Esta tesis representa el primer estudio integral de dos poblaciones de Leathesia marina, Phaeophyceae, en la Patagonia argentina. La misma involucra aspectos ecológicos de la especie tales como ciclo de vida, demografía poblacional, estudios fenológicos y de la comunidad de epífitos; así como sus formas de manejo mediante la optimización de su cultivo: control de la fertilidad y caracterización bioquímica del alga, para su posible utilización en la industria farmacéutica o alimentaria. El estudio del ciclo de vida en condiciones de cultivo in vitro, se basó en un enfoque integrado, involucrando observaciones morfológicas, análisis de los niveles de ploidía y estudios moleculares. L. marina presentó un ciclo de vida heteromórfico, que comprende tres morfologías diferentes, dos morfotipos haploides diferentes (gametófito y esporófito), a) un microtalo de morfología globosa, y b) un microtalo postrado y c) un morfotipo diploide (macrotalo o esporófito). Los cambios en el nivel de ploidía durante las diferentes fases del ciclo de vida, se evidenciaron usando citometría de flujo y fluorescencia del DNA. Los análisis filogenéticos basados en cox3 y el conjunto de datos concatenados cox3 y rbcL confirmaron la identidad de los especímenes argentinos como L. marina, que fueron conespecíficos con las poblaciones de L. marina de Nueva Zelanda, Alemania y Japón. A su vez, el estudio fenológico y dinámica poblacional de L. marina en la naturaleza, permitió comprender que el ciclo de vida heteromórfico se encuentra en completa interacción y en respuesta a las presiones selectivas del entorno altamente cambiante de la Patagonia. El talo macroscópico estuvo presente desde septiembre a abril, durante la temporada cálida, mientras que la fase microscópica se observó en dos períodos, marzo-abril y septiembre-octubre, presentando una superposición temporal entre ambas fases. La población del esporofito macroscópico presentó una curva de supervivencia tipo III, las cuales son frecuentes en algas pardas con fases microscópicas, capaces de crecer rápidamente dejando un reclutamiento masivo, seguido de una alta mortalidad. A su vez, la cobertura, la densidad y el tamaño de los macrotalos se relacionaron con los meses más cálidos, pero la capacidad reproductiva fue mayor en los meses más fríos, previo al final de la temporada de los mismos y coincidentemente con la aparición de los microtalos en la naturaleza. Además esta tesis comprende el primer estudio exhaustivo sobre la dinámica temporal de las comunidades epífitas, no solo sobre L. marina, sino que también sobre Colpomenia sinuosa, debido a la morfología análoga de ambas especies y por presentar un papel ecológico similar en la zona intermareal. Esto permitió evaluar el estado sanitario de L. marina y compararlo con otra especie que ocupa el mismo nicho espacial. La comunidad de epífitos se estudió en términos de riqueza, diversidad y abundancia; y su relación con los hospedadores y los factores ambientales. Un total de 31 taxones de epífitas se registraron en ambas especies, las cuales compartieron el 64,5% de las especies epífitas encontradas. Las algas rojas fue el grupo de epifitos con la mayor abundancia en ambos hospedadores y las diatomeas presentaron la mayor riqueza de especies. La riqueza específica fue similar entre ambos hospedadores, pero L. marina presentó menor diversidad y equitatividad y un claro dominio de las especies U. penicilliformis y E. carnea. A causa del interés reciente en la composición de las algas y el arte de cultivarlas por sus beneficios nutricionales y de salud, en esta tesis se analizó la composición bioquímica de L. marina: materia orgánica, alginatos, carbohidratos totales, contenido de proteínas, pigmentos, polifenoles, actividad antioxidante y composición elemental, así como las mejores condiciones de cultivo, evaluando diferentes temperaturas del agua de mar y nutrientes en las fases esporofíticas y gametofíticas. L. marina mostró un contenido relativamente bajo de carbohidratos y proteínas, pero un alto contenido de polifenoles y actividad antioxidante. En los experimentos de cultivo, las mejores condiciones para el cultivo de gametófitos y esporófitos fueron a 8 °C y a 1 PES. El crecimiento de los esporófitos fue mayor que el de los gametófitos. Los gametófitos se pudieron mantener en latencia en condiciones controladas durante 18 meses. El estudio integral realizado en esta tesis, que analiza el ciclo de vida, parámetros demográficos (tasa de mortalidad, supervivencia, rendimiento reproductivo), así como las características morfológicas, puede ayudar a explicar de qué forma las especies como L. marina lograron adaptarse a un ambiente adverso, con grandes cambios estacionales. A su vez el análisis de la composición