956 resultados para marine and estuarine mangroves
Resumo:
This thesis describes the stratigraphy, sedimentology and diagenesis of the Pendleside Limestone (Asbian age), a sequence of limestones, shales and dolostones in the Clitheroe area of N. W. England. Field study of 19 measured sections indicates that it was deposited in a rhythmically subsiding basin (Craven Basin) because of movements on the Mid-Craven Fault which was active in Dinantian times. The sequence is up to 190m thick and consists mostly of distal turbidite deposits which have been reworked at horizons when sediment accumulation built up to the wave base. The original depositional fabric and mineralogy of the Pendleside Limestone Group has been extensively modified by diagenetic processes including cementation, authigenesis, dolomitization and silicification. These processes have been studied using a wide variety of laboratory techniques. The carbonate cements of the PendIeside Limestone consist predominantly of ferroan calcite and non-ferroan calcite with microdolomite incIusions. The former is probably a stable replacement of original-high-magnesian calcite. Cementation was accompanied by the formation of authigenic albite and quartz. Much of the upper part of the Pendleside Limestone has been extensively dolomitized and chertified. Several distinct zones of dolomitization are found which increase in thickness and intensity towards the top of the Pendleside Limestone Group. The dolostone horizons correspond to coarser-grained lithologies deposited during periods of shallow water sedimentation. The composition of the dolomites changes from ferroan dolomite in the lower part of the Group to non-ferroan dolomite in the upper part. The low strontium and sodium content of the dolostones in association with the other evidence suggests that the dolomitization was brought about in an open system by the mixing of marine and fresh water in phreatic lens which were established at periodic intervals. The dolomitization was closely associated with chertification although this was initiated by the dissolution of siliceous spicules which provided the necessary source of silica.
Resumo:
The Triassic rocks of Central England consist of three major stratigraphic units: Sherwood Sandstone Group, Mercia Mudstone Group, and Penarth Group. The lower part of the Sherwood Sandstone Group represented by the Kidderminster, Cannock Chase, and Polesworth Formations represents pebbly braided river deposits carried by a major fluvial system flowing to the North-Northwest. The upper part of the Sherwood Sandstone Group includes the Wildmoor and Bromsgrove Sandstone Formations, the deposits of a sandy alluvial system. The Mercia Mudstone Group represents quiet-water deposits of marginal palya type which were subjected to occasional marine flooding. The overlying Penarth Group represent shallow marine and lagoonal environment associated with the Rhaetian marine transgression. The mineralogy of the Triassic sandstones indicates that the main source was from medium to low rank metamorphic rocks with additional supplies from igneous and metamorphic rocks. The study of size-composition trends shows that the climate was semiarid in early Triassic time and became more humid later. The Triassic sandstones show a variety of diagenetic features typical of continental red beds; these include: 1. the dissolution of unstable ferromagnesian silicates, 2. the replacement of detrital grains by clay, 3. the pseudomorphism of biotite by haematite, and 4. the formation of a suite of authigenic minerals including quartz, illite, mixed-layer illite-montmorillonite, kaolinite, k-feldspar, haematite, titanium oxide and later carbonate cement. Palaeomagnetic studies of selected samples show that the magnetization is muticomponent with the various components being carried by different textural phases of haematite.
Resumo:
Mapping and sediment sampling in reefs of the Pulau Seribu group (southwest Java Sea) shows the existence of ten physiographic zones and subzones represented by seven lithofacies. Reefs in the northern part of the archipelago are smaller, more closely spaced and morphologically sim pler than those in the south. This pattern is attributed to differences in subsidence rate. A th reedimensional model is proposed for the evo lution of these reefs but borehole data are requi red to test this model. Miocene limestones are described in detail from hydrocarbon reservoirs in the Batu Raja Formation of the same area. Brief comparisons a re made with surface outcrops of approximately coeval carbonate developments. The lithofacies developed within these limestones reflect variations in hydrodynam ic regime and basement topography . Ele\le.n diagenetic processes affected the Batu Raja limestones and the dist ribution of these is primarily related to sealevel fluctuations. Early diagenesis was marine and characterised by micritisation and preCipitation of fibrous and bladed cements. Dolomitisat ion occurred in the mixed- water zone and its variable intensity is attributed to the configuration of the carbonate body relative to this zone. Subsequently the limestones were subjected to freshwater phreatic zone diagenesis resulting in dissolution and cementation, and a t a late stage underwent burial compaction. Secondary porosity, which \ar9e1.y determines the suitability of these limestones as hydrocarbon reserVOirs, is a function of the variable intensity of dissolution and cementation, burial compaction, dolomitisation and possibly micrite neomorphism. The sedimentary processes that generated the Batu Raja buildups are inferred f rom comparisons with the Pulau Seribu and other Recent analogues. The contrasting pinnacle form of the Pulau Seribu patch reefs compared with the low relief of the Batu Raja buUdups results from differences in the initial substrate topography and subsequent subsidence rate
