A Dungeness crab, or Cancer magister, sits on kelp.Jerry Kirkhart/Flickr
New research on the Pacific Northwest portion of the Dungeness crab fishery, which spans the West Coast of the U.S. and Canada, projects how this crustacean will fare under climate change.
Results show that by the end of this century, lower-oxygen water will pose the biggest threat. And while these crabs start as tiny, free-floating larvae, it’s the sharp-clawed adults that will be most vulnerable, specifically to lower-oxygen coastal waters in summer.
The open-access study from researchers at the University of Washington, the University of Connecticut and the National Oceanic and Atmospheric Administration will be in the December issue of AGU Advances, a journal of the American Geophysical Union.
“Including all life stages allowed us to identify a critical life stage, and thus make a management recommendation,” said co-author Samantha Siedlecki at the University of Connecticut, who began the study while at the UW. “Looking seasonally, instead of annually, gives different — and more severe — vulnerability estimates.”
Dungeness crab is the largest single-species fishery in the Northwestern U.S. Washington’s Dungeness Crab Festival takes place in October near the Dungeness Cove that gives the species its name, and the crustacean is a favorite of Pacific Northwest holiday meals and in traditional diets. The study was designed in consultation with the Hoh, Makah, Quileute and Quinault Indian Nation tribes, whose members harvest, study and eat Dungeness crab on Washington’s Olympic Peninsula.
The researchers used a detailed computer model of ocean conditions to simulate the shifting properties of the water the crabs inhabit. Using a scenario of high carbon emissions through 2100, the model looks at how heat-trapping gases in the atmosphere will make the ocean warmer, carbon dioxide transferred from the air will make the surface waters more acidic, and warmer water will hold less dissolved oxygen.
Previous research has shown that the Dungeness crab is vulnerable to climate change. Those studies focused on changes in ocean pH, while the new paper includes multiple ocean properties and uses a model that is more detailed in space and time.
Time and place are both important. Crabs mate in spring and females produce eggs in late fall. Eggs begin to hatch in January and release larvae, which float in the offshore currents while growing, shedding and regrowing their shells five times. In summer the fully developed larvae come back closer to shore and molt, becoming juvenile crabs that scamper on the ocean floor.
Dungeness crabs have a complex lifecycle, that involves larvae floating freely in the currents in the winter and spring months. Juveniles can reproduce after about 2 years, and adult females have a lifespan of 8-10 years. The study focused on the population colored blue on the map.Berger et al./AGU Advances
The authors used an ocean model to study the consequences of climate stressors at different times throughout the Dungeness crab’s life stages — from eggs, to larvae, to juveniles, to adults.
“We found that for all three stressors there will be increased population-level vulnerability, and the most severe is to low oxygen levels,” said first author Halle Berger, a doctoral student at the University of Connecticut. “Low-oxygen events happen during the coastal upwelling season in spring and summer, which impacts the adults, whereas ocean acidification manifests more year-round in the future, impacting all life stages but less severely.”
Lab studies of Dungeness crab combined with model results suggest that the most severe effects will be lower dissolved oxygen along the coastal seafloor in summer, harming the adults. This is unlike other species, such as shellfish, which are thought to be most vulnerable in the larval stage.
Like other animals, crabs breathe oxygen. Warmer water holds less gas, so even if marine life can handle the higher temperature and acidity, the drop in oxygen may lower the chance for survival.
These maps show where Dungeness crabs are most vulnerable in summer, now and in the future. On the left, adult crabs already experience low pH (blue) and a combination of low pH and low oxygen (green) across most of their range. The second panel, from an ocean model, shows the green area representing dual threats will expand by 2100. The panels on the right show the risks to free-floating larvae. In the third panel, some larvae already experience low pH (blue) or high temperatures (red). In the future, both threats will be present throughout the range, but the study suggests this will be less harmful than the changes closer to shore.Berger et al./AGU Advances
“The value of this down-scaled model is that it can help tribes and state agencies to focus their efforts in both space and time,” said co-author Jan Newton, an oceanographer at the UW Applied Physics Laboratory and co-director of the Washington Ocean Acidification Center. “This information is very pertinent to resource managers.”
The researchers say these results could be incorporated into decision-making as ocean conditions change.
“An example would be monitoring low-oxygen events in the summer, and maybe pulling the crab traps earlier,” Berger said. “This would help mitigate from the crabs dying in the trap.”
Further research on the Dungeness crab should include more lab studies on how the species responds to multiple stressors. More generally, authors say, the study shows a way to understand how marine species with complex life stages will respond to climate change.
Other co-authors are Darren Pilcher and Emily Norton at the UW-based Cooperative Institute for Climate, Ocean and Ecosystem Studies; Simone Alin and Isaac Kaplan at the National Oceanic and Atmospheric Administration; and Catherine Matassa at the University of Connecticut.
The research was funded by NOAA and was part of a regional vulnerability assessment for the Olympic Coast to ocean acidification.
NOAA grant: NA17OAR0170166
Part of this text was adapted from a press release by the University of Connecticut.
Oceanic measurements collected during a scientific cruise on NOAA ship Ronald H. Brown last week confirmed that a large area of poorly oxygenated water (known as hypoxia) is growing off the coast of Washington and Oregon.
Oxygen-depleted bottom waters occur seasonally along the continental shelf of Washington and Oregon when strong winds blowing along the coast in spring and summer trigger upwellings that bring deep, cold, nutrient-rich water to the surface. These waters fuel blooms of plankton. The plankton in turn feeds small animals like krill which themselves serve as food for many fish. When these blooms die off, they sink to the bottom, where their decomposition consumes oxygen, leaving less for organisms, such as crabs and bottom-dwelling fish.
Measurements collected by commercial fishermen using dissolved oxygen sensors provided by NOAA’s Coastal Hypoxia Research Program, as well as data from local moorings, also show a large area of hypoxic water.
Earliest Onset in 35 Years
“Low dissolved oxygen levels have become the norm in the Pacific Northeast, but this event started much earlier than we’ve seen in our records,” said Oregon State University Professor Francis Chan, director of the NOAA cooperative institute CIMERS. “This is the earliest start to the upwelling season in 35 years.”
Returning to port from the NOAA-sponsored West Coast Ocean Acidification Cruise, Richard Feely, an oceanographer with NOAA’s Pacific Marine Environmental Laboratory, said that dissolved oxygen and ocean acidity measurements are consistent with an event that has the potential to create “dead zones” later this summer. Dead zones occur when dissolved oxygen levels drop so low that crabs and other bottom-dwelling fish perish.
The last time scientists observed winds this strong was in 2006 when a large dead zone wiped out crabs and other bottom-dwelling marine life along the continental shelf, Chan said.
Concerns about this summer first arose in March, when a NOAA wind measurement station observed an early shift in winds that initiate upwelling. Winds strengthened in April when the first measurements of hypoxic conditions were recorded. In late May, a NOAA Fisheries survey off Washington and Oregon found large phytoplankton blooms and hypoxic conditions on the continental shelf in the area of Grays Harbor, Washington. At about the same time, beachgoers reported large numbers of dead crabs washing ashore in the area of Ocean Shores, Washington. In early June and again in July, samples along the Newport Line, a long-term monitoring transect off Newport, Oregon, also showed hypoxic waters.
West Coast Scientific Cruise Confirms Extent
The West Coast Ocean Acidification Cruise left port June 13 for its 45-day mission sampling along several transects from British Columbia to California. Supported by the NOAA Ocean Acidification Program, this recurring scientific cruise surveys ocean conditions for a host of environmental parameters to better understand the factors that influence ocean acidification and hypoxia, which are related. Scientists obtain measurements from a suite of sensors and floats and collect plankton and other sea life in net trawls.
During the cruise, NOAA ship Ronald H. Brown navigates a series of straight lines running from the edge of the continental shelf to the coast, allowing scientists to take regular measurements along the way. Feely said the scientists observed the hypoxic layer on all of the Washington and Oregon transect lines. While there are no measurements between those transect lines, he said the hypoxic layer likely covers the continental shelf region from the Olympic Peninsula in Washington to Heceta Bank on the central Oregon coast. Measurements did not indicate a hypoxic layer in Canadian transects or northern California.
A Surprise in a Plankton Net
One discovery on this cruise has Feely and fellow scientists anxious to get back into the laboratory. In U.S. waters, a plankton net retrieved vertically from depths of 100 meters surfaced with a large amount of a greenish-black substance in the finely woven fabric of the net. Feely suspects the net was towed through a thick layer of decaying plankton in the water column, the kind of thing responsible for creating hypoxic conditions.
“We added a little alcohol to the sample, and we began to realize that it was a large mass of phytoplankton, either still living or dead, sinking into the deeper water and possibly providing the fuel for the oxygen uptake as it decays,” he said. Samples will be taken back to Seattle for examination under a microscope.
As the West Coast Ocean Acidification Cruise moves south along the California coast, scientists will take ongoing measurements biweekly along the Newport, Oregon transect and by fishermen deploying dissolved oxygen sensors on commercial crab pots.
