Modeling the Biogeochemical Cycle of Selenium in the San Francisco Bay

Due to recent concerns about selenium toxicity in the San Francisco Bay and the roles of refinery and San Joaquin River inputs on the selenium cycle, the model ECoS 3 (distributed from Plymouth Marine Laboratory, United Kingdom) was modified to simulate the biogeochemical cycle of selenium in the Northern Reach. The model is designed to simulate salinity, total suspended material, phytoplankton concentrations, dissolved selenium and its speciation (selenite, selenate, and organic selenide), and particulate selenium and its speciation (selenite + selenate, elemental selenium, and organic selenide). Actual data from 1999 were used to calibrate the model, while data from other sampling periods (1986–1988 and 1997–1998) were then compared to model simulations to verify its accuracy. The sensitivity of the model to specific inputs of selenium was also determined. These results indicate that dissolved selenium is largely controlled by riverine and refinery inputs, while particulate selenium is a function of phytoplankton productivity and riverine inputs of sediment. Forecasting simulations included increasing the San Joaquin River discharge to the Delta and varying refinery discharges to the Bay. These simulation results indicate that total particulate selenium concentrations may increase in the entire Bay to 1 μg g−1 if the San Joaquin Flow is increased. This concentration is twice as high as the current estuarine average particulate selenium and at the level where the concentration of selenium in Potomocorbula amurensis becomes problematic for estuarine predators. Furthermore, simulations suggest that doubling the current refinery loads as selenate have little effect on the particle-associated selenium in the estuary. Simulated data from the model can be used in other models to predict selenium concentrations in higher trophic levels. Furthermore the model can be used as a template to study the biogeochemical cycle of other elements in well-mixed estuaries, and in restoration projects, pollution control and other trophic transfer scenarios

Evaluating the Biogeochemical Cycle of Selenium in San Francisco Bay Through Modeling

A biogeochemical model was developed to simulate salinity, total suspended material, phytoplankton biomass, dissolved selenium concentrations (selenite, selenate, and organic selenide), and particulate selenium concentrations (selenite + selenate, elemental selenium, and organic selenide) in the San Francisco Bay estuary. Model-generated estuarine profiles of total dissolved selenium reproduced observed estuarine profiles at a confidence interval of 91- 99% for 8 different years under various environmental conditions. The model accurately reproduced the observed dissolved speciation at confidence intervals of 81-98% for selenite, 72-91% for selenate, and 60-96% for organic selenide. For particulate selenium, model-simulated estuarine profiles duplicated the observed behavior of total particulate selenium (76-93%), elemental selenium (80-97%), selenite + selenate (77-82%), and organic selenide (70-83%). Discrepancies between model simulations and the observed data provided insights into the estuarine biogeochemical cycle of selenium that were largely unknown (e.g., adsorption/desorption). Forecasting simulations investigated how an increase in the discharge from the San Joaquin River and varying refinery inputs affect total dissolved and particulate selenium within the estuary. These model runs indicate that during high river flows the refinery signal is undetectable, but when river flow is low (70- day residence time) total particle-associated selenium concentrations can increase to \u3e2 µg g-1 . Increasing the San Joaquin River discharge could also increase the total particle-associated selenium concentrations to \u3e1 µg g-1 . For both forecasting simulations, particle-associated selenium was predicted to be higher than current conditions and reached levels where selenium could accumulate in the estuarine food web

Effects of CO\u3csub\u3e2\u3c/sub\u3e on Growth Rate, C:N:P, and Fatty Acid Composition of Seven Marine Phytoplankton Species

Carbon dioxide (CO2) is the primary substrate for photosynthesis by the phytoplankton that form the base of the marine food web and mediate biogeochemical cycling of C and nutrient elements. Specific growth rate and elemental composition (C:N:P) were characterized for 7 cosmopolitan coastal and oceanic phytoplankton species (5 diatoms and 2 chlorophytes) using low density, nutrient-replete, semi-continuous culture experiments in which CO2 was manipulated to 4 levels ranging from post-bloom/glacial maxima (ppm) to geological maxima levels (\u3e2900 ppm). Specific growth rates at high CO2 were from 19 to 60% higher than in low CO2 treatments in 4 species and 44% lower in 1 species; there was no significant change in 2 species. Higher CO2 availability also resulted in elevated C:P and N:P molar ratios in Thalassiosira pseudonana (~60 to 90% higher), lower C:P and N:P molar ratios in 3 species (~20 to 50% lower), and no change in 3 species. Carbonate system-driven changes in growth rate did not necessarily result in changes in elemental composition, or vice versa. In a subset of 4 species for which fatty acid composition was examined, elevated CO2 did not affect the contribution of polyunsaturated fatty acids to total fatty acids significantly. These species show relatively little sensitivity between present day CO2 and predicted ocean acidification scenarios (year 2100). The results, however, demonstrate that CO2 availability at environmentally and geologically relevant scales can result in large changes in phytoplankton physiology, with potentially large feedbacks to ocean biogeochemical cycles and ecosystem structure

