Stress tolerance of the invasive macroalgae <Emphasis Type="Italic">Codium fragile</Emphasis> and <Emphasis Type="Italic">Gracilaria vermiculophylla</Emphasis> in a soft-bottom turbid lagoon

Invasive species are often hypothesized to have superior performance traits. We compared stress tolerance (as change in biomass) of the invasive macroalgae Codium fragile ssp. tomentosoides and Gracilaria vermiculophylla to the native macroalgae Fucus vesiculosus, Agardhiella subulata, Hypnea musciformis and Ulva curvata in Hog Island Bay, a shallow lagoon in Virginia, USA. We hypothesized that the success of the two aliens is due to their high tolerances of turbidity, sedimentation, desiccation, grazing and nutrient enrichment. Like many lagoons, Hog Island Bay is characterized by extensive intertidal mudflats, high turbidity and sedimentation, and high densities of omnivorous mud snails. Nutrient enrichment may also become a problem as land use practices in adjacent watersheds change. Contrary to our hypothesis, C. fragile was less resistant to sedimentation, desiccation and grazing than other algae and had low growth at all light and nutrient levels. This suggests that any superior performance of this invasive species compared to native algae is probably limited to microhabitats where stress is minimal and where bivalve shells facilitate recruitment and long-term persistence. In contrast, G. vermiculophylla was resistant to desiccation, burial and grazing, and was not negatively influenced by either high or low light or nutrient levels. These traits reflect the current success of G. vermiculophylla in already invaded lagoons and estuaries, and indicates that it will likely continue its spread in European and North American turbid and tidal soft-sediment systems.     

Nitrogen uptake responses of Gracilaria vermiculophylla (Ohmi) Papenfuss under combined and single addition of nitrate and ammonium

The ammonium (NH₄⁺) and nitrate (NO₃⁻) uptake responses of tetrasporophyte cultures from a Portuguese population of Gracilaria vermiculophylla were studied. Thalli were incubated at 5 nitrogen (N) levels, including single (50 μM of NH₄⁺ or NO₃⁻) and combined addition of each of the N sources. For the combined additions, the experimental conditions attempted to simulate 2 environments with high N availability (450 μM NO₃⁻ + 150 μM NH₄⁺; 250 μM NO₃⁻ + 50 μM NH₄⁺) and the mean N concentrations occurring at the estuarine environment of this population (30 μM NO₃⁻ + 5 μM NH₄⁺). The uptake kinetics of NH₄⁺ and NO₃⁻ were determined during a 4 h time-course experiment with N deprived algae. The experiment was continued up to 48 h, with media exchanges every 4 h. The uptake rates and efficiency of the two N sources were calculated for each time interval. For the first 4 h, G. vermiculophylla exhibited non-saturated uptake for both N sources even for the highest concentrations used. The uptake rates and efficiency calculated for that period (V_0-4 h), respectively, increased and decreased with increasing substrate concentration. NO₃⁻ uptake rates were superior, ranging from 1.06 ± 0.1 to 9.65 ± 1.2 μM g(dw)⁻¹ h⁻¹, with efficiencies of 19% to 53%. NH₄⁺ uptake rates were lower (0.32 ± 0.0 to 5.75 ± 0.08 μM g(dw)⁻¹ h⁻¹) but G. vermiculophylla removed 63% of the initial 150 μM and 100% at all other conditions. Uptake performance of both N sources decreased throughout the duration of the experiment and with N tissue accumulation. Both N sources were taken up during dark periods though with better results for NH₄⁺. Gracilaria vermiculophylla was unable to take up NO₃⁻ at the highest concentration but compensated with a constant 27% NH₄⁺ uptake through light and dark periods. N tissue accumulation was maximal at the highest N concentration (3.9 ± 0.25% dw) and superior under NH₄⁺ (3.57 ± 0.2% dw) vs NO3 (3.06 ± 0.1% dw) enrichment. The successful proliferation of G. vermiculophylla in estuarine environments and its potential utilization as the biofilter component of Integrated Multi-Trophic Aquaculture (IMTA) are discussed.     

