Paleoceanographic Proxy Calibration Completed
A sediment trap time series in the northern Gulf of Mexico is used to better assess the control of environmental variables (e.g., temperature and salinity) on the flux of both microfossils and molecular fossils to the sediments. The information gained from sediment trap studies is used to develop better proxy-based estimates of past oceanographic conditions from analyses of microfossils and molecular fossils in sediment cores.
USGS Researchers Trap Sediment to Measure Climate Change
Sediment trap studies help scientists better understand the environmental factors (e.g., temperature, salinity, ocean circulation, nutrient supply, etc.) that control the chemical composition, ecology, and life history of planktonic organisms living in the water column. These planktonic organisms, preserved in ocean sediments as microfossils or molecular fossils, can be used to reconstruct oceanographic conditions in the Gulf of Mexico over the past few centuries to the past few millions of years. Scientists at the USGS are using a long-running sediment trap (2008-2018+) in the northern Gulf of Mexico to calibrate foraminifera, biomarker, and other micropaleontological proxies for use in climate reconstructions.
Gulf of Mexico sediment trap
Planktic foraminifera from the Gulf of Mexico
Planktic foraminifera are single-celled organisms that live in the ocean and build shells made of calcium Carbonate (CaCO3). The oxygen isotopic ratio (ð18O) and the Magnesium to Calcium ratio (Mg/Ca) in their shells can be related back to the temperature and salinity at which they grew, allowing for paleoceanographic reconstruction from sediment cores collected from the seafloor.
The sediment trap allows scientists to investigate the depth habitat and seasonality of each planktic species of foraminifera in the Gulf of Mexico, along with variations in flux from year-to-year. Since there are good observations of temperature and salinity available from satellites and buoys, foraminifera from the sediment trap are also being used to improve the calibration of foraminiferal chemistry and oceanographic parameters.
Biomarkers
Biomarkers are molecular organic compounds that are specific to certain groups of organisms. Alkenones are biomarkers produced by coccolithophores, a type of calcareous phytoplankton or algae. The relative proportion of C37 alkenones with 2 double bonds and 3 double bonds can be calibrated back to the temperature of the surface ocean. This makes alkenones a valuable and widely used proxy for past ocean temperature. However, the seasonal production of coccolithophores can vary in different regions, making detailed studies of alkenone flux important to applying this proxy in the subtropical Atlantic Ocean.
GDGTs (glycerol dibiphytanyl glycerol tetraethers) are compounds produced primarily by marine archaea. An index called TEX86, based on the distribution of cyclopentane rings in GDGTs, is related to sea surface temperature globally. The TEX86 proxy, and flux of GDGTs varies across the global ocean, making regional studies particularly important to understanding the strengths and limitations of this temperature proxy.
Alkenone and GDGT Flux in the Gulf of Mexico Sediment Trap
This research is part of the Climate and environmental change in the Gulf of Mexico and Caribbean project.
Below are tasks and science projects associated with this research.
Climate and Environmental Change in the Gulf of Mexico and Caribbean
Below are publications associated with this research.
Gulf of Mexico Climate-History Calibration Study
Seasonal Flux and Assemblage Composition of Planktic Foraminifera from the Northern Gulf of Mexico
- Overview
A sediment trap time series in the northern Gulf of Mexico is used to better assess the control of environmental variables (e.g., temperature and salinity) on the flux of both microfossils and molecular fossils to the sediments. The information gained from sediment trap studies is used to develop better proxy-based estimates of past oceanographic conditions from analyses of microfossils and molecular fossils in sediment cores.
USGS Researchers Trap Sediment to Measure Climate Change
Sediment trap studies help scientists better understand the environmental factors (e.g., temperature, salinity, ocean circulation, nutrient supply, etc.) that control the chemical composition, ecology, and life history of planktonic organisms living in the water column. These planktonic organisms, preserved in ocean sediments as microfossils or molecular fossils, can be used to reconstruct oceanographic conditions in the Gulf of Mexico over the past few centuries to the past few millions of years. Scientists at the USGS are using a long-running sediment trap (2008-2018+) in the northern Gulf of Mexico to calibrate foraminifera, biomarker, and other micropaleontological proxies for use in climate reconstructions.
Gulf of Mexico sediment trap
Planktic foraminifera from the Gulf of Mexico
Planktic foraminifera are single-celled organisms that live in the ocean and build shells made of calcium Carbonate (CaCO3). The oxygen isotopic ratio (ð18O) and the Magnesium to Calcium ratio (Mg/Ca) in their shells can be related back to the temperature and salinity at which they grew, allowing for paleoceanographic reconstruction from sediment cores collected from the seafloor.
The sediment trap allows scientists to investigate the depth habitat and seasonality of each planktic species of foraminifera in the Gulf of Mexico, along with variations in flux from year-to-year. Since there are good observations of temperature and salinity available from satellites and buoys, foraminifera from the sediment trap are also being used to improve the calibration of foraminiferal chemistry and oceanographic parameters.
Biomarkers
Biomarkers are molecular organic compounds that are specific to certain groups of organisms. Alkenones are biomarkers produced by coccolithophores, a type of calcareous phytoplankton or algae. The relative proportion of C37 alkenones with 2 double bonds and 3 double bonds can be calibrated back to the temperature of the surface ocean. This makes alkenones a valuable and widely used proxy for past ocean temperature. However, the seasonal production of coccolithophores can vary in different regions, making detailed studies of alkenone flux important to applying this proxy in the subtropical Atlantic Ocean.
GDGTs (glycerol dibiphytanyl glycerol tetraethers) are compounds produced primarily by marine archaea. An index called TEX86, based on the distribution of cyclopentane rings in GDGTs, is related to sea surface temperature globally. The TEX86 proxy, and flux of GDGTs varies across the global ocean, making regional studies particularly important to understanding the strengths and limitations of this temperature proxy.
Alkenone and GDGT Flux in the Gulf of Mexico Sediment Trap
This research is part of the Climate and environmental change in the Gulf of Mexico and Caribbean project.
- Science
Below are tasks and science projects associated with this research.
Climate and Environmental Change in the Gulf of Mexico and Caribbean
This project documents paleoceanographic, climatic, and environmental changes in the Gulf of Mexico and adjacent land areas over the last 10,000 years. The paleoenvironmental data is used to determine rates of change in the past, and to better understand both the natural and anthropogenic factors that contribute to climate variability on inter-annual to millennial timescales. - Publications
Below are publications associated with this research.
Filter Total Items: 14Gulf of Mexico Climate-History Calibration Study
Reliable instrumental records of past climate are available for about the last 150 years only. To supplement the instrumental record, reconstructions of past climate are made from natural recorders such as trees, ice, corals, and microfossils preserved in sediments. These proxy records provide information on the rate and magnitude of past climate variability, factors that are critical to distinguiAuthorsJessica W. Spear, Richard Z. PooreSeasonal Flux and Assemblage Composition of Planktic Foraminifera from the Northern Gulf of Mexico
A year-long sediment-trap experiment was conducted in the northern Gulf of Mexico (GOM) between January and December 2008 to study the flux and assemblage composition of planktic foraminifera from the region for comparison with concurrent hydrographic and climatic measurements. Ten species, or varieties, of planktic foraminifera constitute >80 percent of the assemblage: Globigerinoides ruber (pinkAuthorsKathy A. Tedesco, Jessica W. Spear, Eric Tappa, Richard Z. Poore