Rico. A yeast bioassay used to measure estrogenicity showed higher removal with tertiary treatment. However, results in the picomolar range suggest low doses of estrogenic compounds were being released to receiving waters. For the phthalates, solid phase extraction and gas chromatography-mass spectrometry analyses revealed removals ranging from 42.9% to 92.4% with tertiary treatment. More than 90% removal was achieved for benzylbutyl phthalate, dibutyl phthalate and bis-2-ethylhexyl phthalate. However, concentrations ranging from 0.86 to 1.29 ppm for the phthalates in the outflow were detected even at the tertiary waste water treatment plant effluent implying failure of EDC removal. These results can assist managers in evaluating pollution control technologies to ameliorate the impacts of EDCs in the tropics. [ABSTRACT FROM AUTHOR]

Increased urbanization in many tropical regions has led to an increase in centralized treatment of sewage effluents. Research regarding the effects of these wastewater treatment plants (WWTPs) on the ecology of tropical streams is sparse, so we examined the effects of WWTPs on stream water quality on the Caribbean island of Puerto Rico. Nutrient concentrations, discharge, dissolved oxygen (DO), biochemical oxygen demand (CBOD5), and specific UV absorbance (SUVA) at 254 nm were measured upstream from the WWTP effluent, at the WWTP effluent, and below the WWTP effluent. All parameters measured (except DO) were significantly affected by discharge of WWTP effluent to the stream. The values of SUVA at 254 nm were typically lower (<2.5 m-1 mg L-1) in WWTP effluents than those measured upstream of the WWTP, suggesting that WWTP effluents are contributing labile carbon fractions to receiving streams, thus changing the chemical composition of dissolved organic carbon in downstream reaches. Effluents from WWTP contributed on average 24% to the stream flow at our tropical streams. More than 40% of the nutrient loads in receiving streams came from WWTP effluents, with the effects on NO3--N and PO4--P loads being the greatest. The effect of WWTPs on nutrient loads was significantly larger than the effect of flow due to the elevated nutrient concentrations in treated effluents. Our results demonstrate that inputs from WWTPs to streams contribute substantially to changes in water quality, potentially affecting downstream ecosystems. Our findings highlight the need to establish nutrient criteria for tropical streams to minimize degradation of downstream water quality of the receiving streams. [ABSTRACT FROM AUTHOR]

The ecologically unique forest ecosystems of the Luquillo Mountains in Eastern Puerto Rico and the scenic value of its forests, rivers and surrounding beaches have promoted population growth, tourism and light industry, thus increasing regional water demands. In light of further increases in future water demand, integrated water resources management (IWRM) initiatives are rapidly evolving in this area. In an effort to seek international collaboration and information exchange on IWRM, the Luquillo Mountains joined the Hydrology for the Environment, Life, and Policy (HELP) Programme of the United Nations Educational, Scientific, and Cultural Organization (UNESCO)/International Hydrological Programme (IHP) in 1999. This paper was prepared to document existing IWRM efforts and to promote internal discussion for further IWRM development in the region. [ABSTRACT FROM AUTHOR]