abstract: Aboveground net primary production (ANPP) is an important ecosystem process that, in drylands, is most frequently limited by water availability. Water availability for plants is in part controlled by the water holding capacity of soils. Available water holding capacity (AWHC) of soils is strongly influenced by soil texture and depth. This study drew upon localized rain gauge data and four data-sets of cover-line and biomass data to estimate ANPP and to determine annual precipitation (PPT). I measured soil depth to caliche and texture by layer of 112 plots across the four landscape units for which estimation of ANPP were available. A pedotransfer function was used to estimate AWHC from soil depth increments to depth of caliche measurements and texture analysis. These data were analyzed using simple and multivariate regression to test the effect of annual precipitation and available water holding capacity on aboveground net primary production. Soil texture remained constant among all plots (sandy loam) and depth to caliche varied from 15.16 cm to 189 cm. AWHC and the interaction term (PPT*AWHC) were insignificant (p=0.142, p=0.838) and annual PPT accounted for 18.4% of the variation in ANPP. The y-intercept was significantly different for ANPP ~ annual PPT when considering AWHC values either above or below 3 cm. Shrub ANPP was insensitive to precipitation regardless of AWHC (R2=-0.012, R2=0.014). Results from this study indicate that a model incorporating annual PPT and AWHC may not serve as a good predictor for ANPP at a site level where there is little variation in soil texture. / Dissertation/Thesis / Masters Thesis Sustainability 2019

Crustaceans, the most abundant group of organisms that make up zooplankton, form a critical link in the food web between primary-producing phytoplankton and planktivorous fish. Examining this link is essential in order to effectively estimate the amount of energy available to higher trophic levels. The most appropriate currency for tracking energy flow through these food webs is to measure production, or the amount of new biomass generated over a given period of time. Although measurements of primary productivity are routinely made in oceanographic studies, estimates of secondary productivity are rare due to their historical reliance on time-consuming methods. The overall objective of this thesis was to determine the factors influencing temporal variations in community-level crustacean productivity. A simplified lab experiment was used to establish a relationship between diet and chitobiase-based estimates of copepod productivity in response to single versus mixed species phytoplankton diets. In addition, the relationships between primary productivity and chitobiase-based productivity for the entire crustacean zooplankton community were examined over two years in Saanich Inlet, British Columbia, Canada. Lastly, this work determined the abiotic and biotic factors most strongly influencing crustacean productivity in the tropical Guanabara Bay, Rio de Janeiro, Brazil, dominated by the microbial loop. Results from this work show that: (i) copepod populations fed a poor food item take longer to develop through early stages, have lower daily growth rates, and exhibit lower productivity than those fed a good quality food item; (ii) important variations in crustacean productivity are missed when biomass estimates, alone, are used to represent food available to higher trophic levels; (iii) relationships between primary productivity and crustacean productivity can vary interannually and are not necessarily controlled by bottom-up processes; (iv) substantial interannual variations in trophic transfer efficiency (TTE) occur even if average TTE is the same across years; and (v) community-level crustacean productivity in tropical regions dominated by the microbial food loop can be as high as, if not higher than, productivity measured in temperate regions. Ultimately, this work provides insight into how accurate productivity estimates can improve our understanding of zooplankton dynamics in both laboratory and field settings in marine ecosystems worldwide. / Graduate

No description available.

Diatoms play a fundamental role in marine food webs, and significantly contribute to global primary production and carbon sequestration into the deep ocean. In many offshore areas of the open ocean, iron (Fe) input is low, and its availability often limits phytoplankton biomass. Recently, gene sequences encoding ferritin, a nearly ubiquitous iron storage and detoxifying protein, have been identified in pennate diatoms such as Pseudo-nitzschia, but not in other Stramenopiles (which include centric diatoms, brown algae and some protist plant parasites) or Cryptophyte relatives. Members of this genus readily bloom upon addition of iron to Fe-limited waters, and are known to produce the neurotoxin domoic acid. Until now, the reason for the success of pennate diatoms in the open ocean was uncertain; however, expressing ferritin would allow pennate species to store Fe after a transient input, using it to dominate Fe stimulated algal blooms. Here, the ferritin gene was cloned from the coastal pennate diatom Pseudonitzschia multiseries, overexpressed in Escherichia coli, and purified using liquid chromatography. The ferritin protein sequence appears to encode a non-heme, ferritinlike di-iron carboxylate protein, while gel filtration chromatography and SDS-PAGE indicate that this ferritin is part of the 24 subunit maxi-ferritins. Spectroscopically monitoring the addition of Fe(II) to a buffered ferritin solution shows that the P. multiseries protein demonstrates ferroxidase activity, binding iron and storing it as Fe(III) in excess of 600 equivalents per protein shell. In keeping with the typical stoichiometry of the ferroxidase reaction, oxygen (O₂) is consumed in a 2 Fe:O₂ratio while hydrogen peroxide is produced concurrently. iii Diatoms evolved from secondary endosymbiosis involving eukaryotic red algae; however, a broad phylogenetic comparison suggests that P. multiseries ferritin was likely acquired via lateral gene transfer from cyanobacteria – not from its ancestral endosymbionts. Until recently, no other ferritins have been identified in diatoms, and the protein characterized here is unique in that it seems to be derived from a prokaryotic organism yet it occurs in a marine eukaryote. These findings have direct implications for the success of pennate diatoms in both Fe rich coastal waters and upon Fe addition in the open ocean.

