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Aim Biogeographical processes underlying Indo-Pacific biodiversity patterns have been relatively well studied in marine shallow water invertebrates and fishes, but have been explored much less extensively in seaweeds, despite these organisms often displaying markedly different patterns. Using the marine red alga Portieria as a model, we aim to gain understanding of the evolutionary processes generating seaweed biogeographical patterns. Our results will be evaluated and compared with known patterns and processes in animals. Location Indo-Pacific marine region. Methods Species diversity estimates were inferred using DNA-based species delimitation methods. Historical biogeographical patterns were inferred based on a six-gene time-calibrated phylogeny, distribution data of 802 specimens, and probabilistic modelling of geographical range evolution. The importance of geographical isolation for speciation was further evaluated by population genetic analyses at the intraspecific level. Results We delimited 92 candidate species, most with restricted distributions, suggesting low dispersal capacity. Highest species diversity was found in the Indo-Malay Archipelago (IMA). Our phylogeny indicates that Portieria originated during the late Cretaceous in the area that is now the Central Indo-Pacific. The biogeographical history of Portieria includes repeated dispersal events to peripheral regions, followed by long-term persistence and diversification of lineages within those regions, and limited dispersal back to the IMA. Main conclusions Our results suggest that the long geological history of the IMA played an important role in shaping Portieria diversity. High species richness in the IMA resulted from a combination of speciation at small spatial scales, possibly as a result of increased regional habitat diversity from the Eocene onwards, and species accumulation via dispersal and/or island integration through tectonic movement. Our results are consistent with the biodiversity feedback model, in which biodiversity hotspots act as both "centres of origin" and "centres of accumulation," and corroborate previous findings for invertebrates and fish that there is no single unifying model explaining the biological diversity within the IMA.

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Flanders Marine Institute and its consortium of experts on non-indigenous species conduct an ongoing effort to collect and maintain a list of alien species with documented established populations in the Belgian part of the North Sea and its adjacent estuaries. The list strives to include all currently known non-indigenous and cryptogenic species registered in salt and brackish environments in the Belgian part of the North Sea, the Belgian coastal zone and adjacent estuaries (Yser, Scheldt, Ostend Sluicedock). The discovery of America (1492) marked by a strong increase in trans-Atlantic shipping is set as the historical baseline of this assessment. This effort scrutinizes intentional and unintentional introductions by man or other vectors. Alien species for which there is no evidence of resident populations are not included in the list, nor are species that are limited to the fresh water environment. Newly registered species as a consequence of (expected) naturally induced migrations are also excluded. This initiative aims at providing a freely available online source of information on non-indigenous species and its associated network of experts for this study area. This includes definitions, information sheets and background literature, by species, and further links to European and international initiatives. Each information sheet describes the life cycle and ecology of the species, the introduction pathways and distribution, the possible effects or impacts of the species on its environment and potential mitigation measures. Pictures and a fully documented reference list - all available at the VLIZ library - represent an important added-value.http://www.vliz.be/NL/Cijfers_Beleid/Niet_inheemse (Dutch)

In the last decade, ecological and biogeographical studies (mainly terrestrial) have greatly benefited from recent developments in geographical techniques, and numerous test cases have been published. However, very few phycological studies emphasizing ecology and biogeography have incorporated these techniques, using traditional, nonspatially explicit descriptive and multivariate statistics instead. Here, we show a satellitebased seasonal mapping study of macroalgal communities in the Arabian Sea, and a global species’ distribution modelling effort of a cryptic green algal complex forming worldwide blooms on physically damaged coral reefs. We demonstrate how spatially explicit information contributes to more efficient work and new insights in marine ecology and biogeography, and comment on why previous studies did not include geographical techniques. Lastly, we briefly discuss future perspectives of spatially explicit phycological studies.

