Nova Scotia’s Lakes: Life Under the Ice
by Val Kendall
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Animal footprints dance across a very frozen Nancy Lake, Nova Scotia. Photo by Amanda Lavers. |
Winter in the Maritimes: Cold and wet. Snow and ice. Deciduous trees lose their leaves, songbirds migrate, and fish no longer jump to the surface of lakes. The same lakes we were swimming in just a few months ago become platforms of ice. Under this ice however, life is still beating in anticipation of the warm, revitalizing months to come.
Temperature has a remarkable effect on lakes and- in turn- the plants and animals living there. During warmer months, sunlight and oxygen penetrate the top layer of lakes. The sun warms the water and plants grow in the light, which adds more oxygen to the system. Because warm water is less dense, it floats on top of colder bottom water. Where the warm and cold water layers meet is known as the thermocline.
As winter approaches, the top layer of lake water begins to cool and sink, bringing along abundant oxygen to the bottom. Once ice covers the lake, oxygen and sunlight can no longer penetrate. Plants stop growing and aquatic animals must adjust their metabolism to survive on the oxygen already dissolved in the water. Frogs survive by hibernating in the muddy bottoms, breathing only through their skin, while many insects and microorganisms build shells around themselves, remaining dormant until spring.
Other creatures such as lake trout stay below the thermocline- coming up only to feed in the warmer seasons. These hardy fish are relatively unaffected by the colder temperatures- but, they are challenged by decreasing prey and oxygen as the winter wears on. Aquatic mammals like beavers and otters that hunt under the ice have insulating fur and specially adapted circulatory systems that maintain constant body temperatures in the frigid water.
Climate research suggests that Nova Scotia (along with much of North America) is experiencing serious climactic changes. This has included a trend of shorter winters, and less ice coverage on lakes and ponds.
While a number of factors influence our planet’s climate, human activities, chiefly related to burning fossil fuels, are altering the composition of our atmosphere, adding carbon dioxide and other gases and causing an accelerated trend of warming. In Nova Scotia, climate change is expected to warm lakes and reduce available dissolved oxygen. This may have serious implications for these systems. Indeed, sensitive species like the lake trout are in danger of losing their habitat altogether.
To combat the effects of climate change, we all need to take responsibility for our actions. Choosing CFC light bulbs, energy efficient appliances and home heating systems can make a real difference, along with using sustainable, active transportation. Taking part in community and workplace initiatives to reduce carbon emissions can also help us all achieve better understanding of environmental changes and protect our precious freshwater ecosystems.
Val Kendall is a volunteer with the Coastal Issues Committee who describes herself as an “environmental enthusiast”. Coastlines is coordinated by the Coastal Issues Committee at Ecology Action Centre and supported by the Nova Scotia Habitat Conservation Fund with contributions from hunters and trappers.
Coastal Issues Committee
Phone: (902) 442-5046
Fax: (902) 405-3716
How do you like your coast? Take action on coastal issues that matter to you. The Coastal Issues Committee meets at the EAC on the last Thursday of every month at 5:30PM.
