Interannual salinity in a Coastal lagoon of Oaxaca, Mexico: Effects on growth of Black mangrove

Abstract

“La Salina” lagoon in Oaxaca, Mexico, is a habitat of black mangrove that tolerates up to 65 g L-1 of salt. In dry seasons the salinity increases to extreme levels and stops the growth and spatial distribution of black mangrove. The objective of this study was to determine the chemical and saline variation of the soil and lake water, and their influence on the growth of the mangrove. Methodology: the distribution of black mangrove in the lake was studied during an interannual rainy-dry period. In the field, soil and water samples were collected. In the laboratory, their physic-chemical properties and saline concentrations were evaluated. Using the central point method, the number of trees was determined in units of 100 m2 and measured their height, normal diameter, canopy diameter and foliar biomass. Results: The salinity of the lagoon is hydrochloric. In humid conditions three salt gradients were determined: 16.77 dS m-1 (level I), 29.42 dS m-1 (level II) and 46.29 dS m-1 (level III), tolerated by the mangrove. In dry grows optimally in gradients I (23.03 dS m-1) and II (54.62 dS m-1); however in gradient III (86.21 dS m-1) limited its production of biomass and spatial distribution. Conclusion: hypersalinity affects the survival of the black mangrove.