A methodology for parameter estimation in seaweed productivity modelling

This paper presents a combined approach for parameter estimation in models of primary production. The focus is on gross primary production and nutrient assimilation by seaweeds. A database of productivity determinations, biomass and mortality measurements and nutrient uptake rates obtained over one year for Gelidium sesquipedale in the Atlantic Ocean off Portugal has been used. Annual productivity was estimated by harvesting methods, and empirical relationships using mortality/ wave energy and respiration rates have been derived to correct for losses and to convert the estimates to gross production. In situ determinations of productivity have been combined with data on the light climate (radiation periods, intensity, mean turbidity) to give daily and annual productivity estimates. The theoretical nutrient uptake calculated using a 'Redfield ratio' approach and determinations of in situ N and P consumption by the algae during incubation periods have also been compared. The results of the biomass difference and incubation approaches are discussed in order to assess the utility of coefficients determined in situ for parameter estimation in seaweed production models

Profiling the transcriptome of Gracilaria changii (Rhodophyta) in response to light deprivation

Light regulates photosynthesis, growth and reproduction, yield and properties of phycocolloids, and starch contents in seaweeds. Despite its importance as an environmental cue that regulates many developmental, physiological, and biochemical processes, the network of genes involved during light deprivation are obscure. In this study, we profiled the transcriptome of Gracilaria changii at two different irradiance levels using a cDNA microarray containing more than 3,000 cDNA probes. Microarray analysis revealed that 93 and 105 genes were up- and down-regulated more than 3-fold under light deprivation, respectively. However, only 50% of the transcripts have significant matches to the nonredundant peptide sequences in the database. The transcripts that accumulated under light deprivation include vanadium chloroperoxidase, thioredoxin, ferredoxin component, and reduced nicotinamide adenine dinucleotide dehydrogenase. Among the genes that were down-regulated under light deprivation were genes encoding light harvesting protein, light harvesting complex I, phycobilisome 7.8 kDa linker polypeptide, low molecular weight early light-inducible protein, and vanadium bromoperoxidase. Our findings also provided important clues to the functions of many unknown sequences that could not be annotated using sequence comparison

ELECTRONIC SPECTROSCOPY OF RARE GAS ISOLATED I2I_{2} AND IBr

Work supported by AFOSR under grant 85-0210Author Institution: Department of Chemistry, Enory UniversityThe electronic spectroscopy of $I_{2}$ and IBr, isolated in solid rare gas matrices has been studied using time and wavelength resolved fluorescence techniques. Argon isolated $I_{2}$, excited at a wavelength of 193 nm, showed a broad feature at about 380 nm, that has a very short life-time (= 20 ns). This transition has been tentatively assigned as the $D(^{3}\Pi_{2g})-A(^{3}\Pi_{2u})$ system. Ar, Kr and Xe isolated IBr, excited at a wavelength of 532 nm, exhibited both $A(^{3}\Pi_{1})-X(^{1}\Sigma)$ and $A^{\prime}(^{3}\Pi_{2})-X(^{1}\Sigma)$ systems. The life-times of these transitions decrease with increasing atomic number of the host. Spectral and temporal analyses will be discussed

TWO PHOTON STUDIES OF MATRIX ISOLATED IODINE

$^{1}$ W. Fawzy. M. Mackr, J. P. Nicolai and M. C. Heaven, submitted to J. Chem. Phys. $^{2}$ M.A.P. Macler and M. C. Heaven, 14, 43rd Symp. on Molec. Spectrosc. 1988. Work supported by AFOSR under grant 88-0249Author Institution: Department of Chemistry, Emory UniversityVisible laser excitation of matrix isolated iodine produced I.R. emissions that have been resolved into three componenta: the $A(^{3}\Pi_{1}) \to x(^{1}\Sigma_{g}^{+})$ and $A(^{3}\Pi_{2})\to x$ systetas $I_{2}$ and the $1^{2}P_{1/2}\to^{2}P_{3/2} transition.^{1}$ Single photon 193nm excitation of Ar isolated iodine produced a U.V. emission at $380 nm (D(^{3}\Pi_{2g})\to A(^{3}\Pi_{2u}))$ and the I.R. emission $systems.^{2}$ Further studies of visible excitation of concentrated rere-gas iodine matrices revealed A' fluorescence decay curves which were bi-exponential. The fast component ($\tau = 13\pm 2$ ms in Ar) corresponded to radiative decay, while a weak, slow component $(\tau 48\pm 4 ms)$ was thought to be a consequence of energy transfer from shallow-bound metastable electronic states. Sequential 2-photon excitation was used to confirm this hypothesis. In one sales of experiments 532nm pulses were used to excite the metastable states. Population in these stases was monitored by using 308nm pulses to excite to the D state. The metastable state decay lifetime was determined by following the $D'\to A'$ emission intensity as a function of the delay between the 532 and 308nm pulses. A $51\pm 7$ ms lifetime was observed, in excellent agreement with the rate at which population was transfered to the A state. Similar results were obtained with a 193nm pump 308nm probe sequence. In this case initial excitation of D' was followed by radiative relaxation into several valence states. The decay of these states was reflected in the delay dependence of the probe laser fluorescence. Spectral and temporal analyses of these experiments will be discussed

Relation between chemical composition of Grateloupia doryphora (Montagne) Howe, Gymnogongrus griffithsiae (Turner) Martius, and abiotic parameters

In Grateloupia doryphora and Gymnogongrus griffithsiae the seasonal variation of their chemical compounds was studied, establishing a relation with the physical and chemical properties of seawater. High values of proteins in the studied species were detected during the winter, 28.88% in G. doryphora and 26.68% in G. griffithsiae, corresponding to the maximum period of ammonium concentration in the marine environment. The variation in carbohydrates content showed an inverse relation with the proteins, with a maximum of 54.72% in G. doryphora and of 55.36% in G. griffithsiae, both in summer, positively correlated with salinity and temperature of sea water. Lipids content was low in both species. In G. doryphora the values ranged between 0.81 and 1.30% and, in G. griffithsiae, from 0.71 to 1.50% of dry weight, showing a direct relation with the amount of nitrogen in the seawater. The maximum content of ashes, phosphorus and potassium occurred in autumn and winter, respectively, with 11.85%, 0.20%, 1.27% in G. doryphora, and 14.46%, 0.14%, 1.41% in G. griffithsiae