Dissolved oxygen variations in marine fish culture zone

Abstract

Extensive field measurements aimed at studying short-term dissolved oxygen (DO) variability have been carried out in a marine fish culture zone in Hong Kong. A dynamic oxygen budget model is developed to analyze the diurnal water-quality data from a series of 26-hr surveys. The model formulation includes phytoplankton dynamics and photosynthetic production, sediment oxygen demand (SOD), fish respiration, carbonaceous and nitrogenous oxidation, and atmospheric oxygen transfer. The model is used to determine the components of oxygen consumption and production-in particular, the SOD and carbon-to-chlorophyll (CCHL) ratio. It is found that SOD and algal respiration are major oxygen consumption items, and the CCHL ratio is much higher than reported in previous mathematical model studies. Simulations of the diurnal DO variation are compared with data over a wide range of meteorological and ecological conditions. The model interpretation provides a basis for the formulation of a water-quality model for short-term DO forecasts.