Evaluating the stable isotopic composition of phosphate oxygen as a tracer of phosphorus from waste water treatment works

Eutrophication is a globally significant challenge facing freshwater ecosystems and is closely associated with anthropogenic enrichment of phosphorus (P) in the aquatic environment. Phosphorus inputs to rivers are usually dominated by diffuse sources related to farming activities and point sources such as waste water treatment works (WwTW). The limited availability of inherent labels for different P sources has constrained understanding of these triggers for eutrophication in natural systems. There have been substantial recent advances in the use of phosphate oxygen isotopes (δ18OPO4) as a way of understanding phosphate sources and processing. Results from all previous studies of the δ18OPO4 composition of WwTW effluent and septic tanks are combined together with significant new data from the UK to assess δ18OPO4 compositions in waste water sources. The overall average δ18OPO4 value is 13.9‰, ranging from 8.4 to 19.7‰. Values measured in the USA are much lower than those measured in Europe. A strong positive correlation exists between δ18OPO4 and δ18OH2O, suggesting biologically-mediated exchange between the water molecules and the phosphate ions. A comparison of δ18OPO4 and the offset from isotopic equilibrium showed a strong positive linear correlation (ρ = 0.94) for the data from Europe but no relationship for the historic USA data which may be due to recent advances in the extraction procedure or to a relative paucity of data. This offset is most strongly controlled by the δ18OH2O rather than temperature, with greater offsets occurring with lower δ18OH2O. Time series data collected over 8-24 hours for three sites showed that, although there were significant changes in the phosphate concentration, for a given WwTW the δ18OPO4 stayed relatively constant. Two new studies that considered instream processing of δ18OPO4 downstream of WwTWs showed mixing of the upstream source with effluent water but no evidence of biological cycling 3 km downstream. It is suggested that δ18OPO4 can be an effective tool to trace P from WwTWs provided the source of the effluent is known and samples are collected within a day

The role of charophytes in a Mediterranean pond created forrestoration purposes

A small, shallow basin was created and flooded with groundwater in a Reserve Area in Albufera de València Natural Park (AVNP) under the scope of a restoration program intended to mimic typical environments such as freshwater springs, abundant in the past but currently suffering from deterioration (desiccation, pollution, etc.), with the ultimate goal of increasing local biodiversity of submerged macrophytes, particularly charophytes. In this study we have monitored, from April 2009 (a few months after its first flooding) to September 2012, the dynamics of charophyte growth and related physical, chemical and biotic variables to highlight the factors determining charophyte success. Just after flooding, five charophyte species grew spontaneously when oospores germinated in the sediments. Chara hispida populations largely dominated the community and developed dense meadows that covered virtually the entire pond floor. Charophytes exerted a negative influence on phytoplankton densities, increasing water transparency. C. hispida stands precipitated substantial CaCO3 in the form of incrustations on the plants, accompanied by coprecipitation of inorganic phosphorus, maintaining low concentrations of soluble P in the water. Reduced groundwater inflow, increased salinity, nutrient concentration, turbidity and augmented feeding pressure by waterfowl, separately or by synergistic effects, considerably reduced charophyte development during the final year of the study; however, charophytes still represent one of the most extensive and dense stands of submerged vegetation within AVNP, verifying the achievement of the goal of the restoration plan. The knowledge obtained has allowed us to recommend several measures to counteract the decrease of charophytes, which can also be applied in other regions affected by the same stressors. © 2014 Elsevier B.V. All rights reserved.The authors express thanks for the funding of this study by TRAGSA and Confederacion Hidrografica del Jucar (J. Ferrer, T. Estrela, M. Regidor) and by the Spanish Ministry of Economy and Competitiveness (research project CGL2009-10292, including plan E). We also thank Fidel Rubio, Jara Garcia-Chicote, Fran Cortes, Sara Calero and William Colom for their help during field and laboratory work. We also thank Matthieu Lassalle, Lucia Moreno and Lurdes Ribera (Tancat de la Pipa staff), particularly for providing data on inflows and water depth. We are grateful for the collaboration of the other members of the research group from Instituto de Ingenieria del Agua y Medio Ambiente (Polytechnic University of Valencia) and of Mario Gimenez from SEO/Birdlife. The waterfowl censuses were part of the SEO/BirdLife's Bird Monitoring Program in AVNP, supported by the Alas sobre Agua Project and with the valuable help of many volunteers. Joan M. Benavent facilitated the aerial photography of the pond. Dominique Auderset-Joye made constructive comments on the manuscript. American Journal Experts carefully reviewed the English language of the manuscript.Rodrigo, MA.; Rojo, C.; Segura, M.; Alonso Guillén, JL.; Martín Monerris, M.; Vera García, P. (2015). The role of charophytes in a Mediterranean pond created forrestoration purposes. Aquatic Botany. 120:101-111. doi:10.1016/j.aquabot.2014.05.004S10111112