Final Blog Post: Human Induced Agricultural Pollution: The Impact of Agriculture on Water Quality in Southern Trinidad

Results/Discussion:

Two main nutrients in crop fertilizer which promotes plant growth are nitrate and ammonium. Once agricultural sites are fertilized, more nitrogen and ammonium are applied to fields than are removed by the crops (Smil, 1999). This excessive level of nutrients in water cause algal blooms, which harms aquatic life. Nitrogen degrades ecosystems by making water more acidic, even killing some aquatic plants while promoting the growth of other kinds of plants (Weldeslassie, 2018). Excess amounts of nutrients in bodies of water will contribute to the excessive plant growth. This process is known as eutrophication, which can lead to hypoxia (Bennet, 2017). The effects of eutrophication can be massive.
Benthic macroinvertebrate communities serve a specific niche in aquatic environments. They feed on dead organism material which will later help recycle nutrients back into the system (Jun et al., 2018). An increase in nutrient levels in aquatic environments can affect benthic macroinvertebrate communities, displacing their ecological niches which will eventually affect water quality.

South Oropuche and Moruga River Water Sampling:
From June to November, it is the “rainy season” in Trinidad, which is the time of year when most of Trinidad’s average yearly rainfall occurs. Large amounts of rainfall during the rainy season potentially will flush a hoard of pollution into nearby river systems. Water sampling has been conducted during both rain events and between storms. The South Oropuche river is heavily developed by agriculture and the Moruga river has low levels of human land use. By comparing levels of fecal contamination and nutrients in the two rivers, enough data is generated to draw conclusions about the impact that agriculture is having, and how future agricultural development might influence the ecology of river systems.
Water sampling was intentionally conducted during the rainy season (June – July 2018). This was done to find out the levels of nutrients, specifically nitrate and ammonium. During rain events, nutrients from agricultural sites would runoff to nearby water bodies. It is expected that nutrient levels of nitrate and ammonium would be greater during this time, but with flooding it is probable these nutrient levels would be low. Therefore when the water samples are ran, river discharge calculations along with standard error calculations would be taken into consideration when drawing conclusions.

Two Season Benthic-Macroinvertebrate Sampling in Both River Systems:
Benthic macroinvertebrate sampling has been conducted in both the South Oropuche and Moruga rivers during the rainy and dry seasons. These macroinvertebrate communities consist of organisms such as worms, shellfish, and insects (e.g. dragonflies and mosquitoes) that spend their larval phase in water. The composition of these communities is an indicator for overall pollution and ecological health (Deborde, 2016). It is expected that there is a more diverse macroinvertebrate community in the Moruga River than the South Oropuche River. There were major differences in each season of macroinvertebrate sampling in both river systems.

Rainy Season Macroinvertebrate Sampling (June – July 2018): During the rainy season, a total of 33 macroinvertebrates have been identified from the South Oropuche, while a total of 123 macroinvertebrates have been identified from the Moruga. One single Polychaete was found in the Moruga. Historically, Polychaetes have survived mass extinctions. They are indeed native to both river systems, but none were found in the South Oropuche.

Dry Season Macroinvertebrate Sampling (January 2019): During the dry season, a total of 40 macroinvertebrates have been identified from the South Oropuche, while a total of 91 macroinvertebrates have been identified from the Moruga.
Overall, more organisms were found in the Moruga river than the South Oropuche river.

Fecal Coliform Testing:
Interestingly enough, fecal coliforms have been indicated in all the river water samples tested, including the samples from the Moruga River (i.e., the “pristine” river in the study). After all fecal coliform tests turned out to be positive, distilled water was used to test the fecal coliform test broth. After turning out to be positive, the fecal coliform results will not be taken into consideration while generating conclusions.

Future Progress:
To better this scientific study, more river water sampling and macroinvertebrate sampling can be conducted on a larger scale along with replication. Specifically, instead of three sampling sites on each river, it can be extended to 10 sites, further apart. A larger sample size tends to produce more reliable results. Replication every few years of both tests can also help produce more reliable results.

Although this research project if still being finalized, 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 underserved 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 experiment is what motivates me to want to wake up every day and continue to do this for a living.

Blog 3: The Impact of Agriculture on Water Quality in Southern Trinidad (Continued)

My field work in Southern Trinidad has come to an end. From January 15th-23rd I have conducted my last set of macroinvertebrate sampling for my research. After getting all my sediment samples, I added ethanol to kill off any decomposing bacteria and to preserve any macroinvertebrates. Because these organisms are small and there is a lot of sediment left in the collected samples (even after rinsing them through a net), I had to carefully look through each sample and individually extract all the macroinvertebrates. I spent an average of two hours sifting and observing each of the 6 samples. Between the collection and processing of these samples, macroinvertebrate samples are much more challenging than collecting and processing water samples! I really enjoyed doing it, though. These organisms are incredibly interesting and diverse. As of now, I am currently working on my final research paper. With my maroinvertebrate results, river water analyses, and fecal coliform tests, I have enough information to start drawing conclusions with the help of my mentor, Dr. Monica Palta. I am set out to answer my big question: What is the impact of agriculture on water quality in Southern Trinidad?

 

This research project has so far 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 experiment is what motivates me to want to wake up every day and continue to do this for a living.

