a variety of plant resources in an variety of aquatic ecosystems. The community structure separates significantly along axis 1, where the tree leaf litter communities show similarity between each other but are different from communities developed on wood and grass leaves, which lie to the left of PCA axis 1 and are separated from each other along PCA axis 2. Source: Data from Gulis (2001).

Fungi are a diverse group of organisms. A range of taxonomic groups is involved in the process of decomposition and mineralization of nutrients from organic sources. It has been shown above that these fungi differ in their enzymatic capabilities (their ability to decompose certain resources), their rate of growth (competitiveness), and their interactions with other organisms in the ecosystem. We have concentrated mainly on terrestrial ecosystems, as here we have the greatest information regarding the role of fungi in decomposition, the measures of rates of nutrient mineralization from organic matter, and the effects of fungi on rock dissolution and soil development. We can see from the discussions of the activities of fungi in aquatic and marine ecosystems that they are involved in similar processes of decomposition of organic resources and that the interactions between fungi and their changing environment during decomposition of these resources leads to similar patterns of resources succession, limitation of decomposition by resources quality, and impacts of environmental constraints upon their activity in the same manner as in the terrestrial environment. Information regarding measure of the amount of nutrient mineralization, however, and the importance of this to plant primary production is less available than for terrestrial ecosystems. Soil development and stability is a unique feature of terrestrial ecosystems. Lichens are abundant on rocky coastlines, but there is little information regarding their input to the nutrient content of oceans by the process of rock dissolution. In salt marsh sediments, fungi probably play a role in binding particles together and reducing the possibility of erosion caused by tidal and wave action. We know that approximately 50% of aquatic and salt marsh plants are mycorrhizal (Khan and Belik, 1995; Cooke and Lefor, 1998), but we have little information about the extent of mycorrhizal hyphal development into sediments in either aquatic or salt marsh habitats or their roles in nutrient acquisition, sediment stabilization, or interactions with other biotic components.