Differential gene expression in fronds and stolons of the siphonous macroalga, Caulerpa lentillifera.

The green alga, Caulerpa lentillifera, is composed of a single cell with multiple nuclei, but it possesses structures analogous to leaves or fronds, stems or stolons, and roots or rhizoids. To understand molecular mechanisms involved in formation and function of these structures, we carried out RNA-seq analysis of fronds and stolons (including rhizoids). Taking advantage of the decoded genome of C. lentillifera, the present RNA-seq analysis addressed transcripts corresponding to 9,311 genes identified in the genome. RNA-seq data suggested that 8,734 genes are expressed in sporophytes. Despite the siphonous body of the alga, differential gene expression was evident in the two structures. 1,027 (11.8%) and 1,129 (12.9%) genes were preferentially expressed in fronds and stolons, respectively, while the remaining 6,578 (75.3%) genes were expressed at the same level in both. Most genes preferentially expressed in fronds are associated with photosynthesis and plant hormone pathways, including abscisic acid signaling. In contrast, those preferentially expressed in stolons are associated with translation and DNA replication. These results indicate that gene expression is regulated differently between fronds and stolons, which probably governs the function of each structure. Together with genomic information, the present transcriptomic data provide genic information about development and physiology of this unique, siphonous organism.

High-throughput sequencing revealed differences of microbial community structure and diversity between healthy and diseased Caulerpa lentillifera.

BACKGROUND: Caulerpa lentillifera is one of the most important economic green macroalgae in the world. Increasing demand for consumption has led to the commercial cultivation of C. lentillifera in Japan and Vietnam in recent decades. Concomitant with the increase of C. lentillifera cultivation is a rise in disease. We hypothesise that epiphytes or other microorganisms outbreak at the C. lentillifera farm may be an important factor contributing to disease in C. lentillifera. The main aims are obtaining differences in the microbial community structure and diversity between healthy and diseased C. lentillifera and key epiphytes and other microorganisms affecting the differences through the results of high-throughput sequencing and bioinformatics analysis in the present study. RESULTS: A total of 14,050, 2479, and 941 operational taxonomic units (OTUs) were obtained from all samples using 16S rDNA, 18S rDNA, and internal transcribed spacer (ITS) high-throughput sequencing, respectively. 16S rDNA sequencing and 18S rDNA sequencing showed that microbial community diversity was higher in diseased C. lentillifera than in healthy C. lentillifera. Both PCoA results and UPGMA results indicated that the healthy and diseased algae samples have characteristically different microbial communities. The predominant prokaryotic phyla were Proteobacteria, Planctomycetes, Bacteroidetes, Cyanobacteria, Acidobacteria, Acidobacteria and Parcubacteria in all sequences. Chlorophyta was the most abundant eukaryotic phylum followed by Bacillariophyta based on 18S rDNA sequencing. Ascomycota was the dominant fungal phylum detected in healthy C. lentillifera based on ITS sequencing, whereas fungi was rare in diseased C. lentillifera, suggesting that Ascomycota was probably fungal endosymbiont in healthy C. lentillifera. There was a significantly higher abundance of Bacteroidetes, Cyanobacteria, Bacillariophyta, Ulvales and Tetraselmis in diseased C. lentillifera than in healthy C. lentillifera. Disease outbreaks significantly change carbohydrate metabolism, environmental information processing and genetic information processing of prokaryotic communities in C. lentillifera through predicted functional analyses using the Tax4Fun tool. CONCLUSIONS: Bacteroidetes, Cyanobacteria, Bacillariophyta, Ulvales and Tetraselmis outbreak at the C. lentillifera farm sites was an important factor contributing to disease in C. lentillifera.

Amendment of Caulerpa sertularioides marine alga with sulfur-containing materials to accelerate Cu removal from aqueous media.

