Shading Responses of the Seagrass Halophila Ovalis (R. Br.) Hook. F. From Teluk Kemang, Negri Sembilan, Malaysia

The seagrass Halophila ovalis from Teluk Kemang coast (2 ° 30'N, 101 ° 45'E) in Port Dickson, Negeri Sembilan was studied to elucidate its responses towards artificial shading. Responses were firstly based on autotrophic productivity of H. ovalis through photosynthesis experiments to determine the effects of prior acclimation to the condition of either in the field (naturally growing) or in cultures (light reduced to 85-90% of ambient conditions). Results showed that the light compensation values in field and cultured leaves (8-13 μmol m-2 s-1) were similar while saturation point was in the range of 268-275 μmol m-2 s-1 for field leaves and increased to 290-293 μmol m-2 s-1 for cultured leaves. A one-month long artificially imposed shading was then performed to plants in the field (50%, 65%, 80% and 95% shading relative to field light intensity) and in cultures (92% shading – Tank 1, and 96% shading – Tank 2, relative to field light intensity) and compared to unshaded plants as a control showed the following responses. Photosynthetic rates of field H. ovalis at two tide levels as determined using the Biological Oxygen Demand bottle method was up to six times higher when compared to the oxygen electrode method. Leaf chlorophyll content was significantly higher from plants under shading for both field and cultured leaves compared to control where leaves from cultures (Tank 2) showed the highest value in leaf chlorophyll content (1353.40 + 74.00 μg chlorophyll a g-1, p < 0.01, and 11.92 + 0.59 μg chlorophyll a cm-2, p < 0.01, by leaf fresh weight and leaf surface area respectively, and 744.30 + 46.55 chlorophyll b g-1 , p < 0.01 and 6.56 + 0.39 μg chlorophyll b cm-2 , p < 0.01, by leaf fresh weight and leaf surface area respectively). For carbohydrates, starch and the reducing sugars of glucose, sucrose, fructose and maltose were tested for in the below-ground portions of field plants, and above-ground and belowground portions of cultured plants. Starch was not detected in both aboveground and below-ground plant portions of both field and culture studies. Glucose content was highest among the four sugars, in both field and culture plants but not significantly different compared to the control. Changes in growth rates were the most discernible where increased shading results in decreased growth rates (3.72 + 0.51 mm apex-1 day-1 from control plants, to the significantly lowest recorded growth rate value of 0.746 + 0.205 mm apex-1 day-1, p < 0.01, from Tank 1 plants). Leaf morphology based on leaf length, leaf width, leaf petiole length, number of cross veins per leaf, leaf fresh weight and leaf surface area were significantly higher for leaves under shading in culture condition compared to field-shaded leaves and the control. This is substantiated by the data from Tank 2 where leaf length is 24.73 + 0.54 mm, leaf width – 9.38 + 0.23, leaf length-width ratio – 2.80 + 0.030, leaf petiole length – 28.48 + 1.03, leaf cross vein number – 14.47 + 0.27, leaf fresh weight – 0.0179 + 0.00134 and leaf surface area – 2.011 + 0.126) compared to the unshaded control (leaf length: 13.20 + 0.54 mm; leaf width: 6.81 + 0.29; leaf length-width ratio: 1.93 + 0.037; leaf petiole length: 11.20 + 1.43; leaf cross vein number: 11.40 + 0.35; leaf fresh weight: 0.00680 + 0.000548; and leaf surface area: 0.796 + 0.0744). For field biomass values, there were no significant differences between shaded plants and the control. Comparatively, culture biomass values of Tank 1 were significantly higher for both above-ground biomass (0.0127 + 0.00238 g DW rhizome-1, p < 0.01) and below-ground biomass (0.0282 + 0.00245 g DW rhizome-1, p < 0.01) compared to the unshaded control (0.0107 + 0.000914 g DW rhizome-1 and 0.0192 + 0.00109 g DW rhizome-1 for above-ground and below-ground biomass respectively). All the observations and results collated showed H. ovalis tolerates extreme low light conditions as low as 96% shading (80 μmol m-2 s-1) by modifying its various physical and biochemical characteristics accordingly with its light environment. This is also evident that the plant survives and continues to maintain productivity with respect to photosynthesis and carbohydrate production even under the highest shading levels imposed in both field (95% shading) and cultures (Tank 2 – 96% shading). Furthermore, it is possible to culture H. ovalis, although maximum growth densities equivalent to those observed in the field were not achieved. The findings suggest that lowered light availability may not be the sole causal factor for H. ovalis loss in a particular area. Other aspects such as epiphytic fouling and available nutrients could be more important in the loss of H. ovalis vegetation, although an interaction of the factor of reduced light and these other factors should not be discounted

