Band 54, Heft 6

Erythroglossum lusitanicum is a foliose, turf-forming member of the Delesseriaceae that colonizes sand-covered intertidal rocks on the Atlantic Iberian Peninsula. We examined (i) the phenology of this alga and (ii) the structure and temporal dynamics of its associated flora at two sites over one year. Species diversity was low in the assemblage, which was dominated by E. lusitanicum. Assemblage structure was essentially constant through the year. There were, however, significant differences in E. lusitanicum characteristics between the two sites. At one, E. lusitanicum was more abundant, thalli were longer and wider, and the proportion of plants with tetrasporangia was higher than at the second location. At the first site, the phenological traits tracked a temporal cycle. Thallus length and blade width were highest in April; after gradual deterioration of the apical portions of the plants, individual sizes reached minimum values in July. Subsequently, individual growth rate was low and plant length was nearly constant from September to February. Tetrasporangia were common throughout most of the year; only in July they were totally absent. Temperature and daylength were inversely related to reproduction. Sexual reproductive structures were not observed. The abundant growth of basal proliferations suggests that vegetative propagation very probably plays an important role in the maintenance of E. lusitanicum populations.

A complete checklist of intertidal to shallow subtidal marine green seaweeds (Chlorophyta) growing on the subtropical island of Hainan (China) is presented here for the first time. It covers data from extensive recent (1990–2009) and historical (1933–1935) collections, and additional published records from various time periods. Data were analyzed by time period. We postulate that environmental changes on Hainan Island documented since the 1980s (e.g., degradation of coral reefs, development of tourism and mariculture farms) are reflected in the green algal species complement and in the dominance or absence of specific algal groups during different time periods. In total, 105 green algal taxa were recorded, including 37 new to Hainan Island, and 18 new records for China. There was a clearly evident change in floristic composition between early and recent collections. In the 1930s, there was a dominance of Caulerpaceae, Codiaceae and Cladophoraceae. By 1990/1992, the numbers of Ulvaceae had increased 1.6-fold and numbers of Cladophoraceae 1.7-fold. Both families contain many opportunistic species that prefer nutrient-enriched or degraded environments. At the same time, species richness of Codiaceae, Caulerpaceae and Udotaceae, families with complex thallus structures, decreased considerably. The floristic differences between the 1990/1992 and 2008/2009 collections were minor.

Six species of macroalgae are newly reported for the Caribbean International Biosphere Reserve Seaflower . All the algae were found growing epiphytically on Thalassia testudinum in shallow (<1 m) meadows around San Andrés Island. Two of these species, Stylonema alsidii and Colaconema hypneae , have been previously reported from Colombian waters, whereas Chroodactylon ornatum , Colaconema dasyae , Colaconema hallandicum and Herposiphonia parca are new records for Colombia.

Ceramium cormacii is newly described based on both vegetative and tetrasporangial features of specimens growing on loggerhead sea turtles ( Caretta caretta ) from the Mediterranean Sea. The new species is characterised by both prostrate and erect axes (9–12 mm high), dichotomously to pseudo-dichotomously branched with apices straight or slightly incurved, attached to the substratum by unicellular rhizoids often terminating in multicellular pads, incomplete cortication formed by one to three rows of acropetal cells, five to six periaxial cells, and tetrahedral tetrasporangia produced by periaxial cells, strongly protruding and partially involucrated.

The marine green alga Chaetomorpha valida (Cladophoraceae, Cladophorales) has been found for several years fouling aquaculture ponds along coasts of the cities Dalian and Rongcheng, P.R. China. Using unialgal culture and microscopic observation, we completed the life history of C. valida and discovered fragment regeneration for the first time. The life history comprised an isomorphic alternation between gametophytes and sporophytes typical of most other members of the Cladophorales. Male and female gametes fused into zygotes then developed into sporophytes. Quadriflagellate zoospores produced by mature sprophytes gave rise to new gametophytes that yielded biflagellate gametes. Germination of zygotes and zoospores was of the bipolar erect type, as observed in some other species of Chaetomorpha . Fragment regeneration occurred in both gametophytes and sporophytes via production of polar algal fragments, which directly developed into entire filaments to give a self-replicating gene­ration. The results improved understanding of the seasonal abundances of C. valida in spring and summer.