This study reports a new approach of alga amendment in a live mode. The Caulerpa sertularioides alga was modified with sulfur-containing materials of methionine (C5H11NO2S) and sodium sulfate (Na2SO4) to more concentrate the sulfur content of the yielded biomass (adsorbent). The simple and amended C. sertularioides alga was fully characterized with FTIR, SEM, EDX, BET, BJH, and pHzpc techniques. The copper adsorption from aqueous media was done by three adsorbents of C. sertularioides-simple (CSS), C. sertularioides-Na2SO4 (CSN), and C. sertularioides-C5H11NO2S (CSC). The parameters of pH (2-6), adsorbent dosage (2-10 g/L), and contact time (3-80 min) were optimized at 5, 5 g/L, and 60 min, respectively. According to Langmuir isotherm (the best-fitted model), the maximum adsorption capacity of CSN (98.04 mg/g) was obtained 2.4 times higher than CSC (40.73 mg/g) and 9.5 times higher than CSS (10.29 mg/g). The Cu adsorption process by the adsorbents was best-fitted pseudo-second-order kinetic model. The CSN, CSC, and CSS biomasses were successfully reused 5, 4, and 4 times, respectively. The thermodynamic study revealed that the copper adsorption process by CSN is exothermic and non-spontaneous. Finally, the suitability of adsorbents prepared from algae was tested by cleaning a simulated wastewater.

Biotic resistance and vegetative propagule pressure co-regulate the invasion success of a marine clonal macrophyte.

Propagule pressure is considered a major driver of plant invasion success. Great propagule pressure would enable invasive species to colonize new areas overcoming the resistance of native species. Many highly invasive aquatic macrophytes regenerate from vegetative propagules, but few studies have experimentally investigated the importance of propagule pressure and biotic resistance, and their interaction, in determining invasion success. By manipulating both recipient habitat and the input of vegetative propagules of the invasive seaweed Caulerpa cylindracea in mesocosm, we examined whether higher propagule pressure would overcome the resistance of a native congeneric (Caulerpa prolifera) and influence its performance. With the native, C. cylindracea population frond number decreased irrespectively of pressure level. High propagule pressure did not increase stolon length and single plant size decreased due to the effects of intra- and interspecific competition. Native biomass decreased with increasing C. cylindracea propagule pressure. These results indicate that higher propagule pressure may fail in enhancing C. cylindracea invasion success in habitats colonized by the native species, and they suggest that biotic resistance and propagule pressure co-regulate the invasion process. These findings emphasize the need to preserve/restore native seaweed populations and may help to design effective management actions to prevent further C. cylindracea spread.

Field transplantation of seagrass (Posidonia oceanica) seedlings: Effects of invasive algae and nutrients.

Seedlings are a key life stage in seagrasses, providing genetic diversity and being a useful tool for restoration. We examined the influence of increased sediment nutrients and the presence of the invasive macroalga Caulerpa cylindracea on the success of in situ transplanting Posidonia oceanica seedlings in a six-month experiment. Our results indicate that one-year old seedlings successfully survive in the field and their survival and growth are positively affected by the presence of C. cylindracea. Furthermore, nutrient addition in the sediment had positive effects on both C. cylindracea (increasing its cover) and seedlings (increasing leaf development), and the increased C. cylindracea cover did not result in detrimental effects on seedlings. Therefore, biological invasions and nutrient addition do not reinforce each other in the short term to negatively impact transplanted seedlings, which highlights facilitative interactions between invasive algae and native seagrass and provides useful information for successful strategies of seagrass restoration.

Food selection of a generalist herbivore exposed to native and alien seaweeds.

