Public bookmarks and private benefits: An analysis of incentives in social computing

Users of social computing websites are both producers and consumers of the information found on the site. This creates a novel problem for web-based software applications: how can website designers induce users to produce information that is useful for others? We study this question by interviewing users of the social bookmarking website del.icio.us. We find that for the users in our sample, metadata reflecting who bookmarked a webpage better supports information seeking than free-form keyword metadata (tags). We explain this finding by describing differences in the way that the design of del.icio.us motivates users to contribute by providing personal benefits for bookmarking and tagging.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/61317/1/1450440240_ftp.pd

Seasonal organic matter dynamics in the Great Barrier Reef lagoon: contribution of carbohydrates and proteins

Organic matter (OM) plays a fundamental role in sustaining the high productivity of coral reef ecosystems. Carbohydrates and proteins constitute two of the major chemical classes identified in the OM pool and are used as indicators of bioavailability due to their fast turn-over. We conducted three cruises across the southern shelf of the Great Barrier Reef (GBR) during the early dry, late dry and wet seasons in 2009–2010 to 1) assess the relative bioavailability of particulate (POM) and dissolved (DOM) organic matter, 2) track the temporal and spatial variability in the carbohydrate and protein contribution to the OM pool, and 3) assess factors influencing protein and carbohydrate fractions of the OM pool. Generally, higher concentrations of particulate carbohydrates were found during the wet season, while similar concentrations of particulate protein were found during the three seasons. Both the dissolved carbohydrates and proteins had highest levels during the early dry season and lowest during the wet season, suggesting seasonal variations in the chemical composition of the DOM pool. Spatially, carbohydrates showed higher concentrations at the inshore stations, while no clear spatial pattern was found for the protein concentrations. On average carbohydrates and proteins accounted for a similar fraction (13±5 and 12±6% respectively) of POM, while carbohydrates accounted for a smaller fraction of the DOM than the proteins (6±3 and 13±10%). This suggests that the POM bioavailability was similar between seasons, while the DOM bioavailability varied seasonally with highest levels during the early dry season. This demonstrates that carbohydrates and proteins in the GBR have temporal and spatial variations. Our statistical analysis showed that 1) both carbohydrates and proteins were related with the POM and DOM C:N:P stoichiometry, demonstrating that both bulk estimates (stoichiometry) and specific compounds (CHO and Prot) provide useful measures of OM bioavailability in the GBR and 2) the carbohydrates and proteins levels were controlled by the amount of nutrients and POM, which in this system is mainly of plankton origin. Overall this study shows that the POM and DOM pools contain highly bioavailable compounds and that carbohydrate and proteins could play an important role in sustaining the productivity of the GBR

Bottom Reflectance in Ocean Color Satellite Remote Sensing for Coral Reef Environments

Most ocean color algorithms are designed for optically deep waters, where the seafloor has little or no effect on remote sensing reflectance. This can lead to inaccurate retrievals of inherent optical properties (IOPs) in optically shallow water environments. Here, we investigate in situ hyperspectral bottom reflectance signatures and their separability for coral reef waters, when observed at the spectral resolutions of MODIS and SeaWiFS sensors. We use radiative transfer modeling to calculate the effects of bottom reflectance on the remote sensing reflectance signal, and assess detectability and discrimination of common coral reef bottom classes by clustering modeled remote sensing reflectance signals. We assess 8280 scenarios, including four IOPs, 23 depths and 45 bottom classes at MODIS and SeaWiFS bands. Our results show: (i) no significant contamination (Rrscorr 17 m for MODIS and >19 m for SeaWiFS for the brightest spectral reflectance substrate (light sand) in clear reef waters; and (ii) bottom cover classes can be combined into two distinct groups, “light” and “dark”, based on the modeled surface reflectance signals. This study establishes that it is possible to efficiently improve parameterization of bottom reflectance and water-column IOP retrievals in shallow water ocean color models for coral reef environments

Assessment of the relative risk of water quality to ecosystems of the Great Barrier Reef. A report to the Department of the Environment and Heritage Protection, Queensland Government, Brisbane - Report 13/28

A risk assessment method was developed and applied to the Great Barrier Reef (GBR) to provide robust and scientifically defensible information for policy makers and catchment managers on the key land-based pollutants of greatest risk to the health of the two main GBR ecosystems (coral reefs and seagrass beds). This information was used to inform management prioritisation for Reef Rescue 2 and Reef Plan 3. The risk assessment method needed to take account of the fact that catchment-associated risk will vary with distance from the river mouth, with coastal habitats nearest to river mouths most impacted by poor marine water quality. The main water quality pollutants of concern for the GBR are enhanced levels of suspended sediments, excess nutrients and pesticides added to the GBR lagoon from the adjacent catchments. Until recently, there has been insufficient knowledge about the relative exposure to and effects of these pollutants to guide effective prioritisation of the management of their sources

