Simultaneous extension of both basic microstructural components in scleractinian coral skeleton during night and daytime,visualized by in situ 86Sr pulse labeling

Using in situ (12 h) pulse-labeling of scleractinian coral aragonitic skeleton with stable ⁸⁶Sr isotope, the diel pattern of skeletal extension was investigated in the massive Porites lobata species, grown at 5 m depth in the Gulf of Eilat. Several microstructural aspects of coral biomineralization were elucidated, among which the most significant is simultaneous extension of the two basic microstructural components Rapid Accretion Deposits (RAD; also called Centers of Calcification) and Thickening Deposits (TD; also called fibers), both at night and during daytime. Increased thickness of the ⁸⁶Sr-labeled growth-front in the RADs compared to the adjacent TDs revealed that in this species RADs extend on average twice as fast as TDs. At the level of the individual corallite, skeletal extension is spatially highly heterogeneous, with sporadic slowing or cessation depending on growth directions and skeletal structure morphology. Daytime photosynthesis by symbiotic dinoflagellates is widely acknowledged to substantially increase calcification rates at the colony and the corallite level in reef-building corals. However, in our study, the average night-time extension rate (visualized in three successive 12 h pulses) was similar to the average daytime extension (visualized in the initial 12 h pulse), in all growth directions and skeletal structures. This research provides a platform for further investigations into the temporal calibration of coral skeletal extension via cyclic growth increment deposition, which is a hallmark of coral biomineralization.     

Testing the first phase of the ‘gardening concept’ as an applicable tool in restoring denuded reefs in Tanzania

Studies on coral reef restoration through a two-step coral gardening protocol have lately proved it to be a viable solution for future reef restoration. This involves a first step of gardening small colonies in mid-water nurseries and a second step, their transplantation, upon reaching suitable size, onto the pre-surveyed damaged areas. We established in September 2007 two mid-water nurseries, each holding 10,000 fragments measuring 2 cm average initial size, at 4 m depths (high tide) in Zanzibar and Mafia Islands, Tanzania. Each nursery comprised six species, each of which was represented by three genotypes. During 9 months, we followed developments by analyzing and comparing survivorship and growth rates of fragments between the different nurseries, species and genotypes. A significant difference between species survival and growth rates was observed in acroporid species, in Pocillopora verrucosa and Millepora sp., which showed better success than Porites cylindrica. In both sites, Millepora suffered no mortality and other species exhibited low mortality, ranging (per coral genotype) between 3% and 24% in Zanzibar (most cases below 10%) and between 13% and 44% (mostly below 25%) in Mafia Island. Most of fragments’ mortality occurred during the first two nursery months. Coral species in Zanzibar nursery also performed better in growth rates than those in Mafia, but in both sites, farmed corals were ready for transplantation just 9 months after the nursery was set up. Economic evaluations involved in the overall nursery set-up and the results indicated that the coral gardening approach could be used in Tanzania to generate large quantities of coral colonies for the restoration of damaged reefs at relatively low cost.     

Tarbellastraea (Scleractinia): A new stable isotope archive for Late Miocene paleoenvironments in the Mediterranean

