By: Brennan Hutchison, 0704996
UPPER LAKE PONTCHARTRAIN BASIN, LOUISIANA- It has been over 5 years since Hurricane Katrina made landfall in Louisiana in August of 2005, but the aftermath and problems Katrina has caused are still being seen today.
As a result from Hurricane Katrina, 57% of residents were displaced from their homes in the Lower Lake Pontchartrain Basin area. The residents lost everything and were forced to move to another location as their homes were no longer considered safe. This caused an increase of 62,000 residents in the Upper Lake Pontchartrain Basin, which drains into Lake Maurepas. With a substantial increase in population, residential and urban land use increased dramatically.
Above- Construction in the Upper Lake Ponchartrain Basin, which drains into Lake Maurepas.
A study done by K. Silcio and his colleagues from the Department of Chemistry and Physics at Southeastern Louisiana University, researched the impact that the sudden increase in population is having on the nutrient levels in Lake Maurepas compared to the levels before Katrina hit. This study which is published in the latest issue of Chemistry and Ecology, proves the problems we still face 5 years after Hurricane Katrina hit.
A concern in the Upper Lake Pontchartrain Basin and in Lake Maurepas is due to the shift in human population after the hurricane. This shift runs the potential for increasing nutrient levels in domestic run-off and wastewater. The study selected nine sites for sample collection, from June 2007 to March 2008, which were used to examine nutrient concentrations at various locations in the lake. The results of this test were then compared to two results taken prior to the hurricane by other studies to see if any differences in nutrient levels were seen.
Areas draining into Lake Maurepas saw the greatest increase in population after hurricane Katrina making this lake the prime focus in the study. The study tested and compared pH levels and phosphate and silicate concentrations before and after the hurricane. The results of the pH comparison showed the pH levels have not changed in response to the human population shift. However, the results of the comparison of phosphate and silicate concentrations show a much different result.
The study found the concentration of phosphate decreased as water moved from the inlet sites to the middle of the lake. The average concentration of phosphate at both the midlake and outlet sites was very similar, but the inlet sites were shown to have a higher concentration than both the midlake and outlet sites. When comparing the results of his study to results taken before the hurricane Silcio commented saying: “there is a clear increase in the level of phosphate in the surface water of Lake Maurepas.” The results show phosphate concentrations are 3.4 times higher than they were prior to hurricane Katrina. Silcio adds that these increased levels are most likely due to: “the fertilization of lawns as a direct result from the construction of the new housing needed to accommodate the influx of people moving to the Upper Lake Pontchartrain area after the hurricane, as well as the amount of residential land use created at the expense of undisturbed land that contributes less phosphate pollution.”
The same result was seen with silicate, where the concentration decreased as the water moved from inlet sites towards the center of the lake. It was also seen that the concentrations of the midlake and outlet sites was similar while the silicate concentrations at the inlet sites were significantly higher than both the midlake and outlet sites. Currently, silicate concentrations are 2.5 times greater than they were before Katrina. Silcio commented on these results saying: ``the rapid infusion of human population into the Upper Lake Pontchartrain Basin and the concurrent growth in construction has led to increased urban and residential run-off and increased levels of silicate in the surface waters of Lake Maurepas.``
Hurricane Katrina forced an increase of 62,000 residents in 2005 to the Upper Lake Pontchartrain Basin but the effects are still being seen currently, 5 years after the disaster. As a direct result from the rapid population increase there is an increase in construction and residential areas which are causing an increase in run-off and silicate and phosphate pollutants are finding their way into Lake Maurepas and surrounding bodies of water. As the concentration of these pollutants increases the organisms living in these bodies of water will be negatively affected. The water sources will become polluted and any food sources from the lakes will not be safe to eat. Five years later we are still constantly reminded of the problems caused by the disaster of Hurricane Katrina.
Silcio, K. , Ball, K. , Risley, R. and Voegel, P. D.(2010) 'Changing nutrient levels in Lake Maurepas following human population shifts in response to Hurricane Katrina', Chemistry and Ecology, 26: 5, 327 — 337.