Catálogo de publicaciones - libros

Percentages of nitrogen and phosphorus in 10 species of seaweeds (6 green and 4 red algae) were monitored from 1997 to 2004 by seasonal sampling in Guanabara Bay, South-eastern Brazil. The species did not show consistent variations in tissue and : that related to annual cycles. Throughout this study, higher percentages of tissue and were found in and (red algae) and lower in and (green algae). In November 1999, the Icaraí Submarine Sewage Outfall became operational, resulting in a reduction of visual pollution in the area and an improvement in the local quality of seawater for recreational use. Measurements of dissolved nutrients at the sampling site did not indicate significant changes in concentrations after the commissioning of the submarine sewage outfall; however, tissue and : ratio of most of species were significantly lower than in the first two years of this survey. Variations in tissue nitrogen throughout this study were not significant, except for in some comparisons. Results show that seaweeds function very well as monitors of environmental changes in Guanabara Bay. Experimental data are needed to identify possible environmental processes which are promoting changes in chemical composition of the local seaweed populations.

La Paz Bay and La Paz Lagoon are water bodies of the Gulf of California that are influenced by waste water discharges from the City of La Paz and from activities of the phosphorite mining company “Rofomex”. Because seaweeds concentrate elements from the water and are used as effective indicators of contamination by metals, we investigated their usefulness in this region. Concentrations of certain major elements (Ca, Fe, K and Na) and trace elements (As, Ba, Co, Cr, Cs, Hf, Rb, Sb, Sc, Se, Sr, Ta, Th, U, Zn and Zr) were determined in 12 species of seaweeds from La Paz Bay and La Paz Lagoon using instrumental neutron activation analysis. The contents of trace elements of environmental importance (As, Co, Cr, Fe, Sb, Se and Zn) in all studied samples are within the range of typical levels for a pristine environment not subjected to anthropogenic impact. Somewhat higher concentrations of Cr (81 mg kg), Hf (4 mg kg), Rb (48 mg kg), Sc (6.3 mg kg), Ta (0.95 mg kg), Th (6.8 mg kg), U(33 mg kg) and Zn (90 mg kg) were found in the green seaweed species (formerly , whereas such elements as As (77 mg kg), Sb (1.4 mg kg) and Se (1.8 mg kg) were mainly concentrated in the species and respectively. Because of their higher abundance and heterogeneity in elemental composition the seaweeds species and seem to be more suitable for further biomonitoring of heavy metal pollution of the coastal waters in this zone.

2-Nonenal and -hexanal are the major and minor flavor compounds in the edible brown alga, , respectively. They are believed to characterize the flavor of this alga. However the metabolism of the two compounds is not precisely known. The pathways were clarified by elucidation of the intermediate structure through purification of the intermediate compounds from an enzymatic reaction and identification using HPLC and GC-MS techniques. Formation of -hexanal, 3-nonenal and 2-nonenal are proposed to be two cascades from unsaturated fatty acids. They are C18:2(-6), linoleic acid cascade and C20:4(-6), arachidonic acid cascade through their hydroperoxides as intermediates by the lipoxygenase/fatty acid hydroperoxide lyase pathway.

Since ancient times, the antimicrobial properties of seaweeds have been recognized. However, antimicrobial activities of volatile compounds in seaweeds have not been explored so far. Here, essential oils from seaweeds including green, brown and red algae such as and were prepared by using SDE (simultaneous distillation and extraction) apparatus. Volatile compounds in the essential oils were identified as aldehydes, ketones, carboxylic acids, alcohols and hydrocarbons by comparison of GC-retention times and MS data with those of authentic specimens. Flavor compounds such as (3)-hexenal, (2)-hexenal and (2)-nonenal in some essential oils showed strong antimicrobial activities against TG-1, and . Inhibition of browning can be achieved during either of two stages, namely, oxidation reaction by tyrosinase or subsequent non-enzymatic polymerization. Tyrosinase activity was measured by monitoring absorbance at 475 nm originating from dopachrome formed from L-DOPA. Many kinds of aliphatic carboxylic acids, aldehydes and alcohols were used as inhibitors for PPO activity. The results indicated that the ,-unsaturated carbonyl compounds strongly inhibit tyrosinase activity. When seaweeds are damaged or macerated, the ,-unsaturated aldehydes such as (2)-hexenal and (2)-nonenal are biosynthesized the corresponding (3)-unsaturated aldehydes from linolenic acid and arachidonic acid. The flavor compounds that are formed could be valuable as safe antimicrobial browning-inhibitory agents of edible seaweed origin.

