Thermal tolerance and preference of exploited turbinid snails near their range limit in a global warming hotspot

Predicted global climate change has prompted numerous studies of thermal tolerances of marine species. The upper thermal tolerance is unknown for most marine species, but will determine their vulnerability to ocean warming. Gastropods in the family Turbinidae are widely harvested for human consumption. To investigate the responses of turbinid snails to future conditions we determined critical thermal maxima (CTMax) and preferred temperatures of Turbo militaris and Lunella undulata from the tropical-temperate overlap region of northern New South Wales, on the Australian east coast. CTMax were determined at two warming rates: 1 °C/30 min and 1 °C/12 h. The number of snails that lost attachment to the tank wall was recorded at each temperature increment. At the faster rate, T. militaris had a significantly higher CTMax (34.0 °C) than L. undulata (32.2 °C). At the slower rate the mean of both species was lower and there was no significant difference between them (29.4 °C for T. militaris and 29.6 °C for L. undulata). This is consistent with differences in thermal inertia possibly allowing animals to tolerate short periods at higher temperatures than is possible during longer exposure times, but other mechanisms are not discounted. The thermoregulatory behaviour of the turban snails was determined in a horizontal thermal gradient. Both species actively sought out particular temperatures along the gradient, suggesting that behavioural responses may be important in ameliorating short-term temperature changes. The preferred temperatures of both species were higher at night (24.0 °C and 26.0 °C) than during the day (22.0 °C and 23.9 °C). As the snails approached their preferred temperature, net hourly displacement decreased. Preferred temperatures were within the average seasonal seawater temperature range in this region. However, with future predicted water temperature trends, the species could experience increased periods of thermal stress, possibly exceeding CTMax and potentially leading to range contractions.     

Vulnerability to climate warming and acclimation capacity of tropical and temperate coastal organisms

Ecological forecasting on the likely impacts of climate warming is crucial at a time when several ecosystems seem to be responding to this environmental threat. Among the most important questions are: which are the most vulnerable organisms to climate warming and where are they? Recently, there has been debate on whether the tropics or temperate zones are more vulnerable to warming. Vulnerability toward higher temperatures will depend on the organisms’ thermal limits and also on their acclimation capacity, which remains largely unknown for most species. The aim of the present work was to estimate (1) the upper thermal limits (Critical Thermal Maximum (CTMax)), (2) the warming tolerance (CTMax – Maximum Habitat Temperature) and (3) the acclimation capacity of tropical and temperate rocky shore organisms. Differences in biological groups (decapod crustaceans vs fish) were investigated and the effect of region (tropical vs temperate) and habitat (intertidal vs subtidal) was tested. Overall, 35 species were tested. For the assessment of the acclimation capacity, tropical-temperate pairs of closely related species of shrimp, crab and fish were selected. Warming tolerance was higher for temperate species than for tropical species and higher for subtidal species than for intertidal species, confirming that species with the highest thermal limits have the lowest warming tolerance. All species tested presented some acclimation capacity (CTMax_Trial − CTMax_Control), with the exception of gobiid fish, which was not observed to acclimate. The tropical species tested showed a lower acclimation capacity than their temperate counterparts. Given that tropical rocky shore organisms are already living very close to their thermal limits and that their acclimation capacity is limited, it is likely that the impacts of global warming will be evident sooner in the tropics than in the temperate zone.     

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.     

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.     

Mixotrophy in the newly described dinoflagellate Yihiella yeosuensis: A small,fast dinoflagellate predator that grows mixotrophically,but not autotrophically

