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991.
Juliane Scheder Max Engel Friederike Bungenstock Anna Pint Annette Siegmüller Stephan Schwank Helmut Brückner 《Journal of Coastal Conservation》2018,22(1):51-69
After the deceleration of the postglacial marine transgression, the German North Sea coast was subject to deposition of a complex pattern of subtidal to terrestrial facies. This study aims at reconstructing these facies changes in the ‘Land Wursten’ region (Lower Saxony) by focussing on so-called dwog horizons (incipient soil horizons of the pre-engineered salt marshes). We explore their implications for relative sea-level reconstructions and their indication for early settlement activities. Archive drilling data (1960, provided by the ‘Landesamt für Bergbau, Energie und Geologie’) were analysed to create five high-resolution stratigraphic cross sections. Three new drilling records were subjected to sedimentological and microfaunal investigations and interpreted to verify and calibrate the archive data. Two dwog horizons were found and 14C-AMS dated. We found basal salt marsh deposits inundated by a high-energy event and covered by tidal flat sediments. The thick tidal flat unit is again overlain by salt marsh deposits indicating the transition from a shallow marine to a terrestrial environment where dwogs were developed and covered by episodic marine incursions. The ages of the dwogs (1128–969 cal BC; cal AD 1426–1467) do not correlate with known layers of adjacent settlement sites and are critically discussed. However, we show that they correlate with phases of stagnant regional relative sea level (RSL) and can be used as RSL indicators. The combined archive and modern data provide valuable information for the RSL reconstruction and palaeoenvironmental changes. However, further research is recommended to accomplish more detailed information about coastal response during the Holocene sea-level changes and implications for settlement dynamics. 相似文献
992.
A series of experiments investigated the potential role of microbial mats in nutrition of the early settlement stages of Penaeus semisulcatus. From 3 days post-metamorphosis, the microbial mat supported high growth and survival rates in postlarvae, equivalent to
that supported by a control diet of Artemia nauplii and mussel. Examination of gut contents indicated that benthic postlarvae feed indiscriminately on the microbial
mat. However, when postlarvae were fed separated size-fractions of the microbial mat, only the fraction containing a high
concentration of infauna (mainly nematodes) was able to support the same growth as intact microbial mat. This appears to be
due to the low nitrogen content (0.4–0.9 mmol g−1) of the various size-fractions, compared to that of infauna (4.0 mmol g−1). The stable isotope composition of the dietary size-fractions and postlarval shrimp tissue supports the hypothesis that
the shrimp assimilated C and N primarily from the associated infauna. This may be due to selective feeding that is not apparent
from stomach contents, due to rapid digestion of fauna soft tissues, or to differential assimilation of infaunal prey relative
to other microbial mat components. The results demonstrate that microbial mats may support survival and growth in early-stage
penaeid shrimp postlarvae on intertidal mud flats. 相似文献
993.
Young green turtles (Chelonia mydas) spend their early lives as oceanic omnivores with a prevalence of animal prey. Once they settle into neritic habitats (recruitment),
they are thought to shift rapidly to an herbivorous diet, as revealed by studies in the Greater Caribbean. However, the precise
timing of the ontogenic dietary shift and the actual relevance of animal prey in the diet of neritic green turtles are poorly
known elsewhere. Stable isotopes of carbon, sulfur and nitrogen in the carapace scutes of 19 green turtles from Mauritania
(NW Africa), ranging from 26 to 102 cm in curved carapace length (CCLmin), were analyzed to test the hypothesis of a rapid
dietary shift after recruitment. Although the length of residence time in neritic habitats increased with turtle length, as
revealed by a significant correlation between turtle length and the δ13C and the δ34S of the scutes, comparison of the δ15N of the innermost and outermost layers of carapace scutes demonstrated that consumption of macrophytes did not always start
immediately after recruitment, and turtles often resumed an animal-based diet after starting to graze on seagrasses. As a
consequence, seagrass consumption did not increase gradually with turtle size and animal prey largely contributed to the diet
of turtles within the range 29–59 cm CCLmin (76–99% of assimilated nutrients). Seagrass consumption by turtles larger than
59 cm CCLmin was higher, but they still relied largely on animal prey (53–76% of assimilated nutrients). Thus, throughout
most of their neritic juvenile life, green turtles from NW Africa would be better classified as omnivores rather than herbivores.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
994.
Julianna L. Johns J. Andrew Roberts David L. Clark George W. Uetz 《Behavioral ecology and sociobiology》2009,64(1):13-18
Evolutionary conflicts of interest between the sexes are common, as mating tactics and strategies that increase fitness benefits
for one sex may incur costs for the other. As a consequence, antagonistic coevolution between the sexes often results in a
complex arms race between male persistence and female resistance. Coercive mating (e.g., forced copulation) likely benefits
males by increasing the probability of mating; however, costs to females may be high, including injury or even death. Here,
we report on a study of the use of fangs by males of the wolf spider Schizocosa ocreata (Hentz) during forcible mating with resistant females, which results in hemolymph loss and scar tissue formation in females.
