In the future, the cultivation of algae for food may become increasingly important in Sweden. But this area is still new in Europe and most of the harvest today comes from wild stocks. In Sweden, cultivation is only available on the west coast, but research is underway to see if it is possible to start cultivating macroalgae in the Baltic Sea as well. The Baltic Sea has completely different biological conditions than the west coast, and one of the challenges is the low salinity, which limits the species that can live in the Baltic Sea. This is something that the Marine Center in Simrishamn is also researching in the project Tångkusten, of which this study is a part of. The purpose of this study is to use a literature study to compile available knowledge about which algae that has the potential to be cultivated in the future and what the life cycles of these algae look like. An inventory of the macroalgae found locally in Hanöbukten was also carried out. Based on this information, possible cultivation methods and the advantages of each species are discussed, but also the challenges that may arise.  The results showed that the most abundant species were filamentous brown algae, bladder wrack and saw wrack . The species deemed most cultivable are gut weed and sea lettuce. Clawed fork weed, bladder wrack and saw wrack are also considered to have some cultivation potential. Among the biggest challenges are the growth of epiphytic algae and finding a suitable site for cultivation. / Projektet Tångkusten på Marint centrum i Simrishamn

In order to evaluate the effect of seaweeds in bio-filtration for removing nitrogen from marine aquaculture and in bioenergy production, Ulva sp. was used in this study. Experiments were triplicated and run in 3-day incubation at salinities with 30 psu, 10 psu and 5 psu in different initial ammonium nitrogen concentrations from 100 μM to 10,000 μM, equivalently to marine aquaculture conditions. The highest concentrations of ammonium removed were about 690 μmol (12.42 mg) NH4+ at 30 psu, 410 μmol (7.38 mg) NH4+ at 10 psu and 350 μmol NH4+(6.3 mg NH4+) at 5 psu in three days of incubation, while highest growth rates of Ulva sp. were 49% and 150% per day at 500 μM of initial ammonium concentration, similarly to the growth rate reported in microalgae. Moreover, after these experiments, biomass of Ulva sp. has been tested for bioenergy producing goals, because the carbohydrate concentration of this alga was very high, reaching 60-70% of DW. Thus, Ulva sp. can be cultured to remove nitrogen concentration in eutrophication conditions at aquaculture systems in combination with the purpose of bioenergy production after harvesting. / Để đánh giá hiệu quả của tảo biển trong việc lọc sinh học loại bỏ hợp chất ni tơ từ việc nuôi trồng thủy sản và trong việc sản xuất năng lượng sinh học, Ulva sp. đã được sử dụng trong nghiên cứu này. Các thí nghiệm được lặp lại 3 lần và chạy trong 3 ngày trong tủ ổn nhiệt tại các điều kiện độ mặn 30psu, 10psu, 5psu ở các nồng độ NH4+-N từ 100μM đến 10.000μM, tương đương với điều kiện nuôi trồng thủy sản nước mặn. Nồng độ cao nhất của NH4+-N được loại bỏ khoảng 690 μmol NH4+(12,42mg NH4 +) tại 30psu, 410μmol NH4+(7,38mg NH4+) tại 10psu và 350 μmol NH4+(6.3mg NH4+) tại 5psu, trong đó tỉ lệ sinh trưởng của Ulva sp. là rất cao, sinh trưởng từ 49 đến 150% mỗi ngày tại nồng độ ammonium ban đầu 500 μM tương đương với sinh trưởng của vi tảo. Hơn nữa, sau các thí nghiệm trên, sinh khối của Ulva sp. được thử nghiệm sản xuất năng lượng sinh học vì hàm lượng carbohydrate trong tảo rất cao, chiếm khoảng 60-70% trọng lượng khô của tảo. Như vậy, Ulva sp. có thể được nuôi trồng để loại bỏ hợp chất ni tơ trong điều kiện phú dưỡng của các hệ thống nuôi trồng thủy sản, kết hợp với mục tiêu sản xuất năng lượng sinh học sau thu hoạch.

