The use of egg shells to infer the historical presence of copepods in alpine lakes     

Roland Knapp  Jodi Garton  Orlando Sarnelle 《Journal of Paleolimnology》2001,25(4):539-543

Copepods (Class Crustacea, Order Copepoda) are rarely included in paleoecological studies of lakes because they lack long-lasting exoskeletal remains. We describe the remains of eggs (egg shells) from Hesperodiaptomus copepods that are well preserved and abundant in alpine lake sediments. We demonstrate that the egg shells are the remains of Hesperodiaptomus eggs based on (i) the similar size and morphology of egg shells collected from sediments and those produced from the hatching of eggs obtained from laboratory-maintained Hesperodiaptomus, and (ii) the finding that diapausing eggs collected from lake sediments and hatched in the laboratory produced copepod nauplii that were morphologically indistinguishable from those hatched from eggs produced by laboratory-maintained Hesperodiaptomus. Egg shells were approximately two orders of magnitude more abundant in sediment cores than were viable diapausing eggs, making egg shells superior to viable diapausing eggs for quantifying the historical presence and abundance of Hesperodiaptomus. These results have important implications for alpine lake restoration as egg shells can be used to identify lakes in which Hesperodiaptomus was eliminated by fish introductions but has failed to return after fish eradication, lakes in which the pre-disturbance conditions are likely to be restored only by reintroductions of this important taxon.  相似文献   

The landscape factor in the formation of pollen records in lake sediments     

J.-M. Punning  T. Koff 《Journal of Paleolimnology》1997,18(1):33-44

Comprehensive paleobotanical and geochemical methods have been used to study the relationship between the spatial scale of landscape development and values of pollen influx to take the bog sediments. The spatial-temporal history of the four lakes and a bog was established in NE Estonia and pollen analyses of thier sediment were made. It was found that the influx of total arboreal pollen directly corresponds with the sizes of the sites studied, and varies with thier expansion or reduction.  相似文献   

Factors affecting the interpretation of caddisfly assemblages from Quaternary sediments     

Nancy E. Williams 《Journal of Paleolimnology》1988,1(4):241-248

The use of assemblages of caddisflies (Trichoptera) in paleoecology has been explored over the past ca. 12 years. During this time, sites in North America, Great Britain and Europe have been studied and progress has been made in both the mechanics of identification and in the understanding of factors relevant to the interpretation of assemblages of this wholly aquatic group. Quaternary caddisfly fossils are abundant and usually well-preserved in waterlaid sediments. Individual larval sclerites can be identified by reference to shapes, textures, colour patterns muscle scar patterns and setal distributions. The flat frontoclypeus is particularly easily identified.Study of the biological and distributional data relevant to a caddisfly assemblage yields information at two levels. First the probable local habitat and second the climate can be described. This information is derived from both modern collections and the literature as the morphology of species, and hence it is assumed their environmental requirements, have not changed during the Quaternary. Comparisons with fossil assemblages of other plant and animal groups suggest that there are important factors to be considered in interpreting caddisfly assemblages, particularly those from sediments deposited during cold periods: for example, caddisflies may be slower to migrate than certain terrestrial insects, in particular the beetles (Coleoptera), and some glacial assemblages may therefore be dominated by hangers on. Lotic and lentic species also may migrate at different rates.Although caddisflies have not yet been fully exploited as paleoecological indicators, they have already contributed to our understanding of past environments and warrant much greater use.  相似文献   

Peatland Initiation During the Holocene in Continental Western Canada   总被引：4，自引：0，他引：4  

