Role of vegetated coastal ecosystems as nitrogen and phosphorous filters and sinks in the coasts of Saudi Arabia

Vegetated coastal ecosystems along the Red Sea and Arabian Gulf coasts of Saudi Arabia thrive in an extremely arid and oligotrophic environment, with high seawater temperatures and salinity. Mangrove, seagrass and saltmarsh ecosystems have been shown to act as efficient sinks of sediment organic carbon, earning these vegetated ecosystems the moniker \u27blue carbon\u27 ecosystems. However, their role as nitrogen and phosphorus (N and P) sinks remains poorly understood. In this study, we examine the capacity of blue carbon ecosystems to trap and store nitrogen and phosphorous in their sediments in the central Red Sea and Arabian Gulf. We estimated the N and P stocks (in 0.2 m thick-sediments) and accumulation rates (for the last century based on 210Pb and for the last millennia based on 14C) in mangrove, seagrass and saltmarsh sediments from eight locations along the coast of Saudi Arabia (81 cores in total). The N and P stocks contained in the top 20 cm sediments ranged from 61 g N m-2 in Red Sea seagrass to 265 g N m-2 in the Gulf saltmarshes and from 70 g P m-2 in Red Sea seagrass meadows and mangroves to 58 g P m-2 in the Gulf saltmarshes. The short-term N and P accumulation rates ranged from 0.09 mg N cm-2 yr-1 in Red Sea seagrass to 0.38 mg N cm-2 yr-1 in Gulf mangrove, and from 0.027 mg P cm-2 yr-1 in the Gulf seagrass to 0.092 mg P cm-2 yr-1 in Red Sea mangroves. Short-term N and P accumulation rates were up to 10-fold higher than long-term accumulation rates, highlighting increasing sequestration of N and P over the past century, likely due to anthropogenic activities such as coastal development and wastewater inputs. © 2020 The Author(s). Published by IOP Publishing Ltd

Improving the productivity of acid sulfate soils for cultivation using limestone, basalt, organic fertilizer and/or their combinations

Acid sulfate soils are generally not suitable for the crop production unless they are efficiently improved. A study was conducted to improve the productivity of acid sulfate soils for rice cultivation using ground magnesium limestone (GML), basalt and organic fertilizer. The study was conducted on rice in laboratory, glasshouse and field. The pH of acid sulfate soils was low and exchangeable Al was very high which affected rice growth. The application of GML and basalt increased soil pH and reduced Al toxicity. GML required to ameliorate the soils for rice cultivation was 4 t ha-1. Basalt in combination with organic fertilizer was a good soil amendment, but required to be applied a few months ahead of rice cultivation. Due to GML or basalt application, rice plants grew well even though water pH was below 5. The highest rice yield obtained was 4.0 t ha-1 season-1 for Sulfaquepts and it was 7.5 t ha-1 season-1 for Sulfosaprists. In general, the application of GML or basalt in combination with organic fertilizer improved the productivity of acid sulfate soils and consequently enhanced rice yield

Effectiveness of different phytohormones on grain filling and yield of rice (Oryza sativa L.) under drought stress

Drought is a major limiting factor affecting rice yield and productivity all over the world, including Malaysia. To induce drought resistance, there is an increasing interest in using different phytohormones for field crop production considering its efficiency, feasibility, cost and labour-effectiveness. A greenhouse experiment was conducted to evaluate effectiveness of five different phytohormone treatments as Vita-Grow Plus (commercial phytohormones product), epibrassinolide, spermine, pyroligneous acid and without any of those or control including three times of application (single spray at 35 days after sowing, DAS; double spray at 35 and 55 DAS and triple spray at 35, 55 and 85 DAS) on growth and yield parameters of rice (Oryza sativa L.). Drought stress was exposed by regulating irrigation schedule. It was observed that all applied growth regulators have more or less progressive effect on rice growth and productivity. Both epibrassinolide and spermine application caused highest grain filling and spermine application highest (66.4%) grain yield. Considering yield components and grain yield, double spray of phytohormones was best. Therefore, two times spray (35 and 55 DAS) of spermine could be suggested for rice cultivation in the drought affected areas of Malaysia or other areas in the tropical region with similar ecologies

Arsenic management in contaminated irrigation water for rice cultivation

Arsenic (As) contaminated irrigation water (groundwater) is a threat to irrigated rice cultivation. Studies were conducted during three consecutive Boro seasons (fully dependent on irrigation) at highly As contaminated areas in Bangladesh to determine a suitable water management practice to reduce As accumulation in rice. In this study, two water management techniques were evaluated: 1) alternate wetting and drying (AWD) and continuous standing water (CSW) with surface (25 μg L-1 As); and 2) groundwater (419 μg L-1 As). A high yielding rice variety, BRRI dhan28, was grown. Results showed that the yield obtained by two management techniques were almost similar, except in CSW with groundwater application where significant yield reduction was observed. Significantly lower As content was found in the straw (77.23%) and rice grain (38.14%) of AWD with groundwater and CSW (straw 70.41% and 26.36%) with surface water application compared to CSW with ground water application. Among the water management practices, AWD with groundwater application showed similar benefit to CSW with surface water irrigation. Thus, alternate wetting and drying (AWD) with groundwater or surface water irrigation with CSW can be advocated as an appropriate agronomic practice for rice cultivated in As contaminated soils of Bangladesh