Diatoms play a fundamental role in marine food webs, and significantly contribute to global primary production and carbon sequestration into the deep ocean. In many offshore areas of the open ocean, iron (Fe) input is low, and its availability often limits phytoplankton biomass. Recently, gene sequences encoding ferritin, a nearly ubiquitous iron storage and detoxifying protein, have been identified in pennate diatoms such as Pseudo-nitzschia, but not in other Stramenopiles (which include centric diatoms, brown algae and some protist plant parasites) or Cryptophyte relatives. Members of this genus readily bloom upon addition of iron to Fe-limited waters, and are known to produce the neurotoxin domoic acid. Until now, the reason for the success of pennate diatoms in the open ocean was uncertain; however, expressing ferritin would allow pennate species to store Fe after a transient input, using it to dominate Fe stimulated algal blooms. Here, the ferritin gene was cloned from the coastal pennate diatom Pseudonitzschia multiseries, overexpressed in Escherichia coli, and purified using liquid chromatography. The ferritin protein sequence appears to encode a non-heme, ferritinlike di-iron carboxylate protein, while gel filtration chromatography and SDS-PAGE indicate that this ferritin is part of the 24 subunit maxi-ferritins. Spectroscopically monitoring the addition of Fe(II) to a buffered ferritin solution shows that the P. multiseries protein demonstrates ferroxidase activity, binding iron and storing it as Fe(III) in excess of 600 equivalents per protein shell. In keeping with the typical stoichiometry of the ferroxidase reaction, oxygen (O₂) is consumed in a 2 Fe:O₂ratio while hydrogen peroxide is produced concurrently. iii Diatoms evolved from secondary endosymbiosis involving eukaryotic red algae; however, a broad phylogenetic comparison suggests that P. multiseries ferritin was likely acquired via lateral gene transfer from cyanobacteria – not from its ancestral endosymbionts. Until recently, no other ferritins have been identified in diatoms, and the protein characterized here is unique in that it seems to be derived from a prokaryotic organism yet it occurs in a marine eukaryote. These findings have direct implications for the success of pennate diatoms in both Fe rich coastal waters and upon Fe addition in the open ocean.

O gênero Pinus ocupa no Brasil uma área plantada de 1,59 milhão de hectares e tem uma ampla faixa de produtividade florestal (18 a 45 m3 ha-1 ano-1), em função das espécies utilizadas, das limitações edáficas, dos tipos de clima, melhoramento genético e, e alguns casos, pela ocorrência de pragas e doenças. Apesar do conhecimento de que o aumento da disponibilidade de recursos naturais (luz, água e nutrientes) eleva a produção de madeira, faz-se necessário compreender como estes recursos influenciam os processos de captura (produção primária bruta ou GPP) e alocação de carbono (C) para os diferentes compartimentos da floresta (raiz, lenho, galhos e folhas). Além disso, o grau de controle genético é de grande importância nesses processos e também deve ser analisado. Assim, este projeto objetivou quantificar as taxas de captura e alocação de carbono em uma espécie de Pinus tropical (P. caribaea var. hondurensis) e em uma subtropical (P. taeda), dos 6,5 aos 8,5 anos de idade, em parcelas controle (sem fertilização e sem irrigação) e parcelas fertilizadas e irrigadas. O experimento está localizado no município de Itatinga - SP e se utilizou o método do balanço de carbono para estimar a produtividade primária líquida da parte aérea (ANPP), o fluxo de carbono para o solo (TBCF), produtividade primária bruta (GPP) e produtividade líquida do ecossistema (NEP). Ao final do estudo, a biomassa do tronco foi 75% superior no P. caribaea var. hondurensis (126 Mg ha-1) do que no P. taeda (72 Mg ha-1), sendo que em ambas as espécies houveram ganhos significativos com a fertilização e irrigação. O primeiro ano avaliado foi mais seco do que o segundo (1195 