Undergraduate Research

Bay Watch: Tracking Long-term Changes in Nutrients and Phytoplankton Composition in Narragansett Bay, RI

Each summer, the University of Rhode Island Graduate School of Oceanography (GSO) hosts undergraduate students from all over the country to participate in oceanographic research. These Summer Undergraduate Research Fellows (SURFOs) have not only been working with GSO scientists, but they also have spent part of their time learning how to communicate this science to the public. Read on to find out what they have been up to, and why everyone should be as excited as they are about their work.

Kaelyn is a senior at the College of Coastal Georgia majoring in Biological Sciences & Environmental Sciences with minors in Chemistry & Mathematics. Kaelyn spent her summer working in the Rynearson lab analyzing data from the Narragansett Bay Long-Term Plankton Time Series.

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Phytoplankton are marine plants that may be more relevant to your life than you may know. Through photosynthesis, phytoplankton use a green pigment (chlorophyll a) to absorb light to make their food. Through this process, they produce about 50% of the world’s oxygen! So, every other breath you take, you can thank a phytoplankton cell.

Some examples of phytoplankton. Image credit: Kaelyn Tyler

Phytoplankton come in many different shapes and sizes, and they can produce different amounts of oxygen.  Because of these factors, it is important to know the community composition, or “the who” and “the how many”, of these phytoplankton in our local and global ocean systems. Factors such as nutrient availability, environmental conditions, or time of year can affect the abundance and diversity of these phytoplankton. However, studying phytoplankton is difficult because many are smaller than the width of a human hair and they grow at different rates on seasonal, annual, and decadal cycles.

So how can we study something that is affected by many different factors, so that we can track long-term changes over time?

Well, imagine a downtown parking lot. In the parking lot, there are many different types of cars and people. Some people have very high-paying, corporate jobs that drive Teslas, some are families in minivans while others are blue-collar workers in trucks. If you were a fly on the wall, watching and collecting data on this parking lot for a long time, you might start to notice trends based on the composition, or the “who” and “how many”, of different cars and people are in the parking lot. Maybe you start to see seasonal trends like more trucks in the summer than in the winter. You might be able to connect this observation to the increase in construction and landscaping work in summer months, indicating seasonal shifts in the work force. Maybe you notice more long-term changes like less trucks and more Teslas, possibly because the town is becoming wealthier. Or on the other hand, maybe Teslas have become more affordable over time.

Conceptual parking lot showing change in composition over time. Image credit: Kaelyn Tyler

Using these fly-on-the-wall observations of this one, highly trafficked area, you can start to make inferences about the total population, diversity, economics, and community function of the town. In this same way, if we were to have fly-on-the-wall observations of nutrients in the water and the “who” and “how many” of phytoplankton are present in a specific area, we could start to make inferences about their composition (total population and diversity), resource use (economics), and species interactions (community function). Luckily, we have these fly on the wall observations for Narragansett Bay (NBay) in Rhode Island, USA.

The NBay is an estuary, where inland freshwater and oceanic saltwater meet. The NBay has been monitored weekly through The Narragansett Bay Long-term Plankton Time Series (NBPTS) for 60 years, making it one of the longest running plankton time series in the world! These data act as our fly-on-the-wall observations for the NBay. So, instead of types of people and cars in the downtown parking lot, this time series records both environmental and biological data. These data are currently being used to understand the dynamics and changes in nutrient concentrations and phytoplankton abundance in NBay over time.

Through analyzing these data, an increase in temperature and a decline in chlorophyll a has been observed. This is potentially concerning because we use chlorophyll a as a proxy for biomass, or how much phytoplankton is in the water at any given time. My research focuses on tackling specific questions: (1) is the decline in chlorophyll a related to the amount of nutrients in the water?, and (2) is community composition (the “who and how many of each species are there) changing with this decline in chlorophyll a?

Kaelyn sampling off the side of The Capt’n Bert in Narragansett Bay Image credit: Dr. Patricia Thibodeau

This summer, I have been able to sample for and work with the data from the NBPTS to address these questions. Every Monday, we take the boat, The Capt’n Bert, out on the water to collect water samples, measure environmental conditions, and use nets of different sizes to catch phytoplankton and other organisms in NBay. When not sampling, I worked on analyzing the 60 years’ worth of data to understand the dynamics of NBay and its phytoplankton community.

Answering these questions will give us a better idea of how the phytoplankton community is changing over time and in response to climate change. As our population grows and our climate changes, protecting our major oxygen producers are more important than ever. As global temperatures are rising, phytoplankton are becoming more vulnerable, so monitoring these producers and using data collected to inform environmental policies is going to be one of our most powerful weapons in mitigating climate change.

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