|
|
|
Wearin’ o’ the Green By Geoff Peach, The Lake Huron Centre for Coastal Conservation One of the things we least like when we go for a swim in the lake is coming out with green slime clinging to our hair. Algae is a regular occurrence on the Great Lakes. Too much algae on our beaches and nearshore waters, though, usually indicates a problem with the local ecology. In honour of St. Patrick’s Day, we naturally thought of green algae as a Lake Huron related topic. Cladophora is a naturally occurring algae on the Great Lakes which provide shelter and nourishment to a wide variety of organisms including molluscs, diatoms and young crayfish. As with most plants, the addition of nutrients like phosphorous and nitrogen can accelerate growth rate of algae, and this can be a problem when the natural balance goes out of control. Concerns of nutrient enrichment and algal growth in the Great Lakes have been high for the past three decades. Between 1978 and 1981, the Ministry of Environment did a study of the growth of the algae “Cladophora” in the nearshore waters of Lake Huron to gain a better understanding of the sensitivity of Lake Huron to Cladophora in the presence of phosphorous inputs. The investigation focused on Goderich, south of the Maitland River mouth, and the Bruce Nuclear Power Development (BNPD) area, including Inverhuron. Another study area included the nearshore waters of southern Georgian Bay (Nottawasaga Bay). Much of the area was characterized by the presence of a rocky lakebed. Cladophora grows clinging to rocks. Studies have roughly estimated that over 70% of the nearshore area (to a depth of about 10 metres) of Lake Huron, from Sarnia to Tobermory, provides a suitable, rocky base for Cladophora growth. While this algae clings to rocks, it occasionally gets sloughed off and gets carried to shore by waves. As an example, in 1978, sloughed Cladophora fouled approximately 10 kilometers of Lake Huron shoreline in the vicinity of Goderich. More recently, the Town of Goderich was faced with removing truck loads of algae from its beaches. In 2001 and 2002 in particular, the Town would routinely remove 4 to 6 gravel truck loads of algae 2 to 3 days a week for the entire summer period (June to September). Prior to 2001, algae on the beach had been a modest problem with removal of light amounts once per month or once every two weeks. The problem with algae amounts of this magnitude is the powerful smell – not a pleasant experience for the average beach-goer. Large amounts of algae are usually indicative of excessive nutrients like nitrogen and phosphorous entering the water from runoff. Algae fouling along our beaches is an obvious example of an ecological imbalance due to excessive nutrients in the water. What are the sources of these nutrients? The usual suspects…faulty septic systems, agricultural runoff, periodic municipal sewage overflows, and waterfowl. Nutrients are part of the concern. The other is that scientists have identified an association between the mats of algae that we see washed up on our beaches and high levels of the bacteria E. coli. The algae may actually promote the growth of E. coli. These decaying mats of algae likely provide increased levels of nutrients, decrease the amount of ultraviolet radiation from the sun that tends to kill the bacteria, and likely provide a warmer, more moisture-stable environment than a sand or rock beach environment. Scientists are looking more closely into the algae problem to help shed some insight into how this issue can be better managed so that we can reduce this problem to local beaches. In the end, it will be up to everyone to participate in the active stewardship of our lake. Tips to reduce nutrients entering our lake: - Maintain your septic system. This will help keep excessive nutrients from leaching from your tile bed into the lake. For more information on algae, contact the Lake Huron Centre for Coastal Conservation at (519) 523-4478, or email coastalcentre@lakehuron.on.ca. |
|