Fiddler crab burrowing affects growth and production of the white mangrove (<Emphasis Type="Italic">Laguncularia racemosa</Emphasis>) in a restored Florida coastal marsh

Positive plant–animal interactions are important in community ecology, but relatively little attention has been paid to their effect on the production of mangroves, dominant halophytic trees in tropical coastal marshes. Here, the role of fiddler crab (Uca spp.) burrowing on the growth and production of the white mangrove, Laguncularia racemosa (<2 years old), was examined in a restored marsh in Tampa Bay, Florida (27°41.65 N, 82°30.34 W) with manipulative experiments from June 2006 to May 2007. Fiddler crab burrowing significantly increased mangrove height by 27%, trunk diameter by 25%, and leaf production by 15%, compared to mangroves in crab exclusion enclosures. Additionally, the exclusion of fiddler crabs significantly increased interstitial water salinity from 32.4 to 44.2, and decreased the oxidation–reduction potential of the low organic sediments, but did not affect soil pH or sulfide concentration. Mangrove height, trunk diameter, and leaf production along a transect that varied in crab burrow density were positively associated with the number of crab burrows. Further, the density of sympatric Spartina alterniflora shoots was positively correlated with crab burrow density along the transect. As in temperate marshes, fiddler crabs can have significant ecological effects on mangrove communities, serving as ecological engineers by modulating the amount of resources available to marsh plants, and by altering the physical, chemical, and biological state of these soft sediment communities. In restored coastal systems that typically have very poor sediment quality, techniques such as soil amendment could be used to facilitate a more natural interaction between crabs and mangroves in ecosystem development.     

Estimates of species- and ecosystem-level respiration of woody stems along an elevational gradient in the Luquillo Mountains, Puerto Rico

We measured CO₂ efflux from stems of seven subtropical tree species situated along an elevational gradient in the Luquillo Mountains, Puerto Rico and scaled these measurements up to the landscape level based on modeled and empirical relations. The most important determinants of ecosystem stem respiration were species composition and stem temperature. At a species scale, measured CO₂ efflux per unit bole surface area at a given temperature was highest in the early successional species Cecropia schreberiana and lowest in species that inhabit high elevations such as Micropholis garciniifolia and Tabebuia rigida. Carbon dioxide efflux rates followed a diel pattern that lagged approximately 6 h behind changes in sapwood temperatures. At an ecosystem scale, our simulation model indicates a decreasing trend of stem respiration rates with increasing elevation due to shifts in species composition, lower temperatures and reductions in branch surface area. The highest estimated stem respiration rates were present in the lowland tabonuco forest type and the lowest rates were present in the elfin forest type (mean 7.4 and 2.1 Mg C ha⁻¹ yr⁻¹, respectively). There was slight temperature-induced seasonal variation in simulated stem respiration rates at low elevations, with a maximum difference of 19% between the months of February and July. Our results coincide well with those of Odum and Jordan [Odum, H.T., Jordan, C.F., 1970. Metabolism and evapotranspiration of the lower forest in a giant plastic cylinder. In: Odum, H.T., Pigeon, R.F. (Eds.), A Tropical Rain Forest: A Study of Irradiation and Ecology at El Verde, Puerto Rico. U.S. Atomic Energy Commission, Oak Ridge, TN, pp. I165–I189] for the tabonuco forest type and extend their work by presenting estimates and spatial patterns of woody tissue respiration for the entire mountain rather than for a single forested plot.     

Temporal and Spatial Trends in Nutrient and Sediment Loading to Lake Tahoe,California‐Nevada,USA

Since 1980, the Lake Tahoe Interagency Monitoring Program (LTIMP) has provided stream‐discharge and water quality data—nitrogen (N), phosphorus (P), and suspended sediment—at more than 20 stations in Lake Tahoe Basin streams. To characterize the temporal and spatial patterns in nutrient and sediment loading to the lake, and improve the usefulness of the program and the existing database, we have (1) identified and corrected for sources of bias in the water quality database; (2) generated synthetic datasets for sediments and nutrients, and resampled to compare the accuracy and precision of different load calculation models; (3) using the best models, recalculated total annual loads over the period of record; (4) regressed total loads against total annual and annual maximum daily discharge, and tested for time trends in the residuals; (5) compared loads for different forms of N and P; and (6) tested constituent loads against land use‐land cover (LULC) variables using multiple regression. The results show (1) N and P loads are dominated by organic N and particulate P; (2) there are significant long‐term downward trends in some constituent loads of some streams; and (3) anthropogenic impervious surface is the most important LULC variable influencing water quality in basin streams. Many of our recommendations for changes in water quality monitoring and load calculation methods have been adopted by the LTIMP.     