Temporal and spatial dynamics of macroalgal communities along an anthropogenic salinity gradient in Biscayne Bay (Florida,USA)

The seasonal and spatial dynamics of two groups of macroalgae, drift algae and rhizophytes, commonly found in tropical seagrass meadows were studied. The aim of this study was to provide insight into how freshwater discharges may be altering seagrass-dominated nearshore tropical habitats. Species composition, biomass, and percent cover of macroalgae were collected at six Thalassia testudinum König dominated sites within Biscayne Bay, Florida, representing three salinity regimes: canal-influenced, natural sheet-flow, and oceanic conditions. Mean annual salinities in these three regimes correspond to 10, 25 and 35 psu, respectively, with much greater variability in the canal and sheet-flow regimes, than in the oceanic condition. There were distinct changes in the composition of the macroalgal community along this salinity gradient. Drift algae (Chondria spp., Laurencia spp.) were most commonly found at canal-disturbed sites (10–85 g m⁻²), while rhizophytic calcareous green algae (Halimeda spp., Penicillus spp.) were most abundant at the higher salinity oceanic sites (20–105 g m⁻²). Seasonal patterns exhibited by the two groups differed also, with drift algae being more abundant in the cooler dry-season months, while rhizophytic algae were more abundant during the warmer wet-season months. These periods of higher abundance correlated with higher growth rates (drift = 2.3% day⁻¹, rhizophytes = 0.85% day⁻¹) measured in representative species for each group. Grazing rates on drift algae were found to be low for tropical habitats and did not differ much between canal (0.44% h⁻¹) and oceanic sites (0.42% h⁻¹).     

Grazing of the invasive alga Codium fragile ssp. tomentosoides by the common periwinkle Littorina littorea: Effects of thallus size, age and condition

We examined the potential of herbivory by the common periwinkle Littorina littorea to limit recruitment and vegetative re-growth of the invasive green alga Codium fragile ssp. tomentosoides in a series of manipulative field experiments in tidepools on a wave-exposed rocky shore in Nova Scotia, Canada. Snails were excluded or included from circular plots (14 to 20 cm diameter) with cages to compare growth and survival of C. fragile against procedural (partial cages) or natural (uncaged) control plots. Our results show that L. littorea may restrict growth and survival of C. fragile by grazing new recruits (< 2 cm thallus length), fronds of adult thalli that are bleached and necrotic, and residual holdfasts (< 2 mm thickness) of detached thalli (artificially severed to mimic wave dislodgement). Once recruits grow beyond a critical size (~ 3 cm), or damaged tissues or holdfasts regenerate, grazing of C. fragile by L. littorea appears to be limited and ineffectual. Our experimental results corroborate correlative evidence from previous studies that herbivory by L. littorea limits the abundance of C. fragile in tidepools on the Atlantic coast of Nova Scotia, particularly pools in the high intertidal zone where these snails are abundant. Lower on the shore, littorinid grazing and physical stressors that render algae more vulnerable to grazers (e.g. UV radiation and freezing) are less intensive, and probably have less of a regulatory effect on populations of C. fragile.     

Effects of native and invasive macroalgal canopies on composition and abundance of mobile benthic macrofauna and turf-forming algae

We examined the effects of native kelps, Laminaria longicruris de la Pylaie and L. digitata (Hudson) Lamouroux, and of the invasive alga, Codium fragile ssp. tomentosoides (Van Goor) Silva, on the composition and abundance of mobile benthic macrofauna and of turf algae by measuring the response of these assemblages to experimental removal of the respective macroalgal canopy. From June 2003 to November 2004, we censused macrofauna and measured canopy cover within 4 × 10 m strips of alternating Canopy Intact (control) and Canopy Removed treatments in both a Codium- and a Laminaria-dominated habitat in the rocky subtidal zone of a semi-protected embayment on the Atlantic coast of Nova Scotia, Canada. Macroalgal canopy cover fluctuated seasonally, peaking in September/October (69% cover in 2003; 55% cover in 2004) for Codium and in May 2004 (70% cover) for kelps, and with both canopy types reaching a winter minimum in January 2004 (22 and 28% cover, respectively). In both Codium and Laminaria habitats, significant effects of canopy removal on the overall macrofaunal assemblage were evident only during periods in which canopy cover in the Canopy Intact treatment was ≥ 50%. In the Codium habitat, 4 out of 11 characteristic taxa were more abundant in the Canopy Intact treatment, where taxonomic diversity also was higher. In contrast, 4 out of 11 characteristic taxa in the Laminaria habitat were more abundant in the Canopy Removed treatment and diversity was similar between treatments. Turf algae were sampled in November 2004 and, despite between-treatment differences in the light regime, there was no significant effect of canopy removal. Our results indicate that selection of algal habitats by mobile macrofauna is likely determined by the different shelter and foraging opportunities offered by these morphologically dissimilar ecosystem engineers.     