Understanding which factors influence the invasion of alien seaweed has become a central concern in ecology. Increasing evidence suggests that the feeding preferences of native herbivores influence the success of alien seaweeds in the new community. We investigated food selection of a generalist native grazer Paracentrotus lividus, in the presence of two alien seaweeds (Caulerpa cylindracea and Caulerpa taxifolia var. distichophylla) and two native seaweeds (Dictyopteris membranacea and Cystoseira compressa). Sea urchins were fed with six experimental food items: C. cylindracea, C. taxifolia var. distichophylla, a mixture of C. cylindracea and C. taxifolia var. distichophylla, D. membranacea, C. compressa and a mixture of D. membranacea and C. compressa. P. lividus ingested all the combinations of food offered, though it preferentially consumed the alien mixture, C. cylindracea and D. membranacea. The alien C. taxifolia var. distichophylla was consumed significantly less than the other food items and, interestingly, it was ingested in a greater amount when mixed with C. cylindracea than when on its own. This finding suggests that C. taxifolia var. distichophylla may become vulnerable to sea urchin grazing when it grows intermingled with C. cylindracea, which does not gain immediate protection from the presence of the very low palatable congeneric seaweed. The present study highlights the potential role of native grazers to indirectly affect the interspecific competition between the two alien seaweeds in the Mediterranean Sea.

Meiofauna communities, nematode diversity and C degradation rates in seagrass (Posidonia oceanica L.) and unvegetated sediments invaded by the algae Caulerpa cylindracea (Sonder).

We investigated meiofauna and sedimentary C cycling in seagrass (Posidonia oceanica) and unvegetated sediments invaded and not invaded by the non-indigenous tropical algae Caulerpa cylindracea. In both habitats, invaded sediments were characterized by higher organic matter contents. No effect was observed for prokaryotes and C degradation rates. In seagrass sediments, C turnover in invaded beds was about half that in not invaded ones. Meiofaunal communities varied significantly among invaded and not invaded grounds only in bare sediments. In both habitats, nematode species richness and assemblage composition were not affected by the algae. The effect of C. cylindracea on the turnover and nestedness components of the Jaccard dissimilarity varied between the two habitats. We show that the presence of C. cylindracea gives rise to variable consequences on meiofauna biodiversity and C cycling in different habitats. We conclude that further studies across different habitats and ecological components are needed to ultimately understand and predict the consequences of C. cylindracea invasion in shallow Mediterranean ecosystems.

Ecophysiological responses of three Mediterranean invasive seaweeds (Acrothamnion preissii, Lophocladia lallemandii and Caulerpa cylindracea) to experimental warming.

The Mediterranean Sea is a hotspot for invasive species and projected Mediterranean warming might affect their future spreading. We experimentally examined ecophysiological responses to the temperature range 23-31 °C in three invasive seaweeds commonly found in the Mediterranean: Acrothamnion preissii, Caulerpa cylindracea and Lophocladia lallemandii. The warming range tested encompassed current and projected (for the end of 21st Century) maximum temperatures for the Mediterranean Sea. Optimal ecophysiological temperatures for A. preissii, C. cylindracea and L. lallemandii were 25 °C, 27 °C and 29 °C, respectively. Warming below the optimal temperatures enhanced RGR of all studied invasive seaweeds. Although sensitive, seaweed photosynthetic yield was less temperature-dependent than growth. Our results demonstrate that temperature is a key environmental parameter in regulating the ecophysiological performance of these invasive seaweeds and that Mediterranean warming conditions may affect their invasion trajectory.

High tolerance to simulated herbivory in the clonal seaweed, Caulerpa cylindracea.

Tolerance can enable introduced plants to establish in the face of intense consumption by native herbivores. The siphonacous seaweed, Caulerpa cylindracea, despite being heavily grazed by native herbivores, is one of the most successful invaders in the Mediterranean. By means of a field experiment simulating herbivore grazing, we tested whether regeneration from damaged creeping stolons may allow C. cylindracea to compensate or overcompensate for biomass loss. In order to simulate different grazing intensities, the cover of C. cylindracea was either left untouched or clipped to 25%, 50% or 75% of the original value. After 2 months, C. cylindracea cover increased by ∼ 450% in 75% removal plots, ∼ 200% in 50% removals and ∼ 70% in 25% removals, whilst the increment in controls was just ∼ 6%. Such differential growth rates resulted in no difference in the cover of C. cylindracea between clipped (irrespective of clipping intensity) and control plots. Thus, regeneration from remnant clipped stolons could compensate for biomass loss, suggesting that non-native siphonaceous seaweeds can withstand intense mechanical damage and, possibly, grazing by herbivores. This compensatory mechanism may underpin the success of some of the most invasive clonal plants.

