Water quality of runoff from revegetated mine spoil

Permanent vegetation plots were established on mixed overburden and topsoiled overburden on a lignite test pit in eastern Texas in 1982. Vegetative treatments included two grass-legume treatments [switchgrass (panicum virgattun) — sideoats grama (Bouteloua curtipendula) — subterrancan elover (Trifolitun subterranean) and litte bluestem (Schizachyriun scoparium) — sideoats grama (Bouteloua curtipendula) — Illinois hundleflower (Dessmanthus illinoiensis)] and three monocultures [Coastal bermudagrass (Cynodon dactylon), bahia grass (paspalum notatum) and yellow Indiangrass (Sorghastrum nutans)]. Water was applied to the 0.5m² plots using a sprinklertype rainfall simulator and quality of runoff was determined for each plot. Parameters analyzed included: settleable solids, total filterable solids, sediment production, infiltration rate, nitrites, nitrates, total iron and total manganese. Topsoiling significantly increased inliltration and significantly decreased filterable sediments, sediment production and settleable solids. The hydrologie qualities of the switchgrass-sideoats grama-subterranean elover mixture coincided closely with those of the Coastal bermudagrass monoculture.Authors are presently graduate research assistant and assistant professor. Range Science Department. Texas A&M University. College Station, Texas 77843. Acknowledgement is given to Northwestern Resources Co. for providing the funding for this project.     

Response of Avian Communities to Historic Habitat Change in the Northern Chihuahuan Desert

Abstract: Throughout much of the northern Chihuahuan Desert, the grasslands that were widespread at the time of European settlement have been replaced by desert shrublands. Little is known about the effects of this change on avian communities. We analyzed historic U.S. Government Land Office records to assess large-scale changes in vegetation cover from the 1880s to the present day. We studied vegetation and avian communities in one grassland habitat type and four desert shrubland habitat types to examine (1) how breeding-bird communities may have changed in response to habitat conversion from grassland to desert shrubland and (2) whether breeding-bird communities differ among the four desert shrubland habitat types that compose Chihuahuan Desert scrub in this region. To estimate the characteristics of 1880s black grama (    Bouteloua eriopoda ) grassland, we focused on plots located within extensive patches of present-day black grama and compared the avian communities found there with those in desert shrubland. Species richness was higher in desert shrubland than grassland. Among the desert shrubland habitat types, species richness was consistently highest in mesquite. Avian abundance patterns differed among the four desert shrubland habitat types. At least 30% of the avian community in each habitat pair was distinct. Conversion of grassland to shrubland in south-central New Mexico has likely been accompanied by a major turnover in the avian community. Remaining tracts of black grama provide habitat for species that may be uniquely adapted to the northern Chihuahuan Desert and should be protected.     

Forage production and quality as influenced by amended quartz sand-tailings following phosphate mining

Quartz-sand tailings is a waste product from the Florida phosphate mining industry. Individual tailings disposal areas may occupy 20 to 60 ha and support no vegetation. A split plot field experiment was conducted on a sand tailings deposit to study the effect of various amendments on yield, quality, and mineral concentrations of ‘Callie’ bermudagrass (Cynodon dactylon var.aridus Harlan et de Wet) and ‘Siratro’ [Macroptilium atropurpureum (DC) Urb]. The two species were established on nine treatments: one sand-tailings control (SC); three with air-dried phosphatic clay (PC) at 110, 225, and 340 Mg ha^-1; and three with overburden (OB) at 448, 1,120, and 1,800 Mg ha^-1. All PC and OB treatment rates contained air-dried sewage sludge (SS) at 45 Mg ha^-1 and were all roto-tilled to a 20 to 25 cm depth. There were two additional treatments of OB at 1800 Mg ha^-1 without SS, with and without roto-tilling into sand tailings. Callie established slower (P<0.05) on SC and OB, than on treatments containing SS and/or PC. However, after the root system developed, yields were similar on all sand-tailings treatments. Crude protein andin vitro organic matter digestion for Callie and Siratro did not differ between soil treatments, but Siratro was generally superior to Callie in forage quality. Forage concentrations of P, K, Ca. Mg, Mn, and Zn were adequate in both species for good cattle growth on all treatments. However, Cu tended to be low in Siratro for plant and cattle growth. Once root systems were well established, good yields of quality forage with suitable mineral concentrations were produced on regularly fertilized, quartz-sand tailings.     

