REsearch interests
I am a micropaleontologist, and my research is fundamentally about how the oceans have changed in the past, the response of marine life to those changes, and what that can tell us about how the oceans and ocean life are changing today. The research conducted in the UT Micropaleo Lab can be split into two broad topics: 1) Holocene coastal environmental change, with the specific goal of improving federal, state, and local response to sea level rise, storm events, and other anthropogenic disruptions; and 2) research into deep-time paleoceanographic events to advance fundamental understanding of oceanographic processes and how they affect the plankton.
Our coastal change research focuses on reconstructing the Holocene evolution of modern coastal environments, and provides a range of student research and teaching opportunities focused on topics that directly affect coastal communities. Studying living foraminiferal assemblages in modern coastal settings also provides important baselines for observing ongoing ecological disruptions. Our deep-time research is fundamentally motivated by a desire to understand how plankton respond to changes in their environment. This work spans the Cretaceous to the Recent, with particular focus on Cretaceous Oceanic Anoxic Events (OAEs), the Cretaceous-Paleogene (K-Pg) mass extinction, and Cenozoic climate transitions (particularly the Eocene-Oligocene transition). A recent review paper in Annual Reviews of Earth and Planetary Science (Lowery et al., 2020) on the response of plankton to the major climatic events of the last 150 million years summarizes this topic in far more detail than is possible here, but basically each of these unique paleoceanographic events was characterized by different disruptions to the marine environment (anoxia, acidification, temperature change, etc.) and by studying which groups went extinct and which didn’t during each event we can build a holistic understanding of extinction risk. This paper lays out a number of key unanswered questions for each event, and the UT Micropaleo Lab’s research program is built around trying to answer these questions.
Our coastal change research focuses on reconstructing the Holocene evolution of modern coastal environments, and provides a range of student research and teaching opportunities focused on topics that directly affect coastal communities. Studying living foraminiferal assemblages in modern coastal settings also provides important baselines for observing ongoing ecological disruptions. Our deep-time research is fundamentally motivated by a desire to understand how plankton respond to changes in their environment. This work spans the Cretaceous to the Recent, with particular focus on Cretaceous Oceanic Anoxic Events (OAEs), the Cretaceous-Paleogene (K-Pg) mass extinction, and Cenozoic climate transitions (particularly the Eocene-Oligocene transition). A recent review paper in Annual Reviews of Earth and Planetary Science (Lowery et al., 2020) on the response of plankton to the major climatic events of the last 150 million years summarizes this topic in far more detail than is possible here, but basically each of these unique paleoceanographic events was characterized by different disruptions to the marine environment (anoxia, acidification, temperature change, etc.) and by studying which groups went extinct and which didn’t during each event we can build a holistic understanding of extinction risk. This paper lays out a number of key unanswered questions for each event, and the UT Micropaleo Lab’s research program is built around trying to answer these questions.
Ongoing projects
Holocene Environmental Change and Sand Resources on the Texas Shelf
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Lab members are part of several projects funded by the Bureau of Ocean Energy Management (BOEM) and the Texas General Land Office (GLO) to study buried sand resources offshore Galveston, Texas. BOEM and GLO are currently undertaking an assessment of all the buried sand resources on the Gulf of Mexico Continental Shelf, and where sand is commonly found in drowned Pleistocene incised valleys. The goal of these projects is to map sand resources for future use in coastal projects but the data we collect also allows us to study Holocene environmental and sea level changes. Collaborating with other scientists at UTIG, we take a systems approach to identifying sand resources, reconstructing overall environmental change in the drowned river valley with a mix of seismic data, sedimentology, and micropaleontology to map environments where sand is present. Benthic foraminifera are excellent proxies for depositional environments in estuaries and on the inner shelf. This work has also allowed us to understand how estuaries on the Texas coast responded to changing rates of Holocene sea level rise.
URA Patty Standring used foraminifera to reconstruct paleoenvironmental change tied to sea level rise in the Holocene Trinity estuary offshore modern Galveston TX in work currently in revision of Marine Geology (preprint). Graduate student Solveig Schilling is continuing the work in by conducting a census of living foraminifera on the modern seafloor and then comparing them to ancient assemblages from new cores around the modern ebb tide delta offshore Galveston Bay. |
Coring cruises offshore Galveston TX
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Eocene-Oligocene Ocean Circulation
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The Eocene-Oligocene transition marks the first step in the progressive cooling of the latter half of the Cenozoic, a major reorganization of global ocean circulation, and a major extinction of foraminifera, both planktic and benthic. To better understand how climate and oceanography changed, and why that drove extinction in the plankton, we are engaged in a number of related projects. An upcoming cruise on the Mexican research ship Justo Sierra, funded by a NSF award to Chris Lowery and supported by UNAM, will image sediment drifts in the southeastern Gulf of Mexico where North Atlantic Deep Water spills into the basin, and then tie that geophysical data to proxy data from old Deep Sea Drilling Project cores in this area. This will serve as both a site survey cruise for the IODP and an opportunity to generate high resolution geophysical images of sediment drifts and unconformities to constrain changes in circulation through this gateway. We are particularly interested in the timing of the onset of modern(ish) deep water flow into the Gulf, which we hypothesize began in the late Eocene.
A related investigation of Eocene-Oligocene deep water circulation changes in the South Atlantic will focus on new cores collected on IODP Expedition 390 April-June 2022, on which Chris Lowery is a shipboard biostratigrapher. These new cores, combined with legacy ocean drilling cores from the Gulf of Mexico and the Caribbean, form the basis of Patty Standring’s PhD project, investigating E-O circulation changes and related extinction in planktic and benthic foraminifera. Recovery of Plankton Ecosystems after the End Cretaceous Mass ExtinctioN
Phytoplankton, which produce energy from sunlight and carbon dioxide, represent the base of the marine food webs and are a critical part of the carbon cycle. In the modern ocean, plankton communities are beginning to shift due to warming and ocean acidification. To understand the long-term effects of such changes on the larger ocean ecosystem it is necessary to look to periods of change in the geologic past. This paleo work has generally been limited to studies of plankton which produce hard shells which leave a physical fossil record. In the modern ocean, plankton which can leave a fossils represent just a fraction of total ocean biomass, which means the fossil record is just a partial view of ancient plankton ecosystems. This project, a collaboration with biogeochemist Julio Sepúlveda at University of Colorado, will overcome this limitation by using chemical fossils called biomarkers in conjunction with traditional physical fossils to reconstruct changes in the composition of the marine plankton community following the Cretaceous-Paleogene (K-Pg) mass extinction. Calcareous nannoplankton were one of the dominant primary producers in the Cretaceous ocean, but 93% of species of this group went extinct at the K-Pg boundary, and they were never again as dominant in the Cenozoic ocean. It has often been assumed that non-fossilizing phytoplankton (chlorophyte algae, cyanobacteria, etc.) filled the gap left by the decline in calcareous nannoplankton, but has not actually been tested. Understanding how primary productivity recovers after mass extinctions is central to reconstructing the recovery of the whole ecosystem. A number of recent studies have built an increasingly sophisticated picture of the role of primary producers in the aftermath of the K-Pg mass extinction and the recovery of the biological pump, which facilitates the downward transport of organic carbon and plays a key role in the carbon cycle. This previous work has all focused on fossilizing plankton and geochemical reconstruction of export production; this study, funded by a NSF grant to Chris Lowery, integrates new biomarker data with traditional microfossil data to fill in the critical link between these two key systems to determine how changes in plankton ecology could lead to the observed changes in the biological pump. We are working to develop datasets of organic biomarkers, calcareous nannoplankton, and planktic foraminifera from 5 sites in Tunisia, Spain, and the US Gulf Coast. Three sites in Tunisia (El Kef, Elles, and El Melah) represent a depth transect on a continental shelf (paleodepths of 200-500 m), Caravaca represents deeper water (~600-1000 m), while Brazos represent a shallow shelf which will allow us to test regional variability between north Africa and the US Gulf Coastal Plain.
Cretaceous Oceanic Anoxic Event 2 on the US Gulf and Atlantic Coastal PLainsCretaceous Oceanic Anoxic events represent major perturbations of the global carbon cycle and drove significant turnover in plankton ecosystems. Although this events are well studied in the deep sea and in the Western Interior US, but they are surprisingly understudied on continental margins. This is surprising because in the modern ocean (and apparently in the Cretaceous) the majority of organic carbon burial occurs on the shelf, and this is the region most affected by changing oxygen minimum and seasonal anoxia. The modern oceans are losing oxygen at roughly the same rate as the Cretaceous oceans did prior to Oceanic Anoxic Event 2, and while the global circulation system will not allow widespread anoxia to develop now like it did then, understanding how continental margins (and their endemic biota) respond to such changes is very important. We have been working with collaborators, principally at the US Geological Survey, to develop new records of OAE2 across the Gulf and Atlantic coastal plains. More and more sites will eventually allow us to develop a detailed understanding of how the expression of OAE2 varied across the shelf, and why.
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Research ship Justo Sierra
Racemiguembelina fructicosa from the latest Cretaceous at El Kef, Tunisia
The K-Pg boundary layer at Darting Minnow Creek just off the Brazos River in Texas. Hammer is laying on cross-bedded sandstone deposited by the impact-generated tsunami.
Sun Spinks core (Mississippi) laid out at the Texas Bureau of Economic Geology (see Lowery et al., 2017).
Organic carbon isotopes, total organic carbon, and carbon/nitrogen ratios from two cores on the North Carolina Coastal Plain (Lowery et al., 2021).
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Past Projects
Recovery of Life in the Chicxulub Crater
he lab’s work on the K-Pg mass extinction dates back to when Chris Lowery (then a lab of one) sailed on IODP Expedition 364 to the Chicxulub Crater in 2016. This work has made important advances in our understanding how the plankton ecosystem recovered in the immediate aftermath of the mass extinction (Lowery et al., 2018, 2021; Nature; Jones et al., 2019, Geology; Bralower et al., 2020a, AGU Advances; Bralower et al., 2020b, EPSL; and Rodriguez-Tovar et al., 2020 Geology) and what that tells us about the fundamental evolutionary processes that govern recovery after rapid events (Lowery and Fraass, 2019 Nature Ecology and Evolution). Micropaleo’s central contribution to this project, (Lowery et al., 2018) show that life appeared in the Chicxulub crater just years after the impact, and that a healthy, high-productivity ecosystem was established within 30 kyr, much sooner than other North Atlantic and Gulf of Mexico sites. This clearly shows that there was no geographic (and thus environmental) control on duration of the recovery of productivity, as had been predicted, and instead suggests an ecological control, like incumbency or competitive exclusion.
We’ve been following up on this initial result in several ways. Building on this work, Lowery and Fraass looked at the longer-term recovery of diversity, which is delayed 10 myr after the boundary (as it turns out, this is a common feature of mass extinctions for which there were some untested hypotheses but no firm explanation). Using a morphometric dataset that Andy had developed, we examined the reconstruction of planktic foraminifer morphospace (which we consider to be equivalent to ecospace, i.e., ecological niche occupation) through the Paleocene and early Eocene, and show that the time it takes to rebuild morphospace provides an explanation for the delay in the recovery of diversity. This need to reconstruct ecospace provides a firm speed limit on the recovery of diversity after a mass extinction event. Additional data from the Expedition 364 cores revealed that export productivity in the Chicxulub Crater was high for ~ 300 kyr after the K-Pg boundary, and then declined (Lowery et al., 2021); the final decline in export is associated with turnover in the calcareous nannoplankton assemblage, suggesting a relationship between the recovery of export production and the recovery of phytoplankton diversity (Jones et al., 2019). Additional work on other K-Pg cores around the Gulf of Mexico and Caribbean shows that the period of high export production and the subsequent decline were coeval across this region indicating that despite global heterogeneity in export production in the early Paleocene, trends were homogenous at a regional level (Lowery et al., 2021 EarthArXiv preprint). |
Planktic foraminfera from sediments deposited <30,000 years after the Chicxulub impact.
IODP Expedition 364 Science Party, in Bremen.
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