Many species of macroalgae survive after becoming dislodged from their primary substratum, but little is known about their capacity to express anti-herbivore defences after detachment. We examined the effect of detachment on the relative palatability of the two kelp species and to mesograzers. Laboratory and field experiments were conducted on the northern-central coast of Chile to investigate whether (i) time after detachment and (ii) grazing on detached and attached algae could trigger internal defence mechanisms in the algae, which may have acted as deterrents to grazing. In order to examine palatability, feeding assays were run after each experiment using fresh algal pieces and artificial food. Time after detachment had a significant influence on palatability of but not of . During the first 12 days of detachment, detached held in grazer-free laboratory tanks were not significantly more palatable than attached conspecifics from the field but thereafter detached individuals became more palatable. Floating individuals of showed no effect of detachment, indicating that this alga maintains its defence after detachment. An experiment conducted in the field confirmed these results for . An additional laboratory experiment confirmed that attachment status plays an important role on algal defence reaction for when exposed to grazers. Detached and previously grazed individuals of this species were less palatable than grazer-free control algae, but grazing had no effect on palatability of attached algae. Our results indicate that kelps have varying capacities for development of anti-grazing responses once they become detached, possibly depending on their capacity to float and survive after detachment.

The effects of different diets on growth in the cultured South African abalone, (Linnaeus), was investigated. Growth of juvenile was monitored on a commercial abalone farm over a period of 9 months in an experiment consisting of 9 treatments with 4 replicates ( = 250 individuals per replicate). The treatments were: fresh kelp () blades (seaweed control); Abfeed ® (formulated feed control); kelp + Abfeed ®; dried kelp pellets; dried kelp blades; dried kelp stipes; fresh kelp with the epiphyte ; a mixed diet (, and kelp) and a rotational diet (abalone were fed 1 of the 9 treatments for the first week and them kelp for the next 3 weeks). Results show that abalone grow well on all fresh seaweed combinations, but grow best on a mixed diet. The likely reason for the success of the mixed diet is that the red and green seaweed was farm grown, with an increased protein content. Dried kelp in any form produced poor growth. Abalone fed on the mixed diet grew at 0.066mm day shell length and 0.074 g day body weight; this corresponds to 24.09mm shell length and 27.01 g body weight increase per annum. Abalone fed on dried kelp grew at only 0.029mm day shell length and of 0.021 g day body weight. Abalone grown on Abfeed ® grew at 0.049mm day shell length and 0.046 g day body weight which corresponds to 17.88mm and 16.79 g increase per annum; this is better than the dried seaweed feeds, but poorer than the fresh seaweed combinations. This study shows that seaweed diets, particularly if the diets include seaweeds grown in animal aquaculture effluent, are good substitutes for the formulated feed generally used today.

Seaweed polyphenols are potent antioxidants and have also been shown to have -glucosidase inhibiting activity. In our continuous efforts to develop new marine-based nutraceuticals and functional food ingredients, we have investigated many algal species collected on the Atlantic coast of Canada. A simple method for estimating the total polyphenol content in seaweeds and their extracts was developed based on the classic Folin-Ciocalteau colorimetric reaction. By using the 96-well microplate and a microplate reader, this new method saves experimental time, significantly reduces the amount of sample required, handles large number of samples in one experiment, and also improves the repeatability of the results.

A number of algal samples collected on the seashore of Nova Scotia, Canada, were analyzed for their levels of polyphenol content using this microplate-based method. The antioxidant activity of these samples was also assessed by using DPPH (2, 2-diphenyl-1-picrylhydrazyl) radical scavenging assay. The results showed that there is a strong correlation between the total polyphenol content and the potency of antioxidant effect.

