Trophic interactions are important determinants of the structure and functioning of ecosystems. Because the metabolism and consumption rates of ectotherms increase sharply with temperature, there are major concerns that global warming will increase the strength of trophic interactions, destabilizing food webs, and altering ecosystem structure and function. We used geothermally warmed streams that span an 11°C temperature gradient to investigate the interplay between temperature-driven selection on traits related to metabolism and resource acquisition, and the interaction strength between the keystone gastropod grazer, Radix balthica, and a common algal resource. Populations from a warm stream (~28°C) had higher maximal metabolic rates and optimal temperatures than their counterparts from a cold stream (~17°C). We found that metabolic rates of the population originating from the warmer stream were higher across all measurement temperatures. A reciprocal transplant experiment demonstrated that the interaction strengths between the grazer and its algal resource were highest for both populations when transplanted into the warm stream. In line with the thermal dependence of respiration, interaction strengths involving grazers from the warm stream were always higher than those with grazers from the cold stream. These results imply that increases in metabolism and resource consumption mediated by the direct, thermodynamic effects of higher temperatures on physiological rates are not mitigated by metabolic compensation in the long term, and suggest that warming could increase the strength of algal-grazer interactions with likely knock-on effects for the biodiversity and productivity of aquatic ecosystems.

The Chandeleur Islands, Louisiana (USA), were among the first coastal locations in the northern Gulf of Mexico (GoM) threatened by exposure to Deepwater Horizon oil. Shoreline oiling data and surface oil trajectories (aerial and satellite imagery) showed oil passing through seagrass beds on the shallow back barrier shelf west of the islands repeatedly between May and early July 2010. Aerial photos in May 2010 revealed a heterogeneous distribution of surface oil crossing the shelf, and MC252 exposure was confirmed in sediments and seagrass tissue during field assessments. We observed 5 seagrasses growing at densities comparable to other northern GoM communities. Ruppia maritima and Halodule wrightii were the most common, followed by Thalassia testudinum. Syringodium filiforme and Halophila engelmannii were rarely encountered. The subtidal and intertidal seascape on the shelf was a mosaic of seagrass patches distributed in varying sizes among unvegetated and sparsely vegetated areas at water depths and in sediment types known to support seagrasses. To quantitatively assess the seagrass response following exposure, sophisticated change detection methodologies were applied to aerial photography acquired in October 2010, 2011, and 2012 in a subsample of 5 locations on the shelf where Deepwater Horizon oil exposure was confirmed. The analysis conservatively estimated a seagrass loss of 104.22 acres (42.18 ha) at these locations. Unexpectedly, the whole back barrier shelf experienced a net gain of 228 acres (92.27 ha) of seagrass between 2010 and 2011, representing a pause in the long-standing trend in seagrass declines in the Chandeleurs and indicating that oil exposure did not result in a shelf-wide catastrophe for seagrasses. Predictions for the impending disappearance of this seagrass resource in the near future may need to be reconsidered.

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 2023;00:1–13. © 2023 Newfields Companies, LLC. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

The Fundão Dam breach on November 5, 2015 (the “Event”) released tailings, water, soil/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 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’ concentration between unaffected soils/sediments and tailings samples. Radar charts of key parameters along with statistical comparisons to pre‐Event and not‐affected water ways 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/sediment related (indirect) impacts. Spatially and temporally aggregated radar charts and non‐parametric 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 2018/19 wet season, most of the direct and indirect parameters had returned to pre‐Event levels.