جستجوی مقالات مرتبط با کلیدواژه « مانگرو » در نشریات گروه « زیست شناسی »

Coastal-marine wetlands consisting of mangrove forests, sandy beaches, and mudflats are among the sensitive and important habitats of the southern coasts of Iran, which play an important role in the economy and livelihood of local communities. The International Mangrove Wetland of Shur, Shirin, and Minab Rivers is one of the important coastal wetlands of Iran, and due to facing many threats, it needs new and effective protection planning. This research has been conducted to investigate the significant changes in the levels of mangrove forests as an indicator species of the wetland, identify and prioritize the factors that threaten the biodiversity of the wetland, and provide Participatory management solutions. The calculation of mangrove level changes was done based on the time series analysis method of OLI (Operational Land Imager) sensor data from Landsat 8. The planning and implementation of participatory protection in this research included reviewing the current situation, identifying stakeholders, and holding participatory meetings to identify and prioritize threats and formulate an action plan for cooperative wetland protection. The results showed that from 2015 to 2022, mangrove forests have been destroyed in some areas by 30.78 hectares. According to the survey of the participants and stakeholder’s beneficiaries, two threats of pollution caused by the dumping of smuggled fuel and illegal fishing activities have the highest priority among the total of 15 threats identified in the wetland. In this research, for the ten important threats prioritized by the opinion of the participants, an action plan to reduce the effects of threats, including the mechanism of the threat effect, the effect on the indicator species, the economic and social effects, and the priority plan to reduce the effects of each threat has been developed. The results of this research are used in raising awareness and preparing educational content for community-based conservation programs with the participation of stakeholders, including the implementation of participatory wetland conservation and restoration projects.

Advances in remote sensing enable fast mangrove mapping the less need for intensive fieldwork, complex and heavy processing, and skill-based classification techniques. In this research, mangrove forest mapping was performed using Sentinel-2 satellite images in Google Earth Engine (GEE) in Hormozgan province in three ecosystems of Qeshm, Khamir, and Sirik. For this purpose, all steps of mapping these forests, including pre-processing and classification were performed in the GEE. The Modular Mangrove Recognition Index (MMRI) and classic spectral indices were also used to highlight the spectral differentiation of mangrove cover from the surroundings. To classify the image of the study area, three land cover classes were used: mangrove, non-mangrove, and sea (water). The classification was performed based on the random forest algorithm and accuracy assessment was evaluated in R software based on the K-fold validation method. The Qeshm site was demonstrated the highest accuracy among the three ecosystems with an overall accuracy of 98% and a kappa of 0.73. Khamir and Sirik sites were shown an overall accuracy of 97% and a kappa value of 0.71 and 0.70, respectively. The MMRI index was the most important variable in the RF classification in Qeshm and Khamir, while in Sirik, the SAVI index was the most important spectral index in mangrove map providing. The overall accuracy of over 95% at all three sites indicates that combining Sentinel-2 data using appropriate indices in the GEE is an effective approach to mangrove forest mapping

Marine plants are good source of natural antioxidant compounds. Mangroves are a group of salt-tolerant marine plants of intertidal areas with numerous medicinal properties. In the present study, phytochemical analysis (steroids, alkaloids, phenols, flavonoids and tannins) and antioxidant properties (total phenolic content, DPPH free radical scavenging activity, reduction power and metal chelating activity) of methanolic extract of leaves, stem bark, and roots of mangrove species Avicennia marina was investigated. The mangrove samples were collected from the shores of Gwater Bay in the southeast of Sistan and Baluchestan province. Phytochemical analysis showed that all the tested compounds were present in the extract of mangrove leaves, except alkaloids. While in the stem bark extract, only phenolic compounds, flavonoids and tannins were observed and alkaloids and steroids were not detected. Alkaloids, phenols and flavonoids were discovered in the root extract. The assessment of the antioxidant properties showed that among different parts of mangroves, the highest amount of phenol (6.28 mg gallic acid/ g extract), free radical scavenging (59.18 %) and iron ion reduction power (absorbance at 700 nm: 0.37) was found in the leaves extract. Contrary to these two indicators, the highest amount of iron chelating activity (absorbance at 562 nm: 0.84) was found in mangrove root extract. The results of this research showed that different parts of the mangrove plant, especially its leaves, can be considered as a potential source of natural antioxidants.

Mangroves are the most efficient coastal environments for carbon sequestration, which can play an effective role in modification of increasing greenhouse gases. In this study, for the first time, the carbon storage in soils and mangrove trees in mangrove forest of Govatr Bay were evaluated. The amount of sediment carbon in sediment cores was determined as well as the diameter on breast height and height of trees were measured in 12 stations in Bahu and Govatr Estuaries. Satellite imagery showed that the total area of the Govatr Bay mangrove forest is 450 ha, 67% of which is high density forest. The amount of soil carbon in the region fluctuates between 1.9 to 3.8%, which is in the range of the global average (2.2%). The average carbon content of the top 1m of Govatr Bay is 393 tons per hectare (t ha-1), which is 30% higher than the global average. The total amount of carbon in top 1m of Govatr mangrove soil was estimated at 177,000 tons, 70% of which is sequestered in Bahu Estuary mangroves. The total amount of soil carbon in Govatr and Bahu Estuaries is 121600 and 210500 tons, respectively. A total of 64,100 tons of carbon is stored in the mangrove trees of Govatr Bay, 64% of which are related to the Bahu Estuary. A total of 376,000 tonnes of carbon (equivalent to 1,378,000 tonnes of carbon dioxide) has been stabilized in the Govatr forest, only 11% of which is stored in trees. Estimates show that if the Govatr are completely deforested, more than 279,000 tons of carbon dioxide will re-mineralize into the atmosphere.