To investigate tropical roles of the newly described Yihiella yeosuensis (ca. 8 μm in cell size), one of the smallest phototrophic dinoflagellates in marine ecosystems, its trophic mode and the types of prey species that Y. yeosuensis can feed upon were explored. Growth and ingestion rates of Y. yeosuensis on its optimal prey, Pyramimonas sp. (Prasinophyceae), as a function of prey concentration were measured. Additionally, growth and ingestion rates of Y. yeosuensis on the other edible prey, Teleaulax sp. (Cryptophyceae), were also determined for a single prey concentration at which both these rates of Y. yeosuensis on Pyramimonas sp. were saturated. Among bacteria and diverse algal prey tested, Y. yeosuensis fed only on small Pyramimonas sp. and Teleaulax sp. (both cell sizes = 5.6 μm). With increasing mean prey concentrations, both specific growth and ingestion rates of Y. yeosuensis increased rapidly before saturating at a mean Pyramimonas concentration of 109 ng C mL⁻¹ (2725 cells mL⁻¹). The maximum growth rate (mixotrophic growth) of Y. yeosuensis fed with Pyramimonas sp. at 20 °C under a 14:10-h light-dark cycle of 20 μE m⁻² s⁻¹ was 1.32 d⁻¹, whereas the growth rate of Y. yeosuensis without added prey was 0.026 d⁻¹. The maximum ingestion rate of Y. yeosuensis fed with Pyramimonas sp. was 0.37 ng C predator⁻¹ d⁻¹ (9.3 cells predator⁻¹ d⁻¹). At a Teleaulax concentration of 1130 ng C mL⁻¹ (66,240 cells mL⁻¹), growth and ingestion rates of Y. yeosuensis fed with Teleaulax sp. were 1.285 d⁻¹ and 0.38 ng C predator⁻¹ d⁻¹ (22.4 cells predator⁻¹ d⁻¹), respectively. Thus, Y. yeosuensis rarely grows without mixotrophy, and mixotrophy supports high growth rates in Y. yeosuensis. Y. yeosuensis has the highest maximum mixotrophic growth rate with the exception of Ansanella graniferaamong engulfment feeding mixotrophic dinoflagellates. However, the high swimming speed of Y. yeosuensis (1572 μm s⁻¹), almost the highest among phototrophic dinoflagellates, may prevent autotrophic growth. This evidence suggests that Y. yeosuensis may be an effective mixotrophic dinoflagellate predator on Pyramimonas and Teleaulax, and occurs abundantly during or after blooms of these two prey species.     

Treatment of domestic wastewater in tropical,subsurface flow constructed wetlands planted with Canna and Heliconia

Constructed wetlands have a good potential for wastewater treatment in developing countries due to the simple operation and low implementation costs. Ornamental plants like Canna and Heliconia are used in the wetlands to increase their aesthetic value and these two species were compared in this study. Six pilot scale horizontal subsurface flow constructed wetland units were constructed at the Asian Institute of Technology (AIT) campus in Bangkok, Thailand, of which three were planted with Heliconia psittacorum L.f. × H. Spathocircinata (Aristeguieta) and three with Canna × generalis L. Bailey. The beds were loaded with domestic wastewater in four trials with hydraulic loading rates ranging from 55 to 440 mm d^?1 corresponding to nominal detention times between 12 h and 4 days. Both plant species grew well in the systems and especially Canna had high growth rates (3100 ± 470 g DW m^?2 yr^?1) compared to Heliconia (550 ± 90 g DW m^?2 yr^?1). TSS mass removal rates were very high with efficiencies >88% even at hydraulic loading rates of 440 mm d^?1. COD mass removal rates varied between 42 and 83% depending on the loading rates. The removal rate constants for COD as fitted by the first-order k–C^* model were estimated to be 0.283 and 0.271 m d^?1 for Canna and Heliconia beds, respectively (C^* = 28.1 and 26.7 mg l^?1). Removals of nitrogen (N) and phosphorus (P) were low compared to the loading rates, but removal of total-N was higher in the beds planted with Canna than in beds with Heliconia because of the higher growth rate of Canna. It is concluded that ornamental species like Canna and Heliconia can be used to enhance the aesthetic appearance and hence the public acceptance of wastewater treatment systems in tropical climates. Canna is the preferred species from a treatment perspective because of its more vigorous growth, but since Heliconia has an economic potential as cut flowers may be preferred in many cases.     

