Patterns and processes in the history of body size in turritelline gastropods, Jurassic to Recent

Body size is an important trait with implications for energy use and ecology as well as generation time and evolutionary rates. Turritelline gastropods are widely distributed through geologic time and space, making them an excellent group for evaluating macroevolutionary patterns. To evaluate the pattern of body-size change in turritelline gastropods, we compiled a dataset of shell lengths of 316 species of turritelline gastropods spanning the Jurassic to Recent. Type specimens were almost always significantly larger than specimen distributions from the same species. We found that turritelline gastropod size was inversely correlated with latitude, a trend likely driven by the Neogene-Recent diversification of small-bodied Southern Hemisphere taxa. A time series model was applied to distinguish among three possible macroevolutionary patterns: unbiased random walk (no directional trend), biased random walk (directional trend), and stasis (no net change). We determined that turritelline gastropods have experienced stasis in body size throughout their evolutionary history, adding to the growing literature documenting directionless body-size trends in marine invertebrate clades. Stasis of geographically widespread clades may be the result of ecological variability across the environmental range occupied by the group or differential diversification into opposing environments. Turritelline life-history patterns, especially their reproductive strategy that combines a short life span and decline in growth rate around 1 year of age to reallocate energy to reproduction, might circumvent selection for longevity and larger size, while further decrease in minimum size is likely limited by feeding efficiency and anti-predatory defense. The expectation that species or clades should continue to evolve to occupy larger size classes conflicts with the evolutionary advantages of small size, which in turritelline gastropods include high generational turnover and larger population sizes that yield opportunities for genetic variance

Biotic impacts of temperature before, during, and after the end-Permian extinction: A multi-metric and multi-scale approach to modeling extinction and recovery dynamics

Extinction and delayed recovery during the end-Permian extinction and Early Triassic has been linked to environmental instability brought on by volcanic outgassing and greenhouse conditions, but the relative importance of the myriad of environmental stressors at this time on recovery dynamics is not well understood. Previous workers have documented both overall delayed biotic recovery for the entirety of the Early Triassic, but also incipient recoveries that appear to occur relatively early after the initial extinction event. Here, we explore the patterns of extinction and recovery using several metrics of ecological complexity in marine benthic communities using a global dataset, and compare several multiple regression models to determine which set of abiotic factors best predicts extinction and recovery dynamics. We additionally test the importance of temporal scale of analysis in interpretations of recovery dynamics and modeling results, by including analyses at the epoch, stage, and substage scales bracketing the interval of extinction and recovery. We find differences in mode of recovery between the ecological metrics analyzed, with some metrics exhibiting an Early Triassic recovery lag, while others recover continuously or immediately following the initial extinction event. We also find evidence of a global ‘Dienerian minimum’, with overall levels of community complexity significantly lower than earlier Griesbachian communities, suggesting a synchronous disturbance to the progression of recovery at this time. The regression model with δ18Oapatite mean values as the response variable is most often found to be the best-fit model across all time scales analyzed, though proxies of rock record fidelity and paleontological sampling effort become more important in finer timescale analyses, likely due to dwindling sample numbers. Out of the models tested, these results suggest that global ocean temperatures best predict patterns of extinction and recovery across several ecological metrics, and that thermal episodes during the initial extinction event and subsequently in the Early Triassic recovery period significantly suppressed benthic marine community health

Variation in Carbonate Chemistry throughout the San Juan Archipelago

Due to the dynamic nature of the water masses in the San Juan archipelago, the carbonate chemistry has not yet been well defined in space and time. For this short-term study during a neap to spring tidal cycle in mid July 2011, we analyzed water samples as far west as Kellett Bluff and as far east as East Sound for dissolved inorganic carbon (DIC), total alkalinity (TA), temperature, and salinity at depths of 10 meters. As expected, we found variability across space and time that may be in part explained by a freshwater signal from the Fraser River, differences in flow and flushing rates, the physical geography and the resultant estuarine and ocean circulation. With continued and more expansive sampling, this data will have pertinence for the larger and future dialogue about ocean acidification in coastal environments

Variation of environmental forcings and the potential for changes in carbonate chemistry of the San Juan Archipelago

The carbonate chemistry of the San Juan Archipelago is extremely varied between regions of low to high tidal flushing. Salinity seems to be a driving parameter of the carbonate system through its effects on alkalinity. Freshwater from the Fraser River may control the environmental characteristics of water moving through the archipelago. In areas of low flushing, biological effects may strongly influence the carbonate chemistry. The effects of upwelling, especially on the west side are understudied. Overall, the water of the different sounds, channels, and straits of the islands are exchanged and equilibrated by mixing during strong spring tides. It is important to understand the interplay between environmental and biological controllers of carbonate chemistry to interpret changes that may be observed with the advent of ocean acidification

Spatial and Temporal Variability in Carbonate Chemistry in San Juan Archipelago

This is the first study that characterizes the carbonate parameters in the Salish Sea surrounding the San Juan Archipelago. Water samples were collected from 9 sites on multiple days and analyzed for total alkalinity and dissolved inorganic carbon. Results show high spatial and temporal variability in carbonated parameters. Levels of pCO2 roughly fluctuated between 400 and 950 μatm. The sites are likely highly influenced by freshwater pulses and tidal exchanges. Stark differences between areas of hypothesized high and low water retention were not observed within this sampling scheme

Little lasting impact of the Paleocene-Eocene Thermal Maximum on shallow marine molluscan faunas

