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Culture studies of economically important seaweeds
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Abstract(s)
Na última década a aquacultura de macroalgas marinhas recebeu uma atenção crescente. Nos Açores, apenas recentemente o Governo Regional começou a apoiar o investimento privado no sector da aquacultura. Apesar do interesse existente na exploração dos recursos algais existentes nos Açores, até à data não existe informação publicada sobre a viabilidade do cultivo de macroalgas marinhas na Região. A presente tese visa contribuir para o preenchimento desta lacuna, através da investigação sobre o potencial de cultivo de algumas espécies com interesse comercial. Pretende‐se gerar informação útil para o setor público e privado que garanta práticas responsáveis e eficientes de cultivo de macroalgas, contribuindo para a prevenção da sobre‐exploração dos stocks selvagens e para o desenvolvimento sustentável da indústria das algas nos Açores. Neste contexto, foram investigados: (i) o efeito da limitação da fonte de azoto no crescimento in vitro de juvenis da alga castanha Macrocystis pyrifera (L.) C. Agardh e a sua capacidade de recuperação após o stress induzido: (ii) o potencial de cultivo de da alga vermelha Pterocladiella capillacea (S.G.Gmelin) Santelices & Hommersand e da alga castanha Halopteris scoparia (Linnaeus) Sauvageau), duas espécies de valor económico comprovado e presentes na flora algal açoriana: e (iii) o uso de H. scoparia como biofiltro num sistema piloto integrado de aquacultura multitrófica (IMTA – sigla inglesa para Integrated Multi‐Trophic Aquaculture). No desenvolvimento da tese, foram realizados ensaios laboratoriais e de campo para explorar as respostas fisiológicas das espécies investigadas a fatores abióticos selecionados.
Verificou‐se que a recuperação dos esporófitos juvenis de M. pyrifera após condições limitantes de nutrientes, foi melhor quando estes foram cultivados previamente num meio de cultivo completo (com uma percentagem de sobrevivência de 83.33 ± 3.61 % e taxa de crescimento de 1.08 ± 0.30 % comprimento dia⁻¹). Estes resultados sugerem um aumento da rentabilidade de produção desta espécie, contudo, é necessário a sua demostração à escala industrial antes de implementar a metodologia de cultivo proposta. A alga P. capillacea cresceu melhor quando submetida a densidades de fluxo de fotões mais elevadas (150 μmol fotões m⁻² s⁻¹) e a períodos de aclimatação mais longos (duas a três semanas). Contudo, foi também observada uma diminuição do comprimento do talo, bem como um baixo crescimento durante os ensaios laboratoriais. Estes resultados foram inesperados tendo em conta outros trabalhos publicados para esta espécie. As condições de cultivo testadas tiveram uma taxa de sucesso baixa, e exigirão novas abordagens por forma a validar o potencial de cultivo desta espécie.
A alga H. scoparia cresceu numa gama alargada de densidades de cultivo, luz e temperatura, desde que mantendo a intensidade luminosa abaixo dos 150 μmol fotões m⁻² s⁻¹, condição necessária para minimizar/limitar o crescimento de epífitos. A melhor relação entre taxa de crescimento relativo e produtividade foi obtida a uma densidade de cultivo de 2 g fw L⁻¹, sendo esta a recomendada para desenvolver a produção da espécie. O potencial de cultivo desta espécie para a industria das macroalgas marinhas, num sistema piloto de tanques em IMTA, usando efluentes da produção de dourada, testado aqui pela primeira vez, revelou resultados positivos e promissores. Os melhores resultados foram obtidos a uma densidade de cultivo de 2 g fw dia⁻¹, com uma produtividade semanal de 13.28 ± 2 g dw m⁻² wk⁻¹ e a remoção de 3.63 ± 0.47 g m⁻² dia⁻¹ de amónia (NH₃+NH₄). H. scoparia é, assim, um bom candidato para integrar sistemas de cultivo integrados nestas latitudes. A exploração desta espécie usando biomassa cultivada é possível e a sua produção a uma escala industrial poderá ser, a partir de agora, prevista pela indústria.
A presente tese permitiu a produção de informação científica importante quer para uso académico, quer económico, que potencialmente poderá ser usada para o desenvolvimento sustentável do sector das algas marinhas nos Açores.
