This study documented lorica ultrastructure variation in Corresponding author: and related taxa from natural populations. On that basis, inaccuracies in the taxonomic system of euglenoid Trachelomonas are pointed out. Loricae of T. caudata and taxa very similar to it were examined by light and scanning electron microscopy and by energy-dispersive X-ray spectroscopy (EDS). The latter observations showed similarity of chemical composition between loricae of different putative taxa, with silicon and iron as the main components, and the absence of a chemical element considered to be a very important component of trachelomonad envelopes - manganese. All observed morphotypes were classified in one complex based upon envelope configuration, and the “caudatae complex” was established. Our morphological analyses led us to conclude that f. pseudocaudata of T. caudata should be subsumed in the typical form or treated as a synonym of T. caudata, as the morphological differences between them are within the typical range of phenotypic variability of species from natural environments. The same view applies to the species T. bernardinensis, T. fusiformis, T. allorgei and T. molesta, which should be considered synonyms of T. caudata.

Mangrove macroalgae produce substantial proportion of biomass, which contributes to the coastal ecosystems. Relatively less is known for the seasonal variation in the occurrence and biomass of mangrove associated macroalgae. Consequently, mangrove macroalgae epiphytic on the pneumatophores of Avicennia marina (Forsk.) Vierh., were sampled from the Miri estuary of Sarawak during the four seasons of Malaysia namely southwest monsoon, northeast monsoon, and two inter-monsoons to elucidate seasonal variation in the occurrence and biomass production of macroalgae. Over the sample period, 11 species of mangrove macroalgae were identified from 6 genera. Six of these species such as Caloglossa leprieurii (Montagne) J.Agardh, C. adhaerens R.J.King & Puttock, C. stipitata E.Post, C. ogasawaraensis Okamura, Bostrychia kelanensis Grunow and Dictyota sp. were found to be common in each sample time. Considering four seasonal samples, maximum frequency of occurrence was observed for C. ogasawaraensis (66 ± 10%) and maximum biomass was observed for B. kelanensis (248 ± 95 g m^-2). Marked seasonal variations were observed in the frequencies of occurrence and the biomass for the most of the dominant macroalgal species. To the best of our knowledge this is the first time to report the seasonal pattern data for occurrence and abundance of macroalgae from the mangrove systems of Malaysia.

Laminaria rodriguezii Bornet is a deep-water brown alga endemic of the Mediterranean Sea. Lectotypification of Laminaria rodiguezii has been based on both Bornet's protologue and the original material housed at the cryptogamic collections of the Muséum National d'Histoire Naturelle de Paris (PC).

A survey of the species of Cystoseira (Fucales, Phaeophyceae, Ochrophyta) of Tunisia highlighted six Mediterranean endemic taxa rare or new for this country: C. barbata f. aurantia, C. brachycarpa var. claudiae, C. compressa subsp. pustulata, C. foeniculacea f. dubia, C. hyblaea and C. spinosa var. tenuior. The discovery and the study of these species, some of which were little known, have allowed some taxonomic and biogeographical uncertainties to be identified and discussed. On the basis of the results, the transfer of C. discors f. dubia to C. foeniculacea as C. foeniculacea f. dubia and the reinstatement of species rank for the Mediterranean endemic species C. schiffneri are proposed.

Spatial and temporal changes in the population structure and standing crop of Gracilariopsis sp. were studied in the San Ignacio Lagoon during two different sampling periods. Biomass (wet weight, g m^-2), thallus size and reproductive state were determined from November 2004 to August 2005. Standing crop was calculated from November 2007 to September 2008. The annual standing crop of Gracilariopsis sp. was estimated to be 1,300 wet tons. We found a seasonal growth cycle during both sampling periods, with the maximum biomass in spring (1,004 wet tons). Biomass was significantly higher near the mouth of the lagoon in shallow and sandy areas. This zone is associated with stronger currents and lower temperatures (annual mean of 20°C). The smallest thalli were found during autumn and winter, and the largest in spring. Senescence and detachment of the plants occurred in summer. Tetrasporangial thalli were the dominant phase in the population throughout the year, followed by vegetative (i.e. showing no reproductive structures) thalli. Gametophytes and carposporophytes were rarely observed during the study. The growth and propagation strategy of Gracilariopsis sp. in San Ignacio Lagoon is characteristic of a clonal population, which strongly suggests this species might be a good alternative for commercial agar production.