Climate Commons^™

Engagement In Practice: Partnering With Communities To Address Nuisance Flooding Challenges, Carol L. Considine, Mujde Erten-Unal, Dalya Ismael, Luka Alandra Hamal-Serenity, Farzaneh Soflaei

Engineering Technology Faculty Publications

Many communities are already experiencing the impacts of climate change that disrupt their daily lives. In Coastal Virginia, these impacts take the form of nuisance and stormwater flooding caused by sea level rise and changes in precipitation. Coastal Virginia has one of the highest relative sea level rise rates on the Atlantic Coast and the regional planning district commission recommends that Atlas 14 rainfall intensity, duration, and frequency curves be increased by 20% to account for changes in rainfall. The Coastal Community Design Collaborative (CCDC), a partnership between Hampton University Architecture and Old Dominion University Engineering & Technology, has had …

Sustainable Management Of Erosive Shores: An Interdisciplinary Approach Integrating Engineering And Social Sciences At A Tide-Dominant Beach Area, Jun Ik Sohn, Hyun Dong Kim, Kiran Adhithya Ramakrishnan

Civil & Environmental Engineering Faculty Publications

This study investigates the causes and consequences of shoreline erosion at Kkotji Beach, a prominent tourist destination on the west coast of South Korea, where the degradation of the coastal environment has increasingly threatened the local tourism industry and economy, by employing a mixed-methods approach that combines field observations with MIKE 21 hydrodynamic simulations and by integrating perspectives from coastal engineering and the social sciences to develop practical, site-specific strategies for mitigating erosion, enhancing public awareness, and promoting sustainable coastal planning and development that support long-term environmental resilience and economic stability. The results show that dominant ebb currents drive southward …

High Temporal Resolution Gene Expression Analysis Of Acute Heat Stress Response In Acropora Cervicornis And Porites Astreoides, Katherine Parker, Nicolas Evensen, Iliana Baums, Daniel Barshis

Biological Sciences Faculty Publications

Widespread coral bleaching and mortality events are becoming increasingly frequent due to rising ocean temperatures, though certain coral species and populations have displayed higher tolerance to elevated emperatures than others. As such, it is of high research priority to identify thermally tolerant coral populations for research and conservation and assess the biological mechanisms allowing these populations to survive exposure to higher temperatures. This research utilized the Coral Bleaching Automated Stress System (CBASS), a portable experimental aquaria system with precise temperature manipulation, to assess the thermal thresholds and heat stress response of two coral species from Summerland Key, FL, USA. Seven …

Symbiodiniaceae Shifts Over The Last Decade On The Hottest Coral Reefs On Earth, Anna Fiesinger, Rachel Alderdice, Luigi Colin, Hannah Manns, Gabriela Perna, Kathryn H. Stankiewicz, Jacob J. Valenzuela, Line K. Bay, Daniel J. Barshis, Nitin S. Baliga, Iliana B. Baums, John A. Burt, Christian R. Voolstra

Biological Sciences Faculty Publications

Corals in the Persian/Arabian Gulf (PAG) are resilient to various stressors, whose levels exceed those of coral reefs globally. These corals thereby offer insight into mechanisms underlying thermal resilience, e.g., regarding the role of endosymbiotic microalgae in the family Symbiodiniaceae. Previous studies have identified the thermotolerant species Cladocopium thermophilum as broadly associated with corals in the southern PAG. However, algal-host specificity at the within-species level and the temporal stability of these associations are not well understood. Here we sampled two dominant stony corals (Porites harrisoni, n = 119 and Platygyra daedalea, n = 79) at three sites …

Seasonal Variability Of Surface Ocean Carbon Uptake And Chlorophyll-A Concentration In The West Antarctic Peninsula Over Two Decades, Jessica S. Turner, David R. Munro, Amanda Fay, Sharon Stammerjohn, Heather Kim, Oscar Schofield, Heidi Dierssen

OES Faculty Publications

The Southern Ocean plays a vital role in global CO₂ uptake, but the magnitude and even the sign of the flux remain uncertain, and the influence of phytoplankton phenology is underexplored. This study focuses on the West Antarctic Peninsula, a region experiencing rapid climate change, to examine shifts in seasonal carbon uptake. Using 20 years of in situ air-sea CO₂ flux and satellite-derived Chlorophyll-a, we observe that the seasonal cycles of both air-sea CO₂ flux and Chlorophyll-a intensify poleward. The amplitude of the seasonal cycle of the non-thermal component of surface ocean pCO₂ increases with increasing latitude, while the amplitude …

