THE EFFECT OF WASTEWATER INFLUX IN THE NUTRIENT COMPOSITION AND ABUNDANCE OF ANOXYGENIC PHOTOTHROPHS IN TROPICAL DAIRY WASTEWATER LAGOONS
V. Román, F.A. Fuentes and H.L. Ayala, University of Puerto Rico at Humacao, Department of Biology
Dairy farm operations generate large amount of wastes, organic carbon and nutrients, that are decomposed by microbes in oxidation lagoons. When dairy farm operations close, oxidation lagoons remain in the field for several years until they are drained and covered with soil. Thus, it is very important that microbes remove all organic carbon and nutrients before drainage to avoid contaminating surrounding soils and bodies of water. Anoxygenic photothrophic bacteria are among some of the populations involved in organic matter decomposition and odor control in oxidation lagoons. These bacteria that carry out photosynthesis without release oxygen. Under anoxic conditions they synthesize bacteriochlorophyll-a, that is a photosynthetic pigment and that absorbs light energy at 580 and 770 nm. The objectives of this study are to compare the effect of dairy wastewater influx in the nutrients composition of oxidation lagoons, and the abundance of anoxygenic photothroph bacteria. We analyzed the nutrients and photosynthetic pigment composition of two active lagoons, that were constantly receiving dairy wastewater, and one inactive lagoon, that did not receive any dairy wastewater during the last two years. Chemical analysis of the two active lagoons revealed that they accumulate significant amounts of carbon, ammonia, phosphate and sulfide. In the inactive lagoon those nutrients were mostly depleted, and higher amounts of oxygen, total iron and calcium were observed. Absorption spectra of extracted pigments from the active lagoons revealed that bacteriochlorophyll- a was the most abundant pigment present in those lagoons while in the inactive lagoon chlorophyll- a was the abundant form. Also the PCR amplification for the pufM gene, which encodes for the M subunit of the light reaction centre complex of these bacteria, revealed his presence in culture and original samples, including in the inactive lagoon. This result suggests that anoxygenic photothtophs seem to be more abundant in the active oxidation ponds; while they were below the detection limit in the inactive lagoon. In summary, the lack of dairy wastewater influx into a dairy lagoon resulted in a decrease in nutrient and carbon concentrations of the pond, which also decreased the abundance of anoxygenic photothrophic bacteria. These studies were supported by the NIH- RISE Program of the University of Puerto Rico at Humacao, Grant # 5R25GM075348- 03 and the BioMinds Program.
**This work must be include in the Microbiology Area.**
