Assessing the Effects of Non-Point Source Pollution on American Samoa’s Coral Reef Communities

Surveys were completed on Tutuila Island, American Samoa, to characterize reef development and assess the impacts of non-point source pollution on adjacent coral reefs at six sites. Multivariate analyses of benthic and coral community data found similar modern reef development at three locations; Aoa, Alofau, and Leone. These sites are situated in isolated bays with gentle sloping foundations. Aoa reefs had the highest estimates of crustose coralline algae cover and coral species richness, while Leone and Alofau showed high abundances of macroalgae and Porites corals. Aoa has the largest reef flat between watershed discharge and the reef slope, and the lowest human population density. Masefau and Fagaalu have a different geomorphology consisting of cemented staghorn coral fragments and steep slopes, however, benthic and coral communities were not similar. Benthic data suggest Fagaalu is heavily impacted compared with all other sites. Reef communities were assessed as bio-criteria indicators for waterbody health, using the EPA aquatic life use support designations of (1) fully supportive, (2) partially supportive, and (3) non-supportive for aquatic life. All sites resulted in a partially supportive ranking except Fagaalu, which was non-supportive. The results of this rapid assessment based upon relative benthic community measures are less desirable than long-term dataset analyses from monitoring programs, however it fills an important role for regulatory agencies required to report annual waterbody assessments. Future monitoring sites should be established to increase the number of replicates within each geological and physical setting to allow for meaningful comparisons along a gradient of hypothesized pollution levels.     

Soil characteristics, heavy metal availability and vegetation recovery at a former metallurgical landfill: Implications in risk assessment and site restoration

Pedological and botanical characteristics of a former metallurgical landfill were examined to assess the risks of heavy metals mobility and to evaluate remediation feasibility. In addition to very high heavy metals levels (Cu, Cr, Mn, Ni, Pb, Zn), the soil was characterized by a lack of clear horizonation, a relatively high pH, a high mineral and organic carbon contents, a low nitrogen level and a high C/N ratio. A two step sequential extraction showed that heavy metals were poorly labile (i.e. not soluble in diluted CaCl2), indicating that their leaching under natural conditions was probably very low. However, extraction with DTPA generated significant amounts of metals (mainly Pb and Cu), suggesting they were potentially mobilizable. A botanical survey of the area showed a biodiverse plant community (28 species and 11 families), with no obvious toxicity symptoms. Measurements of metal contents in dominant species confirmed that they were closely similar to those reported for species growing in unpolluted environments. Consequently, for an effective site restoration, indigenous species could be well suited to cope with local conditions in a phytostabilization strategy.     

Multiple disturbances accelerate clonal growth in a potentially monodominant bamboo

Organisms capable of rapid clonal growth sometimes monopolize newly freed space and resources. We hypothesize that sequential disturbances might change short-term clonal demography of these organisms in ways that promote formation of monotypic stands. We examined this hypothesis by studying the clonal response of Arundinaria gigantea (giant cane, a bamboo) to windstorm and fire. We studied giant cane growing in both a large tornado-blowdown gap and under forest canopy, in burned and unburned plots, using a split-block design. We measured density of giant cane ramets (culms) and calculated finite rates of increase (lamda) for populations of ramets over three years. Ramet density nearly doubled in stands subjected to both windstorm and fire; the high ramet densities that resulted could inhibit growth in other plants. In comparison, ramet density increased more slowly after windstorm alone, decreased after fire alone, and remained in stasis in controls. We predict that small, sparse stands of giant cane could spread and amalgamate to form dense, monotypic stands (called "canebrakes") that might influence fire return intervals and act as an alternative state to bottomland forest. Other clonal species may similarly form monotypic stands following successive disturbances via rapid clonal growth.     

Incorporating the perceptual range of animals into connectivity models

The perceptual range of an animal towards different landscape elements affects its movements through heterogeneous landscapes. However, empirical knowledge and modeling tools are lacking to assess the consequences of variation in the perceptual range for movement patterns and connectivity. In this study we tested how changes in the assumed perception of different landscape elements affect the outcomes of a connectivity model. We used an existing individual-based, spatially explicit model for the dispersal of Eurasian lynx (Lynx lynx). We systematically altered the perceptual range in which animals recognize forest fragments, water bodies or cities, as well as the probability that they respond to these landscape elements. Overall, increasing the perceptual range of the animals enhanced connectivity substantially, both qualitatively and quantitatively. An enhanced range of attraction to forests had the strongest impact, doubling immigration success; an enhanced range of attraction to rivers had a slightly lower impact; and an enhanced range of avoidance of cities had the lowest impact. Correcting the enhancement in connectivity by the abundance of each of the landscape elements in question reversed the results, indicating the potential sensitivity of connectivity models to rare landscape elements (in our case barriers such as cities). Qualitatively, the enhanced perception resulted in strong changes in movement patterns and connectivity. Furthermore, model results were highly parameter-specific and patch-specific. These results emphasize the need for further empirical research on the perceptual capabilities of different animals in different landscapes and conditions. They further indicate the usefulness of spatially explicit individual-based simulation models for recognizing consistent patterns that emerge, despite uncertainty regarding animals’ movement behavior. Altogether, this study demonstrates the need to extend the concept of ‘perceptual ranges’ beyond patch detection processes, to encompass the wide range of elements that can direct animal movements during dispersal through heterogeneous landscapes.     

Navigating the Perfect Storm: Research Strategies for Socialecological Systems in a Rapidly Evolving World

The ‘Perfect Storm’ metaphor describes a combination of events that causes a surprising or dramatic impact. It lends an evolutionary perspective to how social-ecological interactions change. Thus, we argue that an improved understanding of how social-ecological systems have evolved up to the present is necessary for the modelling, understanding and anticipation of current and future social-ecological systems. Here we consider the implications of an evolutionary perspective for designing research approaches. One desirable approach is the creation of multi-decadal records produced by integrating palaeoenvironmental, instrument and documentary sources at multiple spatial scales. We also consider the potential for improved analytical and modelling approaches by developing system dynamical, cellular and agent-based models, observing complex behaviour in social-ecological systems against which to test systems dynamical theory, and drawing better lessons from history. Alongside these is the need to find more appropriate ways to communicate complex systems, risk and uncertainty to the public and to policy-makers.