Hypo-osmotic conditions are among the most stressful environmental factors that affect seaweed physiology and productivity. To improve understanding of hypo-osmotic adaptation and to find genes involved in low salinity stress, we conducted an analysis of expressed sequence tags (ESTs) on the κ-carrageenan-producing red algae, Kappaphycus alvarezii . Of 454 tentatively unique genes (TUGs), 281 matched protein sequences by BlastX analysis ( e value≤10 -3 ), 112 TUGs matched ESTs from other agar- or carrageenan-producing red algae, and 98 TUGs were annotated. The transcriptional profiles of six functional genes from K. alvarezii ESTs were examined. An ATP-binding cassette transporter gene and a sodium phosphate symporter gene were significantly up-regulated, indicating the importance of membrane transport proteins in coping with hypo-osmotic stress conditions.

The structure of a small marine planktonic centric diatom belonging to the genus Thalassiosira was characterised using electron microscopy; and data on its ultrastructure, autecology and initial valve formation are provided here. Although our specimens shared some characteristics with Thalassiosira proschkinae sensu lato , they differed from the type in their permanent lack of areolae and in being constitutively weakly silicified, regardless of the silicate concentration in the medium. Valve areolation in our Thalassiosira isolate was less pronounced than in many other members of the genus and varied with salinity. The most significant effect of changing salinity was that the areola pattern becomes more diffuse, so that it was more difficult to observe areolae even at the margin of the valve. A decrease in salinity also induced changes in cell size, number of marginal fultoportulae and surface architecture. Cells in very low salinity (2) died after 24–48 h. Low silicate in the culture medium affected cell diameter (10% increase in the presence of added silicate). Putative auxospores and initial cells were found in some of the cultures, and some interesting variations in the valve morphology of initial cells were observed.

Halophila stipulacea is a dioecious seagrass that colonised the Mediterranean basin probably following the opening of the Suez Canal in 1869. We investigated its occurrence in the southern Mediterranean. This was done by conducting targeted surveys in two countries (Tunisia and Libya) and compiling existing information from former research. Four new meadows of H. stipulacea were found in the study area: Al-wahesh Lagoon and Tobrouk Bay in Libya, and Kerkennah Island-Allama and Cap Monastir in Tunisia. The new record in Cap Monastir (Tunisia) documents a displacement of approximately 150 km north of the previous limit of H. stipulacea in the southern Mediterranean, which probably represents the westernmost extension of H. stipulacea ’s distribution 3000 km west along the coast from the site of first colonisation at the mouth of the Suez Canal in Port Said. In the Cap Monastir meadow, the shoot density (±SD) was 9900±3509 m -2 and the leaf area index was 3.15±0.5 m 2 m -2 . In Libya, a small meadow of H. stipulacea was documented for the first time in Tobrouk Bay, with an estimated shoot density of 476±83 m -2 .

Rhizophora annamalayana is a natural mangrove hybrid with a rare seed set; the species is fast disappearing. We investigated possible causes of rare fruit set and explored ways of overcoming reproductive difficulties in this mangrove. Flowers open in the early morning in the hybrid and its parent species. Anthers dehisced after flower opening only in Rhizophora mucronata and Rhizophora apiculata . Anthesis and anther dehiscence took up to 5 days in all three species. Stigma receptivity peaked during anthesis; receptivity was lost within 8 h in R. annamalayana and R. mucronata . In R. apiculata , anthesis occurred inside the flowers, confirming that cleiostogamy occurred. Pollen of R. mucronata was 100% viable. Viability was 53% in R . apiculata . In R. annamalayana , only 3% of pollen was viable. R. mucronata flowers offered pollen and nectar to visitors, which were mainly Lucilia caesar (flies, bees, ants, etc.). Pollinators of R. annamalayana were restricted to Monobia quadridens , Vespa tropica and Ocybadistes walkeri . R. annamalayana reproduced by cross-pollination.