Climate Change Coastal Management Physical oceanography

SURFO SPECIAL: The oxygen puzzle of the Gulf of Saint Lawrence

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. Although their research experience was virtual this summer, they still did a fantastic job. Read on to find out what they have been up to, and why they everyone should be as excited as they are about their work.

 Adalberto Ubinas Romero is a rising senior at the University of Puerto Rico at Humacao majoring in coastal marine biology. He is interested in water column health, plant pathology, and taxonomy. He aspires to finish his undergraduate degree and continue graduate studies with the goal of obtaining a PhD.

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The Gulf of St. Lawrence is a relatively small sea, located between Newfoundland and Nova Scotia, Canada. The Gulf receives a constant input of fresh water from the St. Lawrence river which creates the St. Lawrence estuary, known to be one of the largest estuarine systems of the world. The presence of this estuary system is home to a diverse range of commercially important fish species such as, the Atlantic cod, snow crabs and different types of flounder fish. The Gulf is also home to species such as the Beluga whale, the white sided dolphin and sperm whales which makes the region not only have economical value but also biological significance.

A map showing the location of the Gulf of Lawrence. Image credit: The Magazine of Divers Alert Network

A legacy of Questions

The importance of the Gulf has been motive for extensive research mainly with purpose of keeping a record of the health of gulf and factors that could affect the bio diversity and therefore the economy of the area. In fact, historical records show that research has been performed since the 1930’s.

This is a picture that I took of the “Pearldiver,” the glider deployed in 2019 that obtained the data that we are currently using in our research.

When understanding the status of a body of water certain parameters are key factors that we need to look at. These base measurements are the temperature, the salinity, the pH (which helps us understand how acidic or basic the water is) and the dissolved oxygen content of the water. Historically speaking these measurements have been taken from fixed stations or boat expeditions.

Currently the use of technology has become a significant ally for obtaining and recording information. For our research project we have implemented the use of Underwater Gliders in order to obtain this data. Gliders are a type of Autonomous Underwater Vehicle (AUV). These vehicles record measurements depending on the type of sensors that they carry and help us obtain a plethora of variables that we desire to observe in the laboratory. One of the biggest advantages of using these vehicles is the fact that we can remotely pilot them to obtain discrete and/or sustained measurements of our study area.

So what’s the big deal with oxygen?

In the last century the focal point that has caused the Gulf of St. Lawrence to become a scientific hotspot is how the oxygen levels of deep water zones are significantly different when compared to the rest of the water column. The water of these deep basins is described as anoxic, meaning it has dangerously low oxygen levels. This phenomenon creates a domino effect that could potentially have a permanent impact on not only the wildlife communities that inhabit this region but also the lifestyles of those who depend on the Gulf to sustain their families, such as the fishermen, fish supplying companies, the restaurants and even transportation services.

This is a cross sectional graph that I made of the water column using data from the Pearldiver in August 2019; Notice the dark red low oxygen levels at the bottom.

There are many factors that could be the reasons for these low oxygen zones such as, climate change, warm low oxygen currents that could deplete the existing oxygen and even bacteria that may use up oxygen as they break organic material down. However, the extent of this last reason has not been fully studied or understood as of now.

So, what are we doing to help explain this?

This project was part of an internship program located at the University of Rhode Island. Due to the COVID-19 pandemic, the team was forced to work from a distance but thankfully the data we used are provided by the glider. This allows us to contribute not only to the scientific knowledge but also to this interesting phenomenon that is found in the Gulf of St. Lawrence, Canada.

The objective of our research is to understand the spatial and temporal extent of the low oxygen regions of the Gulf of St. Lawrence. Once data analysis is completed, a fusion of data will be created based on the obtained glider data, existing databases and literature in order to develop a timeline of past low oxygen events in the Gulf and to understand how these oxygen levels flux, extend and impact other factors of the area.

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