Geochemical proxy records of sea surface temperature (SST) or sea surface salinity (SSS) variability on intra- and interannual time-scales in corals from geological periods older than Pleistocene are extremely rare due to pervasive diagenetic alteration of coralline aragonite. Very recently, however, stable isotope data (δ¹⁸O, δ¹³C) from specimens of Porites of Late Miocene age (10 Ma) have been shown to preserve original environmental signatures. In this paper we describe new finds of the zooxanthellate corals Porites and Tarbellastraea in exceptional aragonite preservation from the island of Crete in sediments of Tortonian (～ 9 Ma) and Early Messinian (～ 7 Ma) age. Systematic, comparative stable isotope analysis of massive Tarbellastraea and Porites sampled from the same beds and localities reveal identical stable isotope fractionation patterns in both genera. Therefore, extinct Tarbellastraea represents an additional environmental archive fully compatible and mutually exchangeable with Porites. Provided that seasonal variations in δ¹⁸O reflect SST changes only, seasonal SST contrasts of 7.3 °C for the Tortonian and 4.8 °C for the Early Messinian are inferred, implying warmer summer and cooler winter SSTs during the Tortonian than during the Messinian. However, reduced δ¹⁸O seasonality (1.1‰ in the Tortonian and 0.7‰ in the Messinian) and slightly less negative mean δ¹⁸O in Messinian corals (? 2.4‰) compared to Tortonian specimens (? 2.7‰) may not necessarily indicate a long-term fall in SSTs, but changes in surface water δ¹⁸O, i.e. global ice build-up or enhanced evaporation during summer or increased precipitation/river discharge during winter and changes in insolation. On the other hand, coral communities of Tortonian and Messinian age in central Crete are identical, and compatible annual extension rates indicate similar average SSTs during the two investigated time periods. In addition, lithological and paleobotanical data from Central Crete document a change from humid to dry climatic conditions during the Late Miocene. Therefore, a likely explanation for the observed shift in coral mean δ¹⁸O and reduced δ¹⁸O seasonality from the Tortonian to the Early Messinian is a change in ambient seawater δ¹⁸O caused by a change in the hydrological balance towards high evaporation/high salinity during summer.     

New approach for determination of an optimum honeybee colony’s carrying capacity based on productivity and nectar secretion potential of bee forage species

The present study was carried out to determine an optimum honeybee colony’s carrying capacity of selected valleys dominated by Ziziphus spina-christi and Acacia tortilis in the Al-Baha region, Kingdom of Saudi Arabia. The study was conducted based on the assessment of the number of colonies kept, their productivities and the existing productive bee forage resources in the target valleys with its economic implication. In the existing beekeeping practice, the average number of managed honeybee colonies introduced per square kilometer was 530 and 317 during the flowering period of Z. spina-christi and A. tortilis, respectively. Furthermore, the overall ratios of productive bee forage plants to the number of honeybee colonies introduced were 0.55 and 11.12 to Ziziphus trees and A. tortilis shrubs respectively. In the existing situation the average honey production potential of 5.21 and 0.34 kg was recorded per Ziziphus and A. tortilis plants per flowering season, respectively. The present study, revealed that the number of honeybee colonies introduced in relation to the existing bee forage potential was extremely overcrowding which is beyond the carrying capacity of bee forage resources in selected valleys and it has been observed to affect the productivities and subsequent profitability of beekeeping. The study infers that, by keeping the optimum honeybee colony’s carrying capacity of valleys (88 traditional hives/km² or 54 Langstroth hives/km² in Ziziphus field and 72 traditional hives/km² or 44 Langstroth hives/km² in A. tortilis field), profitability of beekeeping can be boosted up to 130.39% and 207.98% during Z. spina-christi and A. tortilis, flowering seasons, respectively.     

Environmental factors controlling colony formation in blooms of the cyanobacteria Microcystis spp. in Lake Taihu,China

Nitrogen (N) and phosphorus (P) over-enrichment has accelerated eutrophication and promoted cyanobacterial blooms worldwide. The colonial bloom-forming cyanobacterial genus Microcystis is covered by sheaths which can protect cells from zooplankton grazing, viral or bacterial attack and other potential negative environmental factors. This provides a competitive advantage over other phytoplankton species. However, the mechanism of Microcystis colony formation is not clear. Here we report the influence of N, P and pH on Microcystis growth and colony formation in field simulation experiments in Lake Taihu (China). N addition to lake water maintained Microcystis colony size, promoted growth of total phytoplankton, and increased Microcystis proportion as part of total phytoplankton biomass. Increases in P did not promote growth but led to smaller colonies, and had no significant impact on the proportion of Microcystis in the community. N and P addition together promoted phytoplankton growth much more than only adding N. TN and TP concentrations lower than about TN 7.75–13.95 mg L⁻¹ and TP 0.41–0.74 mg L⁻¹ mainly promoted the growth of large Microcystis colonies, but higher concentrations than this promoted the formation of single cells. There was a strong inverse relationship between pH and colony size in the N&P treatments suggesting CO₂ limitation may have induced colonies to become smaller. It appears that Microcystis colony formation is an adaptation to provide the organisms adverse conditions such as nutrient deficiencies or CO₂ limitation induced by increased pH level associated with rapidly proliferating blooms.     

A novel method for exploring elemental composition of microbial communities: Laser ablation-inductively coupled plasma-mass spectrometry of intact bacterial colonies

Bacterial colonies are spatially complex structures whose physiology is profoundly dependent on interactions between cells and with the underlying semi-solid substratum. Here, we use bacterial colonies as a model of a microbial community to evaluate the potential of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to delineate elemental distributions within colonies with minimal pre-treatment. To reduce water content of the colony and limit undesirable absorption of laser energy, we compared methods of preparing 24 h-old colonies of Escherichia coli TG1 on agar for laser ablation. Colonies on excised agar segments dried on chromatography paper were superior to colonies dried in a dessicator or by prolonged incubation, with respect to signal magnitude, signal:noise ratio and background signal. Having optimised laser scan speed (10 μm s^− 1) and laser beam diameter (100 μm), further improvements were achieved by growing colonies on nylon membranes over agar, which were then transferred to the ablation chamber without further treatment. Repeated line rasters across individual membrane-supported colonies yielded three-dimensional elemental maps of colonies, revealing a convex morphology consistent with visual inspection. By normalising isotope counts for P, Mn, Zn, Fe and Ca against Mg, the most abundant cellular divalent cation, we sought elemental heterogeneity within the colony. The normalised concentration of Mn in the perimeter was higher than in the colony interior, whereas the converse was true for Ca. LA-ICP-MS is a novel and powerful method for probing elemental composition and organisation within microbial communities and should find numerous applications in, for example, biofilm studies.     

Caractérisation de la production particulaire par l’oursin Echinometra mathaei sur les récifs Indo-Pacifiques : influence des peuplements coralliens et implications sur la dynamique sédimentaire

The characteristics of the sedimentary grains produced by the sea urchin Echinometra mathaei were described from two reef sites: a fringing Acropora-dominated reef at La Reunion island (Indian Ocean) and a barrier Porites-dominated reef at Moorea island (French Polynesia). The composition of the sediment produced by Echinometra was determined from SEM observations. The size and shape of the particles were measured by using image analysis method. The grain diameters range between a few micrometres and 2 mm, with a large predominance (more than 80 %) of particles smaller than 400 μm. The grain size distribution is dependent on the nature of the grazed substratum. Echinometra individuals collected at La Reunion on branching Acropora colonies produce a higher proportion of particles smaller than 200 μm compared to those collected at Moorea on massive Porites colonies. At Moorea, more grains having a diameter comprised between 200 and 500 μm are produced. The microstructure of coral substrata affects the mean particle diameter, which is 192,17 μm for a Acropora substratum and 244,69 μm for a Porites substratum. Since the sediment derived from Acropora erosion is finer, the proportion of suspended material that is exported from the reef is greater at La Reunion than at Moorea. We estimate that, for similar erosion rates and hydrodynamic conditions, the production of sands by Echinometra mathaei is higher and the retention of this erosional sediment more effective on reefs dominated by massive Porites than on Acropora-dominated reefs. This result is in accordance with the proportions of suspension-moving grains that have been previously measured on Moorea and La Reunion reefs. This study highlighted the effect of coral communities on the production of particles related to the bioerosion and on the sedimentary budget.     

