Program
 
General Session 4: Marine environment, ecosystem & sustainability
 
 
 
Poster
Mangroves, heavy metals and the food chain: Do crabs choose between contaminated and non-contaminated leaves?
GS4-30-S
João Marcelo Silva* , Universidade Federal do ABC, Santo Andr¨¦-SP, Brazil.
Gray A. Williams, The Swire Institute of Marine Sciences and School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong.
Stefano Canicci, The Swire Institute of Marine Sciences and School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong.
Ronaldo Adriano Christofoletti, Departamento de Ci¨ºncias do Mar, Universidade Federal de São Paulo, Santos-SP, Brazil.
Presenter Email: j.msilva@yahoo.com.br
Although Hong Kong mangroves represent a highly diverse and functional intertidal habitat they are subject to strong impacts from multiple anthropogenic stressors, including heavy metal pollution. Here we assess the role of mangrove trees in the transfer of heavy metals to consumers at polluted and non-polluted sites in Hong Kong. Heavy metals are a complex and resilient group of elements which accumulate in sediments where they become bioavailable and potentially toxic to plants whose metabolic responses to these stressors are species-specific. Such plant-specific responses will be reflected in the nutritional quality of leaves and may therefore affect the diet-choice of their consumers (e.g. grapsoid crabs). By evaluating the concentration of eight metals in mangrove sediments, leaves from trees (i.e. Kandelia obovata and Avicennia marina) and the soft tissues of two crabs (i.e. Perisesarma bidens and Metopograpsus frontalis) from four different mangrove sites (two heavily polluted and two relatively pristine) in two different seasons, we were able to identify spatio and temporal variability in trophic transfer of heavy metals through this link of the mangrove ecosystem. To date our analysis reveals accumulation of some metals in both plant (Al, Mn and Fe) and crab (Al, Fe, Zn) species with variations between sites and within site areas. The transfer factors between plants and crabs show that P. bidens accumulates Cu, Fe and Zn from K. obovata and Al, Cu and Zn from A. marina. The enrichment factors between plants from polluted and pristine sites reveal that both species accumulate metals in a higher rate at the polluted sites. Feeding preference experiments showed no interactions between heavy metal content of leaves and crab choices. Assimilation rates through the analysis of leaves and fecal material are in progress to shed light on the interplay of these processes on the transfer of heavy metal contaminants in Hong Kong’s mangroves.