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Sunday, November 18, 2018

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A rare glimpe of sunshine on Yunaska Island. (Photo: Genoa Sullaway) A rare glimpe of sunshine on Yunaska Island. (Photo: Genoa Sullaway)

Dispatches from the Aleutians, Part 2

A team of SDSU scientists provides a first-hand account of their investigation into Pacific Ocean kelp forests.
By Genoa Sullaway

This summer, SDSU ecology professor Matthew Edwards is leading a research expedition to the Aleutian Islands, Alaska, to study its kelp forests and the wildlife within. This is the second in a series of field notes that students on the trip will be providing. The project is funded by the National Science Foundation.

Wake up. Eat. Science. Eat. Repeat.

We are on week two of our Aleutian Island cruise, and if we aren’t transiting between islands, our days are dominated by our diving schedule. We average five dives a day, ranging from 15 to 60 minutes in length. Working for that long in Bering Sea conditions (40° Fahrenheit water with swell or wind) requires a lot of warm clothing and warm food.

Why are we spending so much time underwater? Science! A lot of it. Each morning, divers from San Diego State University and the University of Alaska Fairbanks (UAF) divide up into teams, each tasked with a carefully designed experiment or survey. Divers from UAF are comparing species diversity among habitats—specifically kelp forests, transition zones, and urchin barrens—to understand how removal of the foundational dragon kelp impacts the species that live there.

Divers collect the algae and invertebrates from a one-square-meter area, multiple times within each habitat. These collections are brought back to the laboratory on board the R/V Oceanus, where they are sorted and weighed. When this is done, all algae and invertebrates are thrown back in to the ocean, unharmed.

The researchers hypothesize that habitats with kelp will host a greater number of species than habitats without kelp. Kelp is considered a "foundation species" because it supports an incredibly diverse ecosystem. Ecosystem diversity is important because species have distinct interlinked roles that facilitate a healthy ecosystem.

Divers from SDSU measure primary production in these three habitats (kelp forest, transition zone and urchin barren), meaning we measure the amount of photosynthesis, or primary production, occurring in the underwater environment. Similar to lush terrestrial rainforests, these underwater forests have high rates of primary production, which provides resources like oxygen to the surrounding environment and maintain species diversity in our coastal zones.

We measure primary production by deploying oxygen sensors in underwater tents. The tents create a closed system on the seafloor, and we study the small-scale changes in oxygen to understand what is happening on a larger scale. This standardized methodology allows us to compare photosynthesis across habitats. We hypothesized that kelp forests produce more oxygen than other habitats. So far, we have found that our hypothesis holds true. However, urchin barrens, which have little to no kelp canopies produce more oxygen then we thought, likely because the crusting pink coralline algae that survive on the bottom of the sea can take advantage of the increased sunlight and partially compensate for the lack of kelp.

Finally, a team of two divers survey "historical sites" on each island, so-called because these are sites that have been sampled repeatedly using the same methods since the 1970s. All of these surveys and experiments are replicated among islands so we can make inferences about how the underwater landscapes across the entire Aleutian archipelago have changed through time.

The Aleutians are wild and rugged. Landscapes are striking and different at each island. Often steep volcanoes reveal themselves if you are paying attention when the fog clears. You may see curious Steller sea lions (which can grow up to 15 feet long) poke their heads out of the water, a sea otter munching on a sea urchin, or hundreds of puffins flying along the cloudy seascape. If you are lucky, you may even see Orcas!

Check in next week to read about our offshore trawl surveys, shipboard experiments, and the final leg of the trip!

Dispatches from the Aleutians, Part 2
A team of SDSU scientists provides a first-hand account of their investigation into Pacific Ocean kelp forests.