Boodlea composita (Harvey) F. Brand and Phyllodictyon anastomosans (Harvey) Kraft & M.J. Wynne, two widespread tropical siphonocladalean green algae, have had a long and confusing history because of the vague taxonomic boundaries between the two species. Molecular phylogenetic studies on the basis of nuclear-encoded rDNA sequences have resolved these indistinct species boundaries and suggest these taxa are part of a species complex. Detailed morphological investigations in combination with field and culture observations show that the concept of traditionally recognised taxa in this species complex is clouded by an ecologically induced phenotypic plasticity and developmental variability. Examination of a large number of specimens of B. composita, P. anastomosans and morphologically allied taxa including Boodlea siamensis Reinbold, Boodlea montagnei (Harvey ex J.E. Gray) Egerod, Nereodictyon imitans Gerloff and Struveopsis siamensis (Egerod) P. C. Silva, worldwide, including types, shows a wide morphological variety. We recognise seven more or less distinct morphological entities based on differences in thallus architectures, branching systems, cell dimensions and tenacular cell types. Awaiting the recovery of the true nature of the defined entities in this species complex (different species or growth forms of the same species), they are referred to as morphotypes, i.e. making no assumptions as to which taxonomic level they best apply.

Despite the potential model role of the green algal genus Codium for studies of marine speciation and evolution, there have been difficulties with species delimitation and a molecular phylogenetic framework was lacking. In the present study, 74 evolutionarily significant units (ESUs) are delimited using 227 rbcL exon 1 sequences obtained from specimens collected throughout the genus’ range. Several morpho-species were shown to be poorly defined, with some clearly in need of lumping and others containing pseudo-cryptic diversity. A phylogenetic hypothesis of 72 Codium ESUs is inferred from rbcL exon 1 and rps3–rpl16 sequence data using a conventional nucleotide substitution model (GTR + C + I), a codon position model and a covariotide (covarion) model, and the fit of a multitude of substitution models and alignment partitioning strategies to the sequence data is reported. Molecular clock tree rooting was carried out because outgroup rooting was probably affected by phylogenetic bias. Several aspects of the evolution of morphological features of Codium are discussed and the inferred phylogenetic hypothesis is used as a framework to study the biogeography of the genus, both at a global scale and within the Indian Ocean.

Two rare and ill-known subtidal species of stalked, net-forming green algae, Struvea gardineri A.Gepp & E.Gepp and Phyllodictyon orientale (A.Gepp & E.Gepp) Kraft & M.J.Wynne, are re-described on the basis of the examination of type material and recent collections from the Maldives, Seychelles, and Socotra Island in the tropical Indian Ocean. The taxonomic position of both species is re-appraised on the basis of morphological data (cell division, branching pattern, tenacular cells, crystalline cell inclusions, cell shape, and cell dimensions) and molecular phylogenetic evidence (partial large subunit nuclear ribosomal DNA sequences). On the basis of the occurrence of segregative cell division in young plants of S. gardineri, this species is returned to its original genus, Struvea. Cell division in P. orientale takes place exclusively by centripetal wall ingrowths, confirming its placement in the genus Phyllodictyon as currently defined. However, morphological observations and molecular phylogenetic studies indicate that the delineation of genera on the basis of modes of cell division is problematic, and that the genera Struvea and Phyllodictyon, as presently conceived, almost certainly do not represent natural groups.

The marine green alga Boodlea vanbosseae is widely distributed in the tropical Indo-West Pacific region. The phylogenetic position of this somewhat unusual member of the genus is assessed based on morphological examination and phylogenetic analysis of nuclear-encoded partial large subunit rDNA sequences. Boodlea vanbosseae differs from other species of the genus by its coarse, irregularly branching filaments, the typical rhizoids developing from the proximal or apical poles of cells and the absence of calcium oxalate crystalline cell inclusions. These apparent morphological differences are confirmed by the molecular data, which reveal that B. vanbosseae is distantly related to other species of Boodlea (B. composita and B. montagnei), but instead clusters in another siphonocladalean clade that includes Anadyomene, Microdictyon, Cladophora liebetruthii and C. catenata. Within this clade, B. vanbosseae is most closely related to C. catenata, with which it shares several morphological features, such as a cushion-like habit composed of coarse filaments, and the presence of similar rhizoidal cells with terminal haptera. At this stage we restrain ourselves from making taxonomic changes because recent molecular phylogenetic studies have demonstrated that a complete rearrangement of the classification in the Siphonocladales and Cladophorales is inevitable. Remarkably, the cells in both taxa are infected by marine, ascomycotan fungi, which grow either on the distal face of the cross walls in B. vanbosseae, or on the longitudinal cell wall in C. catenata.

