Abstract
Microbial mats are often the dominant benthic biotype in desert streams, however information on such mats is very scarce. We investigated the gross morphology of microbial mats and their cyanobacterial species composition in a perennially flowing wadi in Northern Oman, in relation to current flow and other biotic and abiotic variables. Physical and chemical parameters at the six sites were generally similar with low concentrations of soluble phosphorus and nitrogen; however, flow rates varied greatly with the highest velocity being 50 cm/s. The mats varied greatly in their gross morphology with the four sites with the highest current velocities forming low laminated structures attached to cobbles, and the two sites with minimal or no flow forming complex three-dimensional structures or free floating balls 1 to 3 cm in diameter. The concentration of chlorophyll a varied between 2.6 (±0.02) and 1.4 (±0.11) mg chlorophyll a g -1 mat fresh weight, with the highest concentration detected in the free floating balls. Twenty one cyanobacterial morphotypes belonging to 14 genera (5 unicellular and 9 filamentous) were identified with Calothrix and Leptolyngbya spp. as the most abundant. Cluster analysis of the cyanobacterial species composition showed that mats could have very different morphologies despite similar species compositions suggesting a high degree of plasticity of mat form. We conclude that microbial mats are important elements in Wadi ecosystems and have great variety of structure and community composition.
Highlights
Microbial mats are dense and often vertically stratified benthic communities (Stal and Caumette, 1994)
We investigated the gross morphology of microbial mats and their cyanobacterial species composition in a perennially flowing wadi in Northern Oman, in relation to current flow and other biotic and abiotic variables
Microbial mats are most commonly associated with extreme environments such as hot springs, hypersaline environments and hydrothermal vents (Paerl et al, 2000), they are often found in arid region streams, where they constitute an important component of ecosystem biomass and
Summary
Microbial mats are dense and often vertically stratified benthic communities (Stal and Caumette, 1994) They contain both autotrophic and heterotrophic bacteria and maintain tight internal cycling of nutrients, justifying their description as complete miniature ecosystems (Paerl and Pinckney, 1996). Wadi is an Arabian term used to describe corridors for fluvial run-off that may contain perennial, intermittent, or ephemeral surface flow They are important foci for both regional biodiversity and human activities including agriculture and recreation. During periods of low flow, spatial patchiness is common and in coarse cobble beds flow velocity may be an important determinant of periphyton biomass (Biggs et al, 1998) This patchiness can have significant effects on many important stream processes including the processing of organic carbon nutrient levels and grazer distribution (Casamatta and Vis, 2003)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
