Probes
Dissolved Oxygen
Dissolved Oxygen (DO) is crucial because the initial DO is used to calculate biochemical oxygen demand (BOD), which is the amount of oxygen available in a body of water for organisms to consume.
DO is measured by collecting ten random samples and then sticking a Vernier optical DO probe into a capped, oxygen-free flask. The DO value is then recorded. The probe is washed off with distilled water to repeat the process with the remaining samples. DO readings are usually anywhere between 90mg/l and 100mg/l.
The DO of a river can be affected by a multitude of factors. These include phosphates, temperature, flow rate, and turbidity. More phosphates in a river can cause algal blooms, which initially creates oxygen in the river. But as the algae die and bacteria break down the dead plant material, the oxygen is quickly used up, and thus the amount of oxygen left in the water is greatly diminished. Temperature also affects the amount of oxygen in the water because warm water holds less oxygen. The molecules in warmer water are more active than in cooler water, which means the oxygen molecules can more easily escape. Turbidity affects DO because cloudy water absorbs more sunlight, thus the water is warmer. Finally, Flow rate affects DO because a higher flow rate allows for more oxygen to enter the water.
Temperature
Heat transfer, coming from either the air, sunlight, or thermal pollution can change the temperature of the water. Considered alone, the water temperature can affect the metabolic rates and biological activity of aquatic organisms. There aren’t any specific advantages or disadvantages to having a warm or cold water system because they both have their positives and negatives depending on the organism. Different aquatic organisms have distinct preferred ranges of temperatures in which they can live, thrive, and reproduce. Due to temperature variance throughout the year, even with multiple rivers, we have considered removing this variable from our everyday testing. Even though it varies regularly, it is important for finding rivers with similar conditions to the JRSM habitat where we could possibly introduce the spinymussel.
Water temperature is an important factor to consider when assessing water quality and the health of a river. Temperature influences several other parts of life in a body of water and can alter the physical and chemical properties of this water. Variables like turbidity, benthic, and dissolved oxygen have been discussed on the other variable sites.
Conductivity
Conductivity is a measure of water’s ability to pass an electric flow. This measure is indicative of the abundance of ions in the water. The erosion of minerals from soil, rain, and snow from the atmosphere and runoff can increase conductivity. These conductive ions come from dissolved salts and inorganic materials such as chlorides, alkalis, carbonate compounds, and sulfides. In our tests, conductivity was measured in siemens per centimeter (uS/cm).
In environmental sciences, the conductivity of water is directly proportional to the salinity, which is a measure of sodium chloride ions. Therefore, we can predict the salinity of a river based on the conductivity of said river. This was important because organisms often adapt to survive in certain salinities and not in others, so salinity measures can help us predict the benthic composition of the surrounding area. Although no studies have been done on the James River Spinymussel specifically in regards to salinity, research on other species has shown that in mussels, salinity can affect the growth rate, reflected as “reduced shell growth rate and decreasing weight-specific growth.” Because salinity can potentially have such a large effect on mussels, perhaps salinity should be a variable we test more vigorously in the future.
Flow Rate
The flow rate of a river is the volume of water traveling through a river at any given time. The flow rate of a river can fluctuate depending on the time of year, the weather and the environment surrounding the river. As the seasons change, the amount of rainfall varies. For example, there is more rainfall in the spring than in the summer which affects the amount of water in the rivers. When there is more water in the creeks, rivers, and streams, the flow rate will increase. Along with the dependence on seasonal change, a river’s flow rate is affected by the region. States with the most rainfall happen to be mostly isolated in the southeast as 9 of the top eleven states (Rain/Snowfall totals) are from the southeast. The final major determinant of flow rate is the size of the river. Rivers that are both wide and deep are able to withstand small disturbances such as mountain runoff and small storms as the amount of water originally in the river is very high. On the other hand, creeks and streams can be extremely affected by the smallest of storms. Flow Rate can determine the organisms that are able to survive these changes in conditions. Flow Rate is an important measurement to take when testing a river because its effects on the river’s ecosystem are drastic.
The flow rate of the river is measured using a Vernier Flow rate Sensor. The sensor is placed at a 90-degree angle at the bottom of the river at each of the six sites where water was collected and a reading of the river velocity is recorded.
Turbidity
Turbidity is the measure of suspended particles within a liquid, or its clarity. Urban development and rainy weather wash sediment into the water system increasing the turbidity levels in the river. Eroding river banks can also cause wash deposits into the mussel's habitat. Particles found in river water can include algae, clay, plankton, and silt; all of these do not allow light to shine through the water. This can lead to a reduction in the photosynthesis of plants found beneath the water’s surface. The suspended particles also absorb light, causing the temperature to rise and the dissolved oxygen to lower. High turbidity can also cause health issues for the fauna that live in, and near the river. Animals that filter water can be negatively affected by high turbidity if their gills are clogged by larger particles. When turbidity is at a high level it can also cause the eggs and larvae of aquatic animals to become smothered and die.
By using a Vernier probe we are able to record how much light is able to pass through the water, producing a reading in nephelometric turbidity units (NTU). Before each field session, the turbidity probe was calibrated using 1 NTU and 100 NTU samples on site.
Biochemical Oxygen Demand
We use Biological Oxygen Demand (BOD) to measure bacteria and microorganisms present in the water but unable to be seen by the human eye. A balanced BOD is essential to the health of a river. A higher BOD can be positive for the James River spinymussel because there are more microorganisms for the mussel to feed on, such as plankton. However, a higher BOD can also be negative. An abundance of bacteria can be detrimental to a river because it uses up the available oxygen, substantially restricting and suffocating the rest of the organisms in the river including the James River Spinymussel. To measure BOD, samples from each randomly selected location are bottled underwater in separate containers covered in solid black tape to prevent photosynthesis. The samples were then taken back to the lab at STAB and left to sit for 24 hours. The next day, each sample was uncapped and tested using the Dissolved Oxygen probe. We recorded each measurement and compared the final measurement to the original Dissolved Oxygen measurement with correspondence to the amount of time the sample sat since it was collected. The greater the difference between the first reading and the second reading, the greater the BOD.