Swamp Lake Research Articles

The environmental transformation mechanism of the coal- and oil shale-bearing interval in the Eocene Dalianhe Formation, Yilan Basin, Northeast China

Assemblages of multiple organic matter (OM)-related sedimentary energy systems are common in the Eocene nonmarine basins of Northeast China. During the Middle Eocene Climatic Optimum, oil shale developed in large quantities in the Yilan Basin. Numerous scientific papers have concentrated on the sedimentary cycle and industrial quality of the coal- and oil shale-bearing intervals, whereas few studies have studied the genetic environmental transformation mechanism of the coal and oil shale deposits. The Dalianhe Formation cover thick oil shale member and coal unit, which is a natural archive for studying the environmental evolution of lake swamp systems. In the present paper, the thermal maturity of organic matter (OM), oil shale industrial quality, coal rank, source of OM and paleoenvironmental conditions associated with OM accumulation in the Yilan Basin are investigated through bulk geochemical analyses, organic maceral analyses and biomarker composition analyses. The coal in the Yilan Basin is classified as subbituminous coal with high total organic carbon (TOC) values, high oil yields, low ash yields, and type II OM. The quality of the low-maturity oil shale in the Coal-Bearing Member is better than that in the Oil Shale Member. The oil shale in the Yilan Basin has type I-II OM and relatively high oil yields, which corresponds to the considerable content of liptinite with a predominantly alginite composition. Based on the higher Pr/Ph values, coal was deposited under oxic–dysoxic conditions, and the OM in the coal mainly originated from terrestrial plants, whereas the oil shale accumulated in a dysoxic environment with lower Pr/Ph values, and featured mixed OM sources, including terrestrial plants and low aquatic organisms. Affected by lake level fluctuations and wide peat swamping, the thickest and highest-quality coal and oil shale developed in swamps under a dysoxic–oxic water column in freshwater environments. Subsequently, the lake basin expanded rapidly, and the sedimentary environment changed to a dysoxic–oxic semideep–deep lake, in which extremely thick mudstone and a large amount of inferior oil shale with low oil yields accumulated under the influence of gravity flows. The basin continued to rapidly subside, the water column became anoxic–dysoxic, and the deposition of mudstone, siltstone and fine sandstone predominated.

CHANGES IN TESTATE AMOEBA ASSEMBLAGES IN A SERIES OF DIFFERENT-TYPE AQUATIC AND TERRESTRIAL HABITATS OF WETLAND AND FOREST ECOSYSTEMS

Patterns of changes in the species richness, abundance, community structure, and biomass of testate amoebae were studied in a series of different-type aquatic and terrestrial habitats along an interlake transect in the Tyumen Region. Altogether, 112 species and forms of testate amoebae, including subspecies, were identified. Micrographs of all species detected are given. The species Conicocassis pontiguasiformis (Beyens et al., 1986) Nasser and Anderson, 2015, previously described as an arctic endemic, was found in the south of Western Siberia for the first time. The species richness of testate amoeba assemblages is maximal in the periphyton. The highest values of species numbers and biomass were detected in the bottom detritus of the coastal part of a swamp lake. Testate amoeba assemblages in various habitats along the transect are divided into aquatic and terrestrial, according to the results of cluster and principal component analyses. The species composition of testate amoeba assemblages depended on substrate wetness, as well as the type of vegetation. The dominants in relative biomass were identified for aquatic, forest, and well-lit Sphagnum habitats.

