Geology topics

Caitlin E. Reynolds

Publications and source records attributed to Caitlin E. Reynolds.

12 recordsLinked to original sources

USGS2026

Shifting phenology in planktonic foraminifera in the Gulf of America (Mexico) with 21st century warming

We investigate trends in foraminiferal phenology using a 12-year (2008–2020), well-resolved (7 to 28-day resolution) time series of planktonic foraminiferal fluxes from a U.S. Geological Survey sediment trap in the northern Gulf of America (Gulf of Mexico; 27.5°N, 90.3°W). The total foraminiferal flux declined over this time. We used Horn-Morisita dissimilarity analysis, principal coordinate analysis, and correlation matrices to show that fall assemblages became more similar in composition to summer assemblages (July–September) over the 12 years. As a result, winter (January–March) and fall (October–December) assemblages, which dominate the total annual foraminiferal flux, became more dissimilar in composition. This pattern is consistent with multidecadal, non-uniform trends of increasing seasonal sea surface temperatures, affecting the seasonality and composition of foraminiferal communities through changing species phenology. We speculate that similar phenological changes across plankton communities might have led to trophic mismatch, causing the decline in total foraminiferal flux.

Journal of Foraminiferal Research↗

USGS2026

Synthesizing a twelve-year sediment trap time series of planktic foraminiferal flux in the Gulf of America (Mexico)

Sediment trap time series provide powerful frameworks for testing hypotheses about planktic foraminiferal assemblage composition, seasonality, and geochemical responses to environmental variability, all of which are central to improving paleoceanographic reconstructions. We present high resolution foraminiferal assemblage data from a long-running sediment trap (2008–2020) in the northern Gulf of America (Mexico). This study summarizes the species composition, seasonality, and size distribution of the fifteen most abundant species of planktic foraminifera, which account for 98% of total flux. Foraminiferal flux peaks in winter and reaches a minimum in summer, following the seasonal pattern of primary production in the northern Gulf. Winter assemblages are dominated by non-spinose taxa, whereas spinose taxa prevail during summer. Across nearly all species, average monthly test size covaries with temperature, independent of seasonal flux trends. Notably, Trilobatus sacculifer and Neogloboquadrina dutertrei show a significant decline in relative abundance and flux during 2017–2020, nearly disappearing from the assemblage.

Journal of Foraminiferal Research↗

USGS2025

Insights from growing Globorotalia truncatulinoides and Globorotalia menardii in the laboratory

The vast majority of planktic foraminiferal culture studies have been carried out on spinose species of foraminifera, with relatively few studies on non-spinose species. We conducted a pilot study to test whether live specimens of the non-spinose planktic foraminifera, Globorotalia truncatulinoides and Globorotalia menardii , could be successfully harvested from offshore plankton tow samples in the Gulf of America (Gulf of Mexico) and kept alive in a laboratory at the US Geological Survey St. Petersburg Coastal and Marine Science Center. We collected several G. truncatulinoides specimens (n = 39) from the surface mixed-layer (0–80 meters) via vertical plankton tow in February 2020 during a sediment trap mooring recovery cruise. We collected G. menardii (n = 27) from the upper 200 meters of the water column on follow-up cruises in December 2021 and November 2022. The G. truncatulinoides specimens stayed alive in the laboratory for 8–76 days, and G. menardii for 7–29 days. All non-spinose foraminifera in this study showed a strong preference for eating marine snow aggregates from the plankton tow over Artemia nauplii. Using a combination of morphometric observations and geochemical analysis of the foraminiferal tests, we demonstrate that some specimens of both species grew new chambers while in culture, whereas other individuals added a calcite crust to the final whorl. The G. menardii were cultured in 87 Sr-labeled seawater, and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to verify the presence of laboratory-grown calcite. Our results shed light on the feeding behavior and growth patterns in these two upper-ocean species of non-spinose foraminifera. This study demonstrates the feasibility of conducting laboratory culture experiments with G. truncatulinoides and G. menardii collected via plankton tow in the open ocean.

