Alkaline Phosphatase: An Appraisal of its Critical Role in C-Limited Deep-Sea Sediments of Central Indian Basin

ABSTRACT

Alkaline phosphatase (ALP) is a hydrolase that releases phosphate, a crucial nutrient supporting formation of many macromolecules. The oligotrophic sediments of Central Indian Basin (CIB) were examined for the extent of ALP activity in 20 cores up to 20 cm depth along with other biogeochemical parameters. Northern and southern stations distinctly clustered based on pore water phosphorus (P) concentrations. ALP appeared more active in south due to more P and organic carbon (C) limitation. Central transition profiles revealed interesting mixed diagenetic and geothermal influence. Inter- and intrazonal differences suggest that broadly established paradigms applicable to water columns may deviate in space and time in sedimentary systems. Gross differences in redox status could govern differential response in ALP activity under similar hydrostatic pressure. Hydrothermal scavenging reactions striping soluble P from pore water might be widespread in CIB albeit at extreme low intensities. ALP might redissolve the precipitated P and make it reavailable to microbes.

KEYWORDS:

• Alkaline phosphatase
• Central Indian Basin
• microbial
• MUF-phosphate
• pore water

Acknowledgments

The authors are grateful to the ex-Directors, Dr. S.R. Shetye and Dr. S.W.A. Naqvi, CSIR-National Institute of Oceanography (NIO), Dona Paula, Goa, India, for their encouragement. The constant support of the project team of “Environmental studies for nodule mining in Central Indian Basin”, and the crew of Akademic Boris Petrov Cruises 4 (2005), 26 (2006-07), 38 (2009) are acknowledged. Shri S. Jaishankar is acknowledged for preparation of the base map. A.V. Sijin Kumar, T.C.Vineesh, Trupti Naik, Rupali Naik and Poonam Malik have performed the on-board pore-water extraction and analyses. B.S. Mourya is gratefully acknowledged for pore-water iron measurements in two stations. The support and encouragement of Dr. K.M. Paknikar (Director, MACS-Agharkar Research Institute, Pune, India) and Dr. P.K. Dhakephalkar (Sci. F, MACS-ARI, Pune, India; mentor to AD) have significantly helped during the manuscript revisions.

Funding

The authors are thankful to the Ministry of Earth Sciences (MoES) and Council of Scientific and Industrial Research (CSIR), Government of India for funding the Projects GAP 2128 and GEOSINKS respectively. PAL acknowledges CSIR, New Delhi, for the Emeritus-Scientist fellowship. AD acknowledges CSIR, New Delhi for funding her research work at NIO as JRF-SRF and RA; and DST-SERB, New Delhi for funding fast-track scientist fellowship. This paper is NIO's contribution no. 5889