An intracellular transcriptomic atlas of the giant coenocyte Caulerpa taxifolia.

Convergent morphologies have arisen in plants multiple times. In non-vascular and vascular land plants, convergent morphology in the form of roots, stems, and leaves arose. The morphology of some green algae includes an anchoring holdfast, stipe, and leaf-like fronds. Such morphology occurs in the absence of multicellularity in the siphonous algae, which are single cells. Morphogenesis is separate from cellular division in the land plants, which although are multicellular, have been argued to exhibit properties similar to single celled organisms. Within the single, macroscopic cell of a siphonous alga, how are transcripts partitioned, and what can this tell us about the development of similar convergent structures in land plants? Here, we present a de novo assembled, intracellular transcriptomic atlas for the giant coenocyte Caulerpa taxifolia. Transcripts show a global, basal-apical pattern of distribution from the holdfast to the frond apex in which transcript identities roughly follow the flow of genetic information in the cell, transcription-to-translation. The analysis of the intersection of transcriptomic atlases of a land plant and Caulerpa suggests the recurrent recruitment of transcript accumulation patterns to organs over large evolutionary distances. Our results not only provide an intracellular atlas of transcript localization, but also demonstrate the contribution of transcript partitioning to morphology, independent from multicellularity, in plants.

Mechanisms influencing the spread of a native marine alga.

Like invasive macrophytes, some native macrophytes are spreading rapidly with consequences for community structure. There is evidence that the native alga Caulerpa filiformis is spreading along intertidal rocky shores in New South Wales, Australia, seemingly at the expense of native Sargassum spp. We experimentally investigated the role physical disturbance plays in the spread of C. filiformis and its possible consequences for Sargassum spp. Cleared patches within beds of C. filiformis (Caulerpa habitat) or Sargassum spp. (Sargassum habitat) at multiple sites showed that C. filiformis had significantly higher recruitment (via propagules) into its own habitat. The recruitment of Sargassum spp. to Caulerpa habitat was rare, possibly due in part to sediment accretion within Caulerpa habitat. Diversity of newly recruited epibiotic assemblages within Caulerpa habitat was significantly less than in Sargassum habitat. In addition, more C. filiformis than Sargassum spp. recruited to Sargassum habitat at some sites. On common boundaries between these two macroalgae, the vegetative growth of adjacent C. filiformis into cleared patches was significantly higher than for adjacent Sargassum spp. In both experiments, results were largely independent of the size of disturbance (clearing). Lastly, we used PAM fluorometry to show that the photosynthetic condition of Sargassum spp. fronds adjacent to C. filiformis was generally suppressed relative to those distant from C. filiformis. Thus, physical disturbance, combined with invasive traits (e.g. high levels of recruitment and vegetative growth) most likely facilitate the spread of C. filiformis, with the ramifications being lower epibiotic diversity and possibly reduced photosynthetic condition of co-occurring native macrophytes.

Effectiveness of the California state ban on the sale of Caulerpa species in aquarium retail stores in southern California.

