Does anyone know how the aquatic chemistry of a tropical lake would differ from that of one in the usa or uk?

They have different temperatures so rates of reactions in a tropical lake would be faster. Furthermore, water is most dense at 4 deg C, so at colder temperatures in UK and US which sometimes reaches this temperature during spring or fall, water tends to cycle from top to bottom. Hence, Oxygen will be brought down to lower levels of the lake. It has been observed that more life is found in the bottom of temperate lakes in comparison to tropical lakes because of this.