Marine and Freshwater Research Marine and Freshwater Research Society
Advances in the aquatic sciences

Biodiversity of diatom assemblages in a Mediterranean semiarid stream: implications for conservation

M. Dolores Ros A , José Pedro Marín-Murcia A and Marina Aboal A B

A Laboratorio de Algología, Departamento de Biología Vegetal, Facultad de Biología, Campus de Espinardo, Universidad de Murcia, E-30100 Murcia, Spain.

B Corresponding author. Email:

Marine and Freshwater Research 60(1) 14-24
Submitted: 1 December 2007  Accepted: 12 October 2008   Published: 29 January 2009


Many semiarid streams are threatened both by human demands and climatic effects (global warming), but little is known about their algal biodiversity and their conservation value, especially in Mediterranean areas. The aim of the present study was to evaluate annual changes in the structure and species richness of diatom communities in runs and pools of an oligohaline, semiarid stream in south-eastern Spain, and their relationship with nutrients and hydrology. The pool substrate was covered most of the time by a yellow-brown coat, mainly composed of diatoms and a few cyanophytes (Leptolyngbya). In the runs, cyanophytes were dominant (Rivularia) and diatoms occurred as epiphytes. The diversity of these diatom assemblages was high, particularly in the pools. Some species were present throughout the year, whereas others showed a bimodal growth pattern. Maximum biomasses were reached in summer in the pools and in autumn in the runs, when levels of phosphorus increased as a result of flooding. Species richness and diversity were correlated with hydrology and sulfate concentrations, whereas biomass (as chlorophyll a and ash-free dry weight) was associated with variations in temperature, conductivity and ammonium. These semiarid streams are refuges of biodiversity, representing habitats reliant on cycles of drought and floods, which should be considered in proposals for their conservation.

Additional keywords: dynamics, south-eastern Spain.


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