Atmospheric Chemistry Experiment (Ace) V.5.3 Winds: Validation And Model Comparisons, Matthew Wyatt, Peter F. Bernath, Chris Boone, Leo Lavy, Ryan Johnson

Physics Faculty Publications

The Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) uses limb geometry to measure transmittance spectra of Earth's atmosphere by solar occultation. Line-of-sight wind speeds can be derived via Doppler shifts of molecular lines in infrared spectra. The wind look direction angles relative to geodetic north are derived from geometry. We validate the new ACE version 5.3 (v.5.3) line-of-sight winds with MIGHTI and meteor radar vector wind observations and find a -15 m s^-¹ (+15 m s^-¹) sunrise (sunset) shift above 80 km. We also compare line-of-sight winds from ACE-FTS v.5.2 and v.5.3 with vector winds from …

Estimating The Economic Impact Of A Natural Disaster On The Workforce Resiliency: An Analysis Of The Virginia Beach - Chesapeake - Norfolk Metropolitan Statistical Area, Robert M. Mcnab, Yin-Hsuen Chen, George Mcleod

Presentations, Lectures, Posters, Reports

In this paper, we explore the potential economic impacts associated with a major hurricane making landfall in Hampton Roads. We estimate the direct damages from a Florence-like Category 3 hurricane with a 3.6 feet tidal offset are estimated at $15.6 billion, equivalent to 10% of the 2022 regional GDP. If we apply existing flood insurance rates to these projected damages, we estimate that the total economic impact would exceed $12 billion with a short-term loss of more than 76,000 jobs. The job losses are concentrated in sectors that provide services to households which would bear the brunt of damages during …

Simulating The Compound Impacts Of Climate Change And Sea-Level Rise On Coastal Shallow Groundwater Using An Integrated Surface-Subsurface Hydrologic Model, Zhaoyi Cai

Civil & Environmental Engineering Theses & Dissertations

As climate change intensifies and sea levels rise, coastal aquifers become increasingly vulnerable to interacting oceanic and terrestrial processes. This dissertation examines the combined impacts of climate change and sea-level rise (SLR) on coastal shallow groundwater using an integrated surface-subsurface hydrologic model, focusing on the low-lying Little Creek watershed (LCW) in Norfolk, Virginia. The SWAT-MODFLOW model, a coupled system, unifies land surface, streamflow, and groundwater processes, providing a comprehensive framework for watershed-aquifer analysis. Model parameters were derived from U.S. Geological Survey datasets, relevant literature, station records, and technical reports, followed by meticulous calibration. The validated model first simulated baseline groundwater …

Impact Of Climate Change On Carbon And Nitrogen Balance In Zostera Marina L. (Eelgrass), Malee Jinuntuya

OES Theses and Dissertations

Seagrasses face vulnerability to both global stressors like Ocean Acidification (OA) and climate warming compounded by local stressors such as eutrophication that reduces light availability, leading to a complex dynamic of positive and negative effect on their growth and survival. Increased dissolved aqueous CO₂ (CO_2(aq)) benefits seagrasses by enhancing photosynthetic and growth rates, but it may increase nutrient demand, potentially depleting nutrient supply, especially in oligotrophic environments.

In this study, the long-term impact of CO₂ on Zostera marina L. (eelgrass) were investigated across a gradient of CO_2(aq) concentrations (55 – 2200 µM CO_{2(aq)) …}

Coastal Hazards, Emergency Management, Resilience, And Equity: Issues And Concerns At The Intersection Of Research And Practice, Wie Yusuf, Marina Saitgalina, Oge Nwandu-Vincent, Joshua Behr, Jennifer Whytlaw, Nicole Hutton, Tom Allen, Khairul Anuar

School of Public Service Faculty Publications

No abstract provided.

