The Impact of Agriculture on Water Quality in Southern Trinidad (End of Summer Report)

From June 10th – July 30th, I conducted field work in Southern Trinidad to find out the impact of agriculture on water quality, specifically how agricultural runoff contributes to microbial and nutrient (nitrogen, phosphorus) pollution, and impacts macroinvertebrate communities (an ecological indicator for overall ecological integrity). I conducted water and macroinvertebrate sampling during both the wet and dry seasons (Summer–Fall 2018) in two different river systems in Southern Trinidad, one that is heavily developed by agriculture (South Oropouche river) and the other with low levels of human land use (Moruga river).

The goals of the project are to assess: (1) the level of different pollutants (fecal coliform bacteria, nitrogen, and phosphate) contributed by agricultural runoff, (2) how pollutant loading varies by season, and (3) the health of river biota in watersheds dominated by agricultural activity.  Due to the importance of both agriculture and water quality to the human population living there, southern Trinidad is considered an appropriate model to study human-induced water pollution and its effects on ecosystem and human health. Three methods were used to answer my research questions: (1) Macroinvertebrate sampling: Using a kick net to acquire sediment samples from three points in each river body, later picking out and identifying macroinvertebrates found in each sample; (2) Fecal coliform indication tests: Testing water samples from three points in each river system for fecal coliforms; (3) Water quality testing: Acquiring a total of 126 water samples to determine nutrient concentrations (nitrate and phosphate).

I have successfully collected 126 river water samples to analyze for nutrients, conducted macroinvertebrate sampling in several spots in each river on two different days, and sampled for fecal bacteria (coliforms) four times in each river. I have also successfully run 42 of my river water samples at the University of Trinidad and Tobago, using a HACH Spectrophotometer to determine nutrient concentrations (nitrate and phosphate). The highest concentration for nitrate was 1.2 mg/L, in the lower South Oropuche River. The highest concentration for phosphate was 1.52 mg/L, in the upper Moruga River. I will run all the samples over again for nitrate, phosphate and ammonium at the CUNY Advanced Science Research Center in New York City. All eight fecal bacteria tests all came out positive for fecal coliforms.  I am not sure of the levels of fecal contamination in the rivers (only that all of the samples were contaminated with some level of fecal bacteria), but it was surprising to find that both rivers have this contamination, and that contamination was found even when it was not raining.

About a total of 52 macroinvertebrates were found in the Moruga sediment samples while a total of 23 macroinvertebrates were found in the South Oropuche sediment samples. Some of the organisms I was able to identify to higher (more general) taxonomic ranks, such as mosquito larvae, bivalves and crabs, but I’m unsure of their exact species. I have posted photos of them onto iNaturalist to properly identify them to lower taxonomic levels, but was unsuccessful with obtaining identifications. Dr. Mike Rubbo, an Environmental Studies and Science faculty member at the Pace Pleasantville campus, has a lot of experience with macroinvertebrate sampling and has offered to identify the species I collected.

One finding that matched my expectation going into this study is that I have definitely found more macroinvertebrates in the relatively undeveloped Moruga River than the heavily impacted South Oropuche River. The intensive macroinvertebrate sampling was probably the most difficult, because there are many factors that play into this sampling. I did this six times a day, for two days (in almost 90 degree weather, rain and sunshine) and was very time consuming. Physically going down to the sampling points, going into the river, using a kick net, and sifting through the sediment took a lot of time and energy. My mentor, Dr. Monica Palta has certainly helped me grow as a researcher over the course of this research project. Although I have had a very active and independent role in the research, I was always under her remote supervision. With her help, I was able to establish a relationship with researchers at the University of Trinidad and Tobago. Before leaving for Trinidad, she trained me to establish proper field sites and conduct the multiple studies I have completed.

Although this research project is still ongoing, so far it has had a major impact on me. The research project itself is trying to figure out how agriculture can affect water quality and stream organisms. Seeing that human activities can affect nature and ecology is not new to me, but new to many of the local people of Southern Trinidad that live on and use these rivers. As an Environmental Science major and a person of Trinidadian heritage, completing this research project is just the first step for me in my career goal of developing meaningful solutions to environmental problems that affect undeserved communities of people. The fact that people I know and care about are the ones impacted by the particular environmental problems affecting rivers in Southern Trinidad makes my project of particular importance to me. The feeling of success and fulfillment I receive after completing every research endeavor is what motivates me to want to wake up every day and continue to do this for a living.

Author: Danny Deo

Danny Deo Pace University NYC, Dyson College of Arts and Sciences Department of Environmental Studies and Science

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