Effect of concentration and hydraulic reaction time on the removal of pharmaceutical compounds in a membrane bioreactor inoculated with activated sludge

Pharmaceuticals are often not fully removed in wastewater treatment plants (WWTPs) and are thus being detected at trace levels in water bodies all over the world posing a risk to numerous organisms. These organic micropollutants (OMPs) reach WWTPs at concentrations sometimes too low to serve as growth substrate for microorganisms; thus, co-metabolism is thought to be the main conversion mechanism. In this study, the microbial removal of six pharmaceuticals was investigated in a membrane bioreactor at increasing concentrations (4–800 nM) of the compounds and using three different hydraulic retention times (HRT; 1, 3.5 and 5 days). The bioreactor was inoculated with activated sludge from a municipal WWTP and fed with ammonium, acetate and methanol as main growth substrates to mimic co-metabolism. Each pharmaceutical had a different average removal efficiency: acetaminophen (100%) > fluoxetine (50%) > metoprolol (25%) > diclofenac (20%) > metformin (15%) > carbamazepine (10%). Higher pharmaceutical influent concentrations proportionally increased the removal rate of each compound, but surprisingly not the removal percentage. Furthermore, only metformin removal improved to 80–100% when HRT or biomass concentration was increased. Microbial community changes were followed with 16S rRNA gene amplicon sequencing in response to the increment of pharmaceutical concentration: Nitrospirae and Planctomycetes 16S rRNA relative gene abundance decreased, whereas Acidobacteria and Bacteroidetes increased. Remarkably, the Dokdonella genus, previously implicated in acetaminophen metabolism, showed a 30-fold increase in abundance at the highest concentration of pharmaceuticals applied. Taken together, these results suggest that the incomplete removal of most pharmaceutical compounds in WWTPs is dependent on neither concentration nor reaction time. Accordingly, we propose a chemical equilibrium or a growth substrate limitation as the responsible mechanisms of the incomplete removal. Finally, Dokdonella could be the main acetaminophen degrader under activated sludge conditions, and non-antibiotic pharmaceuticals might still be toxic to relevant WWTP bacteria.     

Effects of an organic sediment on performance of young Phragmites australis clones at different water depth treatments

Performance of young Phragmites australis plants was examined after 7 weeks on an artificial nutrient-enriched inorganic substrate and on the same substrate to which an organic sediment from a eutrophic lake was added, at three different water depth treatments. Growth decreased, and proportional allocation of biomass to roots increased, with the addition of sediment. These differences were significant in shallow and deep water, but not at a medium depth. Concentrations of phosphorus and nitrogen in plant biomass decreased, and concentration of iron increased, with addition of sediment.The effects of sediment addition may have resulted from a decreased availability of nutrients in the substrate or from an impaired root functioning. Nutrient exhaustion in the substrate, due to a fast plant growth, can explain the relatively strong effects in shallow water. Deep water, on the other hand, probably restricted oxygen transport to the roots, resulting in an impaired root functioning in the low-redox sediment environment. The results show that, especially in relatively deep water, growth of undisturbed plants of P. australis may be inhibited by eutrophication of sediments, probably because of an impaired root functioning in sediments containing reduced toxic compounds (e.g. ferrous iron).     

Removal of pharmaceutical compounds in tropical constructed wetlands

The ability of tropical horizontal subsurface constructed wetlands (HSSF CWs) planted with Typha angustifolia to remove four widely used pharmaceutical compounds (carbamazepine, declofenac, ibuprofen and naproxen) at the relatively short hydraulic residence time of 2-4 days was documented. For both ibuprofen and naproxen, pharmaceutical compounds with low D_ow values, the planted beds showed significant (p < 0.05) enhancement of removal efficiencies (80% and 91%, respectively, at the 4 day HRT), compared to unplanted beds (60% and 52%, respectively). The presence of plants resulted in the removal of these pharmaceutical compounds from artificial wastewater. The more oxidizing environment in the rhizosphere might have played an important role, but other rhizosphere effects, beside rhizosphere aeration, appeared to be important also. Carbamazepine, considered one of the most recalcitrant pharmaceuticals, and declofenac showed low removal efficiencies in our CW, and this is attributable to their higher hydrophobicity. The fact that the removal of these compounds could be explained by the sorption onto the available organic surfaces, explains why there was no significant difference (p > 0.05) in their removal efficiencies between planted as compared to unplanted beds. No statistical significant differences (p > 0.05) were observed for the removal efficiencies of any of the pharmaceuticals tested for the 2-day HRT as compared to that corresponding to 4-day HRT. The rather efficient removal shown by the wetlands in this study (with HRTs of 2-4 days), indicates that such a CW system may be more practically used (with less land requirements) in tropical regions for removing conventional pollutants and certain pharmaceutical compounds from wastewater effluents.     

Removal of diclofenac and sulfamethoxazole from synthetic municipal waste water in microcosm downflow constructed wetlands: Start-up results

The objectives of this study were to investigate the start-up removal of pharmaceutical compounds diclofenac and sulfamethoxazole in microcosm downflow constructed wetlands and their effect on the performance of the studied constructed wetlands, and also to assess the effect of plants on the removal of these compounds. The experimental system that was used in this 86-day experiment consisted of 24 columns filled up to 70 cm with predominantly sandy material. Four types of columns were used (six replicates) depending on the presence of plants (Phalaris arundinacea L. var. picta L.) and the presence of pharmaceutical compounds in the influent. The influent was synthetic municipal waste water to which a mixture of 5 mg/L of diclofenac and 5 mg/L of sulfamethoxazole was added. The observed removal of diclofenac was moderate (approx. 50%) and the removal of sulfamethoxazole was relatively low (24–30%). It was found that the removal of diclofenac and sulfamethoxazole was not affected by the vegetation. The presence of diclofenac and sulfamethoxazole in the influent had significant effect on the effluent concentration of N-NO₃ and the water loss in the columns, which in both cases were lower than in the control columns. The scope for further research was discussed.     

Aquaculture of Posidonia australis Seedlings for Seagrass Restoration Programs: Effect of Sediment Type and Organic Enrichment on Growth

Seeds of the seagrass Posidonia australis are desiccation sensitive and as there is no seed dormancy seeds cannot be stored for use in restoration projects. To realize the restoration potential of seed‐based restoration of Posidonia, this study investigated preconditioning seedlings of Posidonia in aquaculture facilities before transplanting to extend the restoration window from a few weeks (for fresh seed) to months or even years (for preconditioned seedlings). Here, we tested two levels of organic matter addition, 0 and 1.5% sediment dry weight and three sediment types; two heterogeneous sediments typical of low‐energy marine environments (1) unsorted calcareous and (2) unsorted silica, and a homogeneous sediment typical of high‐energy marine habitats (3) well‐sorted silica. We then evaluated seedling survival, biomass and development over a period of 7 months in tank culture. There was 100% survival over the 7‐month experimental period for seedlings. Seedling leaf, root, rhizome, and total biomass increased when organic matter was added to unsorted calcareous and unsorted silica sediment but not well‐sorted silica sediment, although this increase was significant only after 7 months of growth. The characteristics of the sediment also influenced seedling root length and architecture. Root length and number of lateral root branches were greatest in unsorted sediments and when organic matter was present. This study demonstrates that tank culture of P. australis enabled seedlings to be available for restoration purposes for at least 7 months, and with modification of the sediment composition, larger P. australis seedlings with more substantial root systems can be produced.     

The Fate of 15N-Nitrate in Healthy and Declining Phragmites australis Stands

Abstract The dissimilatory nitrate-reducing processes, denitrification, and dissimilatory nitrate-reduction to ammonium were studied in freshwater lake sediments within healthy and degrading Phragmites australis (reed) stands. The samples from the healthy vegetation site contained roots and rhizomes. Cores were supplied with 1.9–5.2 μg ¹⁵N-NO₃ ⁻ g⁻¹ dry sediment in the laboratory and subsequently incubated for 8 h at 20°C, in the dark. The ¹⁵N compounds were determined before (natural percentage of ¹⁵N) and after 1 and 8 h of incubation. The uptake of ¹⁵N by the roots and rhizomes in the healthy vegetation was 61%. Nitrogen losses, interpreted as denitrification, accounted for 25 and 84% of the added ¹⁵N-NO₃ ⁻ in sediment from the healthy and degrading vegetation sites, respectively. The percentages of nitrate reduced to ammonium were 4 and 9% in sediment from the healthy vegetation and degrading vegetation sites, respectively. The percentage of ¹⁵N–total N in the sediment of the healthy vegetation site was 10%, whereas for the degrading vegetation site this percentage was 7%. The percentage of nitrate reduced to ammonium could be potentially underestimated by the percentage of ¹⁵N measured in the sediment. In this case, in healthy and degenerating P. australis stands, the percentage of produced ammonium accounted for 14–16%. The nitrate reduction rates were calculated based on an incubation period of one hour. The denitrification rate in sediment from the degrading vegetation site was higher than from the healthy vegetation site. The rate of dissimilatory nitrate reduction to ammonium was almost tenfold higher in sediment from the degrading vegetation site compared to sediment from the healthy vegetation site. The significantly lower percentages of dissimilatory nitrate reduction to ammonium and denitrification in the healthy stand compared to the degrading stand was probably due to the presence of roots and rhizomes. In the sediments of healthy and degrading P. australis stands, denitrification was the main nitrate-reducing process. Received: 24 July 1996; Accepted: 5 December 1996     

Inorganic Nutrient Supplements Constrain Restoration Potential of Seedlings of the Seagrass,Posidonia australis

Seed represents a potentially ecologically sustainable source of planting units for restoring seagrasses, particularly for seagrasses where transplanting negatively impacts donor beds. However, newly germinated seeds may be nutrient limited as their underdeveloped root systems may constrain capacity to access sediment‐based resources. We conducted a study in land‐based aquaculture tanks to determine whether early growth of newly germinated Posidonia australis seedlings could be enhanced by adding inorganic nutrients to the sediment. Sediments were supplemented with nitrogen and phosphorus in a factorial design (no nutrients, N, P, N + P). Shoot survival, whole shoot biomass, root morphology, root architecture, and nutrient concentration of seedlings were assessed monthly for the first 4 months after germination. More than 90% of seedlings survived during the 4 months of the experiment, irrespective of nutrient treatment. Growth of P. australis seedlings was not enhanced by addition of N or P to the sediment despite nutrient uptake occurring. Seedling growth was found to be more dependent on seed nutrient reserves rather than external nutrient sources for at least the first 4 months after germination. Adding inorganic nutrients to the sediment also significantly reduced the development of the seedling root system in terms of biomass, length, and density of lateral root branches. This study demonstrated that inorganic nutrient supplements constrain root development and therefore capacity for successful anchorage of seagrass seedlings, and pose a significant limitation on seedling establishment when transferred to the field, as well as potentially limiting natural and transplanted seedling establishment in eutrophic sediments.     

The ecology of Vibrio vulnificus, Vibrio cholerae, and Vibrio parahaemolyticus in North Carolina Estuaries

While numerous studies have characterized the distribution and/or ecology of various pathogenic Vibrio spp., here we have simultaneously examined several estuarine sites for Vibrio vulnificus, V. cholerae, and V. parahaemolyticus. For a one year period, waters and sediment were monitored for the presence of these three pathogens at six different sites on the east coast of North Carolina in the United States. All three pathogens, identified using colony hybridization and PCR methods, occurred in these estuarine environments, although V. cholerae occurred only infrequently and at very low levels. Seventeen chemical, physical, and biological parameters were investigated, including salinity, water temperature, turbidity, dissolved oxygen, levels of various inorganic nutrients and dissolved organic carbon, as well as total vibrios, total coliforms, and E. coli. We found each of the Vibrio spp. in water and sediment to correlate to several of these environmental measurements, with water temperature and total Vibrio levels correlating highly (P<0.0001) with occurrence of the three pathogens. Thus, these two parameters may represent simple assays for characterizing the potential public health hazard of estuarine waters.     

Effects of organic nutrients and growth factors on biostimulation of tributyltin removal by sediment microorganisms and Enterobacter cloacae

Natural attenuation can reduce contamination of tributyltin (TBT), but persistence of the xenobiotic can cause long-term issues in the environment. Biostimulation is used to accelerate biodegradation. This study investigated the ability of individual organic nutrients and growth factors to enhance TBT biodegradation by sediment microorganisms (SED) and Enterobacter cloacae strain TISTR1971 (B3). The supplements that produced high biomass yield were selected for degradation enhancement. For TBT degradation at initial concentration of 0.1 mg/l, negative or limited degradation was observed in some selected supplements indicating that increasing the biomass did not necessarily promote degradation. Consequently, the addition of nutrients was expected to increase both dioxygenase activity and the degrader population. At different concentrations of supplements, a mixture of succinate/glycerol showed the highest removal for SED which reduced TBT by 77%, 75%, and 68% for 0.1×, 1×, and 10× supplement concentration, respectively. For B3, the addition of succinate showed degradation of 49% (0.1×), 75% (1×), and 77% (10×). Most nutrients and amino acids had an inhibitory effect at 1× or 10× levels. Excess amount of the nutrients added can inhibit the initial degradation of TBT. Therefore, TBT biostimulation requires supplements that increase the capability of TBT degraders at an appropriate amount.     

Influence of nitrogen species (NH4 + and NO3 −) on the dynamics of P in water–sediment–Salvinia herzogii systems

Water – Salvinia herzogii – sediment systems were exposed to different phosphorus and nitrogen combinations in outdoor experiments. The aim was to estimate the amounts of P immobilized in macrophytes and sediments, as well as to elucidate whether or not the presence of N affects the retention of P. The following components were added: o-P, o-P + NH₄ ⁺, o-P + NO₃ ^– + NH₄ ⁺, o-P + NO₃ ^–. The concentration of nutrients was periodically determined throughout the experiment (28 days). The concentrations of P and N in plant tissues and sediments were determined at the beginning and the end of the experiment. Sequential extractions of P-fractions in sediment were performed using the EDTA method (Golterman, 1996). The removal efficiency of P in water was 95–99%. The removal of NH₄ ⁺ (97–98%) was more effective than that of NO₃ ^– (44–86%). The presence of nitrogen species increased the removal velocity of o-P from water, NH₄ ⁺ was the most effective species. Sediments not only had higher P removal rates than macrophytes but, in the control treatment without macrophytes, they reached the values obtained by macrophytes plus sediments in the other treatments. The adsorption of P takes place at the surface layer of the sediment (1 cm). Most of the P incorporated into the sediment during the experiment was sorbed by the fraction Fe(OOH)P. The addition of nutrients to water modified the leaves/lacinias weight ratio.     

Biodegradation of 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid by dichlorophenol-adapted microorganisms from freshwater,anaerobic sediments

Reductive dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) was investigated in anaerobic sediments by non-adapted microorganisms and by microorganisms adapted to either 2,4- or 3,4-dichlorophenol (DCP). The rate of dechlorination of 2,4-D was increased by adaptation of sediment microorganisms to 2,4-DCP while dechlorination by sediment microorganisms adapted to 3,4-DCP displayed a lag phase similar to non-adapted sediment slurries. Both 2,4- and 3,4-DCP-adapted microorganisms produced 4-chlorophenoxyacetic acid by ortho-chlorine removal. Lag phases prior to dechlorination of the initial addition of 2,4,5-T by DCP-adapted sediment microorganisms were comparable to those from non-adapted sediment slurries. However, the rates of dechlorination increased upon subsequent additions of 2,4,5-T. Biodegradation of 2,4,5-T by sediment microorganisms adapted to 2,4- and/ or 3,4-DCP produced 2,5-D as the initial intermediate followed by 3-chlorophenol and phenol indicating a para > ortho > meta order of dechlorination. Dechlorination of 2,4,5-T, by either adapted or non-adapted sediment microorganisms, progressed without detection of 2,4,5-trichlorophenol as an intermediate.     

Marine genetic swamping: hybrids replace an obligately estuarine fish

Populations of obligately estuarine taxa are potentially small and isolated and may lack genetic variation and display regional differentiation as a result of drift and inbreeding. Hybridization with a wide‐ranging marine congener should introduce genetic variation and reduce the effects of inbreeding depression and genetic drift. However, high levels of hybridization can cause demographic and genetic swamping. In southeastern Australia hybridization occurs between obligately estuarine Black bream (Acanthopagrus butcheri) and migratory marine Yellowfin bream (Acanthopagrus australis). Here, we surveyed genetic variation at eight microsatellite loci and the mitochondrial control region of juvenile fish from five coastal lagoons (including temporal replication in two lagoons) (total n = 970) to determine the frequency and persistence of hybridization, and its likely consequence for the estuarine restricted A. butcheri. Of 688 juvenile fish genotyped 95% were either A. australis (347) or hybrids (309); only 5% (32) were A. butcheri. Most hybrids were later generation hybrids or A. butcheri backcrosses, which are likely multi‐generational residents within lagoons. Far greater proportions of hybrid juveniles were found within two lagoons that are generally closed to the ocean (>90% hybrid fish within generally closed lagoons vs. 12–27% in permanently or intermittently open lagoons). In both lagoons, this was consistent across multiple cohorts of fish [79–97% hybrid fish (n = 282)]. Hybridization and introgression represent a major threat to the persistence of A. butcheri and have yet to be investigated for large numbers of estuarine taxa.     

In vitro activity of Bacillus firmus against the burrowing nematode Radopholus similis,the root-knot nematode Meloidogyne incognita and the stem nematode Ditylenchus dipsaci

Antagonistic bacteria have been repeatedly shown to be promising microorganisms for the biological control of sedentary and migratory endoparasitic nematodes. Depending on the bacteria involved, the mechanisms of action include: obligate parasitism, reduction in penetration, growth inhibition due to competition for nutrients and antibiosis associated with bioactive metabolites. In the present studies, the mode of action of the antagonist bacteria Bacillus firmus, isolated from a bionematicide, was evaluated. Significant rates of paralysis and mortality were detected after incubation of three nematode species in low concentrations of the pure culture filtrates following removal of the bacterial cells. The same culture filtrates also significantly reduced hatching of Meloidogyne incognita. Pure bacterial cell suspensions added to sand also reduced survival of R. similis in bioassays by 41% over the controls. The mode-of-action responsible for nematode paralysis and mortality was therefore demonstrated to be closely associated with the production of bioactive compounds secondary metabolites by the bacteria.     

A Novel Dual-Compartment,Continuous-Flow Wetland Microcosm to Assess Cis-Dichloroethene Removal from the Rhizosphere

The anaerobic biodegradation of tetrachloroethene commonly results in the accumulation of chlorinated intermediates such as cis-1,2-dichloroethene (cDCE). Frequently, groundwater contaminated with chlorinated ethenes discharges to natural wetlands. The goal of this study was to quantitatively evaluate the effects of wetland plants and microorganisms on the fate of cDCE in the wetland rhizosphere. To accomplish this goal, a novel dual-compartment wetland microcosm was designed. A Phragmites australis individual was maintained in the microcosm, which was operated with continuous flows of air and mineral medium through the foliar and rhizosphere compartments, respectively, to incorporate mass transfer/transport processes that are important in natural wetlands and allow steady-state assessment of changes in dissolved O₂ and cDCE or [1,2–¹⁴C]cDCE levels. Substantial amounts of [¹⁴C]cDCE were phytovolatilized through a healthy P. australis individual to the foliar chamber. Rhizodegradation by native microorganisms associated with P. australis roots also converted substantial amounts of [¹⁴C]cDCE to ¹⁴C-labeled CO₂ and non-volatile compounds, presumably through cometabolic reactions that could be enhanced by the release of O₂ and exudates by P. australis. These results suggest that, in some cases, the intrinsic capacity of native wetland plants and microorganisms to remove cDCE from the rhizosphere may be substantial.     

Impact of winter reed harvesting and burning on the nutrient economy of reed beds

The fringing reeds (Phragmites australis (Cav.) Trin. ex Steud., Poaceae) at Lake Constance-Untersee were mown or burnt in winter thereby drastically reducing the addition of decomposable organic matter to the sediment. The purpose of this study was to test whether or not this management significantly decreased the contents of organic matter and nutrients in the surface sediment layer and if the oxygen conditions in the withinreed water body improved. Hypotheses were tested by monitoring 6 treated reed beds and 3 reference fields over a period of up to 4 years. The sediment/water system of reed beds was found to be well buffered against the removal of the current year's crop of dead Phragmites straw, because only slight, and mostly insignificant, differences between treated and untreated reeds were detected. Hence, the benefit of winter reed harvesting to reduce nutrient overloading of the reed-belts and the die-back of reeds remains dubious.     

Plant Growth–Promoting Bacteria Facilitate the Growth of the Common Reed Phragmites australisin the Presence of Copper or Polycyclic Aromatic Hydrocarbons

To test whether plant growth–promoting bacteria might be useful in facilitating the growth of Phragmites australis, the common reed, in the presence of metals and organic compounds, P. australis seeds were treated with plant growth–promoting bacteria. The bacterium Pseudomonas asplenii AC was genetically transformed to express a bacterial gene encoding the enzyme 1-aminocyclopropane-1-carboxylate deaminase, and both the native and transformed bacteria were tested in conjunction with P. australis. Inoculation of seeds, which were subsequently grown in the presence of copper or creosote, with transformed P. asplenii AC significantly increased seed germination. Moreover, the addition of either native or transformed P. asplenii AC to P. australis seeds enabled the plants (shoots and roots) to attain a greater size than noninoculated plants after growth in soil in the presence of either copper or creosote.     

The relative importance of sediment and water column supplies of nutrients to the growth and tissue nutrient content of the green macroalga Enteromorpha intestinalis along an estuarine resource gradient

Large blooms of opportunistic green macroalgae such as Enteromorpha intestinalis are of ecological concern in estuaries worldwide. Macroalgae derive their nutrients from the water column but estuarine sediments may also be an important nutrient source. We hypothesized that the importance of these nutrient sources to E. intestinalis varies along a nutrient-resource gradient within an estuary. We tested this in experimental units constructed with water and sediments collected from 3 sites in Upper Newport Bay estuary, California, US, that varied greatly in water column nutrient concentrations. For each site there were three treatments: sediments + water; sediments + water + Enteromorpha intestinalis (algae); inert sand + water + algae. Water in units was exchanged weekly simulating low turnover characteristic of poorly flushed estuaries. The importance of the water column versus sediments as a source of nutrients to E. intestinalis varied with the magnitude of the different sources. When initial water column levels of dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (SRP) were low, estuarine sediments increased E. intestinalis growth and tissue nutrient content. In experimental units from sites where initial water column DIN was high, there was no effect of estuarine sediments on E. intestinalis growth or tissue N content. Salinity, however, was low in these units and may have inhibited growth. E. intestinalis growth and tissue P content were highest in units from the site with highest initial sediment nutrient content. Water column DIN was depleted each week of the experiment. Thus, the water column was a primary source of nutrients to the algae when water column nutrient supply was high, and the sediments supplemented nutrient supply to the algae when water column nutrient sources were low. Depletion of water column DIN in sediment + water units indicated that the sediments may have acted as a nutrient sink in the absence of macroalgae. Our data provide direct experimental evidence that macroalgae utilize and ecologically benefit from nutrients stored in estuarine sediments.     

不同生态型芦苇种群对盐胁迫的生长和光合特性

土壤盐渍化是影响我国土壤利用效率的主要因素之一,芦苇是改良土壤盐渍化的良好实验材料,但芦苇有着多种的生态型,比较各生态型芦苇的耐盐差异成为亟待解决的问题。通过设置淡水(0.00%)与加盐(质量浓度2.00%)处理控制实验,测量芦苇的生长指标和光合指标,比较河口型芦苇与内陆型芦苇耐盐性,寻找合适生态型的芦苇作为改良土壤盐渍化的生物材料。在实验中,与淡水条件相比,加盐(2.00%)处理条件下,河口型芦苇和内陆型芦苇的株高(height)、蒸腾速率(E)均显著性下降,但是两种生态型的芦苇的水分利用效率(WUE)明显提高;河口型的芦苇相对生长速率(RGR)和气孔导度(Gs)都明显高于内陆型芦苇。在淡水环境中,河口型芦苇的相对生长速率(RGR)和净光合速率(A)都显著性地高于内陆型芦苇。结果表明两种生态型的芦苇在进化过程中存在一定程度上的分化,盐胁迫会抑制两种芦苇的生长,两种生态型芦苇的相对生长速率和气孔导度在盐胁迫下出现明显地差异,表明两种生态型的芦苇对盐度的响应机制有所差异。相比于内陆型芦苇,河口型芦苇有着更强的耐盐性,内陆型及河口型芦苇的表型性状差异主要是由于其原生境的差异所决定的。     

Contrasting responses of seagrass transplants (Posidonia australis) to nitrogen, phosphorus and iron addition in an estuary and a coastal embayment

Addition of nutrients to sediments has been proposed as a means of enhancing transplantation success in seagrasses. The effects of nutrient and iron additions to natural sediments on the growth and morphology of Posidonia australis transplants were evaluated in underwater plots in two contrasting environments: a coastal embayment (Princess Royal Harbour) with sandy sediments and little riverine input, and an estuary (Oyster Harbour) with organic-rich sediments and subject to seasonal river flow from a large rural catchment. Sixty six planting units spaced 1 m apart were transplanted in situ in each location. Nitrogen (N) and phosphorus (P) were added in a randomized factorial design using slow release fertilizer granules at the start of the experiment and repeated every 4-5 months for 2 years. In a concurrent experiment, chelated iron Fe EDTA was added to modify the sediment sulphur cycle.In Oyster Harbour, the addition of N significantly increased leaf N concentrations but reduced total biomass and biomass of leaves. Addition of P significantly increased leaf P concentrations and number of living leaves per transplant, leaf area, leaf length, length of longest rhizome axis and total rhizome length. Combined N + P addition resulted in a significant increase in leaf P concentrations and leaf area per plant only. In Princess Royal Harbour, addition of N produced significant increases in leaf variables (total and leaf biomass, number of shoots and living leaves, leaf area, and leaf length) but there were no significant differences observed in below ground plant parts (rhizomes). Addition of P had no significant effects on any growth measurements. Addition of N + P combined increased number of living leaves and leaf area significantly. δ¹⁵N in mature leaf tissue were significantly more negative for N and N + P treatments at both locations.Our results indicated that N limitation was occurring in the coastal embayment, Princess Royal Harbour whereas in the more estuarine Oyster Harbour, P was limiting plant growth. Addition of FeEDTA produced equivocal results at both sites and we suggest these results are confounded by the addition of N and C in the EDTA. We caution the use of nutrient addition to transplants of slow growing seagrasses such as P. australis without a thorough understanding of the nutrient status of the system, estuarine or coastal embayment, in which they are to be transplanted.     

Gamete compatibility between marine and estuarine Acanthopagrus spp. (Sparidae) and their hybrids

On Australia's south‐east coast, hybridization between estuary‐restricted black bream Acanthopagrus butcheri Munro and its migratory coastal congener yellowfin bream Acanthopagrus australis (Günther) has led to estuarine populations largely composed of hybrids that are most genetically similar to A. butcheri. The fertilization success achieved when ova of estuary‐caught A. butcheri were fertilized with the cryogenically preserved sperm of either ocean‐caught A. australis or estuary‐caught A. butcheri‐like was compared. The experimental crosses, which by chance included both pure parental and hybrid bream, revealed no evidence that gametic incompatibility provides a barrier to fertilization among both pure species and their hybrids.