Density and distribution of seeds in bottom sediments in Zostera marina beds in Ago Bay,central Japan

The density of Zostera marina L. seeds in bottom sediments was examined to study the reproductive patterns of the Z. marina population in Ago Bay, Mie Prefecture, central Japan.Seeds and seed coats were numerous in Tategami, where the annual type of Z. marina grows. In contrast, seeds were scarce in Hamajima, where the perennial type of Z. marina grows. Bottom sediment was sampled with sediment cores at Tategami in November 2004 and March 2005 to examine density and depth distribution of the seeds. Seeds were found as deep as 8 cm, but no deeper. On the other hand, empty seed coats were found as deep as 16 cm in both months. In the upper layers of the sediment to a depth of 8 cm, the average number of seed coats was 7960 ± 2997 m⁻² in November and 16,318 ± 2922 m⁻² in March. Deeper than 8 cm, the number of seed coats gradually decreased owing to decomposition, and none was found below 16 cm. We used the density of reproductive shoots and number of seeds per spadix in Tategami to estimate the fate of seeds and seed coats of the annual type of Z. marina in bottom sediments: out of the 6000 seeds m⁻² produced annually, 72% disappears from the stand and 28% is buried locally. The density and distribution of Z. marina seeds are among the most important factors in maintenance and propagation of the annual population at Tategami.     

Growth responses of Zostera capricorni to estuarine sediment conditions

This study comprised (1) a field survey of intertidal seagrass (Zostera capricorni) biomass, cover and photosynthetic potential and sediment characteristics at a range of contrasting sites in three New Zealand harbours, and (2) a microcosm experiment comparing plant responses to sediments from extant versus historical seagrass sites. The field survey showed that the sediment physico-chemical characteristics were generally consistent with the limited previous reports for Zostera environments, although the total P concentration range was higher (0.08–0.72 mg P g⁻¹). Overall, 52% of variation in seagrass cover was explained by sediment water content (R = 0.54) and organic content (R = −0.56). Twenty-two percent of variation in seagrass biomass was explained by sediment total P and redox potential (both R = −0.35). Intra-harbour seagrass–sediment relationships were more significant (explaining up to 82% of plant variation) but harbour-specific. In the microcosm experiment, threefold higher Z. capricorni biomass was maintained on extant than historical sediments but not conclusively linked to measure sediment characteristics. Overall, the results of this study demonstrate that significant relations can exist between estuarine sediment conditions and Z. capricorni growth responses, and suggest that detrimental change in sediment conditions may be a contributing factor in seagrass decline.     

Biodegradation of Tapis blended crude oil in marine sediment by a consortium of symbiotic bacteria

Biodegradation rate and the high molecular weight hydrocarbons are among the important concerns for bioremediation of crude oil. Inoculation of a non-oil-degrading bacterium as supplementary bacteria increased oil biodegradation from 57.1% to 63.0% after 10 days of incubation. Both the oil-degrading bacteria and the non-oil-degrading bacteria were isolated from Malaysian marine environment. Based on the 16S rDNA sequences, the oil-degrading bacteria was identified as Pseudomonas pseudoalcaligenes (99% similarity) while the non-oil-degrading bacterium was Erythrobacter citreus (99% similarity). E. citreus does not grow on crude oil enriched medium under present experimental condition but it withstands 5000 mg kg^?1 Tapis blended crude oil in sediment. Under optimal condition, the oil-degrading bacterium; P. pseudoalcaligenes, alone utilized 583.3 ± 3.8 mg kg^?1 (57.1%) at the rate of 3.97 × 10^?10 mg kg^?1 cell^?1 day^?1 Tapis blended crude oil from 1000 mg kg^?1 oil-contaminated sediment. Inoculation of E. citreus as the supplementary bacteria to P. pseudoalcaligenes enhanced biodegradation. The bacterial consortium degraded 675.8 ± 18.5 mg kg^?1 (63.0%) Tapis blended crude oil from the 1000 mg kg^?1 oil-contaminated sediment. Biodegradation rate of the bacterial consortium increased significantly to 4.59 × 10^?10 mg kg^?1 cell^?1 day^?1 (p = 0.02). Improvement of the oil degradation by the bacterial consortium was due to the synergetic reaction among the bacterial inoculants. There are two implications: (1) E. citreus may have a role in removing self-growth-inhibiting compounds of P. pseudoalcaligens. (2) P. pseudoalcaligenes degraded Tapis blended crude oil while E. citreus competes for the partially degraded hydrocarbons by P. pseudoalcaligenes. P. pseudoalcaligenes forced to breakdown more hydrocarbons to sustain its metabolic requirement. The bacterial consortium degraded 78.7% of (C₁₂–C₃₄) total aliphatic hydrocarbons (TAHs) and 74.1% of the 16 USEPA prioritized polycyclic aromatic hydrocarbons.     

