Márcio Murilo Barboza Tenório

Bio-optical properties of the marine cyanobacteria Trichodesmium spp.

Bio-optical spectral properties were determined on fresh suspensions of Trichodesmium spp. collected in a tropical lagoon and put in seawater tanks (total chlorophyll concentrations range between 0.1 and 3.8 mg m -3). The spectrum of the backscattering coefficient was a hyperbolic function with a slope of 1.2, often showing troughs at 440, 550 and 676 nm, due to absorption peaks of chlorophyll and phycoerythrin. The absorption spectrum computed with a specific beta correction for Trichodesmium, showed a blue to red ratio (B/R) equivalent to the one of a single colony (B/R=2), and also showed the double peak of mycosporine-like amino acids (MAAs, 330 and 360 nm). The CDOM absorption spectrum showed minor MAA peaks when cyanobacterial concentrations were above 1 mg Chl a m -3. The chlorophyll a-specific backscattering and absorption coefficients at 442 nm were respectively 0.0126 m 2 (mg.chl a) -1 and 0.027 m 2 (mg chl a) -1. Suspensions in tanks exhibited a high backscattering ratio at 660 nm (b˜ b=b bp/b p). The above-water reflectance spectrum clearly showed troughs at the wavelength of the pigment absorption peaks. Datasets of Trichodesmium normalized absorption, backscattering and reflectance spectra will allow its detection with future hyperspectral ocean colour sensors.

Chlorophylls and Phycoerythrins as Markers of Environmental Forcings Including Cyclone Erica Effect (March 2003) on Phytoplankton in the Southwest Lagoon of New Caledonia and Oceanic Adjacent Area

Spatio-temporal variations of chlorophylls and phycoerythrins, inferred by spectrofluorometric methods, were studied from April 2002 to June 2003 in the southwest lagoon and oceanic waters of New Caledonia. Trade winds blew 75% of the time and appeared as the main factor influencing surface Tchl (sum of monovinyl- and divinyl-chlorophyll ) variations in the ocean, near the barrier reef. Lagoon and oceanic waters differed in the composition of picoplanktonic cyanobacteria with a relative dominance of Prochlorococcus and high-phycourobilin Synechococcus in the ocean, and a relative dominance of high-phycoerythrobilin Synechococcus in the lagoon. Main pigment variations in the lagoon were associated with cyclone Erica in March 2003 and showed a 5-6 fold Tchl increase around Noumea. The cyclone stimulated mainly diatom growth as indicated by the high chlorophyll ()/chlorophyll ratio and by the lowest values for the other pigment ratios. The relative importance of divinyl-chlorophyll concentration and fluorescence excitation spectra of phycoerythrins appeared as useful tools for characterizing lagoon-ocean exchanges.

Taxonomic and Functional Metagenomic Signature of Turfs in the Abrolhos Reef System (Brazil)

Turfs are widespread assemblages (consisting of microbes and algae) that inhabit reef systems. They are the most abundant benthic component in the Abrolhos reef system (Brazil), representing greater than half the coverage of the entire benthic community. Their presence is associated with a reduction in three-dimensional coral reef complexity and decreases the habitats available for reef biodiversity. Despite their importance, the taxonomic and functional diversity of turfs remain unclear. We performed a metagenomics and pigments profile characterization of turfs from the Abrolhos reefs. Turf microbiome primarily encompassed Proteobacteria (mean 40.57% ± s.d. 10.36, N = 1.548,192), Cyanobacteria (mean 35.04% ± s.d. 15.5, N = 1.337,196), and Bacteroidetes (mean 11.12% ± s.d. 4.25, N = 424,185). Oxygenic and anoxygenic phototrophs, chemolithotrophs, and aerobic anoxygenic phototrophic (AANP) bacteria showed a conserved functional trait of the turf microbiomes. Genes associated with oxygenic photosynthesis, AANP, sulfur cycle (S oxidation, and DMSP consumption), and nitrogen metabolism (N2 fixation, ammonia assimilation, dissimilatory nitrate and nitrite ammonification) were found in the turf microbiomes. Principal component analyses of the most abundant taxa and functions showed that turf microbiomes differ from the other major Abrolhos benthic microbiomes (i.e., corals and rhodoliths) and seawater. Taken together, these features suggest that turfs have a homogeneous functional core across the Abrolhos Bank, which holds diverse microbial guilds when comparing with other benthic organisms.

Characterization of the photosynthetic conditions and pigment profiles of the colour strains of Hypnea musciformis from field-collected and in vitro cultured samples

Hypnea musciformis (Wulfen) JV Lamour. is a species of great economic interest as it produces Κ-carrageenan and has shown biological activities against HIV and HSV viruses. This species displays different colour strains in its natural habitat, which may have implications for the biotechnological potential of the species. The aim of this study was to characterize the photosynthetic apparatus and pigment profile of three colour strains of H. musciformis (green, brown and red) in their natural habitat and in culture. Chlorophyll a fluorescence of photosystem II was measured with a pulse-amplitude modulated fluorometer and pigments were quantified by spectrofluorimetry (chlorophyll a) and spectrophotometry (phycobiliproteins). In the natural habitat, we detected significant differences between the colour strains for the following photochemical parameters: the green strain had a higher effective quantum yield (ΦPSII) than the red strain and a higher maximum relative electron transport rate (rETRmax) than the brown and red strains. Saturation irradiances were 1000 µE.m-2.s-1 (green) and 500 µE.m-2.s-1 (brown and red). Concerning in vitro culture, the green strain presented the lowest ΦPSII, rETRmax, and α rETR, while the brown strain presented the highest values for these same parameters. The chlorophyll a content of the cultured green strain was the lowest. The phycoerythrin contents of the three colour strains were unchanged by either natural of in vitro conditions: lower in green, intermediate in brown and higher in the red strain, ensuring the chromatic identity of the strains. Our results suggest that the green strain has a better performance when exposed to high irradiance, but a lower efficiency under low irradiance compared to the brown and red strains.

SIZE-FRACTION, TROPHIC CATEGORIES AND MORPHOTYPES STRUCTURE OF PLANKTON SMALLER THAN 20 ¼m DURING THE AUSTRAL SUMMER (ADMIRALTY BAY, KING GEORGE ISLAND, WAP)

e density and distribution of plankton community smaller than 20 μm in Admiralty Bay (King George Island, Antarctica) were studied at three sampling sites during the austral summer of 2013/2014 (two surveys at the beginning – early summer, two at the end – late summer). e aim was to identify the environmental factors that in uence their variability. Salinity (34.2 ± 0.1) and temperature (0.47 ± 0.24°C) showed little variation in late summer, but in general, the concentration of dissolved nutrients increased towards this period. Organisms smaller than 10μm showed the higher contribution (74%) for Chlorophyll a concentration. Picoplankton (<2 μm), dominated by basically heterotrophs (98.5%), had density of 3.9 ± 1.8 x108 cell L-1. e fraction between 2 and 20 μm, dominated by autotrophs (60%), presented densities up to 3.6 ± 1.2 x106 cell L-1. is community was dominated by cocci and spherical morphotypes. Our results suggest that: (i) cell density increase along the study period followed nutrient and organic matter inputs; (ii) lower densities relative to 2009-2011 summers were related to lower temperatures and melting rates, besides predation forces, demonstrating the complex spatial-temporal relationships that take place between plankton community and environmental parameters at Admiralty Bay coastal zone.