Interspecific variability of plant stomatal response to step changes of [CO2]

The kinetics of a stomatal response to sudden increases or decreases of CO₂ concentrations ([CO₂]) was studied in 13 plant species growing in the field. Plants were well supplied with water. In each plant, gas exchange measurements were made on a fully developed leaf that was first left to achieve steady-state stomatal conductance (g_s) at 400 μmol (CO₂) mol⁻¹) and then exposed to a step change of [CO₂] (to 700 μmol mol⁻¹ in one experiment; and to 700 and back to 400 μmol mol⁻¹ in a second experiment). Porometric data were captured in intervals of 3 s until a new steady state was reached.A comparison of t_1/2, the half-time needed to achieve new g_s, indicates similar responses of stomata in grasses when compared to herbs. The stomata of C₄ plants responded in approximately 5 min, the highest closure rate was detected in Echinochloa crus-galli and Digitaria sanguinalis. Opening rates were similar to closing rates and the response as a whole was rather symmetric. In C₃ plants, the full response of stomata was much slower. Analysis revealed differences in absolute rates of g_s change between C₃ and C₄ plants. These differences can be related to the specificities of the type of photosynthetic metabolism. C₄ photosynthesis enables plants to reduce g_s, which can hasten further changes of diffusivity in response to the environmental signals. A possible coupling of C₄ metabolism to the regulation of guard cells also has to be taken into account when explaining the observed results.     

Understanding the blob bloom: Warming increases toxicity and abundance of the harmful bloom diatom Pseudo-nitzschia in California coastal waters

The toxic diatom genus Pseudo-nitzschia produces environmentally damaging harmful algal blooms (HABs) along the U.S. west coast and elsewhere, and a recent ocean warming event coincided with toxic blooms of record extent. This study examined the effects of temperature on growth, domoic acid toxin production, and competitive dominance of two Pseudo-nitzschia species from Southern California. Growth rates of cultured P. australis were maximal at 23 °C (∼0.8 d⁻¹), similar to the maximum temperature recorded during the 2014–2015 warming anomaly, and decreased to ∼0.1 d⁻¹ by 30 °C. In contrast, cellular domoic acid concentrations only became detectable at 23 °C, and increased to maximum levels at 30 °C. In two incubation experiments using natural Southern California phytoplankton communities, warming also increased the relative abundance of another potentially toxic local species, P. delicatissima. These results suggest that both the toxicity and the competitive success of particular Pseudo-nitzschia spp. can be positively correlated with temperature, and therefore there is a need to determine whether harmful blooms of this diatom genus may be increasingly prevalent in a warmer future coastal ocean.     

Uptake and allocation of 13C by Enhalus acoroides at sites differing in light availability

Carbon fixation and allocation were studied using ¹³C incubation and leaf marking techniques in mature monospecific stands of Enhalus acoroides L.f. Royle in August 1998 and January 1999 in Banten Bay, Indonesia. The highest rate of ¹³C uptake (>0.008 g ¹³C g C⁻¹ d⁻¹) was found in the middle to distal parts of leaves of E. acoroides. Young and senescing leaves numbers had lower ¹³C incorporation compared to mature leaves. The incorporation of ¹³C by epiphytes on the leaves was higher than that of the leaves themselves (>0.01 g ¹³C g C⁻¹ d⁻¹). The results showed that turbidity of the water influenced the leaf growth, productivity and Relative Growth Rate of E. acoroides, which were lower at Kepuh Island, the more turbid site. However, at Kepuh Island, where the water column was turbid, the plant could still harvest sufficient light for an uptake rate of ¹³C, higher than the uptake rates at Kubur and Panjang Islands, stations with a much more transparent water column (on average 0.0047 g ¹³C g C⁻¹ d⁻¹ at Kepuh Island, versus 0.0045 g ¹³C g C⁻¹ d⁻¹ at Panjang Island and 0.0034 g ¹³C g C⁻¹ d⁻¹ at Kubur Island). There was evidence that ¹³C was exported from the incubated shoots to the roots and rhizomes and to neighboring shoots of E. acoroides in clear water, but not in turbid water. We suggest that single shoots of E. acoroides are able to grow in turbid water under low light conditions. They assimilate sufficient carbon for their own maintenance but are not able to export to neighboring plant parts.     

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.     

