Research Article Dynamics of Dissolved Oxygen in relation to Saturation and Health of an Aquatic Body: A Case for Chilka Lagoon, India B. S. R. V. Prasad, 1 P. D. N. Srinivasu, 2 P. Sarada Varma, 3 A. V. Raman, 4 and Santanu Ray 5 1 Fluid Dynamics Division, School of Advanced Sciences, VIT University, Vellore 632014, India 2 Department of Mathematics, Andhra University, Visakhapatnam 530003, India 3 Department of Basic Science & Humanities, GMR Institute of Technology, Rajam, Srikakulam 532127, India 4 Marine Biological Laboratory, Department of Zoology, Andhra University, Visakhapatnam 530003, India 5 Ecological Modelling Laboratory, Department of Zoology, Visva-Bharati University, Santiniketan 731235, India Correspondence should be addressed to B. S. R. V. Prasad; srvprasad.bh@gmail.com Received 13 March 2013; Revised 4 December 2013; Accepted 5 December 2013; Published 20 February 2014 Academic Editor: Wen-Cheng Liu Copyright © 2014 B. S. R. V. Prasad et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Dissolved oxygen (DO) is essential for an aquatic ecosystem since it controls the biological productivity. Here, we propose a unidimensional dynamic model for DO by incorporating biological (photosynthesis, respiration, and mineralization), physical (atmospheric reaeration) and chemical (nitriication) processes so characteristic of shallow coastal water bodies. he analytical study of the proposed model is focussed on supersaturation and undersaturation of oxygen in the water body. he controllability of the ecosystem health has also been investigated. Model results indicate that, while undersaturation of oxygen is largely governed by nitriication and Net Ecosystem Metabolism (NEM), the supersaturation is controlled by photosynthetic activity. he model results are corroborated with observed data collected from Chilka lagoon, India. Subsequently, a biogeochemical model to study the DO variations in Chilka lagoon has been constructed. he model is properly calibrated and validated with observed data. Two independent sets of data (2004-2005 and 2005-2006) were used for model calibration and validation and Chi-square tests supported its robustness ( 2 = 0.982 and 0.987;  < 0.05). he model was used to evaluate independently the inluence of individual taxa (diatoms, microphytobenthos, and cyanophyceans) on DO variations. Simulations indicate the vital role of microphytobenthos in lagoon DO dynamics and the overall wellbeing. 1. Introduction Dissolved oxygen (DO) is an essential component which determines the water quality and trophodynamics of an aquatic system [1–3]. A luctuation of DO near its saturation indicates relatively healthy waters [4]. In a healthy aquatic lagoon ecosystem the concentration of oxygen must always be above the chronic criterion for growth (4.8 mg L −1 ) devel- oped by the U.S. EPA [5, 6]. A fall of oxygen below this chronic criterion can cause adverse efects on the health of the aquatic system. he system can sufer with hypoxia/anoxia conditions, resulting in depletion of ish stocks and other important aquatic animals [7, 8]. hese losses can have signiicant damaging efects on ecological health, economic health, and stability of aquatic systems [8, 9]. DO dynamics are complex in nature and are afected by many physical, chemical, and biological processes. he important factors that afect DO dynamics in an aquatic environment are atmosphere-water surface exchange, pho- tosynthesis, respiration, and mineralisation [5, 10, 11]. he other processes that afect the oxygen dynamics in the water column include nitriication, sediment-water exchange. he availability of the oxygen in the water column also depends on topography of the system, the nature of the soil, and so forth ([4] and references there in). Many experimental studies are carried out to study the conditions that are responsible for hypoxia/anoxia in costal ecosystems [3, 12–14]. hese studies pointed out that factors such as excess of nutrient load (eutrophic condition) and nitriication are the primary reasons for the hypoxic/anoxic Hindawi Publishing Corporation Journal of Ecosystems Volume 2014, Article ID 526245, 17 pages http://dx.doi.org/10.1155/2014/526245