Development of chemosynthetic microbial communities in organic falls deployed in the deep Southwest Atlantic Ocean

ABSTRACTThe assembly and successional processes of microbial communities inhabiting deep-sea whale and wood falls are highly complex and vastly unknown, as a myriad of factors may affect the development of a chemosynthetic-based ecosystem on these organic islands. The chemoautotrophy supported by organic substrates is the basis of long-lasting ecosystems, considered biodiversity hotspots in the oligotrophic deep sea. Understanding how these microbial communities develop and the factors affecting them could shed light on processes related to the maintenance of biodiversity in this environment. We performed a whale- and wood-fall experiment in the southwest Atlantic on the Brazilian continental margin and investigated biofilm-forming bacterial and archaeal communities colonising these substrates, deployed at 1500 and 3300 m depth. The composition of the prokaryotic communities shared some similarities with previously reported organic falls in the north Pacific and the Mediterranean Sea, mainly regarding sulphur oxidising chemolithotrophic taxa from the phyla Campylobacterota and Proteobacteria. Communities were found to be highly different between the organic substrates, as whale fall associated biofilms presented a higher dominance of sulphur oxidising chemolithotrophs. We also observed a significant difference between the two sites, with the whale associated communities at the 1500 isobath presenting a faster establishment of the chemosynthetic taxa.

A study on the hydrodynamic performance of manta ray biomimetic glider under unconstrained six-DOF motion

A manta ray biomimetic glider is designed and studied with both laboratory experiments and numerical simulations with a new dynamic update method called the motion-based zonal mesh update method (MBZMU method) to reveal its hydrodynamic performance. Regarding the experimental study, an ejection gliding experiment is conducted for qualitative verification, and a hydrostatic free-fall experiment is conducted to quantitatively verify the reliability of the corresponding numerical simulation. Regarding the numerical simulation, to reduce the trend of nose-up movement and to obtain a long lasting and stable gliding motion, a series of cases with the center of mass offset forward by different distances and different initial angles of attack have been calculated. The results show that the glider will show the optimal gliding performance when the center of mass is 20mm in front of the center of geometry and the initial attack angle range lies between A0 = -5° to A0 = -2.5° at the same time. The optimal gliding distance can reach six times its body length under these circumstances. Furthermore, the stability of the glider is explained from the perspective of Blended-Wing-Body (BWB) configuration.

Potential use of fresh mulch to curb potato late blight epidemics in Brazil

ABSTRACT Field experiments were conducted during spring 2014 and fall and spring 2015 to determine the effect of fresh mulch on the development of Phytophthora infestans epidemics, in Lapa Municipality, Parana State, southern Brazil. The used cultivars were ‘Agata’, susceptible, and ‘BRS Ana’, moderately susceptible. The main treatment consisted in manually applying a 10cm-thick layer of fresh mulch when potato sprouts were emerging. Fresh mulch was prepared with plants available at that time of the year. For the spring experiments, fresh mulch was a mixture of oats, rye grass and wild radish (60 t/ha) and for the fall experiment, semi-ripe elephant grass (90 t/ha). Plots consisted of six 10m-long rows, spaced at 0.8m, containing 28 plants per row. Experimental design was in completely randomized blocks with four replicates. Natural inoculum was adopted. Percentage of leaf area was weekly estimated until the end of the plant cycle and the area under the disease progress curve (AUDPC) was calculated. Application of fresh mulch significantly reduced AUDPC by 32.1%, 12.4% and 23.1%, compared to control in all seasons, for ‘BRS Ana’ and by 26.1%, 2.8% and 12.0% for ‘Agata’. Application of fresh mulch showed to be a promising practice for the integrated management of late blight and for the protection of yields, especially in periods more favorable to the development of the disease. More detailed studies should be conducted on the plant type and amount of fresh mulch to be used, as well as on the possibility of reducing concentrations or increasing intervals between fungicide sprays.

Pycnogonids (Arthropoda, Pycnogonida) from the Southwest Indian Ridge

This report addresses sixty-two deep-sea pycnogonid specimens collected by the Southwest Indian Ocean Seamounts Expedition, November 7 to December 21, 2011 on-board the British research vessel R.S.S. James Cook (voyage numbers JC066, JC067). Pycnogonids were collected from four of six geological features sampled along the central section of the Southwest Indian Ridge (SWIR) in an area approximately 1500 km south-south east of Madagascar. Specimens were mostly gathered utilizing a remotely operated vehicle (ROV) and tethered video-sediment grab platforms. Additional specimens were gathered from sediment cores or hand-picked from whale bone and wood-fall experiment nets and mooring buoy ropes. Fifteen new species are described, illustrated and compared with their nearest relatives. Two previously described species belonging to the genera Colossendeis and Austrodecus are recorded. A specimen of Austrodecus bamberi represents the first record of the female and is the only species in the collection previously known from the SWIR. One species of Colossendeis remains unnamed pending further analysis. One subadult specimen of Sericosura showing strong morphological affinity with a specimen previously recorded from the Walvis Ridge remains undescribed pending availability of further material. One subadult specimen is tentatively assigned to Nymphon. Specimens are assigned to six families and eight genera. Colossendeis rostrata is synonymised with C. melancholicus. The methodology of counting palp segments in the genera Austrodecus and Rhynchothorax is reviewed.