No detectable impact of small-scale disturbances on ‘blue carbon’ within seagrass beds

Seagrass meadows are among the most efficient and long-term carbon sinks on earth, but disturbances could threaten this capacity, so understanding the impacts of disturbance on carbon stored within seagrass meadows—‘blue carbon’—is of prime importance. To date, there have been no published studies on the impacts of seagrass loss on ‘blue carbon’ stocks. We experimentally created several kinds of small-scale disturbances, representative of common grazer and boating impacts, within seagrass (Zostera nigracaulis) meadows in Port Phillip Bay (Australia) and measured the impacts on sediment organic carbon stocks (‘C _org’, and other geochemical variables—%N, δ¹³C, δ¹⁵N). Disturbance had no detectable effect on C _org levels within seagrass sediments, even for high-intensity disturbance treatments, which remained bare (i.e. no seagrass recovery) for 2 years after the disturbance. These findings challenge the widely held assumption that disturbance and concomitant loss of seagrass habitat cause release of carbon, at least for small-scale disturbances. We suggest that larger (e.g. meadow scale) disturbances may be required to trigger losses of ‘blue carbon’ from seagrass meadows.     

Species-specific effect of macrobenthic assemblages on meiobenthos and nematode community structure in shallow sandy sediments

Three functionally different macrofaunal species (the filter- and/or surface deposit-feeding polychaete Hediste diversicolor, and the suspension-feeding bivalves Mya arenaria and Cerastoderma glaucum) were introduced as single- and two-species treatments into microcosms containing sandy sediment with a natural meiofaunal community. H. diversicolor is a burrowing species building a system of galleries, C. glaucum lives actively near the sediment surface acting as a biodiffuser and M. arenaria buries deeply and leads a sessile lifestyle. It is shown that H. diversicolor extended the vertical distribution of meiofauna into deeper sediment layers compared to the control and non-Hediste treatments. The response of the nematode community varied significantly among treatments and was dependant on the macrobenthic species composition but not on the species number. Nematode assemblages in all treatments with the polychaete, both in monoculture and with either bivalve, differed significantly from those recorded in other treatments and were more similar than replicates within any other single treatment. H. diversicolor also appeared to have stimulated nematode species diversity. The present study demonstrated that the impact of macrobenthic assemblages on meiofauna is not a simple summation of individual species effects but is species specific.     

Use of polyvinyl chloride pipes (PVC) as potential artificial shelters for amphibians in a coastal plain forest of southeastern Brazil

We studied the use of polyvinil chloride pipes (PVC pipes) by frogs as artificial shelters in a Coastal Plain forest in the Vale Natural Reserve, north of Espírito Santo state, southeastern Brazil from June 2015 to May 2016. We used 14 plots distributed in the Coastal Plain Forest following the RAPELD methodology of sampling. The frogs were sampled in transects along the plots, using the active search method, with visual and auditory sampling. We recorded two species of frogs (Aparasphenodon brunoi and Scinax argyreornatus) using PVC pipes as shelters in the plots in the Forest. Of the 468 PVC pipes established along plots, 38 of them (8.1%) were used as shelter by the frogs. For both frog species, about 33% of microhabitats used in the forest were the interior of PVC pipes. We concluded that the PVC pipes might constitute artificial shelters for at least two of the frog species living in the community of the Coastal Plain Forest, potentially being of relevance in conservation programs. In altered areas and those in which there has been the loss of types of microhabitats, the addition of these PVC pipes as artificial shelters may represent additional and complementary microhabitats to keep or increase the population stocks of arboreal and semi-arboreal frog species and having a size that allow them entering the shelter. These artificial shelters can play an important role in conservation of these frogs in fragmented areas where the availability of the microhabitats of these frog species were locally reduced.     

