Joseph M. Smoak | University of South Florida (original) (raw)

Papers by Joseph M. Smoak

Rates of organic carbon (OC) burial in some coastal wetlands appear to be greater in recent years... more Rates of organic carbon (OC) burial in some coastal wetlands appear to be greater in recent years than they were in the past. Possible explanations include ongoing mineralization of older OC or the influence of an unaccounted-for artifact of the methods used to measure burial rates. Alternatively, the trend may represent real acceleration in OC burial. We quantified OC burial rates of mangrove and brackish marsh sites in southwest Florida through a comparison of rates derived from 210Pb, 137Cs, and surface marker horizons (MH). Age/depth profiles of lignin:OC were used to assess whether down-core remineralization had depleted the OC pool relative to lignin, and lignin phenols were used to quantify the variability of lignin degradation. OC burial rates increased in all seven cores by factors ranging from 1.4 to 6.2 over the past 120 years. We propose that these increases represent net acceleration. Change in relative sea-level rise is the most likely large-scale driver of acceleratio...

Pedobiologia, 2021

Abstract Shrub encroachment into grasslands can greatly alter soil organic carbon (SOC), nitrogen... more Abstract Shrub encroachment into grasslands can greatly alter soil organic carbon (SOC), nitrogen (N) cycling processes, and carbon (C) pools. However, the effects of shrub encroachment on the soil microbial community and its feedback on the chemical composition of SOC are not well understood in the alpine ecosystems. This study aims to evaluate the impact of the encroachment of the shrubs Salix cupularis and Hippophae rhamnoides on SOC, soil microbial biomass C (MBC) and N (MBN), microbial community structure, and enzyme activities of the topsoil (0–30 cm) and explore the underlying mechanisms in the eastern Tibetan Plateau grasslands of China. We found that while SOC increased under both S. cupularis (16.0% increase) and H. rhamnoides (23.3% increase), only the increase in H. rhamnoides was significant in comparison with the adjacent grass soils. The recalcitrant C pool increases were not significant in S. cupularis or H.rhamnoides soils. Additionally, shrub encroachment significantly increased the soil organic N and the activities of N-acetyl-β-glucosaminidase (NAG) and leucine aminopeptidase (LAP). Shrub encroachment significantly increased MBC and MBN, as well as enhanced the total bacteria PLFAs, gram-negtive bacteria PLFAs, arbuscular mycorrhizal fungi, actinomycetes, and hydrolytic enzyme activities, but suppressed the ratio of total fungi to total bacteria PLFAs and phenol oxidase activity in comparison with grassland communities. Redundancy analysis (RDA) showed that litterfall mass, litter N, and root N were the main factors affecting the soil microbial community. Our findings highlight that the encroachment of shrub H. rhamnoides tends to increase soil C sequestration as a result of the high quantities of plant litter input and the changes in the composition of soil microbial communities as well as increased complex C compounds in soil organic matter.

This dataset provides modeled estimates of soil carbon stocks for tidal wetland areas of the Cont... more This dataset provides modeled estimates of soil carbon stocks for tidal wetland areas of the Conterminous United States (CONUS) for the period 2006-2010. Wetland areas were determined using both 2006-2010 Coastal Change Analysis Program (C-CAP) raster maps and the National Wetlands Inventory (NWI) vector data. All 30 x 30-meter C-CAP pixels were extracted that are coded as estuarine emergent, scrub/shrub, or forested in either 2006 or 2010. A soil database for model fitting and validation was compiled from 49 different studies with spatially explicit empirical depth profile data and associated metadata, totaling 1,959 soil cores from 18 of the 22 coastal states. Reported estimates of carbon stocks were derived with modeling approaches that included (1) applying a single average carbon stock value from the compiled soil core data, (2) applying models fit using the empirical data and applied spatially using soil, vegetation and salinity maps, (3) relying on independently generated soil carbon maps from The United States Department of Agriculture (USDA)'s Soil Survey Geographic Database (SSURGO), and the NWI that intersected with mapped tidal wetlands, and (4) using a version of SSURGO bias-corrected for bulk density. Comparisons of uncertainty, precision, and accuracy among these four approaches are also provided.