A database of marine phytoplankton abundance, biomass and species composition in Australian waters

There have been many individual phytoplankton datasets collected across Australia since the mid 1900s, but most are unavailable to the research community. We have searched archives, contacted researchers, and scanned the primary and grey literature to collate 3,621,847 records of marine phytoplankton species from Australian waters from 1844 to the present. Many of these are small datasets collected for local questions, but combined they provide over 170 years of data on phytoplankton communities in Australian waters. Units and taxonomy have been standardised, obviously erroneous data removed, and all metadata included. We have lodged this dataset with the Australian Ocean Data Network (http://portal.aodn.org.au/) allowing public access. The Australian Phytoplankton Database will be invaluable for global change studies, as it allows analysis of ecological indicators of climate change and eutrophication (e.g., changes in distribution; diatom:dinoflagellate ratios). In addition, the standardised conversion of abundance records to biomass provides modellers with quantifiable data to initialise and validate ecosystem models of lower marine trophic levels

Status of nutrient and sediment inputs from great Barrier Reef catchments and impacts on the Reef

This publication does not have an abstract. The first paragraph of this chapter is displayed as the abstract.\ud \ud Export of contaminants from the Great Barrier Reef Catchment\ud The Great Barrier Reef World Heritage Area (GBRWHA), the world's largest marine protected area, is bordered by a catchment of 423,000 km2. Each year, an average of 380 km3\ud of rain falls on the Great Barrier Reef (GBR) catchment (1 km3 = 1 billion m3 or 1 million megalitres). Of this, an average of 70 km3 runs off into the GBRWHA carrying eroded soil, nutrients and other materials. These materials influence water quality and the ecology of nearshore ecosystems in the GBRWHA. Rainfall and runoff are highly seasonal, with ca. 2/3 occurring during the summer (December-April) wet season and varies greatly from year-to- year under the influence of summer monsoon, the occurrence of El Nino events and the unpredictable occurrence of cyclones. Much of the runoff to the GBRWHA occurs during\ud short-lived flood events

Report on AIMS river nutrient data collected from downstream sites in major Queensland rivers draining to the Great Barrier Reef lagoon, 1987-2000

[Extract] Description of sampling program Streams draining to the GBR coast were generally sampled from bridges along the BruceHighway. This highway was convenient for most rivers, far enough downstream to incorporate the bulk of the catchment area and its inputs, but far enough upstream to be within freshwater and out of the estuary, at least during wet-season flows. The principal objective of the sampling program was to determine nutrient loads carried by the major rivers adjacent to the Central-Southern sections of the GBR, for use in the compilation of a nutrient budget of the GBR shelf. River-nutrient data available at the time of this program’s commencement (late 1980s) were poor and had mostly been collected during dry-season periods. The Australian Institute of Marine Science (AIMS) persuaded local professional staff to sample on our behalf where possible (e.g. Bureau of Sugar Experiment Stations[BSES], Tully) or paid local personnel a small per-sample fee for collection. Considerable funding assistance was provided by the Great Barrier Reef Marine Park Authority (GBRMPA). Six major rivers were sampled extensively, the Barron, South Johnstone, Tully, Herbert, Burdekin and Fitzroy. These rivers covered much of the Wet Tropics and the two main rivers of the Dry Tropics. Emphasis was given to wet-season sampling because of the crucial importance of this period to load calculations and because of the likely dynamic changes in nutrient concentrations during rainfall events. Collection personnel were asked to sample using a rainfall-mediated strategy, to sample sparsely until actual wet-season rainfall events, then to actively sample during these events, tapering off as the event concluded. Intensive sampling was then to be recommenced with the next rainfall event, though the whole wet season. This strategy worked better in some rivers than in others, the success largely dependent on the enthusiasm and commitment of the collection personnel. Clearly, rivers of the Wet Tropics, which have multiple wet-season discharge peaks, require greater sampling effort to capture these peaks than do rivers of the Dry Tropics, which typically only have one or two broad discharge peaks per year. A rank of these major data sets for their usefulness is given in Table 1. The author regularly visited these collection personnel, refreshing supplies and returning to AIMS with the frozen water samples for analysis. During these collection trips, the author also took samples of convenience at the major rivers and also at rivers and creeks in between these. The latter streams included Alligator Creek, Haughton River and Barratta Creek to the south, and North Johnstone River, Russell River and Mulgrave River to the north. Unfortunately, sampling was quite intermittent in these small collections, so these small datasets are of much less value than the major data sets. They typically involve dry-season rather than wet-season sampling

