Search

Introduced species may be one of the penultimate threats facing natural systems in the Anthropocene. Unfortunately, some taxa, such as meiofauna (organisms that pass through a 1 mm mesh but are retained by a 45 μm mesh), are so challenging to study that the presence and impact of introduced meiofauna often goes undetected. Further, the impacts of introduced species are seldom placed into context with other structuring variables. Therefore, we used infaunal invertebrate communities of northern British Columbia, Canada, to quantify potential impacts of the introduced Cumacea Nippoleucon hinumensis upon the infaunal community and its closest endemic analog, Cumella vulgaris. We also compared the relative importance of this introduced species to other top-down (predation), bottom-up (competition), middle-out (predation/competition), and abiotic (tolerance) variables in structuring the infaunal community. We identified a significant negative correlation between N. hinumensis and C. vulgaris, suggesting that when placed in context with other structuring factors, the introduced species may have a minor, but detectable impact upon C. vulgaris populations. However, no relationship was observed between N. hinumensis and the infaunal community. The lack of a community-wide effect is potentially the result of the similarity between N. hinumensis and C. vulgaris life history strategies, enabling the introduced species to effectively replace C. vulgaris in the food web. As such, N. hinumensis may be best described as an invasive species, and not as merely non-native. Furthermore, the analytical techniques used here can be applied to other ecological systems to quantify and compare the impact of introduced species against other structuring forces. [ABSTRACT FROM AUTHOR]

Infaunal invertebrate communities are structured by various factors, including predation, resource availability, and environmental conditions. Given that these invertebrates live within sediment, it is not surprising that sediment properties play a critical role in many infaunal behaviours. When models explaining spatial and temporal variation in infaunal community composition are constructed using physical, biophysical, environmental, and sediment properties (salinity, detrital cover, elevation, particle size distribution, organic and water content, redox conditions, and penetrability), a considerable portion of the variation in the data is typically unaccounted for. This suggests that we do not fully understand all the variables that influence infaunal invertebrate communities. One suite of under-explored variables is the elemental composition/concentration of the sediments themselves. As such, we evaluated if sediment geochemistry improved model performance of the spatial variation in infaunal invertebrate communities on three intertidal mudflats in northern British Columbia, Canada. We observed that models including geochemistry data outperformed models that only included physical, biophysical, and environmental properties. Our results, therefore, suggest that some of the observed, and previously unaccounted for spatial variation in infaunal community composition may be a product of variation in sediment geochemistry. As such, sediment geochemistry should be accounted for when studying infaunal communities and assessing human impacts upon intertidal systems. [ABSTRACT FROM AUTHOR]

Marine heatwaves threaten the persistence of kelp forests globally. However, the observed responses of kelp forests to these events have been highly variable on local scales. Here, we synthesize distribution data from an environmentally diverse region to examine spatial patterns of canopy kelp persistence through an unprecedented marine heatwave. We show that, although often overlooked, temperature variation occurring at fine spatial scales (i.e., a few kilometers or less) can be a critical driver of kelp forest persistence during these events. Specifically, though kelp forests nearly all persisted toward the cool outer coast, inshore areas were >3°C warmer at the surface and experienced extensive kelp loss. Although temperatures remained cool at depths below the thermocline, kelp persistence in these thermal refugia was strongly constrained by biotic interactions, specifically urchin populations that increased during the heatwave and drove transitions to urchin barrens in deeper rocky habitat. Urchins were, however, largely absent from mixed sand and cobble benthos, leading to an unexpected association between bottom substrate and kelp forest persistence at inshore sites with warm surface waters. Our findings demonstrate both that warm microclimates increase the risk of habitat loss during marine heatwaves and that biotic interactions modified by these events will modulate the capacity of cool microclimates to serve as thermal refugia. [ABSTRACT FROM AUTHOR]