Resumo:
This study was an evaluation of a Field Project Model Curriculum and its impact on achievement, attitude toward science, attitude toward the environment, self-concept, and academic self-concept with at-risk eleventh and twelfth grade students. One hundred eight students were pretested and posttested on the Piers-Harris Children's Self-Concept Scale, PHCSC (1985); the Self-Concept as a Learner Scale, SCAL (1978); the Marine Science Test, MST (1987); the Science Attitude Inventory, SAI (1970); and the Environmental Attitude Scale, EAS (1972). Using a stratified random design, three groups of students were randomly assigned according to sex and stanine level, to three treatment groups. Group one received the field project method, group two received the field study method, and group three received the field trip method. All three groups followed the marine biology course content as specified by Florida Student Performance Objectives and Frameworks. The intervention occurred for ten months with each group participating in outside-of-classroom activities on a trimonthly basis. Analysis of covariance procedures were used to determine treatment effects. F-ratios, p-levels and t-tests at p $<$.0062 (.05/8) indicated that a significant difference existed among the three treatment groups. Findings indicated that groups one and two were significantly different from group three with group one displaying significantly higher results than group two. There were no significant differences between males and females in performance on the five dependent variables. The tenets underlying environmental education are congruent with the recommendations toward the reform of science education. These include a value analysis approach, inquiry methods, and critical thinking strategies that are applied to environmental issues. ^
Resumo:
Our goal was to quantify the coupled process of litter turnover and leaching as a source of nutrients and fixed carbon in oligotrophic, nutrient-limited wetlands. We conducted poisoned and non-poisoned incubations of leaf material from four different perennial wetland plants (Eleocharis spp., Cladium jamaicense, Rhizophora mangle and Spartina alterniflora) collected from different oligotrophic freshwater and estuarine wetland settings. Total phosphorus (TP) release from the P-limited Everglades plant species (Eleocharis spp., C. jamaicense and R. mangle) was much lower than TP release by the salt marsh plant S. alterniflora from N-limited North Inlet (SC). For most species and sampling times, total organic carbon (TOC) and TP leaching losses were much greater in poisoned than non-poisoned treatments, likely as a result of epiphytic microbial activity. Therefore, a substantial portion of the C and P leached from these wetland plant species was bio-available to microbial communities. Even the microbes associated with S. alterniflora from N-limited North Inlet showed indications of P-limitation early in the leaching process, as P was removed from the water column. Leaves of R. mangle released much more TOC per gram of litter than the other species, likely contributing to the greater waterborne [DOC] observed by others in the mangrove ecotone of Everglades National Park. Between the two freshwater Everglades plants, C. jamaicense leached nearly twice as much P than Eleocharis spp. In scaling this to the landscape level, our observed leaching losses combined with higher litter production of C. jamaicense compared to Eleocharis spp. resulted in a substantially greater P leaching from plant litter to the water column and epiphytic microbes. In conclusion, leaching of fresh plant litter can be an important autochthonous source of nutrients in freshwater and estuarine wetland ecosystems.
Resumo:
The connectivity between the fish community of estuarine mangroves and that of freshwater habitats upstream remains poorly understood. In the Florida Everglades, mangrove-lined creeks link freshwater marshes to estuarine habitats downstream and may act as dry-season refuges for freshwater fishes. We examined seasonal dynamics in the fish community of ecotonal creeks in the southwestern region of Everglades National Park, specifically Rookery Branch and the North and watson rivers. Twelve low-order creeks were sampled via electrofishing, gill nets, and minnow traps during the wet season, transition period, and dry season in 2004-2005. Catches were greater in Rookery Branch than in the North and watson rivers, particularly during the transition period. Community composition varied seasonally in Rookery Branch, and to a greater extent for the larger species, reflecting a pulse of freshwater taxa into creeks as marshes upstream dried periodically. The pulse was short-lived, a later sample showed substantial decreases in freshwater fish numbers. No evidence of a similar influx was seen in the North and watson rivers, which drain shorter hydroperiod marshes and exhibit higher salinities. These results suggest that head-water creeks can serve as important dry-season refugia. Increased freshwater flow resulting from Everglades restoration may enhance this connectivity.