Influence of sediment nitrogen-availability on carbon and nitrogen dynamics in the seagrass Thalassia testudinum

Variations in tissue carbon (C), nitrogen (N) content, and non-structural carbohydrate (NSC) reserves in the turtle grass Thalassia testudinum Banks ex König were examined in relation to changes in sediment-N availability in Corpus Christi Bay (CCB) and lower Laguna Madre (LLM), Texas, USA, from May to October 1997. Under natural conditions, sediment pore-water NH⁺ ₄-concentrations were higher at CCB (100?μM) than at LLM (30?μM); this difference was reflected in a significantly higher leaf and rhizome N-content at CCB than at LLM. However, sediment NH⁺ ₄-enrichment using a commercial fertilizer resulted in significantly higher tissue N-content relative to controls at both sites. N enrichment also influenced plant carbon metabolism, as reflected by distinct increases in leaf C-content at both sites. Significant decreases in rhizome NSC-content was recorded during the first two months of the experiment, suggesting that C was reallocated from rhizomes to leaves to support stimulated leaf growth at both sites. At LLM, leaf growth-rates increased and leaf turnover-time decreased as a result of sediment NH⁺ ₄-enrichment. With respect to chlorophyll, concentrations did not change significantly at CCB, but increased steadily at LLM after the first month following fertilization. In general however, chlorophyll concentrations in control plots were significantly higher at CCB than that at LLM. These observations suggest that leaf function related to C-fixation is enhanced under higher sediment N conditions, as reflected in higher leaf growth-rates and increased blade chlorophyll-content. In contrast, under low-N conditions, below-ground tissue production is enhanced at the expense of the above-ground shoots and leaves, resulting in the high below: above-ground biomass ratios often observed in seagrass beds of oligotrophic environments.     

Interrelationships between sulfate reducing and methane producing bacteria in coastal sediments with intense sulfide production

Coastal sediments receiving different amounts of organic carbon through sedimentation were investigated with respect to sulfate reduction and methanogenic activity. Sampling was carried out at sediment temperatures of 7° and 15°C. Sulfate-reducing and methanogenic bacteria were found at all depths. Sulfate reduction decreased with depth and the highest sulfide concentrations were found a few centimeters below the sediment surface, up to 15 mM at 15°C and pH 7.1. In the same segments a maximum in the methane concentration was also found, 0.91 mM. The high sulfide concentration inhibited the methane formation from acetate but not from carbon dioxide. In the organic rich sediment sulfate reduction was limited by the diffusion of SO ₄ ⁺ into the sediment and methane production from acetate by sulfide diffusion out of the sediment. When electron acceptor concentration limits sulfate reduction, thermodynamic calculations show that the utilization of electron donors more reduced than acetate is favored. In the sediment with the high carbon-input, acetate predominated at 15°C whereas in the low carbon-input sediment hardly any short chain organic acids were detected. The possibility of a shift in sulfate reduction from acetate oxidation to acetate production is discussed.     

The swimming kinematics of larval Atlantic cod, Gadus morhua L., are resilient to elevated seawater pCO2

Kinematics of swimming behavior of larval Atlantic cod, aged 12 and 27 days post-hatch (dph) and cultured under three pCO₂ conditions (control-370, medium-1800, and high-4200 μatm) from March to May 2010, were extracted from swim path recordings obtained using silhouette video photography. The swim paths were analyzed for swim duration, distance and speed, stop duration, and horizontal and vertical turn angles to determine whether elevated seawater pCO₂—at beyond near-future ocean acidification levels—affects the swimming kinematics of Atlantic cod larvae. There were no significant differences in most of the variables tested: the swimming kinematics of Atlantic cod larvae at 12 and 27 dph were highly resilient to extremely elevated pCO₂ levels. Nonetheless, cod larvae cultured at the highest pCO₂ concentration displayed vertical turn angles that were more restricted (median turn angle, 15°) than larvae in the control (19°) and medium (19°) treatments at 12 dph (but not at 27 dph). Significant reduction in the stop duration of cod larvae from the high treatment (median stop duration, 0.28 s) was also observed compared to the larvae from the control group (0.32 s) at 27 dph (but not at 12 dph). The functional and ecological significance of these subtle differences are unclear and, therefore, require further investigation in order to determine whether they are ecologically relevant or spurious.     

The use of measurable coefficients in process formulations—zooplankton grazing

This paper redefines a construct previously used to model phytoplankton—zooplankton interactions in such a way as to permit the use of measurable quantities as contruct coefficients. The new construct can use unaltered values of the half-saturation constant for zooplankton grazing on total available food (k_s) and the minimum food concentration necessary to stimulate effective feeding (BMIN) reported in the literature. Typical values for these coefficients are 0.1–15 and 0.016–0.19, respectively.     

Particulate matter and metals partitioning in highway rainfall-runoff

This study investigated the particulate matter (PM) and metals in highway dry deposition and rainfall-runoff as a function of hydrologic transport and settling on an event basis. Events were differentiated as mass-limited (ML) and flow-limited (FL). Results indicate that unique and separate suspended sediment concentration (SSC) relationships with turbidity occurred for ML and FL events. Sixty minutes of quiescent settling produced a single SSC-turbidity relationship for all events. ML events transport higher proportions of settleable and sediment PM while FL events transported relatively higher suspended PM. For batch clarification with one hour of settling, ML events had generally higher treatment efficiencies compared to FL events for the same settling conditions. Highway dry deposition PM was hetero-disperse and coarse (d _{50 m} = 304 μm). Results indicate that the acidic rainfall is not a significant contributor to metals in runoff but is capable of leaching metals from dry deposition PM into runoff. Partitioning in retained runoff resulted in a particulate-bound predominance for most metals except Ca and Mg. While the finer fraction of dry deposition PM (< 75 μm) generates the highest metal concentrations, the highest metal mass is associated with the coarser fraction (> 75 μm).     

Effects of organic and inorganic fertilisation on soil nutrient dynamics in a Savannah region (DR Congo)

Very few studies have considered the residual effect of inorganic and organic fertilisation on oxisol chemistry and plant productivity while studying the response of maize to fresh fertiliser application. The purpose of the present study was to examine the effects of five treatments of inorganic and organic fertilisers on maize productivity and soil fertility under field conditions in a Savannah region. The trials were conducted from 2009 to 2011 and the treatments included inorganic nitrogen–phosphorus (NP), Entada abyssinica, Tithonia diversifolia, inorganic NP combined with E. abyssinica, and inorganic NP combined with T. diversifolia, and no fertilised plots. The combination of NP with T. diversifolia or E. abyssinica leaves resulted in the highest increase in grain yields during the first crop season.The positive residual effects of fertilisers on maize grain yield were strong and significant in the immediate succeeding season and decreased during the second year following fertilisation. The highest residual effect was observed in plots fertilised with E. abyssinica combined with NP, followed by T. diversifolia combined with NP, and E. abyssinica and T. diversifolia without NP, respectively. The lowest residual effect was observed in plots fertilised with inorganic NP. Analytical results revealed that total nutrients in the soil matrix are not dominantly in forms available for plant uptake. There were significant residual effects for total potassium in the site with low initial nutrient levels. The soil content of bioavailable phosphorus, nickel, zinc, copper, and cobalt was in general below detectable levels.     

Effects of herbicides on Odonata communities in a rice agroecosystem

The effects of the five herbicides propanil, quinclorac, molinate/propanil, 2,4-D amine, and bensulfuron on Odonata diversity and abundance at the experimental rice plots was investigated. A total of 13 Odonata morphospecies belonging to two families have been identified. Treated plots exhibited higher species richness (up to 12 species) than the control plot (8 species). Ishnura spp. was the most abundant species in the treated plots with a mean density of 194.2 individuals per m², (ind m^?2) followed by Brachythemis contaminata (152 ind m^?2) and Agriocnemis spp. (124 ind m^?2). In the control plots, Agrocnemis spp. was the dominant species (153 ind m^?2) followed by Ishnura spp. (143 ind m^?2) and Neurothemis fluctuans (59 ind m^?2). In the propanil-treated plot, the highest number of odonate species (10 species) was recorded followed by the plots treated with quinclorax and molinate/propanil (9 species). On the 2,4-D amine or bensulfuron-treated plots as well as the control plot, only eight odonate species were recorded. This study revealed that herbicide application had a positive effect on Odonata diversity. This seems reasonable as Odonata are non-target organisms for herbicides. Furthermore, the decomposed weeds resulting from herbicide application would enrich the water with necessary organic matter.     

Simulated green turtle grazing affects nutrient composition of the seagrass <Emphasis Type="Italic">Thalassia testudinum</Emphasis>

Before populations of green turtles (Chelonia mydas) were severely reduced by human overexploitation, the seagrass Thalassia testudinum was intensively grazed by green turtles in the Caribbean. To explore how nutrient composition of T. testudinum pastures responds to intense grazing pressure, we simulated green turtle grazing in 15 plots (each 3 m × 3 m) for 16 months in the central Bahamas. Comparisons of clipped plots with 15 adjacent control (unclipped) plots revealed that simulated grazing resulted in significantly higher energy, nitrogen, phosphorus, lignin, cutin, and condensed tannin content in blades in clipped plots, but sediment organic content was not affected. By continually re-cropping blades in grazing plots, turtles ingest young, actively growing blade tissue with higher energy, nitrogen, and phosphorus concentrations. Our 16-month clipping trial did not generate the expected decline in nutrient content in T. testudinum blades under intensive grazing. However, significant decreases in nitrogen and organic matter reserves in rhizomes, with declines apparent after 16 and 11 months, respectively, indicate that nutrient content of blades and/or blade productivity may decline under continued clipping.     

Geo-accumulation index and contamination factors of heavy metals (Zn and Pb) in urban river sediment

The aim of the present study was to appraise the levels of heavy metal contamination (Zn and Pb) in sediment of the Langat River (Selangor, Malaysia). Samples were collected randomly from 15 sampling stations located along the Langat River. The parameters measured were pH, redox potential, salinity, electrical conductivity, loss of ignition, cation exchanges capacity (Na, Mg, Ca, K), and metal ions (Zn and Pb). The geo-accumulation index (I _geo) and contamination factor (C _f) were applied to determine and classify the magnitude of heavy metal pollution in this urban river sediment. Results revealed that the I _geo of Pb indicated unpolluted to moderately polluted sediment at most of the sampling stations, whereas Zn was considered to be within background concentration. The I _geo results were refined by the C _f values, which showed Pb with very high C _f at 12 stations. Zinc, on the other hand, had low to moderate C _f values. These findings indicated that the sediment of the Langat River is severely polluted with Pb. The Zn concentration at most sampling points was well below most sediment quality guidelines. However, 40% of the sampling points were found to have a Pb concentration higher than the consensus-based probable effect concentration of 128 mg/kg (concentrations above this value are likely to cause harmful effects). This result not only highlights the severity of Pb pollution in the sediment of the Langat River, but also the potential risk it poses to the environment.     

Impact of solids on biphasic biodegradation of phenanthrene in the presence of hydroxypropyl-<Emphasis Type="Italic">β</Emphasis>-cyclodextrin (HPCD)

The consequence of polycyclic aromatic hydrocarbons (PAHs) in the environment is of great concern. The hydrophobic properties of PAHs significantly impact phase distribution causing limited bioavailability. Enhanced biodegradation has been extensively carried out by surfactants and the redeployment effect was recognized. However, the quantitative relationship concerning the impact of solids was rarely reported. A batch of biphasic tests were carried out by introducing Mycobacterium vanbaalenii PYR-1 and hydroxypropyl-β-cyclodextrin (HPCD) into a mixture of phenanthrene solution and various glass beads (GB37-63, GB105-125, and GB350-500). The comparative results demonstrated that HPCD had little effect on microbial growth and was not degradable by bacterium. A model was proposed to describe the biodegradation process. The regression results indicated that the partition coefficient k _d (1.234, 0.726 and 0.448 L·g^?1) and the degradation rate k (0 mmol·L^?1: 0.055, 0.094, and 0.112; 20 mmol·L^?1: 0.126, 0.141, and 0.156; 40 mmol·L^?1: 0.141, 0.156 and 0.184 d^?1) were positively and negatively correlated with the calculated total surface area (TSA) of solids, respectively. Degradation enhanced in the presence of HPCD, and the enhancing factor f was calculated (20 mmol·L^?1: 15.16, 40.01, and 145.5; 40 mmol·L^?1: 13.29, 37.97, and 138.4), indicating that the impact of solids was significant for the enhancement of biodegradation.     