Exposure times in rapid light curves affect photosynthetic parameters in algae

Short-and long-duration light curves were applied to four macroalgae (Ulva sp., Codium fragile, Ecklonia radiata and Lessonia variegata), and two microalgal species (Chlorella emersonii and Chaetoceros muellerii). With increasing light curve duration, the maximal relative electron transport rate increased by a factor of three in E. radiata, and by factors of 1.25 and 1.23 in C. emersonii and L. variegata, respectively, but did not change in C. fragile and Ch. muellerii. The light saturation point E_k increased by 26 μmol photons m⁻² s⁻¹ in C. emersonii and 20 μmol photons m⁻² s⁻¹ in Ch. muellerii and E. radiata with elevated light curve exposure times. Oscillatory patterns of the continuous fluorescence readings reflect accumulation of Q_A. Continuous fluorescence values increased, or decreased, by approximately 10% within light curve increments. However, oscillations of 25% were not uncommon, which shows that cells are changing their photo-physiological response state during steady light conditions. Increasing dark acclimation times prior to light curve application lowered maximal relative electron transport rates in the C. emersonii (from 28 ± 1.7 to 25 ± 1.2 for 15 and 95 min dark acclimation in short-duration light curves respectively). This effect was counterbalanced by longer light curve application. It can therefore be concluded that manipulation of light exposure and dark incubation prior to the experiment affects the photosynthetic response, presumably due to different activation states of photosynthetic and photoprotective mechanisms. The highly species-specific photo-response patterns imply that a common rapid light curve protocol will generate artefacts in some species.     

Climate and vegetation structure determine plant diversity in Quercus ilex woodlands along an aridity and human-use gradient in Northern Algeria

We studied the influence of environmental factors relating to climate, soil and vegetation cover on total species richness, species richness of different life-forms and species composition of plant communities occurring in Quercus ilex woodlands, across a 450-km long transect in Northern Algeria constituting a gradient of aridity and human use. We sampled vegetation and collected environmental data in 81 10 m × 10 m plots in five zones representing the largest Q. ilex woodlands throughout the study area, analysing them within an a priori hypothesis framework with the use of Path Analysis. Changes in plant diversity were mainly influenced by environmental factors related to precipitation and temperature regimes, as well as by total plant cover. In particular, changes in species composition were determined by factors associated with the temperature regime through their influence on both woody and annual herbaceous plant richness, and by factors related to the precipitation regime through their influence on perennial herbaceous plant richness, likely due to the differential tolerances of these functional groups to cold and water stress. Our results emphasize the importance of differences in environmental adaptability of the most important life-forms with regard to explaining compositional change (beta diversity) along aridity gradients, and the mediator role of total plant cover in relation to the effects of soil conditions on plant diversity.     

Kinetic mechanism of the Ca2+-dependent switch-on and switch-off of cardiac troponin in myofibrils

The kinetics of Ca²⁺-dependent conformational changes of human cardiac troponin (cTn) were studied on isolated cTn and within the sarcomeric environment of myofibrils. Human cTnC was selectively labeled on cysteine 84 with N-((2-(iodoacetoxy)ethyl)-N-methyl)amino-7-nitrobenz-2-oxa-1,3-diazole and reconstituted with cTnI and cTnT to the cTn complex, which was incorporated into guinea pig cardiac myofibrils. These exchanged myofibrils, or the isolated cTn, were rapidly mixed in a stopped-flow apparatus with different [Ca²⁺] or the Ca²⁺-buffer 1,2-Bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid to determine the kinetics of the switch-on or switch-off, respectively, of cTn. Activation of myofibrils with high [Ca²⁺] (pCa 4.6) induced a biphasic fluorescence increase with rate constants of >2000 s⁻¹ and ∼330 s⁻¹, respectively. At low [Ca²⁺] (pCa 6.6), the slower rate was reduced to ∼25 s⁻¹, but was still ∼50-fold higher than the rate constant of Ca²⁺-induced myofibrillar force development measured in a mechanical setup. Decreasing [Ca²⁺] from pCa 5.0-7.9 induced a fluorescence decay with a rate constant of 39 s⁻¹, which was approximately fivefold faster than force relaxation. Modeling the data indicates two sequentially coupled conformational changes of cTnC in myofibrils: 1), rapid Ca²⁺-binding (k_B ≈ 120 μM⁻¹ s⁻¹) and dissociation (k_D ≈ 550 s⁻¹); and 2), slower switch-on (k_on = 390s⁻¹) and switch-off (k_off = 36s⁻¹) kinetics. At high [Ca²⁺], ∼90% of cTnC is switched on. Both switch-on and switch-off kinetics of incorporated cTn were around fourfold faster than those of isolated cTn. In conclusion, the switch kinetics of cTn are sensitively changed by its structural integration in the sarcomere and directly rate-limit neither cardiac myofibrillar contraction nor relaxation.     