Carbon storage and preservation in seagrass meadows

Seagrass meadows are important ‘Blue Carbon’ sinks but many questions remain unaddressed in regards to the organic carbon (OC) sequestration capacity and processes leading to retention and persistence of OC in seagrass sediments. The research summarised in this dissertation examined 37 sediment cores from twelve Australian seagrass meadows (Posidonia australis and Halophila ovalis) in order to improve our understanding of OC storage and preservation in seagrass sediments. The research: quantified the OC storage in seagrass meadows and the reduction in stores after ecosystem degradation; the rates of OC accumulation; the roles of species composition and the depositional nature of the habitat as factors affecting OC storage; and, characterised the sedimentary organic matter (OM) accumulated over millennia using techniques not previously applied to seagrass sediments. In Oyster Harbour, Western Australia, P. australis had been present over the past 6000 years, as evidenced from radiocarbon analysis of sedimentary matter. Both seagrass- and nonseagrass-derived OM contributed to high sedimentary organic stores (10.79-11.42 kg OC m- 2; 150 cm sediment depth). The persistence of sedimentary OM over millennial scales indicated that the carbon was well-preserved, thus showing a link between carbon storage and its preservation. By quantifying accumulation rates, and using historical accounts of the highest areal cover (6.1 to 6.7 km2) and recent losses in cover (by 2.8-3.1 km2) due to eutrophication, it was estimated that up to 11.17 Gg OC has been lost from shallow sediments (50 cm depth) following seagrass loss. This carbon was potentially remineralisable and may, therefore, have been liberated back to the atmospheric CO2 pool. Nine Posidonia australis meadows were then investigated for the effect of the depositional environment on sedimentary OC stores. Based on hydrodynamic differences of meadows categorised as More Sheltered, Less Sheltered, and Exposed, the More Sheltered sites had OC stores 6-fold higher (4.57 ± 0.16 to 13.51 ± 0.53 kg OC m-2; 140 cm sediment depth) compared to Exposed meadows (2.24 ± 0.31 to 3.77 ± 0.85 kg OC m-2). The OC stores of Less Sheltered meadows were not significantly different to either of the other two categories. It was concluded that the depositional nature of a seagrass habitat can affect the OC stores, though the affects may be influenced by other site-specific characteristics. The effect of species composition on OC stores and accumulation rates was subsequently investigated by comparing the stores in estuarine P. australis and H. ovalis meadows. Comparisons were based on stratigraphic- (OC stores over a set depth) and temporal-based (i.e. accumulation over a set period of time, and as accumulation rates) measures. Organic carbon stores were between 2- (P. australis: 10.81 ± 2.06 kg OC m-2, H. ovalis: 5.17 ± 2.16 kg OC m-2; 150 cm depth) and 11-fold (P. australis: 10.87 ± 2.86 kg OC m-2, H. ovalis: 0.97 ± 0.47 kg OC m-2; 2500 yr accumulation) different between meadows of the two species. While the OC stores were different between species, it was also apparent that environmental factors also contributed to the variability, with some H. ovalis meadows having stores comparable to some P. australis meadows. Thus, both the species and environmental factors needs to be considered for robust predictions of OC storage in seagrass meadows. The final study reported here investigated the preservation of sedimentary OC in the P. australis meadow of Oyster Harbour. A range of biogeochemical variables (age, sediment grain size, anoxia, OM and OC contents, and _13C values) were characterised at increasing depth within a sediment core. Solid-state 13C nuclear magnetic resonance was applied to a seagrass core for the first time to characterise the biochemical constituents of the sedimentary OM. There was a 76-80% contribution of seagrass-derived organics (lignin, carbohydrate, and a black-carbon-like OM) into the sediment. The proportion of black-carbon-like material increased with age/depth, indicating that it underwent selective preservation. Carbohydrates decreased with depth/age and lignin showed no changes, indicating that they have undergone non-selective preservation. There was remarkable consistency in the biochemical makeup of the OM with depth, which accumulated over the past 1900 years, indicating a very high preservation potential within seagrass sediments. Cumulatively, the research presented in this dissertation has highlighted the variability of OC stores in seagrass meadows and how OC may be preserved. The research has indicated that any attempts to estimate regional or global carbon stores must take into account both the species of seagrass that dominate the meadows and the type of depositional environment that the meadows occur in. It is also clear that Posidonia meadows in south-western Australia have the potential to store very large amount of Blue Carbon, comparable in some instances to the highest stores recorded globally, and to preserve these stores over millennia. Modelling future Blue Carbon stores requires an understanding of the fate of the stored carbon following disturbance. It is clear that this carbon can be lost from the meadow, but much of it appears to be in highly recalcitrant forms and it is unclear whether this material is available for subsequent re-mineralisation

Organic chemistry insights for the exceptional soil carbon storage of the seagrass Posidonia australis

The high organic carbon (OC) stores in seagrass meadows have led to their recognition as significant Blue Carbon sinks, though the diagenetic conditions that enable OC retention in seagrass soils remain poorly understood. In this study, seagrass soils were sampled from a Posidonia australis meadow in Oyster Harbour (Albany; south-western Australia) to investigate the preservation of sedimentary OC. We analysed soil characteristics (colour, grain size and redox potential), radiocarbon age, and characterised the soil organic matter (OM) using solid state CP/MAS 13C NMR spectroscopy to examine the preservation of OM down the soil profile. There was minimal change in organic composition over 1,700 years of accumulation, indicating long-term OM preservation. Primarily, this preservation appears to be driven by the recalcitrance of seagrass detritus buried in anoxic soils. The majority (70–83%) of total sedimentary OM comprised components directly attributable to seagrass origins (lignin, carbohydrate and black carbon-like matter), while the remainder consisted mostly of protein, some of which may have been present in seagrass biomass, along with likely contributions from algae and microbes. Although black carbon originates from organic matter combustion, here we provide evidence that the 13C NMR signal identified as black carbon-like matter in our soils is possibly associated with seagrass-derived organic matter consisting of degraded lignin products or other non-pyrogenic aromatics. The increase in the relative abundance of this black carbon-like matter with aging suggests its selective preservation. The relative abundances of carbohydrates significantly decreased with age down core (i.e. they appeared to be selectively decomposed), while lignin and protein did not show any quantitative changes in relative abundance (non-selective preservation). These findings demonstrate the exceptional preservation of P. australis derived OC, which contributes to our understanding of the higher OC storage capacity of Posidonia compared to other seagrass species. © 2020 Elsevier Lt