Assessment of the aquatic biodiversity of a threatened coastal lagoon at Bimini, Bahamas

Coastal biodiversity is threatened worldwide by both direct and indirect anthropogenic activities. To more effectively manage and protect coastal biodiversity, accurate assessments of genetic, species, and ecosystem level diversity are required. We present the results from an assessment of the aquatic species diversity of a small (3?km²), shallow, mangrove-fringed Bahamian lagoon (the North Sound) subject to ongoing anthropogenic development. The assessment was conducted through a collation of field observations and data in published literature. We found that eight angiosperm species, 30 macroalgal species, and 370 animal species (including 95 fishes, 69 arthropods, 56 birds, and 45 mollusks) were documented within the lagoon. At least 11 of these species are of conservation concern, such as the critically endangered smalltooth sawfish (Pristis pectinata) and hawksbill turtle (Eretmochelys imbricata). Comparisons of community similarity indicated that the North Sound has a relatively distinct fauna and flora, but available data suggest that the species found there are most similar to those found in nearby habitats in Cuba. The lagoon forms a key nursery habitat for many species, including lemon sharks (Negaprion brevirostris), Caribbean spiny lobsters (Panulirus argus), and queen conch (Strombas gigas). Recently, the lagoon was included as part of a new marine protected area (MPA), but much of the habitat has already experienced considerable anthropogenic disturbance and the MPA boundaries have yet to be established. We have therefore analyzed the lagoon biodiversity and expect the data presented here to serve as a baseline for future comparisons.     

Sediment load and timing of sedimentation affect spore establishment in Macrocystis pyrifera and Undaria pinnatifida

Although the frequency and magnitude of sedimentation often varies across coastal landscapes creating patches with different mean sediment loads, duration of sedimentation and rates of sediment resuspension, few studies have documented the emergent effects of spatio-temporal variability in sedimentation. Here, we conducted two laboratory experiments to evaluate such effects on the establishment of Macrocystis pyrifera and Undaria pinnatifida spores. In the first experiment, spore establishment was significantly affected by sediment load (the effective dose required for a 40 % reduction in establishment ranged between 16 and 60 mg sediment l^?1) and sediment regime (relative sedimentation occurring before spore settlement, ~3 times more sediment was required for 20 % reduction in spore establishment when sedimentation occurred after spore settlement). The second experiment demonstrated that the effects of sediment depended on sediment load (spore establishment was 2–4 times greater when sediment load was 200 mg l^?1 relative to 400 mg l^?1), variability in sedimentation (spore establishment was 1.36 times greater with variable than fixed sediment loads), repeated pulses of sedimentation (pulsed sedimentation decreased spore establishment by 59–91 % relative to a single sedimentation event) and timing of sedimentation relative to spore settlement (sedimentation before spore settlement decreased establishment by 51–95 % relative to sedimentation after spore settlement). These results have important implications for ecologists and resource managers attempting to predict the consequences of sedimentation, suggesting that it is not only important to consider sediment load, but also fine-scale temporal variability in sedimentation relative to key life-history events of the impacted organisms.     

Low-level sedimentation modifies behaviour in juvenile Haliotis iris and may affect their vulnerability to predation

Sedimentation is an important stressor of coastal ecosystems; yet, there is little research into specific mechanisms by which populations are affected by additional sediment loads resulting from anthropogenic-driven processes. This study explored the potential impact of the proposed disposal of over 7 million m³ of dredge spoil on a nearby fishery for the blackfoot abalone Haliotis iris. The range of sediment deposition predicted by models to occur on reefs inhabited by H. iris as a result of the dispersal of sediment from the disposal site was used to design controlled experiments between July and September 2011 to test the likely effects of sedimentation on: (a) behaviour and mortality of juvenile H. iris and (b) photosynthetic vitality of crustose coralline algae (CCA) that form nursery habitats for H. iris obtained from Brinns Point (45, 40.3′S, 170, 39.4′E). We observed no direct effects on the health or mortality of H. iris juveniles or the photosynthetic vitality of habitat forming CCA. H. iris did, however, avoid sediments by moving from predation refugia beneath cobbles to vertical surfaces on cobble edges significantly more often in sediment treatments compared to sediment-free controls. Deposited sediments were also found to inhibit righting response, key behaviour in allowing H. iris to reattach to the substratum following dislodgement. Results of this study suggest that indirect mortality from reductions in available refugia from predation and inability to recover from dislodgement could be significant. These results highlight the importance of understanding indirect impacts of stressors on key ecological processes in order to predict ecological responses.