Fatty acids in an estuarine mangrove ecosystem

Nabeel M Alikunhi,Rajendran Narayanasamy,Kathiresan Kandasamy

doi:10.15517/rbt.v58i2.5230

Abstract

Fatty acids have been successfully used to trace the transfer of organic matter in coastal and estuarine food webs. To delineate these web connections, fatty acid profiles were analyzed in species of microbes (Azotobacter vinelandii, and Lactobacillus xylosus), prawns (Metapenaeus monoceros and Macrobrachium rosenbergii) and finfish (Mugil cephalus), that are associated with decomposing leaves of two mangrove species, Rhizophora apiculata and Avicennia marina. The fatty acids, except long chain fatty acids, exhibit changes during decomposition of mangrove leaves with a reduction of saturated fatty acids and an increase of monounsaturated fatty acids. The branched fatty acids are absent in undecomposed mangrove leaves, but present significantly in the decomposed leaves and in prawns and finfish, representing an important source for them. This revealed that the microbes are dominant producers that contribute significantly to the fishes and prawns in the mangrove ecosystem. This work has proved the fatty acid biomarkers as an effective tool for identifying the trophic interactions among dominant producers and consumers in this mangrove.

Highlights

Mangroves are one among the most productive ecosystems and their productivity is attributed to litter degradation and efficient recycling of nutrients, which are supplied by both autochthonous and allochthonous inputs from natural and anthropogenic sources (Heald 1971, Odum & Heald 1975, Lee 1990, Kathiresan & Bingham 2001)
In the present study we observed an abundance of Azotobacter vinelandii and Lactobacillus xylosus in the decomposing mangrove leaves, besides Metapenaeus monoceros, Macrobrchium rosenbergii and Mugil cephalus
Fatty acids of the lipids are transferred from primary producers to higher trophic levels without significant change and they are used as biomarkers (Parrish et al 2000, Dalsgaard et al 2003)

Summary

Introduction

Mangroves are one among the most productive ecosystems and their productivity is attributed to litter degradation and efficient recycling of nutrients, which are supplied by both autochthonous and allochthonous inputs from natural and anthropogenic sources (Heald 1971, Odum & Heald 1975, Lee 1990, Kathiresan & Bingham 2001). Mangrove litter of low nutritive value is decomposed and converted into nutrient-rich which serves as food for fishes (Odum 1971, Lee 1990, Kathiresan & Bingham 2001, Rajendran & Kathiresan 1998, 1999a, 2000, 2004 & 2007, Ashton et al 1999). (i) leaching of soluble components; (ii) microbial oxidation of refractory components such as cellulose and lignin; and (iii) physical and biological fragmentation with microbial enrichment (Valiela et al 1985). In these processes, the flow of carbon and nitrogen from primary producers to consumers takes place, but the flow is not clearly understood for the mangrove ecosystem.

Methods

Results

Conclusion