Kia ora! I’m Irisa, an MSc student from the University of Auckland, and I recently had the incredible opportunity to serve as a BLAKE freshwater ambassador at NIWA Ruakura. Over two transformative weeks, I immersed myself in the world of aquatic pollution mitigation, contributing to a team dedicated to developing nature-based solutions for farm runoff and wastewater treatment. One of the most fascinating aspects of this experience was our innovative use of algae to mitigate excess nutrients in water bodies.
Coming from a terrestrial ecology background, my knowledge of algae was quite limited. However, my time at NIWA opened my eyes to the diverse and vital roles these ‘plant-like organisms’ play in freshwater ecosystems. Algae, ranging from unicellular diatoms with silica-based cell walls to multicellular macroalgae like seaweeds, are structurally distinct from land plants despite sharing the ability to photosynthesize. Among the most familiar algae are the Charophyta, known for forming colonial mats in streams and waterways.
After the weekly biomass data collection, the ponds are re-seeded with some of the collected algae. After spinning the retained water out of the algae, it turns a vibrant green and has a texture similar to a ridged candy floss.
Algae are ecological powerhouses, responsible for around 70% of the world’s oxygen production. They support food chains and are crucial in removing excess nutrients from waterways, which directly ties into our work at NIWA. New Zealand’s significant cattle population exerts a detrimental impact on freshwater environments, primarily through nutrient runoff from fertilizers and waste. This nutrient overload can lead to eutrophication, a process where excessive phosphorus causes algal blooms, depleting oxygen levels and harming aquatic life. Toxic cyanobacteria blooms resulting from eutrophication can also pose serious health risks to humans and animals, hindering customary food gathering practices and recreational activities.
To address these issues, our team developed the Filamentous Algae Nutrient Scrubbers (FANS). These systems are essentially large water troughs filled with untreated stream water and outfitted with mesh scaffolds where beneficial algae, such as Spirogyra, can grow. These algae mats capture excess phosphorus and nitrates, effectively cleaning the water. The harvested algae can then be repurposed as fertilizer, promoting a circular system that reduces the need for manufactured fertilizers and mitigates the environmental impact of farm runoff.
Filamentous Algae Scrubbers or FANS, this experimental set up is altering various conditions of each trough to investigate the suitability for large-scale projects.
During my time on the farm near Hamilton, I assisted in monitoring nutrient levels at various depths and lengths of the FANS. This hands-on experience was eye-opening, showcasing the potential of this nature-based solution. Although the FANS are still in the experimental phase, the progress from lab prototypes to a functional farm test site is promising. Scaling up the FANS and developing efficient algae harvesting methods, possibly through robotic ‘algae vacuums,’ will be crucial for making a significant impact on wastewater treatment.
My experience wasn’t limited to fieldwork. I spent considerable time in NIWA’s Ruakura labs, cultivating algae stocks and conducting experiments to optimize conditions for wastewater treatment. This involved working with bioreactors of various sizes, from small flasks to large troughs, and analyzing growth rates and nutrient absorption capacities. One of the most enjoyable lab activities was identifying different algae species under the microscope. The diversity and beauty of these organisms inspired me to illustrate them in watercolor, merging my scientific and artistic passions.
An illustration of various algae specimens found in only one milliliter of sample water from the FANS. The large chain represents Spirogyra, surrounded by smaller chains of Zygnema (star shaped chains) and some rigid diatoms.
Pediastrum algae colony. Illustrating these almost translucent organisms was a definite change from my usual botanical illustrations.
Pediastrum colony hiding behind filamentous algae.
An integral part of my ambassadorship was seeing the integration of mātauranga Māori with western science. Projects like using Harakeke fibers for water filtration and employing wetlands to treat wastewater in Raglan highlighted how indigenous knowledge and community partnerships can drive innovative environmental solutions.
This ambassadorship has been an inspiring journey, reinforcing the importance of nature-based solutions in addressing environmental challenges. It has deepened my understanding of freshwater ecology and environmental science in practice. I am immensely grateful to the NIWA algae team, BLAKE, and everyone involved for this amazing opportunity. My time at NIWA has filled me with hope for the future, knowing that sustainable and innovative solutions are within our reach.
