How can whale fecal matter— i.e., poop —help us to understand ocean ecosystems?
“A little to the left!”
A bright red zodiac moves slowly through the ocean below the gentle buzz of a small drone that’s circling above. It’s 2020 and a calm day in Chatham Strait, a deep marine fjord that separates several large islands within Southeast Alaska’s Alexander Archipelago. A drone operator, standing in the gently rocking boat, is staring at a small screen displaying a video feed of a reddish-orange plume left behind by a humpback whale that has just dived below the surface.
As the boat approaches the area where the whale dove, the four people aboard spring into action. The captain navigates the boat towards the plume; as it gets closer, another crew member unscrews a small plastic bottle and leans over the side to scoop up the floating material. A third holds tightly to the bottle-wielding person’s ankles to keep her from falling overboard. Meanwhile, the final crew member scans through a series of photos to see if they captured an image of the whale’s fluke as it dove.
The AWF Research crew aboard their zodiac, Barbara Belle.
Dana Bloch, a Graduate Fellow working with the Alaska Whale Foundation (AWF), has just collected her first sample of humpback whale fecal matter, i.e, whale poop. Bloch is a student at the University of Alaska Fairbanks (UAF) and current Graduate Fellow with AWF. Since 2021, she has been studying the role that humpback whale poop plays in nutrient cycling in Southeast Alaska.
“I study whale poop, and while I am used to talking about it, and find it interesting and scientific, I forget that most people feel funny talking so openly about poop”, says Bloch. “I have had many conversations with adults, and respected scientists, who can't help but giggle for a minute when they realize we are going to talk in depth about the nutrients in humpback poop. Kids often have a good laugh about it, too, but they also have really interesting questions that spark my curiosity and get my brain turning.”
Bloch’s work is part of a broader effort by researchers to understand the ways in which whales contribute to the health of ocean ecosystems. In many parts of the ocean, nutrients, such as nitrogen and phosphate, are in short supply. Phytoplankton, the microscopic ‘plants’ of the sea (technically, they’re algal cells), require these nutrients to grow, so in areas where nutrients are limited, so too is the abundance of phytoplankton. Because phytoplankton are the base of virtually all marine food webs and are crucial to removing planetary warming-inducing CO2 from the atmosphere, nutrient limitations can have far-reaching impacts on ocean and planetary health.
Bloch collects a sample by dragging a zooplankton net through a whale fecal plume.
Whales are thought to contribute to ocean nutrient cycling through several mechanisms: they physically mix nutrients as they swim up and down through different layers of the ocean; they carry massive amounts of nutrients and carbon to the seafloor when, upon dying, they sink; and through their poop, they fertilize the ocean. This latter process, where whales feed in deep waters and transport nutrients upwards by releasing nutrient rich fecal matter at the ocean’s sunlit surface where phytoplankton grow, is referred to as the ‘whale pump’.1,2,3
Empirical data demonstrating the whale pump’s contribution to regional nutrient cycling is limited, and no such data exist for the North Pacific. Yet, as our planet warms - which leads to ‘vertical stratification’ of the water column and ultimately reduces the amount of nutrients mixed into the ocean’s surface - the whale pump may become increasingly important. It was this concern that led Bloch to begin her work.
Growing up in coastal Maine, Bloch was drawn to whales, especially humpbacks, at an early age. Her fascination with their life histories and behaviors only increased as she went through highschool and college. Eventually she realized her interests resided as much in understanding how whales and ocean ecosystems impact one another as they did in the mystery of whales’ underwater lives.
Bloch collecting water samples as part of her research in Southeast Alaska.
“I love remembering, when looking out at the ocean, that there are gigantic mammals swimming around living their lives all the time! It is so easy to be mesmerized when we have the rare, fortunate opportunity to encounter whales in the wild, but it feels a bit like a special secret to know they are out there right now”
While taking oceanography and earth science courses in college, Bloch began to learn how whales, especially large whales like humpbacks, can impact carbon and nutrient cycling in the ocean and, in doing so, contribute to ocean health.
“This was a light bulb moment for me.” Bloch began to wonder if she could combine her interests in whales and ocean conservation and chart out a graduate research path.
Through a lot of work and patience, the answer was “yes”.
Upon completing her undergraduate degree, Bloch began an internship with AWF, which allowed her to gain hands-on experience in whale research. She returned for a second year in 2019, this time expressing her interest in developing a project to study whales and nutrient cycling to Dr. Andy Szabo, the Executive Director and lead researcher at AWF. With Dr. Szabo’s support, she spent the next two years developing a research project and reaching out to l academic advisors. Eventually, she connected with oceanographers Drs. Heidi Pearson, Will Burt and Tyler Hennon at University of Alaska Southeast (UAS) and
University of Alaska Fairbanks (UAF) and gained their support for her project. With all the pieces in place, Bloch was set to begin a formal Master's program at UAF in 2021 that would allow her to continue her work with whales in Southeast Alaska.
Southeast Alaska is an ideal - and important - place to conduct research on whales, nutrient cycling and ocean health. An estimated 1,500 humpbacks visit the region every summer 5. There, they feed alongside several commercially and culturally important fisheries. Understanding the mechanisms that drive nutrient cycling and production at the base of the food chain is essential for monitoring the sustainability of these fisheries. If humpback whales stimulate increased phytoplankton growth, as Dana predicts, the positive bottom-up effects could have far reaching implications for not only the fisheries, but the entire ecosystem.
