Volume 51, Issue 1

Recruitment of Posidonia oceanica from seeds is infrequent owing to the rare and unpredictable occurrence of sexual reproduction. However, in years of high reproductive success, ample supplies of seeds become available in drifting fruit; this could be a useful source of material for seabed restoration. In this study we introduce and combine viability tests and culture procedures for evaluating this material. Three different groups of collected fruits representing a phenological or maturation sequence were tested for seed viability with tetrazolium. We also examined the effects of storage on the germination and development of seedling root and shoot systems. The younger groups showed good (67–86%) germination and survival, with the tetrazolium viability test proving useful for predicting these processes. However, although a strong correlation between fruit and seed weight was observed, higher values of these parameters did not confer greater germination capacity. The seeds of fruits collected late in the season were more developed and plantlet roots and shoots grew faster under culture, but survival after 4 weeks was reduced (40%). Under the conditions tested, viability was highly reduced and there was no final seedling survival following storage.

Responses of a rocky intertidal community to seasonal sand-inundation were investigated on the cool-temperate west coast of South Africa by experimentally testing the hypothesis that the crustose components in certain macroalgae survive burial, enabling them to dominate the community when the shore is sand-free. Twelve 0.25×0.25 m plots served as controls in the mid-eulittoral and 12 in the upper eulittoral zone. Treatment 1 (T1) comprised a further 12 plots in each zone that were cleared of all biota (scraping, wire-brushing and burning) soon after the sand moved off in year 2. Treatment 2 (T2) comprised clearing a further 12 plots in each zone at the end of Year 2, just before sand returned, in case T1 had inadvertently removed early-settling microscopic stages. Mid-eulittoral zone controls developed similar communities each year dominated by Mazzaella capensis , Gymnogongrus complicatus , barnacles, mussels and small limpets, with smaller covers of several other macroalgae. Both treatments significantly reduced M. capensis , G. complicatus and G. glomeratus , but did not affect covers of other species. These three species persisted as crustose holdfasts, and the latter two also as crustose tetrasporophytes; the crusts probably comprise coalescent sporelings. All other species recruited annually as the sand moved off. In the upper eulittoral zone, T2 had no effect on the biota that developed, indicating that none of the species (including the dominants Porphyra capensis and Chthamalus dentatus ) relied on persistent elements to survive burial. These results confirm that sand-disturbed communities comprise a mixture of opportunistic and disturbance-tolerant species, but experimentally show the importance of crustose elements for survival of these red algae.

This study tested potential chemical defense of the green seaweed Avrainvillea elliottii against grazing by the sea urchin Lytechinus variegatus . We examined intraspecific variation of defensive chemicals in different parts of the thallus (margin, blade and stipe). We predicted that thallus parts making the greatest contributions to thallus fitness would show the greatest chemical deterrence to herbivory. The susceptibility of the whole alga and its different parts to consumption by L. variegatus was evaluated using assays consisting of powdered algae treated with natural concentrations of crude A. elliottii extract. Results from feeding evaluations showed that the crude extracts of whole plants and different thallus parts deterred consumption by this sea urchin. The results also supported our prediction that stronger chemical defenses occur in the more apical and younger areas of the thallus (margins), parts whose loss would result in the greatest reduction of fitness. These results provide added evidence supporting the ability of siphonaceous or coenocytic green macroalgae to concentrate defensive chemicals in growing parts.

Species of the genus Sargassum (Fucales, Phaeophyceae) belonging to the Schizophycus group (in subgenus Sargassum sensu lato ) from the Ryukyu Islands, southern Japan, were morphologically reinvestigated, and two entities were recognized: Sargassum ryukyuense sp. nov. and Sargassum pinnatifidum . The new species is characterized by: 1) compressed primary branches; 2) simple lanceolate primary and lateral leaves with an undulate and dentate margin in all stages; 3) lateral branches issuing alternate-distichously on the main branches in one plane; 4) long and flattened receptacles arranged alternate-distichously on terminal branches; 5) main and lateral branches on the stem issuing as foliar expansions in the early stage of development; and 6) vesicles with a simple coronal leaf. This new species resembles S. pinnatifidum in features 1), 3) and 5). However, it differs from S. pinnatifidum in features 2), 4) and 6). Furthermore, this new species can be distinguished from all previously described species based on the complete set of diagnostic features above and by the presence of long lingulate receptacles with short stalks. The new species is known to be endemic in the Ryukyu Islands and adjacent waters of southern Japan.

A taxonomic survey of nanoflagellates in the extreme southern Brazilian coastal waters of the Patos Lagoon estuary and adjacent coastal shelf was undertaken using transmission electron microscopy. A total of 44 species was recorded including 42 nanoflagellates, one scale-bearing amoeba and two species incertae sedis . Scale-bearing haptophytes predominated (27 species), followed by prasinophytes (7), chrysophytes (6), pedinellids (2), incertae sedis (2) and one scale-bearing amoeba. Most of the species (42) are new records for Brazilian marine waters. Among the haptophytes, Chrysochromulina was the most species-rich genus, occurring mainly in high salinity waters, and C. simplex was the most frequent species. Scales of undescribed Chrysochromulina species were observed and documented. Other haptophytes present were Prymnesium parvum and Phaeocystis scrobiculata . Five scale-bearing prasinophytes of the genus Pyramimonas were observed including the uncommon species P. longicauda , in addition to Micromonas pusilla and Nephroselmis pyriformis . Among the chrysophytes, the scale-bearing Paraphysomonas species (4) and the loricate Dinobryon belgica were recorded. The pedinellids ( Apedinella radians and Parapedinella reticulata ), the amoeba Rabdiophrys sp. and the incertae sedis ( Meringosphaera mediterranea , Thaumatomastix sp.) are all scale-bearing protists. The 44 taxa (mostly scale-bearing flagellate species) identified and the finding of further undescribed Chrysochromulina species indicate that only a fraction of the species present in the region are known, and that an effort must be made to increase general knowledge of biodiversity in these southern waters.

Antarctic benthic marine diatoms from the Potter Cove region, King George Island were studied in samples collected during the austral summer 2003. A floristic list was made to add information on the Antarctic benthic diatom distribution. A total of 84 species was identified from four localities in Potter Cove, the majority of which are of cosmopolitan distribution. The most common taxa encountered were Cocconeis spp., Gyrosigma fasciola, Navicula cf. cancellata, N. cf. perminuta, Petroneis plagiostoma and Pleurosigma obscurum . Both G. fasciola and P. obscurum are recorded for the first time from Antarctica with such common occurrence. The overall diatom population in Potter Cove appeared rather different from other diatom populations observed in Antarctic marine habitats.

Since Chondrophycus poiteaui var. gemmiferus and C. corallopsis fall within the new recently validated segregate genus Palisada K.W. Nam, two new nomenclatural combinations are proposed: Palisada poiteaui var. gemmifera and P. corallopsis .