Journal of Soils and Sediments, 2020

Purpose In order to assess the impact of anthropogenic activities on carbon and nutrient accumula... more Purpose In order to assess the impact of anthropogenic activities on carbon and nutrient accumulation, total organic carbon (TOC), nitrogen (TN), and phosphorus (TP) accumulation rates were examined in a 210 Pb-dated mangrove sediment core from Sepetiba Bay, Brazil, a coastal region impacted by multiple environmental changes during the previous century. Materials and methods A 50-cm length sediment core was collected from a mangrove forest in Sepetiba Bay. Sediment subsamples were analyzed to measure TOC, TN, δ 13 C, and δ 15 N using an elemental analyzer attached to an isotope ratio mass spectrometer Thermo Finnigan Model Delta Plus XP, whereas colorimetric analysis were used to measure TP. For 210 Pbex analyses, gamma-ray measurements were performed in a semiplanar intrinsic germanium high purity coaxial detector, coupled to a multichannel analyzer, whereas the sediment accumulation rate (SAR) was calculated according to the constant initial concentration (CIC) method. Also, carbon and nutrient fluxes were calculated using SAR and TOC, TN, and TP contents, whereas statistical differences were evaluated by ANOVA + Tukey HSD analysis with previous data normalization. Results and discussion The calculated sedimentation rate (~8.1 mm year −1) since the early 1900s was up to threefold higher than the global mean determined for mangrove forests (~2.8 mm year −1) and the regional sea level rise (~3.2 mm year −1). Significantly higher TOC, TN, and TP fluxes, up to nearly 1000, 90, and 15 g m −2 year −1 , respectively, were observed after the water diversion from a nearby drainage basin in the 1950s and an increase in sewage effluent input, which increased in the Responsible editor: Nives Ogrinc

Nature Communications, 2019

Calcium carbonates (CaCO3) often accumulate in mangrove and seagrass sediments. As CaCO3 producti... more Calcium carbonates (CaCO3) often accumulate in mangrove and seagrass sediments. As CaCO3 production emits CO2, there is concern that this may partially offset the role of Blue Carbon ecosystems as CO2 sinks through the burial of organic carbon (Corg). A global collection of data on inorganic carbon burial rates (Cinorg, 12% of CaCO3 mass) revealed global rates of 0.8 TgCinorg yr−1 and 15–62 TgCinorg yr−1 in mangrove and seagrass ecosystems, respectively. In seagrass, CaCO3 burial may correspond to an offset of 30% of the net CO2 sequestration. However, a mass balance assessment highlights that the Cinorg burial is mainly supported by inputs from adjacent ecosystems rather than by local calcification, and that Blue Carbon ecosystems are sites of net CaCO3 dissolution. Hence, CaCO3 burial in Blue Carbon ecosystems contribute to seabed elevation and therefore buffers sea-level rise, without undermining their role as CO2 sinks.

Communications Earth & Environment, 2022

Stormwater ponds are engineered ecosystems designed for flood control and sediment retention in u... more Stormwater ponds are engineered ecosystems designed for flood control and sediment retention in urban watersheds. They are the most commonly used stormwater control measure in the USA, but their biogeochemical processes and impacts are often overlooked. Here, we assessed the potential impact of stormwater ponds on regional carbon cycling by coupling carbon burial rates and fluxes of carbon dioxide and methane gases in five sites over an age gradient of 14–34 years. Carbon burial increased logarithmically with site age, ranging from 22 to 217 g carbon m−2 y−1, while, median floating chamber diffusive gas fluxes were 1290 g carbon dioxide m−2 y−1 and 5 g methane m−2 y−1, which, when combined as carbon dioxide equivalents, equates to 2900 g carbon dioxide eq m−2 y−1. Comparing carbon burial to gas flux reveals that stormwater ponds can be net carbon sources and need to be considered for regional and global carbon models.

During glacial/interglacial cycles, changes in the strength of the Atlantic Meridional Overturnin... more During glacial/interglacial cycles, changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC) modified the intermediate and deep-water mass proportions and high latitude productivity in the Atlantic Ocean. These factors influence the distribution and geochemical partitioning of trace metals in the ocean. Mercury is a redox and productivity-sensitive trace metal, making it a potential proxy of paleoenvironmental changes. Therefore, this work examines the effect of Atlantic Ocean circulation changes during the last two glacial/interglacial cycles on the biogeochemistry of Hg. For this, a high-resolution record of the total Hg concentration was determined in core GL-1090 collected from the Southwestern Subtropical Atlantic that represents the last 185 thousand years. During the reported glacial/interglacial cycles, Hg showed a distinct trend throughout Marine Isotope Stages with higher concentrations during periods of enhanced penetration of northern component w...