bioquímica y la optimización de sus cultivos, constituyen las bases fundamentales para realizar un manejo adecuado y sustentable evitando la sobreexplotación de las poblaciones naturales. / This thesis is the first integral study of two Leathesia marina, Phaeophyceae, populations in Argentian Patagonia. It includes ecological aspects of the species, such as, the life cycle, population demography, phenological studies and the community of epiphytes, as well as the optimization of conditions for L. marina culture and management, through fertility control and biochemical characterization of the alga, for its possible use in the pharmaceutical or food industry. The study of the life cycle of Leathesia marina under in vitro culture conditions was based on an integrated approach, involving morphological observations, ploidy levels and molecular studies. Leathesia marina has a heteromorphic life cycle comprising three different morphologies, two morphotypes of the haploid generation (microthallus or gametophyte and sporophyte) and one morphotype of the diploid generation (macrothallus or sporophyte). Changes were observed in the ploidy level during the different phases in the life cycle using DNA flow and fluorescence cytometry. The phylogenetic analyzes based on cox3 and concatenated cox3 and rbcL data set confirmed the identity of the Argentinian specimens as L. marina, which is conspecific with L. marina from New Zealand, Germany and Japan. In turn, the phenological study and population dynamics of L. marina in nature, allowed us to understand that the heteromorphic life cycle of the species is in complete interaction and response to the selective pressures of the highly changing environment of Patagonia. The macroscopic phase was observed from September to April during the warm season, whereas the microscopic phase was observed in two different periods, March–April and September–October. A temporal overlap was observed between the microscopic and macroscopic phases. The macroscopic sporophyte population presented a type III survival curve, which is frequent in brown algae with microscopic phases, capable of growing rapidly and leaving a massive recruitment, followed by high mortality. In turn, the cover, density and size of the macrothalli were related to the warmer months, but reproductive output was higher in the colder months, prior to the end of the season and coincident with the occurrence of the microthalli in nature. In addition, this thesis includes the first exhaustive study on the temporal dynamics of epiphytic communities, not only on L. marina, but also on Colpomenia sinuosa, due to the analogous morphology of both species and for presenting a similar ecological role in the intertidal zone. This makes it possible to evaluate the health status of L. marina and compare it with another species that occupies the same spatial niche. The community of epiphytes was studied in terms of richness, diversity and abundance and their relationships with the environmental factors and host abundance. A total of 31 epiphyte taxa were recorded and it was found that the two hosts shared 64.5% of these epiphytic species. The red algal epiphytic group had the highest abundance on both hosts and the diatoms presented the highest species richness. The specific richness was similar between both hosts, but L. marina presented less diversity and evenness, and there was a clear dominance of the species Urospora penicilliformis and Erythrotrichia carnea. Due to the recent interest in the composition of algae, and the art of farming them for their nutritional and health benefits, this thesis analyzed the biochemical composition of L. marina: organic matter, alginates, total carbohydrates, protein content, pigments, polyphenols, antioxidant activity and elemental composition, as well as the best conditions for optimizing their culture, evaluating the effect of different temperatures and nutrients in the sporophytic and gametophytic phases. L. marina showed a relatively low carbohydrate and protein content, but a high polyphenol content and antioxidant activity. In the culture experiments, the best conditions for gametophyte and sporophyte survival were 8 °C at 1 PES. The growth of the sporophytes was greater than that of the gametophytes. The gametophytes could be maintained in latency under controlled conditions for 18 months. The integral study carried out in this thesis, which analyzes the life cycle, demographic parameters (mortality rate, survival, reproductive performance), as well as the morphological characteristics, can help explain how species such as L. marina manage to adapt to an adverse environment with large seasonal changes. At the same time, the analysis of the biochemical composition and the culture optimization constitute the fundamental bases for adequate and sustainable management, avoiding overexploitation of the natural populations.

