238-12 Analyzing Drivers of Species Distribution of Planktonic Foraminifera Along the U.S. East Coast

Session: Recent Advances and New Voices in Marine and Coastal Geoscience

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Abstract:

Planktonic foraminifera are single-celled zooplankton that are important contributors of carbonate flux to the deep ocean, and their calcium carbonate shells and sensitivity to environmental conditions make them useful proxies for reconstructing past climate. Understanding their distribution is important in understanding the marine carbon cycle as well as chemical conditions in the upper water column. Living foraminiferal assemblages have not been reported in relation to the large environmental gradients present along the northwestern Atlantic margin, and no systematic surveys have been published from anywhere on the U.S. east coast since the 1960s. This study seeks to document observations and drivers of current foraminifera species abundance and diversity in the northwestern Atlantic using plankton tows from the 2022 NOAA East Coast Ocean Acidification cruise. Samples were collected in August and September 2022 at 59 stations spanning the entire U.S. east coast from the Gulf of Maine (45.66º N) to Florida (26.98º N). Vertically integrated bongo net tows were conducted with maximum depths ranging from 70 to 202 m, using a mesh size of 153 µm. SST ranged from 13.0 ºC to 30.5 ºC, and pH ranged from 7.81 to 8.14.

Findings indicate a north-south gradient in species composition that is linked to temperature. Patterns in species composition indicate two distinct ecological regions. The Gulf of Maine is characterized by high numbers of Neogloboquadrina incompta along with Turborotalita quinqueloba and the cold-water species Neogloboquadrina pachyderma. South of Cape Cod, the Mid-Atlantic Bight and South Atlantic Bight follow similar patterns in species composition, overwhelmingly dominated by the warm-water species Globeriginoides ruber ruber and Globeriginoides ruber albus. There is not a significant relationship between temperature and foraminifera per liter, size of foraminiferal shells (a proxy for total foraminiferal calcite production), or diversity. However, individual species show preferences for distinct temperature ranges. N. incompta and N. pachyderma abundances decrease with increasing temperature and pH, while G. ruber ruber and G. ruber albus exhibit the opposite trend. Preliminary analyses indicate a northward shift of key species relative to previous surveys and core-top samples that is potentially related to the increase in SST over the past 5+ decades.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9716

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