contra 1487 mm), resultando em diferenças nos fluxos calculados. A produção de tronco do P. caribaea var. hondurensis variou de 722 a 1569 gC m-2 ano-1, enquanto do P. taeda foi de 221 a 452 gC m-2 ano-1. A espécie subtropical obteve os maiores valores de TBCF, variando de 1150 a 2197 gC m-2 ano-1, e para as duas espécies se encontrou relação do TBCF com a ANPP e GPP. Assim, encontrou-se que a maior produtividade da espécie tropical é resultado de seu maior GPP (4964 contra 3744 gC m-2 ano-1 no P. taeda), maior partição de carbono para incremento de tronco (22% contra 9% no P. taeda) e menor partição para TBCF (23% contra 45% no P. taeda). Já a fertilização e irrigação não mudaram a partição da GPP para a ANPP e TBCF comparado ao tratamento controle, e o ganho em produção de madeira foi explicado apenas pelo aumento na GPP (11%). A NEP para ambas as espécies foi positiva, mostrando que essas espécies estão atuando como drenos de carbono. Assim, o conhecimento de como a captura e alocação de C é afetada pela espécie, água e nutrição terá aplicação sobre o manejo florestal, além de propiciar valores de fluxos essenciais para a calibração de modelos ecofisiológicos de produção, ainda inexistentes para essas espécies no Brasil. / The genus Pinus in Brazil has a planted area of 1.59 million hectares and it has a wide range of forest productivity (18-45 m3 ha-1 yr-1) depending on the species, edaphic limitations, climate, breeding and, in some cases, the occurrence of pests and diseases. Despite knowing that the increased resources availability (light, water and nutrients) improves the production of wood, it is necessary to understand how these features influence the uptake processes (gross primary production or GPP) and carbon allocation (C) on the different forest compartments (root, bole, branch and leaf). Furthermore, the degree of genetic control is rather important in these processes and should also be analyzed. Thus, this project aimed to quantify carbon sequestration and allocation rates in a tropical pine (P. caribaea var. hondurensis) and a subtropical one (P. taeda), from ages 6.5 to 8.5 years old, in control plots (no fertilization and no irrigation) and fertilized and irrigated plots. The experimental site is located in Itatinga- SP and the carbon balance approach was used to estimate the above ground net primary production (ANPP), total belowground carbon flux (TBCF), gross primary production (GPP) and net ecosystem production (NEP). At the end of the study, the bole biomass was 75% higher in the P. caribaea var. hondurensis (126 Mg ha-1) than in P. taeda (72 Mg ha-1), and in both species there were substantial improvements with fertilization and irrigation. The first year evaluated was drier than the second (from 1195 to 1487 mm), resulting in differences in the calculated fluxes. The P. caribaea var. hondurensis bole production ranged from 722 to 1569 gC m-2 yr- 1, while the P. taeda showed values from 221 to 452 gC m-2 yr-1. The subtropical specie obtained the largest values of TBCF (from 1150 to 2197 gC m-2 yr-1), and on both species there was relationship between TBCF and ANPP and GPP.Thus, the higher productivity of tropical specie is a result of higher GPP (4964 versus 3744 gC m-2 yr-1 in the P. taeda), increased carbon partitioning to bole increment (22% versus 9% in the P. taeda) and smaller partitioning for TBCF (23% versus 45% in the P. taeda). Fertilization and irrigation have not changed the partitioning from GPP to ANPP and TBCF compared to the control plots, and increase in the production of wood it has been explained only by increased GPP (11%). The NEP for both species was positive, showing that these species are acting as carbon sinks. Therefore, the knowledge of how the carbon sequestration and allocation is affected by the species, water and nutrition will have application on forest management, besides providing values of essential fluxes for calibration of ecophysiological production models, still non-existent for these species in Brazil.