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2016-04-28T18:18:17Z No. of bitstreams: 1 Tese Clarissa Lourenço de Araujo.pdf: 7002934 bytes, checksum: 52d368f8ad6a751f994f7846928d0854 (MD5) / Made available in DSpace on 2016-04-28T18:18:17Z (GMT). No. of bitstreams: 1 Tese Clarissa Lourenço de Araujo.pdf: 7002934 bytes, checksum: 52d368f8ad6a751f994f7846928d0854 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geociências-Geoquímica. Niterói, RJ / Este estudo teve como objetivo contribuir para caracterização do processo de incorporação biológica de metais por duas espécies fitobentônicas, a macroalga Ulva sp. e a macrófita aquática Ruppia maritima, para subsidiar futuras atividades de monitoramento da contaminação da biota aquática da Lagoa Rodrigo de Freitas por metais, bem como de outros sistemas costeiros com condições semelhantes. Este estudo baseou-se na realização de experimentos laboratoriais com o radiotraçador 51Cr (nas formas tri e hexavalente) e com Cr, Cu, Hg, Mn, Pb e Zn, para caracterizar a cinética de incorporação destes pelas duas espécies fitobentônicas. As amostras coletadas na Lagoa Rodrigo de Freitas, foram aclimatadas em laboratório e posteriormente submetidas a experimentos onde foram simuladas condições de mistura de águas salinas e fluviais com água marinha artificial de salinidades 7, 15 e 21‰ e de eventos de aumento dos níveis de matéria orgânica na coluna d’água através da adição de ácidos húmicos. A fim de elucidar os processos de sorção e incorporação de metais foram aplicadas ainda, técnicas de remoção de biofilme e de limpeza do material biológico em solução de EDTA. Nos ensaios com 51Cr (III e IV) foi observada que acumulação do metal por Ulva sp. possui relação inversa com a salinidade, enquanto para R. maritima, o máximo de acumulação ocorre em salinidade 21‰. Nos experimentos com adição simultânea de metais foi observada a seguinte ordem de abundância Pb>Zn>Hg>Cu>Mn>Cr. A maior acumulação dos metais foi observada em salinidade 15‰, com exceção apenas do Hg que apresentou máximo de incorporação em salinidade 21% para alga. Nos ensaios com adição de substâncias húmicas foi evidenciada a redução da incorporação de Cu, Pb e Zn por ambas espécies. No tocante ao potencial de acumulação, foi verificada a maior habilidade de sorção de metais por Ulva sp., independentemente da faixa de salinidade aplicada. Nos ensaios de remoção do biofilme aderido a R. maritima foi observada a redução das concentrações de Cu, Mn e Pb, reforçando o papel deste componente na acumulação de íons metálicos por macrófitas aquáticas. Por fim, no ensaio em que o material biológico foi lavado em solução de EDTA, foi observada a tendência de adsorção superficial de Cu, Mn e Pb, enquanto Cr e Zn, são rapidamente internalizados nos tecidos da macrófita. / This study aims to contribute to the characterization of the process of biological incorporation of metals by two benthonic species, the macroalgae Ulva sp. and the aquatic macrophyte Ruppia maritima, to subsidize future activities of monitoring the contamination of aquatic biota of the Rodrido de Freitas Lagoon for metals, as well as other coastal systems with similar conditions. This study was based on laboratory experiments with the radiotracer 51Cr (in forms tri and hexavalent) and with Cr, Cu, Hg, Mn, Pb and to characterize the kinetics of incorporation of these by two phytobentic species. Samples collected in the Rodrigo de Freitas Lagoon were acclimated in the laboratory and subsequently subjected to experiments where conditions of saline and river water mixed with artificial marine water with salinities of 7, 15 and 21‰ were simulated as well as events that increase the levels of organic matter in the water column through the addition of humic acids. In order to elucidate the processes of sorption and incorporation of metals, techniques for the removal of biofilm and the cleaning of biological material in EDTA solution were also applied. In tests with 51Cr (III and IV) it was observed that accumulation of the metal in Ulva sp. has inverse relationship with salinity, while for R. maritima, the maximum accumulation occurs in salinity 21 ‰. In the experiments with simultaneous addition of metals, the following order of abundance was observed Pb>Zn>Hg>Cu>Mn>Cr. The higher accumulation of metals was observed in salinity 15 ‰, with the exception of Hg that showed maximum incorporation in salinity 21% for algae. In tests with addition of humic substances, the reduction in the incorporation of Cu, Pb and Zn both species was evidenced. In regards to the potential for accumulation, it was verified the greater capability of sorption of metals by Ulva sp., regardless of range of salinity applied. In tests of removal of biofilm attached to R. maritima, the reduction of concentrations of Cu, Mn and Pb was observed, reinforcing the role of this component in the accumulation of metal ions by aquatic macrophytes. Finally, in the biological test material that was washed in EDTA solution, the tendency of surface adsorption of Cu, Mn and Pb was observed, while Cr and Zn are rapidly internalized in the tissues of macrophyte.