Gracilaria caudata J. Agardh is one of the naturally occurring species in Brazil that produce good quality agar. In Rio do Fogo (RN), Brazil, a green variant was discovered in a G. caudata population of predominantly red (wild phenotype) tetrasporophytes. Epiphytes gametophytes on tetrasporophytes have been observed for both strains. Considering the wild and green variant strains in laboratory control conditions, this study: (i) assessed the impacts of epiphyte gametophytes on tetrasporophytes by evaluating the growth rates, the pigment content, and the photosynthetic potential of the tetrasporophytes; (ii) evaluated the amount of time required for the differentiation of cystocarps in free-living gametophytes and epiphyte gametophytes on tetrasporophytes; (iii) evaluated the number of epiphyte gametophytes produced by tetrasporophyte; and (iv) analyzed anatomical aspects of the intersection between the tetrasporophytes and the tetraspores that germinated on the tetrasporophytes. Samples were cultivated for 12 weeks on laboratory conditions. Control samples had epiphyte gametophytes growing on them, while treatment samples had their epiphyte gametophytes removed weekly. Physiological analyses compared control and treatment samples, while anatomical analysis used the control samples only. Considering the tetrasporophyte growth rates before fertility (2nd week), wild strain showed higher values than green variant; however, after 12 weeks, no differences were found between strains or between samples without epiphyte gametophytes. The wild strain produced tetraspores more frequently than the green variant and showed deficiency in phycoerythrin and allophycocyanin. Green variant treatment samples had higher content of allophycocyanin, phycocyanin and phycoerythrin than the control samples. Chlorophyll a was higher in the wild strain, and treatment samples had lower values in comparison to control samples. Epiphyte gametophytes possibly promoted reduction in pigment content of the tetrasporophytes on both strains. Wild strain samples without epiphyte gametophytes had higher photosynthetic efficiency. Epiphyte gametophytes produced cystocarps one week before free-living gametophytes. The amount of epiphyte gametophytes on tetrasporophytes is not different between strains. Epiphyte gametophytes were visible one week before on the wild strain than in the green variant strain. It was found that tetraspores give rise to epiphyte gametophytes through two distinct germination methods: outside or inside the thallus of the tetrasporophyte. Germination outside the tetrasporophyte thallus was more common, produced visible holdfasts and promoted cortex thickening in the cortical region of the tetrasporophyte. Germination inside the tetrasporophyte thallus did not show evidences of holdfasts nor cortex thickening on the tetrasporophytes. Epiphyte gametophytes holdfasts had adjacent cells to the cortex of the tetrasporophytes when they germinate outside the thallus; however, when germination occurred inside the thallus, the connection interface was closer to the medulla of the tetrasporophyte. Epiphyte gametophytes might represent a new life strategy that promotes sexual variability in a population mostly composed of tetrasporophytes. For cultivation purposes, wild tetrasporophytes with epiphyte gametophytes yielded more mass than the variant tetrasporophytes, being the best option for production. However, the green variant without epiphyte gametophytes produced more phycobiliproteins, making it a better option to harvest those substances / Gracilaria caudata J. Agardh é uma das espécies encontradas na costa brasileira que produzem ágar de boa qualidade. Em Rio do Fogo (RN), Brasil, uma linhagem variante verde de G. caudata foi descoberta em uma população composta principalmente por indivíduos de coloração vermelha (fenótipo selvagem). Gametófitos epífitos em tetrasporófitos foram observados para as duas linhagens. Considerando-se as linhagens selvagem e verde em condições controladas de laboratório, este estudo analisou: (i) os impactos dos gametófitos epífitos nos tetrasporófitos por meio de taxas de crescimento, conteúdo pigmentar e potencial fotossintetizante dos tetrasporófitos; (ii) o tempo necessário para a diferenciação de cistocarpos em gametófitos de vida livre e gametófitos epífitos; (iii) o número de gametófitos epífitos produzidos por tetrasporófito; e (iv) aspectos anatômicos da interseção entre tetrasporófitos e gametófitos epífitos. O experimento teve duração de 12 semanas. Amostras controle foram mantidas com seus gametófitos epífitos durante o experimento, enquanto