Esta pesquisa foi desenvolvida nas lagoas facultativas das estações de tratamento de esgoto dos municípios de Pariquera-Açu (PA) e Jacupiranga (JA), com diferentes configurações, sendo a primeira composta por lagoa anaeróbia seguida de facultativa com chicanas e a outra por lagoa aerada mecanicamente seguida de facultativa. Estas lagoas são consideradas ambientes hipereutróficos, pois apresentam grande quantidade de matéria orgânica oriunda dos esgotos domésticos e industriais. O conhecimento da estrutura da comunidade fitoplanctônica e sua avaliação em diferentes horários do fotoperíodo são relevantes pois estes organismos são responsáveis pela produção de oxigênio necessário para a degradação da matéria orgânica. Esta pesquisa teve como objetivo principal o estudo sazonal e diário da estrutura da comunidade fitoplanctônica e da produção primária nestas lagoas. Para atingir este objetivo foi caracterizada a estrutura da comunidade, em relação a biomassa e diversidade, e determinada a produção primária com incubações in situ através do método do oxigênio dissolvido. O estudo foi realizado em quatro épocas do ano (variação sazonal) no período das 7 às 16 horas, com amostragens de 3 em 3 horas (diária). Não foram observadas variações temporais e espaciais na estrutura da comunidade fitoplanctônica nas duas lagoas facultativas. Apenas as cianobactérias (principalmente a Synechocystis aquatilis e Phormidium sp) e clorofíceas (Kirchneriella lunaris, Chlorella Kessleri, Monoraphidium contortum, Monoraphidium sp, Chlamydomonas sp, Eutetramorus planctonicus e Micractinium pusillum) foram predominantes, nestas lagoas, porém em períodos alternados. Foram observados altos valores de produção primária bruta (15.891 mg\'O IND.2\'/\'M POT.3\'.h em PA; 5.700 mg\'O IND.2\'/\'M POT.3\'.h em JA) na interface água-sedimento das duas lagoas devido, provavelmente, ao padrão de mistura da coluna de água. Foram também observados altos valores de respiração da comunidade (abril, julho e setembro), devido à alta concentração de matéria orgânica presente nestes sistemas e, portanto, maior decomposição, indicando predominância de processos heterotróficos. / This research was developed in facultative ponds of the waste water treatment plant of Pariquera-Açu and Jacupiranga cities with different configurations, being the first composed by anaerobic pond followed by facultative with chicanas and the another composed by aerated mechanic pond followed by facultative. These ponds are considered hypereutrophic environments because it shows a large quantity of organic matter derived from the domestic and industrial sewage. The knowledge of phytoplanktonic community structure and its evaluation in different times of photoperiod are relevant since such organisms was responsible by production of oxygen necessary to the degrade of organic matter. This research had the main goal the seasonal and daily study of the phytoplanktonic community and the primary production in these ponds. To reach this objective the structure of the community was characterized in relation to biomass and density, and determined the primary production with incubations in situ through the dissolved oxygen method. The study was made in four periods of the year (seasonal variation) between the 7 a.m. to 4 p.m., with samplings of 3-to-3 hours (daily). It was not observed temporal and spatial variations in the phytoplanktonic community structure in the facultative ponds. Only cyanobacteria (mainly Synechocystis aquatilis and Phormidium sp) and chlorophycea (Kirchneriella lunaris, Chlorella Kessleri, Monoraphidium contortum, Monoraphidium sp, Chlamydomonas sp, Eutetramorus planctonicus and Micractinium pusillum) were predominant in these ponds, however, in alternated periods. It was observed high rates of gross primary production (15891 mg\'O IND.2\'/\'M POT.3\'.h, PA; 5700 mg\'O IND.2\'/\'M POT.3\'.h, JA) in the interface water-sediment of both ponds due, probably, to the standard of mixed conditions of water column. It was also observed high rates of community respiration (April, July and September), due to the high concentration of organic matter present in these systems and, therefore, greater decomposition, indicating predominance of heterotrophic processes.

