E. A. Titlyanov

Photo-acclimation dynamics of the coral Stylophora pistillata to low and extremely low light

Abstract Photo-acclimation dynamics of the symbiotic coral Stylophora pistillata to lowering light intensities in the range of 95% to 0.8% of incident surface photosynthetic active radiation (PAR0) was studied. Coral colonies were sampled from 1- to 2-m depths in open and shaded habitats from the fringing reef of Sesoko Island (near the Tropical Biosphere Research Center, University of the Ryukyus) Okinawa, Japan. Photo-acclimation of exterior branches of coral colonies were examined in outdoor aquarium, where light regime and feeding were similar to field conditions. Two photo-acclimation reactions were studied: (1) changes in chlorophyll concentrations in zooxanthellae; (2) changes in zooxanthellar population density in coral branches. In parallel, we measured an average volume of zooxanthellae, proliferating zooxanthellae frequency (PZF) and degrading zooxanthellae frequency (DZF). It was shown that the coral S. pistillata can survive and acclimate to a wide range of light intensities from 95% to 0.8% PAR0. Acclimation to low light (30% and 8% PAR0) involves maximizing the light harvesting capacity by increasing photosynthetic pigment concentration in zooxanthellae and zooxanthellar population density in coral branches. Under extremely low light (0.8% PAR0), the coral lost zooxanthellae by degradation (perhaps digestion) and retained zooxanthellae-accumulated high concentrations of chlorophyll. The photo-acclimation process is dynamic and immediate. Changes in pigment concentrations in zooxanthellae occurred within 2–4 days and changes in zooxanthellar population densities occurred within 40 days. Zooxanthellae population densities were regulated by changes in rates of division and degradation of symbiotic cells.

Photo-acclimation of the hermatypic coral Stylophora pistillata while subjected to either starvation or food provisioning.

This study investigated the photo-acclimation capacity of the coral Stylophora pistillata (Esper). Outer branches of coral colonies, taken from 2 m, were subjected to 90, 20, or 3% of incident surface photosynthetic active radiation (PAR(0)), or kept in total darkness. The corals were maintained either in filtered seawater (i.e., under starvation), or in seawater that had daily additions of zooplankton (rotifers). The experiments were maintained for 31 days. Zooxanthellae population densities and chlorophyll concentrations increased in S. pistillata fragments subjected to 20 and 3% PAR(0). The zooxanthellae densities decreased after 6 days in corals kept in total darkness, although chlorophyll concentrations remained higher. Corals that were fed and subjected to 90% PAR(0) showed lower degrading zooxanthellae frequencies, higher photosynthetic and respiration rates, and higher chlorophyll concentrations than corals in the same light regime under starvation. Complete acclimation to dim (20% PAR(0)) and low (3% PAR(0)) light was only apparent for corals fed with zooplankton. Changes in zooxanthellae population densities occurred through differential rates of zooxanthellae division and degradation.

Fatty acid variations in symbiotic dinoflagellates from Okinawan corals

The fatty acid composition of polar lipids and triacylglycerols was determined in different morphophysiological types of symbiotic dinoflagellates (SD) isolated from the hydrocoral Millepora intricata and the scleractinian corals Pocillopora damicornis, Seriatopora caliendrum, Seriatopora hystrix and Stylophora pistillata from a fringing reef of Sesoko Island, Okinawa, Japan. The distribution of the fatty acids among the morphophysiologically distinct types of SD reported in these corals makes it possible to readily distinguish one type of SD from the other. Moreover, differences were found both in polar lipids and triacylglycerols. The polar lipids of SD from M. intricata showed a very distinctive fatty acid profile. A combination of large proportions of 18:4 (n-3), 18:5 (n-3), 22:5 (n-6), and 22:6 (n-3) and negligible amounts of 20:4 (n-6), and 20:5 (n-3) in SD from M. intricata was particularly noteworthy. The fatty acid profiles of SD from P. damicornis and SD isolated from S. caliendrum and S. hystrix differed in the proportion of 18:4 (n-3) and 22:6 (n-3). It is suggested that fatty acids might provide useful information on possible taxonomic differences among symbiotic dinoflagellates. It is assumed that biochemical differences can reflect the genetic diversity of the morphophysiological types of SD associated with several species of hermatypic corals from this region.

