Non-impacted Areas Research Articles

An Assessment of Submersion as a Mechanical Control Technique of Pomacea maculata eggs in Southern Florida, USA

Pomacea maculata is a freshwater snail native to various regions of South America. In the 1990's invasive populations of P. maculata began to establish in Texas, Florida, and Georgia. These snails have a high fecundity rate and feed on macrophytes. Water bodies in southern Florida undergo frequent fluctuations in water levels; most are controlled by pumps, culverts, gates and levees. A proposed control method for these snails is the inundation of the egg clutches. This study compared the hatching success of unsubmerged egg clutches with the hatching success of partially submerged egg clutches, the growth rates of snails hatched in the treatments, and determined if snails hatched in submerged conditions are viable to a shell length that exceeds 25 mm, a size typically capable of reproduction. Hatchling success was not significantly different amongst treatments; likewise, growth rates were similar despite inundation. Pomacea maculata egg clutches submerged at various times during their incubation can become detached from the vegetation and sink or float. Floating egg clutches can be transported through water control structures and canals, thus facilitating the spread to non-impacted areas. Manual methods for removal of egg clutches and adults may prove more effective in control efforts.

English

The yeast Candida rugosa, deposited in the Collection of Reference Microorganisms on Health Surveillance from Oswaldo Cruz Foundation under accession number INCQS 71011, was isolated from a sediment sample from Caldeirao Escuridao, a pristine water reservoir in the surroundings of Serra da Capivara National Park, and was identified based on molecular, physiological and morphological characterization. In addition, it was tested regarding its capacity to degrade three textile azo dyes, namely Reactive Red 198, Reactive Red 141, and Reactive Blue 214 at a concentration of 100 mg l-1 during 7 days of incubation. C. rugosa INCQS 71011 was highly efficient towards two azo dyes tested, Reactive Red 198 and Reactive Red 141, demonstrating potential as a biological treatment agent of textile effluent. These results are pioneers for the yeast C. rugosa, since its degradation capacity of textile azo dyes has not yet been described. In addition, this study provides important evidence that fungi from non-impacted areas can efficiently degrade azo dyes.

Monitoring selective logging in western Amazonia with repeat lidar flights

The objective of this study was to test the use of repeat flight, airborne laser scanning data (lidar) for estimating changes associated with low-impact selective logging (approx. 10–15m3ha−1=5–7% of total standing volume harvested) in natural tropical forests in the Western Brazilian Amazon. Specifically, we investigated change in area impacted by selective logging, change in tall canopy (30m+) area, change in lidar canopy structure metrics, and change in above ground biomass (AGB) using a model-based statistical framework. Ground plot measurements were only available from the time of the 2010 lidar acquisition. A simple differencing of the 2010 and 2011 lidar canopy height models identified areas where canopy over 30m tall had been removed. Area of tall canopy dropped from 22.8% in 2010 to 18.7% in 2011, a reduction of 4.1%. Using a relative density model (RDM) technique the increase in area of roads, skidtrails, landings, and felled tree gaps was estimated to be 17.1%.A lidar-based regression model for estimating AGB was developed using lidar metrics from the 2010 lidar acquisition and corresponding AGB ground plot measurements. The estimator was then used to compute AGB estimates for the site in 2010 and 2011 using the 2010 and 2011 lidar acquisition data, respectively. A model-based statistical approach was then used to estimate the uncertainty of the changes in AGB between the acquisitions. Change in RDMs between lidar acquisitions was used to classify each 50m cell in the study area as impacted or non-impacted by logging. The change in mean AGB for the entire study area was −9.1Mgha−1±1.9 (mean±SD) (P-value<0.0001). The change in mean AGB for areas newly impacted in 2011 was −17.9±3.1Mgha−1 (P-value<0.0001) while the change in mean AGB for non-impacted areas was significantly less at −2.6±1.1Mgha−1 (P-value=0.009). These results provide corroborating evidence of the spatial extent and magnitude of change due to low-intensity logging in tropical forests with heavy residual canopy cover.