ABSTRACT: Seaweed aquaculture has received increased attention in Europe in the last decade. In the Azores, only recently the Regional Government has started supporting private investment in the aquaculture sector. Despite the interest in exploiting Azorean seaweed resources, until now there was no published information on the feasibility of seaweed cultivation in the Region. The present thesis aims to fulfil this lack of information, by investigating the cultivation potential of selected species, and to provide useful information for a responsible seaweed cultivation practices within the private sector. This will contribute to prevent the overexploitation of the Azorean wild algal stock and to ensure the sustainable development of the seaweed industry in the Azores. In this context, this thesis investigates: (i) the effect of nitrogen (N) limitation on the in vitro growth of the brown alga Macrocystis pyrifera (L.) C. Agardh juveniles and their capacity to recover after nitrogen limitation; (ii) the cultivation potential of the red alga Pterocladiella capillacea (S.G.Gmelin) Santelices & Hommersand, and the brown alga Halopteris scoparia (Linnaeus) Sauvageau), two commercial and ecologically important species of the Azorean algal flora; and (iii) the potential of H. scoparia as a biofilter component in a pilot‐scale Integrated Multi‐Trophic (IMTA) land‐based system. Throughout the thesis, laboratory and outdoor trials were developed to explore the physiological responses of the investigated species to selected abiotic factors. Juvenile sporophytes of M. pyrifera seen to recover better from low nutrient stress conditions when they were previously cultivated in full culture medium (with 83.33 ± 3.61% survival and a growth rate of 1.08 ± 0.30% length day⁻¹). This suggests a possible increase in success and profitability of kelp farming, although full commercial scale field tests are still required before effective implementation of the proposed seedling methodology. The best growth performance for P. capillacea was obtained at a photon flux density of 150 μmol photons m⁻² s⁻¹ and with a longer acclimation period (two to three‐weeks). Nevertheless, a decrease in length or a very low growth observed, an unexpected result that differs from other authors’ reports. This result indicates that the experimental growth trials were not successful and demand more in depth research to validate the cultivation potential of this species. H. scoparia grew healthy in a wide range of stocking densities (SD), light and temperature conditions, providing irradiance was maintained under 150 μmol photons m⁻² s⁻¹ to restrain the development of epiphytes. The best growth/productivity relationship attained at a SD of 2 g fw L⁻¹ that indicates these conditions as ideal to pursuit cultivation upscale of the species. The potential of producing this species in a land‐based tank system using seabream effluents, investigated here for the first time, revealed that it is possible to cultivate H. scoparia in such a system within the conditions tested. The best results were achieved at a stocking density of 2 g fw day⁻¹ reaching a weekly productivity of 13.28 ± 2 g dw m⁻² wk⁻¹ and removing 3.63 ± 0.47 g m⁻² day⁻¹ of total ammonium nitrogen. This brown alga is, therefore, a good candidate to land‐based IMTA culture systems set at these latitudes. The commercial cultivation of this species’ biomass is possible and seaweed farmers can now foresee upscaling its production. The present thesis generated important information for both academic and economic purposes that may be of use in the sustainable development of seaweed industry sector in the Azores.
ABSTRACT: Seaweed aquaculture has received increased attention in Europe in the last decade. In the Azores, only recently the Regional Government has started supporting private investment in the aquaculture sector. Despite the interest in exploiting Azorean seaweed resources, until now there was no published information on the feasibility of seaweed cultivation in the Region. The present thesis aims to fulfil this lack of information, by investigating the cultivation potential of selected species, and to provide useful information for a responsible seaweed cultivation practices within the private sector. This will contribute to prevent the overexploitation of the Azorean wild algal stock and to ensure the sustainable development of the seaweed industry in the Azores. In this context, this thesis investigates: (i) the effect of nitrogen (N) limitation on the in vitro growth of the brown alga Macrocystis pyrifera (L.) C. Agardh juveniles and their capacity to recover after nitrogen limitation; (ii) the cultivation potential of the red alga Pterocladiella capillacea (S.G.Gmelin) Santelices & Hommersand, and the brown alga Halopteris scoparia (Linnaeus) Sauvageau), two commercial and ecologically important species of the Azorean algal flora; and (iii) the potential of H. scoparia as a biofilter component in a pilot‐scale Integrated Multi‐Trophic (IMTA) land‐based system. Throughout the thesis, laboratory and outdoor trials were developed to explore the physiological responses of the investigated species to selected abiotic factors. Juvenile sporophytes of M. pyrifera seen to recover better from low nutrient stress conditions when they were previously cultivated in full culture medium (with 83.33 ± 3.61% survival and a growth rate of 1.08 ± 0.30% length day⁻¹). This suggests a possible increase in success and profitability of kelp farming, although full commercial scale field tests are still required before effective implementation of the proposed seedling methodology. The best growth performance for P. capillacea was obtained at a photon flux density of 150 μmol photons m⁻² s⁻¹ and with a longer acclimation period (two to three‐weeks). Nevertheless, a decrease in length or a very low growth observed, an unexpected result that differs from other authors’ reports. This result indicates that the experimental growth trials were not successful and demand more in depth research to validate the cultivation potential of this species. H. scoparia grew healthy in a wide range of stocking densities (SD), light and temperature conditions, providing irradiance was maintained under 150 μmol photons m⁻² s⁻¹ to restrain the development of epiphytes. The best growth/productivity relationship attained at a SD of 2 g fw L⁻¹ that indicates these conditions as ideal to pursuit cultivation upscale of the species. The potential of producing this species in a land‐based tank system using seabream effluents, investigated here for the first time, revealed that it is possible to cultivate H. scoparia in such a system within the conditions tested. The best results were achieved at a stocking density of 2 g fw day⁻¹ reaching a weekly productivity of 13.28 ± 2 g dw m⁻² wk⁻¹ and removing 3.63 ± 0.47 g m⁻² day⁻¹ of total ammonium nitrogen. This brown alga is, therefore, a good candidate to land‐based IMTA culture systems set at these latitudes. The commercial cultivation of this species’ biomass is possible and seaweed farmers can now foresee upscaling its production. The present thesis generated important information for both academic and economic purposes that may be of use in the sustainable development of seaweed industry sector in the Azores.
Description
Tese de Doutoramento, Biologia, 14 de dezembro de 2018, Universidade dos Açores.
Keywords
Halopteris scoparia Macrocystis pyrifera Pterocladiella capillacea Aquacultura Biorremediação Macroalgas Marinhas Açores Bioremediation Seaweeds Azores
Citation
Patarra, Ana Rita Ferreira. "Culture studies of economically important seaweeds". 2018. 178 p.. (Tese de Doutoramento em Biologia). Ponta Delgada: Universidade dos Açores, 2017. [Consult. Dia Mês Ano]. Disponível em www:<http://hdl.handle.net/10400.3/5097>.