Effect of light intensity on the fatty acid composition of dinoflagellates symbiotic with hermatypic corals

Abstract We examined the effects of varying light intensity on fatty acid composition in symbiotic dinoflagellates (SD) isolated from hermatypic corals Millepora intricata, Pocillopora damicornis, Seriatopora caliendrum, Seriatopora hystrix and Stylophora pistillata. The corals were subjected to 95%, 30%, 8% and 2% of incident photosynthetic active radiation (PAR). Irradiance had a significant effect on fatty acid composition of polar lipids and triacylglycerols. SD showed substantial changes in the proportion of 16:0 as a response to variation in PAR. During adaptation to high light, the percentage of 16:0 increased in polar lipids and triacylglycerols. Additionally, the percentage of 14:0, 16:1(n-7) increased in triacylglycerols. Thus, high light conditions lead to an increase in storage products. Polar lipids of SD adapted to low levels of PAR had greater concentrations of 18:4(n-3), 20:5(n-3), 18:5(n-3) and 22:5(n-6) which are commonly involved in the formation of thylakoid membranes. Conversely, the amounts of 20:4(n-6) and 22:6(n-3) increased with increasing irradiance, suggesting an association with photosynthesis. The elevation in percentages of 18:4(n-3), 20:5(n-3) and 18:5(n-3) during exposure to low light was accompanied by an increase in chlorophyll a content in the SD cells. Light-dependent changes in fatty acid composition are probably due to the correlation of activity of photosystems with processes of production and desaturation of fatty acids.

Obtaining plantlets from apical meristem of the red alga Gelidium sp.

For the first time, plantlets were obtained from fragments and cell aggregates (CA) of apical meristem of the red alga Gelidium sp. After two months of cultivation, an initial weight of 100 mg of fragments and CA from fresh meristem produced 3 g of plantlets without rhizoids. During the same period of cultivation, 100 mg of meristem fragments and CA isolated from thalli by the freezing-thawing procedure produced more than 20 g of plantlets with rhizoids. It is assumed that our methods for obtaining plantlets from fragments and CA of fresh and frozen-thawed meristem could be used to generate mass planting material for cultivation of algae (plantlets with rhizoids) in the sea and for tank-bubbling cultivation (plantlets without rhizoids). We speculate that meristem cells of frozen-thawed algae might be natural “seedstock” in the Arctic and Antarctic seas.

Circadian rhythm of photosynthesis in Kappaphycus alvarezii (Rhodophyta): independence of the cell cycle and possible photosynthetic clock targets

Various processes in the output pathway of the circadian clock are thought to act as important clock targets resulting in the circadian rhythms of photosynthesis observed in various algae. Examples of such processes are synchronization of the cell cycle, pigmentation, and light or dark reaction of photosynthesis. The newly detected, robust photosynthetic circadian rhythm in the red macroalga Kappaphycus alvarezii was investigated in more detail with respect to rhythmically changing components within the photosynthetic apparatus. The following major results were obtained; (1) The growing tips of Kappaphycus (0–2 cm) were found to exhibit a diurnal and circadian rhythm of nuclear division like many other algal species, (2) The circadian photosynthetic rhythm was apparent in the actively growing and dividing tip portions (0–;2 cm) as well as in older portions (2–4 cm) with little remaining mitotic activity. The Kappaphycus rhythm seems therefore to be independent of the cell cycle, at least in the older portions of the thallus, (3) During real (L:D cycle) or subjective (LL) dark phases, net photosynthetic capacity (Pmax) dropped drastically in young (tip) parts of the thallus, and α, the ‘light affinity’ parameter, decreased likewise. The net result of these two changes was an increase in the light saturation point, Ek. Dark respiration did not change rhythmically from one circadian maximum to the next circadian minimum. ΔF/Fm′ dropped during real and subjective night phases, while non-photochemical quenching (NPQ) increased. Low temperature (77 K) emission spectra with an excitation wavelength of 580 nm exhibited a larger increase of the 720:685 nm as well as the 720:696 nm emission quotients compared with spectra at 440 nm excitation for samples harvested in the middle of the subjective dark phase indicating changes in energy trapping from the phycobilisomes to the photosystems.