Feeding by the newly described heterotrophic dinoflagellate Stoeckeria changwonensis: A comparison with other species in the family Pfiesteriaceae

The feeding ecology of the newly described heterotrophic dinoflagellate Stoeckeria changwonensis was explored. The feeding behavior of S. changwonensis, and the kinds of prey species that it feeds on were investigated with several different types of microscopes and high-resolution video-microscopy. Additionally, the growth and ingestion rates of S. changwonensis as a function of prey concentration for perch (Lateolabrax japonicus) blood cells, the raphidophyte Heterosigma akashiwo, the cryptophytes Rhodomonas salina and Teleaulax sp., and the phototrophic dinoflagellate Amphidinium carterae prey were measured. S. changwonensis feeds on prey through a peduncle, after anchoring the prey by using a tow filament. This type of feeding behavior is similar to that of Stoeckeria algicida, Pfiesteria piscicida, and Luciella masanensis in the family Pfiesteriaceae; however, S. changwonensis feeds on various kinds of prey species different from those of the other heterotrophic dinoflagellates. S. changwonensis ingested perch blood cells and diverse algal species, in particular, the large thecate dinoflagellate Lingulodinium polyedrum which are not eaten by the other peduncle feeders. H. akashiwo and the perch blood cells supported positive growth of S. changwonensis, but R. salina, Teleaulax sp., and A. carterae which support positive growth of P. piscicida and L. masanensis did not support positive growth of S. changwonensis. With increasing mean prey concentration the growth rates for S. changwonensis on H. akashiwo and the perch blood cells increased rapidly and then slowly or became saturated. The maximum growth rates of S. changwonensis on H. akashiwo and the perch blood cells were 0.376 and 0.354 d⁻¹, respectively. Further, the maximum ingestion rates of S. changwonensis on H. akashiwo and the perch blood cells were 0.35 ng C predator⁻¹ d⁻¹ (3.5 cells predator⁻¹ d⁻¹) and 0.27 ng C predator⁻¹ d⁻¹ (29 cells predator⁻¹ d⁻¹), respectively. These maximum growth and ingestion rates of S. changwonensis on H. akashiwo, the perch blood cells, R. salina, Teleaulax sp., and A. carterae differed considerably from those of S. algicida, P. piscicida, and L. masanensis on the same prey species. Thus, the feeding behavior of S. changwonensis may differ from that of other species in the family Pfiesteriaceae.     

Carbon sequestration potential of green roofs using mixed-sewage-sludge substrate in Chengdu World Modern Garden City

Green roofs which use sewage sludge to sequestrate urban carbon dioxide may represent a potential opportunity to evaluate carbon sequestration benefits for the urban development under increasing global climate change. In this study, green roofs composed of 6 small green segments with two different substrates, mixed-sewage-sludge substrate (MSSS, volume ratio of sewage sludge and local-natural soil 1:1), and local-natural soil (LNS), three different substrate depths (20 cm, 25 cm and 30 cm), and three types of native plants (Ligustrum vicaryi, Neottia auriculata, and Liriope spicata) in Chengdu City were established to determine carbon sequestration from July 2012 to July 2013 through assessment of the carbon storage and sequestration. Results show that the average carbon storage of MSSS and LNS on green roofs was respectively 13.15 kg C m⁻² and 8.58 kg C m⁻², and the average carbon sequestration followed the order of LNS (3.89 kg C m⁻² yr⁻¹) > MSSS (3.81 kg C m⁻² yr⁻¹). Thus MSSS could be considered as a potential material for carbon sequestration. The carbon storage and carbon sequestration by native plants on the green roofs followed the order of L. vicaryi > L. spicata > N. auriculata. The whole green roof had a mean carbon storage of 18.28 kg C m⁻² and average carbon sequestration of 6.47 kg C m⁻² yr⁻¹ in the combined biomass and substrate organic matter. The best green roof configuration was L. vicaryi together with MSSS substrate, with a middle-high level of carbon sequestration. It will be feasible and worthwhile to scale-up the adaptable green roof configurations in Chengdu World Modern Garden City.     

Biosynthesis of ethyl caproate and other short ethyl esters catalyzed by cutinase in organic solvent

The main objective of this work was to study the enzymatic synthesis of short chain ethyl esters, a group of relevant aroma molecules, by Fusarium solani pisi cutinase in an organic solvent media (iso-octane), and to assess the influence of different parameters on the reaction yield.Cutinase displayed high initial esterification rates in iso-octane, which amounted to 1.15 μmol min⁻¹ mg⁻¹ for ethyl butyrate (C₄ acid chain) and 1.06 μmol min⁻¹ mg⁻¹ for ethyl valerate (C₅ acid chain). High product yields, 84% for ethyl butyrate and 96% for ethyl valerate, were observed after 6 h of reaction, for an initial equimolar concentration of substrates (0.1 M).The highest product yield (97%) was observed for ethyl caproate (C₆) synthesis, a compound which is a part of natural apple and pineapple flavour, for an alcohol:acid molar ratio of 2 (0.2 M ethanol concentration).Cutinase affinity for short chain length carboxylic acids (C₄–C₆) in ester synthesis in iso-octane confirmed previous observations in reversed micellar system.     

