Comparison of macrofauna communities in sediments of the beds of vertical flow constructed wetlands planted with Panicum maximum (Jacq.) treating domestic wastewater

To improve our understanding of the ecological functioning of constructed wetlands, the macrofauna structure in the sediments of a constructed wetland planted with Panicum maximum treating domestic wastewater was studied. Two beds were planted with young P. maximum and two unplanted beds were used as controls. After 150 days of wastewater treatment on the beds, macrofauna was collected by taking five cores of sediment samples at the corners and the centre of each bed following three layers in the vertical profile. Globally, the planted beds removed COD, NH₄⁺, and PO₄^3? more (p < 0.05) than the control. Eleven taxa belonging to 6 classes and 11 orders were recorded. Macrofauna was significantly more diversified (Mann–Whitney test: p < 0.05) in terms of Shannon index of diversity in the planted beds (0.25–0.44 bits/ind.) than in the control (0.08–0.23 bits/ind.). But macrofauna settlement presents a relative homogeneity between the beds (index Jaccard = 0.63). Its abundance was three times higher in the planted bed than in the control. From the surface to the bottom of the beds, macrofauna diversity and abundance decreased and were heavily dominated by Annelida. The significant relationships were only observed between Insecta and Myriapoda in the control.     

Lethal effects of ichthyotoxic raphidophytes,Chattonella marina,C. antiqua,and Heterosigma akashiwo,on post-embryonic stages of the Japanese pearl oyster,Pinctada fucata martensii

The inimical effects of the ichthyotoxic harmful algal bloom (HAB)-forming raphidophytes Heterosigma akashiwo, Chattonella marina, and Chattonella antiqua on the early-life stages of the Japanese pearl oyster Pinctada fucata martensii were studied. Fertilized eggs and developing embryos were not affected following exposure to the harmful raphidophytes; however, all three algal species severely affected trochophores and D-larvae, early-stage D-larvae, and late-stage pre-settling larvae. Exposure to C. marina (5 × 10² cells ml⁻¹), C. antiqua (10³ cells ml⁻¹), and H. akashiwo (5 × 10³ cells ml⁻¹) resulted in decreased success of metamorphosis to the trochophore stage. A complete inhibition of trochophore metamorphosis was observed following exposure to C. antiqua at 5 × 10³ cells ml⁻¹ and C. marina at 8 × 10³ cells ml⁻¹. In all experiments, more than 80% of newly formed trochophores were anomalous, and in the case of exposure to H. akashiwo at 10⁵ cells ml⁻¹ more than 70% of D-larvae were anomalous. The activity rates of D-larvae (1-day-old) were significantly reduced following exposure to C. antiqua (8 × 10³ cells ml⁻¹, 24 h), C. marina (8 × 10³ cells ml⁻¹, 24 h), and H. akashiwo (10⁴ cells ml⁻¹, 24 h). The activity rates of pre-settling larvae (21-day-old) were also significantly reduced following exposure to C. antiqua (10³ cells ml⁻¹, 24 h), C. marina (8 × 10³ cells ml⁻¹, 24 h), and H. akashiwo (5 × 10⁴ cells ml⁻¹, 24 h). Significant mortalities of both larval stages were induced by all three raphidophytes, with higher mortality rates registered for pre-settling larvae than D-larvae, especially following exposure to C. marina (5 × 10²–8 × 10³ cells ml⁻¹, 48–86 h) and C. antiqua (10³–8 × 10³ cells ml⁻¹, 72–86 h). Contact between raphidophyte cells and newly metamorphosed trochophores and D-larvae, 1-day-old D-larvae, and 21-day-old larvae resulted in microscopic changes in the raphidophytes, and then, in the motile early-life stages of pearl oysters. Upon contact and physical disturbance of their cells by larval cilia, H. akashiwo, C. marina and C. antiqua became immotile and shed their glycocalyx. The trochophores and larvae were observed trapped in a conglomerate of glycocalyx and mucus, most probably a mixture of larval mucous and raphidophyte tricosyts and mucocytes. All motile stages of pearl oyster larvae showed a typical escape behavior translating into increased swimming in an effort to release themselves from the sticky mucous traps. The larvae subsequently became exhausted, entrapped in more heavy mucous, lost their larval cilia, sank, become immotile, and died. Although other toxic mediators could have been involved, the results of the present study indicate that all three raphidophytes were harmful only for motile stages of pearl oysters, and that the physical disturbance of their cells upon contact with the ciliary structures of pearl oyster larvae initiated the harmful mechanism. The present study is the first report of lethal effects of harmful Chattonella spp. towards larvae of a bivalve mollusc. Blooms of H. akashiwo, C. antiqua and C. marina occur in all major cultivation areas of P. fucata martensii during the developmental period of their larvae. Therefore, exposure of the motile early-life stages of Japanese pearl oysters could adversely affect their population recruitment. In addition, the present study shows that further research with early-life development of pearl oysters and other bivalves could contribute to improving the understanding of the controversial harmful mechanisms of raphidophytes in marine organisms.     

