Fernando Catarino

NONDESTRUCTIVE TRACING OF MIGRATORY RHYTHMS OF INTERTIDAL BENTHIC MICROALGAE USING IN VIVO CHLOROPHYLL A FLUORESCENCE1,2

In vivo chlorophyll (Chl) a fluorescence was measured in undisturbed intertidal sediments with the purpose of tracing the vertical migratory rhythms of benthic microalgae. A pulse amplitude fluorometer, an instrument which does not require physical contact with the sample, was used, thus allowing successive measurements to be taken on the same sample without causing any type of disturbance to the sediment structure. The basis of the method is the possibility to detect changes in the Chl a concentration near the sediment surface caused by the vertical movement of the microalgae. This requires the verification of two conditions: the possibility to follow changes in the sediment Chl a content from fluorescence intensity, and a sediment photic depth smaller than the vertical distances covered by the moving microalgae. Both conditions were experimentally verified in intertidal muddy sediments of the Tagus estuary, Portugal. In vivo fluorescence was shown to vary linearly with the sediment Chl a content, and the sediment photic depth was estimated to reach 0.27 mm, a value clearly smaller than the reported depths for microalgal migrations. Sediment samples kept under in situ conditions exhibited large hourly Variations (over 400%) in the Chl a fluorescence intensity, which were closely synchronized with the daytime periods of emersion. The rhythmic fluctuations in Chl a fluorescence were confirmed further to represent microalgal migration by (1) its endogenous nature (fluorescence continued to follow diurnal and tidal cycles after removal of environmental stimuli), (2) its dependence on the vertical distribution of the microalgal population within the sediment (vertically homogenized samples failed to display fluorescence variations), and (3) the lack of significant temperature and light effects on the fluorescence emission under in situ conditions (tested in three species representative of the main groups found in the studied microphytobenthic communities—the diatom Phaeodactylum tricornutum (Böhlin), the cyanobacterium Spirulina maxima (Setch. et Gard.), and the euglenophyte Euglena granulata (Klebs) Lemm.). The results obtained indicate that, in spite of the potential concurrent effects of factors other than the Chl a concentration on the fluorescence intensity, in vivo Chl a fluorescence can be used to trace nondestructively the migratory behavior of benthic microalgae.

The cellular location of Cu in lichens and its effects on membrane integrity and chlorophyll fluorescence

Abstract The data in the present study supported the hypothesis that Na 2 -EDTA at pH 4.5 is an efficient chelating agent for extracellular Cu without causing cell membrane damage, and that it can be used in a sequential elution procedure to determine the cellular location of Cu in lichens. The patterns of extracellular uptake vs. time or concentration were anticipated from conventional kinetics studies with other organisms and heavy metals. Supplied Cu replaced the naturally acquired extracellular Mg and Ca and induced alterations in the passage of K across the cell membrane. For Usnea spp. intracellular uptake saturated at low supplied Cu concentrations (0.0157 mM) and was toxic, as indicated by chlorophyll fluorescence measurements. In Ramalina fastigiata intracellular Cu concentrations above ca. 4.0 μmol g −1 were linked to a decline in chlorophyll fluorescence. The fluorescence parameter F v F m was shown to be useful in determining the sensitivity of the lichens to Cu uptake. Usnea spp. were the lichens most sensitive to Cu uptake, since physiological changes occurred for lower supplied Cu concentrations than for R. fastigiata . With this work we were able to determine and quantify the cellular location of Cu in lichens. We were also able to evaluate through membrane integrity and fluorescence measurements the physiological state and the relative sensitivity of different lichen species to Cu uptake.