Resumo:
We conducted a series of experiments whereby dissolved organic matter (DOM) was leached from various wetland and estuarine plants, namely sawgrass (Cladium jamaicense), spikerush (Eleocharis cellulosa), red mangrove (Rhizophora mangle), cattail (Typha domingensis), periphyton (dry and wet mat), and a seagrass (turtle grass; Thalassia testudinum). All are abundant in the Florida Coastal Everglades (FCE) except for cattail, but this species has a potential to proliferate in this environment. Senescent plant samples were immersed into ultrapure water with and without addition of 0.1% NaN3 (w/ and w/o NaN3, respectively) for 36 days. We replaced the water every 3 days. The amount of dissolved organic carbon (DOC), sugars, and phenols in the leachates were analyzed. The contribution of plant leachates to the ultrafiltered high molecular weight fraction of DOM (>1 kDa; UDOM) in natural waters in the FCE was also investigated. UDOM in plant leachates was obtained by tangential flow ultrafiltration and its carbon and phenolic compound compositions were analyzed using solid state 13C cross-polarization magic angle spinning nuclear magnetic resonance (13C CPMAS NMR) spectroscopy and thermochemolysis in the presence of tetramethylammonium hydroxide (TMAH thermochemolysis), respectively. The maximum yield of DOC leached from plants over the 36-day incubations ranged from 13.0 to 55.2 g C kg−1 dry weight. This amount was lower in w/o NaN3 treatments (more DOC was consumed by microbes than produced) except for periphyton. During the first 2 weeks of the 5 week incubation period, 60–85% of the total amount of DOC was leached, and exponential decay models fit the leaching rates except for periphyton w/o NaN3. Leached DOC (w/ NaN3) contained different concentrations of sugars and phenols depending on the plant types (1.09–7.22 and 0.38–12.4 g C kg−1 dry weight, respectively), and those biomolecules comprised 8–34% and 4–28% of the total DOC, respectively. This result shows that polyphenols that readily leach from senescent plants can be an important source of chromophoric DOM (CDOM) in wetland environments. The O-alkyl C was found to be the major C form (55±9%) of UDOM in plant leachates as determined by 13C CPMAS NMR. The relative abundance of alkyl C and carbonyl C was consistently lower in plant-leached UDOM than that in natural water UDOM in the FCE, which suggests that these constituents increase in relative abundance during diagenetic processing. TMAH thermochemolysis analysis revealed that the phenolic composition was different among the UDOM leached from different plants, and was expected to serve as a source indicator of UDOM in natural water. Polyphenols are, however, very reactive and photosensitive in aquatic environments, and thus may loose their plant-specific molecular characteristics shortly. Our study suggests that variations in vegetative cover across a wetland landscape will affect the quantity and quality of DOM leached into the water, and such differences in DOM characteristics may affect other biogeochemical processes.
Resumo:
Pulse subsidies account for a substantial proportion of resource availability in many systems, having persistent and cascading effects on consumer population dynamics, and energy flow within and across ecosystem boundaries. Although the importance of pulsed resource subsidies is well-established, the mechanisms that regulate resource fluxes across ecosystem boundaries are not well understood. The aim of our study was to determine the extent that marsh consumers regulated a marsh prey subsidy to estuarine consumers in the oligohaline reaches of an Everglades estuary. We characterized a marsh pulsed subsidy of cyprinodontoid, invertebrate and sunfish prey that move into the upper estuary from adjacent drying marshes. In response to the prey pulse, we examined the numerical, fitness and dietary responses of three focal consumers in the upper estuary; two marsh species (largemouth bass and bowfin) that accompanied the subsidy as a result of marsh drying, and one estuarine consumer (snook). At the onset of marsh drying and the prey subsidy, estuarine consumers switched diets to consume the larger marsh prey (sunfishes), while bass and bowfin maintained similar diets (cyprinodontoids and invertebrates respectively) than pre and post subsidy. From the consumption of this subsidy, bass (marsh species) and snook (estuarine species) exhibited fitness gains while bowfin did not. Although both marsh and estuarine consumers benefitted from the subsidy, we found evidence that freshwater consumers shunted some of the subsidy away from snook. Of the prey sampled in consumer stomachs, 41% of marsh prey biomass was eaten by marsh consumers, while 59% was consumed by the estuarine consumer. We conclude that the amount of the marsh prey available to estuarine consumers may be greater in the absence of marsh consumers, thus the magnitude of the prey subsidy could depend on the dynamics of the marsh consumers from donor communities.
