I'm not sure if the City workers you spoke with were speaking out of ignorance or politics or both but heat was not the root cause of this fish kill. Do you really believe aquatic ecosystems loose all there oxygen when it's really hot for a couple weeks? if this were true why aren't there fish kills in every freshwater body in the city, county or state? Heat waves are a natural occurnace and healthy aquatic ecosyytems survive them every day.
The culprit is nutrient imput. Next time you drive through Glenn Meade or hitting the back nine at Cape Fear Country Club's golf course (all directly drain into the GF Lake watershed) think about how many pounds of nitrogen, phosphorus and other fertilizing nutrients are added to that beautifaul green grass every year (especially the summer). Now add all that dog and duck poop (though a much smaller and more natural nutrient input). Nutients spike + Sunshine = algal blooms in GF lake. When the algae blooms all at once in the lake, guess what happens later... it all dies at once. The decay of the massive algal bloom in the Lake depleated the dissolved oxygen causing the fish kill. The heat wave was probably a catlyst but not the root cause. Nutrients are the cause.
If you want to understand fish kills don't interview the Parks and Rec Dept. Interview the Aqutic Ecology Laboratory at UNCW-CMS. They have done MANY studies on this topic including on GF Lake.
More information about formatting options