Probing the interactions of hemoglobin with antioxidant flavonoids via fluorescence spectroscopy and molecular modeling studies

Steady state and time resolved fluorescence spectroscopy, combined with molecular modeling computations, have been used to explore the interactions of two therapeutically important flavonoids, fisetin (3,7,3′,4′-OH-flavone) and 3-hydroxyflavone (3-HF), with normal human hemoglobin (HbA). Distinctive ‘two color’ fluorescence signatures and fairly high fluorescence anisotropy (r = 0.12-0.28) of fisetin and 3-HF reveal their specific interactions with HbA. Binding constants estimated from the fluorescence studies were ≈ 4.00 × 10⁴ M^− 1 and 9.83 × 10³ M^− 1 for fisetin and 3-HF respectively. Specific interactions with HbA were further confirmed from flavonoid-induced static quenching of the protein tryptophan fluorescence as indicated by: (a) bimolecular quenching constant K_q ? diffusion controlled limit (b) closely matched values of Stern-Volmer quenching constant and binding constant (c) τ_o/τ ≈ 1 (where τ_o and τ are the unquenched and quenched tryptophan fluorescence lifetimes respectively). Molecular docking and electrostatic surface potential calculations reveal contrasting binding modes of fisetin and 3-HF with HbA.     

Mechanistic features of Salmonella typhimurium propionate kinase (TdcD): Insights from kinetic and crystallographic studies

Short-chain fatty acids (SCFAs) play a major role in carbon cycle and can be utilized as a source of carbon and energy by bacteria. Salmonella typhimurium propionate kinase (StTdcD) catalyzes reversible transfer of the γ-phosphate of ATP to propionate during l-threonine degradation to propionate. Kinetic analysis revealed that StTdcD possesses broad ligand specificity and could be activated by various SCFAs (propionate > acetate ≈ butyrate), nucleotides (ATP ≈ GTP > CTP ≈ TTP; dATP > dGTP > dCTP) and metal ions (Mg^2 + ≈ Mn^2 + > Co^2 +). Inhibition of StTdcD by tricarboxylic acid (TCA) cycle intermediates such as citrate, succinate, α-ketoglutarate and malate suggests that the enzyme could be under plausible feedback regulation. Crystal structures of StTdcD bound to PO₄ (phosphate), AMP, ATP, Ap4 (adenosine tetraphosphate), GMP, GDP, GTP, CMP and CTP revealed that binding of nucleotide mainly involves hydrophobic interactions with the base moiety and could account for the broad biochemical specificity observed between the enzyme and nucleotides. Modeling and site-directed mutagenesis studies suggest Ala88 to be an important residue involved in determining the rate of catalysis with SCFA substrates. Molecular dynamics simulations on monomeric and dimeric forms of StTdcD revealed plausible open and closed states, and also suggested role for dimerization in stabilizing segment 235–290 involved in interfacial interactions and ligand binding. Observation of an ethylene glycol molecule bound sufficiently close to the γ-phosphate in StTdcD complexes with triphosphate nucleotides supports direct in-line phosphoryl transfer.     

Overyielding and the role of complementary use of nitrogen in wetland plant communities

Biodiversity and ecosystem functioning experiments have demonstrated that plant biomass of species grown in mixtures is often greater than plant biomass of monocultures (i.e., mixtures over yield). While we understand that plant species utilize resources differently, how a combination of species increases resource use and productivity is not well known, especially in wetland ecosystems. Here, we used a mesocosm experiment to explore diversity effects on plant biomass production and to examine the role of N partitioning as a mechanism for overyielding in wetland ecosystems. Plant functional groups (FGs) represented the unit of diversity, and we included five levels of diversity (0-4 FGs). To test for N partitioning, we used a stable isotope technique to determine niche breadth and proportion similarity of inorganic N use (NO₃⁻ and NH₄⁺) for individual FGs as well as mixtures containing 3 and 4 FGs. We found that total plant biomass increased in the first season from an average of 290 ± 60 SE g ash-free dry mass (AFDM) m⁻² at the 1 FG level to 490 ± 70 g AFDM m⁻² at the 4 FG level and in the second season from an average of 560 ± 80 g AFDM m⁻² at the 1 FG level to 1000 ± 90 g AFDM m⁻² at the 4 FG level indicating overyielding. Plant species comprising the majority of mesocosm biomass demonstrated preferential uptake of ¹⁵NO₃⁻, while species with relatively less biomass (e.g., Acorus calamus and Carex crinita) preferred ¹⁵NH₄⁺. Concentrations of ¹⁵N in biomass increased with FG richness, but only in the ¹⁵NO₃⁻ treatment. Niche breadth did not vary among levels of FG richness. We observed a greater niche overlap with an increase of FGs, with species taking up greater proportion of ¹⁵NO₃⁻ than ¹⁵NH₄⁺. Our results indicate that plant overyielding in wetland mesocosms is not the result of niche partitioning of N chemical forms, but is associated with greater uptake of NO₃.     

