By Courtney Wigdahl, Friends of Acadia Aquatic Scientist
Our new sensor buoy (sonde) is actively taking measurements of a number of different water quality parameters at Jordan Pond. Here are the basics about what we are measuring, and why they are important to the overall water quality of Jordan Pond and other lakes around the world. Our sonde has individual probes for each of these readings, and collects readings from the probes every 15 minutes throughout the day.
Temperature: Water temperature is an important feature of lakes, as it influences a number of processes within lakes, including organism growth and reproduction, habitat availability for fish, and gas solubility. We measure temperature on the main sonde at about 0.5 meters deep, but we also measure the temperature profile of the lake with sensors placed every meter on a line hanging below the sonde to 16 meters deep. It is important to look at the temperature profile, because lakes in Maine often “stratify,” forming a warm water layer at the surface with a cold water layer below. During the summer, the upper warm layer does not mix with the colder deep water. The size and stability of the layers can change depending on air temperature, water clarity, and wind strength. These layers result in different vertical patterns of chemistry and habitat within the lake for algae, fish, and other organisms in the system.
Dissolved Oxygen: Many aquatic organisms require oxygen to survive and grow (like terrestrial animals and people), but they use oxygen that is dissolved in lake water rather than breathing in oxygen from the surrounding air. In particular, very low oxygen concentrations can result in large die-offs of fish, known as “fish kills.”
pH: pH is a measure of whether a solution is acidic or basic. Measured on a scale from 0 to 14, lower pH (less than 7) indicates an acidic solution, whereas higher pH (greater than 7) indicates a basic solution. For example, stomach acid has a pH of around 1 and household bleach has a pH of around 12.5. Pure water has a neutral pH of 7, though the pH of water in natural systems can range widely. Historically, Jordan Pond has been just below neutral, with pH readings between 6 and 7.
Conductivity: Conductivity is the measure of water’s ability to carry an electric current, generally through the quantity of charged particles (ions) present in the water. These particles include dissolved substances that have both positive (e.g. calcium, magnesium, sodium) and negative (e.g. sulfate, nitrate, phosphate) charges. The amount and types of ions in lakes depends on a number of factors, including local geology, atmospheric inputs, evaporation, and pollution inputs. Major changes in conductivity can alter what types of organisms live in a lake, as well as possibly signal changes in materials coming into the system.
Organic Matter: Organic matter in lakes comes from a number of sources which often include leaf litter, soils, and decaying materials washing into the lake from the surrounding landscape. Organic matter can also be produced within the lake itself by algae, plants, bacteria, and larger organisms. Like tea leaves steeping in water, organic materials can give water a brownish color. This tea-stained color can change water clarity, absorption of heat, and water chemistry (such as pH or nutrients). In recent decades, many lakes in North America have had increases in organic matter, and aquatic scientists are currently working to better understand the causes of these changes.
Chlorophyll: Chlorophyll is the primary pigment that algae (and other plants) use to perform photosynthesis—a process that takes energy from the sun to convert carbon dioxide into sugars that algae use to live and grow. We can use the amount of chlorophyll present in the water as a measure of how much algae growth is occurring within the lake. Algae form the base of the food web in aquatic ecosystems, providing food for other organisms living in the system. In some cases, certain types of algae can grow very rapidly into large “blooms,” resulting in reduced water quality and even issues with oxygen availability for fish communities. These types of blooms are common in some Maine lakes, but rarely occur in Jordan Pond.
Courtney Wigdahl is the 2013 Friends of Acadia Aquatic Scientist leading the water quality monitoring efforts at Jordan Pond. Her position was made possible through a generous grant from Canon U.S.A.