Microbial community structure in a pulp mill effluent-impacted river

Pulp mill effluent is the primary source of pollution to the Fenholloway River, located near Perry, Taylor County, Florida, USA. Since 1954, the Fenholloway River has received approximately 50 million gallons of effluent daily, which accounts for up to 90% of the river flow. Studies have provided extensive evidence of the presence of the masculinization of female fish species, diminishing seagrass and elevated nutrient levels downstream of the facility. Research findings have also indicated that some microorganisms degrade phytosterols, which produce environmental steroids, known to contribute to endocrine disruption of female mosquitofish. Despite the role of microorganisms in this perturbed water body, there has not been an exhaustive study of the microbial community structure.

The pulp mill facility has undergone recent plant modifications yet the Fenholloway River still remains challenged with nutrient loading and specific conductance to satisfy Class III water quality standards. Therefore, we hypothesized that the Fenholloway River selects for unique microbial communities, abundance and diversity compared to a relatively pristine water body, the Econfina River, which has not been impacted by pulp mill effluent. Four water samples were collected from the Fenholloway River and one water sample was retrieved from the Econfina River in June 2009. For microbial water quality analysis, the present study made use of membrane filtration and multiple-tube fermentation techniques for the presence of Enterococci spp., total and fecal coliforms. The Fenholloway River had 5-10 times greater numbers of Enterococci spp., total and fecal coliforms compared to the Econfina River. Predacious marine Bdellovibrio spp. numbers were low downstream, nearest to the pulp mill facility, compared to further downstream sites along the river and the reference stream.

Total phosphorous in the Fenholloway River ranged from 0.14-0.86ppm but was undetected in the Econfina River. An upstream sample near the pulp mill had a NO3 level of 10.45ppm compared to 0.05ppm of the reference water body. Dissolved organic carbon levels from the Fenholloway River were also slightly higher near the area of discharge. The results of this study indicate that the microbial community abundance of the Fenholloway River is affected by the pulp mill effluent. The difference in nutrient levels observed between the Fenholloway and Econfina Rivers likely contributes to the abundance and diversity of the microbial communities.