63 Ocean Acidification and Other Stressors
Description: Maps and variability of regional carbonate chemistry and other oceanographic properties
Indicator family:
Contributor(s): Grace Saba, Lori Garzio
Affiliations: Rutgers University
63.1 Introduction to Indicator
Ocean acidification (OA) has caused measured declines in global ocean pH and is projected to continue declining by up to 0.30 pH units over the course of the 21st century if high carbon dioxide emissions continue (IPCC 2019). OA also changes the availability of minerals required by organisms to form calcified structures such as shells and other structures. Calcifying conditions in seawater can be determined by measuring aragonite saturation state (ΩArag or omega), the tendency of a common type of calcium carbonate, aragonite, to form or dissolve. When ΩArag is less than 1, shells and other calcium carbonate structures begin to dissolve. Typical surface ocean ΩArag is 2-4, but extremes can be <1 or >5. As the ocean absorbs carbon dioxide, both pH and ΩArag decrease and can cause organisms to respond with reduced survival, calcification rates, growth, and reproduction, as well as impaired development, and/or changes in energy allocation (reviewed in [110], [111]). However, sensitivity levels vary, and some organisms exhibit negative responses to calcification and other processes when ΩArag is as low as 3.
The U.S. Northeast Shelf (NES) is prone not only to global rates of ocean acidification, but also to coastal processes that can act to exacerbate acidification, including freshwater sources (primarily riverine), eutrophication and photosynthesis‐respiration cycles, coastal upwelling, and other influences ([112], [113], [114]). Often times, other stressors such as ocean warming and/or low bottom water dissolved oxygen can co-occur. Dissolved oxygen concentrations at or below 5 mg/liter is considered problematic for marine life. Although concentrations between 3-5 mg/liter may not be low enough to directly cause death in many marine animals, research focused on marine species has identified other negative impacts such as reduced metabolism, feeding, growth, and reproduction at these levels. Lower hypoxic concentrations of dissolved oxygen (< 3 mg/liter) have been directly associated with mortalities in some organisms in other coastal regions around the world.
Any one stressor may not itself be an issue due to the resiliency of many coastal species to fluctuating natural environmental conditions. However, when more than one stressor occurs simultaneously, an organism may become unable to fully withstand changes. The impacts of multiple stressors occurring simultaneously on organism health is much less well known. The co-occurrence of low dissolved oxygen and pH may exacerbate negative responses in organisms or increase their susceptibility to either or both oxygen and pH.
The spatio-temporal variability of OA in the NES is still poorly described, and as of yet there are no analyses that have determined times or locations where multiple environmental stressors are co-located. The purpose of developing data products for OA and other stressors for the State of the Ecosystems reports is to determine locations and times where potential stressors overlap in space and time to assist in identifying potentially vulnerable species habitats.
63.2 Key Results and Visualizations
The products developed here include: static and animated maps of seasonal surface and bottom pH and aragonite saturation state (omega) on the U.S. Northeast Shelf; maps of locations where species sensitivity levels for aragonite saturation state were reached in bottom water for representative Mid-Atlantic Bight (MAB) and Gulf of Maine (GoM) species during winter (MAB: 2012-2024, GoM: 2012-2023), spring (MAB: 2014-2024, GoM: 2014-2022), summer (MAB: 2007-2024, GoM: 2012-2023), and fall (MAB and GoM: 2013-2023); and maps showing variable bottom temperature anomalies, bottom aragonite saturation state, and surface chlorophyll anomalies for the summers of 2022, 2023, and 2024.
Seasonal surface and bottom pH and aragonite saturation state on the U.S. Northeast Shelf
Using available quality-controlled vessel- and glider-based datasets accompanying observations on the U.S. Northeast Shelf, maps of seasonal surface and bottom pH and aragonite saturation state (ΩArag) were generated for the U.S. Northeast Shelf (Figs. 1-4). For bottom observations (Figs. 1-2): winter= 2012-2024, spring= 2014-2024, summer= 2007-2024, fall= 2013-2023. For surface observations (Figs. 3-4): winter=2012-2024, spring= 2006-2024, summer= 2004-2024, fall= 2013-2023. These were also combined to create animations of pH and omega over time in the region (pH: access here; omega: access here).
