A TP levels and adenylate energy charge in soils of mangroves in the Andamans

Abstract

Adenosine 5' -triphosphate (ATP) is considered to be a useful indicator of life in soil and the adenylate energy charge (AEC) indicates the energetic status of soil microorganisms. A TP concentration and AEC levels have been extensively studied in a diverse group of soils. However, little knowledge is available on the levels of ATP and AEC in soils of mangroves. We report here the levels of adenylates ATP, adenosine di-phosphate (ADP) and adenosine monophosphate (AMP)) and AEC in soils of undisturbed mangroves of South-, Middle-, North- and Little-Andamans. Relevant soil physico-chemical and microbial parameters and their relationship to ATP and AEC were also examined. A veraged across various mangrove sites, total N level was 1.44 ± 0.13 g kg-I, organic C 15.6 ± 1.5 g kg-I, microbial biomass C 410 ± 35 )lg kg-I, microbial biomass N 34 ± 2 )lg kg-l and qC02 41.1 ± 4.4 mg CO2 (g biomass crl d-l. Among the adenylates, ATP rangedfrom 2.32 to 3.22 nmol g-l (mean 2.87 ± 0.29), AMP from 0.21 to 0.29 nmol g-l (mean 0.25 ± 0.03) and ADP from 0.41 to 0.48 nmol g-l (mean 0.44 ± 0.03). Across sites, the average microbial biomass C/organic C ratio was 2.6 ± 0.2% and microbial biomass C/N ratio at the mangrove sites was wider and ranged from 11.2 to 14.5 with a mean of 12.0 ± 0.9. The ATP/microbial biomass C ratio ranged from 6.0 to 8.2 )lmol g-l with a mean of 7.0 ± 0.6 )lmol g-I, markedly lower than the worldwide average of 10-12 )lmol g-l reported in a wide range of soils. Lower ATP/microbial biomass C ratio in our mangrove soils is most likely due to a changed microbial community structure indicating a decomposition pathway dominated by fungi and microorganisms with large microbial biomass C/N ratio. The AEC levels were consistently >8.0 (mean 0.87) at all the sites, suggesting that the majority of microorganisms in these mangrove soils are probably dormant.