Can acclimation of thermal tolerance,in adults and across generations,act as a buffer against climate change in tropical marine ectotherms?

Thermal acclimation capacity was investigated in adults of three tropical marine invertebrates, the subtidal barnacle Striatobalanus amaryllis, the intertidal gastropod Volegalea cochlidium and the intertidal barnacle Amphibalanus amphitrite. To test the relative importance of transgenerational acclimation, the developmental acclimation capacity of A. amphitrite was investigated in F₁ and F₂ generations reared at a subset of the same incubation temperatures. The increase in CT_max (measured through loss of key behavioural metrics) of F₀ adults across the incubation temperature range 25.4–33.4 °C was low: 0.00 °C (V. cochlidium), 0.05 °C (S. amaryllis) and 0.06 °C (A. amphitrite) per 1 °C increase in incubation temperature (the acclimation response ratio; ARR). Although the effect of generation was not significant, across the incubation temperature range of 29.4–33.4 °C, the increase in CT_max in the F₁ (0.30 °C) and F₂ (0.15 °C) generations of A. amphitrite was greater than in the F₀ (0.10 °C). These correspond to ARR's of 0.03 °C (F₀), 0.08 °C (F₁) and 0.04 °C (F₂), respectively. The variability in CT_max between individuals in each treatment was maintained across generations, despite the high mortality of progeny. Further research is required to investigate the potential for transgenerational acclimation to provide an extra buffer for tropical marine species facing climate warming.     

Spatial and temporal changes in epibenthic communities at deep,hard bottom aquaculture sites in Newfoundland

This study explores spatio-temporal changes in epibenthic communities due to salmon aquaculture at deep (>30 m), hard-bottom dominated sites in Newfoundland (Canada). Using a drop-camera approach, we followed changes with production at two aquaculture sites, as well as potential recovery processes at two fallow sites, comparing their epibenthic composition with nearby non-production sites. Multivariate analysis revealed that aquaculture production led to rapid changes in epibenthic communities, as evidenced primarily by the presence of two visual indicators: bacterial mats and opportunistic polychaetes. Due to low taxon richness and abundances, as well as variability among sites, no clear intermediate successional stages were apparent. Beggiatoa-like mats and opportunistic polychaetes appeared rapidly once aquaculture production began; these indicators did not increase in spatial extent during the survey and were typically observed up to 100 m, and occasionally up to 160 m from cages. After 15 months of fallowing, Beggiatoa-like mats and opportunistic polychaetes remained present at sites and were occasionally accompanied by few other taxa, suggesting incomplete recovery.     

Ecological re-engineering of a freshwater impoundment for salt marsh restoration in a hypertidal system