Frontiers in Marine Science

We reconstruct paleoredox conditions in the Western Equatorial Atlantic (WEA) over the glacial-in... more We reconstruct paleoredox conditions in the Western Equatorial Atlantic (WEA) over the glacial-interglacial cycle (~130 ka) by using new high-resolution REEs data and their anomalies from a marine sediment core (GL-1248) collected from the equatorial margin off the continental shelf of NE Brazil. This approach aims to improve the understanding of the dynamics of paleoclimatic and sedimentary inputs on the coast of northeastern Brazil. Marine sediments were analyzed via Mass Spectrometry (ICP-MS) after total digestion with HF/HNO3. REEs proxies are a useful tool in understanding the transport and origin of sediments due to their physicochemical properties. Our data showed the Parnaíba River was the main source of REEs content in the western South Atlantic. Fe minerals (Fe-oxyhydroxides) produced via weathering of continental and tropical soils were the principal REE-carrier phase during transportation and ultimate deposition at core site GL-1248. Several regional climatic factors mai...

Atmosphere

Severe thunderstorms are often accompanied by strong vertical air currents, temporary wind gusts,... more Severe thunderstorms are often accompanied by strong vertical air currents, temporary wind gusts, and heavy rainfall. The development of this atmospheric phenomenon over tropical shallow water zones, such as bays, can lead to intensification of atmospheric disturbances and produce a small-scale storm surge. Here, the storm surge that occurred on 19 March 2017 in the Persian Gulf coastal area has been investigated. Air temperature, precipitation, mean sea level pressure, wave height, wind direction, wind speed, geopotential height, zonal components, meridional winds, vertical velocity, relative humidity, and specific humidity obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF) and Global Forecast System (FNL) were used to implement the Weather Research and Forecasting (WRF) model. The results showed that the main cause of the storm surge was the occurrence of a supercell thunderstorm over the Persian Gulf. The formation of this destructive phenomenon resulted...

The objective of this research was to measure temporal variability in accretion and mass sediment... more The objective of this research was to measure temporal variability in accretion and mass sedimentation rates (including organic carbon (OC), total nitrogen (TN), and total phosphorous (TP)) from the past century in a mangrove forest on the Shark River in Everglades National Park, USA. The 210Pb Constant Rate of Supply model was applied to six soil cores to calculate annual rates over the most recent 10, 50, and 100 year time spans. Our results show that rates integrated over longer timeframes are lower than those for shorter, recent periods of observation. Additionally, the substantial spatial variability between cores over the 10 year period is diminished over the 100 year record, raising two important implications. First, a multiple-decade assessment of soil accretion and OC burial provides a more conservative estimate and is likely to be most relevant for forecasting these rates relative to long-term processes of sea level rise and climate change mitigation. Second, a small numbe...

Journal of Soil Science and Plant Nutrition, 2021

Ecosystems, 2018

Mangrove wetlands are some of the most important locations of organic carbon (OC) sequestration a... more Mangrove wetlands are some of the most important locations of organic carbon (OC) sequestration and storage in the world on a per area basis. The high stocks of soil OC are driven by generally high burial rates and efficient preservation of organic material over past millennia of relatively slow and consistent sea level rise. Although the global average rate of OC burial in mangrove wetlands is relatively high, the range in the literature varies by up to two orders of magnitude. The objective of this research was to measure burial rates of OC, CaCO 3 , and nutrients [total nitrogen (TN) and phosphorous (TP)] across a pronounced ecosystem gradient of productivity and salinity in the coastal Everglades of southwestern Florida, USA. Concentrations and burial rates of both CaCO 3 (range 13-1233 g m-2 y-1) and TP (range 0.10-1.59 g m-2 y-1) decreased significantly with distance from the Gulf of Mexico. In contrast, there was less spatial variability in OC (134 ± 12 (1 SE) g m-2 y-1) and TN (6.2 ± 0.4 g m-2 y-1) burial rates. However, significant (P < 0.001) regional differences in OC burial rates were observed relative to mangrove primary productivity. Over a centennial timescale, downstream sites buried 14% of annual net primary production, midstream sites buried 22%, and upstream sites preserved less than 10%.

