Impacts of the Deepwater Horizon Oil Spill on Salt Marsh Periwinkles (Littoraria irrorata).

Deepwater Horizon was the largest marine oil spill in U.S. waters, oiling large expanses of coastal wetland shorelines. We compared marsh periwinkle (Littoraria irrorata) density and shell length at salt marsh sites with heavy oiling to reference conditions ∼16 months after oiling. We also compared periwinkle density and size among oiled sites with and without shoreline cleanup treatments. Densities of periwinkles were reduced by 80-90% at the oiled marsh edge and by 50% in the oiled marsh interior (∼9 m inland) compared to reference, with greatest numerical losses of periwinkles in the marsh interior, where densities were naturally higher. Shoreline cleanup further reduced adult snail density as well as snail size. Based on the size of adult periwinkles observed coupled with age and growth information, population recovery is projected to take several years once oiling and habitat conditions in affected areas are suitable to support normal periwinkle life-history functions. Where heavily oiled marshes have experienced accelerated erosion as a result of the spill, these habitat impacts would represent additional losses of periwinkles. Losses of marsh periwinkles would likely affect other ecosystem processes and attributes, including organic matter and nutrient cycling, marsh-estuarine food chains, and multiple species that prey on periwinkles.

Determining recovery of marine water quality of the Rio Doce using statistical and temporal comparisons with nearby river systems.

The Fundão dam breach affected the Rio Doce's estuarine and marine environments with water, tailings, scoured soil and/or sediments, and other debris. Time series and standard exceedance analyses are typically used to assess water quality recovery to baseline conditions after deteriorating water quality events. In the absence of historical measurements, impacts to water quality from the Fundão Event were compared with measurements of nearby rivers. Similar river systems with available water quality measurements were grouped into affected and unaffected estuarine and marine waters. Statistical and temporal comparisons of marine waters unaffected by the Rio Doce with those affected by the Rio Doce were evaluated for systematic differences. Multivariate statistical techniques were also used to assess water quality differences. Our results demonstrate that the Fundão dam breach had a short-term water quality impact on marine waters near the Rio Doce mouth. Principal component and comparative time series analyses clearly demonstrated this impact during the 2015/2016 and 2016/2017 wet seasons. The ephemeral effects of the breach, however, did not compromise marine water quality. Exceedances of CONAMA standards for metals remained either at zero or at very low levels during the affected period (<5.7%). Before the start of the next wet season in October 2017, water quality impacts from the Event were statistically indistinguishable from unaffected marine waters, indicating recovery to baseline conditions. Integr Environ Assess Manag 2024;20:99-116. © 2023 NewFields Companies, LLC. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Applying multivariate techniques to fingerprint water quality impact of the Fundão Dam breach within the Rio Doce basin.

The Fundão Dam breach on 5 November 2015 (the "Event") released tailings, water, soil and/or sediments, and other debris to downstream watercourses. This breach included both direct and indirect impacts from scouring of soils and sediments along and within the affected courses. Multivariate statistical techniques were used to determine the potential of fingerprinting the impact of the breach compared to pre-Event water quality conditions and unaffected watercourses. The selection of key parameters is an important first step for multivariate analyses. Analysis of too many parameters can mask important trends and relationships, while analysis of too few may miss significant water quality indicators. A two-phased selection process was used to identify key parameters that indicated impact from the Event: (a) unbiased, principal component analysis to extract chemically dominant profiles among all measured parameters and (b) comparison of metals' concentrations between unaffected soils and/or sediments and tailings samples. Radar charts of key parameters along with statistical comparisons to pre-Event and not-affected waterways were then aggregated over space and time to assess impact and potential recovery to pre-Event conditions. Nine parameters were identified that characterize tailings-related (direct) and background soil and/or sediment-related (indirect) impacts. Spatially and temporally aggregated radar charts and nonparametric Mann-Whitney U tests were used to assess the statistical significance of these impacts during each wet season since the breach. Indirect parameters, like aluminum and lead, returned to pre-Event levels in the first wet season after the Event. By the 2018/2019 wet season, most of the direct and indirect parameters had returned to pre-Event levels. Integr Environ Assess Manag 2024;20:133-147. © 2023 NewFields Companies, LLC. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Using spatiotemporal ratio analyses to quantitatively estimate water quality recovery of the Rio Doce.

The Fundão Dam breached on 5 November 2015 (the "Event"), resulting in the release of tailings, water, scoured sediment and/or soil, and other debris to downstream watercourses. Statistical analyses using historical and recent water quality measurements were conducted to assess the extent to which water quality in the Rio Doce was recovering to baseline conditions. A review of station- and/or parameter-specific water quality time series in the Rio Doce revealed two challenges: pre-Event data imbalance and seasonality. Due to the combined effects of these two factors, data gathered from Rio Doce water quality stations before the Event likely underestimated concentration ranges and limited the usefulness of common recovery assessment techniques such as times series and water quality standard exceedance analyses. These challenges were addressed by calculating quarterly and watershed-specific river-to-tributary ratios. R code was used to produce spatiotemporal time series for 44 investigated parameters that were measured both before and after the Event. The water quality recovery durations shown by the parameter- and/or region-specific river-to-tributary ratio time series indicated that (a) turbidity provides the most conservative measure for water quality recovery; (b) chemical parameters associated with the tailings, like manganese and iron recovered faster than turbidity; and (c) other investigated parameters unrelated to the tailings showed either no discernable impact or rapid recovery after the Event. The resulting parameter- and/or region-specific river-to-tributary ratio time series provided reliable and quantifiable estimates of water quality recovery durations. The water quality in the region furthest from Fundão Dam, in Espírito Santo, recovered one year after the Event, while water quality in the closest region to Fundão Dam, upstream of Risoleta Neves (Candonga) Dam, recovered 4.2 years after the Event. Integr Environ Assess Manag 2024;20:74-86. © 2023 Newfields Companies, LLC. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Assessing the footprint and volume of oil deposited in deep-sea sediments following the Deepwater Horizon oil spill.

The lateral and vertical extents of Macondo oil in deep-sea sediments resulting from the 2010 Deepwater Horizon oil spill were determined using chemical forensics and geostatistical kriging of data from 2397 sediment samples from 875 cores collected in 2010/2011 and 2014. The total mass of Macondo-derived hopane on the seafloor in 2010/2011 was conservatively estimated between 2.00 and 2.26metric tons, derived from 219,000 to 247,000barrels of oil; or 6.9 to 7.7% of the 3.19millionbarrels spilled. Macondo-derived hopane was deposited over 1030 to 1910km2 of the seafloor, mostly (>97%) in surface (0-1cm) and near-surface (1-3cm) sediments, which is consistent with short-term oil deposition. Although Macondo oil was still present in surface sediments in 2014, the total mass of Macondo-derived hopane was significantly lower (~80 to 90%) than in 2010/2011, affirming an acute impact from the spill and not long-term deposition from natural seeps.