Spatially calibrating polycyclic aromatic hydrocarbons (PAHs) as proxies of area burned by vegetation fires: Insights from comparisons of historical data and sedimentary PAH fluxes

Many regions worldwide have experienced increasing wildfire activity in recent years and climate changes are predicted to result in more frequent and severe fires. Reconstruction of past fire activity offers paleoenvironmental context for modern and future burning. Pyrogenic polycyclic aromatic hydrocarbons (PAHs) have been increasingly used as a molecular biomarker for fire occurrence in the paleorecord and offer opportunity for nuanced reconstructions of fire characteristics. A suite of PAHs is produced during combustion, and the emission amount and assemblage is influenced by many variables including fuel type, fire temperature, and oxygen availability. Despite recent advances in understanding the controls and taphonomy of these biomass burning markers, the spatial scale of this proxy is unknown. In this paper, measurements of PAH fluxes preserved in a lake sediment archive from the Sierra Nevada, California were compared with a historical geographic information system (GIS) dataset of area burned up to 150 km distance from the lake to determine the spatial scales for which these biomarkers are reliable proxies of biomass burning. The PAH fluxes in the Swamp Lake sediments record a change in the relative anthropogenic and pyrogenic sourcing of PAHs. Anthropogenic pollution sources could explain why some PAHs (fluoranthene (Fl), pyrene (Py), benz[a]anthracene (BaA), retene (Ret), benzo[a]pyrene (BaP), dibenzo[a,h]anthracene (DA) and ideno[1,2,3-cd]pyrene (IP)) did not correlate with area burned within 150 km. This indicates that individual PAHs may have different efficacies in recording area burned and be more susceptible to masking of fire signals by pollution sources. Despite these complications, we find that the PAHs naphthalene (Na), acenaphthene (Ace), fluorene (F), and anthracene (An) are reliable local proxies of area burned (within 40 km), whereas the PAHs phenanthrene (Phe), chrysene (Ch), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), and benzo[g,h,i]perylene (Bghi) are both reliable local (within 36 km) as well as more regional (as much as 75 km for phenanthrene (Phe), chrysene (Ch), and benzo[g,h,i]perylene (Bghi) or 150 km for benzo[b]fluoranthene (BbF) and benzo[k]fluoranthene (BkF)) area burned proxies. Comparisons of PAH fluxes with charcoal accumulation rates in the same sediments suggest that pyrogenic particulate transport modulates low to mid-molecular weight PAHs via adsorption. Overall, the results show that PAH records integrate a combination of spatial signals of area burned and measurement of individual PAHs may enable cross-scale paleofire reconstructions.

The relationship between paleoclimate change and paleosedimentary environment identification in coastal areas

Based on the close relationship between paleoclimate change and paleosedimentary environment, the relationship and influence between paleoclimate change and paleosedimentary environment identification in coastal areas were further studied. Taking the coastal areas of Zhejiang Province as the study area, the soil samples of the coastal areas of Zhejiang Province were collected by BZK1 borehole, and the samples were preliminarily treated and identified by optical microscope. The foraminifera, Ostracoda, and grain size were identified, and the paleosedimentary environment was analyzed by mapping. The results show that the coastal strata in Zhejiang can be divided into four stages according to the changes of sporopollen assemblage, species distribution, abundance, and diversity of foraminifera and Ostracoda. Since the late Pleistocene, the general trend of climate change in the study area is warm-wet, warm-wet and warm-wet, and gradually turns to cold-dry, which is consistent with the change of sea level fluctuation. According to the general trend of paleoclimate change in the study area, the paleosedimentary environment of the study area is further analyzed by the characteristics of grain size parameters and grain size composition. According to the depth, the sediments can be divided into seven stages. Since late Pleistocene, the sediments are mainly silt. The changing process of hydrodynamic conditions during deposition is medium energy-medium low energy-medium energy-medium low energy-medium energy. The changes of sedimentary facies are as follows: shore shallow lake, flood plain, shallow lake beach bar, lake swamp, flood plain, and shallow sea swamp.

