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Ca Ratios (ca + ratio)
Selected AbstractsRelative contributions from exposed inshore and estuarine nursery grounds to the recruitment of stone flounder, Platichthys bicoloratus, estimated using otolith Sr:Ca ratiosFISHERIES OCEANOGRAPHY, Issue 4 2000Yoh Yamashita In Sendai Bay, stone flounder larvae settle and spend their juvenile period in either shallow exposed inshore nursery grounds or estuarine nursery grounds. The purpose of this study is to examine the relative contributions of these two kinds of nursery grounds to the flounder population using otolith strontium:calcium ratios. Stone flounder juveniles were collected from both nursery grounds, and one- and two-year-old flounder were caught deeper in Sendai Bay. Sr and Ca content in the otoliths were measured by electron probe micro analysis. The Sr:Ca ratios in the otolith section corresponding to the early postsettlement period ranged from 3.06 to 3.85 for the exposed inshore areas with stable low temperature and high salinity conditions, and from 3.81 to 5.32 in brackish estuaries with high temperature and low salinity conditions but with large diel and tidal cyclical fluctuations. Values from an estuarine site with stable salinity ranged from 3.58 to 4.15 overlapping with both the above ranges. Rearing experiments supported our inference that the high otolith Sr:Ca ratios of juveniles inhabiting estuarine nursery grounds are attributable to higher temperature and physiological stress caused by the large diel temperature and salinity fluctuations within the estuaries. Estimation of the Sr:Ca ratio of recruited fish using the otolith section formed while in the nursery area showed that at least 20 out of 42 individuals examined originated from estuarine nursery grounds. The present study indicates that estuaries play an important role as nursery grounds for stone flounder, producing about half of the stock in spite of the small and restricted area compared with the wide expanse of the exposed inshore area. [source] Environmental signature in the otolith elemental fingerprint of the tapertail anchovy, Coilia mystus, from the Changjiang estuary, ChinaJOURNAL OF APPLIED ICHTHYOLOGY, Issue 5 2006J. Yang Summary The ontogenetic patterns of habitat use and the migratory history of the tapertail anchovy, Coilia mystus, collected in the Changjiang estuary around Chongming Island, China, were studied by examining the environmental signature in the otolith strontium (Sr) and calcium (Ca) fingerprints using electron probe microanalysis (EPMA). Our results suggest that the migration strategy of C. mystus is much more flexible than supposed in the literature to date. The spring spawning population of C. mystus from the studied area was found to consist of individuals with different migration histories. Although the tapertail anchovy seems to be an anadromous fish that spawns and hatches in a freshwater habitat, it can also use a freshwater environment in non-spawning seasons. The otolith EPMA of the elemental fingerprint (Sr x-ray maps and Sr : Ca ratios) is an environmental indicator that can be applied to the migratory ecology of other important diadromous species in China. [source] Application of otolith microchemistry to estimate the migratory history of Japanese eel Anguilla japonica on the Sanriku Coast of JapanJOURNAL OF APPLIED ICHTHYOLOGY, Issue 2 2004A. Kotake Summary The age and migratory history of the Japanese eel, Anguilla japonica Temminck & Schlegel, collected in Miyako Bay along the Sanriku coast of Japan, was examined using the otolith microstructure and analysis of strontium (Sr) and calcium (Ca) concentrations conducted with wavelength dispersive X-ray spectrometry by an electron microprobe. The line analysis of Sr : Ca ratios along the life history transect of each otolith showed a peak (ca. 15,17 × 10,3) which corresponded with the period of their leptocephalus and early glass eel stages in the ocean. The mean Sr : Ca ratios from the elver mark to the otolith edge indicated that there were eels with several general categories of migratory history, including sea eels that never entered freshwater (average Sr : Ca ratios, ,6.0 × 10,3), and others that entered freshwater for brief periods but returned to the estuary or bay. This evidence of the occurrence of sea eels in this northern area indicates that Japanese eels of the Sanriku coast do not necessarily migrate into freshwater rivers during recruitment as do glass eels at the beginning of their growth phase; even those that do enter freshwater may later return to the marine environment. Thus, anguillid eel migrations into freshwater are clearly not an obligatory migratory pathway, but rather a facultative catadromy with seawater or estuarine residents as an ecophenotype. [source] Annual trace element cycles in calcite,aragonite speleothems: evidence of drought in the western Mediterranean 1200,1100,yr,BP,JOURNAL OF QUATERNARY SCIENCE, Issue 5 2005Emily A. McMillan Abstract Each of two calcitic stalagmites from Grotte de Clamouse, Herault, southern France, displays a discrete aragonite layer dated at around 1100,yr,BP. The layer of fanning aragonite ray crystals is immediately preceded by calcite with Mg and Sr compositions that are uniquely high for the past 3,kyr. Trace element compositions close to the boundary between original aragonite and calcite are consistent with quasi-equilibrium partitioning of trace elements between the phases. Study of modern dripwaters demonstrates that pronounced covariation of Mg/Ca and Sr/Ca ratios in dripwater occurs owing to large amounts of calcite precipitation upflow of the drips that fed the stalagmites. Trace element to Ca ratios are enhanced during seasonally dry periods. Ion microprobe data demonstrate a pronounced covariation of trace elements, including Mg and Sr in calcite, and Sr, U and Ba in aragonite. The mean peak spacing is close to the long-term mean of annual growth rates determined by differences in U-series ages and so the trace element peaks are interpreted as annual. The trace element chemistry of the stalagmites on annual to inter-annual scales thus directly reflects the amounts of prior calcite precipitation, interpreted as an index of aridity. The longer-term context is a multi-decadal period of aridity (1200,1100,yr,BP) possibly correlated with an analogous episode in Central America. The arid period culminated in the nucleation of aragonite, but within a decade was followed by a return to precursor conditions. Copyright © 2005 John Wiley & Sons, Ltd. [source] Heathland restoration in The Netherlands: Effects of turf cutting depth on germination of Arnica montanaAPPLIED VEGETATION SCIENCE, Issue 2 2003Leon J.L. van der Berg Abstract. Germination experiments were conducted in a heathland after turf cutting and in a climate chamber to investigate the effects of turf cutting depth, aluminium toxicity and aluminium detoxification by humic acids and base cations on the germination and establishment of Arnica montana. Turfs were cut at three different depths, creating a gradient from organic to mineral soils. Germination and establishment of A. montana were negatively correlated with turf cutting depth. The removal of organic matter resulted in a major decrease in organic fraction of the soil and its nutrients. It also resulted in a considerable decrease in moisture content and humic acids. Additional liming after turf cutting increased germination and establishment in all plots and at all depths. Germination experiments under controlled conditions in a climate chamber revealed a significantly higher germination at low aluminium/calcium (Al:Ca) ratios. High Al:Ca ratios resulted in poor germination, suggesting Al toxicity. Addition of humic acids increased germination, even at high Al:Ca ratios, suggesting immobilization of Al by humic acids. It is concluded that turf cutting can have a marked effect on the success of heathland restoration. It results in the intended removal of the eutrophic layer but also in the unintentional removal of much of the buffering mechanisms and/or Al immobilizing compounds. Additional buffering and/or less deep turf cutting may be necessary to allow germination and establishment of rare herbaceous species such as A. montana. [source] | ||||||||||