Marine Algae Could Sustain Ocean Food Webs in a Changing Sea

Field report

Marine algae is the foundation of ocean life; it produces more oxygen than all forests combined

Katherine Martinko is an expert in sustainable living. She holds a degree in English Literature and History from the University of Toronto.

You may not realize it, but algae forms the base of nearly every ocean food web. As ocean conditions shift and marine ecosystems face unprecedented stress, algae could become even more critical to the survival of sea life. It offers remarkable ecological benefits and sustains everything from tiny krill to the largest whales.

These are the findings of anew studypublished in Frontiers in Marine Science. Led by researchers from the Scripps Institution of Oceanography, the study makes a case for algae being the "foundation of ocean food webs" in a changing world. Up until now, it has mainly been studied for itsrole in carbon cycling, but researchers are beginning to view it as a vital indicator of ocean health.

Dr. Uta Passow, one of the study co-authors and a biological oceanographer at Memorial University, said in a press release, "Many of us have known the ecological importance of marine algae for years, and have been studying it as the base of marine food chains, but now, with ocean warming, acidification, and a rapidly changing climate, most everyone realizes that the ocean's foundation of life simply has to be protected if we want fisheries and marine ecosystems to survive."1

Marine algae refers to a broad range of aquatic organisms, from giant kelp forests and seagrass meadows to microscopic phytoplankton, but this study focuses specifically on the role of microalgae, described as "a catch-all term for the thousands of microscopic algal species and other photosynthetic organisms like cyanobacteria found in various aquatic environments."1

Marine algae is impressively productive. Its growth rates can range from doubling every day to several times per day (for reference, terrestrial trees grow over years and decades2) and it converts sunlight to biomass with remarkable efficiency. It produces more than half the oxygen in Earth's atmosphere, as well as all of the essential fatty acids that fuel ocean food chains. It is the primary food source for zooplankton, which in turn feed small fish, which feed larger predators.

When it comes to ecological impact, marine algae is a powerhouse. The study cites research from 2014 that found "phytoplankton produce approximately 50 billion tonnes of organic carbon each year — roughly half of all primary production on Earth." Some models predict that "changes in algal productivity could cascade through the entire marine food web, affecting everything from sardines to whales."1

Some algal species can thrive in waters ranging from tropical lagoons to polar seas, and even in the dark ocean depths near hydrothermal vents, and they exist in a staggering range of habitats, from sunlit surface waters to sea ice in the Arctic and Antarctic. According to Passow, "Marine algae grow wherever sunlight and nutrients meet — from the surface of the open ocean to the shallows of coastal kelp forests. They also grow in sea ice, where ice algae form the base of the polar food web, so there are many niches for algal production."3Compared to terrestrial plants, marine algae require no freshwater, no soil, and no fertilizer — just sun and seawater.

Much of marine algae's significance lies in its versatility. When researchers were asked what forms algae take in the ocean, they offered the following observations:

It will be harder to convince a skeptical public that protecting microscopic algae is a critical priority, although it's probablymore urgent than saving charismatic megafauna—also a focus of conservation campaigns. When asked about how to get people to care about organisms they can't see, Passow replied:

This research is an interesting initial foray into marine algae's critical role in ocean food webs, with insights into how shifting conditions may reshape algal communities, likely through a combination of species migration and adaptation. Once it's thought of as the foundation of all ocean life (invisible, rather than conspicuous), it could be monitored and protected much the same way we track forests on land — assessed for health, diversity, and productivity.

You read the full studyhere.

Passow, Uta. "Marine snow and the importance of algae in ocean food webs." Frontiers in Marine Science, 19 Jan. 2023.

Falkowski, Paul, et al. "The Rise of Oxygen Over the Past 200 Million Years." Nature, vol. 431, 2004. doi:10.1038/nature03064

Passow, Dr. Uta. "Re: Media inquiry about marine algae study." Received by Katherine Martinko, 20 Jan. 2023.