Change detection of a coastal woodland mangrove forest in Fiji by integration of remote sensing with spatial mapping

Mangroves play key ecological role in structuring the availability of coastal resources. The current study was focused on change detection in a large mangrove patch located in Votua area of the Ba province in Fiji. Globally, the mangrove population continues to decline with the changes in climatic conditions and anthropo-genic activities. Baseline information through wetland maps and time series change are essential references for the development of effective mangrove management plans. These maps reveal the status of the resource over a period of time and the impacts from anthropogenic activities. Remote sensing techniques were integrated with geographic information system tools for mapping and detecting temporal change over a period of 20 years. Remotely sensed imagery data from Landsat satellite was sourced from the year 1999 to 2018 for this investigation. The mapping analysis of temporal changes in mangrove forests was carried using the versatile ArcGIS and ENVI software. The pilot change detection analysis revealed a small but important change in the mangrove patch over these years. Landward creep of mangroves was also detected. The outcomes of this study serve as baseline and conservation information for the development and implementation of effective management plans for one of Fiji’s largest mangrove patches

Benthic resource baseline mapping of Cakaunisasi and Yarawa reef ecosystem in the Ba region of Fiji

Coastal habitats form a critical source of livelihood for a large number of inhabitants in Fiji. The absence of historical and baseline information creates a significant challenge in effectively designing suitable management plans. This study aimed at developing reliable benthic cover maps of village intertidal resource harvest areas (Cakaunisasi and Yarawa reefs) and anthropogenic perceptions of Votua Village in the Ba region of Fiji for better resource management planning and monitoring. Images captured by the WorldView2 satellite were used as a base for mapping out the resources. Data logging on-site, Global Positioning System (GPS) recordings, local interviews and high-resolution video capturing were utilised for ground-truthing techniques. Six classes of benthic cover were identified, which included algae, coral, sand and gravel, buried reef, coral rubble and seagrass. Accuracy assessment and supervised classification were done using ground reference points. There was an existing marine protected area (MPA) on the Yarawa reef, which did not seem to be working as well as anticipated by observing the habitat maps of the two reefs. Baseline maps constructed here and possibly ecosystem maps can allow for monitoring of the existing MPA as well as the formation of a new and more informed MPA. The maps generated in this study serve as baseline information about resource distribution on Cakaunisasi and Yarawa reefs to inform management decisions

Evaluating antimicrobial activity and total phenolic content of commonly used herbs and spices in Fiji

Traditionally, crude extracts from various plants were used for treatment of diseases and ailments, while spices have been used for flavour, as preservatives, in rituals and as medicines for treating infectious diseases. The essential oils of 12 medicinal plants and spices were extracted and tested against Escherichia coli 0157:H7 (EHEC) to determine the antimicrobial properties. The selected plants and spices are Eugenia caryophyllata (F), Jasminium (F), Eucalyptus globulus (L), Zingiber officinale (R), Allium sativum (L), Occimum sanctum (L), Azadirachta indica (L), Psidium guajava (L), Citrus limon (L), Carica papaya (L), Morinda citrifolia (L) and Azadirachta indica (seed). These plants and spices were chosen due to their dependence by local households as a means of traditional medicine. Essential oils extracted from the plant and spices showed growth inhibition of E. coli 0157:H7, whereas the highest antimicrobial activity was recorded for clove oil. Jasmine, pawpaw and neem (seed oil) had the lowest growth respectively. All other extracts had moderate activity. Additionally, the aqueous and ethanol extracts of each plant were used to determine the total phenolic content (TPC). From the plants tested, the TPC of aqueous extract varied from 612±3.15 to 2.67±0.11 (mg GAE/100gdw), while TPC of ethanol extract varied from 434±2.87 to 1.02±0.09 (mg GAE/100gdw). The highest TPC was recorded for noni aqueous extract and the lowest was for jasmine ethanol extract. This study reports the inhibitory effects and phenolic content of 12 herbs and spices and thus its potential use for developing safe pharmaceutical agents

Antimicrobial activity of selected plant extracts against common food borne pathogenic bacteria

Increasing antibiotic resistance of important human pathogens calls for investigation and discovery of new antibiotics. Various medicinal plants and spices available in Fiji have antimicrobial potential against various food-borne pathogens. This research aims to address the assumed antimicrobial activity of twelve selected plant extracts against fifteen food-borne pathogens and to evaluate the pathogens resistances. The Kirby-Bauer Method was used in this study to determine the potency of plant extracts. Total Phenolic Content (TPC) was determined by the Folin-Ciocalteu Spectrophotometric method. The chosen plant species samples used were Morinda citrifolia (noni) leaves, Syzygium aromaticum (clove) bud, Psidium guajava (guava) leaves, Ocimum basilicum (basil) leaves, Carica papaya (pawpaw) leaves, Azadirachta indica (neem) seed oil, Citrus limon (lemon) leaves, and Zingiber officinale (ginger) root. Extracts from these eight plants were tested against common food-borne bacteria; Clostridium perfringens, Citrobacter youngae, Enterobacter aerogenes, Enterobacter amnigenus, Enterobacter cloacae, Escherichia coli, Hafnia alveia, Klebsiella oxytoca, Klebsiella pneumoniae, Morganella morganii, Proteus vulgaris, Proteus mirabilis, Photobacterium damselae, Raoultella ornithinolytica and Vibrio alginolyticus. Both resistance and antibacterial responses were observed for the different plant extracts. All plant extracts were successful in inhibiting bacterial growth for different number of species at varying levels of effectiveness with noni being the most effective. The highest inhibition zones (ZOI > 14 mm) were shown by garlic, basil, jasmine and neem. Highest mean ZOI was shown by noni at 11.4 mm followed by garlic at 10.1 mm and clove at 8.4 mm. Minimum inhibitory concentrations were determined for extracts exhibiting antibacterial potential. TPC may attribute to the antibacterial properties of the extracts, however, this needs further investigation. Results indicate presence of possible bioactive compounds in the extracts which can aid in search for new antibiotic drugs from plant sources. Studies that identify the compounds of therapeutically important flora in Fiji is recommended

Depuration of a freshwater clam (Batissa violacea) from Rewa River in Fiji using a bio - filter set-up in closed and open water circulatory system

The effectiveness of the freshwater bivalve Batissa violacea depuration was tested in closed and open water circulatory system over a 48 h period. The closed circulatory system included a sand biofilter. Microbial levels were assessed every 4 h using Total Aerobic Plate Count (TPC) for heterotrophs and Most Probable Number (MPN) for coliforms. TPC and coliform loads in bivalve tissue reduced rapidly to low and undetectable levels in a closed circulatory system while open system showed a slower reduction. Both TPC and coliform loads remained above detectable levels throughout the depuration period. Closed system showed similar patterns of logarithmic reduction of TPC and coliforms in all cases with R 2>0.95 and p<0.001. Similar results were observed for tank water however, reduction of TPC and coliforms were slower. Biofilm formation was observed in the interior walls of the aquarium tanks over 48 h in all cases. Physicochemical parameters did not show any significant change. The reduction in TPC and coliform load in B. violacea suggests that biofilter in a closed water circulatory system is a simple, cost-effective, water conserving and effective way to significantly reduce the spoilage and coliform bacterial load that is accumulated in the clams