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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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Until recently, bryozoans have not been used as indicators for changes in bottom communities or climate control in the North Sea Basin, despite a 200-year history of bryozoan collecting. The epizoobiontic bryozoan fauna of Flustra foliacea (Linnaeus, 1758) was analysed on 51 sample stations kept in four German museums. The samples cover the entire North Sea and different time periods (1776–2008, mainly the period of 1904/1905 compared to 1980–87). Cluster analysis shows a differentiation into a northern and a southern North Sea assemblage. The northern assemblage is characterized by Amphiblestrum flemingii (Busk, 1854), Callopora dumerilii (Audouin, 1826) and Tricellaria ternata (Ellis & Solander, 1786), while the southern North Sea is characterized by Electra pilosa (Linnaeus, 1767), Crisia eburnea (Linnaeus, 1758) and Plagioecia patina (Lamarck, 1816). Spatial separation approximately follows the 50 m depth contour. The temporal distribution patterns of bryozoans are discussed in terms of NAO (North Atlantic Oscillation) and temperature variations. 相似文献
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Biosecurity management allows countries to meet a number of international obligations and provides some protection from potential degradation of environmental, economic, social and cultural values. Ocean governance relies on the precepts of ecologically sustainable development to manage the multiple uses in the coastal zone. The increasing reliance on aquaculture to provide food security and economic development has led to an increase in the use of non-native target species grown as food sources. Increased economic activity has led to shifting trade patterns and increased efficiencies in vessels with the resulting increase in the number of introduced marine species via ballast water and hull fouling. Herein we review the different marine biosecurity strategies and legislation that have been implemented internationally and locally that aid in preventing and managing introduced marine species, with some attention to Australia and New Zealand as examples. Typical tools being used include quarantine, Import Health Standards, voluntary cleaning guidelines, and risk assessment, all of which aim to prevent introductions. 相似文献
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The impact of rain and spray on the ocean disturbs the sea surface and generates underwater ambient noise. The short scale roughness is influenced by impacting drops due to the momentum transfer. Radar and sonar signals are scattered by the short elements of the sea surface. Spray and rain impact change their characteristics, and consequently affect radar and sonar backscatter. In situ measurements of rain and spray impact are necessary to study their effects on the sea surface. Accurate sea measurements of rain momentum fluxes and drop size distributions are a complex problem, especially on buoys. A new measuring technique has been developed using hydrophones. Exposed to precipitation, these instruments are affected directly by the impact of rain. A drop falling on the hydrophone deforms its surface and is sensed by a piezoelectric transducer. The voltage output of the sensor is a rapidly decaying oscillation. The integral value of this signal is a measure of the drop momentum, and the drop size can be deduced. Laboratory studies of defined drops as well as field measurements of natural rain have shown that hydrophones can be used to determine drop momentums and drop size distributions. Based on simultaneous rain measurements by a Joss-Waldvogel Disdrometer and a hydrophone, an analytical function has been derived which relates drop size and hydrophone voltage output 相似文献
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Johanna Forster Peter W. Schuhmann Iain R. Lake Andrew R. Watkinson Jennifer A. Gill 《Climatic change》2012,114(3-4):745-768
Climate change could have major implications for the global tourism industry if changing environmental conditions alter the attractiveness of holiday destinations. Countries with economies dependent on tourism and with tourism industries reliant on vulnerable natural resources are likely to be particularly at risk. We investigate the implications that climate-induced variations in Atlantic hurricane activity may have for the tourism-dependent Caribbean island of Anguilla. Three hundred tourists completed standardised questionnaires and participated in a choice experiment to determine the influence hurricane risk has on their risk perceptions and decisions regarding holiday preferences. The hurricane season had been considered by 40?% of respondents when making their holiday choice, and the beaches, climate and tranquility of the island were more important than coral reef-based recreational activities in determining holiday destination choice. Choice models demonstrated that respondents were significantly less likely to choose holiday options where hurricane risk is perceived to increase, and significantly more likely to choose options that offered financial compensation for increased risk. However, these choices and decisions varied among demographic groups, with older visitors, Americans, and people who prioritize beach-based activities tending to be most concerned about hurricanes. These groups comprise a significant component of the island’s current clientele, suggesting that perceived increases in hurricane risk may have important implications for the tourism economy of Anguilla and similar destinations. Improved protection of key environmental features (e.g. beaches) may be necessary to enhance resilience to potential future climate impacts. 相似文献
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Ronald C. Chaney Marnie D. Chapman William Miller III 《Marine Georesources & Geotechnology》2013,31(3):333-339
Geotechnical Aspects of Coastal and Offshore Structures. Edited by Yudhair and A. S. Balasubramaniam. Proceedings of the Symposium on Geotechnical Aspects of Coastal and Offshore Structures, Bangkok, December 14–18,1981. Rotterdam: A. A. Balkema, 1983. 280 pp. $40.00. The Seaside Naturalist: A Guide to Nature Study at the Seashore. Written and illustrated by D. A. Coulombe. Englewood Cliffs, N.J.: Prentice‐Hall, Inc., 1984. 246 pp. $12.95. Ichnology, Trace Fossils in Sedimentology and Stratigraphy. By A. A. Ekdale, R. G. Bromley, and S. G. Pemberton. Society of Economic Paleontologists and Mineralogists, Short Course No. 15. Tulsa, Okla.: S.E.P.M., 1984. 317 pp. S.E.P.M. members, $16.00; non‐members, $20.00. 相似文献