Seeing jellies in a new light

To better understand their research, I joined the Sutherland Lab from the University of Oregon, and their collaborators from Oregon State University and Portland State University, as they lived and worked at sea to study the base of the marine food web – plankton.

While the research on, and dialogue around marine ecosystems has been focused on organisms that are commercially viable or more obviously captivating, healthy planktonic communities are essential to the survival of the entire marine food web. Understanding this often-forgotten group of organisms has links to the food on your dinner plate and the commercial fishing in Oregon that is vital to our local economies.

Despite their importance, few people get the chance to learn about and observe plankton in the wild. Fortunately, I had the opportunity to see how marine research operates, why zooplankton are important, and what makes some plankton more captivating than you might realize, such as masses of delicate and eye-catching purple jellies pitching back and forth in glass dishes.

Even with my background in marine biology, I had a couple questions before we even left Newport’s Yaquina Bay. What exactly are plankton? Plankton refers to any living thing that is found drifting in the ocean, both plants, known as phytoplankton, and animals, known as zooplankton. Do zooplankton sleep? Not really, but they do migrate up to the surface to feed at night and return to depth during the day to avoid predators. And how diverse are zooplankton? Zooplankton range in size and classifications from tiny fish larvae to large jellyfish, but the Sutherland Lab is particularly interested in jelly-like, or gelatinous zooplankton, as this group has been historically understudied.

This lack of research can be attributed to a few things, one being the difficulties associated with sampling these watery fragile animals. In spite of this challenge, the Sutherland Lab is among those who are stepping up to study them.

Usually, when jellies come up in surveying trawls, they are mangled and beyond the identification abilities of most researchers and almost always immediately disregarded or even thrown back to sea. Zooplankton, mangled or intact, can also be quite the taxonomic challenge for non-zooplankton specialists, so it’s up to the experts, who have the tools to appreciate and study the hidden world of these creatures, to expand upon our existing knowledge.

As a curious but plankton-illiterate individual, I expected that fully appreciating or understanding plankton would be difficult for those outside the field. However, when given the time to see, interact with and learn about this vitally important group of organisms, I realized how easy it could be to become mesmerized by their gentle pulsing movements or fascinated in how different species reacted to light or my tweezers. But before I could explore the world of zooplankton, we had to collect these fragile animals.

Fortunately, there is equipment especially designed to sample plankton populations, like the MOCNESS net system. The gentle drag of the ship slowly pushes plankton through the nets’ small mesh size to sample without destroying the gelatinous bodies of the jellies. A ring net, aptly named for its ring-shaped opening, is also deployed to collect even smaller zooplankton.

On those mornings that I was running late, my saving grace was that sampling can be described as a “hurry up and wait” kind of process on the Langseth. When MOCNESS was sent over the side of the ship, it took around 30 minutes to reach the sea floor and return to the ship’s deck. Then there was a burst of action as samples were hauled into the lab for processing. A net’s contents were poured into clear glass casserole dishes with lights housed below, illuminating the collection of organisms as scientists crowded around to point out interesting specimens worthy of being photographed or bountiful enough to be sent for elemental analysis. It is within these casserole dishes that I began to see the tiny world of gelatinous zooplankton.

Gelatinous zooplankton come in a range of shapes, sizes and behaviors. Some are round and flat and look like ornate or fine china. Others are long and skinny with many leg-like protrusions, which allow them to swim incredibly fast. Among all these unique animals, there was one group that captured the attention of the entire science party and crew.

Most zooplankton are translucent, with some tan or yellow organs, but Doliolids stand out due to their colorful purple banding. A single barrel-shaped Doliolid doesn’t have enough pigment to really be that interesting, but in mass aggregations of thousands of individuals, they produce a vibrant plum color.

Doliolids weren’t collected at every site, but they could consistently be found at sites over 50 miles offshore. Where they were found, they were the most abundant gelatinous zooplankton, and their purple hue indicated their abundance in the ring net long before it was poured into our dishes.

Despite their eye-catching appearance, Doliolids aren’t well known by most marine scientists or general audiences. While they haven’t been extensively studied, limited, existing literature suggests that warming sea temperatures will promote Doliolid populations to bloom due to the increase in their food source, phytoplankton.

Understanding how different conditions may impact zooplankton composition is central to the work being done by the Sutherland Lab. All sampling was done in combination with an instrument that collects information on the water’s salinity and temperature at different depths. This helps researchers see patterns in the distribution of specific zooplankton, and while some trends are noticed during sampling, like where Doliolids can be found, most of the work is done back on land.

After two weeks at sea, the science party was eager to get back to their families and also into the lab to start processing the data collected from all 28 sites sampled. Processing will take a couple years, and the sampling isn’t done there. This winter, the Sutherland Lab will again be out at sea to introduce another factor, seasonality, to their research. By overlaying ocean conditions and seasonality onto sampling data, the lab hopes to create predictive models of zooplankton composition in response to climate change.

While climate change continues to impact our marine ecosystems, the types of organisms you find washed up on our beaches will likely change. Most people who walk along beaches will usually find an assortment of jellies, like pacific sea nettles or comb jellies, but Doliolids aren’t often found washed ashore. When Doliolids do find their way to land, it is in masses.

As these blooms become more common, beachgoers may start to see more of these purpled-banded, barrel-shaped organisms, something that previously seemed unattainable unless you found yourself abroad a ship collecting zooplankton. While these purple jellies are fascinating to observe, these blooms are also a cue to what is happening in the environment. There are changes occurring to our marine ecosystems, and this is one obvious indication of that.

The Sutherland Lab’s goal of creating zooplankton composition models will take a couple years, and our understanding of how increasing Doliolid populations may affect the larger food web will take even longer. For now, next time they start to wash up on Oregon beaches, take some time to investigate their tiny world and appreciate gelatinous zooplankton at their most colorful. I know I will be.

A website has been created that includes additional images as well as audio files about this research excursion. Find it online at: https://www.sutherlandlab.org/spectra