Coal-bearing strata sequence stratigraphy of Paleogene Meihe Formation, Meihe Basin, NE China

The Meihe Basin is an important Paleogene coal-bearing basin located in the Dunhua-Mishan Fault Zone, northeastern China. Based on a comprehensive study of well logs, seismic profiles, cores and rock geochemical properties, the coal distribution, paleoenvironment evolution within a sequence stratigraphic framework and the accumulation model to explain how coal seams developed in small fault basin were discussed in detail. Three-third-order sequences were identified in the Paleogene Meihe Formation of Meihe Basin and the two coal-bearing sequences are the Lower Coal-bearing Member of Sequence I and the Upper Coal-bearing Member of Sequence III. All three types of system tracts are developed in both sequences, i.e., the lowstand systems tract (LST), the transgressive systems tract (TST), and the highstand systems tract (HST). In LST of Sequence I, fan delta plain marsh is the main coal accumulating environment where coal seams are thin, discontinuous and therefore uneconomic for mining, and it is the same with all coal seams developed in Sequence III. While in TST and HST of Sequence I, lake swamp is the main sedimentary environment where coal seams are thick, continuous, widely distributed, and thus economically attractive for mining. In the study area, the nice thick economical coal seams are usually developed in an ideal stable depositional environment where organic matter accommodation space grows at a balanced rate with peat, in other words, free of sediment input or channel migration. The key findings of this study could provide guidance for the exploration of coal seams in the Meihe Basin and other similar basins.

Tingkat Korosifitas Air Permukaan Hilir Rawa Pening pada Musim Kemarau dan Penghujan

Corrosion is an important factor that can affect the quality of air used by humans. This has an impact on health and economic factors, damage to air distribution equipment. The level of corrosivity of surface water as raw water for drinking water is important to be examined before the water enters the processing process or other uses such as hydroelectric power (PLTA). This study aims to measure the level of water corrosivity on the surface of the Pening swamp during the dry and rainy seasons in 2018. Taking air samples on the surface of the Pening swamp, then carrying out laboratory tests on the parameters of air corrosivity. The results showed that the downstream surface of the Pening swamp was not corrosive in terms of pH, temperature, TDS, and chloride parameters. The pH value in the dry season (J1) is 7.00, while in the rainy (J2) it is 7.77 and is non-corrosive. The temperature values are 28.6oC and 29.3oC in the rainy and dry seasons, respectively. The TDS measurement results in the dry season are lower than the rainy season by a difference of 12 mg / l. In the dry season it is 141 mg / l and the rainy season is 153 mg / l. This increase probably came from geological material (geological material) such as rocks and soil around the Pening Swamp Lake. Other sources of TDS include urban land, road workers, agricultural land and pasture. Human activities also increase in the increase of TDS in water including domestic activities (bathing and washing), trade, and industry. Chloride levels were 2.19 mg / l and 3.19 mg / l. This research has implications for the users of Sungai Pening Swamp. The corrosivity of air measurement is also by microbiological parameters which need to be investigated further.

Interannual changes in δ15N baseline in a lake–swamp–river food web: effects of summer precipitation in West Siberian forest steppe

Frequency and intensity of precipitation events can alter hydrological conditions of lotic systems and material inflow from the catchment. In this study, interannual changes in food web structure were investigated in a lake–swamp–river system in the semi-arid West Siberian forest-steppe region using carbon and nitrogen stable isotope ratios (δ13C and δ15N). The δ15N signatures of aquatic producers and consumers including zooplankton, benthic invertebrates, and fish sharply increased (up to 7.2‰ in range) in 2009 under high summer precipitation. This would reflect the inflow of 15N-rich nutrients accumulated in the catchment through natural and anthropogenic activities, e.g., sewage, livestock farming, evaporation, and/or microbial denitrification. In 2010, benthic producers including epiphytes and macrophytes were more 13C-enriched, which is likely due to limited supply of dissolved inorganic carbon (DIC) under water stagnation, leading to a large isotopic fractionation during photosynthesis. However, 13C-enrichments in the benthic producers were not reflected to those of aquatic consumers in the habitat. Interannual changes in δ13C of particulate organic matter (POM; a proxy of phytoplankton) were reflected to those of zooplankton, benthic invertebrates, and fish fry, suggesting the trophic importance of autochthonous phytoplankton in the system. These findings suggest that occasional precipitation events in semi-arid forest-steppe regions can modify nutrient flux from the catchment, leading to changes in δ15N baseline in the lotic food web.