The choice of a place to live and reproduce is crucial for species� survival in providing them with adequate resources and shelter from predators or climatic conditions. Determining habitat suitability in endangered species is important for the success of translocation as a conservation tool. In addition, understanding mechanisms (source/sink system versus ecological traps) that drive habitat selection in translocated animals may be critical to population viability. In New Zealand, where ecosystems are highly vulnerable to extinction, habitat restoration on predator-free off-shore islands is an important recovery tool. Therefore, there is a need to understand the relationship between the establishment of the translocated populations and the characteristics of their new environment. Previous research indicated that re-introduced populations of Stewart Island robin (Petroica australis rakiura - Toutouwai) and South Island saddleback (Philesternus carunculatus carunculatus - Tieke) on Ulva Island (Stewart Island), New Zealand, showed preferences for coastal habitats that were characterized by low-lying dense vegetation and open ground cover. In this study, we further investigated territorial establishment in these two populations since re-introduction and looked at how birds utilised the landscape. I hypothesised that sites colonised soon after re-introduction were of high quality and later on, birds moved into unsuitable habitats. I defined habitat quality at a micro-scale in terms of vegetation structure, nest characteristics and food availability. I modeled bird presence and nesting success in relation to habitat components to determine factors in the environment that influenced breeding site selection and contributed to successful nesting in these two species. I discussed results in comparison to similar bird-habitat models developed for the South Island saddleback population on Motuara Island (Marlborough Sounds) and examined explanatory variables in each model. Translocated birds in the three studied populations first established territories in coastal scrub, and in the following years moved into larger coastal forest stands. Although vegetation structure was the primary variable explaining site selection in these populations, vegetation composition should still be considered important as it dictated the suitability of nesting substrate and the availability of food items. There was no evidence that first-colonised areas were more suitable habitats, and I concluded that these cases could not be used as examples of ecological traps. Instead, results suggested that with increased density robins and saddlebacks on Ulva have more recently settled in sites less suitable to nesting and foraging, thus underlying a source/sink structure. However, the sparse distribution of food items on Motuara contributed to a lack of territorial behavior and environmental effect on breeding success; therefore a source/sink system could not be confirmed in this population. I recommended that future translocation sites give preference to mixed-size stands with broadleaved species that are characterised by dense canopy below 4 m height and with suitable cavities in live trees. Lastly, due to robins� and saddlebacks� attraction to conspecifics and their territorial behavior, resources evenly distributed across the landscape could also increase their survival and reproductive success.

