All around us plants are breathing! In land, air and water plants are taking in carbon dioxide and releasing oxygen in a process called photosynthesis.
This process is usually invisible. Using the HRECOS real-time data, however, anyone can observe plant breath in the Hudson River water.
The plants found in the Hudson River include phytoplankton and macrophytes. Phytoplankton are floating plants too small to be seen with the naked eye. Macrophytes are visible with the naked eye and can be found growing in shallow waters. Both phytoplankton and macrophytes grow to large populations and have a significant impact on the chemistry and ecology of the Hudson River.
When dawn breaks, phytoplankton and macrophytes begin photosynthesis. They breathe in carbon dioxide and they exhale oxygen. Carbon dioxide is a precursor for carbonic acid so when it is removed, the water's pH increases. As a result, oxygen concentrations and pH increase throughout the morning.
As the light fades, the plants stop photosynthesizing. Oxygen is inhaled and carbon dioxide is exhaled by plants and animals respiring. Thus, in the evening, oxygen concentrations and pH decrease (as a result of the increase of carbon dioxide). Lowest concentrations can be measured just before dawn.
The end result is visible breathing. A daily cycle of rising and falling oxygen concentrations and acidity. These can be seen any time of year but they are most dramatic in the spring and summer when the sun's radiation is strongest.
There are many factors influencing rates of photosynthesis, dissolved oxygen concentrations, and acidity in the Hudson River. Because of this, you will often see variations in the pattern described above. For example, cloudy days will block the sun's radiation resulting in lower rates of photosynthesis. Alternatively, midday low tides will allow sunlight to reach more plant material and increase photosynthetic productivity.
To observe and explore the breathing patterns of the Hudson River aquatic plants, view the real-time HRECOS data by clicking on "Current Conditions" in the main menu.