Trust And Contexts: A Conceptual Framework For Understanding Coastal Household Preparedness, Ogechukwu M. Agim Nwandu-Vincent

School of Public Service Theses & Dissertations

Despite research findings that show the benefits of being prepared for increasingly tumultuous natural and coastal hazard events, studies on hazard preparedness indicate that low levels of preparedness may occur in vulnerable areas due to the uncertainty around hazard risks, expected hazard onset and impact strength, as well as associated effects. Study findings indicate that trust may impact the uncertainty and complexity faced by people dealing with unfamiliar, infrequent, and complex hazards, as well as contexts such as factors such as age, gender, prior hazard experience, and homeownership.

While studies have looked at the relationship between trust and compliance (desired …

Last Millennium Hurricane Activity Linked To Endogenous Climate Variability, Wenchang Yang, Elizabeth Wallace, Gabriel A. Vecchi, Jeffrey P. Donnelly, Julien Emile-Geay, Gregory J. Hakim, Larry W. Horowitz, Richard M. Sullivan, Robert Tardif, Peter J. Van Hengstum, Tyler S. Winkler

OES Faculty Publications

Despite increased Atlantic hurricane risk, projected trends in hurricane frequency in the warming climate are still highly uncertain, mainly due to short instrumental record that limits our understanding of hurricane activity and its relationship to climate. Here we extend the record to the last millennium using two independent estimates: a reconstruction from sedimentary paleohurricane records and a statistical model of hurricane activity using sea surface temperatures (SSTs). We find statistically significant agreement between the two estimates and the late 20th century hurricane frequency is within the range seen over the past millennium. Numerical simulations using a hurricane-permitting climate model suggest …

The Impacts Of Anthropogenic Activity And Climate Change On The Formation Of Harmful Algal Blooms (Habs) And Its Ecological Consequence, Zhangxi Hu, Aifeng Li, Zhun Li, Margaret R. Mulholland

OES Faculty Publications

No abstract provided.

Nitrogen Fixation At The Mid-Atlantic Bight Shelfbreak And Transport Of Newly Fixed Nitrogen To The Slope Sea, C. R. Selden, M. R. Mulholland, K. E. Crider, S. Clayton, A. Macías-Tapia, P. Bernhardt, D. J. Mcgillicuddy Jr., W. G. Zhang, P. D. Chappell

OES Faculty Publications

Continental shelves contribute a large fraction of the ocean's new nitrogen (N) via N₂ fixation; yet, we know little about how physical processes at the ocean's margins shape diazotroph biogeography and activity. Here, we test the hypothesis that frontal mixing favors N₂ fixation at the Mid-Atlantic Bight shelfbreak. Using the ¹⁵N₂ bubble release method, we measured N₂ fixation rates on repeat cross-frontal transects in July 2019. N₂ fixation rates in shelf waters (median = 5.42 nmol N L⁻¹ d⁻¹) were higher than offshore (2.48 nmol N L⁻¹ d⁻¹) …

Integrating Climatological-Hydrodynamic Modeling And Paleohurricane Records To Assess Storm Surge Risk, Amirhosein Begmohammadi, Christine Y. Blackshaw, Ning Lin, Avantika Gori, Elizabeth Wallace, Kerry Emanuel, Jeffrey P. Donnelly

OES Faculty Publications

Sediment cores from blue holes have emerged as a promising tool for extending the record of long-term tropical cyclone (TC) activity. However, interpreting this archive is challenging because storm surge depends on many parameters including TC intensity, track, and size. In this study, we use climatological-hydrodynamic modeling to interpret paleohurricane sediment records between 1851 and 2016 and assess the storm surge risk for Long Island in The Bahamas. As the historical TC data from 1988 to 2016 is too limited to estimate the surge risk for this area, we use historical event attribution in paleorecords paired with synthetic storm modeling …

Nitrogen Uptake Rates And Phytoplankton Composition Across Contrasting North Atlantic Ocean Coastal Regimes North And South Of Cape Hatteras, Yifan Zhu, Margaret R. Mulholland, Peter W. Bernhardt, Aimee Renee Neeley, Brittany Widner, Alfonso Macías Tapia, Michael E. Echevarria

OES Faculty Publications

Understanding nitrogen (N) uptake rates respect to nutrient availability and the biogeography of phytoplankton communities is crucial for untangling the complexities of marine ecosystems and the physical, biological, and chemical forces shaping them. In the summer of 2016, we conducted measurements of bulk microbial uptake rates for six ¹⁵N-labeled substrates: nitrate, nitrite, ammonium, urea, cyanate, and dissolve free amino acids across distinct marine provinces, including the continental shelf of the Mid-and South Atlantic Bights (MAB and SAB), the Slope Sea, and the Gulf Stream, marking the first instance of simultaneously measuring six different N uptake rates in this dynamic region. …