<p>Concentrations of various metals are elevated above background levels in several intertidal areas along the Tanzanian coasts. However, there is little available information concerning the toxicity of these metals and how the uptake of these metals by bioindicators are influenced by external factors, such as heavy rains and increased coastal eutrophication, which tend to fluctuate.</p><p>The present study focused on the uptake and toxicity of Cu and Zn in two common macroalgal species,<i> Padina gymnospora</i> (Phaeophyta) and<i> Ulva</i> <i>reticulata</i> (Chlorophyta). Laboratory studies were performed where metal content, growth (DGR), maximal quantum yields (Fv/Fm) and protein expression patterns (in <i>Ulva</i>) were measured as a response to exposure to Cu and Zn. The levels of metals accumulated in algal tissues correlated well to exposure concentrations and the longer the exposure time, the greater the uptake. However, an increased nutrient load (tested on <i>Padina</i>) or dilution of the seawater (tested on<i> Ulva</i>) affected both uptake of metals and their toxic effects. Here, DGR was more affected than Fv/Fm, suggesting DGR to be the more sensitive indicator of Cu and Zn toxicity. As shown by 2-D gel electrophoresis, more than ten proteins were up-regulated in <i>U. reticulata</i> after being exposed to Cu (1μg/L), while at higher concentrations (10 and 100 μg/L) of Cu numerous proteins were down-regulated.</p><p><i>P. gymnospora </i>was also used as a bioindicator to monitor long-term (1994–2005) and seasonal in-year variations in heavy metal concentrations in the Zanzibar Channel. No clear overall trends were revealed, but analysis of the combined dataset clearly pinpointed the most contaminated sites. It was concluded that seasonal and long-term variations, as well as environmental conditions need to be taken into consideration when using macroalgae as bioindicators.</p>

Concentrations of various metals are elevated above background levels in several intertidal areas along the Tanzanian coasts. However, there is little available information concerning the toxicity of these metals and how the uptake of these metals by bioindicators are influenced by external factors, such as heavy rains and increased coastal eutrophication, which tend to fluctuate. The present study focused on the uptake and toxicity of Cu and Zn in two common macroalgal species, Padina gymnospora (Phaeophyta) and Ulva reticulata (Chlorophyta). Laboratory studies were performed where metal content, growth (DGR), maximal quantum yields (Fv/Fm) and protein expression patterns (in Ulva) were measured as a response to exposure to Cu and Zn. The levels of metals accumulated in algal tissues correlated well to exposure concentrations and the longer the exposure time, the greater the uptake. However, an increased nutrient load (tested on Padina) or dilution of the seawater (tested on Ulva) affected both uptake of metals and their toxic effects. Here, DGR was more affected than Fv/Fm, suggesting DGR to be the more sensitive indicator of Cu and Zn toxicity. As shown by 2-D gel electrophoresis, more than ten proteins were up-regulated in U. reticulata after being exposed to Cu (1μg/L), while at higher concentrations (10 and 100 μg/L) of Cu numerous proteins were down-regulated. P. gymnospora was also used as a bioindicator to monitor long-term (1994–2005) and seasonal in-year variations in heavy metal concentrations in the Zanzibar Channel. No clear overall trends were revealed, but analysis of the combined dataset clearly pinpointed the most contaminated sites. It was concluded that seasonal and long-term variations, as well as environmental conditions need to be taken into consideration when using macroalgae as bioindicators.

The choice of a place to live and reproduce is crucial for species� survival in providing them with adequate resources and shelter from predators or climatic conditions. Determining habitat suitability in endangered species is important for the success of translocation as a conservation tool. In addition, understanding mechanisms (source/sink system versus ecological traps) that drive habitat selection in translocated animals may be critical to population viability. In New Zealand, where ecosystems are highly vulnerable to extinction, habitat restoration on predator-free off-shore islands is an important recovery tool. Therefore, there is a need to understand the relationship between the establishment of the translocated populations and the characteristics of their new environment. Previous research indicated that re-introduced populations of Stewart Island robin (Petroica australis rakiura - Toutouwai) and South Island saddleback (Philesternus carunculatus carunculatus - Tieke) on Ulva Island (Stewart Island), New Zealand, showed preferences for coastal habitats that were characterized by low-lying dense vegetation and open ground cover. In this study, we further investigated territorial establishment in these two populations since re-introduction and looked at how birds utilised the landscape. I hypothesised that sites colonised soon after re-introduction were of high quality and later on, birds moved into unsuitable habitats. I defined habitat quality at a micro-scale in terms of vegetation structure, nest characteristics and food availability. I modeled bird presence and nesting success in relation to habitat components to determine factors in the environment that influenced breeding site selection and contributed to successful nesting in these two species. I discussed results in comparison to similar bird-habitat models developed for the South Island saddleback population on Motuara Island (Marlborough Sounds) and