Daniel Varela

SPORELING COALESCENCE AND INTRACLONAL VARIATION IN GRACILARIA CHILENSIS (GRACILARIALES, RHODOPHYTA)

This study evaluates the hypothesis that spore coalescence may cause intraclonal variation. Spore coalescence might allow the occurrence of unitary thalli that in fact correspond to genetically different, coalesced individuals. Plant portions simultaneously derived from these chimeric individuals may exhibit dissimilar growth responses even when incubated under similar abiotic conditions. Testing of the hypothesis included various approaches. Transmission electron microscopy observations of early stages of sporeling coalescence indicated that polysporic plantlets were formed by groups of spores and their derivatives. Even though adjacent cells in two different groups may fuse, these groups maintained an independent capacity to grow and form uprights. Laboratory‐grown plantlets showed a significant correlation between the initial number of spores and the total number of erect axes differentiated from the sporeling. Construction and growth of bicolor individuals indicated the chimeric nature of the coalesced individuals. Coalesced, bicolor holdfasts had green and red cells, which subsequently produced green and red uprights, respectively. Individuals fronds were also chimeric, as indicated by the production of green and red branchlets from single, red uprights. The existence of mixed tissues was further substantiated by random amplified polymorphic DNA analysis. The banding pattern produced by branchlets of a unisporic thallus was consistently monomorphic, whereas the patterns produced by the polysporic thallus were polymorphic. Growth rates of polysporic thalli had larger data dispersal and variation coefficients than oligosporic or monosporic thalli. Therefore, all results support the original hypothesis and suggest that coalescence might be ecologically more important than previously thought.

Seaweed future cultivation in Chile: perspectives and challenges

Production of seaweeds in Chile has fluctuated between 120,000 and 316,000 wet metric tons per year during the last ten years. The most important Phaeophyta are exploited for alginate production and as abalone feed. Among the Rhodophyta, Chilean production comes mainly from wild stocks, as at present cultivation on a commercial scale is restricted to Gracilaria. Large-scale production of this species has been the result of a sharp increase in the number of farms. During the last five years an important trend towards diversification of seaweed exploitation and cultivation has developed. The demand for brown algal materials for the alginate industry, abalone cultivation, seaweed flour production for human and animal feeding and the development of novel food products has encouraged the farming of Macrocystis pyrifera and of red edible seaweeds, such as Chondracanthus chamissoi and Callophyllis variegata, is also promoting the development of cultivation activities.

Causes and implications of intra-clonal variation in Gracilaria chilensis (Rhodophyta)

Strain selection studies in Gracilaria chilensis detected significant levels of intra-clonal variation. These findings motivated more detailed studies on the causes and implications of intra-clonal variation in these and other red algal species. Our results indicate that intra-clonal variation is common among replicated units (e.g.: carpospores and ramets) of several red algal species and suggest that a larger data base probably will show the occurrence of various kinds of intra-clonal changes, differing in frequency of occurrence and magnitude of phenotypic expression. It is likely also that different species would exhibit different amounts of variation. Four types of factors may cause intra-clonal variation: (1) physiological or developmental differences among ramets, (2) localized pathogen infections, (3) several kinds of genetic changes, and (4) sporeling coalescence. Intra-clonal variation among ramets: (1) increases the possibility of genet survival, (2) explains the origin of morphological and physiological differences among ramets of a given genet, (3) explains the large population variation found in many clonal species and (4) suggests that strain selection of some economically important seaweeds should be thought of as a fairly continuous process due to the instability of some of these clones.

Regenerative capacity of Gracilaria fragments : effects of size, reproductive state and position along the axis

Field farming of Gracilaria chilensis in Chile is mainly based on the regenerative capacity of thallus fragments. This study evaluates experimentally the effects on growth of the few organismic determinants that the farmer is capable of effectively handling in the field. No differences were found in the length increments of ramets with and without apices, a surprising result in view of the generally accepted idea that the most important growth meristem in this group of algae is located in the apex of the thallus. Total elongation and increase in weight of fragments with an initial length of up to 20 cm are a function of the initial length of the ramet, suggesting that intercalary growth makes a significant contribution to growth. Vegetative female axes grow faster, (in terms of length and weight) and produce more laterals than fertile female axes, and these faster than fertile tetrasporic branches. No differences in the growth of ramets originating from proximal or distal parts of axes were found.

The Status of Kelp Exploitation and Marine Agronomy, with Emphasis on Macrocystis pyrifera, in Chile

Kelp cultivation started in Japan, China and Korea, mainly for human consumption; new applications are still expanding. In Chile, three ‘wild’ Lessonia species and Macrocystis pyrifera are under a strong and increasing pressure of exploitation mainly for alginate production and as a source of feed for abalone. Regulatory restrictions for kelp exploitation and the increased demand for biomass provided a positive environment for the installation of a kelp farming industry. Pilot-production studies demonstrated that 200 tonnes (fresh)/ha/year can be achieved and genetic diversity and breeding studies suggested that this volume could be increased. Kelp disease research is a necessary condition for securing the future development of this industry, as are environmental studies on the impacts of large-scale aquaculture. Beyond the positive bioremediation, ecosystem service effects that kelp farming can provide, especially in a region such as in southern Chile, where intensive salmon and mussel cultivation occurs. Life Cycle Assessment suggests that the energy returns on investment in kelp farming are positive, but more detailed data are still required.

Spatial and temporal variation of photosynthesis in intertidal Mazzaella laminarioides (Bory) Fredericq (Rhodophyta, Gigartinales)

The red alga Mazzaella laminarioides is an economically important species with an extended latitudinal distribution along the Chilean coast. Its populations form mid-intertidal stands, several meters wide, and therefore are differentially exposed to environmental variables that result in temporal and spatial variability in productivity. We evaluated the effect of latitude and intertidal height on productivity by in situ measurement of photosynthetic performance. Daily and seasonal variations of O2-evolution rate and maximal quantum yield (Fv/Fm) were determined in plants from the upper and lower intertidal zone at two localities 1500,km apart. Results suggest that plant responses were mainly affected by irradiation, temperature and desiccation. At local level, upper intertidal plants showed a reduced photosynthetic rate and quantum efficiency as compared to those displayed by plants from the lower intertidal, indicating their higher level of excitation energy acclimation. Stronger acclimation differences between upper and lower intertidal plants were observed in spring and summer. Differences in photosynthetic parameters between reproductive phases were recorded in autumn and winter, regardless of the position of the individuals in the intertidal zone. The effects of tidal elevation on seasonal patterns of photosynthesis were also influenced by latitude. Seasonal variation in photosynthetic efficiency was observed in plants from the northern population at both intertidal elevations, but only at the upper intertidal level in the southern population. This study shows that production variability in M. laminarioides results from differences in the intensity of environmental factors observed seasonally at local (intertidal) and latitudinal scales.

Role of resting cysts in Chilean Alexandrium catenella dinoflagellate blooms revisited

The detection of sparse Alexandrium catenella-resting cysts in sediments of southern Chilean fjords has cast doubts on their importance in the recurrence of massive toxic dinoflagellate blooms in the region. The role of resting cysts and the existence of different regional Chilean populations was studied by culturing and genetic approaches to define: (1) cyst production; (2) dormancy period; (3) excystment success; (4) offspring viability and (5) strain mating compatibility. This study newly revealed a short cyst dormancy (minimum 69 days), the role of key abiotic factors (in decreasing order salinity, irradiance, temperature and nutrients) controlling cyst germination (max. 60%) and germling growth rates (up to 0.36-0.52div.day-1). Amplified fragment length polymorphism (AFLP) characterization showed significant differences in genetic distances (GD) among A. catenella populations that were primarily determined by the geographical origin of isolates and most likely driven by oceanographic dispersal barriers. A complex heterothallic mating system pointed to variable reproductive compatibility (RCs) among Chilean strains that was high among northern (Los Lagos/North Aysén) and southern populations (Magallanes), but limited among the genetically differentiated central (South Aysén) populations. Field cyst surveys after a massive 2009 bloom event revealed the existence of exceptional high cyst densities in particular areas of the fjords (max. 14.627cystscm-3), which contrast with low cyst concentrations (<221.3cystscm-3) detected by previous oceanographic campaigns. In conclusion, the present study suggests that A. catenella resting cysts play a more important role in the success of this species in Chilean fjords than previously thought. Results from in vitro experiments suggest that pelagic-benthic processes can maintain year-round low vegetative cell concentrations in the water column, but also can explain the detection of high cysts aggregations after the 2009-bloom event. Regional drivers that lead to massive outbreaks, however, are still unknown but potential scenarios are discussed.

IDENTIFICATION OF THE TOXIC ALGA ALEXANDRIUM TAMIYAVANICHI (DINOPHYCEAE) FROM NORTHEASTERN BRAZIL: A COMBINED MORPHOLOGICAL AND rDNA SEQUENCE (PARTIAL LSU AND ITS) APPROACH1

Morphological and phylogenetic analyses and sequencing of the partial LSU gene and internal transcribed spacer (ITS) regions of the rDNA gene were combined to study toxic strains of Alexandrium tamiyavanichi Balech collected from northeastern Brazilian coastal waters. All specimens were identified with A. tamiyavanichi mainly based on the shape of the anterior sulcal plate (S.a.), which was the most conservative character. Among the specimens studied, 8% did not conform to the morphological description of A. tamiyavanichi. The occurrence of transitory states between A. tamiyavanichi and Alexandrium cohorticula (Balech) Balech tended to confirm that both species are conspecific. The posterior sulcal plate (S.p.) was not a good taxonomic character as variability in its shape did not allow a clear assignment of specimens from the same clonal isolate to either morphologically defined species. Phylogenetic analyses confirmed the overall validity of morphological characters to delineate the evolutionary relationships among the clades of Alexandrium species analyzed here, indicating that A. tamiyavanchi is a valid species according to the morphological species concept. This analysis showed that the Brazilian strains form a monophyletic clade with Asiatic strains of A. tamiyavanichi, but with enough genetic distance to argue for long‐term separation and isolation of locally established populations, extending the known biogeographic range of this species. On the higher phylogenetic level, our data also indicate that Alexandrium tropicale Balech forms part of the clade otherwise consisting of the morphologically defined freterculus group, and this A. tamiyavanichi/tropicale/fraterculus (Balech) Balech clade (including species from the formerly termed tropical Asian [TROP] clade) may be considered as a sister group of the Alexandrium tamarense species complex.