Preparing for an expedition to the Southern Ocean is an adventure in itself. You gather your base layers, boots, goggles, socks, and pack your camera and lenses, envisioning the polar environment—one of the most extreme on Earth. Imagine the biting wind on your cheeks and the sight of albatrosses, prions, penguins, humpback whales, and orcas, thriving in such harsh conditions. The excitement is palpable as you prepare to study the microscopic world that sustains this vast ecosystem. Beneath the icy waters lies an invisible world of phytoplankton, microscopic organisms that are the unsung heroes of the marine ecosystem. Despite their size, phytoplankton play a colossal role in maintaining life on Earth. These single-celled autotrophs perform photosynthesis, drawing carbon dioxide from the ocean and atmosphere, and in return, they produce over 50% of Earth’s oxygen, rivaling the oxygen output of all terrestrial plants and trees combined. Derived from the Greek words phyton (plant) and planktos (drifter), phytoplankton drift in ocean currents, forming the foundation of the marine food web. They are descendants of cyanobacteria, ancient organisms that began oxygenating Earth’s atmosphere 800-600 million years ago. Today, these tiny solar panels continue to be pivotal in carbon cycling and are critical in combating climate change
Understanding phytoplankton is crucial, especially in the Southern Ocean, where they contribute significantly to carbon sequestration and marine life sustenance. The research aboard the expedition involves collecting and analyzing water samples to study phytoplankton blooms especially due to hydrothermal vents, their composition, and their response to environmental changes near the Australian Antarctic ridge. This includes measuring chlorophyll a, organic carbon, nutrients, and assessing stress levels due to varying iron concentrations. Iron, a limiting nutrient, is essential for phytoplankton growth, especially in the Southern Ocean where it is in short supply. The study investigates how hydrothermal vents and aeolian dust contribute to iron availability and influence phytoplankton productivity. The research aims to understand how climate change, through warming waters and altered nutrient delivery, impacts these primary producers and, consequently, the entire marine ecosystem.
The expedition, led by Dr. Kevin Arrigo and his interdisciplinary science team including physicists and chemists, will involve deploying CTDs (Conductivity, Temperature, and Depth sensors) to collect physical data from various depths. Advanced techniques like fluorescence assays will help determine the health and productivity of phytoplankton populations. This collaborative effort exemplifies the power of teamwork in scientific research, a value I aim to instill in my students through similar collaborative projects. Participating in this expedition offers a unique opportunity to witness and contribute to groundbreaking research. It not only enriches my understanding of marine ecosystems but also enhances my teaching by bringing real-world science into the classroom. Sharing this experience with my students, especially first-generation college attendees, will inspire them to appreciate the interconnectedness of oceanic life and climate systems, fostering a generation of environmentally conscious scientists.
Every day aboard our research vessel starts before the sun rises, with a shift beginning at 3 a.m. and running until 3 p.m, and another from 3p.m to 3 a.m. Our base of operations for the biology team is the hydro lab, where we handle the crucial task of filtering water samples collected after each CTD cast. This instrument is our window into the unseen dynamics of the Southern Ocean, capturing water from depths of up to 200 meters. The CTD rosette (a frame that includes 24 Niskin bottles for collecting water samples) is a critical tool that measures the ocean’s physical properties, allowing us to understand how the ocean physics interacts with life. It collects water samples at various depths depending on the properties of the water at that location. These bottles capture water from specific layers of the ocean, which we then analyze for nutrients, particulate organic carbon (POC), and the phytoplankton community. One of the most captivating parts of our work is studying phytoplankton.
After filtering the water samples, we use a Planktoscope, a sophisticated device that captures detailed images of the plankton in our samples. This tool enables us to quickly process large amounts of data, classifying plankton into major taxonomic groups using automatic image recognition software. Back in the lab, we conduct further analysis under an optical microscope to identify, count, and measure the biovolume of phytoplankton cells, which helps us estimate the carbon biomass of these essential organisms.
We also analyze the chlorophyll a content, an indirect indicator of phytoplankton abundance, by acidifying the chlorophyll a with a drop of 10% HCl. This process mimics the digestion of phytoplankton in the guts of zooplankton, releasing phaeopigments for analysis. We then run the samples through a fluorometer, which measures the fluorescence of the chlorophyll and phaeophytin. The fluorometer detects the red light emitted by the two pigments when excited by blue light, providing data on phytoplankton concentration across different ocean depths.
Our work in the Southern Ocean is part of a broader research study aiming to understand the region’s unique ecosystem and its response to environmental changes. By collecting and analyzing these samples, we gain insights into the health of the ocean and its role in regulating our planet’s climate. Each filtered drop of water tells a story of life beneath the waves, a story we are privileged to explore and share.