Photosynthetic light responses of wild and cultured Halophila ovalis

A laboratory based experiment was performed on leaves of the seagrass Halophila ovalis to elucidate its photosynthesis versus irradiance (P-I) relationships. Plant samples were sourced from a low water level seabed off the Teluk Kemang coast (2° 30′N, 101° 45′E) in Negeri Sembilan, Malaysia. Plants growing naturally from this area as well as those transplanted into indoor culture tanks were studied. The oxygen evolution responses of the leaves based on parameters of leaf fresh weight (FW), leaf surface area (Area) and leaf chlorophyll content (Chl) towards varying degrees of illumination were recorded. A comparison between leaves from cultures with those from the wild showed that the curve plotted for its respective values was lowered for the former based on FW and Area but comparatively lowered based on Chl. The light compensation (Ic,) value did not vary much between leaves from the wild and leaves from the cultures (8-13 μmol m-2 s-1) while light saturation point (Ik) was in the range of 268 - 275 μmol m-2 s-1 for leaves from the wild and increased to 290 - 293 μmol m-2 s-1 for leaves from cultures. Dark respiration values did not differ between wild and cultured leaves based on the measurements calculated from the parameters stated (FW, Area and Chl). Calculations based on FW and Area showed a higher light saturation (Pmax) photosynthetic rate for cultured leaves but comparatively lowered based on Chl. Pmax values between leaves from culture to that from the wild based on the parameters of FW and Area were significantly different (p<0.05) but not based on Chl while the trends of curves fitted between wild and cultured leaves were significantly different based on Area only (p<0.05). The results collated in this study serve to add to the present knowledge of biological traits of H. ovalis from Malaysia to further understand its importance in local waters

Spatial and temporal distribution dataset of benthic macroalgae during the 2015-2016 tropical monsoonal cycle in Malaysia

The effects of small-scale disturbances, such as monsoon, are understudied in tropical regions. The storms associated with monsoon events not only modify the local macroalgal community structure, but also reveal the continuation of short-term recolonisation. Thus, this study aims to determine the variation in species, assemblage and cover of macroalgae during the monsoonal cycle from 2015 to 2016. This paper presents data on the spatial and temporal distribution of benthic macroalgae along the coastline of Johor, Malaysia. The information is presented as raw and partially-processed data, which summarises the cover and frequency of macroalgae at the respective study sites. This paper describes an important set of data that can be used further for in-situ experiments on the effects of environmental disturbances towards pioneer and climax species in tropical areas.This study provides a description of the east coast shore of Peninsular Malaysia, specifically in Johor coast in 2015-2016. The spatial and temporal distribution and abundance of a total of 41 taxa were assessed at four monsoon-exposed locations. These data provide a comprehensive baseline against disturbance and recolonisation of macroalgal community can be effectively and objectively evaluated

Carbon stock and ?13C data of sediment samples collected from a tropical seagrass meadow in Malaysia

Seagrass ecosystems are considered as major blue carbon sinks, thus contributing directly to the mitigation of climate change by storing carbon in their habitats. However, empirical data for carbon stocks in Malaysia seagrass meadow sediment remain unreported in a standardised format. This paper presents data on organic (OC) and inorganic carbon (IC) stocks, and stable isotope signatures of carbon (?13C) in bulk seagrass sediments collected from Sungai Pulai estuary (Johor, Malaysia). Within this estuary, seagrasses form shoals at Tanjung Adang and Merambong. Organic carbon and ?13C values in bulk sediment were analysed by an elemental analyser and a continuous flow isotope-ratio mass spectrometer, respectively, while sediment IC data was derived from loss-on-ignition calculations of sample mass differences. The data from these samples are presented as downcore profile of OC (values range at 0.14% to 2.49%), IC (0.16% to 5.29%), ?13C values of organic matter (-27.9‰ to -20.4‰), and cumulative carbon stocks (1.03-3.39 kg OC m-2 and 0.76-2.84 kg IC m-2) in the top 30 cm of sediments. This dataset is applicable for regional and local blue carbon studies, which would allow insights into carbon sink and carbon cycling capacity, in addition to gaining insights into the provenances of carbon stored in seagrass meadows

