de Paula Silva, Pedro H., De Nys, Rocky, and Paul, Nicholas A. (2012) Seasonal growth dynamics and resilience of the green tide alga Cladophora coelothrix in high-nutrient tropical aquaculture. Aquaculture Environment Interactions , 2 (3). pp. 253-266.

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Abstract

Two distinct climatic seasons in the tropics generate extreme environmental fluctuations in land-based aquaculture and corresponding challenges for integrated aquaculture. Here we assessed the influence of environmental and culture variables on productivity of Cladophora coelothrix at multiple scales, firstly in an operational settlement pond and subsequently in laboratory and flow-through mesocosm experiments. Classification and regression tree (CART) analyses were used to partition the influence of key variables on growth. In situ productivity correlated primarily with nitrogen concentration, position in the pond and stocking density, with a lesser influence of salinity, temperature and the ratio of nitrate-nitrogen (NO₃⁻-N) and total ammonium nitrogen (TAN). We subsequently evaluated the resilience of C. coelothrix in laboratory and mesocosm environments by manipulating salinity, temperature and nutrients across a broader range of values derived from a year-long survey of the settlement pond. Here temperature had the greatest influence on growth, followed by nitrogen concentration and salinity. Growth rates of C. coelothrix were high, irrespective of season, except at the extremes of each season, for example, at the lowest annual temperature and with the combination of high temperature and low salinity. Growth was also limited by ~20% when NO₃⁻-N and TAN were available simultaneously. The use of CART analyses for both in situ and controlled environment data provided a formal dissection of the relative contribution of each environmental variable to growth, demonstrating the year-round potential for bioremediation and identifying the critical combinations of environmental variables for management of this system.

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