6.0 Summary of findings
6.1 Objective One: Mesocosm Enrichment Experiment
The purpose of the mesocosm experiment was to determine how nutrient conditions influence the growth of cyanobacteria in Napoleon Gulf in Lake Victoria, Uganda. Through interpretation of the chl-a (RFU) and chl-a (ug/L) values between N (Urea, and NO3) treatments and N + P (Urea + P and NO3 + P ) treatments it was determined that the Napoleon Gulf was most likely N-limited not P-limited. The results showed the chl-a RFU and nutrient concentration responses followed the predicted growth/depletion trends. The chl-a concentrations for Urea and Urea + P treatments showed the predicted growth trend. Further analysis is to be completed to determine species succession and toxin profiles. These results can determine if variation of N-sources within the Napoleon Gulf impacts phytoplankton succession, favouring cyanobacteria and more specifically the toxin producing Microcystis. Understanding how readily used fertilizers, such as Urea, promote potentially harmful algal blooms in the Napoleon Gulf can lead to the proper management of agricultural application within the basin. Building the data base on the tropical Great Lakes will improve how these lakes are management and protected from the exceedance of planetary boundaries.
6.2 Objective Two: Observation Community Visits
The purpose of the community visits were to gather observational data that was culturally and environmentally appropriate to pair with the mesocosm experiment. If the experimental data is used for policy development, it is critical that it reflects and protects the most vulnerable communities within the Napoleon Gulf. Through the identification of the exposure routes, the direct and indirect health risks were assessed. Direct health impacts were associated with the consumption of and physical exposure to toxins. This can cause a variety illness depending on the toxin present, toxin dosage, acute or chronic exposure, and the individual (age, pre-exiting health, etc.). The hepatotoxin microcystin is predicted to be present within the Napoleon Gulf, which has serious human and animal health implications.
The indirect health impacts relate to the negative impact of loss of livelihood and environmental degradation caused by harmful algal blooms (HABs). HABs can lead to large fish kills and poisoning of livestock. These communities rely on fish for their income as well as a food source, and can only afford limited livestock (food and income). Paired with the local loss of fishing practices, Victoria Lake as a whole, produces 1 million tons/year of fish production and significantly adds to the global markets.
6.3 Overall
Therefore, completing the planetary health case study on “harmful algal blooms on Lake Victoria and associated risks to fishing communities required a system-thinking approach. The purpose was to understand the linkages between nutrient addition into the lake, HAB development, potential exposure to HABs, and associated health risks in the Napoleon Gulf. The case study included the experiment paired with the community engagement to ensure the research produced was not solely for “scientific purposes” but used to tackle this planetary health issue. The results of the species succession and toxin profiles from the mesocosm experiment will tie together the experiment to the risk assessment during the community engagement. The findings from this case study (nutrient conditions and health risks) adds pressure to political bodies for the development of culturally-environmentally inclusive polices related to the protection of the Napoleon Gulf. This case study provides an example for future case studies and begins to bridge the gap between “science” and “community work” and highlights the importance of community-based participatory research.