title: Nitrogen isotopic characterisation of macroalgae blooms from different sites within a subtropical bay in the Gulf of California.
abstract: In La Paz Bay conspicuous macroalgal blooms of Ulva spp. are recurrent in the waterfront of the city; studies relate its growth to seasonality and nutrient enrichment but their relative influence is not known. We use the δ15N to discern amongst nitrogen sources at three sites with different substratum and anthropogenic activities. Ulva blooms were monitored monthly at San Juan de la Costa (SJC), Casa del Marino (CM) and El Tecolote (TE). Species presence varied between sites and months. At SJC Ulva displayed the highest signal of δ15N associated with fishing products and local mining wastewaters (19.5‰). CM showed isotopic values related to sewage waters (13‰). The δ15N of species at TE were the lowest. We found higher isotopic signatures than in other tropical/subtropical regions, associated with nutrient rich water masses. Ulva species can be used to trace and discern amongst different sources of nitrogen from natural or anthropogenic sources.
authors.affiliation: Centro Interdisciplinario de Ciencias Marinas, Instituto Politécnico Nacional (CICIMAR-IPN), Av. Instituto Politécnico Nacional s/n, Col. Playa Palo de Santa Rita, La Paz, Baja California Sur, C.P. 23096, Mexico. Electronic address: ale_pinion@hotmail.com.
authors.forename: Alejandra
authors.initials: A
authors.lastname: Piñón-Gimate
authors.affiliation: Universidad Autónoma de Baja California Sur, Carretera al Sur KM 5.5, Apartado Postal 19B, C.P. 23080, La Paz, Baja California Sur, Mexico.
authors.forename: Noemi
authors.initials: N
authors.lastname: Espinosa-Andrade
authors.affiliation: Centro Interdisciplinario de Ciencias Marinas, Instituto Politécnico Nacional (CICIMAR-IPN), Av. Instituto Politécnico Nacional s/n, Col. Playa Palo de Santa Rita, La Paz, Baja California Sur, C.P. 23096, Mexico.
authors.forename: Alberto
authors.initials: A
authors.lastname: Sánchez
authors.affiliation: Centro Interdisciplinario de Ciencias Marinas, Instituto Politécnico Nacional (CICIMAR-IPN), Av. Instituto Politécnico Nacional s/n, Col. Playa Palo de Santa Rita, La Paz, Baja California Sur, C.P. 23096, Mexico.
authors.forename: Margarita
authors.initials: M
authors.lastname: Casas-Valdez
mesh_terms: D061006:Bays; D004784:Environmental Monitoring; D005068:Eutrophication; D008800:Mexico; D009584:Nitrogen / Q000032:analysis*; D009587:Nitrogen Isotopes / Q000032:analysis; D012624:Seaweed; D044445:Ulva
chemical_list: D009587:Nitrogen Isotopes; D009584:Nitrogen
keywords: Isotopes; Nutrient rich water masses; Nutrients; Sewage; Ulva