Este trabalho é parte de um projeto mais amplo intitulado \" Tipologia de Reservatórios do Estado de São Paulo\", financiado pela FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo) que compreendeu o estúdo de 52 reservatórios. Neste estudo, quatro amostragens foram realizadas em dez reservatórios, durante o ano de 1979. Sete destes ambientes pertencem à Bacia do Tietê: Americana, Atibainha, Cabuçú, Cachoeira, Pedro Beicht, Ribeirão do Campo e Taiaçupeba; e três à bacia do Rio Paraíba do Sul: Jaguari, Paraibuna e Santa Branca. Em cada reservatório, foi estabelecida uma estação de coleta, exceto em Paraibuna, onde foram estabelecidas três estações. A produção primária medida pelo método do 14C, foi determinada de forma a se obter um perfil vertical na zona eufótica, assim como as concentrações de clorofila-a . Os dados físico-químicos sobre penetração de luz, temperatura, condutividade, oxigênio dissolvido, pH, alcainidade, formas de CO2, nutrientes e íons em solução foram obtidos ao longo da coluna de água, principalmente na região da zona eufótica. Os resultados obtidos permitiram a identificação de dois padrões de circulação: monomíctico quente e polimíctico. As medidas de produção primaria mostraram que, de modo geral, os reservatórios são pouco ou medianamente produtivos, (41,4 a 285,8 mgC.m-2 .dia-1 ) o que decorre do fato de estarem situados em terrenos pobres, na parte alta das bacias de drenagem. Isto se reflete nos baixos valores de condutividade, alcalinidade e na pobreza especialmente de fosfatos. Em alguns destes reservatórios, também a extensão da zona eufôtica, diminuindo a produtividade. O Reservatório de Americana foi uma exceção por tratar-se de um ambiente que vem sofrendo eutrofização cultural. Em conseqüência, sua produtividade média atingiu 768,2 mgC. m-2 dia-1 . Os valores de eficiência fotossintética observados foram baixos, (0,003 a 0,308%) semelhantes à grande maioria dos ambientes aquáticos. O nanoplâncton foi o principal responsável pela produção primária, o que provavelmente decorre da maior relação superfície/volume apresentada por estes organismos e que permite a melhor exploração de ambientes oligotróficos. Aparentemente, o fósforo é o principal nutriente limitante na maioria dos ambientes, como sugerida pelas baixas concentrações de fosfato dissolvido e pelas razões extremamente altas de N:P obtidas em diversos reservatórios, particularmente no inverno. / The present work is part of a 1argeT project entited \"Typo1ogy of Reservoirs of the State of São Paulo\". It was sponsored by FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo - State Foundation for Research Support), and included the study of 52 reservoirs. For the present study, ten reservois were sampled four times during 1979. Seven of these belong to the Tietê River basin: Americana, Atibainha, Cabuçu, Cachoeira, Pedro Beicht, Ribeirão do Campo and Taiaçupeba; and three to the Paraíba do Sul River basin: Jaguari, Paraibuna and Santa Branca. One samp1ing station was selected for each reservoir except Paraibuna, where three stations were chosen. Primary production, measured by the 14C method, as wel1 as concentrations of ch1orophyll-a were determined in selected depths in order to provide a vertical profile of these variables in the euphotic zone. Physico-chemica1 data such as ligth penetration, temperature, electric conductivity, dissolved oxygen, pH, alkalinity, forms of C02, nutrients and ions in solution were obtained along the water column, especially in the euphotic zone. The resu1ts permitted the detection of two circulation patterns: warm monomictic and po1ymictic. In a general way, primary production levels were from low to medium (41.4 to 285.8 mg C.m-2 .day-1), a consequence of most the reservoirs being located in the upper parts of their drainage basins, characterized by poor soils. This is reflected in low va1ues of conductivity, alkalinity and, among the nutrients, of phosphates. On the other hand, in some of the reservoirs low ligth penetration values reduced the thickeness of the euphotic zone, also lawering productivity. Americana Reservoir, suffering a process of cultural eutrophication, was an exception, its productivity averaging 768.2 mg C.m-2 . day-1 . Observed vaIues of photosynthetic efficiency were low (0.003 to 0.308 per cent) , as in the great majority of aquatic environments. The nanoplankton were responsible for most of the primary production, probably due to their higher surface volume ratios, allowing them to exploít more easily oligotrophic environments. Apparently phosphorus is the chief limiting nutrient in most reservoírs, as suggested by the low values of dissolved phosphates and by the very high N:P ratios observed in several of the reservoirs, particularly in winter.

