Eutrophication

The Effects of Harmful Algal Blooms and Eutrophication

Introduction

Eutrophication, by definition, is a process where bodies of water receive excess nutrients that stimulate excessive plant growth. Eutrophication results from continuous pollution in the form of agricultural run-offs or sewage outflows. Fertilizers and sewage are both rich in nitrogen and phosphorus, which are both nutrients essential for plant growth. However, these nutrients are typically low in content in aquatic environments, which limits the growth of algae and plants, but with an increased amount of these nutrients, more plants are able to grow, disrupting the natural environment. Eutrophication is becoming more and more common throughout the world. One main plant growth of concern is that of harmful algal blooms, or HABS. Harmful algal blooms are the first stage of eutrophication. They turn water different colors, such as red, mahogany, brown, and even green. This was the case along the coast of Guangdong in southern China. Here, the algal blooms “inflicted significant negative impacts on the society” and “devastated aquaculture and destroyed natural marine ecosystems.” (Qi et. al 2004) Harmful algal blooms affect more than just bodies of water, however. They affect everything in the water and anything that consumes something from that body of water, from plankton to humans.

Nutrient loading will appear to have a positive effect on plant growth in the beginning, causing them to grow quickly. In this experiment, the “high” aquarium plants will probably begin growing much faster than those of the “control” aquarium. However, after a few weeks they will probably begin regressing or even dying, while the “control” and even “moderate” plants are thriving. Through this experiment, I hope to gain a better understanding of the effects of agricultural runoff on surrounding aquatic environments. The experiment will provide a hands on look at eutrophication and its effects on my surroundings.

Methods

Terrestrial Component Setup

To begin the terrestrial setup, our TA obtained six pots, filled them with potting soil, added 100 milliliters of water, then more potting soil, and finally planted a bean seed in the soil. The planted pots were placed above the aquariums containing different levels of Elodea. Two plants were placed on chicken wire above the “Control” aquarium, two above the “Moderate” aquarium, and two above the “High” aquarium.

Aquatic Component Setup

For the aquatic component setup, our TA took Elodea (elodea densa) and laid it out to dry on a paper towel, then divided it into three fairly equal portions. The mass of the Elodea was then found using and electronic balance. The mass was then recorded in a row labeled “Control.” The first amount of Elodea was then placed in an aquarium labeled “Control.” This step was then repeated with a second set of plants. The mass was recorded in a row labeled “Moderate” and the plants ere place in an aquarium labeled “Moderate.” This was repeated once more, with the mass recorded in a row labeled “High” and the remaining plants were placed in an aquarium labeled “High.” Next, we measured the nitrate, nitrite, and phosphorous of the aquatic environments and recorded these levels in a table. The class was divided into five groups and each group was assigned to measure one water quality variable. My group measured pH for each of the tanks and recorded the measurements in a table weekly. We also measured the height of plant 1 and 2 for all three levels. At the end of the seven week study, we measured the pH of the three sources of soil, as well as the nitrogen, phosphorous, and potassium of the soil sources using test kits provided to us. We then used the lists in the lab manual to determine if the soil nutrients were depleted, deficient, adequate, sufficient, or had a surplus.

Results

Figure 1 вЂ" Water quality parameters: Dissolved Oxygen

Figure 2 вЂ" Water quality parameters: Conductivity

Figure 3 вЂ" Water quality parameters: pH

Figure 4 вЂ" Water quality parameters: Optical density

Figure 5 вЂ" Water quality parameters: Temperature (Ð'oC)

Figure 6 вЂ" Change in nutrient levels