Effects of Karenia brevis red tide on the spatial distribution of spawning aggregations of sand seatrout Cynoscion arenarius in Tampa Bay, Florida

A passive acoustic survey using a random stratified design detected spawning aggregations of sand seatrout Cynoscion arenarius over 2 sequential spawning seasons (2004 and 2005) in Tampa Bay, Florida. In 2005, an intense Karenia brevis red tide at ichthyotoxic concentra- tions entered Tampa Bay 3 mo after the spawning season began. The bloom persisted through the end of the spawning season and was temporally associated with significant changes in the spatial distribution of spawning aggregations. Red tide was most prevalent and concentrated within the lower portion of Tampa Bay and extended to a lesser degree into the middle bay, but remained absent from the upper bay. While the percentage of sand seatrout aggregations in the middle bay zone did not significantly change from 2004 to 2005, aggregations in the non-impacted area of the upper bay increased, and the red tide-exposed lower bay experienced a significant and pro- nounced decline. These significant bay-wide changes in the sand seatrout spawning population coincided with the red tide event, most notably the considerable decline in the lower bay, but the broad spatial distribution of the aggregations in concert with certain reproductive and life history characteristics may buffer the population from long-term effects. Typically, it is difficult to assess the effect of disturbances on marine fish populations due to complexities in measuring the extent of the perturbation and the magnitude of the loss to the population. Our spatially explicit sampling design further enabled us to demonstrate the widespread effects of red tide on fisheries and pro- vides an important tool for assessing the extent of loss to a spawning fish population.

Microalgae community of the Huaytire wetland, an Andean high-altitude wetland in Peru

AIM: The diversity and distribution of microalgae communities in a high-altitude (3,000 to 4,500 m a.s.l) Andean wetland, regionally known as bofedal, were examined to assess seasonal and spatial patterns. METHODS: Samples were taken monthly from June to December, 2008 at 13 stations in the Huaytire wetland (16° 54’ S and 70° 20’ W), covering three areas (impacted by urban land use, impacted by camelid pasture, and non-impacted) and three climatologically induced periods (ice-covered, ice-melt and ice-free). RESULTS: A total of 52 genera of algae were recorded. Diatoms were the predominant group in abundance and richness. We found a significantly higher abundance during the ice-melting period, when light exposure and runoff were intermediate, in comparison to the ice-covered (low light and flushing) and ice-free (high light and low runoff) periods. Microalgae abundance was significantly lower in the non-impacted area compared to the sites close to the urban area and to the camelid pastures. Alpha diversity ranged from 8 to 29 genera per sample. High genera exchange was observed throughout the wetland, showing a similar floristic composition (beta diversity = 4%). CONCLUSIONS: We found that diatoms were dominant and adapted to the extreme conditions of the Andean wetland, showing higher abundance during the ice-melt period and in the livestock area. Also, taxa richness was higher in the ice-melt period and in the most-impacted areas.

Comparison of zooplankton community structure between impacted and non-impacted areas of Paranaguá Bay Estuarine Complex, south Brazil

We analysed the seasonal distribution of the zooplankton community in an anthropogenically impacted area (Paranaguá Bay) and a non-impacted area (Laranjeiras Bay) of the Paranaguá Bay Estuarine Complex. Large phytoplankton (> 50 μm) and zooplankton were collected every two months, between August 2003 and June 2004. The phytoplankton community was numerically dominated by diatoms (78%) and dinoflagellates (19%). Zooplankton abundance varied between 670 and 100,716 individuals m–3, with a dominance of copepods, mainly the calanoids Acartia lilljeborgii, Acartia tonsa and Pseudodiaptomus acutus. A clear seasonal pattern was observed: copepods were significantly more abundant during the rainy than in the dry season. Significant differences in abundance between the two bays were detected only for cirripede larvae, which were more abundant in Paranaguá Bay. This lack of difference between the two areas was probably a consequence of the water circulation along the estuary, which may have diluted and dispersed the pollutants from Paranaguá Bay to other areas of the estuary.

