Green tide algae integrated aquaculture for nitrogen bioremediation

de Paula Silva, Pedro Henrique (2012) Green tide algae integrated aquaculture for nitrogen bioremediation. PhD thesis, James Cook University.

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Green tide algae bloom in eutrophic environments with fast growth rates, efficient nutrient uptake and broad environmental resilience. These same characteristics are sought after for algae in integrated aquaculture systems. To evaluate the potential use of naturally occurring green tide algae in tropical integrated aquaculture the effects of key variables on resilience, biomass productivity and bioremediation potential were quantified. Three locally abundant green tide algal species (Cladophora coelothrix, Chaetomorpha indica and Ulva sp.) demonstrated a high tolerance across the extremes of salinity (15 to 45‰) and total ammonia nitrogen (TAN from 7 up to 700 μmols l⁻¹) characteristic of tropical aquaculture bioremediation ponds. In a preliminary in situ experiment Cladophora coelothrix demonstrated high growth and survival rates, a high predicted productivity (4 t ha⁻¹ for a 7-day harvest cycles) and corresponding nitrogen removal (23 kg N harvest⁻¹). Subsequently, it was determined that large scale, in situ productivity of Cladophora coelothrix during four winter months 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 and total ammonium nitrogen. Growth and resilience were then determined in factorial laboratory and mesocosm experiments, according to environmental fluctuations of an entire growing season. Cladophora coelothrix growth was high irrespective of seasonal fluctuations. Temperature was the key variable for seasonal growth, followed by nitrogen concentration and salinity, and interestingly growth was limited by ~20% when nitrate-N and TAN were available simultaneously. In addition to adequate nitrogen levels, seaweeds under intensive culture require a high flux of dissolved inorganic carbon (Ci) to support productivity. In this study, higher levels of inorganic carbon (Ci), in particular CO₂ significantly enhanced the productivity of Cladophora coelothrix (26%), Chaetomorpha linum (24%) and Cladophora patentiramea (11%), despite the demonstrated HCO₃⁻ utilization through high pH compensation points (9.7-9.9) and growth in pH levels up to 9. Finally, classification and regression tree (CART) analysis in combination with logistic equations, using relevant laboratory, mesocosm and field data from all previous data chapters, were used to develop annual model simulations for large-scale algal culture for two locally abundant green tide algae. The logistic model simulations demonstrate that Cladophora coelothrix had a high environmental tolerance and the highest predicted annual productivity of 24.3 T dry weight ha⁻¹ year⁻¹, equating to a nitrogen removal of 140 kg ha⁻¹year⁻¹, whereas the lower environmental tolerance and overall growth of Cladophora patentiramea resulted in a lower annual productivity of 10.8 T dry weight ha⁻¹ year⁻¹. In conclusion, this study has demonstrated that green tide algae can be cultured in tropical land based ponds with high productivity and nitrogen bioremediation. Cladophora coelothrix, in particular, demonstrated a broad environmental tolerance, high biomass productivity and nitrogen bioremediation, and these results support the use of this green tide algal species in integrated aquaculture.

Item ID: 33639
Item Type: Thesis (PhD)
Keywords: algal blooms; aquaculture effluent; bioremediation; carbon; eutrophication; green tide algae; nitrogen; predictive models
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Publications arising from this thesis are available from the Related URLs field. The publications are:

Chapter 2: de Paula Silva, Pedro H., McBride, S., de Nys, Rocky, and Paul, Nicholas (2008) Integrating filamentous 'green tide' algae into tropical pond-based aquaculture. Aquaculture, 284 (1-4). pp. 74-80.

Chapter 3: 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.

Chapter 4: de Paula Silva, Pedro H., Paul, Nicholas A., de Nys, Rocky, and Mata, Leonardo (2013) Enhanced production of green tide algal biomass through additional carbon supply. PLoS ONE, 8 (12). pp. 1-7.

Date Deposited: 30 Jul 2014 23:58
FoR Codes: 07 AGRICULTURAL AND VETERINARY SCIENCES > 0704 Fisheries Sciences > 070401 Aquaculture @ 100%
SEO Codes: 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8301 Fisheries - Aquaculture > 830199 Fisheries - Aquaculture not elsewhere classified @ 50%
83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8398 Environmentally Sustainable Animal Production > 839899 Environmentally Sustainable Animal Production not elsewhere classified @ 50%
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