Behavioral thermoregulation and critical thermal limits of giant keyhole limpet Megathura crenulata (Sowerby 1825) (Mollusca; Vetigastropoda)

The thermoregulatory behavior of the giant keyhole limpet Megathura crenulata was determined in a horizontal thermal gradient during the day at 18.9 °C and 18.3 °C for the night. The final preferendum determined for giant keyhole limpets was of 18.6±1.2 °C.Limpets' displacement velocity was 10.0±3.9 cm h⁻¹ during the light phase and 8.4±1.6 cm h⁻¹ during the dark phase. The thermotolerance (measured as CTMax at 50%) was determined in a keyhole limpet in three acclimation temperatures 17, 20, and 23 °C. Limpets were subjected to water increasing temperatures at a rate of 1 °C every 30 min, until they detached from the substrate. The critical thermal maximum at 50% was 27.2, 27.9 and 28.3 °C respectively.     

Potential of dendrochronology in assessing carbon sequestration rates of Vitellaria paradoxa in southern Mali,West Africa

This study aimed to investigate the applicability of dendrochronology for assessing the growth dynamics and response to climate variability and to estimate the aboveground carbon stock and carbon sequestration potential of Vitellaria paradoxa in southern Mali. Twenty stem disks were collected from three land-use types (parklands, fallows and protected areas) in Koutiala and Yanfolila districts. We combined a standard dendrochronological approach with biomass allometric equations to estimate the growth and carbon stocks. The results showed that V. paradoxa forms distinct growth ring boundaries but most of the disks from parklands did not successfully cross-date due to management operations like pruning. The tree-ring width showed a significant standardized coefficient of regression with rainfall (r² = 0.66, p < 0.001) but insignificant correlation with temperature. One-way analysis of variance showed no significant difference (p > 0.05) for C-sequestration as well as for carbon stocks in aboveground biomass for both land-use types and sites. Mean values of the amount of C-sequestered in Yanfolila were 0.112 ± 0.0.065 Mg C ha⁻¹ yr⁻¹ in parklands, 0.075 ± 0.018 Mg C ha⁻¹ yr⁻¹ in fallows and 0.064 ± 0.028 Mg C ha⁻¹ yr⁻¹ in protected areas. In Koutiala, the values were 0.068±0.020 Mg C ha⁻¹ yr⁻¹ in the parklands and 0.053 ± 0.017 Mg C ha⁻¹ yr⁻¹ in the fallows. These results clearly indicate that dendrochronology can be applied to assess growth and carbon sequestration potential of V. paradoxa. These results also suggest that climate change could affect the growth and carbon sequestration potential of V. paradoxa. Given the limited size of our sample, figures on the amount of carbon are indicative calling for applying the tested approaches to larger samples and also to other tree species in West Africa.     

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.     

Flavobacterium circumlabens sp. nov. and Flavobacterium cupreum sp. nov., two psychrotrophic species isolated from Antarctic environmental samples