The aim of this study was to isolate and identify a-amylase-producing bacteria present in mangrove ecosystems on Qeshm Island, Hormozgan, Iran. Samples of mangrove leaves and roots were screened for a-amylase activity using Lugol’s solution. Crude extracts were prepared of positive samples, and their a-amylase activity was determined by the Bernfeld method. The two strains with the highest activity were identified by molecular analysis of their 16S rRNA genes. a-Amylase production and activity were optimized by varying temperature and pH. 46 bacterial strains were isolated from mangrove tree leaf and root samples. Of these, 28 strains were capable of producing a-amylase. 16S rRNA gene sequence analysis of two strains with the highest enzyme production identified them as Bacillus sp. strain HR10 and Bacillus sp. strain HR11. The optimum temperature for enzyme production was 35 and 30 °C for strains HR10 and HR11, respectively, and the optimum pH was pH 8 for both strains. The highest enzyme activity was observed at 70 °C and 60 °C for the HR10 and HR11 strains, respectively, and the optimum pH was pH 8 for both strains. In conclusion, we have shown that bacteria isolated from mangrove leaf and root samples are potential source of a-amylases, tolerating a wide range of temperature and pH. Such a-amylases may be of interest for use in environmentally friendly industries.

The study of biomass and carbon in mangrove forests is often performed by allometry methods. The allometry models in Mangrove trees are influenced by factors such as species, ecological conditions, and tree age. To study the allometry equation of hara shrub (Avicennia marina) in the Nayband Bay, a complete shrub of Hara from the mentioned area was picked up at 6 stations, and biometry, biomass, and carbon content of the samples were measured. According to the results, the best model for estimating the biomass in mangrove shrubs in Nayband is the power equation using a stem diameter at 30 cm height (ABG = 139.3d301.263). The ratio of the root to the top part (leaf and trunk) is 24%. According to the content of carbon in the biomass samples, the amount of carbon was 42% of the upper part biomass and 39% of the root biomass. The obtained allometry equation in this study is different from mature Avicennia marina in different parts of the world and Iran.

Generally, determination of degree of coastal area environmental sensitivity is a prerequisite for assessing vulnerability of sensitive ecosystems in these areas, especially mangroves, and plays an important role in the efficiency and success of their recovery and sustainable management programs. Therefore, the aim of this study was also to determine the degree and prioritization of environmental sensitivity of mangroves of Hormozgan province. To this end, using set of criteria developed by the Marine Environment Bureau and review of studies on sensitivity of mangroves, a list of the most important criteria and sub-criteria for the sensitivity of these ecosystems was provided and the relative weight of the criteria was calculated by analyzing the opinions of experts through the implementation of the FAHP method. The results showed that according to expert's opinion, among the nine criteria for determining the degree of sensitivity of mangroves, vegetation cover and recreational significance criteria obtained the highest and lowest relative weight among the considered criteria, respectively (with relative weights equal to 0.23 and 0.03, respectively). The results also showed that the vegetation cover, wildlife and food network criteria with relative weights of 0.23, 0.17 and 0.13, were the most important sensitivity criteria of mangroves in the final rankings. The results of this study by prioritizing the environmental sensitivity criteria of mangroves of Hormozgan province, provides essential information for assessing the vulnerability of these habitats.

In general, fishing activities are considered as one of the most important environmental disturbances in increasing the vulnerability of the mangrove ecosystems due to their destructive effects on the process of sedimentation and wave currents, decreasing biodiversity, and introducing oil pollutants into these ecosystems. Therefore, investigating and mapping the intensity of fishing activities in mangrove habitats are of great needs in conducting the vulnerability assessment and providing managerial solutions and empowerment of these ecosystems to minimize and compensate the damages caused by environmental hazards. The aim of this study was to investigate, determine, and delineate and the intensity of fishing activities in the mangrove habitats of the Hormozgan province. To this end, the map of intensity of fishing activities was prepared in Khamir, Qeshm, Tiab, Sirik and Jask habitats through mapping the mangrove habitats, drawing 598 cell networks of 4 × 4 km in the coastal waters and the available geospatial data, and number of vessels in the fishing ports of the Hormozgan province. The results showed that in terms of the geographic distribution and the number of vessels in the fishing ports of the Hormozgan province, the intensity of the fishing activities in the mangrove habitats is ranked as follows: Khamir habitat> Qeshm habitat> Tiab habitat> Jask habitat> Sirik habitat. The results of this study can be used as a prerequisite for assessing the vulnerability of the mangroves of Iran.

In this study, the leaf extract activity of two species of mangrove plants, Avicennia marina (Avicenniaceae family) and Rhizophora mucronata (Rhizophoraceae) was compared in biosynthesis of silver nanoparticles (AgNPs). The AgNPs were investigated using spectrophotometry, transmission electron microscopy (TEM), scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). Absorption spectrum in 420 nm confirmed the synthesis of AgNPs. The evaluation of the recorded TEM images from silver nanoparticles showed that the size of nanoparticles synthesized by A. marina was in the range of 0 to 75 nm and the size of nanoparticles synthesized by R. mucronata was in the range of 0 to 80 nm. The results of FE-SEM image analysis showed nanoparticles with a size between 15 to 43 and 10 to 19 nm for A. marina and R.mucronata, respectively. The results of EDS indicated the presence of 51.6% and 73.5% silver in nanoparticles synthesized by A. marina and R. mucronata, respectively. Results suggest that the leaf extracts of both mangrove species are able to reduce the Ag+ into Ag0 in the solution of AgNO3 at room temperature and synthesize silver nanoparticles of very suitable nanometric dimensions.