Whale Poop Could Explain Ocean’s Mysterious Decline After Mass Whaling

A new study reveals that whale excrement contains a precise chemical cocktail that may have once fertilized entire ocean ecosystems, suggesting that the mass slaughter of whales in the 20th century disrupted more than just whale populations. The research, published in Communications Earth & Environment, provides new evidence for how the loss of two million great whales may have triggered cascading effects still visible in today’s oceans.

By analyzing excrement from blue and humpback whales, researchers discovered extraordinarily high levels of bioavailable iron – a critical but scarce nutrient that marine plants need to grow. The study marks the first detailed analysis of how trace metals in whale excrement interact with ocean chemistry.

“We made novel measurements of whale feces to assess how important whales are to recycling important nutrients for phytoplankton,” said Patrick Monreal, lead author and doctoral student in oceanography at the University of Washington. “Our analysis suggests that the decimation of baleen whale populations from historical whaling could have had larger biogeochemical implications for the Southern Ocean, an area crucially important to global carbon cycling.”

The findings help explain a longstanding ecological puzzle: When industrial whaling removed 90% of great whales from the Southern Ocean, their prey – tiny shrimp-like krill – unexpectedly declined instead of flourishing in their absence. Scientists now suspect that whale excrement provided essential nutrients that supported the entire food web.

The research team analyzed five samples – two from humpback whales near Antarctica and three from blue whales off California. They found iron concentrations up to 100,000 times higher than typical ocean levels, along with surprisingly high amounts of copper bound to organic molecules that rendered it non-toxic to marine life.

“We were really shocked by how much copper was in the whale poop. We initially thought, ‘oh, no, is the whale poop actually toxic?'” said senior author Randie Bundy, assistant professor of oceanography at the University of Washington. Further analysis revealed that special compounds called ligands transformed the copper into a safe, usable form.

The study identified nearly 50 previously unknown copper-binding compounds, possibly produced by bacteria in whale digestive systems. “I think animals play a larger role in chemical cycles than many experts give them credit for, especially when thinking at the ecosystem scale,” Monreal noted. “When I say animals, I really mean their gut microbiome. Based on what we see, it seems like bacteria in the whales’ guts could be important.”

The implications are profound. During peak feeding times, a single Antarctic baleen whale can consume several tons of krill daily. When they process this food, they release nutrient-rich excrement near the ocean surface, precisely where marine plants need it most. This “whale pump” of nutrients may have been crucial for maintaining the Southern Ocean’s productivity.

Calculations suggest that before industrial whaling, baleen whales in the Southern Ocean could have recycled between 35,100 and 239,000 moles of bioavailable iron annually. This volume rivals other major iron sources in the region, such as dust, ice melt, and glacial sediments.

The findings arrive as scientists grapple with how to restore damaged ocean ecosystems. While some whale populations have begun recovering, warming temperatures and expanding krill fisheries threaten this recovery. Understanding the complex relationships between whales, nutrients, and ocean productivity could prove crucial for marine conservation efforts.

The research also opens new questions about the role of animal gut bacteria in global nutrient cycles. The team’s discovery of novel copper-binding compounds suggests that whale digestive systems may be an unexplored source of molecules important for ocean chemistry.