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Accounting for the diversity of photosynthetic eukaryotes is an important challenge in microbial biology. It has now become clear that endosymbiosis explains the origin of the photosynthetic organelle (plastid) in different algal groups. The first plastid originated from a primary endosymbiosis, whereby a previously non-photosynthetic protist engulfed and enslaved a cyanobacterium. This alga then gave rise to the red, green, and glaucophyte lineages. Algae such as the chlorophyll -containing chromists gained their plastid through secondary endosymbiosis, in which an existing eukaryotic alga (in this case, a rhodophyte) was engulfed. Another chlorophyll -containing algal group, the dinoflagellates, is a member of the alveolates that is postulated to be sister to chromists. The plastid in these algae has followed a radically different path of evolution. The peridinin-containing dinoflagellates underwent an unprecedented level of plastid genome reduction with the ca. 16 remaining genes encoded on 1–3 gene minicircles. In this short review, we examine algal plastid diversity using phylogenetic and genomic methods and show endosymbiosis to be a major force in algal evolution. In particular, we focus on the evolution of targeting signals that facilitate the import of nuclear-encoded photosynthetic proteins into the plastid.

Genetic responses of the seaweed to pine needle ash have been compared using differential display technique. The tissue viability was assessed to evaluate the stress level with triphenyltetrazolium chloride. Total RNA, from tissues treated in seawater containing ash, was reverse transcribed and amplified by PCR with arbitrary primers. The genetic fragments responding to the stress were selectively isolated from agarose gel and sequenced with a DNA auto sequencer. According to sequence analysis, an ash-inducible gene (342 bp) and an ash-suppressed gene (1690 bp) were identified as hypothetical proteins.

Gametogenesis of thalli is induced by ageing as well as by changing water temperature and photoperiod. Under laboratory conditions, thalli cultivated at 10 °C with a 10:14 h (light: dark) cycle develop vegetatively to adult form without gametogenesis. On the other hand, sexual reproduction, which involves differentiation of vegetative cells and subsequent gametogenesis, is induced by culturing at 15 °C with a 16: 8 h (light: dark) cycle. We have constructed subtracted cDNA libraries enriched for differentially expressed transcripts in vegetative and reproductive thalli, and randomly selected 1,152 cDNAs from each subtracted library. Results of the dot blot analyses used for identification of differentially expressed cDNAs indicated that mRNA levels of 176 and 138 cDNAs tended to increase in the vegetative and reproductive thalli, respectively. BLAST analysis of nucleotide and deduced amino acid sequences showed that the cDNAs represented 63 and 59 unique clones for the vegetative and reproductive cDNA enriched subtracted libraries, respectively. Interestingly, some of the cDNAs isolated from the reproductive subtracted library were homologous to genes encoding protein kinases, GTP-binding protein, and heat shock proteins involved in signal transduction and the molecular chaperon system.

Mediterranean reports of Gracilariaceae species, in particular those assigned to the complex, were re-examined with the use of molecular tools, in order to verify their systematic position and better understand their distribution. Within this complex, we recognized four distinct taxa: and a possible new species. The L gene sequences, together with those of other terete Mediterranean entities, were included in a broad molecular phylogeny of the family. The reproductive characters of the studied taxa do not fit completely with published hypothesis on the generic and intrageneric relationships, suggesting that the anatomy of some subgroups should be better characterized.

This is the first study on the south eastern Pacific coast of South America which details long term, interannual variability in the structure of subtidal rocky-bottom kelp-dominated communities before, during, and after the El Niño Southern Oscillation (ENSO) event of 1997–1998 in northern Chile (23°S). The temporal patterns of the main components of these ecosystems, which included , echinoids and asteroids, were evaluated seasonally between 1996 and 2004. demonstrated high interannual variability in temporal patterns of abundance. The 1997–1998 ENSO did not significantly modify the temporal patterns of , although local extinction of beds occurred during negative thermal anomalies in 1999–2000 (La Niña event), facilitating the establishment of urchin dominated “barren grounds”. The abundance of showed little temporal variability, and this species dominated the deeper regions of the kelp assemblage (8–13m depth).

The structure of the kelp communities in the study area is regulated by a trophic cascade which modulates alternation between kelp dominated areas and sea urchin barrens. In this context, frequent and intense upwelling of cold water high in nutrients favors the establishment and persistence of kelp assemblages. During ENSO, coastal upwellings can mitigate superficial warming of coastal water and increase the nutrient concentration in the water column. Superficial warming during the 1997–1998 ENSO induced spawning by different species of echinoderms, which resulted in major recruitment of these species during 1999. Top-down events, such as the decrease in densities of the asteroids after the 1997–1998 ENSO event, favored increases in densities of benthic grazers, which caused significant decreases in abundance of . The re-establishment of the adult fraction of the carnivore (starfish) guild coincided with a decrease in the density of sea urchins and thus re-establishment of the kelp. In the temperate south eastern Pacific, oceanographic events, which act on different spatial-temporal scales, trigger trophic cascades that act at local levels, producing interannual variability in the structure of kelp communities. On the other hand, considering the high macroinvertebrate diversity associated with kelp assemblages, the transitions between kelp-dominated areas and sea urchin barrens do not appear to significantly affect the biodiversity of these assemblages of benthic invertebrates.

