Secondary productivity in the estuaries of El Mogote sand bar in Ensenada de La Paz, Baja California Sur, Mexico

Abstract

Mangrove ecosystems are critical habitats for many species, and their productivity is important because of their contribution of organic detritus and secondary production. The objective of this study was to identify suitable indicators of secondary productivity of mangrove systems, in order to establish a baseline for measuring changes in the mangrove system due to natural or anthropogenic potential disturbances. The bivalve mollusks chosen as indicators of secondary productivity were the mangrove cockle Anadara tuberculosa and the mangrove oyster Crassostrea palmula. Samples were collected in three estuaries from August 2007 to July 2009. Abundance and secondary production were estimated from biomass increase, calculated from individual growth rates determined using length frequency distributions analysis. The average abundance was 1.27 and 510 ind · m-2 of mangrove cockle and mangrove oyster respectively. It was estimated a growth rate of 4.91 mm · month-1 (3.67 g · month-1 ) for mangrove cockle and 3.80 mm · month-1 (0.18 g · month-1 ) for the mangrove oyster. The mean secondary production of mangrove cockle was 4.51 g · m-2 · month-1 and was higher during spring, while for the mangrove oyster it was 97.9 g · m-2 · month-1 , and the maximum production was recorded during summer. The results show that these indicators of benthos quality are suitable for measuring changes of the mangrove system in the Ensenada of La Paz, B. C. S., Mexico.