Volume 46, Issue 2

Four species of Sphacelaria producing tribuliform propagules in the section Tribuloides were distinguished from each other on the basis of the branching pattern and propagule morphology including the division type of the subapical cells and the shape of the lateral apical cells. Sphacelaria plumula shows complanate tufts composed of erect filaments bearing pinnate determinate laterals arranged in one plane, while the other species, S. tribuloides, S. brachygonia and S. novae-caledoniae , form erect tufts with irregular indeterminate branches. Sphacelaria tribuloides is distinguished by typical tribuliform propagules with acute conical lateral apical cells. Sphacelaria plumula has slightly larger propagules with obtuse conical lateral apical cells and a rather vague constriction at the waist. The distinguishing features of S. brachygonia are its slightly tribuliform, more often transversely ellipsoid propagules with round conical lateral apical cells and small lower parts under the waist. In S. novae-caledoniae , the filaments are slender and its mature propagules have the rectangular lateral apical cells produced by 2–3 longitudinal and transverse divisions of the subapical cells. The morphometric features of segments, propagules and zoidangia in the species of the section Tribuloides , including S. californica and S. novae-hollandiae , were found to be variable, but in some species they can be used to distinguish taxa. In addition, the holotypes of S. cornuta and S. nipponica , previously placed in the section Tribuloides , were examined. The results suggest that S. cornuta can be considered as a synonym of S. tribuloides , and S. nipponica should be placed in the section Furcigerae , based on the presence of diagonal divisions in the subapical cells as well as long stalks and prominent arms in the propagules.

The reproductive state of Ceramium tenuicorne (Kütz.) WӦrn was studied in a salinity and latitudinal gradient near its inner distribution limit in the brackish Baltic Sea, and in laboratory growth experiments on the gametophytes and tetrasporophytes. Along the gradient, a strong reduction in sexual reproduction and an increased tetrasporophyte dominance were observed. The observed changes may not only be explained by salinity constraints. Growth occurred between 1 and 24 PSU and the optimum range for growth corresponded well to the salinity regime of the area studied. Field observations showed that sexual reproduction is at least occasionally possible in salinities around 4 PSU. It is likely that severed climatic conditions constrain sexual reproduction towards the north, but C. tenuicorne remains an ecologically dominant species in large parts of its distributional area. Viable populations are maintained essentially by vegetative reproduction, such as fragmentation and rhizoidal re-attachment. Observations on vegetative propagules were sparse, but these may serve as an important physical escape from temporarily unfavourable conditions in areas where sexual reproduction is unreliable.

The composition, abundance, and distribution of dinoflagellate resting cysts in recent sediments were analyzed at 12 sites in Bahía Concepción in the subtropical Gulf of California. Calcareous and organic Peridiniales, Gonyaulacales, and Gymnodiniales were identified at species level (25 cyst types). Empty cysts constituted 75–90% of cysts in the samples. Cyst assemblages were dominated by calcareous Peridiniales (30–70%) and Gonyaulacales (13–44%), represented mainly by Scrippsiella trochoidea and Lingulodinium polyedrum . In the first centimeter of sediment, cyst counts varied from 173 to 9, 933 cysts g −1 wet weight, and increased in abundance in the inner area of the bay. Cysts of the toxic species Gymnodinium catenatum were also detected, and successful cyst germination of Alexandrium margalefii is described. Cyst abundance and distribution patterns suggest that the bay acts as a cyst trap, and that the cyst assemblages reflect the local community of meroplanktonic dinoflagellates.

A fractionation study of crude agar from the red seaweed Digenea simplex led to isolation of a galactan sulfate fraction consisting of a carrageenan-agaroid hybrid-type backbone. This polysaccharide fraction, containing D-galactose (Gal), L-Gal, 3,6-anhydro-D-galactose (D-AnGal), L-AnGal, sulfate and a small amount of xylose, appeared to consist of repeating units of both 4- O -β-D-galactopyranosyl-3,6-anhydro-L-galactose (agarobiose) and 4- O -β-D-galactopyranosyl-3,6-anhydro-D-galactose (carrabiose) on the basis of results from a partial methanolysis study. Two other repeating disaccharide units in the backbone, 4- O -β-D-galactopyranosyl- L-galactose and 4- O -β-D-galactopyranosyl-D-galactose, were also suggested by the methylation study. The sulfate groups were also suggested to be located at O-4 of (1→3)-linked D-Gal, O-6 of (1→3)-linked D-Gal, O-6 of (1→4)-linked L-Gal and/or O-2 of (1→4)-linked AnGal residues, besides O-3 of (1→4)-linked D-Gal residue. Co-occurrence of carrageenan and agarocolloid backbone structure among the genera in the Florideophycidae was also reviewed.

Thirty-six taxa of brown macroalgae (Phaeophyceae) are reported for the Caribbean coast of the Republic of Panama including 16 new records. Most of the species diversity is restricted to two families, Dictyotaceae and Sargassaceae. This updated list represents an increase in known algal diversity for Panama of approximately 80%, but diversity is probably underestimated as revealed by comparison to the Colombian and Costa Rican floras which harbor many species not yet recorded in the marine flora of Panama. In total species diversity, Panama's brown algal flora is considerably less diverse than Caribbean Colombia but comparable to Caribbean Costa Rica. In addition to presenting a comprehensive species list, we propose the synonymy of Dictyota pfaffii Schnetter with D. friabilis Setchell and D. jamaicensis W. R. Taylor with D. crenulata J. Agardh and discuss other taxonomic problems regarding the Caribbean Dictyotales.

