DSpace Angular :: Browsing by Author "Correa, JA"

Browsing by Author "Correa, JA"

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An assessment of the potential use of the nematode to copepod ratio in the monitoring of metals pollution. The Chanaral case
(2001) Lee, MR; Correa, JA; Castilla, JC
We discuss the use of the nematode to copepod ratio in relation to determining the extent of metals impact using the Chanaral area of northern Chile, where the dumping of copper mine tailings has taken place for many years, as an example. Data were collected from 12 beaches in the area on eight occasions between January 1997 and October 1998. We find that the ratio is not a good predictor of pollution due to the generally low densities of meiofauna on impacted beaches and the absence of harpacticoid copepods from those beaches. We suggest that in the case of metal pollution the mean number of Harpacticoida per site may be a better indicator of impact stress. We rule out the use of the nematode to copepod ratio as an indicator in biomonitoring studies where metal enrichment is thought to occur. (C) 2001 Elsevier Science Ltd. All rights reserved.
Antioxidant responses in Scytosiphon lomentaria (Phaeophyceae) inhabiting copper-enriched coastal environments
(2005) Contreras, L; Moenne, A; Correa, JA
Scytosiphon lomentaria (Lingb.) Link. (Phaeophyceae) is one of the two dominant seaweeds in a coastal area of northern Chile affected by copper mine wastes, where the concentration of copper in water and algal tissues remains higher than in nonimpacted sites. Copper-loaded plants develop oxidative stress, as demonstrated by the increased levels of reactive oxygen species and lipoperoxides. This stress was associated with 1) an enhanced activity of the antioxidant enzymes catalase, glutathione peroxidase, ascorbate peroxidase, monodehydroascorbate reductase, and dehydroascorbate reductase and 2) an inhibition of the glutathione reductase activity. Furthermore, stressed plants showed a decrease in glutathione and phenolic compounds levels and an increase in total ascorbate. Reciprocal transplants revealed that plants rapidly adjusted their antioxidant system in response to the conditions of the receiving site. In individuals transplanted from the copper-enriched environment to the control site, normal levels of lipoperoxides and antioxidant compounds were restored in 48 h and antioxidant enzymes recovered their basal activities in 96 h. Individuals transplanted from the control site to the copper-enriched area adjusted their antioxidant compounds and antioxidant enzymes within 48 h and 96 h, respectively, and reached the functional status of the local plants. We conclude that S. lomentaria inhabiting the copper-enriched area buffered oxidative stress by a simultaneous involvement of antioxidant enzymes and water-soluble antioxidant compounds. These antioxidant responses were rapid and reversible, suggesting that copper resistance in S. lomentaria is a constitutive trait and that copper enrichment of the area did not result in a locally adapted copper-tolerant ecotype.
Copper accumulation, synthesis of ascorbate and activation of ascorbate peroxidase in Enteromorpha compressa (L.) Grev. (Chlorophyta) from heavy metal-enriched environments in northern Chile
(2003) Ratkevicius, N; Correa, JA; Moenne, A
Enteromorpha compressa is the dominant species in coastal areas of northern Chile receiving copper mine wastes. Copper remains as the main heavy metal in these coastal waters and it is accumulated in E. compressa growing at the impacted sites. Algae from these sites showed higher levels of lipoperoxides than from non-impacted sites, which suggests the occurrence of cellular damage resulting from oxidative stress. The strong activation of ascorbate peroxidase detected in this study probably occurs in order to buffer this oxidative stress. Unexpectedly, the activity of glutathione reductase, normally coupled to ascorbate peroxidase activity, was not affected by the chronic exposure to the mine wastes. Moreover, catalase, dehydroascorbate reductase and glutathione peroxidase, commonly reported to buffer oxidative stress in plants and algae, were not detected in E. compressa from any of the studied sites. Levels of total glutathione and phenolic compounds decreased in algae from mine-impacted sites. In contrast, high levels of dehydroascorbate were found in algae from impacted sites, whereas ascorbate remained unchanged. Therefore, it is suggested that E. compressa tolerates a copper-enriched environment, and the accompanying oxidative stress, through the accumulation of copper, activation of ascorbate peroxidase, synthesis of ascorbate ( accumulated as dehydroascorbate) and consumption of glutathione and water-soluble phenolic compounds.