The effects of algae species and densities on the population growth of the marine rotifer, Colurella dicentra

Colurella dicentra clones isolated from bay water in the Mississippi Gulf Coast were cultured with artificial seawater. Experiments were conducted to determine the effects of six algae species (Nannochloropsis oculata, Tetraselmis chuii, Chaetoceros gracilis, Rhodomonas salina, Isochrysis galbana, and Prorocentrum micans), six C. gracilis densities, and six N. oculata densities (25,000, 50,000, 100,000, 250,000, 500,000, and 1,000,000 cells ml^− 1) on C. dicentra population growth. Algae type influenced rotifer production (p < 0.0001). C. gracilis treatment (9120 ± 3351SD) produced the highest number of rotifers followed by N. oculata (5760 ±2232SD). P. micans had the lowest number of rotifers, although not significantly different from numbers in T. chuii, R. salina, and I. galbana treatments (p > 0.05).The population growth rate (r) varied with algae species treatment. The highest values were recorded for C. gracilis treatment (0.22 to 0.26 d^− 1), followed by N. oculata (0.21 to 0.24 d^− 1), and the lowest for P. micans (− 0.19 to 0.14 d^− 1). C. gracilis and N. oculata densities had significant effects (p < 0.0001) on C. dicentra population growth. The highest rotifer production was recorded at a C. gracilis density of 100,000 cells ml^− 1, followed by 250,000 cells ml^− 1 and 50,000 cells ml^− 1. Algae densities of 500,000 cells ml^− 1 and above produced the lowest rotifer numbers. Population growth rate (r) varied with C. gracilis densities. The highest values were observed for C. gracilis concentrations of 100,000 cells ml^− 1 (0.17 to 0.19 d^− 1), and the lowest for concentrations of 500,000 cells ml^− 1 and above (− 0.19 to 0.09 d^− 1). The 100,000 cells ml^− 1N. oculata density gave the highest rotifer production followed by 50,000, 250,000, 25,000, and 500,000 cells ml^− 1. Algae densities of 1,000,000 cells ml^− 1 produced the lowest rotifer numbers. Population growth rate (r) varied with N. oculata densities, with the highest values obtained for algae densities of 100,000 cells ml^− 1 (0.35 to 0.40 d^− 1), and the lowest for concentrations of 1,000,000 cells ml^− 1 (0.05 to 0.012 d^− 1). This is the first report of C. dicentra in Mississippi Coastal waters, and perhaps the smallest marine rotifer species (93 by 49 μm) ever cultured successfully.     

Parrotfish bioerosion on Egyptian Red Sea reefs

Parrotfishes (family Scaridae) are important agents in marine bioerosion. Here, the feeding ecology of seven species of parrotfishes was studied on Egyptian Red Sea reefs. The most abundant species on both the reef flat and slope was Chlorurus sordidus. In contrast, C. gibbus had the lowest abundance on the reef flat, and Cetoscarus bicolor was the least abundant species on the reef slope. Scarus niger exhibited the highest feeding rate (98.9 bites 5 min^− 1), followed by C. sordidus (76.5 bites 5 min^− 1), whereas the rates for C. bicolor and C. gibbus were low (29.4 and 31.9 bites 5 min^− 1, respectively). The daily feeding patterns of all seven species showed agreement in that activity was relatively constant over the day, with highest values in the early afternoon (1400 h) and a steady decrease until 1800 h. C. sordidus was more similar to S. niger and S. ghobban in showing somewhat higher activities in the morning (0800 h) followed by a slight decrease until noon. The average bite volumes of C. gibbus and C. bicolor were high (0.114 and 0.110 cm³, respectively), whereas S. niger had the lowest average value (0.002 cm³). Based on their feeding intensity, C. gibbus, S. ghobban and C. bicolor have high bioerosion rates on the Egyptian Red Sea reefs. Overall, S. ghobban is the most important bioeroder because it is more abundant than the other two species. All parrotfish species fed on dead coral and hard substrates which are rich in algae, but C. gibbus, C. bicolor and S. ghobban also fed on live coral on both reef zones; C. sordidus avoided live coral. The fresh scars on live coral were bigger than on dead coral because the three large parrotfish (C. gibbus, C. bicolor and S. ghobban) fed mainly on live corals.     

