Composition, biomass and secondary production of the macrobenthic invertebrate assemblage in a mangrove forest in Nayband Bay, Persian Gulf

Abstract

Nayband Bay is a unique protected area located on the Iranian coast of the Persian Gulf. The bay supports a diverse macrobenthic assemblage; studying the biomass and secondary production of such a habitat can offer insights into the ecosystem’s patterns and processes. In total, 18 benthic sampling sites were taken from six sites along the bay between May 2016 and February 2017. Macrozoobenthos assemblages comprised 60 taxa; among them, gastropods accounted for much of the overall biomass and secondary production. The mean annual biomass of macrobenthos was found to be 1974.68 mg AFDW m−2, while the secondary production was 8.04 mg m−2 y−1. Secondary production values appeared to increase during winter (14.21 mg m−2 day−1) and decrease in spring (4.59 mg m−2 day−1); such seasonal differences were primarily dependent on the presence of different groups of macrobenthos. The annual mean production-to-biomass (P/B) ratio was 6.93, a value that increased from cold seasons to warm seasons. This means that in summer and spring, polychaetes (with smaller species) were the dominant group of macrobenthos. Conversely, in winter, gastropods and crustaceans (with large species) were the dominant group and increased macrobenthic production. High temperature and drought were the main reasons for the decreased density of macrobenthos during the warm seasons. However, a significant reduction in the abundance of macrobenthos was also observed in areas where road construction prevented direct contact between the mangrove trees and the marine tidal system. This could explain the deficient levels of biomass and secondary production among the macrobenthos groups in the area. The results of this study indicate that human activities, like construction, in mangrove forests can reduce both the density of macrobenthos and their rates of secondary production. Therefore, proper management is essential to sustainable anthropogenic development in mangrove forests.