NUTRIENT CYCLING DYNAMICS OF AN ALGAE-OYSTER SYSTEM

Matthew D. Campbell* and Steven G. Hall
 
Biological and Agricultural Engineering Department
North Carolina State University
3100 Faucette Drive
Raleigh, NC 27695
mdcampb2@ncsu.edu
 

There has been some disparity in the literature regarding oysters and their impact on the surrounding environment. Studies on oyster reefs and farms have shown both positive and negative variability in the net nutrient amounts surrounding these features.  Intuitively, the presence of oysters and their ability to filter seston from the water column would imply an overall reduction in nutrients of a given system. Consequently, some of these studies actually show overall increases of nutrients in the lee of oyster features.  On the other hand, the use of oysters to mitigate estuarine eutrophication and/or reduce nutrients in agriculture and aquaculture waste effluents has recently been proposed in various forms and experienced positive results.

Although previous studies have explored the nutrient recycling of oysters in specific systems or environments, a quantitative model to understand the dynamics of the more comprehensive algae-oyster system is lacking.  A first step in the development of a comprehensive dynamic model is to understand the complex interactions of the algae-oyster nutrient recycling pathways. This is accomplished through the development of a mass balance that incorporates growth dynamics of algae, filtration of oysters, assimilation into biomass, excretion components, and degradation of fecal pellets. Various environmental parameters, such as temperature, light, nutrient concentrations, hydrodynamics, salinity, and turbidity are also incorporated into the model. Experimental data is utilized to validate assumptions within the mass balance model.

This presentation describes the algae-oyster dynamics using a mass balance model in order to investigate the ability of a small or landscape scale system to reduce dissolved nutrients within a water column under various conditions. The results of this work can be implemented into larger scale modeling efforts and has implications on sustainable management of oyster mariculture, management of eutrophic estuarine systems through oyster cultivation, and treatment of aquaculture effluents using an algae-oyster culture system.