In order to assess the influence of the River Po outflow on microphytobenthos distribution, two areas of the northern Adriatic Sea, differently affected by the River Po outflow, were investigated. Sediment samples were collected in June 1996 and February 1997 from two grids of six stations (from 14 to 66 m deep) located across the River Po plume front. In the top 1 cm of sediment, chlorophyll- a ranged from 11.2 to 278.8 mg m −2 , often exceeding integrated values in the water column, except during the winter phytoplankton bloom. Microphytobenthos densities (size >20 μm) ranged from 728 to 9278 cells cm −3 . Diatoms largely dominated microphytobenthic assemblages with both epipelic motile ( Pleurosigma spp., Gyrosigma spp., Navicula spp.) and non-motile forms ( Paralia sulcata , Hyalodiscus laevis ). Filamentous cyanobacteria (Oscillatoriales) were abundant in the summer. The vertical distribution of microphytobenthos revealed that a considerable fraction of the microalgal biomass (up to 40%) was located in the 3–6 cm sediment layer. Microphytobenthos did not display significant changes between sampling periods. Coastal sediments of the northern area displayed high densities of the marine planktonic Thalassiosira angulata , suggesting that high sedimentation rates occurred in the area facing the River Po delta. Conversely, in the southern area pennate epipelic diatoms dominated the microphytobenthic community. In both areas, offshore sediments displayed the dominance of the centric benthic diatom Paralia sulcata . The results of the present study indicate that the plume, which determined marked coast-offshore gradients, influenced both abundance and community structure.

Kappaphycus alvarezii, Eucheuma denticulatum and, more recently, Kappaphycus sp. ‘Sacol’ variety, are the carrageenan-containing red seaweeds currently farmed in the Philippines. The Kappaphycus sp. ‘Sacol’ variety is of particular interest to the Philippine seaweed industry because of its improved resistance to ‘ice-ice’ disease and its fast growing characteristics. Here we report on the detailed chemical analysis of the carrageenan from this species. The native and alkali-modified carrageenans from Kappaphycus sp. ‘Sacol’ variety were characterized by FT-IR, 1 H and 13 C NMR spectroscopy, and constituent sugar and methylation analyses and were compared to those from K. alvarezii, K. cottonii and Eucheuma denticulatum . The three Kappaphycus species contained predominantly κ-carrageenan with low levels of ι-carrageenan, methylated carrageenan and μ-precursor residues, while Eucheuma denticulatum contained predominantly ι-carrageenan with significant amounts of ν-precursor residues. Taxonomic classification of Kappaphycus species based on morphology has proved to be difficult because of their known plasticity. Molecular analysis using the rbcL sequence revealed that the Kappaphycus sp. ‘Sacol’ variety is most likely a form of K. cottonii .

Morphology and nuclear small-subunit (SSU) rDNA sequences from Ishige okamurae Yendo and I. sinicola (Setchell et Gardner) Chihara were investigated to describe their species and to infer their phylogenetic relationships within the Chordariales. Ishige okamurae has a narrower frond, a thicker cortical layer, acute apice and rough superficial arrangement in SEM in contrast to I. sinicola . These morphological differences were supported by the partial SSU sequence differences of 28 base pairs between two species. Ishige species were clearly distinguished from other chordarialean taxa by having inconspicuous apical meristematic cells, terminal unilocular sporangia, only coalescent determinate filaments and hairs from cryptostomata. Consistent with morphological observations, our SSU data indicated that Ishige might form an independent lineage with some possible affinities for the early lineage of the Ectocarpales sensu lato .

The red algal genus Mazzaella presents an interesting challenge to systematists and ecologists. The two species M. linearis and M. splendens are easily distinguished in their ideal form; however, in areas of intermediate wave exposure individuals form a seemingly continuous grade between the two species. On the basis of ecological investigations, it was concluded that the two forms are distinct at the species level and that plants of intermediate morphology can be best assigned to M. splendens . Field-identified ‘classic’ M. linearis and M. splendens (17 individuals each), as well as individuals of intermediate morphology (20 individuals), were collected. Sequences of the internal transcribed spacer (ITS) of the ribosomal cistron were determined for all of these individuals, as well as for related Mazzaella spp . Molecular phylogenetic analyses confirmed a close relationship between M. linearis and M. splendens , and identified their closest relative, M. sanguinea . Pairwise distance comparisons within M. splendens (including intermediate plants; 0–4 differences) and M. linearis (0–2 differences) were less than variation between species (8–12 differences), and both solidly clustered as monophyletic ( M. sanguinea as outgroup; 0–2 differences among four isolates) confirming the results of the ecological investigations. Two further aspects of the earlier ecological studies are also discussed: the conclusion that stipe length is a reliable character for distinguishing between these two species; and, a suggestion that M. splendens displays a slightly heteromorphic alternation of generations, the plants of intermediate morphology being tetrasporophytes (preferring the moderately wave-exposed habitats) whereas the ‘classic’ M. splendens are gametophytic with a preference for wave-sheltered habitats.