Linda A. Halsey  Dale H. Vitt  Ilka E. Bauer 《Climatic change》1998,40(2):315-342

Today, the southern limit of peatlands in continental western Canada is largely limited by thermal seasonal aridity, although physiographic parameters of substrate texture, topography, and salinity also exsert important controls on the presence and absence of peatlands. Factors that control peatland distribution today also operated in the past, thus the initiation of peatlands during the Holocene was mainly limited by aridity and physiography. Calibrated radiocarbon dates of basal peat deposits from 90 locations across continental western Canada indicate that peat formation began approximately 8,000 to 9,000 years BP in nucleation zones along the upper elevations of the Montane region of Alberta and in northern Alberta uplands after an initial deglacial lag. Predictions of maximum early Holocene summer insolation by climate simulations provide a mechanism for limiting peatland establishment during the early Holocene. From 6,000 to 8,000 years ago, peat formation in continental western Canada expanded eastwards into Manitoba responding to decreases in summer insolation. Peatland expansion during the early Holocene was more extensive in Alberta than in Manitoba in response to a southwesterly shift in the Arctic front. The displacement of the Arctic front allowed for more frequent incursions of moist Pacific air into Alberta while limiting it in Manitoba. After 6,000 years BP, the trend of southeasterly peatland expansion continued. Peatlands are youngest in the southern Boreal Forest and Aspen Parkland Region as well as in the lower elevations of the Peace-Wapiti River drainage basin, forming over the last 3,000 to 4,000 years. Peatlands are also young in the lower elevations of the Hudson Bay Lowlands where peat initiation has been limited by timing of emergence from glacial rebound. The spatial and temporal distribution of peatland initiation during the Holocene is verified by existing pollen records and corroborates some simulated climate models.  相似文献   

贵州台江中寒武世凯里生物群古生态研究   总被引：1，自引：2，他引：1  

杨瑞东  赵元龙  毛家仁  聂爱国  陈笑媛 《沉积学报》2002,20(1):129-135

凯里生物群是世界三大布尔吉斯页岩型生物群之一。本文通过古生物个体埋藏保存情况、古生物个体生态学、沉积学和地球化学等的研究和分析,认为凯里生物群中大部分分子是从异地搬运到陆棚环境埋藏的。同时,提出了凯里生物群的埋藏机理模式和生态复原图。  相似文献   

Corals as speaking stones     

Borel Best  Maya 《Geologie en Mijnbouw》1999,78(2):141-145

Corals are animals living in shallow seas (where they may form coral reefs) or in the deep sea. Because they fossilize well, these stones inform us in detail about the geological past; not only about the history of the Earth as a whole (rotation, tectonics, sea-level changes), but also about past local environmental conditions in the sea. Joint research of marine biology and marine geology can therefore solve many questions about our changing world, and can be used to discover what factors cause deterioration of living coral reefs.  相似文献   

Paleoecological investigations of recent lake acidification in northern Florida     

P. Roger Sweets  Ray W. Bienert  Thomas L. Crisman  Michael W. Binford 《Journal of Paleolimnology》1990,4(2):103-137

Thirty-two northern Florida lakes were analyzed to construct a transfer function relating surface sediment diatom assemblages to lakewater pH (R ² =0.89, s.e.=0.34). A paleoecological analysis of sediment cores from six of these lakes indicated that two have become more acidic in the last 50 years. The diatom inferred (DI) pH of L. Barco has declined between 0.56–0.82 in the 1900's and DI ANC (acid neutralizing capacity) by 28–46 eq l^-1. The DI pH of nearby L. Suggs has declined 0.91 pH units and its DI ANC by 19 eq l^-1. The timing of the inferred acidification is synchronous with known increases in emissions of sulfates and nitrates that are associated with acidic precipitation. Also, the increasing accumulation of substances related to emissions from the burning of fossil fuels (e.g., Pb, PAH) co-occurs with the lowering of DI pH in the sedimentary record. However, other processes may have accounted for or contributed to recent lake acidification. For instance, the drawdown of local water tables by human consumption may decrease the inseepage of ANC to seepage lakes. Such an effect would be synchronous with increasing depositions of sulfate. There is also clear evidence that Florida lakes are naturally acidic. Thus, paleoecological results indicate acidic deposition to be at certain contributor, but not necessarily the sole cause, of the recent further acidification of some naturally acidic Florida lakes.This is the tenth of a series of papers to be published by this journal which is a contribution of the Paleoecological Investigation of Recent Lake Acidification (PIRLA) project. Drs. D. F. Charles and D. R. Whitehead are guest editors for this series.  相似文献   