The impact of sewage on environmental quality and the mesozooplankton community in a highly eutrophic estuary in Argentina

Abstract Dutto, M. S., López Abbate, M. C., Biancalana, F., Berasategui, A. A., and Hoffmeyer, M. S. 2012. The impact of sewage on environmental quality and the mesozooplankton community in a highly eutrophic estuary in Argentina. – ICES Journal of Marine Science, 69: 399–409. Eutrophication caused by human sewage is a growing phenomenon along coasts. Mesozooplankton abundance, community structure, and environmental quality were compared at two sites in the inner Bahía Blanca Estuary (BBE), Argentina, one receiving regional sewage discharge (Canal Vieja), and the other a non-impacted area (Bahía del Medio). Comparisons of mean abundance and multivariate analyses were performed to detect spatial and temporal variations in both environmental and biotic variables. Significantly higher amounts of nitrogen and phosphorus and lower oxygen and pH were recorded at Canal Vieja. Larvae of the detritivorous crab Neohelice granulata were more abundant at Canal Vieja, whereas the common estuarine copepod species Acartia tonsa was more abundant at Bahía del Medio, where the mesozooplankton community was typical for the estuary. Although mesozooplankton is likely to be adapted to the high organic matter content in the BBE, the environmental conditions at Canal Vieja appear to favour Neohelice granulata, and this species should be considered as a potential indicator of the impact of sewage in future monitoring programmes. Particulate organic carbon and chlorophyll a were not influenced by organic loading in this naturally eutrophic estuary.

Influence of fish food and faecal pellets on short-term oxygen uptake, ammonium flux and acid volatile sulphide accumulation in sediments impacted by fish farming and non-impacted sediments

Sediment cores were taken from impacted and non-impacted areas and subjected to different incubations: (i) uninoculated, (ii) inoculated with fish feed and (iii) inoculated with gilthead seabream (Sparus aurata) faeces. After inoculation (or not), the cores were incubated for 8 h and the following biogeochemical fluxes were determined: sediment oxygen uptake (SOU), total ammonia nitrogen flux (TANf) and the production of acid volatile sulphides (AVS-Sp). The results showed that the impacted sediments had a more pronounced benthic metabolism than non-impacted sediments. Correlations between the variables and factorial analysis showed that oxygen consumption caused by the organic enrichment appeared as the trigger for subsequent biogeochemical alterations. The addition of faeces led to proportionally higher benthic rates of SOU, TANf and AVS-Sp than those obtained in the feed incubations. Although the feed is relatively sterile and does not create an oxygen demand until colonized by bacteria, the faeces are already richly colonized with fish gut bacteria and could start to consume oxygen without the lag phase experienced in the incubations with feed. The TANf values measured after the addition of feed or faeces seem to be more related to the leaching velocity of TAN than with the benthic flux, given the short incubation time.

Measurements of gaseous mercury exchanges at the sediment–water, water–atmosphere and sediment–atmosphere interfaces of a tidal environment (Arcachon Bay, France)

The elemental mercury evasion from non-impacted natural areas is of significant importance in the global Hg cycle due to their large spatial coverage. Intertidal areas represent a dynamic environment promoting the transformations of Hg species and their subsequent redistribution. A major challenge remains in providing reliable data on Hg species variability and fluxes under typical transient tidal conditions found in such environment. Field experiments were thus carried out to allow the assessment and comparison of the magnitude of the gaseous Hg fluxes at the three interfaces, sediment-water, sediment-atmosphere and water-atmosphere of a mesotidal temperate lagoon (Arcachon Bay, Aquitaine, France) over three distinct seasonal conditions. The fluxes between the sediment-water and the sediment-atmosphere interfaces were directly evaluated with field flux chambers, respectively static or dynamic. Water-atmosphere fluxes were evaluated from ambient concentrations using a gas exchange model. The fluxes at the sediment-water interface ranged from -5.0 to 5.1 ng m(-2) h(-1) and appeared mainly controlled by diffusion. The occurrence of macrophytic covers (i.e.Zostera noltii sp.) enhanced the fluxes under light radiations. The first direct measurements of sediment-atmosphere fluxes are reported here. The exchanges were more intense and variable than the two other interfaces, ranging between -78 and 40 ng m(-2) h(-1) and were mostly driven by the overlying atmospheric Hg concentrations and superficial sediment temperature. The exchanges between the water column and the atmosphere, computed as a function of wind speed and gaseous mercury saturation ranged from 0.4 to 14.5 ng m(-2) h(-1). The flux intensities recorded over the intertidal sediments periodically exposed to the atmosphere were roughly 2 to 3 times higher than the fluxes of the other interfaces. The evasion of elemental mercury from emerged intertidal sediments is probably a significant pathway for Hg evasion in such tidal environments exhibiting background contamination level.

