Grassland intensification effects cascade to alter multifunctionality of wetlands within metaecosystems.

Sustainable agricultural intensification could improve ecosystem service multifunctionality, yet empirical evidence remains tenuous, especially regarding consequences for spatially coupled ecosystems connected by flows across ecosystem boundaries (i.e., metaecosystems). Here we aim to understand the effects of land-use intensification on multiple ecosystem services of spatially connected grasslands and wetlands, where management practices were applied to grasslands but not directly imposed to wetlands. We synthesize long-term datasets encompassing 53 physical, chemical, and biological indicators, comprising >11,000 field measurements. Our results reveal that intensification promotes high-quality forage and livestock production in both grasslands and wetlands, but at the expense of water quality regulation, methane mitigation, non-native species invasion resistance, and biodiversity. Land-use intensification weakens relationships among ecosystem services. The effects on grasslands cascade to alter multifunctionality of embedded natural wetlands within the metaecosystems to a similar extent. These results highlight the importance of considering spatial flows of resources and organisms when studying land-use intensification effects on metaecosystems as well as when designing grassland and wetland management practices to improve landscape multifunctionality.

Toxicological effects of the sunscreen UV filter, benzophenone-2, on planulae and in vitro cells of the coral, Stylophora pistillata.

Benzophenone-2 (BP-2) is an additive to personal-care products and commercial solutions that protects against the damaging effects of ultraviolet light. BP-2 is an "emerging contaminant of concern" that is often released as a pollutant through municipal and boat/ship wastewater discharges and landfill leachates, as well as through residential septic fields and unmanaged cesspits. Although BP-2 may be a contaminant on coral reefs, its environmental toxicity to reefs is unknown. This poses a potential management issue, since BP-2 is a known endocrine disruptor as well as a weak genotoxicant. We examined the effects of BP-2 on the larval form (planula) of the coral, Stylophora pistillata, as well as its toxicity to in vitro coral cells. BP-2 is a photo-toxicant; adverse effects are exacerbated in the light versus in darkness. Whether in darkness or light, BP-2 induced coral planulae to transform from a motile planktonic state to a deformed, sessile condition. Planulae exhibited an increasing rate of coral bleaching in response to increasing concentrations of BP-2. BP-2 is a genotoxicant to corals, exhibiting a strong positive relationship between DNA-AP lesions and increasing BP-2 concentrations. BP-2 exposure in the light induced extensive necrosis in both the epidermis and gastro dermis. In contrast, BP-2 exposure in darkness induced autophagy and autophagic cell death.The LC50 of BP-2 in the light for an 8 and 24 hour exposure was 120 parts per million (ppm) and 165 parts per billion (ppb), respectively. The LC50s for BP-2 in darkness for the same time points were 144 parts per million and 548 parts per billion [corrected].

Heat-stress and light-stress induce different cellular pathologies in the symbiotic dinoflagellate during coral bleaching.

Coral bleaching is a significant contributor to the worldwide degradation of coral reefs and is indicative of the termination of symbiosis between the coral host and its symbiotic algae (dinoflagellate; Symbiodinium sp. complex), usually by expulsion or xenophagy (symbiophagy) of its dinoflagellates. Herein, we provide evidence that during the earliest stages of environmentally induced bleaching, heat stress and light stress generate distinctly different pathomorphological changes in the chloroplasts, while a combined heat- and light-stress exposure induces both pathomorphologies; suggesting that these stressors act on the dinoflagellate by different mechanisms. Within the first 48 hours of a heat stress (32°C) under low-light conditions, heat stress induced decomposition of thylakoid structures before observation of extensive oxidative damage; thus it is the disorganization of the thylakoids that creates the conditions allowing photo-oxidative-stress. Conversely, during the first 48 hours of a light stress (2007 µmoles m(-2) s(-1) PAR) at 25°C, condensation or fusion of multiple thylakoid lamellae occurred coincidently with levels of oxidative damage products, implying that photo-oxidative stress causes the structural membrane damage within the chloroplasts. Exposure to combined heat- and light-stresses induced both pathomorphologies, confirming that these stressors acted on the dinoflagellate via different mechanisms. Within 72 hours of exposure to heat and/or light stresses, homeostatic processes (e.g., heat-shock protein and anti-oxidant enzyme response) were evident in the remaining intact dinoflagellates, regardless of the initiating stressor. Understanding the sequence of events during bleaching when triggered by different environmental stressors is important for predicting both severity and consequences of coral bleaching.