Alternative alert system for Ganga river eutrophication using alkaline phosphatase as a level determinant

Short-term variations in phosphorus (P) concentrations must be considered while assessing the long-term changes in trophic status and estimating the P load and export. Furthermore, given the challenges of conventional monitoring of river systems, a sediment-specific biomonitoring tool may be more successful inferring P related human controls. In this study, conducted along a 37 km river channel representing up-and downstream urban control, and through a trajectory from a major point source (Assi drain), we tested the patterns of concordance between alkaline phosphatase (AP) activity and soluble reactive-P (SRP) and between AP activity and trophic status in the Ganga River. To validate data comparison, we selected a reference site at Dev Prayag, situated ∼1130 km upstream to the main study stretch. Samples were collected for three consecutive year (March 2013 to February 2016) with respect to atmospheric deposition, surface runoff, point source loading, river water and sediment analysis. For trajectory analysis, samples were collected from 15 locations starting from the drain outlet (zero distance) upto 1.5 km downstream with sampling location 100 m away from the preceding one. We found marked spatial and temporal variations in P concentrations which could be traced by quantifying the AP activity. The AP activity, recorded highest at reference site, declined with increases in P; and at drain mouth it was close to zero reflecting strong influence of P level on alkaline phosphatase activity in the river. We used canonical correlation analysis (CCorA) to test the degrees of concordance and similarity in different variables. Most of the environmental variables and indicators of eutrophy appear largely clustered at one side of the coordinate separating AP activity and dissolved oxygen towards opposite side of the axis. The dynamic fit function relating AP activity with different variables showed significant positive correlation with DO (R² = 0.67; p < 0.001) and negative correlations with BOD (R² = 0.82; p < 0.001), Chl a biomass (R² = 0.52; p < 0.001) and trophic status index (R² = 0.54 (Chl a), 0.96 (DRP); p < 0.001). Furthermore, the enzyme activity did not show significant negative correlation with heavy metals in sediment. Because anthropogenic activities continue to enhance P loads; AP is inhibited directly by P availability; and eutrophy feedbacks sediment P release, our observations on P-AP activity relationship provide a valuable alternative means for detecting P related controls on water quality, trophic status and biogeochemical feedbacks in human impacted rivers.     

Growth responses of Zostera capricorni to estuarine sediment conditions

This study comprised (1) a field survey of intertidal seagrass (Zostera capricorni) biomass, cover and photosynthetic potential and sediment characteristics at a range of contrasting sites in three New Zealand harbours, and (2) a microcosm experiment comparing plant responses to sediments from extant versus historical seagrass sites. The field survey showed that the sediment physico-chemical characteristics were generally consistent with the limited previous reports for Zostera environments, although the total P concentration range was higher (0.08–0.72 mg P g⁻¹). Overall, 52% of variation in seagrass cover was explained by sediment water content (R = 0.54) and organic content (R = −0.56). Twenty-two percent of variation in seagrass biomass was explained by sediment total P and redox potential (both R = −0.35). Intra-harbour seagrass–sediment relationships were more significant (explaining up to 82% of plant variation) but harbour-specific. In the microcosm experiment, threefold higher Z. capricorni biomass was maintained on extant than historical sediments but not conclusively linked to measure sediment characteristics. Overall, the results of this study demonstrate that significant relations can exist between estuarine sediment conditions and Z. capricorni growth responses, and suggest that detrimental change in sediment conditions may be a contributing factor in seagrass decline.     

Factors influencing the return of submerged plants to a clear-water,shallow temperate lake

Lack of submerged vegetation was studied in a small, shallow, alkaline, clear-water lake with high nitrate concentration (mean 9 mg NO₃–N L⁻¹) and profuse filamentous green algae (FGA) (mainly Spirogyra sp.). A laboratory microcosm and two lake enclosure experiments were carried out using Elodea nuttallii (Planchon) St John. E. nuttallii grew about 1.7 times as well in sediment from its place of origin compared with sediment from the lake. Differential water quality had no effect, and neither sediment nor water prevented growth in the lake. Nutrient addition reduced plant growth by more than 55% because of shading from epiphytic filamentous green algae (shoot dry weight versus epiphytic algal dry weight, r = −0.491, P < 0.05). Transplanted Elodea plants grew better in enclosures in the lake than in laboratory conditions with lake water and sediment (P < 0.001, t-test). Rare Elodea individuals in the lake indicate the presence of plant propagules in the lake sediment, but excessive growth of filamentous green algae (summer mean 3.2 g dry weight m⁻²) significantly hamperd plant growth (shoot length reduced from 29 ± S.E.M. 1 to 25 ± 1 cm) and bird herbivory significantly reduced survival (from 82 ± 7 to 40 ± 6%) and shoot growth (from 78 ± 6 to 18 ± 5 cm) and thus eliminates establishment of even modest plant beds. Fish disturbance and sediment stability were not important. Restoration of submerged plants may require reduction of nitrate input, control of filamentous green algae and protection from birds.     

Alexandrium pacificum Litaker sp. nov (Group IV): Resting cyst distribution and toxin profile of vegetative cells in Bizerte Lagoon (Tunisia,Southern Mediterranean Sea)

A high spatial resolution sampling of Alexandrium pacificum cysts, along with sediment characteristics (% H₂O, % organic matter (OM), granulometry), vegetative cell abundance and environmental factors were investigated at 123 study stations in Bizerte Lagoon (Tunisia). Morphological examination and ribotyping of cells obtained from a culture called ABZ1 obtained from a cyst isolated in lagoon sediment confirmed that the species was A. pacificum. The toxin profile from the ABZ1 culture harvested during exponential growth phase was simple and composed of the N-sulfocarbamoyl toxins C1 (9.82 pg toxin cell⁻¹), the GTX6 (3.26 pg toxin cell⁻¹) and the carbamoyl toxin Neo-STX (0.38 pg toxin cell⁻¹). The latter represented only 2.8% of the total toxins in this strain.High abundance of A. pacificum cysts correlated with enhanced percentages of water and organic matter in the sediment. In addition, sediment fractions of less than 63 μm were examined as a favorable potential seedbed for initiation of future blooms and outbreaks of A. pacificum in the lagoon. A significant difference in the cyst distribution pattern was recorded among the lagoon's different zones, with the higher cyst abundance occurring in the inner waters. Also, no correlation due to the specific hydrodynamics of the lagoon was observed in the spatial distribution of A. pacificum cysts and vegetative cells.     

