Dr. Soudeh Afsharian's scientific lecture with the tile of "Modeling the Impact of Climate Change on Algal Blooms" was held. In this lecture that was delivered through a webinar on July 27, valuable topics related to the impact of climate change on algal blooms were discussed which are as follows:
A potentially harmful algal bloom often grows to cover a wide area of Lake Erie - located between Canada and United States - (for instance, on October 4, 2017, more than 1812 km2 was covered), turning the lake bright green and alarming residents and local officials. Scientists say that algae blooms have been growing problem for Lake Erie since the 2000s, mostly because of the extensive use of fertilizer on the region’s farmland. The algae blooms can produce toxins that contaminate drinking water, cause harm to the local ecosystem and can cause serious liver damage to humans under certain conditions. Millions of people get drinking water from Lake Erie. On the other hand, Lake Erie attracts millions of visitors for beaches and recreation like fishing, and many businesses stand to lose money during large algae blooms.
An increase in water temperature (within the normal range) will increase the growth of algae. Warmer upper layer temperature prevents water from mixing, allowing algae to grow thicker and faster. Warmer water is easier for small organisms to move through and allows algae to float to the surface faster. Algal blooms absorb sunlight, making water even warmer and prompting more blooms. Also, warmer temperature increases the rate of respiration and this fact associated with the thicker thermocline (a layer of water where the temperature gradient is greater than that of the warmer layer above and the colder layer below – a boundary between epilimnion and metalimnion), causes oxygen depletion. In a stable body of water with no stratification, dissolved oxygen (DO) will remain at 100% air saturation. As stratifications develop, DO falls below 100%. At strong thermocline situation, DO reaches to its minimum value, particularly in deeper waters, due to respiration of aquatic organisms and microbial decomposition. Therefore, some baitfish cannot survive below the thermocline. This has dramatic effects on all the species of fish.
To investigate the effect of Climate Change on the Great Lakes the researches at York University applied COHERENS in order to simulate and investigate the impact of the Climate Change on the Great Lakes’ thermal structure and hydrodynamics as well as study the impact on the algal bloom growth. The physical state of the lakes can be accurately represented through fields of a few variables (current, temperature, etc.). The marine biological system is in principle much more elaborate, for its living part consists of many discrete individuals belonging to a number of species. In addition are nonliving populations of particles of several sizes and a variety of dissolved substances. Our simulation provides scientific guidance on issues related to the Climate Change policy for the Great Lakes.