The animations depict high variability in time and space and increases in sampling frequency and spatial coverage over time. Spatially, the lowest surface and bottom pH and aragonite saturation state have occurred primarily in the western Gulf of Maine, western Long Island Sound, nearshore to mid-shelf waters of the Mid-Atlantic Bight off the coast of New Jersey and New York, and, for bottom aragonite saturation state, in waters > 1000 meters. Seasonally in the U.S. Northeast Shelf, the lowest bottom pH and aragonite saturation state levels, covering the most spatial area, have occurred primarily in the summer, followed by fall. In the Mid-Atlantic, the lowest observed values of surface pH were observed in the summer and the lowest surface aragonite saturation state levels occurred in western Long Island Sound and nearshore New Jersey coastal waters during the summer and in slope waters during the winter. In the Gulf of Maine, the lowest observed values of surface pH and aragonite saturation state occurred in the winter and fall seasons.
Figure 1. Seasonal bottom pH on the U.S. Northeast Shelf plotted from available quality-controlled vessel- and glider-based datasets. Winter (Dec, Jan, Feb) data availability: 2012-2024; Spring (Mar, Apr, May) data availability: 2014-2024; Summer (Jun, Jul, Aug) data availability: 2007-2024; and Fall (Sept, Oct, Nov) data availability: 2013-2023.
Figure 2. Seasonal bottom aragonite saturation state (omega) on the U.S. Northeast Shelf plotted from available quality-controlled vessel- and glider-based datasets. Winter (Dec, Jan, Feb) data availability: 2012-2024; Spring (Mar, Apr, May) data availability: 2014-2024; Summer (Jun, Jul, Aug) data availability: 2007-2024; and Fall (Sept, Oct, Nov) data availability: 2013-2023.
Figure 3. Seasonal surface pH on the U.S. Northeast Shelf plotted from available quality-controlled vessel- and glider-based datasets. Winter (Dec, Jan, Feb) data availability: 2012-2024; Spring (Mar, Apr, May) data availability: 2006-2024; Summer (Jun, Jul, Aug) data availability: 2004-2024; and Fall (Sept, Oct, Nov) data availability: 2013-2023.
Figure 4. Seasonal surface aragonite saturation state (omega) on the U.S. Northeast Shelf plotted from available quality-controlled vessel- and glider-based datasets. Winter (Dec, Jan, Feb) data availability: 2012-2024; Spring (Mar, Apr, May) data availability: 2006-2024; Summer (Jun, Jul, Aug) data availability: 2004-2024; and Fall (Sept, Oct, Nov) data availability: 2013-2023.Locations and times where species sensitivity levels for aragonite saturation state were reached
Using the bottom water aragonite saturation state data, maps depicting locations where bottom aragonite saturation state reached lab-derived sensitivity levels within the habitat depth range of designated target species in the Mid-Atlantic Bight (MAB) and Gulf of Maine (GoM) were developed for winter (Dec, Jan, Feb; MAB: 2012-2024, GoM: 2012-2023), spring (Mar, Apr, May; MAB: 2014-2024, GoM: 2014-2022), summer (Jun, Jul, Aug; MAB: 2007-2024, GoM: 2012-2023), and fall (Sept, Oct, Nov; MAB and GoM: 2013-2023) seasons. The target species selected for the Mid-Atlantic were Atlantic sea scallop (Placopecten magellanicus) and longfin squid (Doryteuthis pealeii), and the target species selected for the Gulf of Maine were Atlantic cod (Gadus morhua) and American lobster (Homarus americanus). Note there are no data yet available for fall 2024 for Mid-Atlantic species. Additionally, maps for Atlantic cod and American lobster do not include any 2024 data because data from this year for the Gulf of Maine are not available. However, the maps for the individual years between 2012-2023 and the combined map for this same time period are available for these species and described below. Bottom water data collected during 2024 (with the exception of the fall season) were incorporated to update this product for the Mid-Atlantic species, Atlantic sea scallop and longfin squid (described below). Plots for each target species can be accessed here.
Aragonite saturation state was at or below the sensitivity levels for both Atlantic sea scallop (Placopecten magellanicus; Fig. 5) and longfin squid (Doryteuthis pealeii; Fig. 6) most frequently during the summer, although these levels were reached for both species also during fall 2023 and, for Atlantic sea scallop in spring 2024. The sensitivity levels of bottom aragonite saturation state occurred during August 2016, July 2018, August 2019, July-October 2023, and August 2024 for both species, and additionally in August 2021, August 2022 and April-May 2024 for the Atlantic sea scallop, and in June-July 2024 for the longfin squid. The comparison between the 2007-2022, 2023, and 2024 maps reveals that the lower aragonite saturation state conditions that occurred in the Mid-Atlantic coastal shelf during the two most recent years (2023 and 2024) not only increased the spatial range of potentially unfavorable habitat for Atlantic sea scallops and longfin squid in the summer-time compared to the observed past years, but also marked the first time these sensitivity levels were reached in observations outside of the summer season: fall for both species and spring for Atlantic sea scallops.