Short-time response in root morphology of Vallisneria natans to sediment type and water-column nutrient

Rooted submerged macrophytes can absorb significant amounts of nutrients from both sediment and water. We investigated root morphology of Vallisneria natans in mesocosm plastic bins, in response to three types of sediment (sandy loam, clay, and a 50:50 (v/v) mixture of the two sediments) and two levels of water-column nutrient (well water and nutrient medium). Compared to the plants grown in the clay or mixed sediments, root diameter decreased (0.39–0.41 versus 0.36–0.37 mm) but total root length per plant increased (0.87–1.27 versus 1.14–1.62 m) when grown in sandy loam. Increase of nutrient availability in water column led to decreased specific root length (306–339 versus 258–281 m g⁻¹). However, both sediment type and water-column nutrient had no impacts on root number (ranged from 19 to 24 number of roots per plant). Root weight ratio, root:leaf mass ratio and root:leaf length ratio generally decreased with enhanced nutrient availability in sediment or water. Plant growth was affected by sediment type alone (P < 0.05), rather than water-column nutrient (P > 0.05). However, plant N and P contents were significantly impacted by both sediment type (P ≤ 0.001) and water-column nutrient (P < 0.05). Increase of nutrient availability in sediment or water led to increased plant N (ranged from 2.47 to 4.77 mg g⁻¹) and P concentrations (ranged from 42.8 to 62.0 mg g⁻¹). These results indicate that considerable variation in root morphology of V. natans exists in response to the fertility of the sediment it is rooted in.     

Towards an optimal sampling strategy for Alexandrium catenella (Dinophyceae) benthic resting cysts

The study proposes methodological developments to optimize sampling strategy of resting cysts of Alexandrium catenella to estimate their abundance with a predefined error. This work also aims to provide information on spatial distribution of resting cysts in sediments. The distribution mode of A. catenella resting cysts related to the abundance variability was studied through sediment cores sampling on four different spatial scales and using Ludox CLX gradient density method. The quantification method underestimates by a factor of 2 the resting cysts abundance in one gram of sediment. Application of Taylor's power law allowed us to define a compromise between sampling effort and abundance estimation error. In the case of A. catenella resting cysts from Thau lagoon, the optimal sampling strategy consists of sampling 10 stations on a surface of 2 km² for a given coefficient of variability (C) of 15%, sampling 3 sediment cores at each station (C = 30%) and counting only one replicate by core (C = 18%). Results related to the application of Taylor's power law are closely dependent on resting cyst density and aggregation in a given sediment. In our area, A. catenella resting cysts are mainly observed in the upper 3 cm of sediment. Horizontally, their heterogeneity is lower on 10 cm² surface and tends to stabilize itself beyond a surface of 10 m². Each author has to carry out this pre-sampling effort for his own resting cysts-forming species, in his own area, in order to increase accuracy of resting cyst mapping.     

Copulation duration of bumblebee Bombus terrestris (Hymenoptera: Apidae): Impacts on polyandry and colony parameters

The influence of copulation duration on mating frequency and colony development were studied in Bombus terrestris (Hymenoptera: Apidae). Copulation time was recorded in transparent plastic boxes and was manipulated by separating mating pairs. Mean copulation duration was found to be 30.0 ± 8.0 (mean ± se) minutes and most matings lasted 20 to 40 min. When queens were only allowed to mate for 2 to 5 min, the chance that they would accept a second mating was 7.2 ± 5.0 % (mean ± se). Incompletely mated queens delayed to initiate colonies but they did not show significant difference from fully mated queens in production of new queens and males. This study shows that colony development was not affected by short copulation duration.     

Effect of different cell sheet ECM microenvironment on the formation of vascular network

The repair and reconstruction of large bone defects remains as a significant clinical challenge mainly due to the insufficient vascularization. The prefabrication of vascular network based on cell sheet technique brings a promising potential for sufficient vascularization due to rich extracellular matrix (ECM) of cell sheets. However, the effect of different cell sheet ECM micro-environment on the formation of a vascular network has not been well understood. Here our goal is to study the effect of different cell sheets on the formation of a vascular network. First we cultured human bone marrow mesenchymal stem cells (hBMSCs) under two culture conditions to obtain osteogenic differentiated cell sheet (ODCS) and undifferentiated cell sheet (UDCS), respectively. Then the human umbilical vein endothelial cells (HUVECs) were seeded onto the surface of the two sheets at different seeding densities to fabricate pre-vascularized cell sheets. Our results indicated that the two sheets facilitated the alignment of HUVECs and promoted the formation of vascular networks. Quantitative analysis showed that the number of networks in ODCS was higher than that in the UDCS. The ECM of the two sheets was remodeled and rearranged during the tubulogenesis process. Furthermore, results showed that the optimal seeding density of HUVECs was 5 × 10⁴ cell/cm². In summary, these results suggest that the vascularized ODCS has a promising potential to construct pre-vascularized tissue for bone repair.     