examined explanatory variables in each model. Translocated birds in the three studied populations first established territories in coastal scrub, and in the following years moved into larger coastal forest stands. Although vegetation structure was the primary variable explaining site selection in these populations, vegetation composition should still be considered important as it dictated the suitability of nesting substrate and the availability of food items. There was no evidence that first-colonised areas were more suitable habitats, and I concluded that these cases could not be used as examples of ecological traps. Instead, results suggested that with increased density robins and saddlebacks on Ulva have more recently settled in sites less suitable to nesting and foraging, thus underlying a source/sink structure. However, the sparse distribution of food items on Motuara contributed to a lack of territorial behavior and environmental effect on breeding success; therefore a source/sink system could not be confirmed in this population. I recommended that future translocation sites give preference to mixed-size stands with broadleaved species that are characterised by dense canopy below 4 m height and with suitable cavities in live trees. Lastly, due to robins� and saddlebacks� attraction to conspecifics and their territorial behavior, resources evenly distributed across the landscape could also increase their survival and reproductive success.

Ces travaux de thèse CIFRE, réalisés au sein du Laboratoire de Biotechnologie et Chimie Marines de l’Université de Bretagne-Sud et du Groupe Olmix, s’inscrivent dans le cadre d’un projet national de valorisation de biomasses d’algues vertes, le projet ULVANS. Ce projet est le fruit d’une collaboration entre cinq industriels bretons et deux laboratoires universitaires. Les objectifs de ces travaux de thèse concernent i) la caractérisation approfondie de la matière première, en particulier des polysaccharides matriciels solubles (ulvanes) et des protéines, ii) la mise au point d’un procédé d’extraction assistée par enzymes des métabolites algaux, iii) la caractérisation biochimique et moléculaire des hydrolysats enzymatiques, avec pour objectif la compréhension de l’effet des enzymes commerciales sur les algues, iv) l’évaluation des activités antioxydantes et antivirales des hydrolysats, v) l’étude de l’influence des paramètres d’hydrolyse en vue de déterminer les conditions optimales pour l’extraction des métabolites d’intérêt et enfin vi) de conclure, à partir des éléments fournis par l’étude, sur la viabilité d’un tel procédé à l’échelle industrielle. En conclusion de ces travaux, l’hydrolyse enzymatique apparait comme un procédé intéressant pour le bioraffinage des algues vertes. Bien que les préparations enzymatiques commerciales utilisées ne soient pas spécifiques des composés algaux, les protéases ont conduit à une augmentation significative des rendements d’extraction, alors que l’effet des carbohydrases reste modéré. L’étude de l’influence des paramètres d’hydrolyses a confirmé les résultats préliminaires et montré que la température, la concentration d’enzyme et la méthode de broyage présentaient peu d’effets sur les activités des protéases testées. Un résultat majeur de cette étude aura été la mise en évidence d’activités anti-herpétiques dans les hydrolysats. La caractérisation des fractions actives a montré que les activités étaient liées à la présence de protéines ou glycoprotéines dans les extraits. Ce résultat présente un intérêt majeur car à l’heure actuelle, a priori, aucune activité de ce type n’a été identifiée chez Ulva sp. / This PhD Thesis works, conducted in the Laboratoire de Biotechnologie et Chimie Marines of the Université de Bretagne-Sud and in the Olmix Group, was included in a national project for the upgrading of green seaweed biomasses, the Ulvans project. This project results in the collaboration of five industrial companies and two academic research laboratories. The objectives of this thesis works had been i) the characterization of the raw material, particularly the soluble matrix polysaccharides (ulvans) and proteins, ii) the development of an enzyme-assisted extraction process of algal metabolites, iii) the biochemical and molecular characterization of the enzymatic hydrolyzates, with the aim of understanding the effect of enzymes on algae thallus, iv) the screening of antioxidant and antiviral activities of hydrolyzates, v) the study of the influence of hydrolysis parameters to determine the optimum conditions for the extraction of metabolites of interest and finally vi) to conclude, according to the results provided by this study, on the viability of the industrial upscaling of the process. In conclusion of this work, enzymatic hydrolysis appeared to be an effective process for biorefinery of green seaweeds. Although commercial enzymatic preparations were not specific of algal compounds, protéases led to a significant increase in the extraction yields, whereas the effect of carbohydrases were moderate. The study of hydrolysis parameters confirmed the preliminary results and showed that the temperature, the concentration of enzyme and the grinding method had no effect on the protease used. A major result of this study has been the highlighting of anti-oxidant and anti-herpetic compounds in hydrolyzates. The antiviral activity of ulvans had several times been demonstrated but the biochemical characterization of actives fractions showed that the activity could be associated to proteins or glycoproteins. This result is very interesting because, a priori, any antiviral activity has also been related to this type of compounds in Ulva sp.

Les plages de sable sont des écosystèmes dynamiques couvrant 70% des côtes mondiales. Ces systèmes abritent un cortège spécifique unique et assurent des fonctions essentielles de nourricerie, de nurserie et d’épuration des eaux. Or à proximité des côtes, la population humaine est en développement constant ce qui accroît les multiples pressions d’origine anthropique sur les écosystèmes côtiers. L’apport en excès de nutriments constitue une menace majeure qui peut se traduire par le développement d’importantes biomasses de macroalgues opportunistes (eutrophisation). La fréquence et l’intensité de ces blooms, communément formés de chlorophycées à court cycle de vie (ulves) et appelés marées vertes (MV), s'amplifient sur les côtes françaises et dans le Monde menaçant le fonctionnement de systèmes prépondérants et uniques.La plupart des études visant à déterminer les effets des MV sur la structure et le fonctionnement d’écosystèmes sédimentaires ont été conduites dans des environnements abrités, micro- ou atidaux. Cette problématique est restée presqu’inexplorée dans des écosystèmes plus dynamiques (systèmes ouverts et macrotidaux) en raison des difficultés de mise en place d’échantillonnage et de détection des effets de stress d’origine anthropique, inhérentes à la variabilité de ces systèmes. Cette thèse a donc eu pour objectif principal de combler ce manque et produire des connaissances en étudiant les réponses in situ des communautés benthiques de plages de sable fin macrotidales en présence ou non de MV. Quatre études ont été menées à différentes échelles spatio-temporelles et en considérant différents compartiments biologiques pour répondre à cette question générale.Ce travail de thèse montre qu’à l’échelle de la région Bretagne (variabilité intégrée sur 2700km de côtes et 7 ans) les communautés benthiques d’écosystèmes dynamiques sont modifiées significativement et de manière conservative par la présence de MV. Ce travail démontre aussi que les marées vertes impactent différemment la faune benthique en fonction du type d’habitat (plages semi-exposées vs. exposées), de la profondeur (mediolittoral vs. infralittoral), et du compartiment biologique (macrofaune benthique vs. juvéniles de poissons plats). Ces comparaisons ont permis d’identifier la faune benthique de médiolittoral inférieur des plages exposées comme étant le système le plus affecté par les MV. L’étude des variations à fine échelle spatio-temporelle de ce dernier montre que les caractéristiques faunistiques (uni- et multi-variées) sont modifiées le long d’un gradient de couverture d’algues vertes. Par exemple, la β-diversité décroît significativement le long de ce gradient. Afin d’explorer les processus pouvant expliquer ces modifications, et déterminer si ces changements ont des répercussions sur le fonctionnement de l’écosystème « plage de sable », les effets de l’accumulation d’ulves sur le réseau trophique à différent(e)s niveaux/échelles ont été mesurés. Les résultats de cette étude montrent qu’une importante biomasse d’ulves induit un changement de la structure entière du réseau trophique et une modification importante du fonctionnement trophique des plages. Les expérimentations menées au cours de cette thèse montrent que les changements observés sont induits par des effets directs (consommation de débris d’ulves) et indirects (modifications d’autres sources de nourriture) de la présence des MV.Cette thèse propose un cadre de travail visant à mieux détecter les effets de stress anthropiques sur la structure et le fonctionnement d’écosystèmes dynamiques. Dans un contexte de changement global forçant les écosystèmes à faire face