Copper mine tailings disposal
(2004) Lee, MR; Correa, JA
The hypothesis investigated in this paper is that the interstitial polychaetc Saccocirrus sonomacus is excluded from beaches impacted by tailing disposal as a result of the blocking of the interstitial space and not by a response to the toxicity of elevated copper concentrations. Field evidence suggested that abundances of S. sonomacus on beaches where they would be expected to occur under natural conditions are lower when a beach has received a significant amount of tailings. In choice experiments, S. sonomacus always preferred an open coarse sand matrix to one where the interstitial spaces had been blocked by fine sand (a tailings substitute). Using in vitro bioassays, we found that the LC50 for S. sonomacus with copper was 44 mug Cu l(-1), this being higher than the values of interstitial labile copper measured on the beaches investigated in this study. We therefore accept the hypothesis of a physically mediated exclusion rather than a toxically mediated one.
Copper, copper mining effluents and grazing as potential determinants of algal abundance and diversity in northern Chile
(2000) Correa, JA; Ramírez, MA; de la Harpe, JP; Román, D; Rivera, L
We experimentally tested three alternative hypotheses to explain the low algal diversity and abundance in an intertidal zone receiving the effluents of the copper mine El Salvador in northern Chile. Our results demonstrated that algae were able to grow at the levels of dissolved copper detected in coastal waters of the area. During the assays, growth and regeneration in several red, green and brown adult algae and juvenile Lessonia nigrescens were normal at copper levels of 150 mu g L-1 or, in some cases, higher. We also found that the coastal sea water mixed with the effluent was not lethal to algae, although in some cases minor effects on growth were detected. These results indicate that today's low algal diversity and abundance can not be explained by the current copper levels in the area nor by the effect of the effluent. Exclusion of grazers, however, resulted in a fast colonization by various algal species. This, together with atypically high grazer density at the areas under the influence of the effluent, strongly suggests that herbivory, a factor not directly related to the mining operation, is likely to be responsible for the low algal diversity and abundance in the studied locality.
Development of microsatellites DNA markers in the cultivated seaweed, Gracilaria chilensis (Gracilariales, Rhodophyta)
(2005) Guillemin, ML; Destombe, C; Faugeron, S; Correa, JA; Valero, M
The red algae Gracilaria chilensis is extensively cultivated for agar production. In spite of its commercial significance as the first algal resource in Chile, no information is available on the pattern of genetic diversity. In this paper, we isolated six polymorphic microsatellite markers from a G. chilensis-enriched DNA library. Genetic diversity was assessed in two natural populations revealing relatively low levels of heterozygosity ranging from 0.00 to 0.51. The six loci developed here are good candidates to assess the level of genetic resources within this species, which probably suffered from over-exploitation in several localities along the Chilean coast.
Differential life history phase expression in two coexisting species of Scytosiphon (Phaeophyceae) in northern Chile
(2005) Camus, C; Meynard, AP; Faugeron, S; Kogame, K; Correa, JA
The identity of two phaeophycean taxa that monopolized the middle-lower rocky intertidal zone of a coastal area chronically exposed to copper mine wastes in northern Chile was unraveled. One of them was preliminarily identified as the gametophytic stage of Scytosiphon lomentaria (Lyngbye) Link. The other, a dark crust, resembled the alternate stage of some Scytosiphon species. Comparative analysis of morphology, life history, and DNA sequences strongly suggests that crusts corresponded to sporophytic S. tenellus Kogame and confirm that erect thalli belonged to S. lomentaria. A clear segregation of erect and crustose thalli was found using internal transcribed spacer region 1 and RUBISCO spacer sequences. Furthermore, whereas crusts always grouped with S. tenellus, erect thalli always grouped with S. lomentaria. Life history studies failed to connect the two entities. First, field-collected S. tenellus produced progeny that either recycled the crust, which reproduced by unilocular zoidangia, or developed into erect thalli. The latter, unlike typical gametophytic S. lomentaria, developed patchy sori of plurilocular zoidangia. Second, S. lomentaria displayed a direct-type life cycle, in which progeny from erect individuals only developed into erect thalli and produced only plurilocular zoidangia. This constitutes the first experimental study on Scytosiphon from the Pacific coast of South America and the first report of S. tenellus on this coast. It is also the first report of the crustose stage of Scytosiphon appearing as a perennial and dominant algal species in a temperate rocky intertidal system.
Dissection of two distinct defense-related responses to agar oligosaccharides in Gracilaria chilensis (Rhodophyta) and Gracilaria conferta (Rhodophyta)
(2005) Weinberger, F; Leonardi, P; Miravalles, A; Correa, JA; Lion, U; Kloareg, B; Potin, P
The two agar-producing red algae, Gracilaria chilensis C. J. Bird, McLachlan & E. C. Oliveira and Gracilaria conferta (Schousboe ex Montagne) Montagne, responded with hydrogen peroxide (H2O2) release when agar oligosaccharides were added to the medium. In G. conferta, a transient release was observed, followed by a refractory state of 6 h. This response was sensitive to chemical inhibitors of NADPH oxidase, protein kinases, protein phosphatases, and calcium translocation in the cell, whereas it was insensitive to inhibitors of metalloenzymes. Transmission electron microscopic observations of the H2O2-dependent formation of cerium peroxide from cerium chloride indicated oxygen activation at the plasma membrane of G. conferta. A putative system, consisting of a receptor specific to agar oligosaccharides and a plasma membrane-located NADPH oxidase, appears to be responsible for the release of H2O2 in G. conferta. Subcellular examination of G. chilensis showed that the H2O2 release was located in the cell wall. It was sensitive to inhibitors of metalloenzymes and flavoenzymes, and no refractory state was observed. The release was correlated with accumulation of an aldehyde in the algal medium, suggesting that an agar oligosaccharide oxidase is present in the apoplast of G. chilensis. The presence of this enzyme could also be demonstrated by polyacrylamide electrophoresis under nondenaturating conditions and proven to be variable. Cultivation of G. chilensis at 16 to 17 degrees C resulted in significantly stronger expression of agar oligosaccharide oxidase than cultivation at 12 degrees C, which indicates that the enzyme is used under conditions that generally favor microbial agar macerating activity.
Healing and regeneration responses in Gigartina skottsbergii (Rhodophyta, Gigartinales)
(1999) Correa, JA; Beltrán, J; Buschmann, AH; Westermeier, R
The red alga Gigartina skottsbergii is becoming increasingly valuable as a resource to providing the raw material for the carrageenan industry established in Chile and elsewhere. As a result, wild stocks of the species are subject to intense harvesting by local fishermen. With the current levels of harvesting, it seems likely that natural stands of G. skottsbergii will soon collapse. Although cultivation seems an alternative, knowledge regarding the biology of the species is exceedingly limited. This study reports the first attempt to determine the optimal conditions for vegetative propagation of this species in the laboratory. For this purpose, the processes of wound healing and regeneration of frond fragments and haptera were studied under controlled conditions of temperature, light, and media strength. Our results demonstrated that excised tissues of G. skottsbergii were able to seal the exposed areas in approximately 20 days, by a wound healing process characterized by a re-differentiation of medullary cells into a normal cortex. Our data also demonstrated that frond fragments are better than haptera for propagation purposes. The development of new cortical tissue at the cut surface is followed, within 60 days, by localized blade-like outgrowths along the repaired area. Furthermore, the healing and regenerative responses in both frond fragments and haptera differed in efficiency according to the various combinations of factors, with optimum of 10-15 degrees C, 5 mu mol m(-2) s(-1) and plain seawater or standard SFC medium for the fronds. The two types of responses were negatively affected by seawater enriched with a double concentration of nutrients.
