Climate vulnerability assessment for deep-sea coral ecosystems in Channel Islands National Marine Sanctuary

Overview

Principal Investigators:

There is a compelling need to understand the effects of changing ocean climate on deep-sea corals. Deep-sea corals are long-lived animals. Like trees, they grow to be very old and they are sessile, or fixed in place. Their branches provide substrate and refuge to many associated species. So, any natural or anthropogenic threats to deep-sea corals can bring changes to this ecosystem.  Warming oceans threaten deep water communities because they are stenothermal, adapted to stable cold-water conditions. Acidified oceans may also be a threat, because stony coral skeletons are comprised of aragonite, a form of calcium carbonate that dissolves under acidified conditions. Scientific studies will help to understand the resilience of deep water species to a changing climate.

The goals of this project are: 1) to use the US Pacific coast region as a natural laboratory to understand the effects of ocean acidification on the deep water stony coral, Lophelia pertusa; 2) to assess the depth and intensity of warm water anomalies and discern their impacts on deep water gorgonian aggregations, if any 3) to contribute to a climate vulnerability assessment of sanctuary resources in support of the CINMS Condition Report; and 4) to educate the local community about ocean warming and ocean acidification.

A series of research expeditions took place between 2014 and 2016 in support of these goals, including NOAA ship Bell M. Shimada (early spring, 2015), EV Nautilus (late summer 2016), and R/V Shearwater (late summer 2014, 2015 and 2016). Each of these expeditions was co-sponsored by NOAA, each had an ROV platform for deep-water surveys, and each collected water and coral samples, as well as video transect and temperature logger data. The Climate Change Vulnerability Assessment described here was one of several projects conducted aboard the multi-disciplinary expeditions, collectively referred to as the ‘Patterns in Deep Sea Corals’ expeditions. 

Summary to Date

A project page was produced in 2014 for “Vulnerability of Deep-Sea Coral Ecosystems to Ocean Acidification”, introducing the pilot project in CINMS to collect live samples to characterize the effects of ocean acidification on deep-sea Lophelia corals in Pacific waters. The proposal followed two years of preliminary research on the distribution and water chemistry of Lophelia in Southern California Bight (Wickes, 2014). Fieldwork in 2015 obtained live corals for husbandry and water samples for aragonite saturation.  At that time, the research team also began to investigate warm water anomalies associated with the 2015-2016 El Niño event using in-situ data loggers top record temperatures from 20 - 200 m depth. Health assessments for gorgonian aggregations potentially impacted by these anomalies were incorporated in 2015 and 2016. Live coral experiments were concluded in 2017, and published in 2019.

A large number of publications and reports were produced from this work. The first was a front-page story in the Science section of the Los Angeles Times in April 2015 that described the work aboard NOAA ship Bell M. Shimada. Two additional articles in Oceanography described work in 2016 aboard EV Nautilus (NA074; (Coleman et al., 2017; Raineault et al., 2017). Later, NOAA technical memoranda were produced. These outlined the results of NOAA’s mapping and ROV surveys (Caldow et al. 2016), showed images of coral samples, and plots of in-situ temperature data for a period of ~8 months during 2015-2016 ENSO event (Etnoyer et al. 2017). A series of peer-reviewed articles were published on the effects of ocean acidification of Lophelia corals (Gomez et al. 2018; Hennige et al. in prep) and the effects of warming on octocorals (Gugliotti et al. 2019)

Research on warm water anomalies in the Southern California bight and the sampling of live gorgonian octocorals from the Channel Islands was the subject of an article called “Nautilus Samples 2016: New Techniques and Partnerships” in Oceanography Magazine (Raineault et al., 2017). Results of experiments working with these live corals were published in the Journal of Experimental Marine Biology and Ecology (Gugliotti et al., 2019).

Monitoring Trends

Discussion

National Marine Sanctuaries in the Pacific Ocean along the US West Coast are a ‘natural laboratory’ to study the effects of extreme conditions of deep-sea corals and sponges. They offer a window into forecasted ‘future ocean’ conditions in which scientists can evaluate the effects of climate change on deep-sea corals in this and other parts of the world, such as the Atlantic Ocean. Deep scleractinian corals along the US West Coast are naturally subject to relatively low aragonite saturation and dissolved oxygen levels relative to Atlantic basins. The corals are also subject to intense, periodic fluctuations in water temperature associated with El Nino/La Nina Southern Oscillation.

Lophelia pertusa is an aragonitic scleractinian coral growing in naturally low aragonite saturation states in Southern California. Several colonies were collected alive using a remotely operated vehicle (ROV), and maintained in cold water aquaria for experimental exposures to low pH.  The information supports assessment of the vulnerability of these corals to ocean acidification. Further work in needed to verify the genetic identity of California’s Lophelia; and to compare the health, extent, and skeletal structure of these corals to other colonies from the Atlantic and Gulf of Mexico.