Blog 2: The Impact of Agriculture on Water Quality in Southern Trinidad (Continued)

Since my last blog post, I have made a great amount of progress with my research. On November fourth, my faculty mentor and I went to the CUNY Advanced Science Research Center to run all 120 water samples from Trinidad for nitrate and ammonium. I was able to meet Claire Koehler, a research technician working in Dr. Andrew Reinmann’s and Dr. Peter Groffman’s labs in the Environmental Sciences Initiative at the CUNY Advanced Science Research Center. She was able to train and help me run all my samples. By comparing nutrients, levels of fecal contamination and macroinvertebrate samples, I hope to make some conclusions about the impact that agriculture is having.

                    

I used two different microplates, one to test for ammonium and nother to test for nitrates. Pipetting all the samples and reagents into wells of a mircoplate carefully was time consuming, but for me it was fun! I was able to use an eight channel automatic pipette, something that was new to me that the Pace labs do not have. After pipetting everything into each well, I placed the microplate into a microplate photometer to run my samples for the chemical compounds. Running the samples in the microplate photometer is amazing because it only takes a few minutes to get results for a vast amount of samples. The microplate photometer was also able to generate the results into a graph through a computer software.

I am going back to Southern Trinidad on January 16th to conduct my last macroinvertebrate sampling. January is the beginning of the dry season in Trinidad, so I would like to see if there is any difference with my wet season sampling. I am very excited to go back and to start writing my final research paper.

The Impact of Agriculture on Water Quality in Southern Trinidad

I have spent my summer conducting field work in Southern Trinidad to find out the impact of agriculture on water quality. This area and these river systems are very important to me personally, because my family is from Trinidad and they interact with these rivers quite a bit. The rivers here are not only the recipient of a lot of agricultural runoff (which can contain animal waste and fertilizers, among other contaminants), but of great cultural and economic importance to Trinidadians. People practicing the Hindu faith use the river for religious ceremonies, and a big part of the economy here is tourism, which means that the beaches and marine wildlife need to be clean and healthy.

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. For this reason, I have spent this summer examining how agricultural runoff contributes to microbial and nutrient (nitrogen, phosphorus) pollution.  I have also sampled and characterized macroinvertebrate communities.  These macroinvertebrate communities consist of organisms such as worms, shellfish, and insects (e.g. dragonflies and mosquitoes) that spend their larval phase in water. The composition of these communities is an indicator for overall pollution and ecological health.

From June to November, it is the “rainy season” in Trinidad, which is the time of year when most of Trinidad’s average yearly rainfall occurs. Large amounts of rainfall during the rainy season potentially will flush a hoard of pollution into nearby river systems. I have conducted water sampling, both during rain events and between storms. I have chosen to collect water samples in two different river systems in Southern Trinidad. One is heavily developed by agriculture (the South Oropouche river) and the other has low levels of human land use (the Moruga River). By comparing levels of fecal contamination and nutrients in the two rivers, I hope to make some conclusions about the impact that agriculture is having, and how future agricultural development might influence the ecology of river systems here. Before starting my field work, I walked along each river to find sampling sites.  I found three sites on each river, determining them by accessibility.

 

 

Once samples are collected, they need to be tested for fecal contamination and for nutrients (nitrogen, ammonium, and phosphorus). Fecal contamination is found by testing for the presence of bacteria (called coliform bacteria) that are typically found only in the gut of warm-blooded animals. There are many types of coliform bacteria and not all are harmful, but they do indicate that animal waste is making its way into a river. Coliform bacteria produce acid and gas from lactose, and you can take advantage of this to perform a simple test on water to see if they are there. I add 1 mL of the river water sample into a test tube with lactose and a color solution that is sensitive to pH (i.e., acidity) – kind of like litmus paper. I then agitate the solution for about 30 seconds, then leave it for 72 hours at room temperature to let the bacteria do their thing. If the broth does not change color, fecal coliforms were not present in high enough numbers to change the acidity of the water. If it turned yellow, that means that fecal coliforms consumed the lactose, lowering the pH of the water and causing the color solution to change. Interestingly enough, fecal coliforms have been indicated in all the water samples I tested, including the samples from the Moruga River (i.e., the “pristine” river in my study). Although I was unsure of the extent of contamination (only that the samples are contaminated with some level of fecal waste), it was surprising to find that both rivers have this contamination, and that contamination was found even when it wasn’t raining. When I got back to NYC, I tested the fecal coliforms tests with distilled water from Pace’s lab. It came up to be positive, so something is definitely wrong with the tests.

My nutrient analysis of river samples will require the use of analytical machines, so unlike the coliform testing, I can’t perform these analyses at the house I am staying at. Nutrient concentrations can change very quickly in water if algae and bacteria are present, so froze my samples right after collecting them, and keep them stored in the freezer until they can be analyzed. Luckily, I have teamed up with a Professor at the University of Trinidad and Tobago, where I ran a portion of my samples to measure concentrations of nitrate and phosphate, to get some experience with the analysis. I will test all samples for nutrient concentrations (nitrate, phosphate, ammonium) at the CUNY Advanced Science Research Center next month.

 

Doing my field work has been an amazing experience, and has confirmed to me the importance of the small study I am doing. Before I went to Trinidad for the summer, I tried to find other water quality studies of the rivers here, and didn’t find any. It also seemed like most residents on the island, even though they use the rivers quite a bit, are largely unaware of the presence or repercussions of river pollution there. These findings have been reflected in my experiences in the field. While collecting samples from the South Oropouche, some of the local people noticed I was collecting water samples near their homes and asked what I was doing and where I was from. I explained to them what my research was on, and they were shocked to find out what was happening in the river system they use daily. They were glad to find out that someone was conducting water quality tests on the river system they rely on for food and water. Hearing this made me happy because I felt that my research can potentially help better people’s everyday lives. I plan to go back to Trinidad in December/January to continue my study.