渤海湾盆地东部中新世馆陶组古植物群及其古气候分析     

汪舒  尹太举 《地质与资源》2019,28(6):503

通过孢粉图谱的绘制及孢粉数据的统计分析,得出渤东地区馆陶组植物孢粉在地层上的组合特征及气候演化特点.主要表现为：乔木层的演化分为两个阶段,馆陶组早期（孢粉组合带Ⅲ、Ⅳ）——针叶树为主的混交林;馆陶组晚期（孢粉组合带Ⅰ、Ⅱ）——落叶林含有许多亚热带成分.统计发现馆陶组湿生植物明显多于旱生植物,喜热植物明显多于喜温植物,具有典型的亚热带季风气候特点.挑选典型孢粉计算得到S/A、E-T两个参数,详细地刻画了样品点间的气候变化,证明馆陶组气候波动频繁,气候以湿热为主.  相似文献   

Plant–Arthropod Associations from the Lower Miocene of the Most Basin in Northern Bohemia (Czech Republic): A Preliminary Report     

Jakub PROKOP  Torsten Wappler  Stanislav Knor  Zlatko Kva?ek 《《地质学报》英文版》2010,84(4):903-914

Terrestrial plants and insects currently account for the majority of the Earth's biodiversity, and approximately half of insect species are herbivores. Thus, insects and plants share ancient associations that date back more than 400 Myr. However, investigations of their past interactions are at the preliminary stages in Western Europe. Herein, we present the first results of our study of various feeding damage based on a dataset of nearly 3500 examined plant specimens from the Lower Miocene of the Lagerst?tte Bílina Mine in the Most Basin, Czech Republic. This site provides a unique view of the Neogene freshwater ecosystems. It has long been studied by scientists working in different branches of sedimentology, paleobotany, and paleozoology. The fossils are preserved in three characteristic horizons overlaying the coal seam (Clayey Superseam Horizon, Delta Sandy Horizon, and Lake Clayey Horizon), reflecting paleoenvironmental changes in a short time period of development. The trace fossils are classified as functional feeding groups or “guilds”, without searching for a direct cause or a recent analog host relation. Approximately 23% of specimens of dicotyledonous plant leaves were found to be damaged and associated with some leaf “morphotypes”. Deciduous plant–host taxa, and those with a chartaceous texture typical of riparian habitats, were frequently damaged, such as Populus, recorded with two species Populus zaddachii and Populus populina (57.9% and 31% herbivory levels, respectively), followed by Acer, Alnus, and Carya, averaging almost 30% of damaged leaves/leaflets. There has been evidence of 60 damage types (DT) representing all functional feeding groups recorded at the Bílina Mine, including 12 types of leaf mines and 16 gall-type DT. In total, Lower Miocene of the Lagerst?tte Bílina Mine exhibits a high level of external foliage feeding types (23.7%), and a low level of more specialized DT, such as galls (4.3%) and leaf mines (<1%). A broader comparison based on DT of the main sedimentary environments shows significance supporting different biomes by frequency of damage levels and DT diversities.  相似文献   

Holocene carbon storage and testate amoeba community structure in treed peatlands of the western Hudson Bay Lowlands margin,Canada     

Marissa A. Davies  Jim W. Mclaughlin  Maara S. Packalen  Sarah A. Finkelstein 《第四纪科学杂志》2023,38(1):92-106

The Hudson Bay Lowlands (HBL) stores a significant proportion of the northern peatland carbon pool, and constraints on the factors controlling local-scale variation are needed to better predict soil carbon stocks. We investigated two treed peatland sites, a fen and a bog, to understand how local ecohydrological factors impacted long-term carbon storage. Ecohydrological conditions were reconstructed using quantitative water table depth reconstructions from testate amoebae (TA) and broad peat type classifications. We also linked these factors and carbon storage to changes in TA community structure through the investigation of morphological and functional traits. Both sites have high rates of peat vertical accretion during the warmer Middle Holocene. A shift to a drier, Sphagnum-dominated habitat after 7400 cal a bp at the bog site, however, led to lower apparent carbon accumulation rates (aCARs) than at the fen site. aCARs decreased with the transition to a cooler Late Holocene climate at both sites. Both sites have higher total carbon masses (kg m⁻²) than other more open and younger HBL localities, demonstrating the potential importance of treed peatlands in regional carbon storage. Shifts in the frequency of TA traits corresponded to changing ecohydrological conditions and provided insights into the role of TA in carbon storage.  相似文献