Temperature is important for growth in any ecosystem. Oxygen gas is less soluble in water at higher temperatures than at lower temperatures, which means that the level of dissolved oxygen in warm water will usually be lower than the amount in colder waters. An easy way to remember this is that warm water will 'bubble the oxygen out' quickly, while cold water will 'hold onto oxygen for a longer time'. An increase in water temperature can encourage biological and chemical activity, usually decreasing the amount of dissolved oxygen in the system.
Larger lake or ocean systems show characteristic temperature patterns as the seasons change: during spring, temperature patterns, water density, and the level of dissolved oxygen within a lake are fairly consistent. As summer approaches, the sun heats the system, causing internal changes. The less dense top layers of the water warm first, and stay at the surface. Thus, two distinct layers form: a warmer, upper layer and a cooler, lower layer. This layering is called thermal stratification. By midsummer there will be three layers: the warm upper layer, a transition layer from warm to cold called the thermocline, and the cool deeper layer.
This layering has consequences for dissolved oxygen levels. The warmer upper layer at the surface circulates, thus maintaining contact with the air, whereas, the deeper, cooler layer is cut off from the surface by the thermocline. This reduces oxygen in deeper waters, and limits productivity in this layer
This layering has consequences for dissolved oxygen levels. The warmer upper layer at the surface circulates, thus maintaining contact with the air, whereas, the deeper, cooler layer is cut off from the surface by the thermocline. This reduces oxygen in deeper waters, and limits productivity in this layer
Students watch as they are shown how to use the equipment for measuring the water temperature of the Bay of Islands. Students from the various communities participate in collecting the data used to measure the water quality.
When winter arrives, the water cools. The layering disappears and temperatures become uniform again. As air temperatures continue to fall, the surface waters of the lake cool further, become denser and sink to the bottom. This pattern continues until the water temperature reaches 4°C, the temperature of maximum density for water. Water colder than 4°C is lighter, remains near the surface, and freezes, forming ice at the surface, while the temperature remains 4°C at depth.
While plants are adapted to these temperature variations, many animals prefer more stable temperatures and generally move to stay within a certain range. These temperature preferences are critical for feeding, reproduction, and migration. In particular, temperatures are critical for the survival of young.
While plants are adapted to these temperature variations, many animals prefer more stable temperatures and generally move to stay within a certain range. These temperature preferences are critical for feeding, reproduction, and migration. In particular, temperatures are critical for the survival of young.
The graph to the left shows the temperature measurements from 10 Bay of Islands sites in the years 2005 & 2006.
The data used to generate the graph was collected in the Fall season of 2005 & 2006.
A copy of the Microsoft Excel spreadsheet containing the data used to generate the graph may be downloaded here.
The data used to generate the graph was collected in the Fall season of 2005 & 2006.
A copy of the Microsoft Excel spreadsheet containing the data used to generate the graph may be downloaded here.
Environmental Education - Science & Research - Community Engagement
Initiative Supported By
ACAP Humber Arm Environmental Association Inc.
P.O. Box 564, Corner Brook, NL, Canada, A2H 6E6
P.O. Box 564, Corner Brook, NL, Canada, A2H 6E6