The beneficial impact of a chemical released by small marine creatures on whales

Dimethyl sulfide (DMS) is a chemical compound released when tiny marine crustaceans called zooplankton graze on microscopic plants known as phytoplankton. Phytoplankton produce compounds including dimethylsulfoniopropionate (DMSP) to survive in the seawater. The water-soluble DMSP uses sulfur from the surrounding marine environment to support regulating the balance of saline water within and around the phytoplankton cells.

DMSP-aided regulation has been shown to protect these cells against changes in environmental conditions such as salinity, light, nutrients, and oxygen. This ultimately contributes to phytoplankton’s ability to survive in changing environments, giving them niche plasticity.

When phytoplankton get eaten by zooplankton, the DMSP they store releases into the water and is broken down into DMS by bacteria. The resulting chemical aroma lingers in the ocean and atmosphere, where it can act as a foraging signal attracting other predators, including North Atlantic right whales, searching for zooplankton to eat.

Using DMS to track North Atlantic right whales

While predictive methods like species distribution and habitat suitability models have been used to map whale presence, predictive prey models using DMS are relatively new. Previous studies have demonstrated that DMS concentrations are spatially correlated to the biomass of zooplankton—a crucial food source for the North Atlantic right whale and other baleen whales. Given this correlation, a 2021 study demonstrated the potential to predict the presence of baleen whales based on these concentrations.

Over the last three years, Stellwagen Bank National Marine Sanctuary, Woods Hole Oceanographic Institution, and IFAW collaborated on research showing that North Atlantic right whales were showing up in areas with the highest DMS concentrations, and subsequently locating zooplankton. IFAW is working alongside these groups to continue researching DMS with the aim of identifying potential connections between DMS and North Atlantic right whale aggregations.

In 2023, researchers boarded the Song of the Whale, a non-invasive research vessel monitoring mother whales and their calves, to collect data on their behavior, health, habitat, and threats. Researchers followed their migratory path from their calving grounds in Florida to the Gulf of Maine, during which they investigated DMS-right whale rates of merging in Cape Cod.

One key question that has supported this study is: how can North Atlantic right whales use the aroma from DMS to pinpoint the microscopic zooplankton? It turns out they have a unique nasal structure drawing them directly to these small organisms.

IFAW and other groups are testing one hypothesis outlined in a 2024 study to support a claim that right whales may have an olfactory advantage when it comes to tracking and locating food. The study found that whales like North Atlantic right whales, with a preference for zooplankton, have nostrils (nares) with wider spacing than other whales. Just as stereo-vision can help animals locate prey at specific distances and owls’ asymmetrical ears can pinpoint certain sounds through stereo-hearing, these widely spaced nares allow for a greater ability to pinpoint prey using smell—also known as stereo-olfaction. These whales know exactly what food they want and are equipped with the tools to find it!