Recommended Priorities for Research on Ecological Impacts of Ocean and Coastal Acidification in the U.S. Mid-Atlantic

The estuaries and continental shelf system of the United States Mid-Atlantic are subject to ocean acidification driven by atmospheric CO2, and coastal acidification caused by nearshore and land-sea interactions that include biological, chemical, and physical processes. These processes include freshwater and nutrient input from rivers and groundwater; tidally-driven outwelling of nutrients, inorganic carbon, alkalinity; high productivity and respiration; and hypoxia. Hence, these complex dynamic systems exhibit substantial daily, seasonal, and interannual variability that is not well captured by current acidification research on Mid-Atlantic organisms and ecosystems. We present recommendations for research priorities that target better understanding of the ecological impacts of acidification in the U. S. Mid-Atlantic region. Suggested priorities are: 1) Determining the impact of multiple stressors on our resource species as well as the magnitude of acidification; 2) Filling information gaps on major taxa and regionally important species in different life stages to improve understanding of their response to variable temporal scales and sources of acidification; 3) Improving experimental approaches to incorporate realistic environmental variability and gradients, include interactions with other environmental stressors, increase transferability to other systems or organisms, and evaluate community and ecosystem response; 4) Determining the capacity of important species to acclimate or adapt to changing ocean conditions; 5) Considering multi-disciplinary, ecosystem-level research that examines acidification impacts on biodiversity and biotic interactions; and 6) Connecting potential acidification-induced ecological impacts to ecosystem services and the economy. These recommendations, while developed for the Mid-Atlantic, can be applicable to other regions will help align research towards knowledge of potential larger-scale ecological and economic impacts

Projecting ocean acidification impacts for the Gulf of Maine to 2050: new tools and expectations

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Siedlecki, S. A., Salisbury, J., Gledhill, D. K., Bastidas, C., Meseck, S., McGarry, K., Hunt, C. W., Alexander, M., Lavoie, D., Wang, Z. A., Scott, J., Brady, D. C., Mlsna, I., Azetsu-Scott, K., Liberti, C. M., Melrose, D. C., White, M. M., Pershing, A., Vandemark, D., Townsend, D. W., Chen, C,. Mook, W., Morrison, R. Projecting ocean acidification impacts for the Gulf of Maine to 2050: new tools and expectations. Elementa: Science of the Anthropocene, 9(1), (2021): 00062, https://doi.org/10.1525/elementa.2020.00062.Ocean acidification (OA) is increasing predictably in the global ocean as rising levels of atmospheric carbon dioxide lead to higher oceanic concentrations of inorganic carbon. The Gulf of Maine (GOM) is a seasonally varying region of confluence for many processes that further affect the carbonate system including freshwater influences and high productivity, particularly near the coast where local processes impart a strong influence. Two main regions within the GOM currently experience carbonate conditions that are suboptimal for many organisms—the nearshore and subsurface deep shelf. OA trends over the past 15 years have been masked in the GOM by recent warming and changes to the regional circulation that locally supply more Gulf Stream waters. The region is home to many commercially important shellfish that are vulnerable to OA conditions, as well as to the human populations whose dependence on shellfish species in the fishery has continued to increase over the past decade. Through a review of the sensitivity of the regional marine ecosystem inhabitants, we identified a critical threshold of 1.5 for the aragonite saturation state (Ωa). A combination of regional high-resolution simulations that include coastal processes were used to project OA conditions for the GOM into 2050. By 2050, the Ωa declines everywhere in the GOM with most pronounced impacts near the coast, in subsurface waters, and associated with freshening. Under the RCP 8.5 projected climate scenario, the entire GOM will experience conditions below the critical Ωa threshold of 1.5 for most of the year by 2050. Despite these declines, the projected warming in the GOM imparts a partial compensatory effect to Ωa by elevating saturation states considerably above what would result from acidification alone and preserving some important fisheries locations, including much of Georges Bank, above the critical threshold.This research was financially supported by the Major Special Projects of the Ministry of Science and Technology of China (2016YFC020600), the Young Scholars Science Foundation of Lanzhou Jiaotong University (2018033), and the Talent Innovation and Entrepreneurship Projects of Lanzhou (2018-RC-84)

Effect of ocean acidification on growth and otolith condition of juvenile scup, Stenotomus chrysops