Meanwhile, indications are that the hypoxic waters in Oregon and Washington will persist and perhaps intensify. An important coastal model called J-SCOPE, developed by the Cooperative Institute for Climate, Ocean, and Ecosystem Studies, or CICOES, NOAA’s cooperative institute with the University of Washington, predicts a large hypoxic zone will remain through fall.
Severe biological effects under present-day estuarine acidification in the seasonally variable Salish Sea
S. Fisher Gonski, Micah J. Horwith, Skip Albertson, Julia Bos, Allison S. Brownlee, Natalie Coleman, Carol Falkenhayn Maloy, Mya Keyzers, Christopher Krembs, Greg Pelletier, Elisa Rauschl, Holly R. Young, Wei-Jun Cai
The Washington State Department of Ecology conducted a large-scale ocean acidification (OA) study in greater Puget Sound to: (1) produce a marine carbon dioxide (CO2) system dataset capable of distinguishing between long-term anthropogenic changes and natural variability, (2) characterize how rivers and freshwater drive OA conditions in the region, and (3) understand the relative influence of cumulative anthropogenic forcing on regional OA conditions. Marine CO2 system data were collected monthly at 20 stations between October 2018 and February 2020. While additional data are still needed, the climate-level data collected thus far have uncovered novel insights into spatiotemporal distributions of and variability in the regional marine CO2 system, especially at low salinities in shallow, river-forced shelf regions. The data provide a strong foundation with which to continue monitoring OA conditions across the region. More importantly, this work represents the first successful long-term OA monitoring program undertaken at the state-level by a regulatory agency. Therefore, we offer the work described herein as a blueprint to help state and local scientists and environmental and natural resource managers develop, implement, and conduct long-term OA monitoring programs and studies in their own contexts and jurisdictions.
Original post: https://www.tandfonline.com/
Coastal processes modify projections of some climate-driven stressors in the California Current System
Samantha A. Siedlecki1, Darren Pilcher2,5, Evan M. Howard3, Curtis Deutsch3, Parker MacCready3, Emily L. Norton2, Hartmut Frenzel3, Jan Newton4, Richard A. Feely5, Simone R. Alin5, and Terrie Klinger6
- 1Department of Marine Sciences, University of Connecticut, Groton, CT 06340, USA
- 2Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, Seattle, WA, 98105, USA
- 3School of Oceanography, University of Washington, Seattle, WA 98195, USA
- 4Applied Physics Laboratory, Washington Ocean Acidification Center, University of Washington, Seattle, WA 98105, USA
- 5NOAA Pacific Marine Environmental Laboratory (PMEL), Seattle, WA 98115, USA
- 6School of Marine Environment and Affairs, Washington Ocean Acidification Center, University of Washington, Seattle, WA 98105, USA
Correspondence: Samantha A. Siedlecki (firstname.lastname@example.org)
Received: 17 Jul 2020 – Discussion started: 05 Aug 2020 – Revised: 04 Mar 2021 – Accepted: 13 Mar 2021 – Published: 11 May 2021Abstract
Global projections for ocean conditions in 2100 predict that the North Pacific will experience some of the largest changes. Coastal processes that drive variability in the region can alter these projected changes but are poorly resolved by global coarse-resolution models. We quantify the degree to which local processes modify biogeochemical changes in the eastern boundary California Current System (CCS) using multi-model regionally downscaled climate projections of multiple climate-associated stressors (temperature, O2, pH, saturation state (Ω), and CO2). The downscaled projections predict changes consistent with the directional change from the global projections for the same emissions scenario. However, the magnitude and spatial variability of projected changes are modified in the downscaled projections for carbon variables. Future changes in pCO2 and surface Ω are amplified, while changes in pH and upper 200 m Ω are dampened relative to the projected change in global models. Surface carbon variable changes are highly correlated to changes in dissolved inorganic carbon (DIC), pCO2 changes over the upper 200 m are correlated to total alkalinity (TA), and changes at the bottom are correlated to DIC and nutrient changes. The correlations in these latter two regions suggest that future changes in carbon variables are influenced by nutrient cycling, changes in benthic–pelagic coupling, and TA resolved by the downscaled projections. Within the CCS, differences in global and downscaled climate stressors are spatially variable, and the northern CCS experiences the most intense modification. These projected changes are consistent with the continued reduction in source water oxygen; increase in source water nutrients; and, combined with solubility-driven changes, altered future upwelled source waters in the CCS. The results presented here suggest that projections that resolve coastal processes are necessary for adequate representation of the magnitude of projected change in carbon stressors in the CCS.
Original post: https://bg.copernicus.org/articles/18/2871/2021/