Dictyota is a genus of tropical to warm temperate brown algae characterized by parenchymatous, flattened thalli that grow from a single, transversely oriented apical cell. Dictyota is currently distinguished from allied genera of the tribe Dictyoteae (Dilophus, Glossophora, Glossophorella, and Pachydictyon) by the structure of the cortical and medullary layers, as well as the relative abundance of surface proliferations. Even though the traditional classification of the Dictyoteae has repeatedly been criticized in the past, the absence of sound molecular data has so far discouraged any new taxonomic proposals apart from a merger of Dilophus with Dictyota, which has been accepted by only part of the phycological community. Phylogenetic analysis of rbcL gene, partial 26S rDNA sequence, and combined data sets, including four of five generitypes, demonstrates that the traditional classification does not accurately reflect the evolutionary history of the group. None of the genera are resolved as a monophyletic clade. Hence, a merger of Glossophora, Glossophorella, and Pachydictyon in Dictyota is proposed. Two new genera, Canistrocarpus (incorporating D. cervicornis, D. crispata, and D. magneana) and Rugulopteryx (accommodating D. radicans, Dil. suhrii, and Dil. marginata), are proposed. Both genera are supported by molecular indications and a combination of reproductive and vegetative characters. The position of Dil. fastigiatus as a clade sister to Dictyota s.l. and the absence of Dil. gunnianus, the generitype of Dilophus, from the analyses, prevented us from making a more definite statement on the status of the latter genus.

Valonia cladophora Kützing was described from New Caledonia in the 1860s, on the basis of a single specimen, but has not since been observed or studied. Preliminary observations of the type specimen led to its transfer to the genus Cladophora and because of ICBN regulations the species required a new name, C. mamillata Leliaert in Millar & Prud’homme van Reine. In this paper, a detailed description of this poorly known taxon is provided. Cladophora mamillata is characterized by mamillate elevations on the cross-walls, a unique feature in the genus. Morphologically, C. mamillata falls into the Cladophora section Aegagropila, where it closely resembles C. catenata (Linnaeus) Kützing, a widespread species in the Indo-Pacific and Atlantic Oceans.

A reassessment of the genus Cladophoropsis results in the recognition of six morphospecies: C. macromeres, C. magna, C. membranacea, C. philippinensis, C. sundanensis and C. vaucheriiformis. The emended genus Cladophoropsis is characterized by mat- or cushion-forming plants attached to the substratum by tenacular cells or by rhizoids that sprout from the proximal pole of the basal cells or are formed in any part of the thallus, cell division by centripetal wall ingrowths or occasionally segregative, cells producing a single lateral but older cells occasionally producing secondary laterals, cross walls at the base of the laterals either absent or their formation markedly delayed and reinforcement of the thallus by entangling of the filaments or by anastomosis of adjacent filaments by tenacular cells. The different species are distinguished from each other based on thallus structure, mode of cell division, organization of branch systems, mode of thallus attachment and reinforcement, shape and dimensions of the cells and shape of the crystalline cell inclusions. Twenty Cladophoropsis species are excluded from the genus, including the widely distributed Indo-Pacific species C. herpestica and C. javanica, which have been found to be unrelated to other Cladophoropsis species but instead allied with species of the Cladophora section Longi-articulatae. Phylogenetic studies based on molecular data have furthermore demonstrated that Cladophoropsis is closely related to Boodlea, Phyllodictyon, Struveopsis, Struvea and Chamaedoris and that the genus probably does not form a natural group within this genus complex. Morphologically this can be illustrated by a number of Cladophoropsis species (e.g. C. magna and C. membranacea) crossing generic boundaries by sharing common features with Chamaedoris, Boodlea, Phyllodictyon and Struvea. For the benefit of taxonomic stability, Cladophoropsis is presently maintained, awaiting additional molecular evidence.

Molecular systematic studies have changed the face of algal taxonomy. Particularly at the species level, molecular phylogenetic research has revealed the inaccuracy of morphology-based taxonomy: Cryptic and pseudo-cryptic species were shown to exist within many morphologically conceived species. This study focused on section Rhipsalis of the green algal genus Halimeda. This section was known to contain cryptic diversity and to comprise species with overlapping morphological boundaries. In the present study, species diversity within the section and identity of individual specimens were assessed using ITS1–5.8S–ITS2 (nrDNA) and rps3 (cpDNA) sequence data. The sequences grouped in a number of clear-cut genotypic clusters that were considered species. The same specimens were subjected to morphometric analysis of external morphological and anatomical structures. Morphological differences between the genotypic cluster species were assessed using discriminant analysis. It was shown that significant morphological differences exist between genetically delineated species and that allocation of specimens to species on the basis of morphometric variables is nearly perfect. Anatomical characters yielded better results than external morphological characters. Two approaches were offered to allow future morphological identifications: a probabilistic approach based on classification functions of discriminant analyses and the classical approach of an identification key.

