Sônia Maria Flores Gianesella

Effects of Enhanced UV-B on Pigment-based Phytoplankton Biomass and Composition of Mesocosm-enclosed Natural Marine Communities from Three Latitudes

Abstract A series of three outdoor mesocosm experiments was undertaken in Rimouski (Canada), Ubatuba (Brazil) and Ushuaia (southern Argentina) to examine the effects of lamp-enhanced UV-B (280–320 nm) on phytoplankton communities isolated from seawater at each site. Detailed pigment composition was used to identify these communities. Each experiment compared three replicated UV-B treatments, consisting of natural sunlight conditions (NUVB), low-level UV-B enhancement corresponding to local 30% ozone depletion (LUVB) and high-level enhancement corresponding to 60% ozone depletion (HUVB). Each mesocosm (ca 2 m deep) was mixed continuously (turnover time, ca 1.3 h) and samples were obtained daily over 7–10 days. In Rimouski a large diatom bloom occurred during the first week. Repeated-measures analysis of variance (RM-ANOVA), with time as the repeated factor, showed slight but statistically significant increases in the chlorophyll (Chl) a level with the HUVB treatment, which were especially obvious over the last 3 days of the experiment. A large decrease in grazers (ciliates) that was observed concurrently with this treatment is the most likely explanation for the increase in Chl a level. The lack of negative effect on algal biomass by enhanced UV-B is attributed to the mixing inside the mesocosms and to the relatively low UV-B penetration. In Ubatuba levels of most pigments decreased over time, particularly fucoxanthin, Chl c3 and alloxanthin. The RM-ANOVA showed no effect of the UV-B treatments, except for Chl c3, which had significantly lower concentrations under natural UVB conditions, indicating that enhanced UV-B directly or indirectly favored Chl c3 algae (likely prymnesiophytes). Although particulate organic carbon concentration was significantly larger during HUVB treatment than during the other treatments, Chl a was unaffected, suggesting that enhanced UV-B favored heterotrophs. Lack of algal growth during this experiment was attributed to low nutrient concentrations (which were the lowest of the three sites), high irradiances (which were the highest noon incident photosynthetically available radiation and UV of the three sites) and UV-B penetration down to the bottom of the mesocosms. In Ushuaia a small bloom took place over the first 5 days. The RM-ANOVA showed no overall effect of the UV-B treatments for any of the pigments examined but on the last 3 days of the experiment several green algae-type pigments, such as Chl b and siphonein, showed increased concentrations under the HUVB treatment. UV-B enhancement hence favored green algae, as seen from the stronger increase over time in the ratio of Chl b to Chl a associated with the HUVB treatment. UV-B enhancement also seemed to cause a slight decrease in physiological condition, because the relative concentration of chlorophyllide a and some pheophorbides that may be the product of dying algae increased during the HUVB treatments in Ubatuba and particularly in Ushuaia (where UV-B also penetrated to the bottom of mesocosms). For all three sites changes in phytoplankton biomass due to the UV-B treatments were minor, even though UV-B enhancement was important. This study indicates that effects of enhanced UV-B on the community structure of both phytoplankton and their grazers are potentially more important than effects on overall algal biomass.

Instantaneous transport of salt, nutrients, suspended matter and chlorophyll-a in the tropical estuarine system of Santos

The contribution of the polluted Sao Vicente and Santos estuarine channels to the eutrophication of Santos bay was assessed through the quantification of instantaneous transport of salt, dissolved inorganic nitrogen (DIN) and phosphate, organic and inorganic matter (OSM and ISM) and chlorophyll-a (Chl-a), during dry (austral winter- August/ 1999) and rainy (austral summer- January/2000) seasons. Samplings were carried out during spring and neap tides, in flood and ebb phases, in two transversal sections at the mouths of the Sao Vicente and Santos channels. Instantaneous transport values generally indicated importation of salt to the estuarine channels, exportation of DIN to the bay, mainly as N-NH4, at a maximum rate of 1155.1 g s-1 during the rainy season; importation of phosphate during the dry season (maximum of 385 g s-1) and exportation of ISM, OSM and Chl-a during periods of greater freshwater discharge. These results demonstrate the great contribution made by the Santos and Sao Vicente estuaries to the eutrophication of Santos bay, especially in the rainy season.