A survey of environmental pollutants and cellular-stress markers of Porites astreoides at six sites in St. John, U.S. Virgin Islands.

Coral communities along the coast of St. John, U.S. Virgin Islands have exhibited site-specific behavior in declines. In order to determine if these specific coral communities are stressed and whether a pollutant or environmental factor present at this site is a probable stressor, we surveyed six near-shore coral communities in St. John, USVI for environmental pollutants and to determine the cellular physiological condition of the coral, Porites astreoides. The six sites within St. John are Cruz Bay, Caneel Bay, Hawksnest Bay, Trunk Bay, Tektite Reef in Beehive Bay, and Red Point. Red Point was considered the reference site because of its abundance and diversity of species, and it was the furthest removed from down-stream and down-current anthropogenic activities. All sites showed distinct cellular-stress marker patterns, indicating that the physiological condition of each population was different. Populations at Cruz, Hawksnest, Trunk, and Tektite were stressed, as indicated by high levels of DNA lesions and expression of stress proteins. Hawksnest and Tektite were contaminated with polyaromatic hydrocarbons (PAHs), while Cruz was contaminated with semi-volatile organochlorines and nitrogen-based biocides. At least for Hawksnest and Tektite, stress-marker patterns were consistent with an exposure to PAHs. Fecal coliform levels were high in Cruz and Trunk, indicating fecal contamination, as well as consideration for management action. Results from this study serve as a justification for a more thorough and methodical investigation into the stressors responsible for declines of coral populations within St. John. Furthermore, this study supports the argument for the importance of local factors contributing to regional coral reef declines; that not all forces impacting coral are global.

In vitro cell-toxicity screening as an alternative animal model for coral toxicology: effects of heat stress, sulfide, rotenone, cyanide, and cuprous oxide on cell viability and mitochondrial function.

The logistics involved in obtaining and maintaining large numbers of corals hampers research on the toxicological effects of environmental contaminants for this ecologically and economically important taxon. A method for creating and culturing single-cell suspensions of viable coral cells was developed. Cell segregation/separation was based on specific cell densities and resulting cell cultures were viable for at least 2 mos. Low-density cells lacking symbiotic zooxanthallae and rich in mitochondria were isolated and cultured for toxicity studies. Cells were exposed to differing degrees or concentrations of heat stress, rotenone, cyanide, sulfide, and cuprous oxide. Cells were assayed for mitochondrial membrane potential using the fluorescent probe, JC-9, and for overall viability using the MTT/formazan spectrophotometric viability assay. Significant differences were observed between controls and treatments and the efficacy of this method was validated; only 2 cm(2) of tissue was required for a seven-point concentration-exposure series.

Cellular diagnostics and coral health: declining coral health in the Florida Keys.

Coral reefs within the Florida Keys are disappearing at an alarming rate. Coral cover in the Florida Keys National Marine Sanctuary declined by 38% from 1996 to 2000. In 2000, populations of Montastraea annularis at four sites near Molasses Reef within the Florida Keys National Marine Sanctuary and one reef within Biscayne National Park were sampled on a quarterly basis. Anecdotal observations showed corals at Alina's Reef in Biscayne National Park appeared healthy in March, but experienced an acute loss of coral cover by August. Cellular Diagnostic analysis indicated that Alina's Reef corals were in distress: they had been afflicted with a severe oxidative damaging and protein-denaturing stress that affected both the corals and their symbiotic zooxanthellae. This condition was associated with a significant xenobiotic detoxification response in both species, reflecting probable chemical contaminant exposure. These results demonstrate that applying a Cellular Diagnostic approach can be effective in helping to identify stress and its underlying causes, providing diagnostic and prognostic biomarkers of coral health.

