FUNGI ISOLATED FROM MANGROVE DETRITUS IN IBENO LOCAL GOVERNMENT AREA OF AKWA IBOM STATE

ABSTRACT A study of fungi from mangrove detritus in Ibeno Local Government Area was carried out. Composite sample of decayed plant parts (wood, leaf, root and stem) was aseptically collected from the mangrove floor. Fungal isolation from the sample on PDA (Potato Dextrose Agar) at room temperature (25 ± 20C) for 4 days revealed the presence of a single culture, Trichoderma sp. This was identified through morphological and microscopic examinations which showed the following characteristics; white colony with blue green shades, septate hyphae, branched conidiophores and philiades in groups. A systematic research should further be initiated for fungi from special extreme environments such as the mangroves, deep-sea, hypoxic zones (with low oxygen levels) and hydrothermal vents for enzymes, degradation of xenobiotics and bioremediation applications.

CHAPTER ONE

  1.                           INTRODUCTION

          The word mangrove is derived from the Portuguese word “Mangue” which means “tree” and the English word “grove” which is used for “trees” and shrubs that are found in shallow or muddy areas”. Mangroves are highly productive, salt-tolerant forest ecosystems confined to intertidal zones of sheltered shores, estuaries, tidal creeks, backwaters, lagoons, marshes and mudflats of the tropical and subtropical latitudes, mainly between latitudes 25oN and 25oS. These important ecosystems are a dynamic ecotone between terrestrial and marine habitats and of great ecological, economic, and social significance (Gopal and Chauhan, 2006). Approximately 25% of the world’s coastline is dominated by mangroves distributes in 112 countries and territories encompassing an area of 181,000km2 (Spalding et al., 1997). The remaining mangrove forest areas of the world in 2000 was 53,190 square miles (137,760km2) spanning 118 countries and territories (Giri et al., 2011). Approximately 75% of the world’s mangroves are found in just 15 countries, and the largest percentage of mangroves is found between 5oN and 5oS latitudes (Giri et al., 2011). Mangroves are represented on all continents with tropical and subtropical coasts, that is North/Central America (15%), South America (11%) (Giri et al., 2011), Africa (21%), Middle East and Oceania (12%) including Australia and Asia (42%) which has the largest amount of the world’s mangroves. Important mangrove swamps in Africa are found in Kenya, Tanzania, democratic republic of Congo and Madagascar with the latter even admixing at the coastal verge with dry deciduous forests. Nigeria has Africa’s largest mangrove concentration, spanning 36,000km2, though oil spills and leaks have destroyed many in the last 50 years, damaging the local fishing economy and water quality (O’Neill, 2007). In America, mangroves live in many parts of the tropical and subtropical coastal zones of the North, South and central America. Because of their sensitivity to subfreezing temperatures, mangroves in the United states are very limited to the Florida Peninsula (Florida mangroves) and some isolated growths of black mangrove (Avicenniaa germinans) at the Southmost coast of Louisiania and South Texas(Yang et al 2008). In central America, and Caribbean coasts of Belize, Costa Rica etc. A 2010 Satellite-based study of Belize’s mangroves by the World Wildlife Fund (WWF) and the Water Centre for the Humid Tropics of Latin America and the Caribbean found in 2010, mangroves covered some 184,548 acres (74,684 hectares) or 3.4% of Belize’s territory (Cherrington et al., 2010). In South America, Brazil contains approximately 26,000km2 of mangals, 15% of the world’s total. Venezuela has 4% of the world’s mangroves, with an extension of 6735km2. Colombia possesses large mangrove forests on both its Caribbean and Pacific coasts.

          In Asia, mangroves occur on Asia’s South coast, throughout the Indian subcontinent, in all south-east Asian countries. On the Malayan Peninsula, mangroves cover an estimated 1,089.7 square kilometers (420.75sqmi), while most of the remaining 5,320 square kilometers (2, 054sqmi) mangroves in Malaysia are on the island of Borneo. In Indonesia, mangroves occur around much of Sumatra, Borneo, Sulawesi and the surrounding islands, while further north, they are found along the coast of the Malay Peninsula. Indonesia has around 9.36 million hectares of mangrove forests, but 48% is categorized as “moderately damaged” and 23% as “badly damaged”. In Pakistan, mangroves are located mainly along the delta of the Indus River. Oman near Muscat, in the Middle East supports large areas of mangroves, in particular at Shinas, Qurm park and Mahout island. Iranian mangrove forests occur between 250111N to 270521 N. Mangrove is also widely seen in Tarut Island, east of Quatif in Suadi Arabia. In India, mangrove tidal forests are found in the areas of coasts influenced by tides. In Bangladesh, the Sundarbans in the largest single block of tidal halophytic mangrove forest in the world. In Oceania mangroves occur in northern Australian and New Guinea. Australia has about 11,500km2 of mangroves primarily on the northern and eastern coasts of the continent. New Zealand has mangrove forests extending to around 380S. Species of mangrove are also found on Pacific islands.