à de multiples stress, cette approche pourrait se révéler particulièrement utile pour démêler, comprendre et prédire les effets de perturbations induites par les activités humaines sur le fonctionnement des écosystèmes et constituer une aide à la gestion de ces environnements particuliers. / Highly dynamic systems, often considered as resilient systems, are characterised by abiotic and biotic processes under continuous and strong changes in space and time. Because of this variability, the detection of overlapping anthropogenic stress is challenging. Coastal areas harbour dynamic ecosystems in the for of open sandy beaches, which cover the vast majority of the world’s ice-free coastline. These ecosystems are currently threatened by increasing human-induced pressure, among which mass-development of opportunistic macroalgae (mainly composed of Chlorophyta, so called green tides), resulting from the eutrophication of coastal waters. The ecological impact of opportunistic macroalgal blooms (green tides, and blooms formed by other opportunistic taxa), has long been evaluated within sheltered and non-tidal ecosystems. Little is known, however, on how more dynamic ecosystems, such as open macrotidal sandy beaches, respond to such stress. This thesis assesses the effects of anthropogenic stress on the structure and the functioning of highly dynamic ecosystems using sandy beaches impacted by green tides as a study case. The thesis is based on four field studies, which analyse natural sandy sediment benthic community dynamics over several temporal (from month to multi-year) and spatial (from local to regional) scales. In this thesis, I report long-lasting responses of sandy beach benthic invertebrate communities to green tides, across thousands of kilometres and over seven years; and highlight more pronounced responses of zoobenthos living in exposed sandy beaches compared to semi-exposed sands. Within exposed sandy sediments, and across a vertical scale (from inshore to nearshore sandy habitats), I also demonstrate that the effects of the presence of algal mats on intertidal benthic invertebrate communities is more pronounced than that on subtidal benthic invertebrate assemblages, but also than on flatfish communities. Focussing on small-scale variations in the most affected faunal group (i.e. benthic invertebrates living at low shore), this thesis reveals a decrease in overall beta-diversity along a eutrophication-gradient manifested in the form of green tides, as well as the increasing importance of biological variables in explaining ecological variability of sandy beach macrobenthic assemblages along the same gradient. To illustrate the processes associated with the structural shifts observed where green tides occurred, I investigated the effects of high biomasses of opportunistic macroalgae (Ulva spp.) on the trophic structure and functioning of sandy beaches. This work reveals a progressive simplification of sandy beach food web structure and a modification of energy pathways over time, through direct and indirect effects of Ulva mats on several trophic levels. Through this thesis I demonstrate that highly dynamic systems respond differently (e.g. shift in δ13C, not in δ15N) and more subtly (e.g. no mass-mortality in benthos was found) to anthropogenic stress compared to what has been previously shown within more sheltered and non-tidal systems. Obtaining these results would not have been possible without the approach used through this work; I thus present a framework coupling field investigations with analytical approaches to describe shifts in highly variable ecosystems under human-induced stress.