The other component of this study deployed temperature loggers in shallow and deep waters, and collected live samples of the octocorals Adelogorgia and Leptogorgia. Live samples are maintained at the NCCOS laboratory in Charleston SC, in order to understand the threat of warm-water events to deep-water corals. The results of this study indicated that deep-water corals are frequently exposed to warm-water anomalies. Projections that warm-water events will become more frequent and intense indicate that the thermal limits of gorgonian octocorals in the Channel Islands will likely be reached and exceeded in the future. This work helps to establish a baseline for coral health to assess the effects of climate change in the deep sea.

Ocean warming and acidification induced by climate change could affect the distribution of deep water corals in the Channel Islands. Ocean acidification (i.e. decrease in pH) drives the upward movement of the aragonite saturation horizon (ASH) and creates unfavorable conditions particularly for deep scleractinian corals like L. pertusa. Populations of L. pertusa in the Southern California bight currently grow in acidified conditions despite having a shallow distribution (~90-300 m; Gomez et al., 2018). Shallow populations of deep water corals could further be threatened by warm-water events that are penetrating deeper in response to climate change (Gugliotti et al., 2019). Together, ocean warming and acidification could create a very narrow depth range with favorable conditions for deep water coral growth in Southern California.

The ROV surveys conducted by NOAA and partners supported deep-water climate change and impact/threat assessment missions related to deep-sea coral and sponge habitats in US West Coast Sanctuaries in Channel Islands. This project was a multiyear, cross-line office partnership between NCCOS Marine Spatial Ecology division, the NOS Office of National Marine Sanctuaries (ONMS) and NOAA Deep-Sea Coral Research and Technology Program (DSCRTP). The partnership combined NCCOS’s core expertise in deep-sea corals, climate change, habitat classification, and geospatial analysis with ONMS field operations and local knowledge to address key information needs related to the sustainable management of essential fish habitat.

Next Steps:

Study Parameters

Study Methods

ROV operations

The research used two different ships for visual surveys and biological sampling - the Beagle ROV from Marine Applied Research and Exploration (MARE) was deployed from RV Shearwater and Hercules ROV from Ocean Exploration Trust was deployed from EV Nautilus.  The ROV collects high-resolution still and video image data from on-bottom to off-bottom. During seafloor survey, the ROV transits at an altitude of ~1 m off the bottom and a speed over ground of ~0.50 knots for a period of 5-15 minutes for each transect, with the video and still cameras maintaining a wide and fixed frame.  Video is collected continuously. Still images are collected periodically, every five seconds. The still images are utilized for detailed species or genus level identifications and to access health and condition of corals and sponges. The video is used for estimates of abundance over a known survey area.

Temperature Loggers

Two types of temperature loggers are utilized for this study.  Star-Oddi titanium data loggers for depths up to 1000 m and OnSet Hobo temperature loggers for depths up to 300 m.  Loggers are attached to a block of syntactic foam via nylon rope and anchored with a 4 lb dive weight. Loggers record temperature every 5 to 10 minutes depending on available memory based on type of logger.  Loggers are deployed at sites near known coral aggregations using the ROV.

Water Chemistry Collection

Water samples were collected using SBE 19plus CTDs and niskin rosettes from Valentine lab at UC Santa Barbara, NOAA SWFSC in Santa Cruz, and NOSS ship Bell Shimada. The instruments were deployed over the side, near or adjacent to coral aggregations. Two niskin bottles were fired at 30, 60, 100, 200, 300, and 400 meters depth for the purposes of obtaining duplicate pH, DIC, and TA values. These values are used to derive water column profiles of aragonite saturation

Coral and Sponge Specimen Collection

Corals were collected from San Miguel, Santa Cruz, and Anacapa Islands. Surveys focused on hard-bottom targets between 50-600 meters depth. The use of an ROV with a manipulator arm and a sample basket enables collections of small colonies, with the least impact compared to dredge or trawl methods

Biological sampling targets included gorgonian corals (Eugorgia rubens, Adelogorgia phyllosclera, and Acanthogorgia sp.) and the scleractinian corals (Lophelia pertusa). Gorgonian samples were used to assess vulnerability to warming. Scleractinian corals were used to assess vulnerability to ocean acidification.

Biologists on board were able to maintain Lophelia pertusa coral alive in small aquaria aboard the vessel. Samples were shipped to NOAA NCCOS in Charleston for experimentation and analysis. Lophelia samples were transferred to Temple University for aquarium study by Dr. Erik Cordes and his students. Acanthogorgia samples were transferred to Keck-Claremont, Temple University, and Scripps Aquarium. Acanthogorgia, Eugorgia and Adelogorgia samples were maintained alive at NCCOS in Charleston for study by graduate students from Grice Marine Lab at the College of Charleston. Adelogorgia was hardy and plentiful, and the focus of study.

Figures & Images

Deep-sea scleractinian coral Lophelia pertusa with a bubblegum octocoral (in red, Paragorgia sp.) at 300 meters depth on Piggy Bank in Southern California’s Channel Islands National Marine Sanctuary.  Image credit: NOAA and Marine Applied Research and Exploration (MARE).


Live colonies of the orange-colored octocoral Adelogorgia phyllosclera with small rockfish in the background. Image collected near 70 m depth south of Santa Rosa Island in Channel Islands National Marine Sanctuary, California. Image credit: NOAA and Marine Applied Research and Exploration (MARE).