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Virginia E. Villafañe Paul J. Janknegt Marco de Graaff Ronald J. W. Visser Willem H. van de Poll Anita G. J. Buma E. Walter Helbling 《Marine Biology》2008,154(6):1021-1029
During austral summer 2006, experiments were carried out to evaluate the effects of ultraviolet radiation (UVR, 280–400 nm)
on carbon fixation of natural phytoplankton assemblages from Patagonia (Argentina). Surface water samples were collected (ca.
100 m offshore) at mid morning using an acid-cleaned (1 N HCl) dark container. The short-term impact of UVR (measured as radiocarbon
incorporation) was immediately assessed by exposing samples to three artificial illumination treatments: PAR (400–700 nm),
PAR + UV-A (320–700 nm), and PAR + UV-A + UV-B (280–700 nm). Pico-nanoplankton characterized the assemblages, and taxon-specific
pigment fingerprinting combined with CHEMTAX and supplemented with microscopic observations showed varied proportions of diatoms,
chlorophytes, and cyanobacteria throughout January–February 2006. Photosynthetic efficiency, as assessed through assimilation
numbers, was high [between 4.4 and 10.4 μg C (μg chl-a)−1 h−1], and it was probably favored by the supply of inorganic nutrients from the Chubut River. UVR-induced photoinhibition appeared
to be related to the taxonomic composition: in general, higher photoinhibition was observed when diatoms dominated, whereas
this was lower when samples were dominated by chlorophytes. Our data suggest that xanthophyll pigments might have provided
only limited protection in these already highlighted acclimated assemblages. 相似文献
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Brian Buma Jennifer K Costanza Kurt Riitters 《Environmental monitoring and assessment》2017,189(12):642
The scale of investigation for disturbance-influenced processes plays a critical role in theoretical assumptions about stability, variance, and equilibrium, as well as conservation reserve and long-term monitoring program design. Critical consideration of scale is required for robust planning designs, especially when anticipating future disturbances whose exact locations are unknown. This research quantified disturbance proportion and pattern (as contagion) at multiple scales across North America. This pattern of scale-associated variability can guide selection of study and management extents, for example, to minimize variance (measured as standard deviation) between any landscapes within an ecoregion. We identified the proportion and pattern of forest disturbance (30 m grain size) across multiple landscape extents up to 180 km2. We explored the variance in proportion of disturbed area and the pattern of that disturbance between landscapes (within an ecoregion) as a function of the landscape extent. In many ecoregions, variance between landscapes within an ecoregion was minimal at broad landscape extents (low standard deviation). Gap-dominated regions showed the least variance, while fire-dominated showed the largest. Intensively managed ecoregions displayed unique patterns. A majority of the ecoregions showed low variance between landscapes at some scale, indicating an appropriate extent for incorporating natural regimes and unknown future disturbances was identified. The quantification of the scales of disturbance at the ecoregion level provides guidance for individuals interested in anticipating future disturbances which will occur in unknown spatial locations. Information on the extents required to incorporate disturbance patterns into planning is crucial for that process. 相似文献
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Buma B 《Environmental monitoring and assessment》2012,184(6):3849-3860
Forest disturbances around the world have the potential to alter forest type and cover, with impacts on diversity, carbon
storage, and landscape composition. These disturbances, especially fire, are common and often large, making ground investigation
of forest recovery difficult. Remote sensing offers a means to monitor forest recovery in real time, over the entire landscape.
Typically, recovery monitoring via remote sensing consists of measuring vegetation indices (e.g., NDVI) or index-derived metrics,
with the assumption that recovery in NDVI (for example) is a meaningful measure of ecosystem recovery. This study tests that
assumption using MODIS 16-day imagery from 2000 to 2010 in the area of the Colorado’s Routt National Forest Hinman burn (2002)
and seedling density counts taken in the same area. Results indicate that NDVI is rarely correlated with forest recovery,
and is dominated by annual and perennial forb cover, although topography complicates analysis. Utility of NDVI as a means
to delineate areas of recovery or non-recovery are in doubt, as bootstrapped analysis indicates distinguishing power only
slightly better than random. NDVI in revegetation analyses should carefully consider the ecology and seasonal patterns of
the system in question. 相似文献
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Marampouti Christina Buma Anita G. J. de Boer M. Karin 《Environmental science and pollution research international》2021,28(4):3837-3851
Environmental Science and Pollution Research - Harmful algal blooms (HABs) are mostly phytoplankton blooms, which have detrimental environmental and socioeconomic impacts. The Mediterranean Sea due... 相似文献
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