Radiographic Signs of Type 3A Schatzker Fracture of Lateral Tibial Plateau

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Top-down and bottom-up factors in tidepool communities

Abstract Recent studies suggest that nutrient variation influences rocky intertidal community structure, however empirical evidence is rare. In the Gulf of Maine, tidepools that occur on seagull feeding roosts are potentially subjected to regular nutrient loading from seagull guano. The results of a survey conducted on Swan's Island, ME show that roost tidepools have very low macroinvertebrate and macroalgal diversity as well as very high phytoplankton biomass compared to non-roost tidepools. An experiment presented here tested basic food chain hypotheses in tidepool communities. These basic food chain models predict that in a tidepool with one trophic level (phytoplankton only), phytoplankton biomass will increase when nutrients are enriched. In contrast, these models predict that in two trophic level tidepools (phytoplankton and mussels) herbivory will prevent an increase in phytoplankton biomass when nutrients are enriched. A short term 2 Â 2 factorially designed field experiment was used to test this basic conceptual model using herbivory by mussels and enrichment with nitrogen as the main effects. The results of this investigation are consistent with the predictions of basic food chain models, and indicate that over the short time interval of a few days, herbivory by mussels is sufficient to maintain low phytoplankton levels following enrichment with nitrogen. Experimental enrichment with phosphorus in this study had no effect on phytoplankton biomass. The results of this study suggest that periodic pulses of nitrogen into tidepools will have little effect on phytoplankton biomass when mussels are present and that longer-term chronic nitrogen influxes may be driving the patterns of community structure in tidepools occurring on roosts.

Forage fish interactions: A symposium on creating the tools for ecosystem-based management of marine resources

Forage fish (FF) have a unique position within marine foodwebs and the development of sustainable harvest strategies for FF will be a critical step in advancing and implementing the broader, ecosystem-based management of marine systems. In all, 70 scientists from 16 nations gathered for a symposium on 12–14 November 2012 that was designed to address three key questions regarding the effective management of FF and their ecosystems: (i) how do environmental factors and predator–prey interactions drive the productivity and distribution of FF stocks across ecosystems worldwide, (ii) what are the economic and ecological costs and benefits of different FF management strategies, and (iii) do commonalities exist across ecosystems in terms of the effective management of FF exploitation

Variation in Community Structure across Vertical Intertidal Stress Gradients: How Does It Compare with Horizontal Variation at Different Scales?

In rocky intertidal habitats, the pronounced increase in environmental stress from low to high elevations greatly affects community structure, that is, the combined measure of species identity and their relative abundance. Recent studies have shown that ecological variation also occurs along the coastline at a variety of spatial scales. Little is known, however, on how vertical variation compares with horizontal variation measured at increasing spatial scales (in terms of sampling interval). Because broad-scale processes can generate geographical patterns in community structure, we tested the hypothesis that vertical ecological variation is higher than fine-scale horizontal variation but lower than broad-scale horizontal variation. To test this prediction, we compared the variation in community structure across intertidal elevations on rocky shores of Helgoland Island with independent estimates of horizontal variation measured at the scale of patches (quadrats separated by 10s of cm), sites (quadrats separated by a few m), and shores (quadrats separated by 100s to 1000s of m). The multivariate analyses done on community structure supported our prediction. Specifically, vertical variation was significantly higher than patch- and site-scale horizontal variation but lower than shore-scale horizontal variation. Similar patterns were found for the variation in abundance of foundation taxa such as Fucus spp. and Mastocarpus stellatus, suggesting that the effects of these canopy-forming algae, known to function as ecosystem engineers, may explain part of the observed variability in community structure. Our findings suggest that broad-scale processes affecting species performance increase ecological variability relative to the pervasive fine-scale patchiness already described for marine coasts and the well known variation caused by vertical stress gradients. Our results also indicate that experimental research aiming to understand community structure on marine shores should benefit from applying a multi-scale approach

Vital population rates across multiple spatial scales: A geostatistical analysis

Population and community level processes change across multiple spatial scales. Understanding these patterns and the factors that drive them are essential for the development of spatial approaches in fisheries management. Determining appropriately-resolved spatial scales is further complicated in temperate marine ecosystems by the generally high mobility and low site fidelity of temperate species compared to those in tropical reef systems. Spatial variability in per capita vital population rates (e.g., consumption, mortality, growth, survival) can directly affect the population level dynamics of managed species. Benthic habitat characteristics also change across spatial dimensions and may contribute to the differential spatial variability in vital rates. We used a set of bioenergetic equations to compute the daily per capita rate of consumption and mortality for individual groundfish species. These estimates used data from the US National Marine Fisheries Service Northeast Fisheries Science Center bottom trawls and food habits data sets. A geographic information system (GIS) was created to map these vital rates at multiple spatial scales. The spatial variability and spatial independence of vital rates were then explored using geostatistical techniques. Multivariate statistical approaches were also used to examine how habitat characteristics may be influencing spatial patterns in vital rates. Our results demonstrate the challenge of evaluating key population processes at the most appropriate spatial scales. Yet the demonstrated ability to integrate individual, population, and habitat information across multiple spatial scales should enhance our ability to manage our living marine resources. Keywords: spatial statistics, consumption, mortality, groundfish, fisheries management, essential fish habitat, NW Atlanti

The effects of nutrients and consumers on tidal pool communities

Patterns of community structure are thought to be driven by consumer processes in benthic marine systems. However, the conclusions of the qualitative and quantitative reviews presented in this dissertation suggest that nutrient variation may play a more important role than previously believed. The paucity of field experiments studying the role of nutrient variation in benthic marine communities is primarily due to the difficulties of manipulating nutrients in open systems. Tidepools along rocky shores provide a novel setting in which to study questions of trophic control, because they have discrete boundaries, which allow both nutrients and consumers to be manipulated easily. I studied the effect of nutrient enrichment in one trophic level (phytoplankton only) and two trophic level tidepool communities (phytoplankton and blue mussels, Mytilus edulis). Basic trophic interaction models predict that in one trophic level systems, nutrient enrichment will cause an increase in primary producer biomass, whereas in two trophic level systems, the models predict that herbivores will maintain low levels of producer biomass, resulting in no net increase in producer biomass. The results of a short time course experiment supported this model. Two subsequent experiments tested a modified model, which was developed to predict the effect of sustained nutrient enrichment over a summer season. The modified model predicted that primary producer biomass would increase with nutrient enrichment in both one and two trophic level systems. Furthermore, the modified model predicted that the increase in producer biomass in one trophic level systems would be due to an increase in large, competitively superior, phytoplankton cells, whereas the increase in producer biomass in two trophic level systems would be due to an increase in small phytoplankton cells that mussels are unable to capture. The experiments that tested the modified model produced mixed results, suggesting that basic trophic interaction models are an insufficient predictor of community structure in tidepool systems. More complex models that incorporate interactions between phytoplankton and bacterioplankton, seasonal variation in consumer-driven nutrient recycling, and variation in physical parameters that affect nutrient availability, are necessary to understand tidepool community structure

Radiographic Signs Of Type 3A Schatzker Fracture Of Lateral Tibial Plateau

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Transphyseal Fracture of the Distal Humerus in a Neonate

[West J Emerg Med. 2012;12(2):173.