Figure 5. Locations where bottom aragonite saturation state (omega) in the habitat depth range were at or below the laboratory-derived sensitivity level for Atlantic sea scallop during different seasons for the time periods 2007-2022 (dark cyan), 2023 only (magenta), and 2024 only (cyan). There are no data included for fall 2024. Gray circles indicate locations where bottom omega values were above the species-specific sensitivity values and/or outside of the habitat depth range.
Figure 6. Locations where bottom aragonite saturation state (omega) in the habitat depth range were at or below the laboratory-derived sensitivity level for longfin squid during different seasons for the time periods 2007-2022 (dark cyan), 2023 only (magenta), and 2024 only (cyan). There are no data included for fall 2024. Gray circles indicate locations where bottom omega values were above the species-specific sensitivity values and/or outside of the habitat depth range.Aragonite saturation state was at or below the sensitivity levels for both Atlantic cod (Gadus morhua; Fig. 7) and American lobster (Homarus americanus; Fig. 8) most frequently during the summer, although these levels were also reached at a few locations for both species during fall and winter. The locations this typically occurred within their habitat depth ranges were in western Gulf of Maine and off the coast of eastern Maine. These areas include Stellwagen Bank, slope waters south of Penobscot and Blue Hill Bays, and Wilkinson Basin and additionally, for Atlantic cod, slope waters south of Maquoit Bay and in waters of Jeffreys Ledge and Jordan Basin. The sensitivity levels of bottom ΩArag for Atlantic cod occurred in at least one of these areas during July 2007, February and August 2012, June and November 2013, June and October 2015, June and August 2016, June and November 2017, June and July 2018, August and October 2019, and July and October 2021, June August September-October 2022 and December 2022, and June and August 2023, and for American lobster during February 2012, June 2013, November 2014, October 2015, June 2016, February 2017, June and August 2019, May July August and October 2021, June August and September 2022, and June and August 2023.
Figure 7. Locations where bottom aragonite saturation state (omega) in the habitat depth range were at or below the laboratory-derived sensitivity level for Atlantic cod during different seasons for the time periods 2007-2022 (dark cyan) and 2023 only (magenta). There are no data included for 2024. Gray circles indicate locations where bottom omega values were above the species-specific sensitivity values and/or outside of the habitat depth range.
Figure 8. Locations where bottom aragonite saturation state (omega) in the habitat depth range were at or below the laboratory-derived sensitivity level for American lobster during different seasons for the time periods 2007-2022 (dark cyan) and 2023 only (magenta). There are no data included for 2024. Gray circles indicate locations where bottom omega values were above the species-specific sensitivity values and/or outside of the habitat depth range.Interannual variability between summers of 2022, 2023, 2024
The progression from summer 2022 to summer 2024 in the Mid-Atlantic is characterized by an intense switch from a warmer bottom temperature anomaly in 2022 to a colder bottom temperature anomaly in 2024 (Fig. 9, row A). This trend also occurs in the Gulf of Maine, but between the summers of 2023 and 2024. This is likely driven by a greater volume input of Labrador Slope water to both the Gulf of Maine and shelf waters of the Mid-Atlantic in 2024. In the Mid-Atlantic, this cooling corresponds with decreasing summer bottom aragonite saturation state values between 2022 and 2024 (Fig. 9, row B). The bottom aragonite saturation state observed on the Mid-Atlantic coastal shelf during summer 2024 are the lowest values recorded when compared to all of the years sampled (since 2007). At the same time, there was little difference in chlorophyll-a anomalies between the 3 years in the Mid-Atlantic compared to the Gulf of Maine which saw a large swing from positive to negative chlorophyll-a anomaly between 2023 and 2024. If we loosely define chlorophyll climatology as a proxy for food availability, this suggests that for the Mid-Atlantic, there is little to no change in that availability over time while aragonite saturation state levels are decreasing (and summer conditions are potentially becoming more stressful for vulnerable organisms).
Figure 9. Bottom temperature anomaly (row A), bottom aragonite saturation state (row B), and surface chlorophyll anomaly (row C) for the summers of 2022 (left column), 2023 (middle column), and 2024 (right column). The bottom temperature anomaly for each summer-year was calculated as the difference from the summer mean 2012-2024. Bottom temperature data courtesy of the E.U. Copernicus Marine Service Information (CMEMS): Global Ocean Physics Reanalysis (GLORYS12V1) dataset. The bottom aragonite saturation state values were those observed from available vessel- and glider-based efforts during the summers of 2022, 2023, and 2024. The surface chlorophyll-a anomaly for each summer-year was calculated as the difference from the summer mean 2012-2024. Satellite-derived surface chlorophyll-a data courtesy of the NASA Ocean Biology Distributed Active Archive Center (OB.DAAC).
63.3 Indicator statistics
Spatial scale: Seasonal surface and bottom pH and aragonite saturation state on the U.S. Northeast Shelf: full U.S. Northeast Shelf; Locations and times where species sensitivity levels for aragonite saturation state were reached: Mid-Atlantic Bight (Atlantic sea scallop, longfin squid) and Gulf of Maine (Atlantic cod, American lobster); Interannual variability between summers of 2022, 2023, 2024: full U.S. Northeast Shelf
Temporal scale: Seasonal surface and bottom pH and aragonite saturation state on the U.S. Northeast Shelf: winter (Dec, Jan, Feb)= 2012-2024, spring (Mar, Apr, May)= 2006-2024, summer (Jun, Jul, Aug)= 2004-2024, fall (Sep, Oct, Nov)= 2013-2023 (for surface observations) and winter= 2012-2024, spring= 2014-2024, summer= 2007-2024, fall= 2013-2023 (for bottom observations); Locations and times where species sensitivity levels for aragonite saturation state were reached for target species in the Mid-Atlantic Bight (MAB) and Gulf of Maine (GoM): winter= 2012-2024, spring= 2014-2024, summer= 2007-2024, fall= 2013-2023 (for the MAB) and winter= 2012-2023, spring= 2014-2022, summer= 2012-2023, fall= 2013-2023; Interannual variability between summers of 2022, 2023, 2024: summer (June-August) 2022, 2023, 2024 and summer-year anomalies for bottom temperature and surface chlorophyll-a were calculated as the difference from the summer mean 2012-2024.
Synthesis Theme:
63.4 Implications
While the sparsity of carbonate chemistry data at annual and seasonal scales to date limits our ability to calculate anomalies from a long-term mean or to determine exposure frequency and duration of unfavorable conditions to marine species, locations where recurring low levels of seawater pH and aragonite saturation state can be identified from the available data. These areas include the western Gulf of Maine, western Long Island Sound, and nearshore to mid-shelf waters of the Mid-Atlantic Bight off the coast of New Jersey and New York. This information helps to identify potential vulnerable species habitats and can guide future targeted observations aimed at determining stressor exposure frequency and duration and the co-occurrence of additional environmental stressors.
The updated datasets this year provided the seasonal evaluation of available carbonate chemistry data to be included in this report, and they highlighted the lowest and most spatially extensive pH and aragonite saturation state levels occurred in bottom water and primarily in the summer season, followed by fall. The addition of the 2024 data to the bottom water products in the Mid-Atlantic (2007-2024) revealed that the lowest observed aragonite saturation state values were recorded during summer 2024, and the lower aragonite saturation state values during the past two summers (2023, 2024) have increased the spatial and temporal range of potentially unfavorable habitat for local species compared to past observed years (2007-2022). Events such as these that may prevent the ability to sustain normal populations of marine organisms are concerning, not only for the ocean ecosystem but also for the local economy and commercial and recreational fishing industries. Understanding the factors that cause these events will aid in projecting the severity and duration of these events under ongoing climate change and provide important support for guiding policy and management options and identifying priorities for science and monitoring.
63.5 Get the data
Point of contact: Grace Saba (saba@marine.rutgers.edu); Lori Garzio (lgarzio@marine.rutgers.edu)
ecodata name: No dataset
Variable definitions
- depth_interpolated meters 2) temperature degrees Celsius 3) chlorophyll_a µg L-1 4) oxygen_concentration_shifted_mgL mg L-1 5) pH_shifted 6) aragonite_saturation_state
No Data
Indicator Category: