Microbial flora associated with submerged mangrove leaf litter in India

Abstract

Abstract:We studied the microbial flora in decomposing mangrove leaves in relation to changes in nitrogen and tannin levels, and in penaeid prawn assemblages. Senescent leaves of two mangrove species (Rhizophora apiculata and Avicennia marina) kept in nylon bags, were separately immersed for 80 days in five tanks full of mangrove water. A known amount of decomposing leaves was collected every ten days from each tank for microorganism counts, total nitrogen and tannin measurement, and juvenile penaeid prawn counts. Five genera of total heterotrophic bacteria (THB), three species of azotobacters and 19 species of fungi were identified. The azotobacters showed a significant peak around 40-50 days after the beginning of of decomposition, similar to the trend for total nitrogen and for prawn assemblages. Rev. Biol. Trop. 55 (2): 393-400. Epub 2007 June, 29.Key words: Rhizophora, Avicennia, litter, microbes, decomposition, Azotobacter.Microorganisms play an important ecological role in decomposing organic matter and producing protein-rich detritus that serves as food to fishes especially in detritus-based marine ecosystems like mangroves (Dickinson and Pugh 1974, Steinke 2000, Mumby et al. 2004. Fungi are particularly important in the marine environment as decomposers of dead organic substrates (Kohlmeyer and Kohlmeyer 1979). The dead organic matter and the associated microorganisms form the base of the food webs of commercially important fishes and crustaceans. The undecomposed leaves are poor in nutrients, and they become nutritious due to the microbial enrichment process during decomposition (Odum 1971). The microbial decomposition of mangrove litter, has been extensively studied (Fell and Master 1973, Meyers 1974, Fell et al. 1975, Boonruang 1978, Cundell et al. 1979, Misra et al. 1984, Robertson 1988, Raghukumar et al. 1994, Rajendran and Kathiresan 1999a, 2000, Kathiresan and Bingham 2001, Rajendran and Kathiresan 2004 especially for the prevalence of fungi in decaying seedlings (Newell 1976). The microbial activity results in mineralization of detritus and a decrease in C/N ratio (Blum et al. 1988).Although microbes play an important role in the cycling of nutrients in the mangrove ecosystem, very little information is available about the types of microbes associated with decomposing leaves. These studies have not been extended to faunal assemblages associated with the decomposing leaves, especially for juvenile penaeid prawns which are usually abundant in mangrove waters (Rajendran 1997, Rajendran and Kathiresan 1999b. Hence, the present study was made on microbial load during decomposition of two mangrove species. mangrove forest at Pichavaram (11°27' N, 79°47' E) located in southeast coast of India and shade-dried. The leaves weighing at 500 g, without dissection, were packed in five nylon bags (35 x 35 cm, 2 mm mesh size) and submerged in five tanks (1.5 x 1.0 m), which were constructed separately for Rhizophora and Avicennia in the lower intertidal areas adjacent to the mangrove forest. To facilitate the b...

Experimental determination of stable carbon and nitrogen isotope fractionation between mangrove leaves and crabs

“…Avicennia spp. (Kathiresan 2003, Rajendran & Kathiresan 2007, the crabs in our experiments preferred the former, which indicates that tannins are of minor importance in food choice.…”

Sunlight and sediment improve the environment of a litter biofilm-based shrimp culture system

“…Ecological shrimp aquaculture in mangrove systems has gained environmental support because of its tendency to conserve the mangrove forest (Primavera 1998, Fitzgerald 2000 by rearing fish without clearing mangrove trees (Primavera 1998). This integrated approach implies that the shrimp culture system constantly intercepts mangrove litter fall, which proceeds to decompose under the influence of the microbiota present in the biofilm (Benner & Hodson 1985, Rajendran & Kathiresan 2007. The mangrove trees also shade the shrimp culture system from direct sunlight either partially or completely.…”

?Seasonal Variation of Litter Accumulation And Putrefaction With Reference To Decomposers In A Mangrove Forest From Karachi, Pakistan?.

“…The fungal and bacterial colonies were estimated using the methods of Rajendran and Kathiresan (2007). Triplicates of petri plates were incubated at 32 °C for 5 to 7 days in an incubator.…”