Vergara-Carranza, C., N., López & A., Piñón-Gimate (2024). Use of intertidal macroalgae as bioindicators of anthropogenic nutrient disturbance in the rocky coasts of the tropical central Mexican Pacific. Ciencias Marinas. 50(1A): e3416. DOI: 10.7773/cm.y2024.3416.
Careli Vergara-Carranza 1, Norma López 1 y Alejandra Piñón-Gimate 2
Bahía de Zihuatanejo, Mexico,exhibits disturbances in its rocky shores due to large amounts of nutrientsthat enter the sea due to urbanization and mass tourism. These nutrients aretraced in macroalgae using stable isotopes. The objective of this study was touse 4 species of macroalgae as bioindicators to infer nutrient sources in thesystem through d15N and the elemental nitrogen (N) content. Sampleswere collected in the rainy and dry seasons of 2021 at 3 sites in theZihuatanejo region: La Madera, Las Salinas, and La Majahua. Water samples weretaken at each site and season to determine nitrate (NO3) and phosphate (PO4) concentrations. Isotopic signals and N contentwere evaluated in Hypnea spinella, Padina gymnospora, lva intestinalis, and Ulva lactuca for each site and season. Theconcentrations of NO3 and PO4, which were highest at Las Salinas and showed no differences between La Madera and La Majahua, were similar to those previouslyreported for the region. The highest d15N signals were found in U. intestinalis and H. spinella at Las Salinas (16.12‰ and 15.38‰,respectively) and La Madera (15.12‰ and 13.58‰, respectively) and were close tothe isotopic wastewater signal. In La Majahua, low signals were obtained for H. spinella (13.54‰), P. gymnospora (9.24‰), and U. lactuc (8.24‰),with values that were close to the isotopic signal of nutrient-rich oceanicwaters. The N content varied depending on the species and site, although it wasgenerally higher at Las Salinas. The isotopic signals agreed with thosereported for anthropogenic and natural nutrient-enriched coasts. The species U. intestinalis and H. spinella can be used as bioindicators ofanthropogenic disturbance due to sewage discharge in the region.
Palabras clave: Macroalgae; bioindicators; stable isotopes; contamination; Tropical Mexican Pacific
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