Ecosystem recovery at hypersaline salt marsh remediation projects impacted by the Gulf War Oil Spill

ABSTRACT #1141405 The 1990 Gulf War Oil Spill was the largest marine oil spill in history, spilling an estimated 6–11 million barrels of crude oil into the Arabian Gulf and impacting approximately 800 km of shoreline in Saudi Arabia between the border with Kuwait and Abu Ali Island near Jubail. Many intertidal areas were heavily oiled, severely damaging salt marsh ecosystems and facilitating the growth of thick algal mats, which, in turn, created a physical barrier that restricted tidal exchange and prevented recolonization of marsh flora and fauna at these sites. Remediation projects have been ongoing since early 2010 at 19 project areas throughout the area of impact. Remediation activities are focused on refreshing existing or creating new tidal channels to restore hydrology and tilling the substrate to expose moderately oiled sediment and enhance the degradation of oil and break up laminate algal mats. Additional activities include removal of heavily oiled sediments, re-use of excavated unoiled and lightly oiled sediments to create additional topography in restored marshes, and vegetation planting in selected areas. Monitoring plots for long-term study were established at remediation sites, impacted but untreated sites (set-asides), and nearby reference (comparison) sites. Initial monitoring data were collected before and after remediation activities, which were primarily undertaken between 2010 and 2013. Biannual (spring and fall) monitoring was resumed in fall 2018 and will continue through spring 2022 to characterize ecosystem recovery at these sites. Based on results from fall 2018 and spring 2019, most remediation sites show some level of recovery, indicated by the return of annual vegetation and resident marsh invertebrates in lower elevation plots, and thinner algal mat types and insect burrowing activity at the upper elevations. While the lower portions of untreated sites are beginning to show recruitment of annual vegetation and invertebrates (e.g. crabs), thick, laminated algal mat cover occurs in the middle-upper elevations at untreated sites. Multimetric indices (MMIs) summarizing ecosystem health and stressors were developed to summarize recovery of these projects and evaluate progress at remediation sites relative to set-aside and comparison sites. MMI results indicate that remediation work was effective at reducing stressors in remediation sites compared to set-asides; however, the level of ecosystem recovery is variable across sites, in part depending on the time since restoration.

Multimetric Index to Evaluate Water Quality in Lagoons: A Biological and Geomorphological Approach

In recent years, Multimetric Indices (MMIs) have received a lot of attention thanks to their ability to develop integrative evaluations of water quality, particularly in lagoons. In this article, we propose a new MMI for determining the water quality in lagoons. The proposed index is composed of biotic and abiotic indicators, in particular macroinvertebrates, macrophytes and morphological indicators. The proposed index is based on a geometric representation of a phenomenon associated with an ecological system, the ecosystem elements are mapped as vertices of a network and the relationship between them is represented by the corresponding edges. We classify the status of water bodies, from very low to very high using the ecological quality ratio. We compare our index with different different indices that measure water quality, such as General Biotic Index (JP(G)), Macrophyte Index for River (MIR) and Shannon diversity index (H’) and validate our index with Pearson’s correlation coefficient. A strong correlation with the JP(G) and MIR indices (R2 = 0.8605 and R2=0.7661, respectively) is obtained. Although the proposed index is composed of other indices, the independence of the proposed index with respect to its component indices is proven and the structure of the geometric model associated to the proposed network is studied. A close relationship between the measure called medium articulation and the geometric model associated with the proposed index is highlighted, which allows to determine the missing relationships in the network using structural analysis. The proposed index presents a more comprehensive measure than most indices currently used and has the advantage in the scalability, since other existing indicators can be integrated into our model.

A Fish-Based Index of Biotic Integrity for Neotropical Rainforest Sandy Soil Streams—Southern Brazil

Multimetric indices are considered a low-cost and rapid means of assessing ecological integrity in streams. This study aimed to develop a fish-based Index of Biotic Integrity (N3S-IBI) in an agricultural region within the domains of the Atlantic rainforest in Brazil. We sampled 23 first-order streams and used large-scale land use and a local physical condition index to choose reference sites and to classify sites according to the disturbance level. N3S-IBI resulted in six metrics (Simpson’s dominance; the numbers of Characiformes and non-native individuals (Poecilia reticulata); and the percentages of Characidae species, intolerant insectivorous individuals, and tolerant species), contemplating tolerance, composition, abundance, richness, trophic habits, and origin. The low number of metrics contributes to a quick and easy biomonitoring process. N3S-IBI showed an excellent performance to separate least and most disturbed sites in our study area and can provide additional knowledge about anthropogenic effects within this impacted region. In fact, this tool could be utilized by managers to direct restoration actions for the most disturbed sites and to strengthen the preservation of the least disturbed sites.

A predictive index based on environmental filters for the bioassessment of river basins without reference areas in Atlantic Forest biome, Brazil

Biological assessments that use the reference condition approach are based on the concept of comparing a site's observed biology to sites where disturbance is minimal or absent. However, in many regions of the world, such areas are scarce or nonexistent. In this study, an alternative approach proposed by Chessman and Royal for bioassessment without reference areas based on environmental filters was tested in Brazil. This approach assumes that key environmental features act in the selection of potential colonists, from a regional pool of taxa, based on the ecological traits (tolerances) possessed by each taxon. We developed the approach by: 1) determining the regional pool, based on a large Atlantic Forest biome database; 2) selecting environmental filters (elevation, original vegetation and soil type); and 3) including information on the tolerance and preferences of aquatic insects to these filters. With this information we were able to determine the expected taxon under natural conditions and compare with observed taxon, developing a predictive index (Observed/Expected). Although the model was intended to predict the fauna in regions without reference sites, we included reference areas to test the model responsiveness, precision and sensitivity. Our results indicated that the index was able to discriminate impairment classes (F=56.9; p<0,001), it has high precision due to low standard deviation across reference sites values (SD=0.098) and high sensitivity due the correlation with environmental variables that are sensitive to human alteration (r=0.74, p<0.01). Also, it was strongly correlated with multimetric indices developed for multiple watersheds in the state, showing agreement between the methods in relation to ecological quality classification. Even though the predictive index had performed well in our study, we make some considerations that may help to improve its sensitivity of similar methods that are being tested using the environmental filters approach.