The invasion of the aquarium strain of the green alga Caulerpa taxifolia and subsequent alteration of community structure in the Mediterranean Sea raised awareness of the potential for non-native seaweeds to impact coastal communities. An introduction of C. taxifolia in southern California in 2000, presumably from the release of aquarium specimens, cost ~$7 million for eradication efforts. Besides C. taxifolia, other Caulerpa species being sold for aquarium use also may have the potential to invade southern Californian and U.S. waters. Surveys of the availability of Caulerpa species in southern California aquarium retail stores in 2000-2001 revealed that 26 of 50 stores sold at least one Caulerpa species (52 %) with seven stores selling C. taxifolia. In late 2001, California imposed a ban on the importation, sale, or possession of nine Caulerpa species; the City of San Diego expanded these regulations to include the entire genus. To determine the effectiveness of the California ban, we resurveyed Caulerpa availability at 43 of the 50 previously sampled retail stores in southern California in ~2006, ~4 years following the ban. Of the 43 stores, 23 sold Caulerpa (53 %) with four stores selling C. taxifolia. A χ(2) test of frequency of availability before and after the California ban suggests that the ban has not been effective and that the aquarium trade continues to represent a potential vector for distributing Caulerpa specimens, including C. taxifolia. This study underscores the need for increased enforcement and outreach programs to increase awareness among the aquarium industry and aquarium hobbyists.

Physical factors contributing to the benthic dominance of the alga Caulerpa sertularioides (Caulerpaceae, Chlorophyta) in the upwelling Bahía Culebra, north Pacific of Costa Rica / Factores físicos que contribuyen a la dominancia bentónica del alga Caulerpa sertularioides (Caulerpaceae, Chlorophyta) en la surgencia Bahía Culebra, Pacífico norte de Costa Rica

Caulerpa sertularioides has been spreading in Bahía Culebra, a seasonal upwelling bay in the north Pacific of Costa Rica, since 2001. The survey was carried out from December 2003 to March 2005, in several locations around Bahía Culebra, located inside the Gulf of Papagayo. This study investigated spatial and temporal patterns, percent coverage, monthly growth rate, reproductive adaptations, and morphological variations of frond length and stolon diameter of Caulerpa sertularioides, at different environmental physical and chemical factors at the bay. The alga extended to depths of 23 m on a variety of substrates. The stolons extended quickly, with a maximum growth rate of 31.2 cm month-1. This alga grows mainly by fragmentation of its fronds and stolons; nevertheless it can also reproduce sexually by releasing gametes in the water column. These two modes of spreading promote the adaptation of this opportunistic species to environmental, chemical, and physical changes at this bay. At the same time the alga showed variations in the length of its fronds and stolons, adapting to conditions such as depth and season. Average percent cover and frond density increased during the dry season when the upwelling of nutrients and cold water occurs. In the rainy season the average percent cover and frond density decreased; however there was a peak in September, when high precipitation resulted in runoff into the bay of nutrient-rich waters. The morphological and physiological plasticity of C. sertularioides, in synergy with its predominant clonal propagation and sexual reproduction provided this species with a great adaptability to changes in temperature and nutrient concentration at Bahía Culebra.

Desde el 2001 se ha observado una propagación del alga verde Caulerpa sertularioides en Bahía Culebra, zona de afloramiento costero, en el Pacífico norte de Costa Rica. El muestreo se llevó acabo entre Diciembre 2003 a marzo 2005, en varias localidades de Bahía Culebra. En este estudio se presentan los patrones de distribución, cobertura, tasa mensual de crecimiento, adaptaciones reproductivas y variaciones morfológicas del largo de la fronda y diámetro del estolón de Caulerpa sertularioides, a diferentes factores ambientales físico-químicos en Bahía Culebra. Esta alga se extiende hasta profundidades de 23 m, en una gran variedad de sustratos. Los estolones se extienden rápidamente, con un crecimiento máximo de 31.2 cm mes-1. Esta alga se propaga principalmente por la fragmentación de sus frondas y estolones, así mismo se reproduce sexualmente liberando gametos a la columna de agua. Estos modos de reproducción promueven la adaptación de esta especie oportunista, a los cambios ambientales, tanto químicos, como físicos, de la bahía. Al mismo tiempo esta alga presenta variaciones en el largo de sus frondas y el diámetro del rizoma, adaptándose a diferentes profundidades y condiciones de la época del año. El porcentaje de cobertura y densidad de frondas aumentan durante la época seca, cuando emergen aguas frías y nutrientes por el afloramiento costero. Por otro lado, en la época lluviosa estas medidas decrecen, sin embargo se presenta un pico en setiembre, cuando la precipitación aumenta y llega una carga extra de nutrientes a la bahía por escorrentía. La plasticidad morfológica y fisiológica de C. sertularioides, en sinergia con su propagación clonal, proveen a esta alga con una gran adaptabilidad a los cambios en temperatura y nutrientes de Bahía Culebra.