Sorgoleone,a sorghum root exudate: Algicidal activity and acute toxicity to the ricefish Oryzias latipes

The discovery of natural and natural-based compounds has resulted in its application as an alternative to synthetic algicides to control harmful algae in aquatic systems. Of the many natural-product-based algicides, sorgoleone, a natural plant product from Sorghum bicolor root exudates has been investigated for its controlling effect on different algal species and its acute fish toxicity. Growth of the blue green algal species Microcystis aeruginosa Kützing was completely inhibited by the crude methanol extract of sorghum root at 20 μg mL⁻¹. The most noticeable inhibition was observed in the bioassay of n-hexane soluble extract, where 98% growth inhibition occurred in M. aeruginosa at the concentration of 1.25 μg mL⁻¹. Sorgoleone very effectively controlled blue green algae inhibiting 97% of M. aeruginosa at 0.5 μg mL⁻¹ and 99% of Anabaena affinis Lemmermann at 4 μg mL⁻¹. In contrast, inhibition of the green algae species Chlorella vulgaris Beijerinck and Scenedensmus spp. at 16 μg mL⁻¹ sorgoleone was 87 and 68%, respectively. There were no mortalities or adverse effects observed in any of the fish exposed to water control, solvent control, and a nominal concentration of 1 μg mL⁻¹ during the test period. The no observed effect concentration (NOEC) value was 1.5 μg mL⁻¹ for the tested fish (O. latipes). Sorgoleone can be considered as an effective and an ecologically and environmentally sustainable approach to controlling harmful algae.     

Landscape-level tree diversity assessment in tropical forests of southern Eastern Ghats,India

This large-scale, landscape-level study aims to assess tree species diversity, stem density and stand structure of six major tropical hill forests of southern Eastern Ghats, India, namely, Bodamalai (BM), Chitteri (CH), Kalrayan (KA), Kolli hills (KO), Pachaimalai (PM) and Shervarayan hills (SH). The Eastern Ghats of India is relatively under-studied compared with the Western Ghats biodiversity hotspot. The entire stretch of southern Eastern Ghats was divided into smaller grids of 6.25 km × 6.25 km, totaling to 120 grids. Within each grid, a belt transect of 0.5 ha (5 m × 1000 m) area was laid and all trees ≥30 cm girth at breast height (gbh) were enumerated. A total of 272 tree species (≥30 cm gbh) that belonged to 181 genera and 62 families were recorded in the total 60 ha area inventoried. Diversity indices such as Shannon, Simpson and Fisher's alpha indices were 2.44, 0.03 and 42.1, respectively, for the whole 60 ha area. One way ANOVA revealed that the species richness varied significantly across the six sites (F_(5,823) = 4.854, p < 0.0002). Also, the contribution of tree species to total species richness classified by three plant types viz. evergreen, brevi-deciduous and deciduous species varied significantly across the sites (One way ANOVA: F_(2,15) = 10.05, p < 0.002). Similarity indices such as Jaccard and Sørensen showed that sites CH and KA are more similar in terms of species composition. The total stand density and basal area for the total 60 ha area were 27,412 stems (457 stems ha⁻¹) and 1012.12 m² (16.9 m² ha⁻¹), respectively. The stand density and basal area for the six sites ranged from 290 (in site BM) to 527 stems ha⁻¹ (in site KA) and from 5.6 (in site BM) to 24.4 m² ha⁻¹ (in site KO), respectively. Stand density and basal area of tree species varied significantly across the six hill complexes (F_(5,823) = 4.85, p < 0.0002 and F_(5,823) = 2.71, p < 0.02, respectively). A positive correlation was obtained between stand density and species richness in sites PM (r_s = 0.65, p < 0.05) and SH (r_s = 0.67, p < 0.05), but not in other sites. The predominant tree species in the tropical forests of southern Eastern Ghats include Albizia amara, Euphorbia antiquorum, Canthium dicoccum var. dicoccum, Memecylon edule, Chloroxylon swietenia and Nothopegia heyneana. Taxonomically, Euphorbiaceae constituted the most diverse family with 25 species. Whereas, by tree abundance the Mimosaceae with 4126 stems enumerated from the 60 ha area formed the dominant family. Bray–Curtis cluster analysis, based on tree species composition and abundance revealed that the low-diverse site BM formed a separate entity from other hill complexes. This large-scale tree diversity inventory provides a baseline data for a variety of investigations and is expected to be useful for effective forest management and biodiversity conservation of southern Eastern Ghats region.     

