skip to main content

Attention:

The NSF Public Access Repository (NSF-PAR) system and access will be unavailable from 11:00 PM ET on Friday, July 12 until 2:00 AM ET on Saturday, July 13 due to maintenance. We apologize for the inconvenience.


Title: Documenting Environmental and Oceanic Variability in the Down East Coastal Region of the Gulf of Maine using the long-lived bivalve Arctica islandica
The Gulf of Maine (GoM) is currently undergoing rapid environmental and ecological changes and this system is projected to become increasingly stressed in the coming decades. Thus understanding past spatial and temporal conditions of this region is key to understanding how future environmental changes and extreme events may impact fisheries and ecosystem dynamics in the GoM. Changes in the physical and chemical variations in the shells of mollusks can be used as a powerful proxy for studying past climates and environments. In this study, we used the growth and geochemistry signatures in the long-lived marine bivalve Arctica islandica collected from the Down East coastal region in the Gulf of Maine (Jonesport, ME) to evaluate past climatic and hydrographic variability in the northwestern North Atlantic Ocean. The recent collection of shells extends a previously developed master shell growth chronology by 11 years and now spans from 1954 to 2020 CE. Based on visual crossdating techniques, shell growth variability is highly coherent among the population indicating that environmental conditions are driving growth. Variability in annually resolved shell growth increments and stable oxygen isotope values are largely related to sea surface temperatures (SSTs) and water mass properties of the Eastern Maine Coastal Current. This master shell growth chronology and annually-resolved isotope series will fill data gaps prior to instrumental records and allow us to better understand the spatial oceanographic variability in the GoM.  more » « less
Award ID(s):
2028197
NSF-PAR ID:
10341585
Author(s) / Creator(s):
; ; ;
Date Published:
Journal Name:
PAGES Open Science Meeting
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Coastal systems can exhibit large variability in pH compared to open marine conditions, thus the impacts of ocean acidification (OA) on their resident calcifying organisms are potentially magnified. Further, our understanding of the natural baseline and variability of pH is spatially and temporally limited in coastal settings. In the few coastal locations that have been monitoring seawater pH, records are generally limited to <10 years and are thus unable to provide the full range of centennial to decadal natural variability. This is the case for the Gulf of Maine (northwestern Atlantic), a highly productive region of strategic importance to U.S. fisheries, that is facing multiple environmental stressors including rapid warming and threats from OA. Paleoceanographic proxy records are therefore much needed in this region to reconstruct past pH conditions beyond instrumental records. A clear candidate for this is the boron isotope (d11B) pH proxy provided the d11B sensitivity to pH in long-lived shallow water marine carbonates can be established. To this end, we grew juvenile and adult Arctica islandica (ocean quahog) in flowing seawater tanks for 20.5 weeks in controlled pH (7.4, 7.6, 7.8 or 8.0 (ambient) ± 0.02) and temperature (6, 9 or 12 ± 0.56 °C) conditions at Bowdoin College’s Schiller Coastal Studies Center, Harpswell, Maine (USA). The clams were stained twice with calcein and supplemented with food (Shellfish Diet) throughout the experiment to ensure suitable growth. New shell growth (average 67% increase in maximum shell height and 522% increase in buoyant weight across all treatments), constrained by calcein markings, were sampled for boron isotope analysis (d11B) to determine if shell d11B varied as a function of pH similar to many other calcifying organisms. The results of the culture experiment will yield whether or not Arctica islandica preserves seawater pH information in their shells. If so, the transfer function relating shell d11B to pH will be used to hindcast pH in the central coastal region of the Gulf of Maine during recent centuries. Alternatively, if the shell d11B signal is independent of ambient seawater pH, this may reveal the capacity of Arctica islandica to regulate internal calcifying fluid chemistry and their resilience to OA. 
    more » « less
  2. Warming in recent decades in the North Atlantic Ocean has been heterogeneous, with locations along the northwestern Atlantic experiencing some of the largest and fastest warming in the last 100 years. This region is important for fisheries but has limited spatial and temporal hydrographic instrumental series extending beyond the past decades, especially along the coastal United States portion of the northwestern Atlantic, thus impacting our understanding of past climatic variability. To provide a longer temporal context for these changes, we constructed a continuous master shell growth chronology spanning the last two centuries and provided geochemical records from the Mid-Atlantic region using the long-lived marine bivalve Arctica islandica. Shells were collected on the outer shelf region off Ocean City, Maryland, in ~ 60 m water depth. This region is sensitive to large-scale North Atlantic Ocean dynamics, including the Atlantic Meridional Overturning Circulation (AMOC) and Gulf Stream eddies. Based on growth histories and shell oxygen isotopes, we provide evidence of hydrographic variability beyond the relatively short instrumental period and evaluate the likely causes for these changes. These data allow us to better characterize recent and past oceanographic changes in the Mid-Atlantic region, synthesize the new results with previously developed paleo-records in the northwestern Atlantic, and provide guidance for the management of fisheries in this region. 
    more » « less
  3. Abstract The Gulf of Maine and surrounding western North Atlantic shelf are some of the fastest warming regions of the worlds oceans. The lack of long-term observational records from this area inhibits the ability to assess the timing and initial causes of this warming and consequently accurately predict future changes to this ecologically and economically important region. Here we present oxygen, nitrogen, and radiocarbon isotope data measured in Arctica islandica shells collected in the western North Atlantic to better understand the past temperature and ocean circulation variability of the region over the last 300 years. We combine these results with output from the Community Earth System Model Last Millennium Ensemble simulations to assess the temporal and spatial context of these isotope records. We find that the isotope records capture the end and reversal of a millennium-scale cooling trend in the Gulf of Maine. Last Millennium Ensemble single-forcing simulations indicate that this cooling trend appears to be largely driven by volcanic forcing. The nitrogen and radiocarbon records indicate that ocean circulation is in part driving the reconstructed hydrographic changes, pointing to a potential role of the Atlantic Meridional Overturning Circulation in regulating Gulf of Maine temperatures as suggested by the Last Millennium Ensemble simulations. Both isotope and model results suggest that the Gulf of Maine began to warm in the late 19th century, ultimately driven by increased greenhouse gas forcing. Plain-language Summary The Gulf of Maine, located off of the Eastern Coast of the United States, has experienced significant temperature increases recently. Because the instrumental record only began in 1905, we do not have a good idea of when this warming began and what may have initially caused the warming. Here, we analyze the chemistry of clam shells, which have grown in the Gulf of Maine for hundreds of years, to infer past changes in ocean temperatures and water properties. We combine these results with output from a climate model to reveal that the temperatures reconstructed from the clams shells agree well with the model during the period of overlap. Both the chemical records and the model suggest the Gulf of Maine started warming in the late 1800s as a result of increased atmospheric greenhouse gas concentrations. Before this warming began, the Gulf of Maine region appears to have been cooling. The model suggests that this cooling trend is likely due to the influence of volcanic eruptions. The chemical records from the clam shells also suggest that part of this cooling is likely related to changing ocean circulation patterns. 
    more » « less
  4. Abstract