Historical trends of polychlorinated dibenzo-p-dioxins and dibenzofurans in three dated sediment cores from Mexico

This paper describes the first report of dioxins and furans (PCDDs/Fs) in sediment cores from Mexico. Sedimentation rates and vertical fluxes were estimated using 210Pb dating. Two cores correspond to marine sediments and one to an endorheic lake. Concentrations of PCDDs/Fs found in the three sites are typical of non-impacted areas with low concentrations when compared to reference values. However the PCDDs/Fs sediment profiles show an increasing concentration trend in the upper core sections. This behavior is different from that found at many sites around the globe where diminishing concentrations have been reported. A strong predominance of OCDD was observed, and a comparison to typical composition profiles of industrial and other sources did not result in clear origin assignments for these measured compounds. We suggest that local sources may be responsible for the increase in concentration and, because these undetermined sources have not been curtailed, their importance is still growing.

Rapid Inspection of Lead Aprons and Other Personal Radiation Shielding Using A Fan-Beam Bone Densitometer - Verification of System Ability to Identify Small Shielding Defects

Historical, or ‘legacy’ landfills are commonly unlined and can therefore pose risks to human health and the environment via the discharge of leachate to sensitive groundwater and surface waters. Characterising the impacts on groundwater from legacy landfills located within urban re-development precincts is therefore of growing importance worldwide and is difficult using conventional indicators. At Australia's largest urban re-development precinct, Fishermans Bend, seven known legacy landfills exist, as well as numerous other contamination sources (e.g. historical industrial spillages). Conventional landfill leachate indicators (e.g. ammonia-N and bicarbonate) and perfluoroalkyl acids (PFAA) were measured in 36 bores to distinguish leachate-impacted groundwater from non-impacted areas. Whilst eleven bores showed clear leachate impacts based on conventional indicators, others did not show clearly identifiable leachate signals, particularly those installed near landfills thought to have accepted a larger component of non-putrescible waste (e.g. industrial, construction and/or demolition waste). A new index for detection of legacy landfill leachate impact on groundwater was therefore developed, incorporating perfluorooctanoate (PFOA) as a proportion of PFAA (PFOA/∑PFAA) into an existing method based on leachate to native cation ratios, (‘L/N ratios’). Significant differences between the means of the leachate-impacted versus non-impacted bores were found using the ‘modified L/N ratio’ (p = .006), whereas no significant differences were found between the means of the two groups using the standard L/N ratio (p = .063). The modified L/N ratios also showed a statistically significant difference between the means of the bores impacted by municipal waste versus those impacted by non-putrescible waste (p = .003), indicating they are a much more sensitive indicator of both the existence and type of landfill leachate impact on groundwater than previously reported. This new index may prove particularly useful in complex urban areas where multiple potential contamination sources exist, and land use histories are either unknown or complicated.Conventional methods for leachate detection in groundwater surrounding legacy landfills have been analysed and further developed via the inclusion of perfluoroalkyl acids, to better understand contaminant sources, fate and transport.