Vulnerability of marine habitats to the invasive green alga Caulerpa racemosa var. cylindracea within a marine protected area.

The relative vulnerability of various habitat types to Caulerpa racemosa var. cylindracea invasion was investigated in the National Marine Park of Zakynthos (Ionian Sea, Greece). The density of C. racemosa fronds was modelled with generalized additive models for location, scale and shape (GAMLSS), based on an information theory approach. The species was present in as much as 33% of 748 randomly placed quadrats, which documents its aggressive establishment in the area. The probability of presence of the alga within randomly placed 20 x 20 cm quadrats was 83% on 'matte morte' (zones of fibrous remnants of a former Posidonia oceanica bed), 69% on rocky bottoms, 86% along the margins of P. oceanica meadows, 10% on sandy/muddy substrates, and 6% within P. oceanica meadows. The high frond density on 'matte morte' and rocky bottoms indicates their high vulnerability. The lowest frond density was observed within P. oceanica meadows. However, on the margins of P. oceanica meadows and within gaps in fragmented meadows relative high C. racemosa densities were observed. Such gaps within meadows represent spots of high vulnerability to C. racemosa invasion.

The role of benthic macrophytes and their associated macroinvertebrate community in coastal lagoon resistance to eutrophication.

Eutrophication is widely recognised as one of the major menaces to coastal environments, particularly enclosed bays and lagoons. Although there is a general understanding of the consequences of eutrophication in these systems, there is a lack of sufficient knowledge concerning biotic feedbacks that influence eutrophication patterns and the resistance capacity of coastal environments. In this paper, the isotope ratios of main producers and consumers of a Mediterranean lagoon were examined in order to elucidate the fate of anthropogenic inputs from the main watercourse flowing into the lagoon. The results of the study of stable isotope data in the Mar Menor lagoon reflected that the whole benthic community plays an important role as a natural 'filter' that removes excess nutrients from the water column and stores them in the sediments, thereby enhancing lagoon resistance to eutrophication.

Effects of irradiance and temperature on the photosynthesis and vegetative propagation of Caulerpa serrulata.

The photosynthetic oxygen evolution of Caulerpa serrulata was determined with oxygen electrodes. The effects of light and temperature on the growth and regeneration of fragmented C. serrulata thalli were analyzed. The regenerating rate and establishment of different sizes and portions of C. serrulata were studied. The results showed that the light saturation point of C. serrulata was 200 micromol photons/m(2) per s and the optimum growth temperature was 25-30 degrees C. Under these conditions, the maximum photosynthetic oxygen evolution rate was 15.1 +/- 0.29 mg O(2)/mg Chl a/h, the growth rate and elongation rate reached the highest values, 4.67 +/- 0.09 mg FW/d and 0.78 +/- 0.01 mm/d, respectively. The fragmented C. serrulata thalli was regenerated at 20-35 degrees C and survived at 15 degrees C and 200 micromol photons/m(2) per s. A different survival rate was detected according to fragment size. All of these results indicated that C. serrulata was a candidate to become an invasive species if introduced into a new place. Therefore, we should pay more attention to C. serrulata for its potential threat to marine ecosystem when it is sold for aquarium use.

Competition between the invasive macrophyte Caulerpa taxifolia and the seagrass Posidonia oceanica: contrasting strategies.