Journal of Foraminiferal Research↗

USGS2022

Barium enrichment in the non-spinose planktic foraminifer, Globorotalia truncatulinoides

Observations of elevated barium-to-calcium ratios (Ba/Ca) in Globorotalia truncatulinoides have been attributed to contaminant phases, deep calcification depth and diagenetic processes. Here we investigate intra- and inter-test Ba/Ca variability in the non-spinose planktic foraminifer, G. truncatulinoides , from a sediment trap time series in the northern Gulf of Mexico to gain insights into the environmental influences on barium enrichment in this and other non-spinose species. We use laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to differentiate between the elemental composition of the crust and lamellar calcite in non-encrusted (<150 m calcification depth) and encrusted (>150 m calcification depth) specimens of G. truncatulinoides . We find that the Ba/Ca ratio in lamellar calcite is between two and three orders of magnitude higher (10–280 μmol/mol) than that of the crust (0–3 μmol/mol). We include seasonal water column profiles of the Ba/Ca ratio in the northern Gulf of Mexico and determine that the vertical gradient in seawater barium concentration cannot account for the intra-test Ba/Ca variations in G. truncatulinoides . We find the Ba/Ca ratio of the crust to be within the range observed in co-occurring spinose species of foraminifera (pink and white chromotypes of Globigerinoides ruber , and Orbulina universa ) while the range of Ba/Ca in lamellar calcite is consistent with co-occurring non-spinose foraminifera ( Pulleniatina obliquiloculata , Globorotalia menardii , G. tumida , and Neogloboquadrina dutertrei ). Our data are consistent with the hypothesis that G. truncatulinoides calcifies in a marine snow aggregate microenvironment that is enriched in barium relative to ambient seawater. We suggest that G. truncatulinoides crust is formed after the rhizopodia retract and the foraminifer detaches from its marine snow substrate.

Geochimica et Cosmochimica Acta↗

USGS2019

Considerations for Globigerinoides ruber (white and pink) paleoceanography: Comprehensive insights from a long‐running sediment trap

We present a detailed analysis of the seasonal distribution, size, morphological variability and geochemistry of co‐occurring pink and white chromotypes of Globigerinoides ruber from a high‐resolution (1–2 weeks) and long‐running sediment trap time series in the northern Gulf of Mexico. We find no difference in the seasonal flux of the two chromotypes. Although flux of G. ruber is consistently lowest in winter, the flux‐weighted signal exported to marine sediments represents mean annual conditions in the surface mixed‐layer. We observe the same morphological diversity among pink specimens of G. ruber as white. Comparison of the oxygen and carbon isotopic composition (δ 18 O and δ 13 C) of two morphotypes ( sensu stricto and sensu lato ) of pink G. rube r reveals the isotopes to be indistinguishable. The test size distribution within the population varies seasonally, with the abundance of large individuals increasing (decreasing) with increasing (decreasing) sea surface temperature (SST). We find no systematic offsets in the Mg/Ca and δ 18 O of co‐occurring pink and white G. ruber . The sediment trap data set shows that the Mg/Ca‐temperature sensitivity for both chromotypes is much lower than the canonical 9% per °C, which can likely be attributed to the secondary influence of both salinity and pH on foraminiferal Mg/Ca. Using paired Mg/Ca and δ 18 O we evaluate the performance of a suite of published equations for calculating SST, sea surface salinity (SSS) and isotopic composition of seawater (δ 18 O sw ), including a new salinity‐δ 18 O sw relationship for the northern Gulf of Mexico from water column observations.

Paleoceanography and Paleoclimatology↗

USGS2018

Environmental controls on the geochemistry of Globorotalia truncatulinoides in the Gulf of Mexico: Implications for paleoceanographic reconstructions

Modern observations of planktic foraminifera from sediment trap studies help to constrain the regional ecology of paleoceanographically valuable species. Results from a weekly-resolved sediment trap time series (2008–2014) in the northern Gulf of Mexico demonstrate that 92% of Globorotalia truncatulinoides flux occurs in winter (January, February, and March), and that encrusted and non-encrusted individuals represent calcification in distinct depth habitats. We use individual foraminiferal analysis (IFA) of G. truncatulinoides tests to investigate differences in the elemental (Mg/Ca) and isotopic composition (δ 18 O and δ 13 C) of the encrusted and non-encrusted ontogenetic forms of G. truncatulinoides , and to estimate their calcification depth in the northern Gulf of Mexico. We estimate that non-encrusted and encrusted G. truncatulinoides have mean calcification depths of 66 ± 9 m and 379 ± 76 m, respectively. We validate the Mg/Ca-calcification temperature relationship for G. truncatulinoides and demonstrate that the δ 18 O and Mg/Ca of the non-encrusted form is a suitable proxy for winter surface mixed layer conditions in the Gulf of Mexico. Care should be taken not to combine encrusted and non-encrusted individuals of G. truncatulinoides for down core paleoceanographic studies.

