title: Impacts of a high-discharge submarine sewage outfall on water quality in the coastal zone of Salvador (Bahia, Brazil).
abstract: Carbon and nitrogen stable isotopic signatures of suspended particulate organic matter and seawater biological oxygen demand (BOD) were measured along a coastal transect during summer 2015 to investigate pollution impacts of a high-discharge submarine sewage outfall close to Salvador, Brazil. Impacts of untreated sewage discharge were evident at the outfall site by depleted δ(13)Corg and δ(15)N signatures and 4-fold increased BOD rates. Pollution effects of a sewage plume were detectable for more than 6km downstream from the outfall site, as seasonal wind- and tide-driven shelf hydrodynamics facilitated its advective transport into near-shore waters. There, sewage pollution was detectable at recreational beaches by depleted stable isotope signatures and elevated BOD rates at high tides, suggesting high bacterial activity and increased infection risk by human pathogens. These findings indicate the urgent necessity for appropriate wastewater treatment in Salvador to achieve acceptable standards for released effluents and coastal zone water quality.
authors.affiliation: Coral Reef Ecology Group, Leibniz Center for Tropical Marine Ecology (ZMT), 28359 Bremen, Germany; Faculty of Biology and Chemistry, University of Bremen, 28369 Bremen, Germany; King Abdullah University of Science and Technology (KAUST), Red Sea Research Center, Thuwal 23955-6900, Saudi Arabia. Electronic address: florian.roth@uni-bremen.de.
authors.forename: F
authors.initials: F
authors.lastname: Roth
authors.affiliation: Department of Oceanography, Institute of Geosciences, Federal University of Bahia (UFBA), 40170-110 Salvador, Bahia, Brazil. Electronic address: gclessa@gmail.com.
authors.forename: G C
authors.initials: GC
authors.lastname: Lessa
authors.affiliation: Coral Reef Ecology Group, Leibniz Center for Tropical Marine Ecology (ZMT), 28359 Bremen, Germany; Faculty of Biology and Chemistry, University of Bremen, 28369 Bremen, Germany. Electronic address: christian.wild@uni-bremen.de.
authors.forename: C
authors.initials: C
authors.lastname: Wild
authors.affiliation: Coral Reef and Global Changes Research Group (RECOR), Department of Oceanography, Institute of Geosciences, Federal University of Bahia (UFBA), 40170-110 Salvador, Bahia, Brazil. Electronic address: kikuchi@ufba.br.
authors.forename: R K P
authors.initials: RK
authors.lastname: Kikuchi
authors.affiliation: Coral Reef Ecology Group, Leibniz Center for Tropical Marine Ecology (ZMT), 28359 Bremen, Germany. Electronic address: mnaumann@uni-bremen.de.
authors.forename: M S
authors.initials: MS
authors.lastname: Naumann
mesh_terms: D001938:Brazil; D004784:Environmental Monitoring; D012623:Seawater / Q000382:microbiology; D012722:Sewage; D060753:Water Quality
chemical_list: D012722:Sewage
keywords: Biological oxygen demand; Carbon and nitrogen stable isotopes; Health threat; Marine pollution; Oceanic Disposal System of Rio Vermelho; Shelf hydrodynamics