English

The Keating Tailings site is located in Broadwater County, Montana on land administered by the Bureau of Land Management. These low pH (4 standard units) wastes resulting from historic gold and copper mining operations contain phytotoxic levels of several metals and are generally devoid of vegetation. With an estimated volume of 110,100 m 3 , these tailings represent unacceptable risk to the environment and human health. The objective of conducting a phytostabilization study at the Keating Tailings Site was to provide BLM managers and decision makers with site specific information and data relating to the implementation, and effectiveness of phytostabilization so that it may be applied to other similar acid metalliferous mine tailings sites administered by the Bureau. To achieve this management objective, replicated experimental plots were implemented using soil amendments, lime and organic matter, designed to ameliorate the plant inhibiting chemical characteristics of the tailings. The plots were seeded with a mix of indigenous native plant species. Vegetation performance of plants grown in the amended or phytostabilized tailings was compared to results for plants seeded into tailings that were not amended, and performance of plants seeded in an adjacent off-site, but non-impacted area. Response variables evaluated in the first growing season, 2004, included emergence and establishment, density, and canopy cover. Concentrations of metals in vegetation were evaluated in terms of plant sufficiency/excess, and in terms of maximum allowable dietary levels for cattle. Changes in soil rootzone pH, conductivity, and soluble metal concentrations before and after treatment were also determined.

Monitoring of immunotoxic responses in oysters reared in areas contaminated by the “Erika” oil spill

Immunological alterations may be used as ecotoxicological biomarkers to detect and monitor biological effects of chemical contaminants in polluted environments. This study reports on a survey of Pacific oysters from the Atlantic coast of Britanny (France) after the “Erika” oil spill. Reared stocks were sampled twice a year from November 2001 to March 2003 at three impacted sites and at an additional site outside the spill area. A multiparametric diagnosis of the immune system was performed on individual hemolymph samples to identify structural, immunopathological alterations and functional impairment of immunocompetent cells. One year after the spill, severe immunological alterations were observed in a site heavily impacted by oil. Since the oysters there had higher contents of PAH compared to the other sites, it was suggested that chronic contamination, possibly generated by oil trapped in the sediments, had induced immunotoxicity. Moreover, moderate variations in some hemolymph parameters observed at the non-impacted area strongly suggested that natural environmental factors may have generated physiological stress. An immunotoxicological index applied here in order to integrate all measurements of defense-related functions appeared to be an efficient tool to identify samples suffering immunological stress.

Benthic microbial indicators of fish farm impact in a coastal area of the Tyrrhenian Sea

We studied the impact of organic loads due to the biodeposition of a fish farm in a non-impacted coastal area of the Tyrrhenian Sea (Western Mediterranean). Sediment chemistry and benthic microbial community were investigated from July 1997 to February 1998 on monthly basis at two stations: one was located under the fish farm, while the second was about 1 km away, and served as a reference site. The presence of the cage induced rapid changes in the benthic conditions: the sediments were rapidly (after 6 weeks) reduced. A significant accumulation of biopolymeric carbon was observed beneath the cage both 2 weeks after the initial cage deployment, on non-impacted sediments, and 5-7 months after, and appeared to be related to the fish farm production cycle. The density of microbial communities beneath the fish farm increased only during the first month of farming activity (July) and partially 7 months after cage disposal (i.e. in January), when there was a significant sediment organic enrichment. Additional evidence of rapid impact of the fish farm on the benthic bacterial communities is provided by the increase in the numbers of autofluorescent microbial cells. The photosynthetic eukaryotic cells displayed a highly reduced contribution to total autofluorescent microbial density, indicating that their decrease is related with biopolymeric carbon accumulation, and probably was due also to “shadow effect” induced by suspended material, coming from the fish farm, on the environment below. We propose here, to apply the ratio of culturable heterotrophic bacteria to microbial direct counts (CFU/MDC) to detect fish farm impact. In cage sediments, organic enrichment and the consequent modification of the characteristics of the benthic environment, determined an increase in aerobic heterotrophicbacteria and vibrio density indicating that they are efficient colonizers of organic-rich sediments. Densities of Escherichia coli and Enterococci were not significantly higher than in the reference site, and are likely of terrestrial origin. Thus they cannot be used as specific indicators of fish farm impact.

