Bayou Lafourche

population explosion of these microscopic organisms can quickly consume nearly all
available oxygen, greatly impacting fisheries and potentially resulting in fish kills.
Insecticides used to target agricultural pests can also decimate aquatic insects vital to
the productivity of the Bayou Lafourche ecosystem. Insects often provide the primary
source of nourishment to larval fish. Some of these fish will mature to become part of a
lucrative sport fishing industry. Others will be consumed by other small fish, which will,
in-turn, be consumed by larger sport fish. The introduction of pesticides threatens to
collapse this food chain by eliminating the base on which it is built. The impact is not
limited to aquatic organisms. This community of insects and fish supports countless
larger terrestrial communities of amphibians, birds, reptiles, and mammals.
When agricultural herbicides enter water bodies, they often execute their largest impact
on native vegetation. Native aquatic plants are a food source to many species and act
as shelter to others. When native plant species are weakened by herbicides, they are
often replaced by exotic or introduced species. Exotic species are not as well suited to
fulfill the roll as food and shelter to aquatic animals. The result is a decline in
productivity at every level similar to the impact of insecticides as discussed above.
Perhaps the greatest potential impact from agriculture is sedimentation. As raindrops
impact bare soil, they dislodge sediment particles that are carried by runoff over fields,
into drainage channels, and eventually into receiving waters. Sediments can fill
channels and limit their ability to convey water. This ability is especially important in
Bayou Lafourche. The water conveyed by the bayou is used to irrigate fields and to
provide drinking water to thousands of homes. Sediment clouds water and limits the
production of food sources for aquatic animals. Sediment can also carry pesticides,
herbicides, fertilizers, and other potentially harmful chemicals. Sedimentation potential
is increased by eroding channel walls and improper agricultural practices.
Urban Runoff
Urban NPS pollution has severely impacted many of the water bodies receiving runoff
from major cities in Louisiana, but urban NPS pollution is not limited only to large
communities. Rural areas such as those near Bayou Lafourche contribute to urban NPS
pollution as well. The Bayou Lafourche Watershed is also home to Louisiana Highways
1 and 308. These roads are heavily utilized for commercial transport, agricultural
27