Marine Micropaleontology↗

USGS2016

Seasonal flux and assemblage composition of planktic foraminifera from the northern Gulf of Mexico, 2008–14

The U.S. Geological Survey anchored a sediment trap in the northern Gulf of Mexico in January 2008 to collect seasonal time-series data on the flux and assemblage composition of live planktic foraminifers. This report provides an update of the previous time-series data to include continuous results from January 2013 through May 2014. Ten taxa constituted ~95 percent of both the 2013 and 2014 assemblages: Globigerinoides ruber (pink and white varieties), Globigerinoides sacculifer , Globigerina calida , Globigerinella aequilateralis , Globorotalia menardii group [The Gt. menardii group includes Gt. menardii , Gt. tumida , and Gt. ungulata ], Orbulina universa , Globorotalia truncatulinoides , Pulleniatina spp., and Neogloboquadrina dutertrei . In 2013, the mean daily flux was 177 tests per square meter per day (m −2 day −1 ), with maximum fluxes of >1,200 tests m −2 day −1 during the middle of February and minimum fluxes of <13 tests m −2 day −1 during the beginning of November. In 2014, the mean daily flux was 189 tests m −2 day −1 , with maximum fluxes of >900 tests m −2 day −1 at the end of January and minimum fluxes of <30 tests m −2 day −1 at the beginning of January. Globorotalia truncatulinoides showed a clear preference for the winter, consistent with data from 2008 to 2012. Globigerinoides ruber (white) flux data for 2012 (average 23 tests m −2 day −1 ) were consistent with data from 2011 (average 30 tests m −2 day −1 ) and 2010 (average 29 tests m −2 day −1 ) and showed a steady threefold increase since 2009 (average 11 tests m −2 day −1 ) and a tenfold increase from the 2008 flux (3 tests m −2 day −1 ). The flux data from 2013 (average 15 tests m −2 day −1 ) and 2014 (average 8 tests m −2 day −1 ) showed decline from the previous 3 years.

Open-File Report↗

USGS2015

Lunar periodicity in the shell flux of planktonic foraminifera in the Gulf of Mexico

Synchronised reproduction offers clear benefits to planktonic foraminifera – an important group of marine calcifiers – as it increases the chances of successful gamete fusion. Such synchrony requires tuning to an internal or external clock. Evidence exists for lunar reproductive cycles in some species, but its recognition in shell flux time series has proven difficult, raising questions about reproductive strategies. Using spectral analysis of a 4-year time series (mostly at weekly resolution) from the northern Gulf of Mexico, we show that the shell flux of Globorotalia menardii , Globigerinella siphonifera , Orbulina universa , Globigerinoides sacculifer , Globigerinoides ruber (both pink and white varieties), Pulleniatina obliquiloculata , Neogloboquadrina dutertrei , Globigerinella calida and Globigerinita glutinata is characterised by lunar periodicity. However, the lunar rhythm is not present in all size fractions of each species and tends to be more dominant in the flux of larger shells, consistent with reproduction being more prevalent in larger specimens. Lunar periodicity is superimposed on longer term/seasonal changes in the shell fluxes, but accounts for a significant part of the variance in the fluxes. The amplitude of the lunar cycle increases roughly proportional with the magnitude of the flux, demonstrating that most of the population is indeed affected by lunar-phased synchronisation. In most species peak fluxes occur predominantly around, or just after, full moon. Only G. siphonifera and G. calida show a contrasting pattern with peaks concentrated around new moon. Although the exact cause of the synchronisation remains elusive, our data considerably increase the number of species for which lunar synchronised reproduction is reported and suggest that such reproductive behaviour is common in many species of planktonic foraminifera.

Biogeosciences↗

USGS2014

Weekly resolution particulate flux from a sediment trap in the northern Gulf of Mexico, 2008-2012

The U.S. Geological Survey anchored a sediment trap in the northern Gulf of Mexico to collect time-series data on sediment flux from 2008 to 2012. There are continuous measurements of total mass flux and organic carbon flux (ogC) at 7–14 day resolution from 2008 to 2012. The flux of calcium carbonate (CaCO 3 ), particulate nitrogen (nitro), and biogenic silica (Opal) were also measured from January-December, 2008. The mass flux ranged from 0.01 g m -2 day -1 (grams per square meter per day) to 2.50 g m -2 day -1 , with a mean mass flux of 0.20 g m -2 day -1 over the 5-year study period.