Effects of phosphorus and nitrogen amendments on the growth of Egeria najas

The effect of nutrient addition on the growth of E. najas was evaluated in a dose response experiment using sand amended with phosphorus (P) and nitrogen (N), and in enrichment trials with N and P amendments to natural sediments. Plants, water and sediment came from lagoons of the Upper Paraná River Floodplain and from Itaipu Reservoir (Brazil). Relative growth rates (RGRs) of E. najas shoots, based on dry mass (DM), varied from 0.03 to 0.060 d⁻¹ for both nutrients. Root:shoot biomass ratios were related to sediment exchangeable P (r = −0.419; P = 0.03) and N (r = −0.54; P = 0.006), however root RGR was not related to sediment nutrient concentrations. When natural sediments were amended with N and P, neither shoot nor root RGRs differed among treatments for substrata from either the reservoir or the floodplain lagoons (P > 0.05). Comparison of nutrient concentrations measured in natural sediments collected from several sites in both the Upper Paraná River Floodplain (range 49–213 μg P g⁻¹ DM; 36–373 μg N g⁻¹ DM) and Itaipu Reservoir (range 43–402 μg P g⁻¹ DM; 7.9–238 μg N g⁻¹ DM) showed that sediment N and P from these systems usually exceeded minimum requirements necessary for E. najas growth, as measured in the dose response experiment. Together, these results indicate that E. najas, at least in early stages of development, responds to sediment nutrient amendments and relies upon bottom sediments to meet its N and P requirements and that for at least two Brazilian ecosystems, growth of this species is not limited by insufficient sediment N or P. Thus, reducing N and P in water is not enough to control E. najas growth in short time periods in these ecosystems.     

Extent estimates and land cover relationships for functional indicators in non-wadeable rivers

Functional indicators are being increasingly used to assess waterway health but their responses to pressure in non-wadeable rivers have not been widely documented or applied in modern survey designs that provide unbiased estimates of extent. This study tests the response of river metabolism and loss in cotton strip tensile strength across a land use pressure gradient in non-wadeable rivers of northern New Zealand, and reports extent estimates for river metabolism and decomposition rates. Following adjustment for probability of selection, ecosystem respiration (ER) and gross primary production (GPP) for the target population of order 5–7 non-wadeable rivers averaged −7.3 and 4.8 g O₂ m⁻² d⁻¹, respectively, with average P/R < 1 indicating dominance by heterotrophic processes. Ecosystem respiration was <−3.3 g O₂ m⁻² d⁻¹ for 75% of non-wadeable river length with around 20% of length between −10 and −20 g O₂ m⁻² d⁻¹. Cumulative distribution functions of cotton strength loss estimates indicated a more-or-less linear relationship with river km reflecting an even spread of decay rates (range in k 0.0007–0.2875 d⁻¹) across non-wadeable rivers regionally. A non-linear relationship with land cover was detected for GPP which was typically <5 g O₂ m⁻² d⁻¹ where natural vegetation cover was below 20% and greater than 80% of upstream catchment area. For cotton strength loss, the relationship with land cover was wedge-shaped such that sites with >60% natural cover had low decay rates (<0.02 d⁻¹) with variability below this increasing as natural cover declined. Using published criteria for assessing waterway health based on ER and GPP, 232–298 km (20–29%) of non-wadeable river length was considered to have severely impaired ecosystem functioning, and 436–530 km (42–50%) had no evidence of impact on river metabolism.