Application of stable isotopic analyses for fish host–parasite systems: an evaluation tool for parasite-mediated material flow in aquatic ecosystems

Parasites potentially have important roles in aquatic ecosystems, although relatively little is known about their contributions to the complexity of food web structure. In this study, stable carbon and nitrogen isotope analyses (δ13C and δ15N) were applied for fish host–parasite systems in a shallow swamp–lake ecosystem to assess the validity of stable isotope technics to reveal the parasite-mediated trophic linkages in the food web. Forty host–parasite pairs, including seven parasite taxa (cestodes, trematodes, crustaceans, and hirudinids), found on six host fish species (cyprinids and percids) were examined. The parasites showed unusual δ15N fractionation, with an overall average of − 1.9‰, suggesting the intake of 14N-rich ammonia for amino acid synthesis and/or selective absorption of 15N-depleted amino acids in the host fluid. The isotopic signatures of fish hosts and their parasites were positively correlated, suggesting the absorption and transfer of host-derived nutrients during infection. A δ13C-based isotope mixing model showed that each host fish species exhibited unique dependencies on POM, land-derived organic matter, and macrophytes, suggesting the host-specific trophic niche of the associated parasites in the lake–swamp food web. These emphasized that parasites are potential pathways of material and energy flows in aquatic ecosystems, contributing substantially to the food web complexity. Stable isotope analyses are the useful tools to elucidate the host–parasite trophic linkages, and case-specific isotopic fractionation factors are the mandatory information for a better understanding of the parasite-mediated material flow in ecosystems.

Managing Pymatuning swampland in northwestern Pennsylvania: A personal story

P ymatuning Swamp lies buried beneath Pymatuning Reservoir, subdued but not forgotten, its legacy still visible in the hydric soils and wetlands of the reservoir backwaters (figure 1). This is a story of a changing climate, melting glaciers, ancient lakes filled with sediments, swamplands of northwestern Pennsylvania, and humanity's unceasing efforts to mold and manage the natural landscape for human uses. The footprint of the Adena culture, hunters and gatherers who grew corn ( Zea mays L.), beans, and squash 3,000 to 1,000 years ago near the wetlands, was light. Their settlements thrived for a short period along Pymatuning Creek, the Shenango River, and Conneaut Lake swamp. By the late 1700s, Europeans attempted to settle the wet, forested region incentivized by the Pennsylvania Land Act. The human solution to this wetland wilderness of abundant white pine ( Pinus strobus ), beaver ( Castor canadensis ), and wildlife that was nearly impenetrable to travel was to construct the Beaver to Erie Canal in the 1830s. This extension of the Erie Canal connected the Ohio River via Beaver River north to Shenango River, over the continental divide to Lake Erie and quickened the transport and exchange of the wilderness's raw materials and East Coast's dry goods. The Pymatuning…

Assessing the spatial fidelity of sedimentary charcoal size fractions as fire history proxies with a high-resolution sediment record and historical data

Fire reconstructions provide context for modern rates of burning and inform predictions of fire regimes' responses to climate and/or ecological changes. Charcoal particles preserved in lake sediments are a widely employed fire proxy. Although many studies have calibrated the charcoal proxy, the spatial scales of charcoal dispersal and source area remain disputed. Understanding the spatial fidelity of charcoal accumulation is increasingly important in light of recent efforts to aggregate multiple charcoal records to infer changes in regional, continental- and global-scale fire regimes. Using a high-resolution sediment record from Swamp Lake, California, we compare charcoal accumulation rate (CHAR) variations of three size fractions of sedimentary charcoal (63–150, >150, and >250 μm) to historical area burned data. We find that macroscopic (>250 and >150 μm) and mesoscopic (63–150 μm) charcoal source areas are within 25, 35, and 150 km of Swamp Lake, respectively. We also use a dispersal model to confirm these findings. Our estimates of charcoal source area fall within the large range of estimates for forest fires in the literature. Further, our methodology shows potential for constraining source areas of charcoal in sedimentary records, which is requisite for the reliable inference of the spatial extent of fire in paleorecords.

