Study Links Ocean Biomass Growth to 540 Million Years of Biodiversity

A recent study conducted by researchers at Stanford University has provided groundbreaking insights into the evolution of ocean life over the past 540 million years. The study highlights a significant increase in marine biomass, suggesting a deep connection between the amount of life in the ocean and its biodiversity. Published in the journal Current Biology, this research aims to fill a critical gap in our understanding of historical ocean ecosystems.

The study, led by Pulkit Singh, a postdoctoral scholar in Earth and Planetary Sciences at the Stanford Doerr School of Sustainability, utilized data from over 7,700 marine limestone samples collected from more than 100 published studies. Each sample was meticulously analyzed using a technique known as petrographic point-counting, which measures the percentage of skeletal remains, such as shells and algae, to estimate the biomass of marine organisms at various points in Earth's history.

According to Singh, “Understanding the amount of biomass is important because it represents key traits about an ecosystem that are not captured by the number of species or even the number of niches that they fill.” The findings indicate that while ocean life has gradually increased over time, significant declines occurred during major extinction events, including the Permian-Triassic extinction, which witnessed a dramatic drop in shell material to just 3 percent.

Professor Jonathan Payne, a senior author of the study, emphasized the uniqueness of this quantitative effort, stating, “The first quantitative effort to document and graph biodiversity across geological time was made in 1860, but until Pulkit’s paper, there’s never been a corresponding biomass-across-time paper.” This historical context helps illuminate how marine biodiversity and biomass interact and evolve.

The researchers discovered that the earliest samples from the Cambrian period revealed low shell content of under 10 percent. However, as time progressed into the Ordovician period, beginning around 485 million years ago, shell percentages increased significantly, aligning with the Cambrian Explosion—a time of rapid diversification in marine life.

By the Cenozoic era, the volume of shells had surged above 40 percent, largely due to the proliferation of mollusks and corals. The study posits that increasing biodiversity has allowed ecosystems to utilize energy more efficiently, consequently supporting greater life forms and enhancing biomass. Singh noted, “The overall idea is that there is more food available in ecosystems and because of that, ecosystems can support more life.”

Despite the encouraging historical trend of increasing biomass, the study also pointed to present-day challenges. Oceans face unprecedented threats from human activities such as overfishing, pollution, and climate change, which could jeopardize the delicate balance of marine ecosystems. “Today’s oceans are complicated given the extent of human activity that’s rapidly altering conditions planet-wide,” Payne warned.

Experts agree that the ongoing loss of biodiversity may have dire consequences for ocean health and productivity, potentially leading to long-term reductions in biomass. The study serves as a crucial reminder of the interconnectedness of biodiversity and ecosystem health, underscoring the necessity for conservation efforts. As Payne aptly concluded, “Our findings show that overall biomass is linked to biodiversity and that losses in biodiversity may suppress productivity for geologically meaningful intervals, adding one more argument of why conserving biodiversity is essential for the health of humans and our planet.”