Gulf Of Mexico↗

USGS2013

Seasonal flux and assemblage composition of planktic foraminifera from the northern Gulf of Mexico, 2008-11

The U.S. Geological Survey anchored a sediment trap in the northern Gulf of Mexico to collect seasonal time-series data on the flux and assemblage composition of live planktic foraminifers. This report provides an update of the previous time-series data to include results from 2011. Ten species, or varieties, constituted ~92 percent of the 2011 assemblage: Globigerinoides ruber (pink and white varieties), Globigerinoides sacculifer , Globigerina calida , Globigerinella aequilateralis , Globorotalia menardii group [The Gt. menardii group includes Gt. menardii , Gt. tumida , and Gt. ungulata ], Orbulina universa , Globorotalia truncatulinoides , Pulleniatina spp., and Neogloboquadrina dutertrei . The mean daily flux was 205 tests per square meter per day (m -2 day -1 ), with maximum fluxes of >600 tests m -2 day -1 during mid-February and mid-September and minimum fluxes of <60 tests m -2 day -1 during mid-March, the beginning of May, and November. Globorotalia truncatulinoides showed a clear preference for the winter, consistent with data from 2008 to 2010. Globigerinoides ruber (white) flux data for 2011 (average 30 tests m -2 day -1 ) were consistent with data from 2010 (average 29 m -2 day -1 ) and showed a steady threefold increase since 2009 (average 11 tests m -2 day -1 ) and a tenfold increase from the 2008 flux (3 tests m -2 day -1 ).

Gulf Of Mexico↗

USGS2013

Seasonal flux and assemblage composition of planktic foraminifera from the northern Gulf of Mexico, 2008-2012

The U.S. Geological Survey anchored a sediment trap in the northern Gulf of Mexico beginning in 2008 to collect seasonal time-series data on the flux and assemblage composition of live planktic foraminifers. This report provides an update of the previous time-series data to include results from 2012. Ten species, or varieties, constituted ~92 percent of the 2012 assemblage: Globigerinoides ruber (pink and white varieties), Globigerinoides sacculifer , Globigerina calida , Globigerinella aequilateralis , Globorotalia menardii group [The Gt. menardii group includes Gt. menardii , Gt. tumida , and Gt. ungulata ], Orbulina universa , Globorotalia truncatulinoides , Pulleniatina spp., and Neogloboquadrina dutertrei . The mean daily flux was 158 tests per square meter per day (m –2 day –1 ), with maximum fluxes of >450tests m –2 day –1 during the beginning of July and mid–August and minimum fluxes of <10 tests m –2 day –1 during the beginning of February and mid–July. Globorotalia truncatulinoides showed a clear preference for the winter, consistent with data from 2008 to 2011. Globigerinoides ruber (white) flux data for 2012 (average 23 tests m –2 day –1 ) were consistent with data from 2011 (average 30 tests m –2 day –1 ) and 2010 (average 29 tests m –2 day –1 ) and showed a steady threefold increase since 2009 (average 11 tests m –2 day –1 ) and a tenfold increase from the 2008 flux (3 tests m –2 day –1 ).

Open-File Report↗

USGS2011

Seasonal flux and assemblage composition of planktic foraminifera from the northern Gulf of Mexico, 2008-2010

The U.S. Geological Survey anchored a sediment trap in the northern Gulf of Mexico to collect seasonal time-series data on the flux and assemblage composition of live planktic foraminifers. This report provides an update of the previous time-series data to include results from 2010. Ten species, or varieties, of planktic foraminifers constituted ~90 percent of the assemblage: Globigerinoides ruber (pink and white varieties), Gs. sacculifer, Globigerina calida, Globigerinella aequilateralis, Globorotalia menardii group, Gt. truncatulinoides, Pulleniatina spp., Orbulina universa, and Neogloboquadrina dutertrei. The mean daily flux was 219 tests per square meter per day (m -2 day -1 ), with maximum fluxes of >600 tests m -2 day -1 during late December and minimum fluxes of <40 tests m-2 day-1 during late August. Globorotalia truncatulinoides showed a clear preference for the winter, consistent with data from 2008 and 2009. Globigerinoides ruber (white variety) flux data for 2010 (average 29 tests m -2 day -1 ) showed a steady increase of about a factor of 3 since 2009 (average 11 tests m -2 day -1 ), and an almost 10-fold increase from the 2008 flux (average 3 tests m-2 day-1). The progressive increase in flux resulted in a relatively large increase in percent abundance of total assemblage from 2008 (1.5 percent) to 2010 (12.4 percent). In addition, though Gs. ruber (white) percent abundance increased from 4.9 percent in 2009 to over 12 percent in 2010, it continued to occur in lower abundance than the 20-30 percent indicated by dead-assemblage records from nearby sediments.

Open-File Report↗