Effects of Fiddler Crab Burrows on Sediment Properties in the Mangrove Mudflats of Sungai Sepang, Malaysia.

Mohammad Mokhtari,Gires Usup,Mazlan Abd Ghaffar,Zaidi Che Cob

doi:10.3390/biology5010007

Mohammad Mokhtari, Gires Usup + Show 2 more

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https://doi.org/10.3390/biology5010007

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Abstract

In mangrove ecosystems, litter fall accumulates as refractory organic carbon on the sediment surface and creates anoxic sediment layers. Fiddler crabs, through their burrowing activity, translocate oxygen into the anoxic layers and promote aerobic respiration, iron reduction and nitrification. In this study, the effects of four species of fiddler crabs (Uca triangularis, Uca rosea, Uca forcipata and Uca paradussumieri) on organic content, water content, porosity, redox potential and solid phase iron pools of mangrove sediments were investigated. In each crab’s habitat, six cores down to 30 cm depth were taken from burrowed and non-burrowed sampling plots. Redox potential and oxidized iron pools were highest in surface sediment, while porosity, water and organic content were higher in deeper sediment. Reduced iron (Fe (II)) and redox potential were significantly different between burrowed and non-burrowed plots. Crab burrows extend the oxidized surface layer down to 4 cm depth and through the oxidation effect, reduce the organic content of sediments. The effects of burrows varied between the four species based on their shore location. The oxidation effect of burrows enhance the decomposition rate and stimulate iron reduction, which are processes that are expected to play an important role in biogeochemical properties of mangrove sediments.

Highlights

Mangrove sediments are important sinks for organic carbon [1,2,3,4,5]
In almost all sampling plots, sediment porosity, water content and organic matter (OM) increased with increasing depth, while redox all potential, sediment density and oxidized were and higher surface sediments
The results of this study revealed that redox potential and reduced iron pools were significantly different between burrowed and non-burrowed sediments

Summary

Introduction

Mangrove sediments are important sinks for organic carbon [1,2,3,4,5]. Litter fall represents the major organic carbon input into the mangrove sediment [7]. Due to poor nutritional value and high amounts of tannin, lignin and cellulose in mangrove detritus, microbial decomposition is slow, especially under anaerobic conditions [8]. The oxic zone of mangrove sediment, anaerobic microorganisms mediate much of the oxidation of carbon [10]. Sulfate reduction is a dominant decomposition pathway in unbioturbated mangrove sediments [11].

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