This study investigates the floristic composition and the ecological and biogeographical characteristics of macroalgal communities in three bays along the coastline of the southern province of Dhofar in the Sultanate of Oman. Dhofar is located in the north-western Arabian upwelling province. From June through September the south-west monsoon winds cause Ekman transport of surface waters away from the Arabian coastline. This brings cold nutrient-rich waters from deeper layers into the eufotic zone.At each study site nine 0.25 m2 quadrants were sampled, three in the intertidal zone, three at a depth of 5m and three at a depth of 10m. In the intertidal zone Ulva fasciata and Melanothamnus somalensis are the dominant species. At two of the study sites Nizamuddinia zanardinii and Sargassum oligocystum are the dominant species in the subtidal zone, at the third site Jania sp. and Codium duthieae are the most abundant.Multivariate analysis was carried out on the data collected in the present study and data from previous studies on the macroalgal assemblages of the Socotra Archipelago and Masirah Island (Schils & Coppejans, 2003). DCA at species level showed a strong gradient in floristic composition from upwelling sheltered sites (Gulf of Oman, west coast of Masirah, north coast of Socotra and seagrass beds of both Masirah Island and the Socotra Archipelago) to upwelling exposed sites (east coast of Masirah Island, south coast of Socotra and Dhofar). The bays of Dhofar clearly have high affinities with the other upwelling exposed sites, but nonetheless cluster analysis showed that they are very well separated from all the other study areas. This uniqueness is also illustrated by the large number of indicator species pointed out by the indicator species analysis, among which are many endemics and species with a disjunct distribution.Affinities with remote areas were assessed based on the data collected in this study and species inventories of 11 countries in the Indian Ocean. For all Arabian Sea locations the similarity with the tropical coasts of east Africa and Indonesia is much lower than the similarity with South Africa and Australia, where besides subtropical conditions also temperate conditions occur. The rbcL gene of a number of specimens of Codium and Portieria was sequenced in order to assess whether these specimens are related to morphologically similar Japanese specimens. This analysis has shown that the Japanese and Omani specimens of the supposedly disjunctly distributed species are not related.

Grateloupia filicina (C. Agardh) Lamouroux, originally described from the Mediterranean Sea, has long been considered a textbook example of a marine red alga with a cosmopolitan distribution. An rbcL-based molecular phylogeny, encompassing samples covering the entire geographic distribution of the species, revealed a plethora of ‘‘cryptic’’ species, whereby the presence of genuine G. filicina is limited to the Mediterranean basin. The phylogeny revealed a strong biogeographic imprint, with specimens from temperate regions resolved in clades composed of species inhabiting the same geographic region. Presence of widely divergent morphologies in the temperate clades indicated that several lineages have converged independently to a G. filicina-type morphology. Tropical representatives are resolved in a single clade with very uniform G. filicina-type morphology and pairwise sequence divergences that are lower than the average divergence observed in temperate lineages. This, combined with a lack of clear geographic structure among the tropical lineages, may indicate a more recent divergence with long-range dispersal capacities. Violations to the biogeographic signal in temperate lineages seemed to be due to either inadequate taxonomy or recent introductions. Grateloupia minima P. & H. Crouan, a taxon placed in synonymy under G. filicina, is reinstated as a separate species distributed in the northeast Atlantic Ocean. Grateloupia capensis sp. nov. is described to accommodate specimens from South Africa with a G. filicina-type morphology, and G. filicina var. luxurians is elevated to species status. Morphological and anatomical characters were put forward that support the distinctiveness of these three distinct species.

Twelve species of the genus Cladophora occur along the South African East Coast. Detailed descriptions and illustrations are presented. Four species are recorded for the first time in South Africa: C. catenata, C. vagabunda, C. horii and C. dotyana; the last two are also new records for the Indian Ocean. A comparison of the South African C. rugulosa specimens with specimens of C. prolifera from South Africa and other regions have shown that these species are not synonymous as previously considered, leading to the resurrection of C. rugulosa which is probably a South African endemic.

