Spatial And Temporal Distribution Of Epiphytic Diatoms On Macroalgae Inhabiting Port Said Coast, Mediterranean Sea, Egypt

The epiphytic diatoms growing on seaweeds inhabiting Port Said coast were investigated seasonally during the period from summer 2004 to spring 2005. A total of 62 species of the epiphytic diatoms were recorded. They comprised fifty nine pennate and three centric forms. The important components in the flora of the epiphytic diatoms were belonging to the genera: Achnanthes, Achnanthidium, Fragilaria, Gyrosigma, Licmophora, Navicula, Pleurosigma, Synedra and Tabellaria. The rest recorded epiphytic diatoms were considered rare and of no significance in defining the epiphytic flora on seaweeds. Summer showed the highest relative abundance of total epiphytes reached to 53%, while the lowest value (5%) was recorded in spring. Site I displayed a maximum relative abundance (64%) of the epiphytes occurrence, while site IV showed a minimum percentage (6%). Of the macroalgal species inhabiting Port Said coast, 14 species were mostly utilized by the epiphytic diatoms. The results revealed that there was a relationship between the architecture of seaweeds and the associated epiphytes. Most of the foliose and flattened macroalgal thallus was nearly not preferred as a substrate. By contrast, the fine and sometimes branched thallus hosted many epiphytic diatoms. Considering the macroalgal species which used as a substrate, the attached epiphytic diatoms observed different patterns of preference. Some epiphytic diatoms showed host specificity giving unialgal epiphytic flora on few hosts. Other epiphytic diatoms did not reflect the previous preference pattern and existed on the majority of the macroalgae indicating the absence of selectivity.New Egyptian Journal of Microbiology Vol. 17 (2) 2007: pp. 285-29