The Skeena River estuary supports commercial and culturally important salmon fisheries. However, considerable development has occurred in the area, and more has been proposed. If anthropogenic development degrades this critical habitat, the Skeena salmon run, that every year contributes $110 million to local economies, may be negatively impacted. Benthic invertebrates are common indicator species, as they often respond to disturbances before commercial species, warning of potential impacts. Unfortunately, invertebrates in the Skeena estuary have not been extensively studied, and we lack the detailed understanding of their community structure and dynamics for them to serve as indicator species in this region. Therefore, present conditions of the Skeena estuary are established here (invertebrate community, sediment conditions and food availability), in order to provide the data required both to anticipate changes associated with potential anthropogenic disturbances and to detect changes in this system if development occurs. [ABSTRACT FROM AUTHOR]

The bioaccumulation of Potentially Toxic Elements (PTEs) by benthic invertebrates in estuarine sediments is poorly understood. We sampled and analysed PTEs in sediments and benthic invertebrates from five sites in the Skeena Estuary (British Columbia, Canada), including sites adjacent to an abandoned cannery and a decommissioned papermill. Our aim was to elucidate baseline levels of PTE concentrations at sites that may be recovering from disturbance associated with prior industrial development and identify organisms that could be used to biomonitor the impact of future industrial developments. There was no indication that sediments of the salmon cannery were polluted, but acidic sediments adjacent to the papermill contained elevated concentrations of Cd, Cr, Hg and Pb. Benthic invertebrate community assemblages confirm that sediments have mostly recovered from prior industrial development associated with discharge of papermill sludge. Overall, we did not observe any relationship between PTE concentrations in the sediment and PTE concentrations in invertebrate tissues. However, we did observe a negative relationship between sediment pH and the Biota-Sediment Accumulation Factor (BSAF) of most PTEs for Oregon pill bugs (Gnorimosphaeroma oregonensis). G. oregonensis, observed at all sites, feeds on the fibers associated with the papermill discharge. Thus, G. oregonensis is a useful biomonitors for quantifying the impact of the decommissioned papermill, and are candidate biomonitors for assessing the impact of similar industrial development projects on intertidal ecosystems. [ABSTRACT FROM AUTHOR]

Efficiently evaluating industrial activities plays an essential role in determining the extent to which human–ecosystem interactions may lead to species loss, disrupted community dynamics, and degraded ecosystems. Intertidal habitats offer a unique opportunity in this regard, as they are species rich ecosystems that exhibit rapid community turnover and pronounced responses to ecological disturbances. In an attempt to use these dynamic communities to identify the impact storage of harvested logs is having on the Kitimat River estuary, surveys evaluating the biotic and abiotic conditions within surrounding mudflats were conducted. The intertidal mudflats of the Kitimat River Estuary varied spatially and temporally, and with differences in the infaunal community, as well as the abiotic sediment conditions between reference mudflats, and mudflats potentially impacted by logging activities. While these differences were pronounced, we cannot at this time link these differences to the logging activities at impacted sites. We also observed evidence that suggests that the infaunal community of these intertidal mudflats have changed substantially since the 1970s, with the establishment of a community of polychaetes, as well as the appearance of the invasive clam Mya arenaria, and the invasive Cumacea Nippoleucon hinumensis. Beyond contrasting impacted and reference mudflats, the current health of these mudflats, as indicated by the infaunal community assemblage, is currently unclear. More research is required to determine if organic enrichment has occurred at these habitats, as well as to further elucidate the current health of these intertidal mudflats. [ABSTRACT FROM AUTHOR]

High T[sub c] and J[sub c] YBa[sub 2]Cu[sub 3]O[sub 7-x] (YBCO) thin films have been formed by ex-situ processing of a spin coated organic sol-gel precursor based on a polymerized complex. To form the precursor we have reacted metal cations with a chelating organic acid, then formed polyesterified complexes through reaction with a polyhydroxy alcohol. This method permits a simple, cheap and reliable route to the fabrication of YBCO films. The value of J[sub c] achieved for the film deposited onto a LaAlO[sub 3] (100) substrate at 77 K under a zero field is routinely as high as 0.25 MA/cm² with T[sub c,zero] of 90.6 K. [ABSTRACT FROM AUTHOR]