A systematic reassessment of the sole representative of the South African genus Phyllymenia, P. belangeri, indicates a lack of clear-cut diagnostic characters to separate it from Grateloupia. The morphology of the auxiliary cell ampullae, widely regarded as a key generic character in the Halymeniaceae, is almost identical in both genera. The autapomorphic character that has traditionally separated Phyllymenia from Grateloupia is the formation of pronounced lateral cytoplasmic protuberances on inner cortical cells. However, the establishment of protuberances is correlated with the presence of large intercellular spaces between neighbouring cortical cell files, coupled with narrow intercalary cortical cells. Thus, in order to establish secondary pit connections to more distant neighbouring cells, cortical cell protuberances may have become more prominent in P. belangeri than in species of Grateloupia with smaller intercellular spaces. Phylogenetic analyses of chloroplast-encoded rbcL sequences for a dataset including four representatives of P. belangeri and 32 other species, currently placed in Grateloupia or Prionitis, resolve (with high support) P. belangeri as a sister taxon of G. longifolia from South Africa. Based on morphological and molecular evidence, it is therefore proposed that Phyllymenia be reduced to a synonym of Grateloupia.

Nuclear ribosomal and plastid DNA sequences of specimens belonging to section Halimeda of the pantropical green seaweed genus Halimeda show that the group under scrutiny contains many more genetically delineable species than those recognized by classical taxonomy. Discordances between phylograms inferred from nuclear and plastid DNA sequences suggest that reticulate evolution has been involved in speciation within the clade. Nonetheless, our data do not allow ruling out certain alternative explanations for the discordances. Several pseudo-cryptic species are restricted to the margins of the generic distribution range. In a clade of H. cuneata sibling species from widely separated subtropical localities in the Indian Ocean, the South African sibling branches off first, leaving the Arabian and West Australian species as closest relatives. We hypothesize that geographic isolation of the siblings may have taken place following Pleistocene or Pliocene periods of climatic cooling during which subtropical species occupied larger distribution ranges. A more basal separation of Atlantic, Indo-Pacifc, and Mediterranean species indicates vicariance. The alternative events that could have caused this vicariance are discussed.

Aglaothamnion rigidulum is described as a new species from southern Kwazulu-Natal, South Africa. The main distinguishing characters are the robust nature of the filaments, the dense cortication in the lower part of the thallus, the alternating distichous branching pattern and the unbranched determinate laterals which curve upwards and overtop the apical cell. In addition to a detailed description of the vegetative anatomy and reproductive structures, attention is drawn to unusual changes of the branching pattern associated with the formation of procarps near the apices of indeterminate axes, and the subsequent formation of an involucrum protecting the developing gonimoblast. The plane of branching changes by 90degrees at the fertile axial cell, and the determinate laterals 2-3 cells below and above the fertile axial cell are strongly incurved and branch once or twice subdichotomously, thereby forming a protective involucrum enclosing the developing gonimoblast from all sides. This aspect of the morphology has not been well documented in either Aglaothamnion or Callithamnion, but may well occur in several other species belonging to the Callithamnieae.

Aim: Comparing the marine plant communities of two islands, with a similar diversity in biotopes, in two different upwelling areas of the Arabian Sea. Location: Arabian Sea: (1) the Socotra Archipelago (Yemen; 12.47°N, 53.87°E) in the Somali upwelling area, (2) Masirah Island (Oman; 20.42°N, 58.79°E) in the upwelling area of the southern Arabian Peninsula. Methods: The marine flora of different biotopes around both islands were examined by means of qualitative assessments. Ordination analysis (DCA) was used to identify the different plant communities and to correlate these with environmental parameters. The species composition of the identified communities were compared (tripartite similarity index) and their biogeographic affinity with nations bordering the Indian Ocean was determined. Indicator species analyses were performed to identify the characteristic species of the different plant communities and their biotopes. Results: The DCA analysis shows a clustering of sites (plant communities) corresponding with their geographic position, linked in turn to the prevailing environmental conditions of the different coastal areas. The combined interpretation of the ordination, similarity and biogeographic analyses results in the aggregation of similar plant communities of both upwelling areas into four biotopes. Main Conclusions: The north coast communities of Socotra and the west coast communities of Masirah can be grouped into 3 biotopes related to the degree of exposure and sedimentation. These biotopes are typified by indicator species, characteristic for specific substrata, and have a high biogeographic affinity with the East African coast. The plant communities of Socotra’s south coast and Masirah’s east coast constitute a fourth biotope, being diverse and species rich, typified by a large proportion of red macroalgae including the characteristic species of the unique Arabian Sea flora. This biotope has a pronounced biogeographic affinity with distant regions (disjunctly distributed taxa). Within the different biotopes, the communities of Masirah are more divergent from an East African flora in comparison to Socotra, the latter being a stepping stone between the East African and Arabian Sea flora.

