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Optical remote sensing of chlorophyll a in case 2 waters by use of an adaptive two-band algorithm with optimal error properties
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A coastal ocean model intercomparison study for a three-dimensional idealised test case
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The spectral reflectance and transparency of river plume waters
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On the signatures of river outflow fronts in radar imagery
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Development and application of an algorithm for detecting Phaeocystis globosa blooms in the Case 2 Southern North Sea waters
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While mapping algal blooms from space is now well-established, mapping undesirable algal blooms in eutrophicated coastal waters raises further challenge in detecting individual phytoplankton species. In this paper, an algorithm is developed and tested for detecting Phaeocystis globosa blooms in the Southern North Sea. For this purpose, we first measured the light absorption properties of two phytoplankton groups, P. globosa and diatoms, in laboratory-controlled experiments. The main spectral difference between both groups was observed at 467 nm due to the absorption of the pigment chlorophyll c3 only present in P. globosa, suggesting that the absorption at 467 nm can be used to detect this alga in the field. A Phaeocystis-detection algorithm is proposed to retrieve chlorophyll c3 using either total absorption or water-leaving reflectance field data. Application of this algorithm to absorption and reflectance data from Phaeocystis-dominated natural communities shows positive results. Comparison with pigment concentrations and cell counts suggests that the algorithm can flag the presence of P. globosa and provide quantitative information above a chlorophyll c3 threshold of 0.3 mg m(-3) equivalent to a P. globosa cell density of 3 x 10(6) cells L(-1). Finally, the possibility of extrapolating this information to remote sensing reflectance data in these turbid waters is evaluated.
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Spectral variations of light scattering by marine particles in coastal waters, from visible to near infrared
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Field measurements and Mie calculations of the particulate light-scattering coefficient (b(p), in m(-1)) in the near-infrared and visible spectral domains are combined to quantify and model the effect of particulate absorption on the b(p) spectral variations. The case of particles of coastal origin and assumed to follow a Junge-type size distribution is considered. A simple power-law function closely reproduces the near-infrared b(p) spectral variations, with a spectral slope varying in the range 0.1-1.4. In the visible (e.g., 440 nm), particulate absorption effects systematically lead to b(p) values 5-30\% lower than values predicted using a power-law function fitted in the near infrared and extrapolated to 440 nm. The respective influences of the particle size distribution and composition are investigated for both mineral and organic particle populations. Finally, an empirical model derived from theoretical calculations closely reproduces the actual b(p) spectral variations from near-infrared to short visible wavelengths, taking into account particulate absorption effects.
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Chironomid distribution along a pollution gradient in Ethiopian rivers, and their potential for biological water quality monitoring.
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Water pollution resulting from the rapidly intensifying use of freshwater resources in Ethiopia is increasing the need for continuous follow-up and monitoring of the country’s aquatic ecosystems, in order to maintain their biological diversity and water quality. Chironomids (non-biting dipteran midges) are often used for biological water quality assessment because their larvae tend to respond rapidly and sensitively to changes in the aquatic environment. Larval chironomid assemblages from 37 sites in 20 Ethiopian rivers were analysed in 2010 to assess the relationship between species composition and water quality. Cluster analysis of local physical and chemical variables was used to classify sites into three different water quality classes: 15 sites were classified as not or slightly polluted, 16 as moderately polluted and six as heavily polluted. We recovered 21 chironomid taxa, representing three subfamilies, with Chironominae (13 taxa) making the largest contribution, followed by Tanypodinae and Orthocladinae (four taxa each). Polypedilum nubifer, P. wittei, Polypedilum type Wabe, Cryptochironomus sp. and Conchapelopia sp. were the dominant species in unpolluted or slightly polluted sites. Chironomus alluaudi and C. imicola were indicators of heavily polluted sites, typified by low (<2 mg l–1) concentrations of dissolved oxygen. Heavily polluted sites, such as the Modjo and Sebata rivers, also held a lower number of species and genera than less-impacted sites. Larval chironomid assemblages proved useful as indicators of river water quality in Ethiopia when taxa are identified at the species and/or genus level.
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BIOFRAG - a new database for analysing BIOdiversity responses to forest FRAGmentation.
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Habitat fragmentation studies have produced complex results that are challenging to synthesize. Inconsistencies among studies may result from variation in the choice of landscape metrics and response variables, which is often compounded by a lack of key statistical or methodological information. Collating primary datasets on biodiversity responses to fragmentation in a consistent and flexible database permits simple data retrieval for subsequent analyses. We present a relational database that links such field data to taxonomic nomenclature, spatial and temporal plot attributes, and environmental characteristics. Field assessments include measurements of the response(s) (e.g., presence, abundance, ground cover) of one or more species linked to plots in fragments within a partially forested landscape. The database currently holds 9830 unique species recorded in plots of 58 unique landscapes in six of eight realms: mammals 315, birds 1286, herptiles 460, insects 4521, spiders 204, other arthropods 85, gastropods 70, annelids 8, platyhelminthes 4, Onychophora 2, vascular plants 2112, nonvascular plants and lichens 320, and fungi 449. Three landscapes were sampled as long-term time series (>10 years). Seven hundred and eleven species are found in two or more landscapes. Consolidating the substantial amount of primary data available on biodiversity responses to fragmentation in the context of land-use change and natural disturbances is an essential part of understanding the effects of increasing anthropogenic pressures on land. The consistent format of this database facilitates testing of generalizations concerning biologic responses to fragmentation across diverse systems and taxa. It also allows the re-examination of existing datasets with alternative landscape metrics and robust statistical methods, for example, helping to address pseudo-replication problems. The database can thus help researchers in producing broad syntheses of the effects of land use. The database is dynamic and inclusive, and contributions from individual and large-scale data-collection efforts are welcome.
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Towards more equal footing in north–south biodiversity research: European and sub-Saharan viewpoints
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Research collaboration between developed countries from the northern hemisphere and developing countries in the southern hemisphere is essential for the understanding and protection of the major proportion of biodiversity located in the tropics. Focusing on the case of sub-Saharan Africa, we here assess the real involvement of northern versus southern contributors, and caution against unequal academic benefit sharing arising from non-commercial biodiversity research that may ultimately hamper sustainable knowledge transfer and long-term biodiversity conservation. We discuss possible drivers that may have led to a business of raw biodiversity data. While we fully support the current efforts to stamp out biopiracy through international biodiversity policies and agreements, we illustrate that such legislative frameworks may further constrain biodiversity research, especially in countries where regulations are poorly streamlined and bureaucracy remains rather inert. We therefore ask for workable solutions towards more equal footing in north–south biodiversity research, and propose a number of steps to transgress the current barriers towards a more fair and equitable sharing of benefits arising from biodiversity research.
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Evolution and Conservation of Central African Biodiversity: Priorities for Future Research and Education in the Congo Basin and Gulf of Guinea
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