Organic Mulch Effects on High Tunnel Lettuce in Southern New England

Lettuce (Lactuca sativa L.) is a popular crop for spring and fall high tunnels among direct-market vegetable producers. Common practices include the use of compost as a soil amendment, and reliance on cultivation for weed control. This study examined the impacts of using compost as a surface mulch to control weeds in spring and fall romaine lettuce, with data collected on soil temperature, weed suppression, and lettuce yields. Costs of all inputs, including labor, were tracked to assess economic feasibility of using mulch. Compost mulch was compared with bare ground with cultivation across four cultivars of romaine lettuce: Ridgeline, Coastal Star, Green Forest, and Shushan. In the fall experiment, mulching increased average soil temperature by 1 °C and canopy cover, leaf area index (LAI), and fresh and dry weights were significantly higher in mulched plots. Mulching decreased daily variation in soil temperature in the spring experiment but had no effect on average soil temperature. Canopy cover, LAI, and fresh and dry weights were not significantly affected by mulching in the spring experiment. Compost mulch affected all cultivars similarly in both experiments, with no significant interaction effects. Yields were greater and leaves were larger in the spring experiment than in the fall for all cultivars. Fresh weight yields in the spring experiment averaged 3.22 kg·m−2 and heads had a LAI of 7.9 as compared with 1.02 kg·m−2 and 1.6 for the fall experiment. Dry matter content (DMC) was significantly higher in the fall lettuce (113 g·kg−1) than in the spring lettuce (43 g·kg−1). Cultivar rank order was consistent across experiments, with ‘Ridgeline’ having the best performance and ‘Green Forest’ the worst. ‘Coastal Star’ and ‘Shoshone’ were intermediate and very similar to each other. Although the use of compost as a mulch increased yields of all cultivars in the fall experiment, only the top cultivar, Ridgeline, produced enough additional yield to offset the increased costs of the compost mulch used in this study. The use of a less-expensive compost or a higher retail price for romaine lettuce would have made the economics more favorable for the other cultivars.

Suppression of nutrient release from freshwater lake sediments using granulated coal ash

In order to investigate the applicability of granulated coal ash (GCA), a by-product of coal thermal power stations, to freshwater lakes, two incubation experiments (fall and summer experiments) were conducted using large-volume vessels and sediments taken from eutrophic lakes. The phosphorus and nitrogen release fluxes in the vessels with GCA (up to 2.9 mg m−2 d−1 for total phosphorus and 23.9 mg m−2 d−1 for total nitrogen) were considerably smaller than those in the vessels without GCA (up to 8.9 mg m−2 d−1 and 56 mg m−2 d−1, respectively), except in the case of phosphorus in the fall experiment, and thus the phosphorus concentration released from the vessel without GCA under anoxic conditions in the summer experiment was extraordinarily higher (over 1.5 mg l−1) than those in the other vessels (less than 0.31 mg l−1). Supplementary experiments with smaller columns indicated that the chemical effect of GCA was on a similar level with its physical effect and that the threshold phosphorus concentration for removing it was lower in freshwater than seawater. The chromium level slightly exceeded the standard for drinking water and the development of technology to suppress its release is a future challenge.

PENENTUAN PERCEPATAN GRAVITASI PADA PERCOBAAN GERAK JATUH BEBAS DENGAN MEMANFAATKAN RANGKAIAN RELAI

The determination of the gravity acceleration through free fall experiment using the relay circuit has been done. This study aims to make free-fall experiment design using relay circuit, and determine the value of gravity acceleration by using this experiment design. The measurement method used in this study is to measure the free fall time of the object using a stopwatch that can work automatically. The result of this research is this experiment design can be used to get the free fall time data automatically. The values of gravity acceleration to 10 cm, 20 cm, 30 cm, 40 cm and 50 cm respectively, are 9.80952381 m/s2, 9.814058957 m/s2, 9.845 m/s2, 9.858283385 m/s2, and 9.829645226 m/s2. So that the average acceleration value of the five variations of height is 9.831302275 m/s2. Keywords: Free fall motion, gravity acceleration, relay circuit.