Hard or soft environmental systems?

Recent trends in lake and stream water quality modeling indicate a conflict between the search for improved accuracy through increasing model size and complexity, and the search for applicability through simplification of already existing models. Much of this conflict turns on the fact that that which can be simulated in principle issimply not matched by that which can be observed and verified in practice. This paper is concerned with that conflict. Its aim is to introduce and clarify some of the arguments surrounding two issues of key importance in resolving the conflict: uncertainty in the mathematical relationships hypothesized for a particular model (calibration and model structure identification); and uncertainty associated with the predictions obtained from the model (prediction error analysis). These are issues concerning the reliability of models and model-based forecasts. The paper argues, in particular, that there is an intimate relationship between prediction and model calibration. This relationship is especially important in accounting for uncertainty in the development and use of models. Using this argument it is possible to state a dilemma which captures some limiting features of both large and small models.     

来自印度Adayar河的重金属:渗透进入相邻的地下水含水层

引言 Adayar河是一条很短的河流(40km长),向西南方向流去,流经Chennai(北纬13°05',东经80°15'),从这里蜿蜒曲折大约13km后汇入孟加拉湾(图1).在河口地带它变得很宽,河口宽达2km.汇水面积约有800km2,其中大多数地方地势平坦,有岩层的露头.     

Combined sclerochronologic and oxygen isotope analysis of gastropod shells (Gibbula cineraria, North Sea): life-history traits and utility as a high-resolution environmental archive for kelp forests

The grey top-shell, Gibbula cineraria is a common member of temperate to cold water kelp forest communities, but its longevity and the age structure of its populations remains unresolved. Combined measurements of shell growth rates (sclerochronology) and oxygen isotope composition allow analysis of rate and timing of shell growth. Eight specimens were analyzed from the southern North Sea (near Helgoland, German Bight). Three age groups were identified but external measurements (width, height, ornamentation patterns and number of whorls) and shell weight are not adequate for ontogenetic age discrimination. Stable oxygen isotope data is consistent with shell growth during the interval from April to December in isotopic equilibrium with seawater, and growth increments exhibit strong tidal controls with fortnightly bundles well preserved. Reliable environmental proxy data (water temperature) can be extracted from the shell aragonite using conventional stable oxygen isotope analyses, with a temporal resolution of days attainable during intervals of maximum growth, but annual extremes are not always recorded in the shell. While demonstrating the utility of G. cineraria as a environmental and potential paleoenvironmental proxy for kelp forest habitats, its longevity has been significantly overestimated.     

Expanding marine protected areas to include degraded coral reefs

Marine protected areas (MPAs) are a commonly applied solution to coral reef degradation, yet coral reefs continue to decline worldwide. We argue that expanding the range of MPAs to include degraded reefs (DR‐MPA) could help reverse this trend. This approach requires new ecological criteria for MPA design, siting, and management. Rather than focusing solely on preserving healthy reefs, our approach focuses on the potential for biodiversity recovery and renewal of ecosystem services. The new criteria would help identify sites with the highest potential for recovery and the greatest resistance to future threats (e.g., increased temperature and acidification) and sites that contribute to MPA connectivity. The DR‐MPA approach is a compliment rather than a substitute for traditional MPA design approaches. We believe that the DR‐MPA approach can enhance the natural, or restoration‐assisted, recovery of DRs and their ecosystem services; increase total reef area available for protection; promote more resilient and better‐connected MPA networks; and improve conditions for human communities dependent on MPA ecosystem services.     

Exploited species impacts on trophic linkages along reef-seagrass interfaces in the Florida Keys

The removal of fish biomass by extensive commercial and recreational fishing has been hypothesized to drastically alter the strength of trophic linkages among adjacent habitats. We evaluated the effects of removing predatory fishes on trophic transfers between coral reefs and adjacent seagrass meadows by comparing fish community structure, grazing intensity, and invertebrate predation potential in predator-rich no-take sites and nearby predator-poor fished sites in the Florida Keys (USA). Exploited fishes were more abundant at the no-take sites than at the fished sites. Most of the exploited fishes were either omnivores or invertivores. More piscivores were recorded at no-take sites, but most (approximately 95%) were moderately fished and unexploited species (barracuda and bar jacks, respectively). Impacts of these consumers on lower trophic levels were modest. Herbivorous and smaller prey fish (< 10 cm total length) densities and seagrass grazing diminished with distance from reefs and were not negatively impacted by the elevated densities of exploited fishes at no-take sites. Predation by reef fishes on most tethered invertebrates was high, but exploited species impacts varied with prey type. The results of the study show that, even though abundances of reef-associated fishes have been reduced at fished sites, there is little evidence that this has produced cascading trophic effects or interrupted cross-habitat energy exchanges between coral reefs and seagrasses.     

How do significant others influence our driving? A descriptive study of ego–alter dyads in a college population

Objectives: The purpose of this investigation was to describe the mutual influences between drivers and their significant others in a sample of college students, using a social network perspective.

Methods: A web-based survey was made of 65 dyads of drivers and their significant others, in order to examine areas of mutual influence concerning driving. Measures were taken of their frequency of risky driving, including how often they drive, talk on the cell phone, or text with each other while driving. They were also asked whether they have influenced or been influenced by each other to drive safer or in a more risky manner.

Results: The dyads were very similar in how frequently they drive as well as talk to each other on the phone while driving. However, they were unlikely to feel that their driving was influenced by each other, with only 17% of the drivers and 19% of the significant others saying that they have been overtly influenced by (or have influenced) each other's driving behavior often or most of the time. Yet, most (67.7% and 72.1%) said they have ever encouraged or been encouraged by each other to drive more safely, mainly by being told to reduce their speed. In both sets of drivers in these dyads, talking to and texting their significant other while driving was related to risky driving.

Conclusions: These findings suggest that a similarity exits in the driving patterns of young drivers and their significant others, especially concerning talking to each other on the phone while driving. The largest degree of overt social influence appears to center around avoidance of behaviors perceived to be associated with getting a traffic citation. Implications for safety campaign development and future research are presented.