Checklist of marine benthic green algae (Chlorophyta) on Hainan, a subtropical island off the coast of China: comparisons between the 1930s and 1990-2009 reveal environmental changes

Abstract A complete checklist of intertidal to shallow subtidal marine green seaweeds (Chlorophyta) growing on the subtropical island of Hainan (China) is presented here for the first time. It covers data from extensive recent (1990–2009) and historical (1933–1935) collections, and additional published records from various time periods. Data were analyzed by time period. We postulate that environmental changes on Hainan Island documented since the 1980s (e.g., degradation of coral reefs, development of tourism and mariculture farms) are reflected in the green algal species complement and in the dominance or absence of specific algal groups during different time periods. In total, 105 green algal taxa were recorded, including 37 new to Hainan Island, and 18 new records for China. There was a clearly evident change in floristic composition between early and recent collections. In the 1930s, there was a dominance of Caulerpaceae, Codiaceae and Cladophoraceae. By 1990/1992, the numbers of Ulvaceae had increased 1.6-fold and numbers of Cladophoraceae 1.7-fold. Both families contain many opportunistic species that prefer nutrient-enriched or degraded environments. At the same time, species richness of Codiaceae, Caulerpaceae and Udotaceae, families with complex thallus structures, decreased considerably. The floristic differences between the 1990/1992 and 2008/2009 collections were minor.

Stocks and the use of economic marine macrophytes of Vietnam

This review analyzes the literature and original data on the resources, use, and cultivation of useful marine macrophytes in Vietnam. Information is provided about more than 60 species of macroalgae: including 41 species of Rhodophyta, 15 species of Heterokontophyta and 7 species of Chlorophyta. Out of these, more than 50 species are used for food, about 20 species are used in folk medicine, and more than 30 species are important commercial sources of polysaccharides (agar, carrageenan, and alginates); Sargassum, Gracilaria, and Kappaphycus are exported (mainly to China). The wild stocks of useful algae in Vietnam are declining as a result of their uncontrolled export (especially Sargassaceae). Several species of Gracilaria and Kappaphycus are commercially cultivated and also exported.

Inventory change (1990s–2010s) in the marine flora of Sanya Bay (Hainan Island, China)

Sanya Bay lies at the southern part of Hainan Island, 18°15′N 109°28′E. The seawater in the bay has been catastrophically polluted during the past two decades with urban sewage from the rapidly developing Sanya City. The marine flora research in Sanya Bay was started at the beginning of the 1930s and the most detailed studies were performed by two German-Chinese expeditions in 1990 (October–December) and in 1992 (March–April). In April, October, November and December 2008–2010 the marine flora of Sanya Bay was studied by the authors at three localities: Luhuitou Peninsula, Xiaodong Hai and Dadong Hai. Marine algae were sampled in the intertidal and upper subtidal zones (to 4–5xa0m depth). The list of species (including varieties and forms) of the marine algae for Sanya Bay sampled during the period from 2008 to 2010 is compared with those collected at the same localities in 1990/1992. Comparative analysis of the floristic composition of the marine red, brown and green algae (found during different time periods) revealed that considerable changes have taken place between 1990/1992 and 2008–2010 at Sanya Bay. There was an increase in filamentous, tubular and fine blade-like green and red algae (mainly epiphytes with a high surface to volume ratio) and a displacement of upright-growing fleshy, foliose and other large green, brown and red algae with a low surface to volume ratio. It is assumed that the changes reflect mainly increased pollution by urban sewage and mariculture pond wastes and probably by coral bleaching events of 1998.

New records of benthic marine green algae (Chlorophyta) for the island of Hainan (China)

The island of Hainan (China) is located on the northern periphery of the subtropical Pacific Ocean in the South China Sea and possesses one of the most prominent fringing coral reefs of China. The marine algal flora of the island was described for the first time after several early expeditions in the 1930s (and around 1960) mentioning 68 species of marine green algae (Chlorophyta) in total. Sixty years later, the island was revisited in autumn 1990 and spring 1992 within in the framework of two extensive expeditions in order to scrutinise the algal biodiversity of the coral reef habitats. Again 20 years later, three more surveys were performed in 2008, 2009 and 2010 focusing only on the southern shores of Hainan Island near Sanya city. The analysis of this material revealed the existence of 31 new records of marine green algae for Hainan Island, including 17 species which also constitute new records for China. The new records are described and characteristic details are depicted. Collection sites around Hainan Island and world-wide distributions are given. Thirteen newly recorded species were only sampled once and therefore seem to be rare. Thirteen other species are pre-dominantly epiphytic or endophytic. The new records for China are fairly typical for tropical to subtropical locations of south-western to south-eastern Asia, except Chlorochytrium cohnii (distribution hitherto restricted to Europe). Chaetomorpha minima (distribution hitherto restricted to North and Central America, Africa, Indian Ocean islands) and Cladophora perpusilla (distribution hitherto restricted to Central and South America, Australia, New Zealand, Pacific islands). None of the new records are considered to represent an invasive species.