The Cape Ohma region of Shimokita Peninsula, the northernmost point of Honshu Island, Japan, is subject to both the warm Tsugaru Current and the cold Kurile Current. As a result, the Laminarialean flora includes both cold temperature species ( Areschoug, Miyabe and (C. Agardh) Saunders) andwarm temperature species ( (Kjellman) Okamura, Okamura), as well as (Yendo) Okamura, which is distributed in both waters. The frequency of occurrence (as a measure of distribution) and the biomass of these species were recorded in June 1976 (at 50 points in depths between 8–30 m), July 1988 (192 points, 2.5–25 m) and July 2001 (78 points, 2.5–25 m). Comparison of these data revealed a decrease in cold temperature species and an increase in warm temperature species from 1976 or 1988 to 2001. Long-term data of seawater temperature measured at 5 m depth near the study site showed that mean temperatures in the middle of winter (late January to February) in 1989–2000 were 0.9–1.1 °C higher than those in 1980-1988. Higher seawater temperatures in the last decade appear to have affected the frequency of occurrence and biomass of the Laminarialean species along the coasts of Cape Ohma. This result supported our previous conclusion that 1 °C higher mean seawater temperature in late January caused a decrease in the biomass of (by ca. 64%) along the same coast.

Introductions of non-indigenous species to new ecosystems are one of the major threats to biodiversity, ecosystem functions and services. Globally, species introductions may lead to biotic homogenisation, in synergy with other anthropogenic disturbances such as climate change and coastal pollution. Successful marine introductions depend on (1) presence of a transport vector, uptake of propagules and journey survival of the species; (2) suitable environmental conditions in the receiving habitat; and (3) biological traits of the invader to facilitate establishment. Knowledge has improved of the distribution, biology and ecology of high profile seaweed invaders, e.g. ssp. , and . Limited, regional information is available for less conspicuous species. The mechanisms of seaweed introductions are little understood as research on introduced seaweeds has been mostly reactive, following discoveries of introductions. Sources of introductions mostly cannot be determined with certainty apart from those directly associated with aquaculture activities and few studies have addressed the sometimes serious ecological and economic impacts of seaweed introductions. Future research needs to elucidate the invasion process, interactions between invaders, and impacts of introductions to support prevention and management of seaweed introductions.

The Gulf of California, considered one of the most pristine areas of the world, hosts more than 50 seaweed species that have commercial applications. Only one species, however, is presently harvested commercially. In order to establish potential areas for seaweed use, a Geographical Information System (GIS) was used to determine areas for potential seaweed exploitation based on more than 9000 literature records. The system allows for the determination of sites, areas and times of the year when commercial species may be available. This information is being considered in a zoning program that would determine the areas of the Gulf sustainable for use or conservation. Temperature data were also included in order to determine potential areas for seaweed cultivation. GIS proves to be a powerful tool for large-scale management of seaweed resources.

The reproductive phenology of and the effects of temperature and light on its growth were examined in Cheongsapo near Busan, Korea, from September 1994 to August 1995. The vegetative plants dominated over the year, with a peak occurrence in January. Gameto- and tetrasporophytes were most abundant in November and August. All vegetative and reproductive plants had a peak both in length and weight in October, when seawater temperature was highest (24 °C). In laboratory culture, the maximum relative growth rate (RGR) of 2.94% day was obtained at 20 °C and 100mol photons m s, whereas the lowest value was recorded at 25 °C and 100 mol photons m s in a 12: 12 h LD photoperiod regime. Among the three photoperiod regimes (8:16 h, 12:12 h, 16:8 h LD) tested, there was evidence of a higher RGR in the 12:12 h LD cycle. This result suggests that the growth and reproduction of are correlated with the seawater temperature based on laboratory culture and field observations.

A free-floating, loose form of (Huds.) Lamour is rare in the Baltic Sea area. Kassari Bay, situated in the West Estonian Archipelago Sea area contains the largest known community of this kind. Here the free-floating mixed (Paela) M. J. Wynne et J. N. Heine community inhabits sandy bottom, covering up to 120 km. Commercial exploitation of the community started in 1966 and has led to regular monitoring surveys for the quantification of the commercial resource. The aim of the present study was to determine the potential growth rates of the two community-forming species as well as to test different environmental factors affecting their growth. Results showed that the highest growth rates were measured in shallower depths (4 m) for both species. The seasonal growth pattern was also very similar for both species, showing the highest growth rates during the beginning of summer. Incubation of both species in another sea area with apparently similar basic environmental conditions (the northern part of the Gulf of Riga, Kõiguste Bay) resulted in significantly lower growth rates during the whole incubation period.