Dictyota naevosa (Suhr) Montagne and D. radicans Harvey possess characters that do not conform to the generic description of Dictyota. The generic boundaries in the tribe Dictyoteae are thus called into question. Dictyota naevosa differs from other Dictyota species by having more than one layer of cortical cells in the lower part of the thallus. The presence of a multilayered cortex is the only character distinguishing Pachydictyon from Dictyota. Dictyota radicans is characterised by the presence of terete surface proliferations, a feature used to distinguish Glossophora from Dictyota. Both D. naevosa and D. radicans have clear sister species that are currently placed in the genus Dilophus. The segregation of Dilophus from Dictyota, as still advocated by some authors, therefore becomes untenable. The morphological evidence leads us to question the generic status of Pachydictyon, Glossophora and Glossophorella, since the characters used to delineate these genera are commonly found in some species of Dictyota.

A third species of Chamaebotrys ,C. erectus, is described from an upwelling region off Socotra Island,Yemen. The new species clearly displays one of the defining features of the genus, viz. terminal tetrasporangia in nemathecial sori. The nemathecia become diffuse when mature and produce secondary tetrasporangia. Tetraspores can apparently germinate in situ, resulting in compound thalli with tetrasporic and cystocarpic parts. Carpogonial branches are four-celled and cystocarps are protuberant, both of which features illustrate the affinities of Chamaebotrys with the closely related Coelarthrum.

A three-year project bas increased by more than 30 % the number of seaweed and echinoderm species recorded off KwaZulu-Natal, and included some new to science? It demonstrates that we do not need to go to abyssal depths to make a significant and novel contribution to our knowledge of marine biodiversity.

The genus Tapeinodasya, originally described by Weber-van Bosse (1904) from Indonesia and the Sulu Archipelago (Philippines), has remained one of the least known genera of the Dasyaceae. Based on recent collections from the East African coast, vegetative and tetrasporangial structures are described in detail for the first time and the placement of genus Tapeinodasya in the Dasyaceae based on cellulosympodial growth is confirmed. The genus is separated from all other genera of the Dasyaceae by a distinctive cauliflower-like habit, complete absence of monosiphonous filaments, extensively corticated tetrasporangial stichidia and the presence of both pre- and postsporangial cover cells. genus Tapeinodasya appears to be related to the Heterosiphonia-like genera, based on an alternate sequence of periaxial cell formation, a primary alternate- distichous arrangement of holoblastic branches, and branches separated from one another by one or more unbranched segments. Placement of genus Tapeinodasya in a clade with Thuretia and Dictyurus as recently hypothesized is verified by the recognition of a clockwise mode of alternate periaxial cell formation and a primary bilateral organisation. Comparison of the East African specimens with the type collections of the other known species, shows that the Tanzanian specimens belong to the Indonesian Tapeinodasya bornetii rather than to T. etheliae which was described from the Amirante Islands. The presence of T. bornetii in Tanzania represents a substantial range extension and a new record for the Indian Ocean.

A new ceramiaceous alga, Sciurothamnion stegengae De Clerck et Kraft, gen. et sp. nov., is described from the western Indian Ocean and the Philippines. Sciurothamnion appears related to the tribe Callithamnieae on the basis of the position and composition of its procarps and by the majority of post-fertilization events. It differs, however, from all current members of the tribe by the presence of two periaxial cells bearing determinate laterals per axial cell. Additionally, unlike any present representative of the subfamily Callithamnioideae, no intercalary foot cell is formed after diploidization of the paired auxiliary cells. The genus is characterized by a terminal foot cell (“disposal cell”), which segregates the haploid nuclei of the diploidized auxiliary cell from the diploid zygote nucleus. The nature of three types of foot cells reported in the Ceramiaceae (intercalary foot cells containing only haploid nuclei, intercalary foot cells containing haploid nuclei and a diploid nucleus, and terminal foot cells containing only haploid nuclei) is discussed.