A taxonomic study of 24 Gram-stain-negative rod-shaped bacteria originating from the Antarctic environment is described. Phylogenetic analysis using 16S rRNA gene sequencing differentiated isolated strains into two groups belonging to the genus Flavobacterium. Group I (n = 20) was closest to Flavobacterium aquidurense WB 1.1-56^T (98.3% 16S rRNA gene sequence similarity) while group II (n = 4) showed Flavobacterium hydatis DSM 2063^T as its nearest neighbour (98.5–98.9% 16S rRNA gene sequence similarity). Despite high 16S rRNA gene sequence similarity, these two groups represented two distinct novel species as shown by phenotypic traits and low genomic relatedness assessed by rep-PCR fingerprinting, DNA-DNA hybridization and whole-genome sequencing. Common to representative strains of both groups were the presence of major menaquinone MK-6 and sym-homospermidine as the major polyamine. Common major fatty acids were C_15:0 iso, C_15:1 iso G, C_15:0 iso 3-OH, C_17:0 iso 3OH and Summed Feature 3 (C_16:1 ω7c/C_16:1 ω6c). Strain CCM 8828^T (group I) contained phosphatidylethanolamine, three unidentified lipids lacking a functional group, three unidentified aminolipids and single unidentified glycolipid in the polar lipid profile. Strain CCM 8825^T (group II) contained phosphatidylethanolamine, eight unidentified lipids lacking a functional group, three unidentified aminolipids and two unidentified glycolipids in the polar lipid profile. These characteristics corresponded to characteristics of the genus Flavobacterium. The obtained results showed that the analysed strains represent novel species of the genus Flavobacterium, for which the names Flavobacterium circumlabens sp. nov. (type strain CCM 8828^T = P5626^T = LMG 30617^T) and Flavobacterium cupreum sp. nov. (type strain CCM 8825^T = P2683^T = LMG 30614^T) are proposed.     

Pantoea endophytica sp. nov., novel endophytic bacteria isolated from maize planting in different geographic regions of northern China

Four endophytic bacterial strains were isolated from root, stem and leaf of maize planted in different regions of northern China. The four strains possessed almost identical 16S rRNA gene sequences. However, REP-PCR fingerprint patterns discriminated that they were not from one clonal origin. Furthermore, the average nucleotide identity (ANI) values among them were higher than 95%, suggesting they all belong to one species. Based on 16S rRNA gene phylogeny, the four strains were clustered together with Pantoea rodasii LMG 26273^T and Pantoea rwandensis LMG 26275^T, but on a separate branch. Multilocus sequence analysis (MLSA) indicated that the four strains form a novel Pantoea species. Authenticity of the novel species was confirmed by ANI comparisons between strain 596^T and its closest relatives, since obtained values were considerably below the proposed thresholds for the species delineation. The genome size of 596^T was 5.1Mbp, comprising 4896 predicted genes with DNA G + C content of 57.8 mol%. The respiratory quinone was ubiquinone-8 (Q-8) and the polar lipid profile consisted of phosphatidylethanolamin, diphosphatidylglycerol, phosphatidylglycerol, unidentified aminophospholipid and unidentified phospholipid. The major fatty acids of strain 596^T were C_16:0, summed feature 2 (C_12:0 aldehyde), summed feature 3 (C_16:1ω7c and/or C_16:1ω6c) and summed feature 8 (C_18:1ω7c and/or C_18:1ω6c). Based on phylogenetic, genomic, phenotypic and chemotaxonomic data, the four isolates are considered to represent a novel species of the genus Pantoea, for which the name Pantoea endophytica sp. nov., is proposed, with 596^T (= DSM 100,785^T = CGMCC 1.15280^T) as type strain.     

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.     

Product-controlled steady-state kinetics between cytochrome aa3 from Rhodobacter sphaeroides and equine ferrocytochrome c analyzed by a novel spectrophotometric approach

Cytochrome c oxidase (CcO) catalyzes the reduction of molecular oxygen to water using ferrocytochrome c (cyt c^2 +) as the electron donor. In this study, the oxidation of horse cyt c^2 + by CcO from Rhodobacter sphaeroides, was monitored using stopped-flow spectrophotometry. A novel analytic procedure was applied in which the spectra were deconvoluted into the reduced and oxidized forms of cyt c by a least-squares fitting method, yielding the reaction rates at various concentrations of cyt c^2 + and cyt c^3 +. This allowed an analysis of the effects of cyt c^3 + on the steady-state kinetics between CcO and cyt c^2 +. The results show that cyt c^3 + exhibits product inhibition by two mechanisms: competition with cyt c^2 + at the catalytic site and, in addition, an interaction at a second site which further modulates the reaction of cyt c^2 + at the catalytic site. These results are generally consistent with previous reports, indicating the reliability of the new procedure. We also find that a 6 × His-tag at the C-terminus of the subunit II of CcO affects the binding of cyt c at both sites. The approach presented here should be generally useful in spectrophotometric studies of complex enzyme kinetics. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).