Increasing amounts of atmospheric carbon dioxide (CO2) from human industrial activities are causing changes in global ocean carbonate chemistry, resulting in a reduction in pH, a process termed “ocean acidification.” It is important to determine which species are sensitive to elevated levels of CO2 because of potential impacts to ecosystems, marine resources, biodiversity, food webs, populations, and effects on economies. Previous studies with marine fish have documented that exposure to elevated levels of CO2 caused increased growth and larger otoliths in some species. This study was conducted to determine whether the elevated partial pressure of CO2 (pCO2) would have an effect on growth, otolith (ear bone) condition, survival, or the skeleton of juvenile scup, Stenotomus chrysops, a species that supports both important commercial and recreational fisheries. Elevated levels of pCO2 (1200–2600 latm) had no statistically significant effect on growth, survival, or otolith condition after 8 weeks of rearing. Field data show that in Long Island Sound, where scup spawn, in situ levels of pCO2 are already at levels ranging from 689 to 1828 latm due to primary productivity, microbial activity, and anthropogenic inputs. These results demonstrate that ocean acidification is not likely to cause adverse effects on the growth and survivability of every species of marine fish. X-ray analysis of the fish revealed a slightly higher incidence of hyperossification in the vertebrae of a few scup from the highest treatments compared to fish from the control treatments. Our results show that juvenile scup are tolerant to increases in seawater pCO2, possibly due to conditions this species encounters in their naturally variable environment and their well-developed pH control mechanisms.publishedVersio

The East River tidal strait, New York City, New York, a high-nutrient, low-chlorophyll coastal system

Abstract The East River tidal strait, located between New York Harbor and Western Long Island Sound, is characterized by high suspended silt concentrations with low organic content kept in suspension by intense tidal currents. Inorganic nutrients, including nitrate, nitrite, ammonia, and phosphate, were high even during the summer. Dissolved inorganic nitrogen (DIN) concentrations generally were above 20 µM and did not likely limit phytoplankton growth. Despite high nutrient concentrations, median chlorophyll a concentration was only 1.53 µg l−1, making the East River tidal strait a high-nutrient, low-chlorophyll (HNLC) area, likely a result of suspended silt blocking light penetration into the surface water. There were times at which the ratio of mixed layer to depth of the euphotic zone was generally greater than what has been suggested for phytoplankton to produce net primary production. The high-nutrient East River tidal strait is likely one of the sources of nutrients fueling summer phytoplankton production and consequent hypoxia in the Western Long Island Sound as silt settles from surface water in the lower turbulence conditions of the western narrows of Long Island Sound, thereby allowing light penetration and subsequent consumption of dissolved nutrients by phytoplankton

Seawater carbonate chemistry and Black Sea Bass hatching success and percentage of larvae with vertebral column anomalies

After a decade of research on how embryonic fish will respond to the increased dissolved carbon dioxide (ρCO2) levels predicted for the next century, no uniform response to near future acidification has been observed among marine species. We exposed Black Sea Bass Centropristis striata (BSB) embryos to varied levels of ρCO2 (microatmospheres [μatm]) for 48 h during seasonal experiments conducted in 2013–2015 to compare embryonic response among multiple broodstocks. The relationship between ρCO2 concentration and hatching success was inconsistent among years, with a nonlinear, inverse relationship noted in 2014 only, explaining 13% of observed variance. Conversely, ρCO2 was a good predictor of unhatched BSB embryos after 48 h for all years combined (39%) and for 2013 (38%). The ρCO2 concentration was a good predictor of the frequency of vertebral column anomalies for individual years (2013: 40%; 2014: 12%; 2015: 38%) but not when data were pooled for all years. In 2013 and 2015, vertebral column anomalies were relatively consistent below 1,000 μatm and were elevated above that threshold. Preliminary results suggest that BSB embryos may demonstrate resilience to future ρCO2 levels, but the results also highlight the challenges associated with drawing broad conclusions given observed variability in results obtained from different broodstocks and study years

Seawater carbonate chemistry and shell height and lipid concentrations of laboratory-reared larval Atlantic surfclam (Spisula solidissima)

The Atlantic surfclam (Spisula solidissima) supports a $29.2-million fishery on the northeastern coast of the United States. Increasing global carbon dioxide (CO2) in the atmosphere has resulted in a decrease in ocean pH, known as ocean acidification (OA), in Atlantic surfclam habitat. The effects of OA on larval Atlantic surfclam were investigated for 28 d by using 3 different levels of partial pressure of CO2 (ρCO2): low (344 μatm), medium (821 μatm), and high (1243 μatm). Samples were taken to examine growth, shell height, time to metamorphosis, survival, and lipid concentration. Larvae exposed to a medium ρCO2 level had a hormetic response with significantly greater shell height and growth rates and a higher percentage that metamorphosed by day 28 than larvae exposed to the high- and low-level treatments. No significant difference in survival was observed between treatments. Although no significant difference was found in lipid concentration, Atlantic surfclam did have a similar hormetic response for concentrations of phospholipids, sterols, and triacylglycerols and for the ratio of sterols to phospholipids, indicating that larvae may have a homeoviscous adaptation to OA at medium ρCO2 levels. Our results indicate that larval Atlantic surfclam have some tolerance to slightly elevated ρCO2 concentrations but that, at high ρCO2 levels, they may be susceptible to OA