Nutrient dynamics of seasonal tanks in the dry zone of Sri Lanka in relation to their hydrological regimes

Jayakody, B.V.P.L. and Murray, F.J. and Little, D.C. and Mowjood, M.I.M. (2002) Nutrient dynamics of seasonal tanks in the dry zone of Sri Lanka in relation to their hydrological regimes. Stirling, Scotland, Institute of Aquaculture, University of Stirling,

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Abstract

Village tanks are put to a wide range of uses by the rural communities that depend on them for their survival. As the primacy of irrigation has decreased under these tanks due to a variety of climatic and economic reasons there is a need to reevaluate their use for other productive functions. The research presented in this paper is part of a programme investigating the potential to improve the management of living aquatic resources in order to bring benefits to the most marginal groups identified in upper watershed areas. Based on an improved typology of seasonal tanks, the seasonal changes and dynamics of various water quality parameters indicative of nutrient status and fisheries carrying capacity are compared over a period of one year. Indicators of Net (Primary) Productivity (NP): Rates of Dissolved Oxygen (DO) change, Total Suspended Solids (TSS): Total Suspended Volatile solids (TVSS) ratios are the parameters of principle interest. Based on these results a comparative analysis is made on two classes of ‘seasonal’ and ‘semi-seasonal’ tanks. Results indicate a broad correlation in each of these parameters with seasonal trends in tank hydrology. Highest productivity levels are associated with periods of declining water storage, whilst the lowest levels are associated with the periods of maximum water storage shortly after the NW monsoon. This variation is primarily attributed to dilution effects associated with depth and storage area. During the yala period, encroachment of the surface layer by several species of aquatic macrophyte also has progressively negative impacts on productivity. The most seasonal tanks show wider extremes in seasonal nutrient dynamics, overall, with less favourable conditions than the ‘semi-seasonal’ tanks. Never the less all the tanks can be considered as being highly productive with NP levels comparable to fertilised pond systems for much of the year. This indicates that nutrient status is not likely to be amongst the most important constraints to enhancing fish production. Other potential management improvements based on these results are discussed. [PDF contains 19 pages]

Item Type: Monograph or Serial Issue
Title: Nutrient dynamics of seasonal tanks in the dry zone of Sri Lanka in relation to their hydrological regimes
Personal Creator/Author:
CreatorsEmail
Jayakody, B.V.P.L.
Murray, F.J.
Little, D.C.
Mowjood, M.I.M.
Date: 2002
Publisher: Institute of Aquaculture, University of Stirling
Place of Publication: Stirling, Scotland
Projects: DFID Aquaculture and Fish Genetics Programme (AFGRP)
Funders: Department for International Development, U.K.
Issuing Agency: Institute of Aquaculture, University of Stirling
Additional Information: nstitute of Aquaculture, University of Stirling; University of Peradeniya, Sri Lanka
Uncontrolled Keywords: Sri Lanka
Subjects: Aquaculture
Earth Sciences
Item ID: 2916
Depositing User: Ms. Jean Collins
Date Deposited: 19 Feb 2010 12:23
Last Modified: 29 Sep 2011 18:11
URI: http://aquaticcommons.org/id/eprint/2916

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