Final answer:
Strong thermoclines develop best during the 2. summer season when the heat from the sun causes the temperature of lake water to stratify, forming a stable thermocline with warm water on the surface and cooler water below.
Step-by-step explanation:
Strong thermoclines in shallow waters best develop during the 2. summer season. This occurs because the temperature of the lake water stratifies, creating distinct layers, with the warmest water positioned at the lake surface. During this time, a significant temperature difference establishes a thermocline, which is a layer of water with a temperature drastically different from that of the surrounding layers.
The summer stratification is a period where the effects of heat from the sun are most pronounced, leading to the development of a stable thermocline in lakes and other bodies of shallow water.
On the contrary, during winter, a layer of ice forms on the water surface, causing water below to retain a liquid form, where the aquatic life can survive on available resources. As spring arrives, temperatures increase and surface ice melts, leading to spring turnover.
By contrast, the fall turnover occurs when the temperature of the water cools to 4 °C, causing denser, oxygen-rich water to sink and displace water from the bottom, thereby circulating nutrients. However, it is the summer months when water layers become most pronounced and thermoclines are at their strongest.