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This study explores the utility of a set of tablet-based personal computers in the K-12 science, technology, engineering, and mathematics classroom. Specifically, a lesson on food-chain dynamics and predator-prey population controls was designed on the Apple® iPad platform and delivered to three sophomore-level ecology classes (roughly 30 students per class with six iPads). Questionnaire feedback indicated that most students greatly enjoyed and were engaged in the activity. Further, student understanding of core concepts generally increased after participating in the tablet-based activity. Here, the iPad was essentially used as a data generator for a calculation-based activity, which is one of many potential applications of a class set of tablets. The collective results of this study indicate that student engagement and concept building is enhanced by immersive, tablet-based activities and a lesson plan that can be readily used in K-12 science classrooms is provided.

The balance between the storage of vascular plant carbon in soils, oxidation to carbon dioxide, and export via rivers affects calculations of the strength of terrestrial ecosystems as carbon sinks. The magnitude and timescale of the riverine export pathway are not well constrained. Here we use radiocarbon dating of lignin phenols to show that plant-derived carbon carried by suspended sediment of the Mekong River is very young, having been produced within the last 18 years. Further, this plant-derived carbon remains young during times of the year when bulk carbon varies from modern to over 3000 radiocarbon years old. Our results demonstrate that primary-production derivatives are exported rapidly and suggest that the age of riverine lignin is similar to estimates of the residence time of terrestrial organic carbon in tropical catchments. These results are relevant for modeling predictions of the influence of the terrestrial biosphere on atmospheric carbon dioxide levels.

Biogeochemical controls on the community structure of heterotrophic marine bacteria are not well understood, and these organisms play a critical role in the global carbon cycle. Through terminal restriction fragment length polymorpbism (T-RFLP) analyses of bacterial 16S rRNA genes along a zonal transect in the eastern subarctic North Pacific, variations in community structure were compared to commonly obtained chemical and biological oceanographic measurements. It was found that heterotrophic bacterial community structure was strongly, but independently, related to both phytoplanktonic production and light. Based on computer-simulated T-RFLP analyses of database 16S rRNA gene sequences, it appeared that the relationship between bacterial community structure and light observed along the transect was driven by the distribution of a-proteobacteria with phototrophic capabilities. In addition, experiments were conducted at sea to measure the growth of heterotrophic bacteria in response to amendments of amino acids, protein, N-acetyl glucosamine, and chitin. Variation in the response of heterotrophic bacteria in the experiments did not correlate significantly with variation in community structure along the transect, which suggests that the ability of the heterotrophic bacterial community to use specific components of the dissolved organic carbon reservoir was not related to its phylogenetic structure as detected by T-RFLR However, a possible relationship between community structure and the cycling of chitin is discussed. Overall, the results stress the importance of both heterotrophic and phototrophic metabolisms when considering environmental controls on the structure of bacterial communities in the sea.

The authors examine the sedimentary effects and compositional parameters of remnant organic matter in sea water. Topics include the oxic effect, carbon/surface area ratios, and oxygen penetration.

Sorption of organic matter to mineral surfaces controls lability and quantity of organic matter in marine sediments, stabilizes component molecules and diminishes their remineralization rates. Hence, internally labile molecules such as amino acids and simple sugars are preserved in marine deposits by sorption, which correlates organic carbon preservation in marine sediments to mineral surface deposition.

The volume and biomass production of heterotrophic bacterioplankton in the subarctic pacific was measured, and the results compared with those of phytoplankton during the years 1987 and 1988. The results show that bacterial biomass was equal to phytoplankton biomass. It is imperative to closely monitor heterotrophic bacterioplankton because they constitute a large reservoir of carbon and nitrogen, which are essential to preserve the ecosystem of the subarctic pacific.