Differential Response of Macrobenthic Abundance and Community Composition to Mangrove Vegetation

Abstract

The mass planting of mangroves has been proposed as a mitigation strategy to compensate for mangrove loss. However, the effects of mangrove vegetation on the abundance and community composition of macrobenthos remain controversial. The macrobenthic communities in four intact mangrove forests with different conditions and the adjacent nonvegetated mudflats of two mangrove species with distinct stand structures on the western coast of Taiwan were examined. Some macrobenthic taxa occurred only in the mangroves, suggesting macrobenthic critical habitats. Seasonal shift in community composition was more pronounced in the mudflats than in the mangroves, possibly due to the rich food supply, low temperature, and shelter function provided by mangrove forests. However, crab density was always lower in the mangroves than in the mudflats. There was a negative relationship between the stem density of Kandelia obovata (S., L.) and infaunal density. The pneumatophore density of Avicennia marina (Forsk.) correlated negatively with epifaunal density. Our results show that the response of macrobenthic abundance and community composition to mangrove vegetation was inconsistent. We reason that mangroves are critical habitats for the macrobenthos in the mudflats. However, if mangrove tree density is high, we predict that the macrobenthic density will decrease. This suggests that at some intermediate level of mangrove tree density, where there are enough mangrove trees to harbor a macrobenthic community but not enough trees to significantly reduce this density, mangroves management can be optimally achieved to promote the presence of a diverse and dense macrobenthic community.

Polychaete Diversity and Functional Trait Composition in Subtropical Mangrove Ecosystems

“…Also, nMDS showed that species composition differed between habitats. We observed similar results to those of Checon et al (2017) [29], Leung (2015) [31], and Pan et al [5]. Many studies, including the present study, show that the presence of vegetation and structural components (such as roots, algal mats, and pneumatophores) significantly changed sediment characteristics.…”

“…In the mangrove ecosystem, prop roots and pneumatophores helped trap detritus and litter, and also weakened wave action to increase sedimentation rates, which resulted in finer sediment and more organic matter [31,54]. The abundance and diversity indices decrease with the increase in root biomass, which may lead to inhibition and reduction in the burrowing behavior and feeding activity [5,31,55]. As reported by Leung (2015) [31] and Checon et al (2017) [29], the density of polychaetes in the mangrove was lower than those in mudflats, and the density of polychaetes was negatively correlated with root biomass.…”

“…There are a number of natural and anthropogenic disturbances that threaten mangroves, including changes in hydrodynamics, subsidence, pollution from industries, clearing of mangrove trees, and climate change [3]. Globally, mangrove areas decline by 0.22% per year [4,5].…”