Resumo:
Vegetation patterns of mangroves in the Florida Coastal Everglades (FCE) result from the interaction of environmental gradients and natural disturbances (i.e., hurricanes), creating an array of distinct riverine and scrub mangroves across the landscape. We investigated how landscape patterns of biomass and total net primary productivity (NPPT), including allocation in above- and below-ground mangrove components, vary inter-annually (2001–2004) across gradients in soil properties and hydroperiod in two distinct FCE basins: Shark River Estuary and Taylor River Slough. We propose that the allocation of belowground biomass and productivity (NPPB) relative to aboveground allocation is greater in regions with P limitation and permanent flooding. Porewater sulfide was significantly higher in Taylor River (1.2 ± 0.3 mM) compared to Shark River (0.1 ± 0.03 mM) indicating the lack of a tidal signature and more permanent flooding in this basin. There was a decrease in soil P density and corresponding increase in soil N:P from the mouth (28) to upstream locations (46–105) in Shark River that was consistent with previous results in this region. Taylor River sites showed the highest P limitation (soil N:P > 60). Average NPPT was double in higher P environments (17.0 ± 1.1 Mg ha−1 yr−1) compared to lower P regions (8.3 ± 0.3 Mg ha−1 yr−1). Root biomass to aboveground wood biomass (BGB:AWB) ratio was 17 times higher in P-limited environments demonstrating the allocation strategies of mangroves under resource limitation. Riverine mangroves allocated most of the NPPT to aboveground (69%) while scrub mangroves showed the highest allocation to belowground (58%). The total production to biomass (P:B) ratios were lower in Shark River sites (0.11 yr−1); whereas in Taylor River sites P:B ratios were higher and more variable (0.13–0.24 yr−1). Our results suggest that the interaction of lower P availability in Taylor River relative to Shark River basin, along with higher sulfide and permanent flooding account for higher allocation of belowground biomass and production, at expenses of aboveground growth and wood biomass. These distinct patterns of carbon partitioning between riverine and scrub mangroves in response to environmental stress support our hypothesis that belowground allocation is a significant contribution to soil carbon storage in forested wetlands across FCE, particularly in P-limited scrub mangroves. Elucidating these biomass strategies will improve analysis of carbon budgets (storage and production) in neotropical mangroves and understanding what conditions lead to net carbon sinks in the tropical coastal zone.
Resumo:
We examined interannual variation in soil properties from wetlands occurring in adjacent drainage basins from the southeastern Everglades. Triplicate 10-cm soil cores were collected, homogenized, and analyzed during the wet season 2006–2010 from five freshwater sawgrass wetland marshes and three estuarine mangrove forests. Soil bulk density from the Taylor Slough basin ranged from 0.15 gm-cm−3 to 0.5 gm-cm−3, was higher than from the Panhandle basin every year, and generally increased throughout the study period. Organic matter as a percent loss on ignition ranged from 7 % to 12 % from freshwater marshes and from 13 % to 56 % from estuarine mangroves. Extractable iron in soils was similar among drainage basins and wetland types, typically ranging from 0.6 to 2.0 g Fe kg−1. In contrast, inorganic sulfur was on average over four times higher from estuarine soils relative to freshwater, and was positively correlated with soil organic matter. Finally total soil phosphorus (P) was lower in freshwater soils relative to estuarine soils (84 ± 5 versus 326 ± 32 mg P kg−1). Total P from the freshwater marshes in the Panhandle basin rose throughout the study period from 54.7 ± 8.4 to 107 ± 17 mg P kg−1, a possible outcome of differences in water management between drainage basins.
Resumo:
The Everglades is a sub-tropical coastal wetland characterized among others by its hydrological features and deposits of peat. Formation and preservation of organic matter in soils and sediments in this wetland ecosystem is critical for its sustainability and hydrological processes are important divers in the origin, transport and fate of organic matter. With this in mind, organic matter dynamics in the greater Florida Everglades was studied though various organic geochemistry techniques, especially biomarkers, bulk and compound specific δ13C and δD isotope analysis. The main objectives were focused on how different hydrological regimes in this ecosystem control organic matter dynamics, such as the mobilization of particulate organic matter (POM) in freshwater marshes and estuaries, and how organic geochemistry techniques can be applied to reconstruct Everglades paleo-hydrology. For this purpose organic matter in typical vegetation, floc, surface soils, soil cores, and estuarine suspended particulates were characterized in samples selected along hydrological gradients in the Water Conservation Area 3, Shark River Slough and Taylor Slough. ^ This research focused on three general themes: (1) Assessment of the environmental dynamics and source-specific particulate organic carbon export in a mangrove-dominated estuary. (2) Assessment of the origin, transport and fate of organic matter in freshwater marsh. (3) Assessment of historical changes in hydrological conditions in the Everglades (paleo-hydrology) though biomarkes and compound specific isotope analyses. This study reports the first estimate of particulate organic carbon loss from mangrove ecosystems in the Everglades, provides evidence for particulate organic matter transport with regards to the formation of ridge and slough landscapes in the Everglades, and demonstrates the applicability of the combined biomarker and compound-specific stable isotope approach as a means to generate paleohydrological data in wetlands. The data suggests that: (1) Carbon loss from mangrove estuaries is roughly split 50/50 between dissolved and particulate carbon; (2) hydrological remobilization of particulate organic matter from slough to ridge environments may play an important role in the maintenance of the Everglades freshwater landscape; and (3) Historical changes in hydrology have resulted in significant vegetation shifts from historical slough type vegetation to present ridge type vegetation. ^