as amostras tratamento tiveram seus gametófitos epífitos removidos semanalmente. Análises fisiológicas compararam amostras controle e tratamento, enquanto que para os estudos anatômicos utilizou-se apenas as amostras controle. A linhagem selvagem apresentou maiores taxas de crescimento que a linhagem verde nas duas primeiras semanas do experimento, quando ainda não estavam férteis; entretanto, após as doze semanas de cultivo, não foram observadas diferenças entre as linhagens tetrasporofíticas. A linhagem vermelha produziu tetrásporos com mais frequência do que a linhagem verde e apresentou deficiência em ficoeritrina e aloficocianina. As amostras tratamento da linhagem verde apresentaram valores maiores de aloficocianina e ficoeritrina do que às do controle. A linhagem selvagem apresentou menores teores de ficoeritrina e aloficocianina quando comparada à linhagem verde. As amostras tratamento da linhagem verde apresentaram maiores valores de aloficocianina, ficocianina e ficoeritrina que as amostras controle da mesma linhagem. A quantidade de clorofila a foi maior na linhagem selvagem, e as amostras tratamento desta linhagem apresentaram valores maiores que às do controle. A presença de gametófitos epífitos promoveu a redução no conteúdo pigmentar nas duas linhagens. Amostras tratamento da linhagem selvagem apresentaram potencial fotossintetizante maior do que amostras controle. A quantidade de gametófitos epífitos não foi diferente entre as linhagens. Gametófitos epífitos produziram cistocarpos uma semana antes do que gametófitos de vida livre. A linhagem selvagem produziu gametófitos epífitas uma semana antes da linhagem verde. A germinação de tetrásporos em tetrasporófitos ocorreu de duas maneiras: antes e após a liberação de tetrásporos. A liberação de tetrásporos seguida da germinação sobre o tetrasporófito foi mais frequente, produziu apressórios e promoveu aumento do número de células no córtex do tetrasporófito. A germinação de tetrásporos dentro do talo do tetrasporófito não apresentou evidências de apressórios ou espessamento da região cortical do tetrasporófito. A porção basal de apressórios de gametófitos epífitos permaneceu adjacente ao córtex do tetrasporófito. Quando a germinação do tetrásporo ocorreu ainda dentro do talo, a interface de conexão das células foi mais próxima da medula do tetrasporófito. Gametófitos epífitos podem representar uma nova estratégia de vida para a espécie por possibilitar a variabilidade por reprodução sexual em uma população predominantemente composta por tetrasporófitos. Para um possível cultivo em larga escala, tetrasporófitos com gametófitos epífitos da linhagem selvagem seriam mais adequados por produzirem mais massa que os da variante verde. Entretanto, se o objetivo for a produção de ficobiliproteínas, a linhagem verde seria a mais indicadaphycoerythrin and allophycocyanin. Green variant treatment samples had higher content of allophycocyanin, phycocyanin and phycoerythrin than the control samples. Chlorophyll a was higher in the wild strain, and treatment samples had lower values in comparison to control samples. Epiphyte gametophytes possibly promoted reduction in pigment content of the tetrasporophytes on both strains. Wild strain samples without epiphyte gametophytes had higher photosynthetic efficiency. Epiphyte gametophytes produced cystocarps one week before free-living gametophytes. The amount of epiphyte gametophytes on tetrasporophytes is not different between strains. Epiphyte gametophytes were visible one week before on the wild strain than in the green variant strain. It was found that tetraspores give rise to epiphyte gametophytes through two distinct germination methods: outside or inside the thallus of the tetrasporophyte. Germination outside the tetrasporophyte thallus was more common, produced visible holdfasts and promoted cortex thickening in the cortical region of the tetrasporophyte. Germination inside the tetrasporophyte thallus did not show evidences of holdfasts nor cortex thickening on the tetrasporophytes. Epiphyte gametophytes holdfasts had adjacent cells to the cortex of the tetrasporophytes when they germinate outside the thallus; however, when germination occurred inside the thallus, the connection interface was closer to the medulla of the tetrasporophyte. Epiphyte gametophytes might represent a new life strategy that promotes sexual variability in a population mostly composed of tetrasporophytes. For cultivation purposes, wild tetrasporophytes with epiphyte gametophytes yielded more mass than the variant tetrasporophytes, being the best option for production. However, the green variant without epiphyte gametophytes produced more phycobiliproteins, making it a better option to harvest those substances