Marinifilum flexuosum sp. nov., a new Bacteroidetes isolated from coastal Mediterranean Sea water and emended description of the genus Marinifilum Na et al., 2009

A facultatively anaerobe, moderately halophilic, Gram-negative, filamentous, non motile and unpigmented bacterium, designated M30^T, was isolated from coastal Mediterranean Sea water in Valencia, Spain. Phylogenetic analysis based on 16S rRNA sequences placed this strain in the phylum “Bacteroidetes” with Marinifilum fragile JC2469^T as its closest relative with 97% sequence similarity. Average nucleotide identity (ANI) values between both strains were far below the 95% threshold value for species delineation (about 89% using BLAST and about 90% using MUMmer). A comprehensive polyphasic study, including morphological, biochemical, physiological, chemotaxonomic and phylogenetic data, confirmed the independent species status of strain M30^T within the genus Marinifilum, for which the name Marinifilum flexuosum sp. nov. is proposed. The type strain of Marinifilum flexuosum is M30^T (=CECT 7448^T = DSM 21950^T).     

Phenology of the Mediterranean seagrass Posidonia oceanica (L.) Delile: Medium and long-term cycles and climate inferences

The results of 15 years of monitoring of Posidonia oceanica in the “Cinque Terre” Marine Protected Area (NW Mediterranean) are presented. Seasonal data on meadow characteristics (cover and shoot density), plant phenology (leaf number, leaf length and width, leaf brown portion, undamaged leaves), lepidochronology, leaf epiphyte cover and herbivore pressure collected from three stations at 5, 10 and 17 m depth were compared. Time-series analyses showed both medium-term (5 < years) and long-term cycles (from 5 to more than 20 years). The comparison of annual cycles with sea surface temperatures (SST) and rainfall showed correlations that differed in relation to depth and, in the case of epiphytes, with each side (internal and external) of the leaf blade. Meadow parameters (visual cover, shoot percent cover) and plant parameters (leaf number, number of undamaged leaves, number of scales shoot⁻¹) showed a positive trend in accordance with the rise of air and sea surface temperature recorded over these last decades. Shoot density and leaf width showed exceptions. Leaf length, leaf brown portion length and the number of undamaged leaves shoot⁻¹ showed positive or negative long-term trends, whose variability could not be related to climate data alone. The two major groups of epiphytes (encrusting algae and the bryozoan Electra posidoniae) showed negative trends. Grazing variability could be explained only partially by climate parameters. Epiphyte cover was found to be related to the NAO index.In conclusion, data showed that the effects of the climate change in terms of both sea surface temperature rising and rainfall decreasing may affect the growth cycles of P. oceanica on two levels: on a decadal level, with positive or negative trends in meadow and plant characteristics and in epiphyte cover; on yearly and seasonal levels, influencing endogenous plant growth rhythms, as in the case of leaf production cycle.     

Stability and solvation of alkali metal ion complexes with dibenzo-30-crown-10

Stability constants for the 1:1 complexes of dibenzo-30-crown-10 (DB30C10) with alkali metal ions have been determined at 25 °C in nitromethane and water by conductometry and capillary electrophoresis, respectively. Transfer activity coefficients of DB30C10 and its complexes from nitromethane to S (S = water, acetonitrile, propylene carbonate, methanol, and N,N-dimethylformamide) have been determined at 25 °C to evaluate the solvation properties. The stability constant in the poorly solvating solvent, nitromethane, decreases with increasing metal ion size, Na⁺ > K⁺ > Rb⁺ > Cs⁺, reflecting the intrinsic selectivity governed by electrostatic interaction between the metal ion and the ether oxygen atoms. It is also suggested that a part of the ether oxygen atoms does not bind to the metal ion in the Na(DB30C10)⁺ complex. The aqueous stability constant varies as Na⁺ ? K⁺ ≈ Rb⁺ ≈ Cs⁺; this selectivity pattern is similar to that in acetonitrile, propylene carbonate, and methanol. The complex stability in water is very low compared to that in the nonaqueous solvents, owing to hydrogen bonding of water to the oxygen atoms of the free crown ether. The transfer activity coefficient values show that DB30C10 shields all the metal ions effectively from the solvents and lead to the conclusion that the complexation selectivity in S receives a significant contribution from the solvation of the free metal ions. The Na(DB30C10)⁺ complex has specific interaction with water, causing much lower K⁺/Na⁺ selectivity in H₂O than in MeOH.     