An Inconsistent Enso Response To Northern Hemisphere Stadials Over The Last Deglaciation, Ryan H. Glaubke, Matthew W. Schmidt, Jennifer E. Hertzberg, Lenzie G. Ward, Franco Marcantonio, Danielle Schimmenti, Kaustubh Thirumalai

OES Faculty Publications

The dynamics shaping the El Niño-Southern Oscillation's (ENSO) response to present and future climate change remain unclear, partly due to limited paleo-ENSO records spanning past abrupt climate events. Here, we measure Mg/Ca ratios on individual foraminifera to reconstruct east Pacific subsurface temperature variability, a proxy for ENSO variability, across the last 25,000 years, including the millennial-scale events of the last deglaciation. Combining these data with proxy system model output reveals divergent ENSO responses to Northern Hemisphere stadials: enhanced variability during Heinrich Stadial 1 (H1) and reduced variability during the Younger Dryas (YD), relative to the Holocene. H1 ENSO likely intensified …

Integrating Climatological-Hydrodynamic Modeling And Paleohurricane Records To Assess Storm Surge Risk, Amirhosein Begmohammadi, Christine Y. Blackshaw, Ning Lin, Avantika Gori, Elizabeth Wallace, Kerry Emanuel, Jeffrey P. Donnelly

OES Faculty Publications

Sediment cores from blue holes have emerged as a promising tool for extending the record of long-term tropical cyclone (TC) activity. However, interpreting this archive is challenging because storm surge depends on many parameters including TC intensity, track, and size. In this study, we use climatological-hydrodynamic modeling to interpret paleohurricane sediment records between 1851 and 2016 and assess the storm surge risk for Long Island in The Bahamas. As the historical TC data from 1988 to 2016 is too limited to estimate the surge risk for this area, we use historical event attribution in paleorecords paired with synthetic storm modeling …

4500-Year Paleohurricane Record From The Western Gulf Of Mexico, Coastal Central Tx, Usa, Sarah B. Monica, Davin J. Wallace, Elizabeth J. Wallace, Xiaojing Du, Sylvia G. Dee, John B. Anderson

OES Faculty Publications

Texas receives the second-highest number of tropical cyclone (TC) landfalls per year in the United States. At present, long-term TC projections from climate models remain uncertain due to the short and biased nature of Atlantic TC observations. Sediment archives of past storms can help extend the observational record of TC strikes over the past few millennia. When a TC makes landfall along the central Texas coast, coastal downwelling channels and storm currents transport and deposit coarse sediment to a zone of rapid accumulation along the shelf, known as the Texas Mud Blanket (TMB). This “backwash” process results in expansive storm …

A Proxy System Modeling Approach To Combining Tree-Ring And Sediment-Based Paleotempestological Records, Elizabeth J. Wallace, Sylvia Dee, Joshua Bregy, Kerry A. Emanuel

OES Faculty Publications

The short and biased observational record of tropical cyclones (TCs) limits scientific understanding of how these destructive storms respond to climate forcing. Paleohurricane records use natural archives (tree rings, coarse-grained sediment) to reconstruct TC properties (frequency and intensity of rainfall, wind) over the past few hundreds to thousands of years. However, different sensitivities and sampling biases in the various paleohurricane proxies restrict our ability to compile these records into regional or basin-scale TC estimates. Here we test how well pseudo tree-ring records of paleohurricanes capture TC rainfall and occurrence. Using a large set of statistically downscaled storms forced with the …

Removing Development Incentives In Risky Areas Promotes Climate Adaptation, Hannah Druckenmiller, Yanjun (Penny) Liao, Sophie Pesek, Margaret Walls, Shan Zhang

Economics Faculty Publications

As natural disasters grow in frequency and intensity with climate change, limiting the populations and properties in harm’s way will be key to adaptation. This study evaluates one approach to discouraging development in risky areas—eliminating public incentives for development, such as infrastructure investments, disaster assistance and federal flood insurance. Using machine learning and matching techniques, we examine the Coastal Barrier Resources System (CBRS), a set of lands where these federal incentives have been removed. We find that the policy leads to lower development densities inside designated areas, increases development in neighbouring areas, reduces flood damages and alters local demographics. Our …