BACKGROUND: Plant defense strategy is usually a result of trade-offs between growth and differentiation (i.e. Optimal Defense Theory--ODT, Growth Differentiation Balance hypothesis--GDB, Plant Apparency Theory--PAT). Interaction between the introduced green alga Caulerpa taxifolia and the endemic seagrass Posidonia oceanica in the Mediterranean Sea offers the opportunity to investigate the plausibility of these theories. We have accordingly investigated defense metabolite content and growth year-round, on the basis of an interaction gradient. RESULTS: When in competition with P. oceanica, C. taxifolia exhibits increased frond length and decreased Caulerpenyne--CYN content (major terpene compound). In contrast, the length of P. oceanica leaves decreases when in competition with C. taxifolia. However, the turnover is faster, resulting in a reduction of leaf longevity and an increase on the number of leaves produced per year. The primary production is therefore enhanced by the presence of C. taxifolia. While the overall concentration of phenolic compounds does not decline, there is an increase in some phenolic compounds (including ferulic acid and a methyl 12-acetoxyricinoleate) and the density of tannin cells. CONCLUSION: Interference between these two species determines the reaction of both, confirming that they compete for space and/or resources. C. taxifolia invests in growth rather than in chemical defense, more or less matching the assumptions of the ODT and/or PAT theories. In contrast, P. oceanica apparently invests in defense rather than growth, as predicted by the GDB hypothesis. However, on the basis of closer scrutiny of our results, the possibility that P. oceanica is successful in finding a compromise between more growth and more defense cannot be ruled out.

[Investigation and culture of microbial contaminants of Caulerpa lentillifera (Sea Grape)].

Caulerpa lentillifera is a kind of edible seaweed, known as 'sea grape' or 'green caviar'. It is used in fresh salads. However, it is sensitive to low temperature and osmotic pressure, and is easily spoilt by storage in a refrigerator or washing with tap water. That is the reason why it is difficult to prevent food poisoning, especially due to Vibrio parahaemolyticus. In this study we investigated of marine bacteria and V. parahaemolyticus in C. lentillifera and cultured them in order to develop effective control of bacteria in commercial farms. The sixteen farms in the Okinawa Islands were investigated from August to September in 2006. A total of 176 samples were collected from eleven points during the cultivation processes and from the products. About 10(3) cfu/mL of marine bacteria were detected in the seawater used in the tank culture, but after cultivation of C. lentillifera the number had increased to about 10(6) cfu/mL. The number of marine bacteria in C. lentillifera did not change significantly through the process of planting to the final product (about 10(7) cfu/g). V. parahaemolyticus was detected in seawater from all processes and C. lentillifera was isolated from 56% of seawater, 25% of seed-stocks, and 18.8% of product samples, though but thermostable direct hemolysin gene was not detected from enrichment cultures or isolated V. parahaemolyticus strains. These results indicate that for prevention of food poisoning by V. parahaemolyticus in C. lentillifera, it is important to establish a suitable sterilization procedure for each process.

First assessment of the Caulerpa racemosa (Caulerpales, Chlorophyta) invasion along the French Mediterranean coast.

The introduced green alga Caulerpa racemosa var. cylindracea has been rapidly spreading in the Mediterranean Sea since 1990. It was first observed in France in 1997 (Marseilles). In early 2004, the stretch of the French Mediterranean coastline and the surface area affected by the invasion were estimated at about 83 km and 4014 ha, respectively. The depth range of colonized areas was usually 10-35 m depth. Shallow (0-10 m) and deep (down to 40 m) dense meadows were rarely observed. In contrast to the dead matte of Posidonia oceanica, which constituted the most widely colonized substratum, dense P. oceanica meadows and fine sand with large ripple-marks were not invaded. Few rocky areas were colonized and coarse sand bottoms were usually colonized below 20 m depth. All the colonized areas were exposed to human activities and more than 40% were fishing areas. Mild climate, suitable substrata, presence of vectors of dispersal and absence of efficient biological control make the French Mediterranean coast particularly vulnerable to the further spread of the alga.