Hierarchical spatial structure and discriminant analysis of genetic diversity in the red alga Mazzaella laminarioides (Gigartinales, Rhodophyta)
(2001) Faugeron, S; Valero, M; Destombe, C; Martínez, EA; Correa, JA
Our study of the genetic structure of Mazzaella laminarioides (Bory) Fredericq (Gigartinales) in the central Chilean region documented a high level of genetic diversity based on random amplified polyp morphic DNA (RA-PD) markers and indicated the occurrence of significant genetic structure at different spatial scales. A total of 288 haploid gametophytes was analyzed with 17 polymorphic RAPD bands, which produced 202 distinct multilocus genotypes. Within stands, mean gene diversity ranged from 0.210 to 0.249 and no significant linkage disequilibrium could be detected among pairs of alleles, revealing that recombination (sexual reproduction) regularly shuffles the genes at that scale. Analysis of molecular variance within stands (less than 30 in) showed that the structure was very low, only marginally significant, and did not increase with increasing hierarchical levels at this lowest spatial scale. In contrast, at a larger spatial scale (among stands, from 5 to 60 km), increasing geographical distance seemed to account for increasing isolation between populations even if natural barriers, such as sandy beaches or river estuaries, may play a role in such isolation. Moreover, the strong genetic differentiation occurring between locations separated by 60 kin allowed the assignment of individuals to their original population through a canonical discriminant analysis. This approach further allowed the identification of potential recent migrants from one population to the other. Thus, in species like M. laminarioides for which the dominance of RAPD markers can be avoided by selecting haploid individuals, RAPD analysis appeared to be specially appropriate for the study of genetic differentiation.
Infectious diseases in Mazzaella laminarioides (Rhodophyta)
(2000) Faugeron, S; Martínez, EA; Sánchez, PA; Correa, JA
Very little is known about the potential effects of endophytic infections on the host in algae, especially in terms of fitness. In this study, we report a first attempt at quantifying the effects of the endophytes Endophyton ramosum (Chlorophyta) and Pleurocapsa sp. (Cyanophyta) on the reproductive potential of their host Mazzaella laminarioides (Rhodophyta). Density of reproductive structures and spore germination rates was compared between infected and non-infected fronds. It was found that differences in density of reproductive structures between infected and non-infected fronds were not significant, which suggests that the level of maturity of the host is unaltered by the endophytes. On the other hand, carpospore germination rates significantly decreased when produced by fronds infected by the cyanobacterium Pleurocapsa sp. Thus, in the general context of host fitness, we discuss the fact that only some of the components of the reproductive output of M. laminarioides are negatively affected by the endophytes.
Long-term copper mine waste disposal in northern Chile associated with gene flow disruption of the intertidal kelp Lessonia nigrescens
(2005) Faugeron, S; Martínez, EA; Correa, JA; Billot, C
This study tests the general hypothesis that habitat disruption caused by the release of copper mine wastes in coastal waters has a negative impact on gene flow among populations of the kelp Lessonia nigrescens Bory. Hierarchical sampling was performed within continuous, undisturbed stands and at the northern and southern edges of a 40 km gap caused by mine wastes. Our results, based on RAPD markers, showed a strong genetic structure even in the absence of the disrupting effect of the mine wastes. No pattern of isolation by distance is apparent, however, which indicates that populations are at migration-drift disequilibrium, and suggests that most events of spore recruitment and/or gametophyte fertilization occur within a few metres. On the other hand, some long distance dispersal is likely to occur, which prevents isolation by distance within the spatial scale of 40 km. When comparing continuous stands across the disrupted habitat, an increased genetic differentiation associated with the interruption of the species distribution was observed. A Multiple Correspondence Analysis (MCA) clearly separated the sampling units into 2 groups, each representing a separate stand. Other lines of evidence supporting the idea of genetic disruption came from the mean pairwise differentiation estimates (F-ST) and from the Analyses of Molecular Variance (AMOVA). Finally, the southern edge of the interruption in the distribution of L. nigrescens showed clear signals of a recent founding event, suggesting that northward recolonisation is currently occurring.
Massive prevalence of viral DNA in Ectocarpus (Phaeophyceae, Ectocarpales) from two habitats in the North Atlantic and South Pacific
(2000) Müller, DG; Westermeier, R; Morales, J; Reina, GG; del Campo, E; Correa, JA; Rometsch, E
Ectocarpus, a cosmopolitan genus of filamentous marine brown algae, contains two species, E. siliculosus and E. fasciculatus. Both species are subject to virus infections, which either destroy the host's sporangia or persist in a latent state without visible symptoms. We used PCR amplification of a viral gene fragment to monitor the infection status of Ectocarpus samples from Gran Canaria Island, North Atlantic, and southern Chile over 26 months.
Reduced genetic diversity and increased population differentiation in peripheral and overharvested populations of Gigartina skottsbergii (Rhodophyta, Gigartinales) in southern Chile
(2004) Faugeron, S; Martínez, EA; Correa, JA; Cardenas, L; Destombe, C; Valero, M
This study assesses two hypotheses on the genetic diversity of populations of Gigartina skottsbergii Setchell et Gardner (Rhodophyta, Gigartinales) at the border of the species distribution: 1) peripheral populations display a reduced genetic diversity compared with central populations, and 2) genetic differentiation is higher among peripheral than among central populations. Two peripheral and four central populations were sampled along the Chilean coast and 113 haploid individuals were analyzed using 17 random amplification of polymorphic DNA loci. The genetic diversity was estimated by allele diversity (H-e), allele richness (A), and the mean pair-wise differences among multilocus genotypes. All three estimates consistently and significantly indicated a lower genetic diversity within the peripheral than within the central populations. Genetic differentiation between the two peripheral populations was stronger (F-ST=0.35) than between central populations at similar spatial scales (F-ST ranging from 0 to 0.25). In addition, it appeared from the distribution of pair-wise differences that peripheral populations are in demographic expansion after a recent bottleneck. The results are discussed in the specific context of potential overharvesting of these wild populations.
Ultrastructure and taxonomy of Sporocladopsis novae-zelandiae (Ulvophyceae, Chlorophyta)
(2002) Leonardi, PI; Cáceres, EJ; Correa, JA
The ultrastructure of vegetative and reproductive cells in Sporocladopsis novaezelandiae has been studied for the first time to determine the precise taxonomic position of this genus. Vegetative cells contained one parietal chloroplast with 58 ulvophyceantype pyrenoids and transverse cell walls with plasmodesmata.The growth of the transverse walls was centripetal by furrow ingrowth. Ovoid zoosporangia initially had one nucleus and a large basal vacuole. Zoospore release occurred by the apical disintegration of the zoosporangial wall and expansion of an apical mucilage plug. Emptied zoosporangia could be occupied by a series of successive new zoosporangia developed from the same mother cell. Zoospores were bi or quadriflagellate.The flagellar apparatus showed a 180 rotational symmetry and overlapped basal bodies with bilobed terminal caps covering their proximal ends. Our study permits us to conclude that Sporocladopsis is an ulvophycean genus. This conclusion is based on the occurrence of overlapping basal bodies, cytokinesis by infurrowing, and ulvophycean type of pyrenoids. Bilobed terminal caps and zoospore release by apical disintegration of the cell wall (which is accompanied by expansion of a mucilage plug) in Sporocladopsis suggest affinities with the order Ulvales. However, the absence of plasmodesmata and the absence of percurrent proliferation of zoosporangia in all members of the order Ulvales challenge this taxonomical position.The plasmodesmata in Sporocladopsis are similar to those in the Trentepohliales and could suggest a relationship with the latter, but the typical features of the Trentepohliales are absent in Sporocladopsis and this absence does not support an affinity between Sporocladopsis and the Trentepohliales. In conclusion, the fine structural characters of Sporocladopsis are paradoxical and it is therefore difficult to relate this genus to an order within the class Ulvophyceae. Molecular data of the genus, which are not available at present, would be necessary before making a final taxonomic decision concerning its ordinal position inside the class Ulvophyceae.

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