Seasonal variation of Zn, Pb, Cu and Cd concentrations in the root-sediment system of Spartina maritima and Halimione portulacoides from Tagus estuary salt marshes

Concentrations of Zn, Pb, Cu and Cd have been determined in leaves, stems and roots of Spartina maritima and Halimione portulacoides from the Tagus estuary salt mash (Corroios) and in the sediments between their roots. Biological materials and sediments were sampled every 2 months, between July 1991 and July 1992. Root biomass increased from July to September and from January to March. The greatest metal concentrations occurred in the roots, with lowest levels in January and increasing levels during the growth periods. Zn, Pb and Cu in sediments exhibited a corresponding change in concentrations, reaching maximum in January and subsequently decreasing in spring. The ratios between metal concentrations in the root and in sediments were higher for H. portulacoides when compared to S. maritima, whose roots are surrounded by a more acidic and reduced sediment environment. It was concluded, therefore, that H. portulacoides is a more effective accumulator of metals than S. maritima, and both root-sediment systems exhibited a seasonal variation of metal concentrations.

Ecological economics and sustainable governance of the oceans

Abstract This paper is an introduction and synthesis of the papers that appear in this special issue devoted to the sustainable governance of the oceans. The special issue contains papers on various aspects of the problem, including: the ecological and economic importance of the oceans, the problems facing the oceans from an ecological economics perspective, the links between science and policy, the rationale for sustainable ocean governance, and examples of sustainable institutions and governance structures. We developed the ‘Lisbon principles’ of sustainable governance (responsibility, scale-matching, precaution, adaptive management, full cost allocation, and participation) as a core set of guidelines for sustainable ocean governance. We then describe the major problems facing the oceans in terms of how the principles are violated, and evaluate some suggested institutions in terms of how the principles are incorporated.

Improving the use of lichens as biomonitors of atmospheric metal pollution

The data reported on this study supported the hypothesis that the absence of the lichen Ramalina fastigiata near a copper mine site located on the south of Portugal was related to toxic levels of Cu-dust near the centre of the mine. Lichen biodiversity reflected the impact of the copper-mine dust emissions which were more widespread towards the east, correlated with wind direction and frequency. The chemical analysis of R. fastigiata collected at different distances and in different directions from the mine showed that Cu, K and Mg were derived from the centre of the mine site, confirming thus as the major source of atmospheric dust. Total inhibition of PSII photochemical reactions occurred in R. fastigiata both under field and controlled conditions, when intracellular Cu concentrations exceeded a threshold of approximately 2.0 mumol g-1. No samples of this species were found under field conditions beyond the Cu threshold. Thus, the fluorescence parameter Fv/Fm proved to be a good estimator of the survival capacity of R. fastigiata under field conditions and thus a useful parameter in determining the sensitivity of the lichens (photobiont) to Cu pollution. The intracellular location of Cu allowed an explanation of the physiological changes and the survival of the species in the surroundings of the copper-mine.

Lead (Pb) uptake and its effects on membrane integrity and chlorophyll fluorescence in different lichen species

Abstract We report an investigation into the effect on membrane integrity and chlorophyll fluorescence of extra- and intracellular lead (Pb) concentrations in lichens possessing different photosynthetic symbionts and thallus growth forms (Lobaria pulmonaria, Ramalina farinacea, Parmelia caperata and Peltigera canina). Pb uptake, particularly in cyanobiont lichens, caused a decrease in photosystem II (PSII) photochemical reactions, measured as a change in the ratio variable fluorescence:maximal fluorescence ( F v F m ). In the lichens L. pulmonaria and Parmelia caperata, the effect on PSII photochemical reactions could only be observed 48 h after Pb uptake, confirming that prolonged exposure to Pb caused an additional decrease in F v F m . We confirmed that Pb enters the cells of the lichens. We found identical maximal extracellular Pb concentrations among the different lichens; however, the maximal intracellular Pb concentrations were not identical in range. Lichen PSII photochemical reactions were more sensitive to Pb than cell membrane damage since, with increasing Pb concentrations, no clear alterations in lichen membrane permeability, as measured by the loss of intracellular K and Mg, were observed. The effects of Pb in lichens were shown to be dependent only on the nature of the photobiont. We confirmed that Pb displaced extracellular exchangeable Ca and Mg.