State Of Coastal And Marine Resources: Lian, Batangas, Joseph Benedict T. Garcia, Mary Joyce P. Velos, Jemelyn Grace P. Baldisimo, Joey P. Cabasan, Ma Celina J. Añonuevo, Denmark B. Recamara, Hazel O. Arceo

Biological Sciences Faculty Publications

[Introduction] Lian (13.9852° N, 120.6545° E) is a third-class municipality in the northwestern part of the province of Batangas. It is bounded on the north by the municipality of Nasugbu, on the east by the municipalities of Tuy and Balayan, on the west by the WPS, and on the south by the municipality of Catatagan (Figure 2.7-1). It has a total land area of 76.80km² that is divided into 19 barangays, six of which are coastal and two are integrated coastal barangays (LGU-Lian 2013). Its total population is 56,280 individuals in 15,991 households as of 2020 (PSA 2020).

The main …

State Of Coastal And Marine Resources: Sablayan, Occidental Mindoro, Ma Celina J. Añonuevo, Jemelyn Grace P. Baldisimo, Denmark B. Racamara, Mary Joyce P. Velos, Joseph Benedict T. Garcia, Frederico B. Sabban, Joey P. Cabasan, Rhea Mae Luciano, Darryl Anthony Valiño, Lovely Joy Heyres, Hazel O. Arceo

Biological Sciences Faculty Publications

[Introduction] Sablayan, situated on the western side of Mindoro Island facing the WPS (12.8564° N, 120.9101° E), is a first-class municipality in the province of Occidental Mindoro with a total land area of 2,188.8km² that is divided into 22 barangays, nine of which are along the coast. The coastline stretches for 115 km, with municipal waters covering approximately 750,000 km² (LGU-Sablayan 2008).

The Apo Reef Natural Park, one of its most prominent features, is located approximately 33 km off the coast (Figure 2.9-1) The Apo Reef Natural Park is a protected coral reef system under presidential proclamation 868 (1996) encompassing …

Deconstructing The Mangrove Carbon Cycle: Gains, Transformation, And Losses, M. F. Adame, N. Cormier, P. Taillardat, N. Iram, A. Rovai, T. M. Sloey, E. S. Yando, J. F. Blanco-Libreros, M. Arnaud, T. Jennerjahn, C. E. Lovelock, D. Friess, G. M. S. Reithmaier, C. A. Buelow, S. M. Muhammad-Nor, R. R. Twilley, R. A. Ribeiro

Biological Sciences Faculty Publications

Mangroves are one of the most carbon-dense forests on the Earth and have been highlighted as key ecosystems for climate change mitigation and adaptation. Hundreds of studies have investigated how mangroves fix, transform, store, and export carbon. Here, we review and synthesize the previously known and emerging carbon pathways in mangroves, including gains (woody biomass accumulation, deadwood accumulation, soil carbon sequestration, root and litterfall production), transformations (food web transfer through herbivory, decomposition), and losses (respiration as CO₂ and CH₄, litterfall export, particulate and dissolved carbon export). We then review the technologies available to measure carbon fluxes in …

Antarctic Polar Stratospheric Cloud Analysis Of Ace-Fts Data From 2005 To 2023, M. Lecours, C. D. Boone, P. F. Bernath

Chemistry & Biochemistry Faculty Publications

We present an analysis of Antarctic polar winters from 2005 to 2023 as observed by the Atmospheric Chemistry Experiment (ACE). The unique broad band infrared spectral features in ACE “residual” spectra are used to classify the spectra of polar aerosols by composition into polar stratospheric clouds (PSCs) and sulfate aerosols. The spectra of PSCs are further classified into nitric acid trihydrate, supercooled ternary solutions, supercooled nitric acid, ice-mix, and mixtures of PSCs. A breakdown of PSC composition is presented for each year. Antarctic winter seasons with unusual compositions are: 2011, in which volcanic ash mixed with PSCs was observed from …

On The Links Between Sea Level And Temperature Variations In The Chesapeake Bay And The Atlantic Meridional Overturning Circulation (Amoc), Tal Ezer, Teresa Updyke