Quality and antioxidant activity of rice grown on alluvial soil amended with Zn, Cu and Mo

Insufficient micronutrients are a common phenomenon in Malaysian soils derived from riverine alluvium, which affect the growth and quality of rice. A study was conducted on such soils at Kelantan, Malaysia to evaluate the effects of applying Zn (5kgha −1 ),Cu (4kgha −1 ) and Mo (0.5kgha −1 ) along with the recommended N, P, K and S at 120, 30, 50, 10kgha −1 , respectively on rice plant growth, grain yield, quality and antioxidant activity. Any single micronutrient or in combination with macronutrients had positive effects on the growth, chlorophyll contents, grain quality, and protein content of rice. Application of micronutrients increased phenolic compound by 40% and flavonoid content by 71.54% in rice grain compared to the control, particularly, Zn and Cu had positive effects on grain protein percentage. Furthermore, the application of micronutrients increased Zn, Mo, and Cu content in grain and straw. Higher values of antioxidant activities were found in the de-husked grain compared to those of the milled rice in micronutrient applied treatments. The application of the micronutrients to the riverine alluvium soil enhanced rice yield by 18% via uptake of nutrients, attributed to increased physiological performance, leading to higher harvest index and grain quality

El impacto de las inundaciones y las tormentas de arena en el crecimiento y la supervivencia de las plántulas del manglar Avicennia marina en el sur del Mar Rojo

Mangroves occur in tropical and subtropical regions, including harsh arid areas. Little is known about how the environmental conditions of deserts influence the ecology of mangrove seedlings. The seedlings of the mangrove Avicennia marina were examined in situ in a natural stand of the southern Red Sea coast of Saudi Arabia to (1) estimate and compare the growth rate of A. marina between selected microhabitats with different tidal exposures, and (2) examine the influence of sandstorms on the growth and survival of the seedlings. Samplings were conducted in four zones established according to their tidal exposure: low tidal exposure (Z1), medium tidal exposure (Z2), high tidal exposure with numerous burrows (Z3), and high tidal exposure with a few or no burrows (Z4). Vertical growth and mortality of the seedlings and selected environmental variables were quantified. The results show that seedling growth rates differed significantly between the sampling zones, the highest growth being found in the high tidal regions (Z3 followed by Z4) and the lowest growth in Z1. Growth rate followed a significant decreasing pattern over time, coinciding with increasing air temperature and decreasing relative humidity. Sandstorms showed a marked increase in July, leading to massive dust deposition that caused extensive mortality of the seedlings by burial. Our study highlights that seedling growth can be affected by the extent of tidal inundation and that sandstorms act as a natural stressor.Los manglares proliferan en regiones tropicales y subtropicales, incluidos los desiertos. Sin embargo, se sabe poco acerca de cómo las condiciones ambientales de los desiertos influyen en la ecología de las plántulas de manglares. Las plántulas del manglar Avicennia marina se examinaron in situ en un manglar natural de la costa sur del Mar Rojo de Arabia Saudita para (1) estimar y comparar la tasa de crecimiento de A. marina entre microhábitats seleccionados con diferente exposición a las mareas, y (2) examinar la influencia de las tormentas de arena en el crecimiento y supervivencia de las plántulas. Los muestreos se realizaron en cuatro zonas establecidas en función de su exposición a las mareas: exposición a las mareas bajas (Z1), exposición a las mareas medias (Z2), exposición a las mareas altas con numerosas madrigueras de cangrejos (Z3) y exposición a las mareas altas pero con pocas o ninguna madriguera (Z4). Se cuantificó el crecimiento vertical y la mortalidad de las plántulas, así como las variables ambientales seleccionadas. Los resultados muestran que las tasas de crecimiento de las plántulas difirieron significativamente entre las zonas de muestreo con el mayor crecimiento encontrado en las regiones de marea alta (Z3 seguida de Z4) y el crecimiento más bajo en Z1. La tasa de crecimiento siguió un patrón decreciente significativo a lo largo del tiempo, que coincidió con el aumento de la temperatura del aire y la disminución de la humedad relativa. Las tormentas de arena aumentaron en julio, causando una deposición masiva de polvo que enterró a las plántulas, desencadenando una gran mortalidad. Nuestro estudio destaca que el crecimiento y la supervivencia de las plántulas pueden verse afectados por la extensión de la inundación de las mareas y las tormentas de arena, actuando como factores de estrés natural