Exposure of inner-shelf reefs to nutrient enriched runoff entering the Great Barrier Reef Lagoon: post-European changes and the design of water quality targets

We used historical flood plume extent data (modelled) to quantify the typical spatial extent of the summer runoff–seawater mixing zone of the Great Barrier Reef (GBR) lagoon. Spatially explicit analysis of the variability of in situ chlorophyll a concentrations (observed) across the runoff–seawater mixing zone, then allowed us to explore regional differences in the nutrient enrichment impact of runoff events from the various river systems that drain the GBR catchment. We demonstrate the existence of a discernable north–south gradient along the length of the GBR, such that for equivalent runoff:seawater dilutions ratios, lower levels of nutrient enrichment (as indicated by chlorophyll a observations) result from the river systems that drain the relatively undisturbed northern areas of the GBR catchment, compared to more human-impacted central and south areas. We identify a strong correlation between this north–south enrichment gradient and the flood concentration of dissolved inorganic nitrogen (DIN) entrained by the various river systems. By substituting the nutrient enrichment characteristics of the human-impacted river discharges with those of the undisturbed northern rivers, we provide a means to compare the short-term enriching ‘footprint’ for existing runoff intrusions with those that are likely to have occurred under pre-European catchment conditions. We demonstrate that under pre-European conditions, the nutrient enriching impact from river runoff was likely to have been largely constrained within 1–2 km of the coast, whereas existing conditions support the impact of reefs some 20–30 km off the coast. By using the developed spatial relations, we show that for the heavily human-impacted river systems, reductions in the end-of-river concentrations of DIN in the order 50–80% are needed in order to restore parity with pre-European conditions. We discuss these results in regard to developing end-of-catchment water quality targets for the region

Water quality guidelines for the Great Barrier Reef World Heritage Area: a basis for development and preliminary values

The Australian and New Zealand Guidelines for Fresh and Marine Water Quality (ANZECC Guidelines) provide default national guideline values for a wide range of indicators of relevance to the protection of the ecological condition of natural waters. However, the ANZECC Guidelines also place a strong emphasis on the need to develop more locally relevant guidelines. Using a structured framework, this paper explores indicators and regional data sets that can be used to develop more locally relevant guidelines for the Great Barrier Reef World Heritage Area (GBRWHA). The paper focuses on the water quality impacts of adjacent catchments on the GBRWHA with the key stressors addressed being nutrients, sediments and agricultural chemicals. Indicators relevant to these stressors are discussed including both physico-chemical pressure indicators and biological condition indicators. Where adequate data sets are available, guideline values are proposed. Generally, data were much more readily available for physico-chemical pressure indicators than for biological condition indicators. Specifically, guideline values are proposed for the major nutrients nitrogen (N) and phosphorus (P) and for chlorophyll-a. More limited guidelines are proposed for sediment related indicators. For most agricultural chemicals, the ANZECC Guidelines are likely to remain the default of choice for some time but it is noted that there is data in the literature that could be used to develop more locally relevant guidelines

In the other 90%: phytoplankton responses to enhanced nutrient availability in the Great Barrier Reef lagoon

Our view of how water quality effects ecosystems of the Great Barrier Reef (GBR) is largely framed by observed or expected responses of large benthic organisms (corals, algae, seagrasses) to enhanced levels of dissolved nutrients, sediments and other pollutants in reef waters. In the case of nutrients, however, benthic organisms and communities are largely responding to materials which have cycled through and been transformed by pelagic communities dominated by micro-algae (phytoplankton), protozoa, flagellates and bacteria. Because GBR waters are characterised by high ambient light intensities and water temperatures, inputs of nutrients from both internal and external sources are rapidly taken up and converted to organic matter in inter-reefal waters. Phytoplankton growth, pelagic grazing and remineralisation rates are very rapid. Dominant phytoplankton species in GBR waters have in situ growth rates which range from not, vert, similar1 to several doublings per day. To a first approximation, phytoplankton communities and their constituent nutrient content turn over on a daily basis. Relative abundances of dissolved nutrient species strongly indicate N limitation of new biomass formation. Direct (15N) and indirect (14C) estimates of N demand by phytoplankton indicate dissolved inorganic N pools have turnover times on the order of hours to days. Turnover times for inorganic phosphorus in the water column range from hours to weeks. Because of the rapid assimilation of nutrients by plankton communities, biological responses in benthic communities to changed water quality are more likely driven (at several ecological levels) by organic matter derived from pelagic primary production than by dissolved nutrient stocks alone