The influence of plants on concentration and fractionation of Zn, Pb, and Cu in salt marsh sediments (Tagus Estuary, Portugal)

Sediment cores were collected from two sites of the Tagus estuary salt marshes which differed in degree of metal contamination. At each site, six 60-cm-long cores were taken, three from a non-vegetated intertidal zone, and one from each of areas colonized by salt marsh plants, Spartina maritima, Halimione portulacoides and Arthrocnemum fruticosum, respectively. Total concentrations and concentrations in sequential extractions of Zn, Pb, and Cu were determined in several sediment layers. Sediment slices containing most of the roots (5–15-cm depth) were enriched in metals in comparison with other depths in the core and with non-vegetated cores. Additionally, metals in sediment slices with roots were preferentially linked to the residual fraction. These results are evidence that aquatic plant roots can have a strong influence on metal concentration and speciation in sediments. Since metals become immobilized in vegetated sediments, the preservation of salt marshes or the creation of artificial wetlands could be considered as an efficient natural means for maintaining ecosystem health or restoring ecosystem quality.

Presence of metal-rich rhizoconcretions on the roots of Spartina maritima from the salt marshes of the Tagus Estuary, Portugal.

Abstract A striking feature of southern and eastern intertidal areas in the Tagus Estuary is the presence of hollow sediment-cylinders, ranging from 0.5 to 15 mm both in length and diameter, around the roots and rhizomes of the vascular plant Spartina maritima . The weight fraction that makes up these cylinders varies between 0% near the sediment surface and 8% in deeper layers. Compared with the surrounding sediment, the structures are enriched in some metals, particularly Fe (11%). The concentration of Mn is also high (1496 μg g −1 ). Trace metals Zn, Cu, Cd and Pb vary widely, with the highest concentrations in the thinnest rhizoconcretions.

Oxygen profiles in intertidal sediments of Ria Formosa (S. Portugal)

Microelectrode oxygen profiles were measured in intertidal sediments from Ria Formosa (S. Portugal), a very productive shallow coastal lagoon. Four intertidal sampling sites were selected according to different sediment characteristics. Individual profiles revealed a high degree of lateral variability on a centimeter spatial scale. Nevertheless, consistent differences were observed between oxygen profiles measured in atmosphere-exposed and inundated intertidal sediments: in organically poor sand oxygen-penetration depth varied from 3 mm in inundated cores to more than 7 mm in exposed ones, while in organically rich muddy sand and mud it remained between 0.5–2.0 mm. The oxygen input from inundated to exposed conditions was estimated for each sampling site. Semi-diurnal tidal fluctuation, leading to periodical atmospheric exposure of sediments plays a major role in the oxygenation process of intertidal zones of Ria Formosa.

Microphytobenthos primary production of Tagus estuary intertidal flats (Portugal)

The purpose of this study was to measure primary productivity of microphytobenthos of intertidal mudflats of Tagus estuary. Sampling occurred from 1991 to 1992, during low tide of spring waters on 2 stations, each one representative of a typical habitat. Net photosynthesis rates (NP) were measured in undisturbed sediment cores incubated in the laboratory andin situ. The results obtained indicated that NP in the laboratory was similar for the two stations, (mean values of 1.1 and 1.3 mmol O2 m−2 h−1, within a range of 5-fold). A stepwise regression analysis combining biotic and abiotic factors was performed to explain temporal variability, indicating that NP in each site was influenced by different parameters, with the exception of precipitation, which might play an important role in the disruption of sediment-water interface. Photosynthesis-Irradiance curves constructed with the results obtained insitu showed similar photophysiological responses of the two communities. Based on the values of photosynthetic efficiency (α), and of optimal light intensity (lk) measured and on the combination of the photoperiod pattern and the amount of light available for each sampling site, an estimation of total annual productivity is given: 47–178 g C m−2.