    In order to document relative changes in water mass contributions in the Gulf of Maine (GoM), we used the shell material of the long‐lived ocean quahog (Arctica islandica). A multicentury, crossdated master shell growth chronology facilitated the reconstruction of a radiocarbon Δ14C history prior to the radiocarbon bomb‐pulse of the 1950s. This reconstruction reveals a highly variable Δ14C series (mean = −56.6 ± 8.0‰ (1σ);N = 34) from CE 1685 to 1935. Δ14C values indicate a rapid shift ca. 1860 CE in source waters to the GoM. From CE 1685 to 1860, GoM waters were dominated by an admixture of Warm Slope Water primarily composed of tropical Atlantic surface waters/Gulf Stream Waters, and Scotian Shelf Water. This water regime was followed by a rapid Δ14C transition to a Labrador Slope Water endmember after CE 1860, with an apparent decrease in Scotian Shelf Water. Together, this shift is likely related to broader changes in the Arctic and the Labrador Sea, and a short‐term strengthening of the Atlantic meridional overturning circulation. Labrador Slope Water dominating GoM hydrography in the 1900s is verified by the similarities between this record and other coral‐ and shell‐derived Δ14C records influenced by waters with Labrador Sea origin. This suggests that GoM radiocarbon variability broadly reflects large‐scale ocean circulation processes in the Northwestern Atlantic. The lack of Δ14C values much below the Labrador Slope Water endmember suggests that the interior GoM gets very little to no Antarctic Intermediate Water as other studies had previously suggested.

     
    more » « less
  5. Warming in the North Atlantic Ocean has been heterogeneous in recent decades, with locations along the eastern United States seaboard (northwestern Atlantic) seeing some of the largest and fastest warming in the last 100 years. In order to provide a longer temporal context for these changes, we are in the process of developing several master shell growth chronologies and associated geochemical records from theMid-Atlantic coast using the shells of the long-lived marine bivalve Arctica islandica. Based on the shell collection locations (shelf regions offOcean City, Maryland in ~ 61 m water depth and Long Island, New York in ~47 m water depth) and shell geochemistry measurements, we will be able to better ascertain hydrographic spatial and temporal variability of subtropical Atlantic water moving northward through time. These findings will be integrated with similar sclerochronology datasets previously published from the Gulf of Maine region and several others from theMid-Atlantic region that are currently being constructed. Collectively, this network of sclerochronology records will allow us to better characterize changes in the northwestern Atlantic and provide hydrographic insights beyond the relatively short instrumental record and evaluate potential dynamical forcings through time. 
    more » « less