The purpose of this paper was to examine the vegetative, sedimentary, nekton and hydrologic response to ecological re-engineering of a freshwater impoundment in the Upper Bay of Fundy. The dyke was breached in five locations and one channel initiated to connect the river to the borrow pit behind the dyke. This triggered significant self-organization within the restoration site. Existing channels (e.g. borrow pit) were incorporated within the newly excavated and developing creek system, increasing the hydraulic connectivity within the marsh and increasing fish habitat. Vegetation colonization, primarily by Spartina alterniflora, was rapid with almost 100% coverage by the end of the third year. Species associated with high marsh communities such as Juncus gerardii, Scirpus robustus, Ranunculus cymbalaria and Puccinellia maritima were present in increasing abundance post-restoration at the restoration site. The constructed channel eroded downward 2.3 m and the head of the channel retreated 35 m in response to the increased tidal prism. In the year immediately following the breach (2006), the surface of the marsh was unconsolidated and rates of change in surface elevation measured at RSET stations ranged from ?0.7 (±0.1) to 1.7 (±0.2) cm yr^?1 (±1SE). Measurements between years are highly variable. By year 3 the rate of surface elevation change decreased to a more moderate but variable mean of 0.3 (±0.6) cm yr^?1 with the marker horizons recording mean accretion rates of 0.7 cm yr^?1. This implies subsurface consolidation as the sediments dewatered or organic matter decomposed and vegetation became more established. Fish density decreased after restoration, however, remained higher than at the reference site for most years.     

Effects of plant diversity on biomass production and substrate nitrogen in a subsurface vertical flow constructed wetland

Most biodiversity experiments have been conducted in grassland ecosystems with nitrogen limitation, while little research has been conducted on relationships between plant biomass production, substrate nitrogen retention and plant diversity in wetlands with continuous nitrogen supply. We conducted a plant diversity experiment in a subsurface vertical flow constructed wetland for treating domestic wastewater in southeastern China. Plant aboveground biomass production ranged from 20 to 3121 g m^?2 yr^?1 across all plant communities. In general, plant biomass production was positively correlated with species richness (P = 0.001) and functional group richness (P = 0.001). Substrate nitrate concentration increased significantly with increasing plant species richness (P = 0.046), but not with functional group richness (P = 0.550). Furthermore, legumes did not affect biomass production (P = 0.255), retention of substrate nitrate (P = 0.280) and ammonium (P = 0.269). Compared to the most productive of the corresponding monocultures, transgressive overyielding of mixed plant communities did not occur in most polycultures. Because greater diversity of plant community led to higher biomass production and substrate nitrogen retention, thus we recommend that plant biodiversity should be incorporated in constructed wetlands to improve wastewater treatment efficiency.     

Spatial and temporal variability in macroalgal blooms in a eutrophied coastal estuary

All three macroalgal clades (Chlorophyta, Rhodophyta, and Phaeophyceae) contain bloom-forming species. Macroalgal blooms occur worldwide and have negative consequences for coastal habitats and economies. Narragansett Bay (NB), Rhode Island, USA, is a medium sized estuary that is heavily influenced by anthropogenic activities and has been plagued by macroalgal blooms for over a century. Over the past decade, significant investment has upgraded wastewater treatment from secondary treatment to water-quality based limits (i.e. tertiary treatment) in an effort to control coastal eutrophication in this system. The goal of this study was to improve the understanding of multi-year macroalgal bloom dynamics through intensive aerial and ground surveys conducted monthly to bi-monthly during low tides in May–October 2006–2013 in NB. Aerial surveys provided a rapid characterization of macroalgal densities across a large area, while ground surveys provided high resolution measurements of macroalgal identity, percent cover, and biomass.Macroalgal blooms in NB are dominated by Ulva and Gracilaria spp. regardless of year or month, although all three clades of macroalgae were documented. Chlorophyta cover and nutrient concentrations were highest in the middle and upper bay. Rhodophyta cover was highest in the middle and lower bay, while drifting Phaeophyceae cover was patchy. Macroalgal blooms of >1000 g fresh mass (gfm)/m² (max = 3510 gfm/m²) in the intertidal zone and >3000 gfm/m³ (max = 8555 gfm/m³) in the subtidal zone were observed within a heavily impacted embayment (Greenwich Bay). Macroalgal percent cover (intertidal), biomass (subtidal), and diversity varied significantly between year, month-group, site, and even within sites, with the highest species diversity at sites outside of Greenwich Bay. Total intertidal macroalgal percent cover, as well as subtidal Ulva biomass, were positively correlated with temperature. Dissolved inorganic nitrogen concentrations were correlated with the total biomass of macroalgae and the subtidal biomass of Gracilaria spp. but not the biomass of Ulva spp. Despite seasonal reductions in the nutrient output of wastewater treatment facilities emptying into upper Narragansett Bay in recent years, macroalgal blooms still persist. Continued long-term monitoring of water quality, macroalgal blooms, and ecological indicators is essential to understand the changes in macroalgal bloom dynamics that occur after nutrient reductions from management efforts.     

Leaf growth and population dynamics of intertidal Zostera japonica on the western coast of Korea

Leaf production and population dynamics of Zostera japonica were examined at three elevations of an intertidal transect in Seungbongdo Island on the western coast of Korea. Morphometrics, shoot density, biomass, leaf production, reproductive effort and environmental factors were monitored from October 2001 to October 2002. Z. japonica grew well in the lower intertidal zone from 0.2 to 1.0 m above mean chart datum. The upper station (St. 1) exhibited a finer sediment grain size and richer organic content than the middle (St. 2) and lower stations (St. 3). The size of shoots and leaves was significantly greater at St. 1 than at St. 3, whereas the rhizome internodes were longer at St. 3. Despite differences in morphological characteristics among three stations, seagrass biomass and shoot density were not significantly different among study sites. Shoot density, biomass, morphometrics and leaf productivity exhibited clear seasonal variations, which varied along with seasonal changes of water and air temperature. Leaf productivity measured by the clip and reharvest method was highest in September (4.3 g DW m⁻² d⁻¹) and lowest in February (0.2 g DW m⁻² d⁻¹). Reproductive shoots rapidly increased to maximum density along with the high water temperature in July to September. In the intertidal zone, Z. japonica exhibited faster vegetative growth on muddy sand than on sand, probably due to the difference in nutrient supply. The seasonal changes of water and air temperature were considered to play an important role in the seasonal leaf growth of Z. japonica.     

Effects of plant diversity on microbial biomass and community metabolic profiles in a full-scale constructed wetland

There has been less understanding of relations of microbial community patterns with plant diversity in constructed wetlands. We conducted a single full-scale subsurface vertical flow constructed wetland (SVFCW, 1000 m²) study focusing on domestic wastewater processing. This study measured the size and structure of microbial community using fumigation extraction and BIOLOG Ecoplate? techniques, to examine the effects of macrophyte diversity on microbial communities that are critical in treatment efficiency of constructed wetlands. We also determined the relationship of plant diversity (species richness) with its biomass production under disturbance of the same wastewater supply. Linear regression analysis showed that plant biomass production strongly correlated with plant species richness (R = 0.407, P < 0.001). Increase in plant species richness increased microbial biomass carbon and nitrogen (R = 0.494, P < 0.001; R = 0.465, P < 0.001) and utilization of amino acids on Ecoplates (R = 0.235, P = 0.03), but limited the utilization of amine/amides (R = ?0.338, P = 0.013). Principal components analysis (PCA) showed that the diversity and community-level physiological profiles (CLPP) of microbial community at 168 h of incubation strongly depended on the presence or absence of plant species in the SVFCW system, but not on the species richness. This is the first step toward understanding relations of plant diversity with soil microbial community patterns in constructed wetlands, but the effect of species diversity on microbial community should be further studied.     

Characterisation of the bacteria associated with barnacle,Balanus amphitrite,shell and their role in gregarious settlement of cypris larvae

The acorn barnacle Balanus amphitrite (syn. Amphibalanus amphitrite) is a model organism to investigate pelago-benthic transitions in marine invertebrates. A driver for larval settlement in this organism is the need to attach close to conspecifics, to allow reproduction to take place. Adult barnacles are covered by microbial biofilms and the contribution of these biofilms to conspecific recognition is not fully understood. Little information is available on microbial communities associated with B. amphitrite. We compared biofilm communities from the barnacle shell surface with those from the surrounding rocks using the culture-independent methods of quantitative PCR and denaturing gradient gel electrophoresis. Quantification of the relative abundances of higher bacterial taxa showed that barnacles hosted a greater proportion of α-Proteobacteria compared to rock-associated biofilms (p < 0.01). Differences in relative abundances of other taxa were not observed but DGGE profiling suggested that differences were present at lower taxonomic levels. The capacity of these communities to influence larval settlement was assessed by growing multispecies biofilms on artificial medium, obtained by extracting nutrients from adult barnacles. Biofilms composed of shell-associated bacteria were capable of promoting conspecific settlement by 67% compared to control surfaces (p < 0.05), while rock-associated communities showed contrasting effects. A taxonomic comparison of settlement-stimulating and -inhibiting bacteria was performed by DGGE and band sequencing. All partial 16S rRNA genes sequenced were similar to members of the Vibrio and Pseudoalteromonas genera, suggesting that larvae can detect and respond to variations in the composition of microbial biofilms at low taxonomic levels. Our results indicate that barnacle larvae may be able to detect parentally-associated biofilms and use this information to settle close to members of its own species.     

Leaf growth and population dynamics of intertidal Zostera japonica on the western coast of Korea

Leaf production and population dynamics of Zostera japonica were examined at three elevations of an intertidal transect in Seungbongdo Island on the western coast of Korea. Morphometrics, shoot density, biomass, leaf production, reproductive effort and environmental factors were monitored from October 2001 to October 2002. Z. japonica grew well in the lower intertidal zone from 0.2 to 1.0 m above mean chart datum. The upper station (St. 1) exhibited a finer sediment grain size and richer organic content than the middle (St. 2) and lower stations (St. 3). The size of shoots and leaves was significantly greater at St. 1 than at St. 3, whereas the rhizome internodes were longer at St. 3. Despite differences in morphological characteristics among three stations, seagrass biomass and shoot density were not significantly different among study sites. Shoot density, biomass, morphometrics and leaf productivity exhibited clear seasonal variations, which varied along with seasonal changes of water and air temperature. Leaf productivity measured by the clip and reharvest method was highest in September (4.3 g DW m⁻² d⁻¹) and lowest in February (0.2 g DW m⁻² d⁻¹). Reproductive shoots rapidly increased to maximum density along with the high water temperature in July to September. In the intertidal zone, Z. japonica exhibited faster vegetative growth on muddy sand than on sand, probably due to the difference in nutrient supply. The seasonal changes of water and air temperature were considered to play an important role in the seasonal leaf growth of Z. japonica.     

Brevetoxin persistence in sediments and seagrass epiphytes of east Florida coastal waters

A bloom of Karenia brevis Davis developed in September 2007 near Jacksonville, Florida and subsequently progressed south through east Florida coastal waters and the Atlantic Intracoastal Waterway (ICW). Maximum cell abundances exceeded 10⁶ cells L⁻¹ through October in the northern ICW between Jacksonville and the Indian River Lagoon. The bloom progressed further south during November, and terminated in December 2007 at densities of 10⁴ cells L⁻¹ in the ICW south of Jupiter Inlet, Florida. Brevetoxins were subsequently sampled in sediments and seagrass epiphytes in July and August 2008 in the ICW. Sediment brevetoxins occurred at concentrations of 11–15 ng PbTx-3 equivalents (g dry wt sediment)⁻¹ in three of five basins in the northern ICW during summer 2008. Seagrass beds occur south of the Mosquito Lagoon in the ICW. Brevetoxins were detected in six of the nine seagrass beds sampled between the Mosquito Lagoon and Jupiter Inlet at concentrations of 6–18 ng (g dry wt epiphytes)⁻¹. The highest brevetoxins concentrations were found in sediments near Patrick Air Force Base at 89 ng (g dry wt sediment)⁻¹. In general, brevetoxins occurred in either seagrass epiphytes or sediments. Blades of the resident seagrass species have a maximum life span of less than six months, so it is postulated that brevetoxins could be transferred between epibenthic communities of individual blades in seagrass beds. The occurrence of brevetoxins in east Florida coast sediments and seagrass epiphytes up to eight months after bloom termination supports observations from the Florida west coast that brevetoxins can persist in marine ecosystems in the absence of sustained blooms. Furthermore, our observations show that brevetoxins can persist in sediments where seagrass communities are absent.     

Comparison of Zostera marina and maerl community metabolism

The photosynthetic and repiratory metabolism of Zostera marina and maerl communities was compared, in the same area of the Bay of Brest in March–April, using benthic chambers. P–E curves for both oxygen and carbon were established for bottom irradiances between 0 and 525 μmol m⁻² s⁻¹. An exponential function was fitted to calculate daily production. Community metabolic quotients did not differ for maerl and seagrass beds. Community photosynthetic quotients were significantly higher (1.19) whereas community respiratory quotients were lower (0.70) than 1. Maerl and seagrass bed P–E curves mainly differed by the minimum saturating irradiance (E_k). Net community production was estimated to 26.8 mmol C m⁻² d⁻¹ for Z. marina meadows and 8.6 mmol C m⁻² d⁻¹ for maerl beds. The two communities can, therefore, be considered as autotrophic during the March–April period. Community respiration did not differ between Z. marina meadows and maerl beds, with an average value of 53.8 mmol C m⁻² d⁻¹ during a day. In similar environmental conditions, the production of maerl beds corresponds to approximately one third that of seagrass meadows. The maerl communities, therefore, form productive ecosystems, relevant to temperate coastal ecosystems functioning.     

Urine nitrification with a synthetic microbial community

During long-term extra-terrestrial missions, food is limited and waste is generated. By recycling valuable nutrients from this waste via regenerative life support systems, food can be produced in space. Astronauts’ urine can, for instance, be nitrified by micro-organisms into a liquid nitrate fertilizer for plant growth in space. Due to stringent conditions in space, microbial communities need to be be defined (gnotobiotic); therefore, synthetic rather than mixed microbial communities are preferred. For urine nitrification, synthetic communities face challenges, such as from salinity, ureolysis, and organics.In this study, a synthetic microbial community containing an AOB (Nitrosomonas europaea), NOB (Nitrobacter winogradskyi), and three ureolytic heterotrophs (Pseudomonas fluorescens, Acidovorax delafieldii, and Delftia acidovorans) was compiled and evaluated for these challenges. In reactor 1, salt adaptation of the ammonium-fed AOB and NOB co-culture was possible up to 45 mS cm⁻¹, which resembled undiluted nitrified urine, while maintaining a 44 ± 10 mg NH₄⁺–N L⁻¹ d⁻¹ removal rate. In reactor 2, the nitrifiers and ureolytic heterotrophs were fed with urine and achieved a 15 ± 6 mg NO₃⁻–N L⁻¹ d⁻¹ production rate for 1% and 10% synthetic and fresh real urine, respectively. Batch activity tests with this community using fresh real urine even reached 29 ± 3 mg N L⁻¹ d⁻¹. Organics removal in the reactor (69 ± 15%) should be optimized to generate a nitrate fertilizer for future space applications.     

Effect of yak rumen content treatments on seed germination of 11 alpine meadow species on the Qinghai-Tibetan Plateau

The Qinghai-Tibetan Plateau is located in the ‘Third Pole’ of the world, characterized by a harsh environment. Despite this, the alpine meadow ecosystem have developed over a wide area but serious grassland degradation is threatening the ecological environment on the Plateau. Recruitment of new plants to the population, via germination and establishment, is vital to plant community survival. Previous work on the seeds in this area has mainly focused on community-wide germination strategies, seed germination characteristics and their correlations with seed size and seed mass. However, there have been no studies on the effects of soaking in rumen contents on the plant seed germination characteristics of alpine meadow species. The present study had two main objectives: (i) to determine the effect of fresh rumen content from yaks on seed germination characteristics and seedling growth of species common to the eastern Tibetan Plateau alpine meadow, and (ii) to develop an effective method to enhance seed germination. Seeds of 11 common species were collected together with fresh rumen content from three yaks that grazed there. Seed germination tests were conducted after they had been soaked in rumen content for one of six soaking periods (12, 24, 36, 48, 60 or 72 h). The seeds were incubated under natural light conditions of 8 h light at 25 °C and 16 h darkness at 15 °C, for the germination period of 34 days. The results showed that seed germination and seedling growth were affected by soaking time, seed coat completeness and seed type. After soaking in rumen content, the germination percentages of scarified (peeled or with the seed coat cut through) seeds of some species (true seeds Oxytropis ochrocephala and Medicago ruthenia var inschanica, nutlet Carex enervis, achenes Anemone rivularis and Polygonum sibiricum) and complete seeds of C. enervis, and A. rivularis were improved but the duration of soaking was also important. Seed germination of caryopsis Achnatherum inebrians (a toxic grass) was significantly inhibited by any exposure to rumen fluids. Scarified seeds generally had higher germination percentages than complete ones after treatment, but with the increase in soaking time, germination percentages declined and scarified seeds were more sensitive to the treatment than the complete seeds. After soaking in yak rumen content, the germination indices of scarified M. ruthenia at 12 h treatment, O. ochrocephala and achene Rumex acetosa at 12–24 h treatment, nutlet Kobresia humilis at 24 h treatment, P. sibiricum at 24–48 h treatment, C. enervis at 12–48 h treatment and A. rivularis at 12–60 h treatment were significantly higher than the control (P < 0.05), while the germination indices of complete C. enervis seeds at 12 h and 36 h treatment, and A. rivularis at 12–60 h treatment were significantly higher compared with the control. The germination indices of other species gradually decreased with the increase in soaking time. We concluded that yak rumen digestion could enhance, inhibit or not affect seed germination and seedling growth of the alpine meadow species, which might influence seedling recruitment, interspecific competition, and the plant community structure of the eastern Tibetan Plateau alpine meadow. Overall, yak digestion has a positive effect on alpine meadow seed germination and seed dispersal.     

Early responses of Bassia diffusa (Thunb.) Kuntze to submergence for different salinity treatments

Early responses of the salt marsh succulent Bassia diffusa (Thunb.) Kuntze to combined salinity and submergence were studied in a laboratory experiment aimed at determining the pattern of the response of photosynthetic pigments, membrane stability, oxalic acid and water relations to these stressors. Three key stages in the response were identified. A drop in chlorophyll a + b within 6 h (4.2 ± 0.2 to 2.4 ± 0.3 mg g^− 1 DM) with a corresponding increase in carotenoid concentration (0.6 ± 0.1 mg g^− 1 DM) indicated an immediate response to submergence. Oxalic acid concentration was highest on Day 4 (1.7 g g^− 1 DM) as opposed to control levels, indicative of its role in submergence tolerance, thus Day 4 may be the peak of positive acclimation. The third phase was marked by a sharp increase in electrolyte leakage to 47.5 ± 2.6% on Day 10, from 9.4 ± 1.4% on Day 7, with a corresponding decrease in total dissolved solutes between Days 7 and 10. Results suggest that oxalic acid accumulates under submergence possibly as a stabilising osmolyte. The threshold for tolerance of the species under submergence is 7 days with membrane damage thereafter. B. diffusa would not survive prolonged submergence (> 7 days) but could survive submergence of short duration (< 7 days) through continuous underwater photosynthesis, accumulation of osmolytes such as oxalic acid and carotenoid, and maintenance of relative water content and succulence within control levels. These data show that this upper intertidal salt marsh plant would be sensitive to prolonged inundation as a result of sea level rise or due to estuary mouth closure and a subsequent rise in water level.     

Epiphytic lichen indication of nitrogen deposition and climate in the northern rocky mountains,USA

Lichen bioindication can provide economical and spatially extensive monitoring of climate and pollution impacts on ecological communities. We used non-metric multidimensional scaling of lichen community composition and generalized additive models to analyze regional climate and pollution gradients in the northern Rocky Mountains, U.S. Temperature extremes, relative humidity, and N-deposition were strongly related to lichen community composition. Eutrophic species (genera Physcia, Xanthomendoza, and Xanthoria) were associated with high N deposition, low precipitation, and temperature extremes. Estimated N deposition in our study ranged from <0.5 to 4.26 kg N ha⁻¹ year⁻¹ with degradation to lichen communities observed at 4.0 kg N ha⁻¹ year⁻¹, the indicated critical load. The resulting model can track changes in climate and N pollution related to lichen communities over time, identify probable sensitive or impacted habitats, and provide key information for natural resource management and conservation. The approach is broadly applicable to temperate ecosystems worldwide.     