Bloch collects water samples and deploys probes that measure salinity, temperature, and chlorophyll concentrations at 120 whale survey sites as part of AWF's Ocean Health Program.
Bloch conducts her work as part of AWF’s ongoing Ocean Health Program. As part of this program, the AWF team visits some 120 survey sites each month where they collect whale abundance, distribution and health data. Whenever they visit one of these locations, Bloch deploys probes that measure ocean salinity, temperature and chlorophyll concentrations - the latter a proxy for phytoplankton biomass - from the surface to a depth of ~50m. She also collects water samples to measure nutrient concentrations. These data provide a detailed picture of the water column’s physical and chemical structure throughout the study region.
AWF survey sites in September 2022.
She augments these data with similar data provided to her by local fishermen through a collaboration with the Alaska Trollers Association, a regional association of commercial fishing boats. This partnership is proving to be a great way to include regional stakeholders in the process.
Bloch uses these oceanographic data to track how oceanographic conditions change within and between years. They also form the basis for quantifying the amount of nutrients humpback whale poop contributes to the region.
Of course, for that she also needs to collect poop, and this can be hard to do.
“Fecal plumes can be difficult to spot from the boat, but we usually have a drone in the air [when collecting whale data], and often the drone pilot will spot the poop first.”
Despite the added help from the drone pilot, the team still rarely spots poop. In her three years, Bloch has only collected twenty samples, so when the team does spot poop she tries to capture as much as possible However, not all poop is the same - something that Bloch did not anticipate when she began her study - and this can impact her success.
Bloch collecting a sample with a plastic bottle.
“When humpbacks are feeding on krill, their fecal matter is bright reddish orange and remains in soft clumps at the surface, making it relatively easy to collect with a net. After whales have been feeding on fish, their fecal plumes are brown and watery. This makes them really difficult to spot from the boat (much easier with a drone), and challenging to know that I have actually collected a fecal sample, after dragging my net through the plume.”
These differences not only affect how easily Bloch can collect samples, they likely reflect differences in the poop’s nutrient concentrations as well, something that Bloch is interested to investigate further.
Water samples are transported to a lab, where Bloch is conducting incubation experiments to determine how much of the whale poop is 'bioavailable', or available for phytoplankton to use during photosynthesis.
Once Bloch has collected a sample, she stores it in a plastic bottle and brings it back to the lab where it is frozen until it can be analyzed for its nutrient concentration.
Bloch is also conducting incubation experiments to determine how much of the whale poop is ‘bioavailable’ - that is, available for the phytoplankton to use during photosynthesis. To do so, she grows phytoplankton in the lab - some with nutrients from whale poop and others without - and compares the rate at which they grow under the different conditions. She hopes her incubation results will provide further insight into how phytoplankton respond to whale poop in the wild.
Although Bloch has more data to collect, her preliminary analyses are already revealing that phosphate and ammonium concentrations in whale poop are significantly higher than in the surrounding seawater. Phytoplankton need these nutrients, so humpback whale fecal plumes may be a welcome influx of nutrients in areas where nutrient concentrations are low. Her work is also generating extensive baseline nutrient, chlorophyll, temperature, and salinity data for Southeast Alaska. These important oceanographic data are lacking in the region and Bloch’s data are beginning to provide insight into how Alaska’s marine ecosystems are being impacted by climate change.
Yet, the overarching questions that inspired Bloch to begin this study remain.
“Humpback whales clearly interact with their environment”, says Bloch, “but the actual connections between these animals and their oceanographic environment are still muddy.
Do whales provide meaningful nutrient cycling services in the local environment? How do oceanographic patterns, such as warming waters or increased freshwater inputs, affect humpback whale health? These are the questions that motivate Bloch to devote so much of her time to studying whales in Southeast Alaska.
However, it is truly a labor of love.
“I know I am just really lucky to be able to investigate a topic I find intellectually fascinating, while also spending my summers in the Tongass National Forest and cruising all over the inside waters, hanging out with humpback whales.”
Southeast Alaska is a prime, and beautiful, location for humpback whale research.
Literature Cited
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2. Lavery, T. J., B. Roudnew, J. Seymour, J. G. Mitchell, V. Smetacek, S. Nicol. 2014. Whales sustain fisheries: Blue whales stimulate primary production in the Southern Ocean. Marine Mammal Science 30: 888-904.
3. Roman, J., J. Nevins, M. Altabet, H. Koopman, J. McCarthy. 2016. Endangered right whales enhance primary productivity in the Bay of Fundy. PLoS ONE 11: 1-14.
4. Behrenfeld, M. J., R. T. O’Malley, E. S. Boss, T. K Westberry, J. R. Graff, K. H. Halsey, A. J. Milligan, D. A. Siegel, M. B. Brown. 2015. Revaluating ocean warming impacts on global phytoplankton. Nature Climate Change 26: 1-8.
5. Hendrix, A. N., J. Straley, C. M. Gabriele, S. M. Gende. 2012. Bayesian estimation of humpback whale (Mgaptera novaeangliae) population abundance and movement patterns in southeastern Alaska. Canadian Journal of Fisheries and Aquatic Sciences 69: 1783-1797.
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