Microscopic inspection revealed that fang wounds (evidenced by scar tissue) were absent on unmated (virgin) females but were
found on mated females and were significantly more frequent in coercively mated females. Experimental fang immobilization
studies found no difference in copulation success between experimental (fangs immobilized) and control (sham manipulation)
males. However, males that had use of their fangs had significantly longer copulation duration. These findings represent a
previously unknown male mating tactic in spiders and an unrecognized potential cost of mating for female spiders. 相似文献
995.
David F. Staples Mark L. Taper Brian Dennis Robert J. Boik 《Environmental and Ecological Statistics》2009,16(4):547-560
Estimates of a population’s growth rate and process variance from time-series data are often used to calculate risk metrics
such as the probability of quasi-extinction, but temporal correlations in the data from sampling error, intrinsic population
factors, or environmental conditions can bias process variance estimators and detrimentally affect risk predictions. It has
been claimed (McNamara and Harding, Ecol Lett 7:16–20, 2004) that estimates of the long-term variance that incorporate observed
temporal correlations in population growth are unaffected by sampling error; however, no estimation procedures were proposed
for time-series data. We develop a suite of such long-term variance estimators, and use simulated data with temporally autocorrelated
population growth and sampling error to evaluate their performance. In some cases, we get nearly unbiased long-term variance
estimates despite ignoring sampling error, but the utility of these estimators is questionable because of large estimation
uncertainty and difficulties in estimating correlation structure in practice. Process variance estimators that ignored temporal
correlations generally gave more precise estimates of the variability in population growth and of the probability of quasi-extinction.
We also found that the estimation of probability of quasi-extinction was greatly improved when quasi-extinction thresholds
were set relatively close to population levels. Because of precision concerns, we recommend using simple models for risk estimates
despite potential biases, and limiting inference to quantifying relative risk; e.g., changes in risk over time for a single
population or comparative risk among populations. 相似文献
996.
Many benthic colonial invertebrates have the ability to fuse and form chimeras with compatible colonies. Botryllid ascidians
are model organisms for the study of the evolution of and molecular basis for allorecognition, and fusion rates have been
determined for different populations and species by random sampling and fusion testing between individuals. However, natural
fusion rates over time have not been documented. Nine settlement panels were deployed in Salem Harbor, Massachusetts, USA
and Botrylloides violaceus settlement, growth, and fusion monitored from July to mid-August 2007. Seventy-three percent of the recruits observed fused
with at least one other colony, while 4% neither fused nor were overgrown. Multifused colonies were not observed to grow faster
than single colonies when growth was calculated as increase in size beyond the summation of fused entities; however, they
were significantly larger. These results suggest that larvae settle in clumps of compatible individuals, and that large subtidal
colonies may be the result of high numbers of fusions between compatible colonies. 相似文献
997.
Modelling habitat suitability of semi-aquatic vertebrates for large scale conservation purposes is a particularly challenging task, due to the fine-scale linearity of riverine habitats, and to the ecological continuum represented by the riparian and the aquatic ecosystems, on one side, and by a river and its tributaries, on the other. 相似文献
998.
This paper introduces an innovative modelling strategy aimed at simulating the main terms of net forest carbon budget (net primary production, NPP and net ecosystem exchange, NEE) in Tuscany (Central Italy). The strategy is based on the preliminary calibration and application of parametric and bio-geochemical models (C-Fix and BIOME-BGC, respectively), which simulate the behaviour of forest ecosystems close to equilibrium condition (climax). Next, the ratio of actual over-potential tree volume is computed as an indicator of ecosystem distance from climax and is combined with the model outputs to estimate the NPP and NEE of real forests. The per-pixel application of the new modelling strategy was made possible by the collection of several data layers (maps of forest type and volume, daily meteorological data and monthly normalized difference vegetation index (NDVI) images for the years 1999–2003) which served to characterize the eco-climatic and forest features of the region. The obtained estimates of forest NPP and NEE were evaluated against ground measurements of accumulated woody biomass and net carbon exchange. The results of these experiments testify the good potential of the proposed strategy and indicate some problem areas which should be the subject of future research. 相似文献
999.
Compilation of published and unpublished data shows acid precipitation to be more widespread in the Pacific coastal states than is generally recognized. Although information is scattered and discontinuous, precipitation is definitely acidic in the Los Angeles Basin and north-central california, and in the Puget Sound region in Washington. Acid rain occurrences have been observed in western and eastern Oregon, but data are inadequate for regional generalization. New stations currently being established in Washington and Oregon, largely in resposnse to the recently renewed activity of Mount St. Helens, will greatly facilitate assessment of precipitation acidity in the Northwest. 相似文献
1000.