Long-term adaptations of a migratory bird (Little Tern Sternula albifrons) to quasi-natural flooding disturbance

Population size of migratory birds responds to various types of environmental factors, which affect different stages of bird population. In the current study, we analyzed a long-term avifauna monitoring database to investigate population changes in the migratory bird Little Tern, Sternula albifrons, with respect to a quasi-natural disturbance, flooding, induced by a regional characteristic climate pattern, the Korean Monsoon (KM), in the Nakdong River Estuary of South Korea. We scrutinized the time-delayed influence by means of wavelet transformation and year-to-year comparison. Little Tern individuals started to grow in April, and reached its maximum generally in May or June, and an abrupt decrease of individual number was observed after KM occurred. Sequential time-series analysis based on wavelet transformation revealed that the changing pattern of the population size of Little Tern in the estuary was linked to the previous year's flooding (a 9- to 10-month delay), which is regarded as the time difference between Little Tern breeding season and previous KM period. Stronger flooding waters during KM season expelled comparably more individuals of Little Tern from the estuary (r² = 0.595; p < 0.05; n = 9), and the more the individuals left, the smaller the bird arrived at the estuary in the next year. Further examination revealed that earlier initiation and longer duration of KM in year_t − 1 negatively affected the newly arriving Little Tern individuals in the current year (i.e., year_t; r² = 0.809 for impact of KM onset, r² = 0.909 for impact of KM duration; n = 10, respectively; p < 0.005). The Little Tern population gradually increased when summer flooding was not strong in the previous successive years, from which we concluded that the population of the migratory bird Little Tern tends to adapt to quasi-natural disturbance (flooding) to maintain their population size.     

Bacteriocidal effects of brevetoxin on natural microbial communities

The sensitivity of bacteria to the marine neurotoxins, brevetoxins, produced by the dinoflagellate Karenia brevis and raphidophytes Chattonella spp. remains an open question. We investigated the bacteriocidal effects of brevetoxin (PbTx-2) on the abundance and community composition of natural microbial communities by adding it to microbes from three coastal marine locations that have varying degrees of historical brevetoxin exposure: (1) Great Bay, New Jersey, (2) Rehoboth Bay, Delaware and (3) Sarasota Bay, Florida. The populations with limited or no documented exposure were more susceptible to the effects of PbTx-2 than the Gulf of Mexico populations which are frequently exposed to brevetoxins. The community with no prior documented exposure to brevetoxins showed significant (p = 0.03) changes in bacterial abundance occurring with additions greater than 2.5 μg PbTx-2 L⁻¹. Brevetoxin concentrations during K. brevis blooms range from ∼2.5 to nearly 100 μg L⁻¹ with typical concentrations of ∼10–30 μg L⁻¹. In contrast to the unexposed populations, there was no significant decrease in bacterial cell number for the microbial community that was frequently exposed to brevetoxins, which implies variable sensitivity in natural communities. The diversity in the bacterial communities that were sensitive to PbTx-2 declined upon exposure. This suggests that the PbTx-2 was selecting for or against specific species. Mortality was much higher in the 200 μg PbTx-2 L⁻¹ treatment after 48 h and >37% of the species disappeared in the bacterial communities with no documented exposure. These results suggest that toxic red tides may play a role in structuring bacterial communities.     

Optimization of biomass production with enhanced glucan and dietary fibres content by Pleurotus ostreatus ATHUM 4438 under submerged culture

This work was aimed at optimizing biomass production by the edible basidiomycete Pleurotus ostreatus ATHUM 4438 in a submerged process with enhanced glucan and dietary fibres content. β-Glucan from Pleurotus sp. (pleuran) has been used as food supplements due to its immunosuppressive activity. Like other dietary fibre components, oyster mushroom polysaccharides can stimulate the growth of colon microorganisms (probiotics), i.e. act as prebiotics. We used the FF MicroPlate for substrate utilization and growth monitoring. The pattern of substrate catabolism forms a substrate assimilation fingerprint which is useful in selecting media components for media optimization of maximum biomass production. Different carbon sources (95) were used and then 8 of them were tested in shake flask cultures. The effect of various organic and complex nitrogen sources on biomass production was also examined and response surface methodology based on central composite design was applied to explore the optimal medium composition. When the optimized culture medium was tested in a 20-L stirred tank bioreactor, using 57 g L⁻¹ xylose and 37 g L⁻¹ corn steep liquor, high yields (39.2 g L⁻¹) of dry biomass was obtained. The yield coefficients for total glucan and dietary fibres on mycelial biomass formed were 140 ± 4 and 625 ± 9 mg g⁻¹ mycelium dry weight, respectively.