CCPO Publications

Recent studies found that on long time scales there are often unexplained opposite trends in sea level variability between the upper and lower Chesapeake Bay (CB). Therefore, daily sea level and temperature records were analyzed in two locations, Norfolk in the southern CB and Baltimore in the northern CB; surface currents from Coastal Ocean Dynamics Application Radar (CODAR) near the mouth of CB were also analyzed to examine connections between the CB and the Atlantic Ocean. The observations in the bay were compared with daily Atlantic Meridional Overturning Circulation (AMOC) observations during 2005–2021. Empirical Mode Decomposition (EMD) analysis was used …

Evidence For Large-Scale Climate Forcing Of Dense Shelf Water Variability In The Ross Sea, Zhaoru Zhang, Chuan Xie, Pasquale Castagno, Matthew H. England, Xiaoqiao Wang, Michael S. Dinniman, Alessandro Silvano, Chuning Wang, Lei Zhou, Xichen Li, Meng Zhou, Giorgio Budillon

CCPO Publications

Antarctic Bottom Water (AABW), which supplies the lower limb of the thermohaline circulation, originates from dense shelf water (DSW) forming in Antarctic polynyas. Here, combining a long mooring record of DSW measurements with numerical simulations and satellite data, we show that significant correlation exists between interannual variability of DSW production in the Ross Sea polynyas, where DSW contributes between 20-40% of the global AABW production, and the Southern Annular Mode (SAM). The correlation is largest when the Amundsen Sea Low (ASL) is weakened and shifted east of the Ross Sea. During positive SAM phases, enhanced offshore winds and lower air …

Western Boundary Current-Subtropical Continental Shelf Interactions, William B. Savidge, Dana K. Savidge, Frederico Brandini, Adam T. Greer, Eileen E. Hofmann, Moninya Roughan, Iison De Silvera, Iain M. Suthers

CCPO Publications

Western boundary currents (WBCs) adjacent to subtropical continental shelves (STCSs; between ~25° and 35° latitude; Figure 1) transport heat, nutrients, and biota poleward along the western margins of major ocean basins, interacting with the continental margins and influencing their physics and biology. Eddies and meanders along the shelf edge upwell deep, nutrient-laden water that can be advected onto the adjacent shelves with a corresponding export of particle-rich shelf water (e.g., Lee et al., 1991; Kimura et al., 1997; Campos et al., 2000; Roughan and Middleton, 2002, 2004; Lutjeharms, 2006; Savidge and Savidge, 2014). Despite their similarities, the various STCS regions …

Divergent Responses Of Nitrogen-Species Loadings To Future Climate Change In The Chesapeake Bay Watershed, Zihao Bian, Shufen Pan, Raymond G. Najjar, Marjorie A.M. Friedrichs, Eileen E. Hofmann, Maria Herrmann, Kyle E. Hinson, Pierre St.-Laurent, Hanqin Tian

CCPO Publications

Study region: Chesapeake Bay Watershed

Study focus: Climate plays a critical role in regulating N loading from terrestrial ecosystems to coastal waters and further affecting the health and functioning of coastal ecosystems. However, the sensitivities of riverine exports of different N species to climate change have rarely been investigated. This study examines the response of riverine exports of ammonia (NH₄⁺), nitrate (NO₃^-), dissolved organic nitrogen (DON), and particulate organic nitrogen (PON) to future changes in precipitation and temperature. A suite of climate forcings was used to drive a processbased terrestrial-aquatic model, DLEM (Dynamic Land Ecosystem Model), …

Season Influences Interspecific Responses Of Canopy-Forming Kelps To Future Warming And Acidification At High Latitude, Lauren E. Bell, Lily Westphal, Evan O' Brien, Jason A. Toy, Haleigh Damron, Kristy J. Kroeker

Biological Sciences Faculty Publications

Variability in primary producers' responses to environmental change may buffer higher trophic levels against shifts in basal resource composition. Then again, in instances where there is a lack of functional redundancy because consumers rely on a few species to meet their energetic requirements at specific times of the year, altered community production dynamics may significantly impact food web resilience. In high-latitude kelp forests, a complementary annual phenology of seaweed production supports coastal marine consumers' metabolic needs across large seasonal variations in their environment. Yet, marine consumers in these systems may face significant metabolic stress under the pronounced low pH conditions …