Journal of Geophysical Research: Biogeosciences, 2017

Ecosystem respiration rates in relict permafrost areas are high. Temperature sensitivity of ecosy... more Ecosystem respiration rates in relict permafrost areas are high. Temperature sensitivity of ecosystem respiration in the non-permafrost areas is greater than those of permafrost areas. Experimental warming increased annual ecosystem respiration by approximately 50%, half of the increase occurred during the non-growing seasons.

Ecological Indicators, 2018

Torrecillas Lagoon, on the north coast of Puerto Rico, has experienced extensive anthropogenic in... more Torrecillas Lagoon, on the north coast of Puerto Rico, has experienced extensive anthropogenic influence over the past 200 years. Elevated concentrations of Potentially Toxic Elements (PTEs) in bulk sediment (Cu, Zn, Pb, Ni, Cr, Li, V, Fe, As, Se, and Mn) have been reported in surficial sediments and have relatively uniform spatial distributions. Areas with higher concentrations are associated with a higher percentage of total organic carbon (TOC) and percent mud (mud), as well as anoxic conditions. Ammonia beccarii, Quinqueloculina rhodiensis, and Triloculina oblonga are the dominant foraminifers in the lagoon and are characteristic of stressed coastal environments. Bulk concentrations of Cu-Zn-Fe are negatively correlated with numerous foraminiferal taxa, absolute abundances, and diversity indices, though very few correlations with the bioavailable counterparts (F2 Tess-bioavailable) are observed. Similarly, relative abundances of Quinqueloculina and Triloculina positively correlate with bulk Cu-Zn-Fe but not with F2 Tess-bioavailable. The waters in Torrecillas lagoon show strong stratification, with hypoxic/anoxic (dissolved oxygen <3 mg/L) and corrosive (pH < 7.4) conditions below 4 m depth. The presence of such strong gradients in very shallow water represents a dynamic chemical environment, with changes occurring on day-night cycles, tidal cycles, and especially with storm activity that induces mixing of otherwise highly stratified, very localized waters. Recognizing the potential for sequestered PTEs to be remobilized is an essential insight for coastal management agencies that must assess the risks of existing PTEs during coastal engineering activities (e.g., dredge and fill activities) and major storm events. Exchangeable and oxidizable fractions are likely more bioavailable than acid-soluble fractions in influencing the ecology of foraminifers under most circumstances.

SIL Proceedings, 1922-2010, 2006

face runoff. Augmented lakes receive a portion of their input waters as groundwater from the Flor... more face runoff. Augmented lakes receive a portion of their input waters as groundwater from the Floridan Aquifer, which consists of Eocene to Miocene limestones (Scorr 1997). Our study of augmented Lake Charles was designed to: (l) identify the sediment fraction that binds dissolved 226 Ra in groundwater after it enters the lake and (2) to evaluate the stratigraphic distribution of 226 Ra and other constituents in the sediment profile.

Journal of Arid Environments, 2018

Mangrove forests rank as one of the world's most productive biomes and their soils are highly eff... more Mangrove forests rank as one of the world's most productive biomes and their soils are highly efficient in accumulating organic carbon (OC). Most research on OC in mangrove forests has focused on moist tropical and subtropical regions. Here we examine an arid mangrove forest (composed of the species Avicennia marina) from the Jask area in southern Iran. The organic carbon content, TOC:TN ratios and δ 13 C signatures indicate that marine algae and microalgae are a greater source of organic material than the terrestrial inputs at three out of the four study sites in this work. Furthermore, sea-level rise as well as geomorphic and topographic differences are contributing to the mangrove landward migration and expansion of 112 ha (or 33%) of these arid forests between 1956 and 2012. This is substantial as up to 0.60 g OC cm −2 were found in the upper 42 cm of the soils. However, these values should be taken with caution as the large inorganic carbon deposition in the soils here and in other regions may offset the CO 2 sequestration of the global arid mangroves in terms of climate mitigation.