UV Effects on Marine Planktonic Food Webs: A Synthesis of Results from Mesocosm Studies

Abstract UV irradiance has a broad range of effects on marine planktonic organisms. Direct and indirect effects on individual organisms have complex impacts on food-web structure and dynamics, with implications for carbon and nutrient cycling. Mesocosm experiments are well suited for the study of such complex interrelationships. Mesocosms offer the possibility to conduct well-controlled experiments with intact planktonic communities in physical, chemical and light conditions mimicking those of the natural environment. In allowing the manipulation of UV intensities and light spectral composition, the experimental mesocosm approach has proven to be especially useful in assessing the impacts at the community level. This review of mesocosm studies shows that, although a UV increase even well above natural intensities often has subtle effects on bulk biomass (carbon and chlorophyll), it can significantly impact the food-web structure because of different sensitivity to UV among planktonic organisms. Given the complexity of UV impacts, as evidenced by results of mesocosm studies, interactions between UV and changing environmental conditions (e.g. eutrophication and climate change) are likely to have significant effects on the function of marine ecosystems.

Ultraviolet B-photoprotection Efficiency of Mesocosm-enclosed Natural Phytoplankton Communities from Different Latitudes: Rimouski (Canada) and Ubatuba (Brazil)

Abstract Photoprotection against UV-B radiation (UVBR; 280–320 nm) was examined in natural phytoplankton communities from two coastal environments at different latitudes: temperate Rimouski (Canada) and tropical Ubatuba (Brazil). Mesocosm experiments were performed at these sites to examine the response of phytoplankton to increases in UVBR that corresponded to local depletions of 30% and 60% in atmospheric ozone levels (low and high UVBR treatments, respectively). A fluorescence method using a pulse amplitude modulation fluorometer (Xe-PAM, Walz, Germany) with selective UV filters was used to estimate photoprotection, and these results were compared with an index of mycosporine-like amino acid (MAA) concentrations determined using spectrophotometry of methanol extracts. The present study provided the first evidence, to our knowledge, of the suitability of this in vivo fluorescence method for the estimation of UV photoprotection efficiency in natural phytoplankton. No significant differences were found for most of the variables analyzed between the light treatments used at both sites, but differences were found between sites throughout the duration of the experiments. Vertical mixing, used to maintain cells in suspension, likely alleviated serious UVBR–induced damage during both experiments by reducing the length of time of exposure to the highest UVBR irradiances at the surface. In Rimouski, this was the main factor minimizing the effects of treatment, because optical properties of the coastal seawater rapidly attenuated UVBR throughout the water column of the ca 2 m deep mesocosms. In this location, synthesis of MAAs and photoprotective pigments likely contributed to the observed phototolerance of phytoplankton and, hence, to their growth; however, in a comparison of the UVBR treatments, these variables showed no differences. In Ubatuba, where nutrient concentrations were significantly lower than those in Rimouski, light attenuation was less than that in Rimouski and UVBR reached the bottom of the mesocosms. UVBR penetration and the forced vertical mixing of the cells, without the possibility of vertical migration below this photostress zone, resulted in photo-inhibition, because confinement in the mesocosms forced cells to remain constantly exposed to high levels of irradiance during the daytime. Hence, additional effects of UVBR were masked in this experiment, because cells were damaged too much and phytoplankton populations were rapidly declining. There was also an overall preservation of MAAs, in contrast with chlorophyll (Chl) degradation, in spite of the fact that this UV screening was not sufficient to counteract photo-inhibition, which suggests an important role for these molecules, either in the overall photoprotection strategy or in other physiological processes. Altogether, local water characteristics, namely attenuation, mixing, and nutrients concentration, can strongly modulate the photoprotection strategies used by natural phytoplankton populations in coastal environments.

Trichodesmium erythraeum Bloom on the Continental Shelf off Santos, Southeast Brazil

Samplings were undertaken on the basis of a grid of 40 oceanographic stations distributed along eight sections with the same point of origin: in the middle portion of the mouth of Santos Bay (Fig. 1). Surface water samples were collected using a Niskin bottle. The water samples were filtered through AP-40 Millipore filters for chlorophyll-

Simulation of Ozone Depletion Using Ambient Irradiance Supplemented with UV Lamps

Abstract In studies of the biological effects of UV radiation, ozone depletion can be mimicked by performing the study under ambient conditions and adding radiation with UV-B lamps. We evaluated this methodology at three different locations along a latitudinal gradient: Rimouski (Canada), Ubatuba (Brazil) and Ushuaia (Argentina). Experiments of the effect of potential ozone depletion on marine ecosystems were carried out in large outdoor enclosures (mesocosms). In all locations we simulated irradiances corresponding to 60% ozone depletion, which may produce a 130–1900% increase in 305 nm irradiance at noon, depending on site and season. Supplementation with a fixed percentage of ambient irradiance provides a better simulation of irradiance increase due to ozone depletion than supplementation with a fixed irradiance value, particularly near sunrise and sunset or under cloudy skies. Calculations performed for Ushuaia showed that, on very cloudy days, supplementation by the square-wave method may produce unrealistic irradiances. Differences between the spectra of the calculated supplementing irradiance and the lamp for a given site and date will be a function of the time of day and may become more or less pronounced according to the biological weighting function of the effect under study.

Assessment of plankton community and environmental conditions in São Sebastião Channel prior to the construction of a produced water outfall

A comunidade planctonica e condicoes hidrologicas foram avaliadas como parte de um diagnostico ambiental no Canal de Sao Sebastiao, previamente a construcao de um emissario submarino de agua de producao, oriunda do terminal maritimo da PETROBRAS. As amostras foram coletadas em vinte estacoes oceanograficas situadas na area adjacente ao terminal petrolifero, durante a primavera de 1991. As concentracoes de nutrientes inorgânicos dissolvidos e de cIorofila-a obtidas, indicam um ambiente oligo-mesotrofico. Fenois e sulfetos nao foram detectados e os valores de 080, com excecao de tres pontos, foram caracteristicos de ambientes nao poluidos, apesar da contaminacao por oleos e graxas ter sido observada em metade das estacoes amostradas. O fito e o zooplâncton apresentaram altos indices de diversidade e equitatividade para toda area estudada. O fitoplâncton foi dominado por fitoflagelados, enquanto que o zooplâncton foi dominado por copepodos, especialmente Paracalanus quasimodo. A composicao da comunidade planctonica foi similar a de outras areas adjacentes, sob baixa pressao aotropogenica.

A microcosm approach on the potential effects of the vertical mixing of water masses over the primary productivity and phytoplankton biomass in the southern Brazilian coastal region

The vertical mixing between South Atlantic Central Water (SACW) and Coastal Water (CW) was simulated through microcosm experiments using the autochthonous phytoplankton community (fraction 20°C) and oligotrophic. The phytoplankton growth potential of SACW, CW and an equivalent mixture of both (SACW+CW) was compared, under 100, 30 and 10% of sunlight, at surface seawater temperature, in winter and summer conditions. Results demonstrate the importance of SACW as a natural eutrophication agent for the mixing layer, allowing the occurrence of new production by nutrient input, and also as a biological seeder through the development of its autochthonous phytoplankton community when it reaches the euphotic zone. The time lag for phytoplankton development during winter was around 4-5 days, against 1-2 days in summer. The hypothesis of physiological differences between surface and bottom phytoplankton populations from a deep (80 m) and thermally homogeneous water column (common winter feature) was also tested through the microcosm experiments. Results obtained clearly demonstrate that bottom water presented higher phytoplankton growth potential than the surface one.

Short-term variability and transport of nutrients and Chlorophyll-a in Bertioga Channel, São Paulo State, Brazil

Short-term variability of nutrients, chlorophyll-a (Chl-a) and seston (TSS) concentrations were followed up at a fixed station in the Bertioga Channel (BC), Southeastern Brazil, over two full tidal cycles of neap and spring tides, during the winter of 1991. Simultaneous data on hydrographic structure, tidal level and currents allowed the computation of the net transport of those properties. Tidal advection and freshwater flow were the main forcing agents on the water column structure, nutrient availability and Chl-a distribution. Dissolved inorganic nitrogen and phosphate average values were high (16.88 and 0.98 ¼M, respectively, at neap tide and 10.18 and 0.77¼M at spring tide). Despite N and P availability, Chl-a average values were low: 1.13 in the neap and 3.11 mg m-3 in the spring tide, suggesting that the renovation rate of BC waters limits phytoplankton accumulation inside the estuary. The highest Chl-a was associated with the entrance of saltier waters, while the high nutrient concentrations were associated with brackish waters. Nutrients were exported on both tides, TSS and Chl-a were exported on the spring tide and Chl-a was imported on the neap tide. The study of the main transport components indicated that this system is susceptible to the occasional introduction of pollutants from the coastal area, thus presenting a facet of potential fragility.

Microalgal Feedstock for Bioenergy: Opportunities and Challenges

The utilization of algal feedstock for bioenergy can be considered as one of the greatest challenges for biosystems engineering in the near future. Some species of microalgae show high potential for oil accumulation and further utilization of its biomass for biogas generation, pyrolysis, ethanol production, and even as fertilizer. Microalgae can utilize CO2 as carbon source and can also be grown on nonagricultural environments, such as wastewater facilities, industrial effluents, freshwater, and marine water habitats. The vast research field on microalgae engineering is due to the facts that it can be a source of energy and act as an air and water pollutants removal. There have been considerable advances in engineering its growth, in bioreactor designs, and on lipid accumulation due to chemical, biochemical, and genetic studies. Despite that, there are still some fundamental processing aspects that are considered challenges, either economical, ecological, or technical, such as biomass harvesting and the competition with the higher value products produced from algae, as proteins.