Benthic megafauna of the nearshore zone of Martel Inlet (King George Island, South Shetland Islands, Antarctica): depth zonation and underwater observations

The benthic megafauna from the soft bottoms of the shallow coastal zone of Martel Inlet (Admiralty Bay, King George Island, South Shetland Islands, Antarctica) was studied during three austral summers (1989/1990, 1990/1991 and 1994/1995) in relation to the bathymetric features. Surveying and sampling, based on specimen counting and underwater observations, were undertaken by scuba-diving at depths down to 25 m. The depth zonation appears to be influenced by the nature of the substrate and especially by the action of the ice. The multiple action of ice flows prevents the occurrence of sessile forms in the shallower areas, where a low-diversity community, dominated by motile animals, was found. In the area around 18 m in depth, the action of icebergs generated faunistic and sedimentary patches of impacted and non-impacted areas. The more stable conditions prevailing below depths of 20–25 m allowed the establishment of a more diversified epifauna, including many sessile forms. The interannual differences observed in the densities of the mobile isopod Serolis polita may be associated with the summer period when the sampling was undertaken.

Initial Fish-Farm Impact on Meiofaunal Assemblages in Coastal Sediments of the Western Mediterranean

We studied the initial impact of organic loads due to the biodeposition of a new fish farm in a non-impacted coastal area of the Tyrrhenian Sea (Western Mediterranean). Sediment chemistry and meiofaunal assemblages were investigated from July 1997 to February 1998 on a monthly basis at two stations: the first was located under the fish farm, while the second was at about 1 km distance, and served as control. Variations in the biochemical composition of the sedimentary organic matter and meiofaunal community structure were also related to changes in reared fish biomass. The presence of the cage-induced rapid changes in the benthic compartment: the sediments reached rapidly (i.e., after only 6 weeks) reducing conditions. A significant accumulation of biopolymeric carbon was observed beneath the cage both at the beginning of this study and 5–7 months after cage disposal and appeared to be related to the fish-farm production cycle. Sedimentary proteins and lipids resulted to be good descriptors of medium-term fish-farm impact. Changes in the sediment conditions beneath the cage determined a significant reduction of the total meiofaunal density (on average for 70%). Most meiofaunal taxa, including nematodes, copepods and ostracods displayed a significant decrease in the farm sediments within 3 months after cage installation. Kinorhynchs appeared extremely sensitive to reducing conditions of the sediments and disappeared almost completely, whereas polychaete densities remained unvaried. After initial impact meiofaunal assemblages responded to organic enrichment recovering, at least partially, their apparent structural characteristics. These data indicate that studies carried out several months after cage deployment might underestimate the actual impact on benthic assemblages.

Methylmercury in fish as a tool for understanding the Amazon mercury contamination

In order to evaluate aquatic environmental mercury (Hg) and methylmercury (MeHg) contamination, a wide variety of fish species were sampled from some tributaries of the Brazilian Amazon river system, the Balbina reservoir and the Pantanal watersheds. These water bodies present different mercury inputs and biogeochemical characteristics. Amazon fish, which are the main pathway of MeHg to the local population, are the most important protein source for them, and fishing is a significant economic activity throughout these regions. MeHg in fish samples (164) were analysed with an efficient extraction technique and measured by GC–ECD. Analytical quality was checked through intercomparisons between two laboratories with local samples and a certified standard from IAEA. MeHg concentrations of carnivorous, omnivorous, detritivorous and herbivorous species ranged from 0.1 to 1.25 mg kg−1 wet wt and the mean percentages of MeHg to total mercury were usually higher than 80%. Carnivorous (piscivorous) fish, which represented 74% of all samples, effectively showed higher MeHg concentrations as well as a higher MeHg/total mercury ratio in muscle tissue than fish from lower trophic levels. In general, MeHg concentrations in carnivorous fish were higher in places close to goldmining activities, the Madeira river and the Tapajós river near Itaituba city. The MeHg/total mercury ratios in fish were higher in non-impacted areas and with smaller amounts of suspended particulate materials (Negro river, Balbina reservoir and Pantanal watershed). No MeHg seasonal variability was observed in Serrasalmus rhombeus (carnivorous fish) from the Madeira river basin during the year. High variability in MeHg levels was observed in muscle of the same carnivorous species fish with similar weights sampled at the same place and by similar nets. Copyright © 1999 John Wiley & Sons, Ltd.