The following research has focused on the utility of Ulva as an indicator of seawater nitrogen loading. Evaluation was made in three ways: 1) Observation of large-scale geographic variation in nitrogen status in natural populations around New Zealand in summer and winter, 2) Laboratory-based experimental assessment of the biochemical responses of N-indices in Ulva to nitrogen enrichment, and 3) Culturing standardized test-Ulva under low nutrient conditions which could be deployed into a variety of field situations. Seawater inorganic nutrient (nitrate, nitrite, ammonium and phosphate) concentrations and nitrogen (N)-indices (free amino acids, chlorophyll and total tissue nitrogen) in natural Ulva populations from 32 sites around New Zealand were compared. Sites were divided into 6 environmental categories: sheltered rural, exposed rural, rock pools, sheltered urban, exposed urban, and nitrogen-enriched urban sites. Seawater nutrient concentrations were highly variable between all sites in summer and winter. However, in the summer enriched urban sites had the highest mean total inorganic nitrogen concentrations and Ulva with the highest mean levels of all N-indices compared with any other environmental category. In the winter, Ulva contained more nitrogen (reflected in all N-indices) compared with Ulva in the summer, particularly in populations growing in colder southern seawater on more exposed coasts. The increase in Ulva N-status was not explained by increased seawater inorganic nitrogen concentrations. With univariate and multivariate statistical approaches it was shown that there was a significant effect of seawater temperature and site exposure on N-status in Ulva. Compared with other N-indices, stable nitrogen isotopes (δ15N) from Ulva growing in enriched urban sites had the widest range (4.77 ± 0.04 ‰ to 15.16 ± 0.03 ‰) of values compared with all other categories in both summer and winter. Conversely, Ulva from exposed rural sites had the lowest range of δ15N values compared with any other category (6.7 ± 0.1 to 8.8 ± 0.1 ‰) and showed no seasonal change in mean values (7.8 ‰ and 7.6 ‰ for summer and winter, respectively). In addition, δ15N values in Ulva were the only N-index that showed a significant difference between urban and rural categories. To test the relationship between inorganic nitrogen concentration in seawater and the responses of biochemical nitrogen indices in Ulva pertusa, several experiments were conducted in an outdoor, flow-through culture apparatus, in summer and winter. In this apparatus effects of ammonium concentration, nitrogen source (nitrate and ammonium), light and seawater motion were investigated. Of the same three N-indices examined in natural Ulva populations (free amino acids, chlorophyll and total tissue nitrogen), increases in free amino acids, particularly asparagine, provided the strongest indicator of increases in nitrogen availability. In addition, while tissue nitrogen and chlorophyll also increased with seawater nitrogen concentration, it was apparent that these indices were also strongly influenced by light, and probably season. Rates of ammonium assimilation provided no overall measure of the availability of nitrogen in seawater and were clearly affected by season. Similarly, growth rates in Ulva only showed a response to nitrogen addition in summer months. Stable isotopes of nitrogen (δ15N) in Ulva provided a clear distinction between natural and synthetic nitrogen sources, but more importantly, showed only minor fractionation (ranging from 1.3 ‰ to -1.9 ‰) of 15N supplied from synthetic nitrate and ammonium under both light-saturating and light-limiting conditions. To further develop Ulva as a standardized test-organism it was cultured in low-nutrient (non-polluted) seawater to deplete internal storage pools of nitrogen. Each month the resulting test-Ulva was then placed in surface-moored growth enclosures at a range of coastal sites around Auckland and then monitored for one year. In winter there were increases in seawater inorganic nitrogen concentrations and concomitant increases in free amino acid content. However, tissue nitrogen and chlorophyll content in test-Ulva showed similar increases (possibly saturating) across all sites suggesting that seasonal increases in these N-indices were also due to other seasonal factors (e.g., surface irradiance and / or seawater temperature). On the other hand, the total free amino acid pool showed strong differences between a low-nitrogen reference site and the other study sites all year round. It was probable that test-Ulva was integrating differences in tidally-averaged nitrogen loading that were not reliably detected in instantaneous seawater samples. In addition to N-indices in test-Ulva, levels of tissue heavy metals and stable isotopes of nitrogen showed strong differences with higher values of both typically found in urban environments compared with values found in non-polluted reference sites. It is concluded that several abiotic and biotic factors affect nitrogen status in Ulva, but the average nitrogen concentration in seawater, and the physical factors of temperature, light and water motion, appear to be the overarching determinants. It is further suggested that in combination with Ulva tissue δ15N values, tissue nitrogen and the free amino acid pool, as quantitative biochemical measures of nitrogen availability, are likely to provide useful information on both the amount and composition of nitrogen entering coastal environments. / Foundation for Research, Science and Technology. Auckland Regional Council.