In the cold dark depths of the North Pacific Ocean, corals and sponges create living habitat for an abundance of life—including some of Alaska’s valuable commercial fish and shellfish.
This summer, Alaska Fisheries Science Center researchers and partners will embark on three expeditions to explore deep-sea coral and sponge habitats in the Gulf of Alaska. Advanced sampling technologies like stereo cameras, ROVs and environmental DNA (eDNA) will make it possible to survey vast areas in a noninvasive and cost-effective manner. The team will discover where corals and sponges are diverse and abundant. They will also learn about coral and sponge early life stages and growth. This knowledge will fill critical information needs for ecosystem-based management of Alaska’s fisheries in a rapidly changing ocean.
“The overarching goal is to conserve and protect unique habitats,” said project lead Christina Conrath, NOAA Fisheries Alaska Fisheries Science Center. “The first step is learning where important habitats are and how important they are to supporting fish and the ecosystem. That’s what we’re doing now.”
Deep-sea Coral and Sponge Ecosystems
Corals and sponges form complex habitat for a multitude of animals. This structure offers protection, feeding opportunities, and nursery areas for commercial species like rockfish, spot prawns, and golden king crab. Some fish deposit their eggs in sponges where they are not only protected from predators, but may also benefit from the sponge’s natural antifungal and antibacterial activity.
In addition to their value as habitat, filter feeding sponges recycle waste and nutrients, which helps keep the ocean balanced and healthy. Also, some species produce chemicals of great biomedical potential.
Deep-sea corals and sponges are vulnerable to a number of threats. Unlike many species, they cannot migrate to new locations as climate change alters ocean conditions. Ocean acidification and warming may make it difficult for some species to build their skeletons or filter water. They can also be damaged by human activities like some types of commercial fishing and energy operations. These slow-growing animals, and the habitats they create, may not quickly recover from harm.
To predict and mitigate impacts of human activities and climate change on deep-sea corals and sponges, we need to know their habitat needs and basic biology.
Key Missions for 2022: Validation, Recovery, and Exploration
This summer’s research is part of the ongoing 2020–2024 Alaska Deep-Sea Coral and Sponge Initiative. The Initiative is funded by the Deep Sea Coral Research and Technology Program. This program sponsors multi-year studies that rotate among national regions. Alaska was previously on rotation in 2012–2015.
This summer’s work will build on accomplishments from the earlier expeditions, and the first 2 years of the current initiative.
The 2022 expeditions will focus on three major projects.
Validation of Coral and Sponge Distribution Modeling in the Gulf of Alaska
June 14–July 14
The Alaska seafloor is immense. Visually searching its entirety for coral and sponge is not practical or possible. To zero in on where corals and sponges are likely to be found, the Center developed predictive models.
An important accomplishment of the previous expeditions was the production of maps based on these models for the eastern Bering Sea, Aleutian Islands, and Gulf of Alaska. The maps for the Bering Sea and Aleutian Islands were validated using visual surveys.
“Now it’s the Gulf of Alaska’s turn,” Conrath said. “That’s our biggest goal this summer.”
To accomplish this goal the team will attempt to sample 300 randomly selected sites at depths from about 30 to nearly 800 meters.
At each station, the team will:
- Capture stereo camera images to measure the density and size of coral and sponge
- Record seafloor type (bedrock, boulder, sand, etc.)
- Record associations with other invertebrates and fish
- Collect water samples for eDNA analyses to compare with the visual observations of corals, sponges, and fish
- Measure water temperature and depth
The stereo camera system, developed by Center researchers, is the sampling advancement that makes this work possible. It provides the capability to survey remote, deep, often untrawlable Alaska seafloor habitats over a vast area—all in a time- and cost-effective way without causing any harm. And it enables scientists to collect a great deal of information. Kresimir Williams, Alaska Fisheries Science Center research biologist, led the development of the stereo camera system. He explains:
“Stereo imagery constructs a 3D environment; the image quality is high enough to identify species. Together these allow us to answer a lot of questions. We can see how close animals are together. We can measure heights. We can associate fish species with types of corals. The main goal is to be able to do quantitative science. With the stereo camera we can measure density—the number of animals per square meter.”
ROV-assisted Recovery of Settlement Plates to Study Coral Reproduction, Recruitment, and Growth
Because of the challenges involved in studying deep sea Alaska corals, we know little about their basic biology. This summer’s research will bring to light new information on coral reproduction, recruitment (settlement from the planktonic larval stage to non-mobile adult), growth, and development.
In 2013, natural stone settlement plates were placed on the seafloor near coral colonies at two sites. This summer, researchers will use an ROV system to retrieve four of those plates. (The remaining plates will be retrieved in subsequent years.)
“We are excited to see what has grown,” said Pam Goddard, NOAA Fisheries affiliate, Alaska Fisheries Science Center. “Measuring coral growth on the plates is an important step to understanding the impacts of climate change on cold-water corals, and understanding how these corals function in the deep sea."
At the same time, four autonomous reef monitoring structures will be placed for later retrieval. These structures have eight layers of separated plastic plates that provide plentiful surface areas and crevices. These structures are standardized to allow comparisons of recruitment among varied study sites.
The plate settlement work is part of three interrelated projects that will fill critical gaps in management information needs regarding coral and sponge reproduction, recruitment, growth, development, and impacts of climate change and ocean acidification.
Joint Canada-United States Seamount Exploration
Deep-sea coral and sponge ecosystems differ between the British Columbia continental shelf and the Alaska continental shelf. Two seamount chains in international waters may form a geological connection between these two regions. This summer, U.S. and Canadian researchers are partnering to explore these seamounts.
The team will use the same suite of tools as the validation expedition to survey 78 stations.
Expedition findings could provide insight on:
- Genetic connectivity among coral and sponge ecosystems from Washington to Alaska
- Impacts of climate change
- Location of international vulnerable marine habitats
- Historical fisheries impacts and recovery rates
- Linkages between fished species and deep-sea corals and sponges
Benefits Now and For the Future
Alaska’s productive fisheries depend on healthy, well-managed ecosystems.
Discoveries made during this summer’s research will help keep them healthy. They will benefit fisheries and fishing communities now and into the future.
Mapping deep-sea coral and sponge habitat will help pinpoint the most important areas to protect, and avoid wide-sweeping closures to fishing.
Completing the surveys will help researchers learn how to better assess untrawlable habitats and how important they are to fish.
It will inform sustainable fisheries management and help fisheries and fishing communities prepare for the future.
“If we want to understand how environmental change will impact fish, we need to understand how it is going to affect their habitat,” Conrath said.
Alaska Deep-Sea Coral and Sponge Initiative 2020-2024 research is a collaborative effort between NOAA Fisheries Alaska Fisheries Science Center (Christina Conrath, Pat Malecha, Jerry Hoff, Pam Goddard, Vanessa Lowe, Kresimir Williams, Rick Towler), Alaska Department of Fish and Game (RV Solstice and ROV), Survey Vessels of Alaska (RV Woldstad), Fisheries and Oceans Canada (Chris Rooper and CCGS John P. Tully), and Tjärnö Marine Laboratory, University of Gothenburg (Rhian Waller).