Actual and potential heterotrophicneutrogen fixation and detrification rates of oryza glumaepatula Steud in an amazonian lake

Estimates of the rates of heterotrophic nitrogen fixation (HNF) and denitrification by acetylene reduction and acetylene inhibition, respectively, were determined for the roots and culms of wild rice, Oryza glumaepatula, in Lake Batata, a lake severely impacted by the dumping of bauxite tailings into the lake basin. Two stations were established in different parts of the lake: one in a natural area and other in an impacted area of the lake. Plant assays were performed during the principle hydroperiods of dry (December) and flood (July) to determine both: a) Actual rates of HNF and denitrification, and b) potential rates of HNF after amending with glucose potential rates of denitrification after amending with glucose, glucose + nitrate, or nitrate alone. HNF was found to naturally exceed denitrification in this system. HNF and denitrification were consistently found to be greater for roots than culms but no correlation was found between rates of HNF or denitrification and water depth. It was determined that for HNF and denitrification that glucose and nitrate were the limiting factors in controlling those processes in roots and culms of O. glumaepatula . HNF and denitrification of O. glumaepatula does not appear to show differences between impacted and non-impacted areas.

Effects of bauxite tailing on PAR attenuation in an Amazonian crystalline water lake

The PAR attenuation in Batata Lake, an Amazonian crystalline system subject to the effect of bauxite mining, was increased through dumping of tailing by 35% during low periods in impacted areas. Subsequently, the euphotic zone was reduced by 1 meter and phytoplankton production decreased by 60%. The tailing, which are frequently resuspended and transported into non-impacted areas by currents, and remain in suspension as small particles (>50% of frequency distribution), thereby increasing inorganic turbidity (>25 NTU) and PAR scattering. However, during the high water hydrological phase, there was no distinct difference in PAR attenuation between the impacted and non-impacted areas.

Fate of phosphorus in Florida Spodosols contaminated with cattle manure

Phosphorus loading from dairies and beef ranches in the Lake Okeechobee watershed and the subsequent movement of the P into the drainage waters is a major factor influencing the eutrophication of Lake Okeechobee. The soils of this area are mainly Spodosols with the watertable lying between surface and spodic horizons for extended periods each year. In this study, the quantity of total P (TP) within the soil profile (A, E, Bh and Bw horizons) of dairies and beef ranches in the Lake Okeechobee basin was determined to evaluate the magnitude of P loading in these soils. The effect of cattle density was evident in TP concentrations throughout the soil profile. In the A horizon, mean TP concentrations were 1680, 165, and 34 kg P ha −1 for high, low, and nonimpacted areas, respectively. The same trend, although at lower concentrations, was evident in the E, Bh, and Bw horizons. The quantity of P considered to be potentially mobile under leaching conditions (water-soluble P, Mehlich I extractable or NH 4Cl extractable), also followed similar trends as the TP concentrations. Based on chemical fractionation data, nearly 80% of TP in the A horizon of the highly impacted soils may be considered leachable. We calculated hat about 4000 kg P ha −1 would be available for leaching in the soil profile of the high intensity areas immediately adjacent to the dairy barns. This “labile P” appears to be solubilized slowly over a long period of time (likely several years). There seems to be no natural mechanism whereby the P is stabilized through the formation of minerals, and even if such processes do take place, a vast amount of P still remains in a form in which it is readily transported along with the drainage water. The A and E horizons had poor P retention capacities while the retention capacity of the Bh horizon varied with the soil type, Myakka ≥ Immokalee > Pomello. Due to the Low P-retention capacity in the upper horizons of these soils, there is potential for significant subsurface lateral P transport.