Enhancing the fertility of an acid sulfate soil for rice cultivation using lime in combination with bio-organic fertilizer

The acid sulfate soils contain pyrite (FeS2) which is due to oxidation results in the production of high amount of acidity, aluminum and iron significantly affecting rice growth.A glasshouse study was arranged to determine the effect of ground magnesium limestone (GML) in combination with bio-organic fertilizer (JITUTM) application on the chemical properties of soils and rice yield. Three rice seedlings were transplanted in pots which were previously amended with 0, 2, 4, 6 and 8 t/ha GML with or without bio-organic fertilizer. The common rice varieties (MR 219 and MR 253) were cultivated for two seasons in the same pots. The critical Fe²⁺and Al³⁺ activities for MR 219 were 14.45 and 4.23 µM, while for MR 253 were 7.45 and 5.53 µM, respectively. However, without applying the amendments, rice grown on the soils was affected severely by the high acidity (Fe²⁺and Al³⁺toxicity). The soil pH increased to 5 and the higher grain yield of MR 219 (99.77 and 121.38 g/pot) and MR253 (98.63 and 112.60 g/pot) was in first and second season with the application of 2 t GML application combined with 0.25 t JITU−/ha respectively. In addition, 1000 grain weight, number of panicle, number of spikelets panicle⁻¹ and the percentage of filled spikelet, were also higher than without the soil amendments. Hence, the infertility of acid sulfate soils for sustainable rice cultivation in Malaysia can be improved by applying 2 t GML/ha combined with 0.25 t JITU−/ha for two seasons in long run

Effects of applying ground basalt with or without organic fertilizer on the fertility of an acid sulfate soil and growth of rice

Rice yield grown on acid sulfate soils is very low because of Al3+ and/or Fe2+ toxicity. A study was conducted to determine the effects of applying ground basalt with or without organic fertilizer on the growth of rice. Results showed clear benefits of ground basalt as an amendment for acid sulfate soil infertility. The ameliorative effects were comparable with that of applying 4 t ground magnesium limestone (GML) ha-1; however, basalt had an additional advantage over GML as it contained K and P besides Ca and Mg. But as basalt needs time to disintegrate and dissolve completely in the acid sulfate soil under submerged conditions, the best option is to apply ground basalt in combination with organic fertilizers a few months ahead of transplanting rice in the field. The organic fertilizers would then be able to partly reduce Al and/or Fe in the soil via the chelation process

Exponential increase of plastic burial in mangrove sediments as a major plastic sink

© 2020 The Authors. Sequestration of plastics in sediments is considered the ultimate sink of marine plastic pollution that would justify unexpectedly low loads found in surface waters. Here, we demonstrate that mangroves, generally supporting high sediment accretion rates, efficiently sequester plastics in their sediments. To this end, we extracted microplastics from dated sediment cores of the Red Sea and Arabian Gulf mangrove (Avicennia marina) forests along the Saudi Arabian coast. We found that microplastics \u3c0.5 mm dominated in mangrove sediments, helping explain their scarcity, in surface waters. We estimate that 50 ± 30 and 110 ± 80 metric tons of plastic may have been buried since the 1930s in mangrove sediments across the Red Sea and the Arabian Gulf, respectively. We observed an exponential increase in the plastic burial rate (8.5 ± 1.2% year-1) since the 1950s in line with the global plastic production increase, confirming mangrove sediments as long-term sinks for plastics

Occurrence of arsenic in soils, groundwater and rice plants in selected districts of Bangladesh

A study was conducted in four districts of Bangladesh, namely Faridpur sadar, Kolaroa (Satkhira), Shibaloya (Manikganj) and Natore sadar to assess arsenic (As) status in groundwater, agricultural soils, rice straw and rice grain. One hundred samples each of soil, irrigation water and plant parts (root, straw, husk and grain) were collected from the four areas for As determination. Results showed that the minimum mean of As in the soils (4 ± 0.17 ppm) and water (2 ± 1 ppb) was found in Natore Sadar, while the maximum in the soil (35 ± 16.03 ppm) and water (462 ± 28 ppb) was in Kolaroa (Satkhira). Murarikati, Keralkata, Jallabad, Jugikhali and Helatala of Kolaroa showed high As in the soils and groundwater. Similarly, high soil and water As were found in Aliabad, Kaijuri and Majchar (Faridpur) areas. The high As containing areas may be considered as arsenic hot spots. Arsenic content in the deep tube well water was also high in the Kolaroa area. In the hot spot areas, the level of As in rice straw and rice grain was significantly higher than those of the normal soil areas. It implies that increase in the level of soil and water As would result in the increase of As content in rice straw and rice grain. However, As content in the rice grain was below the permissible level for consumption. The accumulation of As followed the order of root > straw > husk > grain