Global warming, acidification, and oxygen stress at the Paleocene-Eocene Thermal Maximum (PETM) are associated with severe extinction in the deep sea and major biogeographic and ecologic changes in planktonic and terrestrial ecosystems, yet impacts on shallow marine macrofaunas are obscured by the incompleteness of shelf sections. We analyze mollusk assemblages bracketing (but not including) the PETM and find few notable lasting impacts on diversity, turnover, functional ecology, body size, or life history of important clades. Infaunal and chemosymbiotic taxa become more common, and body size and abundance drop in one clade, consistent with hypoxia-driven selection, but within-clade changes are not generalizable across taxa. While an unrecorded transient response is still possible, the long-term evolutionary impact is minimal. Adaptation to already-warm conditions and slow release of CO2 relative to the time scale of ocean mixing likely buffered the impact of PETM climate change on shelf faunas

Evolutionary models in the Early Triassic marine realm

The relative influences of extrinsic compared to intrinsic drivers of evolutionary change have long been theorized and debated in the fossil record. Ecological recoveries from mass extinction events present records in which to examine these contrasts. Competition in a low diversity world, reproductive strategy, reconstruction of trophic systems and ecological specialization represent possible intrinsic controls on diversification. Feedback between diversity and abundance shifts of marine organisms with biogeochemical cycling and environmental conditions act as extrinsic controls on recovery process and rate. Disentangling these evolutionary pressures is a major challenge for understanding evolutionary recovery from mass extinction.The end-Permian mass extinction (251.88 Ma) represents the largest mass extinction in Earth history and led to an extended recovery interval which lasted the duration of the Early Triassic (~ 4.8 Myr) and beyond. Recent analyses suggest that the survivors of the mass extinction were biased toward organisms with higher metabolic rates that were more resilient against the volatile environmental changes that pervaded the Early Triassic including extreme temperature events, low pH, and low oxygen conditions. We use the Early Triassic recovery of gastropods, echinoids, and ammonoids to examine the processes of taxonomic and ecological evolution in response to, or in spite of, extrinsic environmental perturbations.The case studies of benthic gastropods and echinoids, when compared to pelagic ammonoids reflect similarities and differences in recovery following the end-Permian mass extinction. Gastropods and echinoids exhibit evidence of strong extrinsic environmental limitations which implicate the availability of refugia as a control on recovery. Low initial taxonomic diversity of survivors may have also limited the evolutionary recovery of both clades. Abundant and diverse microgastropod assemblages are interpreted as an adaptation to extreme environmental conditions. The morphological diversity of disarticulated echinoid spines and plates described in the southwestern United States, and examination of phylogenetic ghost lineages hints at a significant “hidden diversity” of Early Triassic echinoids. Ammonoids experienced taxonomic resets but are shown to be resilient to repeated environmental perturbations in the Boreal Ocean over the duration of the Early Triassic. Ammonoids may have adapted to persistent latitudinal temperature gradients and oxygen minimum zones that developed in the Early Triassic ocean basins

Carbonate chemistry of the San Juan Archipelago: A baseline field study for future ocean acidification research

Natural variability in the carbonate system is difficult to control in the lab. Furthermore, environmental carbonate chemistry data over small spatial scales is lacking. We measured discrete water samples across various flushing regimes in the San Juan Archipelago every other day during low slack tide over one neap to spring tidal transition. After analyzing these samples for temperature, salinity, total alkalinity and dissolved inorganic carbon, we plotted these variables across space and time. Our data suggest that although carbonate chemistry varies through space and time, biological processes and tidal cycles may have a significant influence on the local marine chemistry. Our study aims to inform those interested in ocean acidification research about the natural variation of various carbonate system parameters in the San Juan Archipelago

Leveraging a Community of Practice to Build Faculty Resilience and Support Innovations in Teaching during a Time of Crisis

Amidst the COVID-19 upheaval to higher education, a grantor-led community of practice (CoP) supported faculty members to deliver an innovative, sustainability-oriented entrepreneurship curriculum and maintain resiliency as teaching professionals. This paper discusses how through engagement in the CoP, this group of faculty from across engineering, material science, business, and geosciences demonstrated resilience, adaptability, and pivoted to create curriculum for students in real time, as the events of the COVID-19 pandemic unfolded throughout 2020 and impacted face-to-face learning. The role the community of practice played in sustaining and supporting the faculty will be discussed. Case studies from faculty members will demonstrate how sustainable design and social responsibility can be integrated into entrepreneurially focused classes and student experiences across disciplines. The primary contribution of this research is the important role that an emergent learning framework can play in informing how best to optimize the CoP format and approach in a way that leverages and addresses individual member strengths, challenges, and experiences, and supports the needs of CoP members during a time of significant change and crisi

Investigating the Paleoecological Consequences of Supercontinent Breakup: Sponges Clean Up in the Early Jurassic

The continued release of fossil fuel carbon into the atmosphere today means it is imperative to understand Earth system response to CO2 rise, and the geologic record offers unique opportunities to investigate such behavior. Stomatal and paleosol proxies demonstrate a large change in atmospheric pCO2 across the Triassic-Jurassic (T-J) transition, concomitant with the eruption and emplacement of the Central Atlantic Magmatic Province (CAMP) and the splitting of Pangea. As one of the “big 5” mass extinctions—when the so-called modern fauna was particularly hard hit—we know the biosphere was severely affected during this time, but the details are relatively poorly understood, particularly with respect to an Earth system perspective. As part of the NSF Earth Life Transitions initiative, our team has targeted the T-J for integrative investigation to explore, among other things, alternative ecological states that may exist in the aftermath of mass extinctions. The initial findings reveal a global “sponge takeover” in the Early Jurassic following the extinction that lasted nearly 2 million years. The sponge takeover may be linked to an unusual confluence of factors, including potential ocean acidification and intense silicate weathering following the emplacement of CAMP