Monday, December 11, 2017

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An inflatable dive boat is craned into the water from the R/V Oceanus. An inflatable dive boat is craned into the water from the R/V Oceanus.
 


Dispatches from the Aleutians, Part 3

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

“As I back-rolled off the boat, the dense fog disappeared from my view and an expansive underwater world opened up.”

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 third and final installment in a series of field notes that students on the trip will be providing (Part 1, Part 2). The project is funded by the National Science Foundation.

As we sped away on our inflatable boat, the 177-foot R/V Oceanus immediately disappeared into the dense fog. We relied on GPS to guide us to our dive site off Ogliuga Island. The small arrow on the screen pointed the way, as we kept our eyes peeled for shallow rocks that could destroy our boat propeller and kelp that could get caught in the engine. Working in a remote location like the Aleutians means you have to prepare for the unexpected.

When we got to our first dive site, we donned our gear in a matter of minutes. As I back-rolled off the boat, the dense fog disappeared from my view and an expansive underwater world opened up. The sea swell was minimized by a kelp cover, leaving the subtidal world relatively calm.

Kelp forests support life in the shallow nearshore waters of the Aleutian Archipelago. Through photosynthesis, kelp forests act like massive lungs, drawing down carbon dioxide and supplying oxygen to the marine environment. They also provide habitat and food for a diverse array of species. However, we know less about how kelp forests indirectly support life in the deeper offshore environment.

Organic detritus, or plant matter that has died and been washed offshore, can be found in these deeper environments. The question is: Is it there by chance, or does this nutrient-rich detritus contribute to  life at ocean depths?

Another component of our Aleutian research is to understand how nearshore kelp forests may support life off the shores of these small islands. To do this, we conduct trawls at each island. A trawl is a fishing method that has been adapted to conduct deep sea surveys. It involves briefly dragging a net along the ocean floor to survey organisms that live there. An ideal trawl location for this trip has a relatively flat bottom and is about 90 meters deep. Trawl locations are picked using nautical charts, but sometimes we hit rocks that manage to damage the trawl bar (so far, we have bent two). During our last trawl of the trip, we accidentally hauled up a 400-pound lava rock.

Once a haul comes up to the boat deck, scientists quickly get the animals into tubs of water and move them inside so they can be sorted, weighed, and then returned to the ocean. These surveys give us a picture of the types of communities that live in the deep-water environment. We also collect small samples of muscle tissue, which can tell us if the organisms making up these communities depend on carbon derived from kelp or from another source, like plankton. This allows us to link the nearshore kelp forests (or, on some islands, lack thereof) to the deep-sea environment.

To cram the maximum amount of science into our three-week trip, scientists from Kunsan University in South Korea and SDSU conducted shipboard algae and invertebrate incubation experiments. The goal of these incubations is to estimate how much oxygen is produced by an individual alga or how much oxygen is consumed by an invertebrate, like a sea urchin or sea star. These will help us understand photosynthesis from individual species at a fine scale, and allow us to relate these puzzle pieces to the larger community’s oxygen production measurements. In total, we conducted 150 incubations that included 26 different algae species.

During these three grueling weeks on the R/V Oceanus, we visited seven islands, spent 261 cumulative hours underwater, with 11 divers conducting 457 total dives. We counted more than 211 species and did 54 benthic tent deployments to measure oxygen production. These numbers represent almost a year’s worth of research crammed into 19 days.

They also represent the relentless spirit of adventure and exploration at the heart of this research. As scientists, we set out to explore and understand the natural world. The next step in this research is to analyze the data and see what kind of story it tells about how the loss, and in some places recovery, of kelp forests across the Aleutians has impacted the communities that depend on the kelp. We hope our findings can be shared with others and enhance the greater societal understanding of how the oceans operate and support valuable life.

Thank you for tuning in!

 
Dispatches from the Aleutians, Part 3
A team of SDSU scientists provides a first-hand account of their investigation into Pacific Ocean kelp forests.