Preliminary Report on the Late Pleistocene and Holocene Diatoms of Swamp Lake, Yosemite National Park, California, USA

Swamp Lake, Yosemite National Park, is the only known lake in California containing long sequences of varved sediments and thus has the potential to provide a high-resolution record of climate variability. This preliminary analysis of the diatom assemblages from a 947-cm-long composite sediment core (freeze core FZ02–05; 0–67 cm, Livingstone core 02–05; 53–947 cm) shows that the lake has been freshwater, oligotrophic, and circumneutral to alkaline throughout its ~16,000-year-long history. The first sediments deposited in the lake show that the vegetation in the watershed was sparse, allowing organic matter-poor silt and clay to be deposited in the basin. The basin filled quickly to a depth of at least 5 m and remained at least that deep for most of the sediment record. Several short intervals provided evidence of large fluctuations in lake level during the Holocene. The upper 50 cm of the core contains evidence of the Medieval Climate Anomaly and Little Ice Age.

N-Alkane evidence for the onset of wetter conditions in the Sierra Nevada, California (USA) at the mid-late Holocene transition, ~ 3.0 ka

n-Alkane biomarker distributions in sediments from Swamp Lake (SL), in the central Sierra Nevada of California (USA), provide evidence for an increase in mean lake level ~3000yr ago, in conjunction with widespread climatic change inferred from marine and continental records in the eastern North Pacific region. Length distributions of n-alkane chains in modern plants growing at SL were determined and compared to sedimentary distributions in a core spanning the last 13ka. As a group, submerged and floating aquatic plants contained high proportions of short chain lengths (<nC25) compared to emergent, riparian and upland terrestrial species, for which chain lengths >nC27 were dominant. Changes in the sedimentary n-alkane distribution over time were driven by variable inputs from plant sources in response to changing lake level, sedimentation and plant community composition. A shift toward shorter chain lengths (nC21,nC23) occurred between 3.1 and 2.9ka and is best explained by an increase in the abundance of aquatic plants and the availability of shallow-water habitat in response to rising lake level. The late Holocene expansion of SL following a dry mid-Holocene is consistent with previous evidence for increased effective moisture and the onset of wetter conditions in the Sierra Nevada between 4.0 and 3.0ka.

Landform classification using soil data and remote sensing in northern Ordos Plateau of China

Landform classification is commonly done using topographic altitude only. However, practice indicates that locations at a same altitude may have distinctly different landforms, depending on characteristics of soils underneath those locations. The objectives of this study were to: 1) develop a landform classification approach that is based on both altitude and soil characteristic; and 2) use this approach to determine landforms within a watershed located in northern Ordos Plateau of China. Using data collected at 134 out of 200 sampling sites, this study determined that D10 (the diameter of soil particles 10% finer by weight) and long-term average soil moisture acquired in 2010, which can be estimated at reasonable accuracy from remote sensing imagery, can be used to represent soil characteristics of the study watershed. Also, the sampling data revealed that this watershed consists of nine classes of landforms, namely mobile dune (MD), mobile semi-mobile dune (SMD), rolling fixed semi-fixed dune (RFD), flat sandy land (FD), grassy sandy land (GS), bedrock (BR), flat sandy bedrock (FSB), valley agricultural land (VA), and swamp and salt lake (SW). A set of logistic regression equations were derived using data collected at the 134 sampling sites and verified using data at the remaining 66 sites. The verification indicated that these equations have moderate classification accuracy (Kappa coefficients \(\hat K\) > 43%). The results revealed that the dominant classes in the study watershed are FD (36.3%), BR (27.0%), and MD (23.5%), while the other six types of landforms (i.e., SMD, RFD, GS, FSB, VA, and SW) in combination account for 13.2%. Further, the landforms determined in this study were compared with the classes presented by a geologically-based classification map. The comparison indicated that the geologically-based classification could not identify multiple landforms within a class that are dependent upon soil characteristics.