The effects of UVB radiation on the growth of macroalgal thalli were evaluated using tetrasporophytic fronds of the Rhodophytes and . The tetrasporophytic fronds were collected from nature and the tetrasporophyte sporelings grown in a temperature regulated chamber at 8±2 °C with a 12L:12D (Light: Dark) photoperiod, Photosynthetically Active Radiation (PAR) of 55 mol photons m s and seawater enriched with 20 mL L of Provasoli medium. We exposed the thalli of these macroalgae to PAR (55mol photons m s) and three treatments using a combination of PAR with three different levels of UVB radiation (0.10, 0.15 and 0.23 W m for and and 0.02, 0.05 and 0.10 W m for ) during a period of 71 days. Growth of thalli was quantified by measuring their length using digitized photographs of samples.

Important differences were detected in the growth of individuals cultured under the effects of UVB radiation, when compared to the control (i.e. plants exposed to PAR only). In the case of and higher levels of UVB radiation resulted in slower growth of thalli. In nearly all measurements for the first two species, UVB radiation levels of 0.1 W m induced differences in thallus growth, while for levels of UVB radiation of 0.1 W m were effective only after a prolonged period of exposure.

Differential effects of UVB radiation on and could interfere with the natural populations of these economically important macroalgal species in southern Chile, where they occur under the annual influence of the Antarctic Ozone Hole and the general thinning of the ozone layer.

The marine algal species in the Baltic Sea are few due to the low sea water salinity. One of the few species that can be found is . Even this species is affected by the low salinity and becomes smaller in size in the Baltic. In present work the photosynthesis of in the northern Baltic (Bothnian Sea) was compared to the photosynthesis of in the Atlantic. Oxygen evolution was measured before and after exposure to 2.3W of UV-B (280–320 nm) radiation for 5 h, as well as after 48 h recovery in low light. The plants were kept in their own sea water salinity as well as in a changed salinity, this to examine possible correlations between salinity and photosynthesis. The results show a significant higher initial maximal photosynthesis () for Atlantic plants (10.3 nmolO g FWs) compared to Baltic plants (4.0 nmolO g FWs). The Baltic plants were found more sensitive to UV-B with a 40–50% decrease of as well as a lower degree of recovery (60–70% compared to 75–95% for the Atlantic plants). The higher salinity (35 psu) had a positive effect on the Baltic with increased as well as increased tolerance to UV-B. The lower salinity (5 psu) had a negative effect on the Atlantic plants with a decreased as well as a lower tolerance to UV-B. Pigment content was found higher in Atlantic . The pigment content decreased then the Atlantic plants were transferred to 5 psu. The concentration of Chl a as well as the total content of violaxanthin, diadinoxanthin and zeaxanthin in Baltic plants increased when transferred to 35 psu. The Atlantic can not survive the low salinity in the northern Baltic (died within 8 weeks). It is likely that a long time acclimation or adaptation to low salinity has taken place for in northern Baltic. If this is an ecotypic or genotypic development it is too early to say.

is a potentially valuable source of marine biopolymers such as proteins and polysaccharides. In order to select suitable culture conditions, growth and tolerance of Holmes from Shikoku Island in southwest Japan were investigated under variations of temperature (5–30 °C), photon irradiance (20–120mol photons m s), and photoperiod (12:12 h, 14:10 h light:dark regime) in a unialgal culture. showed wide tolerances for all factors investigated, which is characteristic of eurythermal species. Maximum growth was observed at 18–24 °C. The optimum photon irradiance for algal growth was 60–120mol photons ms. Instead of using ordinary sea salt (NaCl) to prepare artificial seawater, ultra pure salt was adopted. grew faster in artificial seawater made with ultra-pure salt than that made with ordinary sea salt, probably because the former medium was clear, while the latter was milky. Effects of some metal ions on the growth were tested with artificial seawater. Iron ions affected algal growth, but cobalt ions did not. This study enables us to determine suitable culture conditions for . A scaled-up 30 l culture of under such conditions was successful.