Impacts of atmospheric pollution on the plant communities of British acid grasslands

Air pollutants are recognised as important agents of ecosystem change but few studies consider the effects of multiple pollutants and their interactions. Here we use ordination, constrained cluster analysis and indicator value analyses to identify potential environmental controls on species composition, ecological groupings and indicator species in a gradient study of UK acid grasslands. The community composition of these grasslands is related to climate, grazing, ozone exposure and nitrogen deposition, with evidence for an interaction between the ecological impacts of base cation and nitrogen deposition. Ozone is a key agent in species compositional change but is not associated with a reduction in species richness or diversity indices, showing the subtly different drivers on these two aspects of ecosystem degradation. Our results demonstrate the effects of multiple interacting pollutants, which may collectively have a greater impact than any individual agent.     

Hesperidin protects against aluminum-induced renal injury in rats via modulating MMP-9 and apoptosis: biochemical,histological, and ultrastructural study

Environmental Science and Pollution Research - Aluminum, one of the most abundant metallic elements, is known to be toxic to multiple organs including the kidneys. This study aimed to investigate...     

Odd fish abandon mixed-species groups when threatened

Summary In a field experiment, two juvenile size classes of striped parrotfish (Scarus iserti), stoplight light parrotfish (Sparisoma viride), and ocean surgeonfish (Acanthurus bahianus) were threatened by a model of a common predator (the trumpetfish, Aulostomus maculatus) while alone and in mixedspecies groups of 3–100 members. Striped parrotfish, which usually consitute the majority of a group, used the groups for protection. Stopight parrotfish, present in very low numbers, hid in the coral. Individuals of both species left a group sooner if it had fewer conspecifics. Small surgeonfish sought protection in groups, while larger individuals too big to be consumed by the trumpetfish, swam away alone. These results may be explained by differences in the protection derived from mixed-species groups, and particularly, by the high predation risk suffered by odd individuals.     

Identification and investigation of properties of social support

In response to the charge by House and Kahn (1985) that there is lack of specificity in conceptualization and measurement of the social support construct, this paper suggests the need to identify and specifically measure discrete properties of the previously identified dimensions (type and source) of social support. Properties are defined as what it is about combinations of source and type that needs to be measured. Based on literature reviews it is suggested that the relevant properties are amount of support, adequacy of support and number of providers of support. Measures are developed for each property. Data from 186 nurses were used to assess main and moderating effects of social support properties, workload and dying patients on emotional exhaustion and physical symptoms. As predicted, support adequacy was related to perceptions of lower workload. As single predictors, amount and adequacy of support reduced physical symptoms and emotional exhaustion. With amount and adequacy controlled, number of providers increased emotional exhaustion. Amount buffered the relationship between death and emotional exhaustion. Moderate levels of adequacy and number buffered the relationship between workload and exhaustion. Both adequacy and amount of support assisted in coping with patient death. In addition, a number of ‘reverse’ buffering and coping relationships were found. It was concluded that examination of different properties of social support increases our understanding of the impact of social support, and that further research needs to examine the simultaneous effects of various combinations of property, type and source of social support.     

Alpha-fetoprotein and acetylcholinesterase in twins discordant for neural tube defect

Twins concordant for elevated alpha-fetoprotein (AFP) and acetylcholinesterase (AChE) and discordant for neural tube defect (NTD) and sex are reported. A literature review reveals instances of termination of twin pregnancies with one normal and one abnormal fetus, partly based on concordant high AFP and positive AChE (although discordant on ultrasound examination). The levels of AFP and AChE in twin pregnancies are probably a function of the number of layers of fetal membranes separating twin sacs: dichorionic, diamniotic membranes allow transfer of AFP; monochorionic, diamniotic membranes allow transfer of both AFP and AChE. Cautious interpretation of biochemical findings and reliance on high resolution ultrasonography are suggested.