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Jacco C. Kromkamp Edward P. Morris Rodney M. Forster Claire Honeywill Scott Hagerthey David M. Paterson 《Estuaries and Coasts》2006,29(2):183-196
Estimating biomass of microphytobenthos (MPB) on intertidal mud flats is extremely difficult due to their patchy occurrence,
especially at the scale of an entire mud flat. We tested two optical approaches that can be applied in situ: spectral reflectance
and chlorophyll fluorescence. These two approaches were applied in 4 European estuaries with different sediment characteristics.
At each site, paired replicate measurements of hyperspectral reflectance, chlorophyll fluorescence (after 15 min dark adaptation,
Fo
15), sediment water content, and chlorophylla concentrations were taken (including breakdown products: [chla+phaeo]). Sediments were further characterized by grain size and organic content analysis. The spectral signatures of tidal
flats dominated by benthic microalgae, mainly diatoms, could be easily distinguished from sites dominated by macrophytes;
we present a 3 waveband algorithm that can be used to detect the presence of macrophytes. The normalized difference vegetation
index (NDVI) was found to be most strongly correlated to sediment [chla+phaeo], except for the predominantly sandy Sylt stations. Fo
15 was also significantly correlated to sediment [chla+phaeo] in all but one grid (Sylt grid A). Our results suggest that the functional relationships (i.e., the slopes) between
NDVI or fluorescence and [chla+ phaeo] were not significantly different in the muddier grids, although the intercepts could differ significantly, especially
for Fo
15. This suggests a mismatch of the optical depth seen by the reflectometer or fluorometer and the depth sampled for pigment
analysis. NDVI appears to be a robust proxy for sediment [chla+phaeo] and can be used to quantify MPB biomass in muddy sediments of mid latitude estuaries. 相似文献
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Nicole A. Dijkman Henricus T.S. Boschker Lucas J. Stal Jacco C. Kromkamp 《Journal of Sea Research》2010,63(1):62-70
The beaches of the North Sea barrier island Schiermonnikoog (The Netherlands) are covered by microbial mats. Five types of microbial mats were distinguished based on a variety of characteristics, located along a transect perpendicular to the coast. Biomass abundance and composition of the microbial community were analyzed in these mats using pigments and phospholipid-derived fatty acids (PLFA) as biomarkers. Biomass per gram sediment increased more than six-fold from the mats at the low water mark to mats found at the edge of the dunes. Microscopic analysis revealed that the increase in biomass was accompanied by a change in species composition. Pigment- and PLFA composition reflected the changes in species composition. The PLFA data could be used to estimate the relative group abundance using the matrix factorization program CHEMTAX., whereas the pigment data were found not to be suitable for this purpose. 相似文献
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The ongoing human-induced emission of carbon dioxide (CO2) threatens to change the earth's climate. One possible way of decreasing CO2 emissions is to apply CO2 removal, which involves recovering of carbon dioxide from energy conversion processes and storing it outside the atmosphere. Since the 1980's, the possibilities for recovering CO2 from thermal power plants received increasing attention.In this study possible techniques of recovering CO2 from large-scale industrial processes are assessed.In some industrial processes, e.g. ammonia production, CO2 is recovered from the process streams to prevent it from interfering with the production process. The CO2 thus recovered can easily be dehydrated and compressed, at low cost. In the iron and steel industry, carbon dioxide can be recovered from blast furnace gas. In the petrochemical industry CO2 can be recovered from flue gases, using low-temperature heat for the separation process.Carbon dioxide can be recovered from large-scale industrial processes and in some cases the cost of recovery is significantly less than CO2 recovery from thermal power plants. Therefore this option should be studied further and should be considered if carbon dioxide removal is introduced on a wide scale. 相似文献
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We investigated whether climate change results in long-term changes in phytoplankton biomass and phenology in a turbid eutrophic
coastal plain estuary. Changes in annual mean chlorophyll a (chla) concentrations were studied for the period 1978–2006 in the eutrophic and turbid macro-tidal Western Scheldt estuary. Three
stations were investigated: WS1, at the mouth of the estuary; station WS6, halfway up the estuary; and station WS11, near
the Dutch–Belgian border near the upstream end of the estuary. No significant long-term changes in yearly averaged chla concentrations were observed in WS1 and WS6, but in WS11 the phytoplankton biomass decreased considerably. This is most likely
due to an increase in grazing pressure as a result of an improvement in the dissolved oxygen concentrations. Spectral analyses
revealed a possible periodicity of 7 years in the mean chla which was related to periodicity in river discharge. We also observed strong phenological responses in the timing of the
spring/summer bloom which were related to a well-documented increase in the temperature in the estuary. The fulcrum, the center
of gravity or the day at which 50% of the cumulative chla was reached during the year, advanced by 1–2 days/year. A similar trend was observed for the month in which the maximum bloom
was observed, with the exception of station WS1. All stations showed an earlier initiation of the bloom, whereas the day at
which the phytoplankton bloom was terminated also moved forward in time excepted for WS11. As a result, the bloom length decreased
at station WS1, remained the same at station WS6, and increased at WS11. This complicated pattern in bloom phenology demonstrates
the complex nature of ecosystem functioning in estuaries. 相似文献
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Jacco Vink 《Astronomy and Astrophysics Review》2012,20(1):49-120
Supernova remnants are beautiful astronomical objects that are also of high scientific interest, because they provide insights
into supernova explosion mechanisms, and because they are the likely sources of Galactic cosmic rays. X-ray observations are
an important means to study these objects. And in particular the advances made in X-ray imaging spectroscopy over the last
two decades has greatly increased our knowledge about supernova remnants. It has made it possible to map the products of fresh
nucleosynthesis, and resulted in the identification of regions near shock fronts that emit X-ray synchrotron radiation. Since
X-ray synchrotron radiation requires 10–100 TeV electrons, which lose their energies rapidly, the study of X-ray synchrotron
radiation has revealed those regions where active and rapid particle acceleration is taking place. 相似文献