Oxidative stress and seasonal coral bleaching.

During the past two decades, coral reefs have experienced extensive degradation worldwide. One etiology for this global degradation is a syndrome known as coral bleaching. Mass coral bleaching events are correlated with increased sea-surface temperatures, however, the cellular mechanism underlying this phenomenon is uncertain. To determine if oxidative stress plays a mechanistic role in the process of sea-surface temperature-related coral bleaching, we examined corals along a depth transect in the Florida Keys over a single season that was characterized by unusually high sea-surface temperatures. We observed strong positive correlations between accumulation of oxidative damage products and bleaching in corals over a year of sampling. High levels of antioxidant enzymes and small heat-shock proteins were negatively correlated with levels of oxidative damage products. Corals that experienced oxidative stress had higher chaperonin levels and protein turnover activity. Our results indicate that coral bleaching is tightly coupled to the antioxidant and cellular stress capacity of the symbiotic coral, supporting the mechanistic model that coral bleaching (zooxanthellae loss) may be a final strategy to defend corals from oxidative stress.

Cellular physiological assessment of bivalves after chronic exposure to spilled Exxon Valdez crude oil using a novel molecular diagnostic biotechnology.

The objective of this study was to determine the cellular physiological status of the bivalves Mya arenaria and Mytilus trossulus in an area experiencing a 10-yr chronic exposure of spilled Exxon Valdez crude oil in Prince William Sound. Bivalves were collected from well-characterized oiled and unoiled sites. We used a novel biotechnology (Environmental Cellular Diagnostic System) to determine (i) if bivalves were physiologically stressed, (ii) the nature of the altered physiological state, and (iii) whether the bivalves were responding to an exposure of polyaromatic hydrocarbons (PAH). Molecular diagnostic analysis indicated that bivalves at the oiled site were experiencing both oxidative and xenobiotic stress, resulting in increased protein turnover and chaperone activity. Bivalves from the impacted area were responding specifically to a PAH-xenobiotic exposure and accumulating protein-PAH adducts. Finally, species-specific responses were observed that could be related to the habitat preferences of each species. We conclude that bivalves inhabiting a site impacted by crude oil from the 1989 Exxon Valdez spill showed clear indications of cellular physiological stress.

LOCAL VARIATION IN THE GENETIC BASIS OF PAEDOMORPHOSIS IN THE SALAMANDER AMBYSTOMA TALPOIDEUM.

The hypothesis that local isolated populations differed in the genetic basis for life-history traits was tested in the salamander Ambystoma talpoideum. Genetic basis was defined as the specific genetic architecture (additive and nonadditive) that contributes, along with maternal and environmental factors, to the phenotype. All crosses within and between three populations were made to produce nine F1 populations. Nine within-population crosses produced the F2 generation. This design does not permit an estimation of the exact nature of the genetic basis (e.g., additive, nonadditive) for any trait within populations. However, hybrid dissimilarity in the F2 generation was taken as evidence of a different genetic basis for a trait in each population. The genetic basis of life-history pathway (metamorphosis vs. paedomorphosis) and per capita fecundity differed between two populations. The genetic basis of life-history pathway, per capita fecundity, survival, and growth rate was similar between the remaining sets of populations. This study and related ones (Semlitsch and Wilbur, 1989; Semlitsch et al., 1990) suggest that a heterochronic shift that causes rapid morphological evolution between metamorphosis and paedomorphosis (a macroevolutionary pattern) can evolve independently and does not require a macromutation or other nonmicroevolutionary mechanisms.