An organic geochemical record of Sierra Nevada climate since the LGM from Swamp Lake, Yosemite

Sediment records from Swamp Lake (SL) in the central Sierra Nevada, California, provide evidence of climatic change on millennial and centennial timescales over the last ∼20,000 years. Total organic carbon (TOC) abundance varied in concert with elemental and isotopic tracers of organic matter (C/N, δ13Corg, δ15N), biogenic silica content, total magnetic susceptibility, and sediment lithology. We interpret the down-core proxy records as representing the response of the lake environment, in terms of temperature, seasonal ice cover, mixing regimes, runoff and in situ OM and nutrient cycling, to shifting climate states. These environmental factors in turn drove changes in algal productivity, OM sources, microbial OM regeneration and secondary production, and detrital input. The late Pleistocene (∼19.7–10.8 cal. kyr BP) was dominated by fluctuations between relatively warm/dry intervals with high TOC (17.4–16.5, 15.8–15.0, 13.9–13.2, 11.4–11.0 cal. kyr BP) and cold/wet intervals (16.5–15.8, 14.8–13.9, 13.1–11.6, 11.0–10.7 cal. kyr BP) characterized by low TOC and high detrital input. The Holocene (∼10.7 cal. kyr BP – present) was characterized by three abrupt increases in TOC (after ∼10.8, 8.0, and 3.0 cal. kyr BP) and numerous century-scale fluctuations. TOC increases reflected enhanced lake productivity and OM recycling, and reduced detrital input, in response to changing winter temperature and hydrologic regimes. Inferred environmental changes at SL correlate with other Sierra Nevada paleorecords, and with reconstructed sea surface temperatures along the California margin. Parallel changes in the SL and SST records over the past ∼20,000 years provide new evidence that continental climate in the Sierra Nevada and the California Current system have responded, on multiple timescales, to common drivers in North Pacific ocean-atmospheric circulation.

Polycyclic aromatic hydrocarbons (PAHs) in lake sediments record historic fire events: Validation using HPLC-fluorescence detection

Understanding the natural mechanisms that control fire occurrence in terrigenous ecosystems requires long and continuous records of past fires. Proxies, such as sedimentary charcoal and tree-ring fire scars, have temporal or spatial limitations and do not directly detect fire intensity. We show in this study that polycyclic aromatic hydrocarbons (PAHs) produced during wildfires record local fire events and fire intensity. We demonstrate that high performance liquid chromatography with fluorescence detector (HPLC-FLD) is superior to gas chromatography–mass spectrometry (GC–MS) for detecting the low concentrations of sedimentary PAHs derived from natural fires. The HPLC-FLD is at least twice as sensitive as the GC–MS in selective ion monitoring (SIM) mode for parent PAHs and five times as sensitive for retene. The annual samples extracted from varved sediments from Swamp Lake in Yosemite National Park, California are compared with the observational fire history record and show that PAH fluxes record fires within 0.5km of the lake. The low molecular weight (LMW) PAHs (e.g., fluoranthene, pyrene and benz[a]anthracene) are the best recorders of fire, whereas the high molecular weight (HMW) PAHs likely record fire intensity. PAHs appear to resolve some of the issues inherent to other fire proxies, such as secondary deposition of charcoal. This study advances our understanding of how PAHs can be used as markers for fire events and poses new questions regarding the distribution of these compounds in the environment.