B-spline curve interpolation model by using intuitionistic fuzzy approach

In this paper, B-spline curve interpolation model by using intuitionistic fuzzy set approach is introduced. Firstly, intuitionistic fuzzy control point relation is defined based on the intuitionistic fuzzy concept. Later, the intuitionistic fuzzy control point relation is blended with B-spline basis function. Through interpolation method, intuitionistic fuzzy B-spline curve model is visualized. Finally, some numerical examples and an algorithm to generate the desired curve is shown

B-spline curve interpolation model by using intuitionistic fuzzy approach

In this paper, B-spline curve interpolation model by using intuitionistic fuzzy set approach is introduced. Firstly, intuitionistic fuzzy control point relation is defined based on the intuitionistic fuzzy concept. Later, the intuitionistic fuzzy control point relation is blended with B-spline basis function. Through interpolation method, intuitionistic fuzzy B-spline curve model is visualized. Finally, some numerical examples and an algorithm to generate the desired curve is shown

Intelligent Controller Design For Multifunctional Prosthetics Hand

Prosthetics hand is replacement of original hands that lose or damage because of war, trauma, accident or congenital anomalies. However, problems often occur on a prosthetics hand when dealing with the control capabilities and devising functional. Thus, an advanced mechanical design with control approach is required to improve the performance in terms of quality control in prosthetics hand and also enhance existing capabilities to the optimum level. This paper aims to develop a functional prosthetics hand at upper limb, which will focus on position of human hand particularly using the movement of finger instructions. In this paper, an intelligent controller, Fuzzy with Proportional-Integral-Derivative (Fuzzy-PID) controller is proposed to realize accurate force control with high performance. The performance of prosthetics hand model controlled by Fuzzy-PID controller is outperform the conventional PID controller and Fuzzy controller, where the improvement of the transient response and steady state error is achieved. Performance comparison of three different controllers has been presented through these evaluation process

Key biogeochemical factors affecting soil carbon storage in Posidonia meadows

Unidad de excelencia María de Maeztu MdM-2015-0552Biotic and abiotic factors influence the accumulation of organic carbon (Corg) in seagrass ecosystems. We surveyed Posidonia sinuosa meadows growing in different water depths to assess the variability in the sources, stocks and accumulation rates of Corg. We show that over the last 500 years, P. sinuosa meadows closer to the upper limit of distribution (at 2-4m depth) accumulated 3- to 4-fold higher Corg stocks (averaging 6.3 kg Corg m¯²/ at 3- to 4-fold higher rates (12.8 gCorg m¯² yr¯¹/ compared to meadows closer to the deep limits of distribution (at 6-8m depth; 1.8 kg Corg m¯² and 3.6 g Corg m¯² yr¯¹/. In shallower meadows, Corg stocks were mostly derived from seagrass detritus (88% in average) compared to meadows closer to the deep limit of distribution (45% on average). In addition, soil accumulation rates and fine-grained sediment content (< 0.125 mm) in shallower meadows (2.0mm yr¯¹ and 9 %, respectively) were approximately 2-fold higher than in deeper meadows (1.2mm yr¯¹ and 5 %, respectively). The Corg stocks and accumulation rates accumulated over the last 500 years in bare sediments (0.6 kg Corg m¯² and 1.2 g Corg m¯² yr¯¹/ were 3- to 11-fold lower than in P. sinuosa meadows, while fine-grained sediment content (1 %) and seagrass detritus contribution to the Corg pool (20 %) were 8- and 3-fold lower than in Posidonia meadows, respectively. The patterns found support the hypothesis that Corg storage in seagrass soils is influenced by interactions of biological (e.g., meadow productivity, cover and density), chemical (e.g., recalcitrance of Corg stocks) and physical (e.g., hydrodynamic energy and soil accumulation rates) factors within the meadow. We conclude that there is a need to improve global estimates of seagrass carbon storage accounting for biogeochemical factors driving variability within habitats