En milieu intertidal rocheux, les communautés dominées par des canopées d'algues brunes (Phaeophyceae) sont particulièrement répandues. Malgré leur accessibilité, leur fonctionnement reste encore largement méconnu. En particulier, l'influence de la saisonnalité et du gradient d'émersion sur le métabolisme, le réseau trophique ou encore le processus de succession a été peu étudiée. Ce travail de thèse a donc eu pour objectif d'analyser le fonctionnement de deux communautés de Fucus établies à des niveaux marégraphiques différents, en portant une attention particulière aux conditions environnementales. Sur les côtes bretonnes (France), les communautés de Fucus vesiculosus Linnaeus et de Fucus serratus Linnaeus sont respectivement caractéristiques des étages médiolittoral moyen et inférieur. Des mesures de métabolisme (production primaire et respiration) réalisées in situ à différentes périodes de l'année ont mis en évidence une forte influence de la saisonnalité et le rôle primordial de la canopée dans les flux de carbone. Le métabolisme s'est avéré être plus élevé à l'émersion qu'à l'immersion, où l'intensité lumineuse constitue régulièrement un facteur limitant pour la production primaire. Par une approche de modélisation basée sur ces mesures et sur des données environnementales acquises à haute fréquence, un bilan annuel de production primaire a été calculé pour chaque communauté. Ces bilans confirment que ces systèmes sont fortement productifs et permettent de préciser leur régulation à l'échelle des cycles de marées. Le réseau trophique de ces communautés, analysé via les isotopes stables du carbone et de l'azote, apparait basé sur l'utilisation de nombreuses sources. / Along intertidal rocky shores, communities dominated by canopy-forming brown algae (Phaeophyceae) are particularly widespread. Their functioning is however largely understudied, especially concerning the influence of seasonality and shore height on primary production and respiration, on food webs or on successional process. The aim of this study was to investigate the functioning of two intertidal Fucus communities which are established at different tidal levels. During this study, a special consideration was given to the effects of environmental conditions. On the coasts of Brittany (France), communities dominated by Fucus vesiculosus Linnaeus and Fucus serratus Linnaeus are characteristic of mid-intertidal and low mid-intertidal levels, respectively. In situ measurements of metabolism (primary production and respiration) carried out at different periods of a year highlighted a strong seasonal influence on carbon fluxes and emphasized the importance of canopies in the metabolism of whole communities. Metabolism was higher during emersion than during immersion periods, for which light intensity regularly limits the primary production. Based on these measurements and on high-frequency measurements of environmental parameters, an annual primary production was calculated by modelling for both communities. These annual estimations confirmed that these communities are among the most productive systems of coastal region and specify their regulation at the tidal cycles scale. Food webs, which were analysed through carbon and nitrogen stable isotopes, are based on the use of almost all available sources of organic matter by consumers, and revealed a strong conservation of food webs across seasons. Thecolonisation survey of bare substrates shows that Fucus species improve the settlement success of numerous species and increase rapidly primary production of whole assemblages. Overall, despite some differences in metabolism and successional sequences according to the shore height at whichthey are located, these communities exhibited similar functioning due to the canopy which damns the environmental conditions.

Diatoms play a fundamental role in marine food webs, and significantly contribute to global primary production and carbon sequestration into the deep ocean. In many offshore areas of the open ocean, iron (Fe) input is low, and its availability often limits phytoplankton biomass. Recently, gene sequences encoding ferritin, a nearly ubiquitous iron storage and detoxifying protein, have been identified in pennate diatoms such as Pseudo-nitzschia, but not in other Stramenopiles (which include centric diatoms, brown algae and some protist plant parasites) or Cryptophyte relatives. Members of this genus readily bloom upon addition of iron to Fe-limited waters, and are known to produce the neurotoxin domoic acid. Until now, the reason for the success of pennate diatoms in the open ocean was uncertain; however, expressing ferritin would allow pennate species to store Fe after a transient input, using it to dominate Fe stimulated algal blooms. Here, the ferritin gene was cloned from the coastal pennate diatom Pseudonitzschia multiseries, overexpressed in Escherichia coli, and purified using liquid chromatography. The ferritin protein sequence appears to encode a non-heme, ferritinlike di-iron carboxylate protein, while gel filtration chromatography and SDS-PAGE indicate that this ferritin is part of the 24 subunit maxi-ferritins. Spectroscopically monitoring the addition of Fe(II) to a buffered ferritin solution shows that the P. multiseries protein demonstrates ferroxidase activity, binding iron and storing it as Fe(III) in excess of 600 equivalents per protein shell. In keeping with the typical stoichiometry of the ferroxidase reaction, oxygen (O₂) is consumed in a 2 Fe:O₂ratio while hydrogen peroxide is produced concurrently. iii Diatoms evolved from secondary endosymbiosis involving eukaryotic red algae; however, a broad phylogenetic comparison suggests that P. multiseries ferritin was likely acquired via lateral gene transfer from cyanobacteria – not from its ancestral endosymbionts. Until recently, no other ferritins have been identified in diatoms, and the protein characterized here is unique in that it seems to be derived from a prokaryotic organism yet it occurs in a marine eukaryote. These findings have direct implications for the success of pennate diatoms in both Fe rich coastal waters and upon Fe addition in the open ocean. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate