In a groundbreaking investigation that stretches across the panorama of Earth’s vast marine history, researchers at Stanford University have achieved an unprecedented measurement of how oceanic life abundance has evolved over the past 540 million years. This exhaustive study reveals a broad upward trajectory in the total biomass of marine organisms, demonstrating that despite periodic catastrophic downturns driven by mass extinction events, the general trend over hundreds of millions of years is one of increasing abundance. This seminal work, published in Current Biology, aligns elegantly with historical observations of rising marine biodiversity, offering compelling evidence that these two fundamental ecological parameters – biomass and biodiversity – are intricately linked through deep evolutionary time.
Central to the significance of this research is the concept of biomass – the cumulative mass of living organisms within an ecosystem – which encapsulates essential ecological traits not readily deduced from biodiversity counts alone. While past studies have meticulously chronicled species richness and niche diversity, the quantification of biomass over geological time had remained an elusive, unmet challenge despite its crucial role as an indicator of ecosystem productivity and ecological energy flow. Pulkit Singh, lead author and postdoctoral scholar in Earth and Planetary Sciences at Stanford’s Doerr School of Sustainability, undertook this enormous endeavor to fill this knowledge gap, painstakingly compiling data from thousands of marine rock samples that preserve skeletal remnants, acting as a tangible proxy for marine life’s historical abundance.
The methodology depended primarily on petrographic point-counting, a painstaking lab technique involving the preparation of ultra-thin slices of limestone that allow scientists to peer through and quantify the proportion of shell material under a microscope. This technique, although time-consuming, is vital for accurately documenting the percentage of skeletal content within rock layers formed over disparate geologic periods. The researchers’ database encompasses over 7,700 samples drawn from global marine limestone outcrops, allowing a statistically robust reconstruction of biomass fluctuations across diverse paleoenvironments spanning the Phanerozoic eon.
The fossil record from the Cambrian period, which marks the dawn of modern animal life approximately 540 million years ago, indicates a modest presence of skeletal material, with less than 10 percent of rock samples comprising shells. This coincides with the explosive Cambrian diversification event, a biological renaissance during which marine ecosystems became increasingly complex and varied. Over the ensuing Ordovician Period, shell biomass experienced a marked increase, paralleled by the emergence and radiation of calcifying sponges, echinoderms—including precursors of starfish—and a myriad of arthropods such as trilobites. This evolution of shell-producing taxa reflects not only an increase in diversity but also a rising contribution to ecosystem biomass.
For nearly 230 million years following these early Cambrian and Ordovician blooms, marine shelly biomass remained robust, often exceeding 20 percent by volume in the rock record. Yet this sustained abundance was punctuated by profound declines linked to the planet’s major extinction pulses. The Late Devonian extinction events brought a significant reduction in shell prevalence about 375 to 360 million years ago, an ecological wrench that dramatically rearranged marine communities and diminished their biomass. The most severe decimation, however, occurred during the Permian-Triassic “Great Dying” roughly 250 million years ago, a cataclysmic extinction episode that caused skeletal abundance to nosedive to a mere 3 percent of rock volume, reflecting near-total system collapse in marine ecosystems.
Remarkably, post-extinction recovery phases revealed a resilience in oceanic life. During the Mesozoic and Cenozoic eras, marine biomass rebounded vigorously, with the rock record showing shell content climbing to over 40 percent, particularly fueled by the evolutionary success of mollusks and reef-building corals. Notably, secondary mass extinctions—such as the end-Triassic and end-Cretaceous events—caused sharp but transient drops in marine biomass that quickly rebounded. These patterns illustrate a general trend of biomass expansion, reinforcing the interconnectedness of evolutionary innovation, ecological energy utilization, and ecosystem productivity.
Crucially, the researchers addressed pivotal methodological concerns that could confound interpretations of shifting skeletal content. They rigorously tested whether observed biomass increases were artifacts of sampling biases or ecological factors like predator-prey dynamics. By stratifying data across environmental gradients such as water depth, paleolatitude, and continental configurations, the team demonstrated consistent biomass trends irrespective of these variables. This meticulous cross-validation confirms that the long-term patterns identified are genuine biological signals, rather than noise introduced by geological or sampling variability.
The evolutionary drivers underlying this biomass rise lie in the increasing complexity and specialization of marine life forms over geological time. Specialized species exploit ecological niches more effectively, enabling more efficient energy capture and nutrient cycling within marine food webs. Phytoplankton serve as primary producers, transforming solar energy into organic matter, while diverse decomposers recycle nutrients back into the system, sustaining higher trophic levels. This enhanced ecosystem efficiency translates into larger, more productive biological communities capable of sustaining greater biomass and indicative of healthy ocean systems.
While the fossil record extends this hopeful narrative over deep time, the present and near future paint a more cautionary picture. The Anthropocene epoch, defined by rapid and widespread human impact, is marked by events such as fertilizer runoff, overfishing, ocean acidification, and habitat destruction that pose severe threats to marine biodiversity. Scientists widely recognize this as a sixth mass extinction, driven by anthropogenic forces operating on a scale and pace unmatched in geological history. This contemporary loss of biodiversity carries the ominous potential to erode marine biomass in real time, with cascading effects on ocean productivity and planetary health.
The Stanford team emphasizes the critical linkage demonstrated between biodiversity and biomass, highlighting that reductions in species richness may suppress productivity over geological timescales. This insight underscores the broader implications of biodiversity conservation, as maintaining species diversity is foundational not only to ecological resilience but also to sustaining the flow of ecosystem services upon which humanity depends. As Jonathan Payne, senior author and esteemed professor at Stanford, notes, understanding these macroevolutionary relationships helps inform strategies to safeguard ecosystem function amid accelerating environmental change.
By bridging paleobiology, geology, and ecology, this research offers a transformative lens on Earth’s marine biosphere, revealing how the intertwined evolution of biomass and biodiversity has shaped ocean life through epochs of triumph and tragedy. It invites us to consider how current human actions will be recorded—and felt—across future chapters of Earth’s biological history, while reinforcing the imperative of stewardship in preserving the ocean’s ancient and vital legacy.
Subject of Research: Marine biomass and biodiversity changes across the Phanerozoic eon
Article Title: Macroevolutionary coupling of marine biomass and biodiversity across the Phanerozoic
News Publication Date: 25-Jun-2025
Web References: http://dx.doi.org/10.1016/j.cub.2025.06.006
Keywords: Marine biology, Earth sciences, Evolution, Fossils, Paleobiology, Geologic periods