Thirteen taxa of Rhodophyta, Phaeophyta and Chlorophyta are reported for the first time from Inhaca Island: Gelidiopsis repens, Solieria robusta, Tricleocarpa cylindrica, Dictyota humifusa, Padina boergesenii, Sargassum crassifolium, Stoechospermum polypodioides, Caulerpa microphysa, Cladophora catenata, C. coelothrix, C. vagabunda, Rhizoclonium africanum, Udotea indica. All of these species are new records for Mozambique, Cladophora catenata is recorded for the first time in the Indian Ocean. The seaweed flora of Inhaca Island now totals 224 taxa, including 73 genera of Rhodophyta (120 species), 15 genera of Phaeophyta (28 species) and 28 genera of Chlorophyta (35 species, some of which have several varieties).

Rocky shores (natural intertidal hard substrates) are known for their high density and especially for their high diversity of marine organisms (e.g. algae, invertebrates, fishes and birds). They are complex ecosystems in which the biological richness results from biotic (predation, competition, grazing) and abiotic (tides, waves, coastal topography) interactions. The majority of the organisms living on rocky shores are restricted to this habitat, forming distinct communities that are significantly different from the surrounding soft substrates (e.g. sandy beaches).In contrast to the French and English coast, natural rocky shores do not exist in Belgium. Numerous artificial hard structures (e.g. groins, harbour walls and dykes) have however been built within the framework of coastal protection. Along the Belgian coast the typical rocky shore biota can only develop on these structures, thereby increasing the Belgian marine biodiversity. Furthermore, these hard substrates are also important for a number of bird species (e.g. Turnstone (Arenaria interpres) and Purple Sandpiper (Calidris maritima) as foraging grounds.A study of the physical characterization of the hard substrates along the Belgian coast has resulted in four types of structures: harbour walls, dykes, groins and piers. Seventeen sites were sampled. Numerous samples were collected at each site where the height above the mean low water spring mark (MLWS) and other physical characters (e.g. substrate type, wave exposure, etc.) were noted. Each sample comprised a quadrat of area 0.25 m² where the % cover and relative abundance of the macrofauna and -algae were ascertained. A total of 91 macrofaunal species and 78 macro-algal species were identified. Most of these organisms are generalist species and widespread throughout North-West Europe. Differences in biodiversity and density have been found on the various structural types. This can be partly attributed to the various substrates used in the construction of these structures (e.g. sedimentary rock, wood, concrete, etc.), due to their specific physical characteristics (e.g. density, porosity, etc.). Other physical characteristics that appear to be important were geographical orientation, wave-exposure and degree of sand inundation. The information gained from such a study may provide useful information for the construction of hard substrates along the coast that will not only serve their original function (e.g. sand stabilisation, harbour infrastructure, etc.), but also be ecologically meaningful.

The subtidal understorey seaweed communities were studied along a coastal distance of 104 km around the Cape Peninsula, which is situated in an overlap region between two marine provinces and characterized by a considerable temperature gradient. Sampling was carried out at six sites (4 to 10 quadrats per site) around the Cape Peninsula. For each of the quadrats, biomass of each species, grazing, and environmental variables such as temperature, wave exposure and sand cover were determined. The data were analysed using canonical correspondence analysis (CCA) and two way indicator species analysis (TWINSPAN). A total of 142 seaweed taxa were found at the six sites (21 Chlorophyta, 14 Phaeophyta and 107 Rhodophyta). The two sides of the Peninsula have a very different biomass-composition of Chlorophyta, Phaeophyta and Rhodophyta. The biomass of Rhodophyta in the Atlantic sites is much higher than in the Bay, and the biomass of Chlorophyta is higher in False Bay than on the west coast. A change in floristic composition of subtidal algal communities around the Cape Peninsula can be observed and is principally related to seawater temperature and wave exposure. Next to these physical factors, grazing is demonstrated to be important in determining species composition. A lower degree of wave exposure might result in a higher number of grazers in False Bay. The occurrence of a higher cover of encrusting corallines in the Bay is probably a consequence of the higher grazing pressure. Distinct community types can be recognized from TWINSPAN and CCA.

A three-year project has increased by more than 30% the number of seaweed and echinoderm species recorded off KwaZulu-Natal, and included some new to science. It demonstrates that we do not need to go to abyssal depths to make a significant and novel contribution to our knowledge of marine biodiversity.