Cation effect on energy transfer reactions from [Tb(2,6-pyridinedicarboxylate)3] to anionic chromium(III) and neodymium(III) complexes in aqueous solutions

Cation effects are studied on the excitation energy transfer reaction between anionic complexes, i.e., [Tb(dpa)₃]³⁻ (dpa=2,6-pyridinedicarboxylate) quenched by [Cr(ox)₃]³⁻ (ox=oxalate ion), [Cr(mal)₃]³⁻ (mal=malonate ion) and [Nd(dpa)₃]³⁻ in aqueous solutions in the presence of alkali metal ions added for adjustments of ionic strengths. In the quenching reaction of [Cr(ox)₃]³⁻, magnitudes of quenching rate constants (k_q) and energy transfer rate constant in encounter complex (k₁) are changed by the cations in the order of Li⁺ < Na⁺ < K⁺ ≈ Rb⁺ ≈ Cs⁺, that is quite contrary of the cation effect on energy transfer reaction between [Ru(N-N)₃]²⁺ and [Cr(ox)₃]³⁻, reported in the previous paper. On the other hand, the rate constants in quenching reactions by [Cr(mal)₃]³⁻ and [Nd(dpa)₃]³⁻ remain almost constant. This result indicates that more separated donor-acceptor pair is not sensitive to coexisting cations.     

Mixed-valency with cyanides as terminal ligands: Diruthenium(III,II) complexes with the 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine bridge and variable co-ligands (CN vs. bpy or NH3)

New diruthenium complexes (PPN)₄[(NC)₄Ru(μ-bptz)Ru(CN)₄], (PPN)₄1, and [(bpy)₂Ru(μ-bptz)Ru(CN)₄], 2, (PPN⁺ = bis(triphenylphospine)iminium; bptz = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine; bpy = 2,2′-bipyridine), were synthesised and characterised by spectroscopic and electrochemical techniques. The comproportionation constant K_c = 10^7.0 of the mixed-valent species [(NC)₄Ru(μ-bptz)Ru(CN)₄]³⁻ as obtained by oxidation of 1⁴⁻ in CH₃CN is much lower than the K_c = 10^15.0 previously detected for [(H₃N)₄Ru(bptz)Ru(NH₃)₄]⁵⁺, reflecting the competition between CN⁻ and bptz for the π-electron density of the metals. Comparison with several other bptz-bridged diruthenium(II,III) complexes reveals an approximate correlation between K_c and the diminishing effective π acceptor capacity of the ancillary terminal ligands. In addition to the intense MLCT absorption at λ_max = 624 nm, the main IVCT (intervalence charge transfer) band of 1³⁻ was detected by spectroelectrochemistry at λ_max = 1695 nm (in CH₃CN; ε = 3200 M⁻¹ cm⁻¹). The experimental band width at half-height, Δν_1/2 = 2700 cm⁻¹, is slightly smaller than the theoretical value Δν_1/2 = 3660 cm⁻¹, calculated from the Hush approximation for Class II mixed-valent species. In agreement with comparatively moderate metal-metal coupling, the mixed-valent intermediate 1³⁻ was found to be EPR silent even at 4 K. The unsymmetrical mixed-valent complex [(bpy)₂Ru^II(μ-bptz)Ru^III(CN)₄]⁺, obtained in situ by bromine oxidation of 2 in CH₃CN/H₂O, displays a broad NIR absorption originating from an IVCT transition at λ_max = 1075 nm (ε ≈ 1000 M⁻¹ cm⁻¹, Δν_1/2 ≈ 4000 cm⁻¹). In addition, the lifetime of the excited-state of the mononuclear precursor complex [Ru(bptz)(CN)₄]²⁻ was measured in H₂O by laser flash photolysis; the obtained value of τ = 19.6 ns reveals that bptz induces a metal-to-ligand electronic delocalisation effect intermediate between that induced by bpy and bpz (bpz = 2,2′-bipyrazine) in analogous tetracyanoruthenium complexes.