Drought-induced sulphate release from a wetland in south-central Ontario

Increased sulphate (SO(4)) export from wetlands following summer droughts in central Ontario, Canada has been associated with the delayed chemical recovery of downstream surface waters following decreased sulphur (S) emissions. Prolonged summer droughts result in a decrease or cessation of stream flow, declines in wetland water table level and oxidation of reduced S compounds to SO(4), which is subsequently flushed into drainage streams when stream flow resumes. Sulphate input-output budget calculations (1983-1995 and 1999-2001) at a conifer Sphagnum swamp in the Plastic Lake catchment, indicate that SO(4) is retained in most years but is exported on a net basis following particularly severe summer droughts that result in the cessation of stream flow for more than 54 days (95% CI: 41-72 days). Hindcast calculations using long-term (1916-2000) stream discharge records from a nearby station indicate that while droughts occurred frequently in south-central Ontario over the past 85 years, sufficiently dry conditions to cause net SO(4) export occurred in only 18 of the past 85 years, and indicate a cumulative positive SO(4) balance for the swamp (i.e. net SO(4) retention). Furthermore, the S pool at the Plastic Lake swamp has been estimated to be approximately 1500 kg S/ha in the upper 40 cm peat layer, which is large compared to the amount of net SO(4) export that occurs even in years with particularly dry summers (e.g. -43 kg S/ha in 1987/88). Together, these data suggest that the wetland S pool at Plastic Lake has not been depleted by previous droughts and will continue to sustain episodic drought-related SO(4) export for the foreseeable future.

Seasonal dynamics of zooplankton communities in interconnected tropical swamp lake ecosystems

Seasonal dynamics of zooplankton communities in interconnected tropical swamp lake ecosystems

Diversity and Distribution of Odonata (Dragonflies and Damselflies) in the Fresh Water Swamp Lake Tasek Bera, Malaysia

Fifty-nine species of Odonata were collected in a recent study in the freshwater swamp lake of Tasek Bera, Peninsular Malaysia, in contrast to 33 species that were recorded previously from the Ramsar site. This study added 35 species to the odonate records and together with the museum records, the number of species for the site now stands at 78 from 12 families. The causal factors for the absence of 19 species and other biological aspects such as habitat clustering and temporal activity profile were discussed.

Species inventory and the local uses of the plants and fishes of the Lower Sondu Miriu wetland of Lake Victoria, Kenya

This investigation has surveyed the plants and fishes of the Lower Sondu Miriu wetland and described their use by adjacent communities. Poverty is endemic in the area. Fish samples were caught by beach seines, fence, weir traps, baskets, spears and gill-nets. A schedule (structured/openended) was used to discover the major local uses of wetland plants. A total of 37 species of aquatic plants were identified. The dominants were Cyperus papyrus L. (Papyrus), Eichhornia crassipes Mart. Solms-Laubach (Water hyacinth),Vossia cuspidata Roxb. (Hippo grass) and Phragmites australis (Cav.) Trin. ex. Steud. (Reeds) in a descending order of dominance. The invasion of the wetland by Water hyacinth Eichhornia crassipes, which has lead to sudden disappearance of submerged macrophytes at the swamp–lake interface zone, is reported here for the first time. Twelve families consisting of 28 species of fish were identified, the bulk of which consisted of the indigenous fish species of Lake Victoria. A dependence on the wetland plants for the supply of building material and cooking fuel is highlighted. Traditional use is recommended as opposed to commercial-scale enterprise and industry based on swamp plants, since subsistence utilization is compatible with sustainable utilization.

Late Wisconsin paleoecologic record from Swamp Lake, Yosemite National Park, California

A 7.86-m sediment core from Swamp Lake in Yosemite National Park, California, provides a continuous record of environmental change over the last ca. 16,000 yr, as inferred from pollen, macrofossil, and microscopic charcoal analyses. The core stratigraphy documents late Wisconsin (Tioga stage) deglaciation between >16,000 and 13,700 yr B.P., approximately 6000-3500 yr earlier than higher-elevation Sierra Nevada records. The core includes five volcanic ash layers, chemically identified as four Mono Craters ashes and the Tsoyawata ash (Mt. Mazama, Oregon). The fossil record shows that herbs and sagebrush dominated the glacial environment at Swamp Lake. By 12,000 yr B.P., a mixed conifer forest composed of high- and mid-elevation conifers grew around the lake, suggesting a cool, wet late-glacial environment. The modern Sierra montane forest did not become established until ca. 10,400 yr B.P., when maximum charcoal concentrations and minimum fir pollen percentages indicate an early Holocene xeric period. The record suggests that a cooling trend began ca. 6500 yr B.P. and persisted until ca. 3700 yr B.P. when the modern climatic regime was established.