          Mangrove ecosystems otherwise called coastal wetlands are considered to be one of the most productive natural ecosystems on earth (Kohlmeyer and Volmann-Kohlmeyer, 1993). Mangrove species diversity is well known for animals and plants, including micro organisms. Plants here include different species of mangrove and the word mangrove is used in at least three senses; most broadly to refer to the habitat and entire plant assemblage or mangal (Hogarth, 1999) for which the terms mangrove forest biome, mangrove swamp and mangrove forest are also used. It refers to all trees and large shrubs in the mangrove swamp and narrowly refers to the mangrove family of plants, the Rhizophoraceae, or even more specifically just to mangrove trees of the genus, Rhizophora. Mangroves are various large and extensive types of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics. Mangrove swamps on the other hand, are found in tropical and subtropical tidal areas. Areas where mangals occur include estuaries and marine shorelines. The intertidal existence to which these trees are adapted represents the major limitation to the number of species able to thrive in their habitat. About 110 species are considered “mangroves”, in the sense of being a tree that grows in such a saline swamp, though only a few are from the mangrove plant genus, Rhizophora. About 25 species of mangrove are found on various pacific islands, with extensive mangals on some islands. Also, more than 5 species of Rhizophoraceae grow in Australia with particularly high biodiversity on the island of New Guinea and northern Australia. However, a given mangrove swamp typically features only a small number of trees species. It is not uncommon for a mangrove forest in Caribbean to feature only three to four tree species. For comparison, the tropical rainforest biome contains thousands of tree species, but this is not to say mangrove forest lacks biodiversity. Though the trees themselves are few in species, the ecosystem these trees create provide a home for a variety of other organisms. Mangrove vegetation have morphologically and physiologically adapted to harsh conditions such as high salinity. High tide bring in salt water and when the tides recedes, solar evaporation of the sea water in the soil leads to further increases in salinity. The return of tide can flush out these soils, bringing them back to salinity levels comparable to that of sea water. Other harsh conditions include, tidal extremes, high wind velocity, high temperature, anaerobic clayey soils, moisture, problems of anoxia and frequent and frequent tidal inundation, and mangrove plants require a number of physiological adaptations as already stated  above ,like possession of pneumatophores, stilt roots, vivipary, possession of lenticels, possession of aerenchyma for survival.      

          Mangrove forests have been proved as best diversity “hotspots” for fungi (Shearer et al., 2007). They constitute the second largest ecological group of marine fungi (Sridhar, 2004). Considerable amount of detritus in the form of leaf litter, twigs, bark, wood, inflorescence and other detritus is generated from mangrove forests (Wafar et al., 1997). Mangroves being detritus-based, considerable fungal population are involved in detritus processing. And as diverse vegetation exists in mangroves, it is considered as a major niche of fungal repository. These fungi play an important role in the nutritive cycle (nutrient cycling) and support the mangrove ecosystem. They commonly occur as saprophytes on decomposing organic matter, as symbionts of plants and animals and as parasites of plants in mangrove ecosystems. Mangrove fungi include lower fungi (Oomycetes and thraustochytrids) and higher fungi (ascomycetes and basidiomycetes). The fungi associated with mangroves are known as manglicolous fungi which include mostly marine fungi. However a small group of terrestrial fungi also occurs in mangrove environment.     

Fungi are of diverse species as well as their habitats including mangrove detritus which is the concern of this study. The knowledge about the possibility to culture or grow fungi from mangrove detritus is still incognizant to 75% of the masses. However, most fungi species look alike morphologically, in growth patterns, colour and forms. Furthermore, although so much works on fungi have been published, the knowledge of mangrove fungi is still at the cataloguing stage and despite some systematic information, there is little knowledge about the role of mangrove fungi in the ecosystem because only a few researchers have studied the physiology and biochemistry of manglicolous fungi (mangrove fungi). Also, detailed works have been carried out on fungi colonizing in wood submerged in water, mangrove leaves and seedlings but their distribution has not been adequately studied in mangrove ecosystems. Much works has not been done on fungi inhabiting the mangrove the mangrove detritus in the mangrove ecosystem of Ibeno Local Government Area. Moreover, despite a better understanding of the importance of mangroves, they continue to be destroyed at an alarming rate (Ong, 1995). It is therefore imperative to identify, record and quantify the abundance of fungi found in the detritus of the mangrove plant species in Ibeno Local Government Area and to culture them to ensure their conservation for future biochemical, genetic and molecular studies.

1.1     OBJECTIVES OF THE STUDY

          Objectives of this study include; To isolate, characterize and identify the species of fungi found in the detritus of mangrove plant species in Ibeno Local Government Area.