Oregon State University

About: Oregon State University is a education organization based out in Corvallis, Oregon, United States. It is known for research contribution in the topics: Population & Climate change. The organization has 28192 authors who have published 64044 publications receiving 2634108 citations. The organization is also known as: Oregon Agricultural College & OSU.

Chronic nutrient enrichment increases prevalence and severity of coral disease and bleaching.

Abstract: Nutrient loading is one of the strongest drivers of marine habitat degradation. Yet, the link between nutrients and disease epizootics in marine organisms is often tenuous and supported only by correlative data. Here, we present experimental evidence that chronic nutrient exposure leads to increases in both disease prevalence and severity and coral bleaching in scleractinian corals, the major habitat-forming organisms in tropical reefs. Over 3 years, from June 2009 to June 2012, we continuously exposed areas of a coral reef to elevated levels of nitrogen and phosphorus. At the termination of the enrichment, we surveyed over 1200 scleractinian corals for signs of disease or bleaching. Siderastrea siderea corals within enrichment plots had a twofold increase in both the prevalence and severity of disease compared with corals in unenriched control plots. In addition, elevated nutrient loading increased coral bleaching; Agaricia spp. of corals exposed to nutrients suffered a 3.5-fold increase in bleaching frequency relative to control corals, providing empirical support for a hypothesized link between nutrient loading and bleaching-induced coral declines. However, 1 year later, after nutrient enrichment had been terminated for 10 months, there were no differences in coral disease or coral bleaching prevalence between the previously enriched and control treatments. Given that our experimental enrichments were well within the ranges of ambient nutrient concentrations found on many degraded reefs worldwide, these data provide strong empirical support to the idea that coastal nutrient loading is one of the major factors contributing to the increasing levels of both coral disease and coral bleaching. Yet, these data also suggest that simple improvements to water quality may be an effective way to mitigate some coral disease epizootics and the corresponding loss of coral cover in the future.

Error-correcting output coding corrects bias and variance

Abstract: Previous research has shown that a technique called error-correcting output coding (ECOC) can dramatically improve the classification accuracy of supervised learning algorithms that learn to classify data points into one of k ≫ 2 classes. This paper presents an investigation of why the ECOC technique works, particularly when employed with decision-tree learning algorithms. It shows that the ECOC method— like any form of voting or committee—can reduce the variance of the learning algorithm. Furthermore—unlike methods that simply combine multiple runs of the same learning algorithm—ECOC can correct for errors caused by the bias of the learning algorithm. Experiments show that this bias correction ability relies on the non-local behavior of C4.5.

Genetic comparisons reveal the same unknown bacterial lineages in Atlantic and Pacific bacterioplankton communities

Abstract: The phylogenetic diversity of oligotrophic bacterioplankton communities was compared with 16s ribosomal RNA genes cloned from natural populations. The data reported here extend a previous analysis of a bacterioplankton 16s rRNA clone library with 15 additional nucleic acid clone sequences, to provide information on 60 16s rDNA clones from hydrostation S in the Sargasso Sea. The data were compared to partial sequences of 37 Bacterial 16s rDNA clones reported from a surface picoplankton population collected at the Aloha station in the North Pacific gyre, and partial sequences of 29 Bacterial 16s rRNA clones obtained from sites near Bermuda and the western California Current. The results support reports of diverse groups of previously unknown a-proteobacteria, y-proteobacteria, and cyanobacteria in oceanic surface samples. Three novel lineages (SAR 12 1,125, 145) of proteobacteria were found. Several genes cloned from the Sargasso Sea were nearly identical to genes cloned from the Pacific samples, suggesting that these previously unrecognized bacteria groups (SAR 11, SAR 122, SAR86) are distributed widely in the surface waters of subtropical oceans. Two gene clones closely matched nucleotide sequences from the cultivated bacterial species Photobgxterium phosphoreum and Alteromonas haloplanktis. Oceanic biogeochemical processes are mediated by communities of microorganisms, which have often been viewed as “black boxes” in which most of the organisms present are not defined in taxonomic or phylogenetic terms. Uncertainties about the diversity and genetic structure of these natural bacterioplankton populations stem from the limitations of common microbial cultivation techniques, which typically support the growth of only a small subset of cells from the original sample (Ferguson et al. 1984; Jannasch and Jones 1959; Kogure et al. 1979). The use of ribosomal RNAs as markers for species diversity is providing a fresh approach for investigating the structure of microbial communities (Ward et al. 1992). Biases in the filtration and cloning procedures used in these studies are not yet well understood, but they clearly appear to be less limiting than the biases associated with microbial cultivation. Phylogenetic analyses provide information on bacterioplankton population diversity, as well as nucleic acid probes, which can be used to establish the significance of cultured microorganisms and to study the temporal and spatial distributions of microbial taxa in the oceans (DeLong 1992; Giovannoni et al. 1990a). The general utility of nucleic acid probes for the study of

Effects of Roads on Hydrology, Geomorphology, and Disturbance Patches in Stream Networks

Abstract: We outline a view of how road networks interact with stream networks at the landscape scale and, based on examples from recent and current research, illustrate how these interactions might affect biological and ecological processes in stream and riparian systems. At the landscape scale, certain definable geometric interactions involving peak flows ( floods) and debris flows (rapid movements of soil, sediment, and large wood down steep stream channels) are influenced by the arrangement of the road network relative to the stream network. Although disturbance patches are created by peak-flow and debris-flow disturbances in mountain landscapes without roads, roads can alter the landscape distributions of the starting and stopping points of debris flows, and they can alter the balance between the intensity of flood peaks and the stream net- work's resistance to change. We examined this conceptual model of interactions between road networks and stream networks based on observations from a number of studies in the H. J. Andrews Experimental Forest, Oregon (U.S.A.). Road networks appear to affect floods and debris flows and thus modify disturbance patch dynamics in stream and riparian networks in mountain landscapes. We speculate that these changes may in- fluence the rates and patterns of survival and recovery of disturbed patches in stream networks, affecting ec- osystem resilience, and we outline an approach for detecting such effects based on a patch dynamics perspec- tive. A field sampling scheme for detecting the magnitude of various road effects on stream and riparian ecology could involve (1) landscape stratification of inherent stream network susceptibility to floods or de- bris flows, (2) overlay of road and stream networks and creation of areas with various densities of road- stream crossings, emphasizing midslope road-stream crossings, and (3) designations of expected high- and low-impact stream segments based on numbers of upstream road-stream crossings where sampling of se- lected biological variables would be conducted.