A dinâmica da matéria orgânica particulada (MOP) nos oceanos, desde sua formação até seu consumo/exportação, é um elo importante no ciclo biogeoquímico do carbono e elementos associados, que ganhou importância nas últimas décadas devido ao aumento do CO2 antropogênico. Para melhorar os modelos e as previsões climáticas, projetos oceanográficos investigam os fatores que influenciam na dinâmica da MOP, sobretudo em regiões produtivas e representativas em escala global. No Atlântico Sul, a região mais produtiva é ao largo do continente africano, devido à contínua ressurgência de borda leste. Entretanto, regiões hidrograficamente dinâmicas também podem contribuir com elevadas taxas de produção dependendo das condições ambientais, cuja importância no reservatório de MOP ainda é desconhecida. Este trabalho tem como objetivo estudar a dinâmica do MOP em suspensão em duas regiões também produtivas do Atlântico Sudoeste: (i) o setor externo da Margem Continental Sudeste Brasileira (Capítulo 1); e (ii) o setor Austral ao sul de 30ºS (Capítulo 2). São discutidos os efeitos das condições oceanográficas no reservatório de MOP e seus padrões interanuais de distribuição geográfica. / The dynamics of particulate organic matter (POM) in the oceans, from its formation to its consumption/export, is an important link in the biogeochemical cycle of carbon and associated elements, which gained importance in the last decades due to increase of anthropogenic CO2. To improve models and climate predictions, oceanographic projects investigate the factors that influence the POM dynamics, especially in productive and representative regions on a global scale. In the South Atlantic, the most productive region is off the African continent, due to permanent Eastern Boundary upwelling. However, dynamic hydrographic regions can also provide with high production rates depending on environmental conditions, whose importance in the POM reservoir is still unknown. This work aims to study the suspended POM dynamics in two productive regions of the southwest Atlantic: (i) the outer Brazilian Southeast Continental Margin (Chapter 1); and (ii) the Austral sector south of 30ºS(Chapter 2). The effects of different oceanographic conditions in the POM reservoir, their interannual pattern and geographic distribution are discussed.

The objective of this dissertation is to gain a better understanding of the environmental and climatic effects on the temporal and spatial variability of phytoplankton biomass along the West Florida Shelf. Chapter 1 examines temporal and spatial patterns in chlorophyll concentrations using satellite data collected between 1997 and 2003. Chlorophyll data derived from the SeaWiFS sensor are validated with in-situ data and analyzed. Wind, current, sea surface temperature, river, and rain data are used to better understand the factors responsible for the patterns observed in the satellite data. My question is whether the standard OC4 algorithm is adequate for studying short-term variability of chlorophyll concentrations along the WFS. I will examine temporal and spatial trends using the OC4 and compare them to the Carder semianalytical algorithm which uses remote sensing reflectances at 412nm, 443nm, 490nm,and 555nm to estimate chlorophyll concentrations separately from CDOM estimates. In Chapters 2 and 3 the potential problems due to CDOM and bottom reflectance are examined. In Chapter 2 I analyze the influence of riverine induced CDOM. Water leaving radiances are analyzed in an effort to discriminate true chlorophyll patterns from CDOM contaminated signals. Chapter 3 examines the impact of bottom reflectance on the satellite signal by using the percentage of remote sensing reflectance at a wavelength of 555 to differentiate between optically shallow waters and optically deep waters. Optically shallow waters are defined as those with the percentage of Rrs at 555 due to bottom reflectance greater than or equal to 25 percent, while optically deep waters have percent bottom reflectance less than or equal to 25 percent. These analyses will help assess the validity of the temporal and spatial patterns ofchlorophyll concentration observed with the SeaWiFS data described in Chapter 1.

Nutritional factors with antioxidant properties, such as those contained in edible algae or green plants, might be implicated in protection against cancer development. Chlorophyll and other tetrapyrrolic compounds, structurally related to heme and antioxidant bile pigment bilirubin, belong to important candidate molecules, which might be responsible for these effects. Based on our studies demonstrating antiproliferative effects of S. platensis edible alga extract on experimental model of human pancreatic adenocarcinoma we investigated in detail the effect of chlorophyll occurring abundantly in this alga. Since only scarce data exist on the antiproliferative effects of chlorophylls, the aim of our study was to assess these effects. The study was performed on experimental models of human pancreatic and prostate cancer. The inhibitory effects of chlorophylls (chlorophyll a, chlorophyll b, chlorophyllin and pheophytin a) on cell proliferation and cell viability were investigated in in vitro studies. Chlorophylls reduced the mRNA expression as well as activity of hemeoxygenase in tested pancreatic cancer cells. Simultaneously, chlorophylls played an important role in redox environment of studied cancer cell lines including modulation of mitochondrial membrane potential, reactive oxygen species (ROS)...

This work monitors the response of plants to water deficit and subsequent restoration of water availability with the aim to expand our knowledge about plant behaviour during and after drought stress from the perspective of two plant species with a different type of photosynthesis. A particular attention was paid to the intraspecific differences and their possible changes during stress and post-stress periods. The plant response was monitored as the changes of selected photosynthetic, morphological and developmental characteristics caused by the cessation of watering for six days followed by a six-day period of renewed optimal water supply. The experiments were carried out on plants with different types of photosynthesis - C3 plant Vicia faba L and C4 plant Zea mays L.; for both plant species, three varieties / genotypes were monitored. The response of both plant species to insufficient water supply differed by the extent of changes in relative water content (RWC), chlorophyll fluorescence parameters, the dry mass of individual leaves (developed during the stress period), the ratio between the aboveground dry mass and dry mass of roots. In drought-stressed plants, downward trend in RWC was observed, as well as the increase of the minimum yield of chlorophyll fluorescence in dark-adapted leaves (F ),...

Freshwater resources and supplies in South Africa are experiencing severe stress from rising population growth, drought and high urbanization. The stress factors have also exerted pressure on wastewater treatment works leading to the release of partially treated effluent. The study assessed and compared the impact of the two wastewater treatment works effluent discharged into the Roodeplaat Dam. Selected physical parameters (pH, conductivity), chemical parameters (total oxidised nitrogen, phosphate, chemical oxygen demand, chloride, sulphate, sodium) and microbiological parameter (Escherichia coli) were evaluated and compared with South African standards. Secondary data (from January 2012 to December 2017) was used to identify parameters that were above or below regulatory standards. The t-test (p < 0.05) was used to compare changes between 2012 and 2018 over the same months.The results indicated that aquatic ecosystem quality has not improved, degradation continues as well as a lack of intervention from authorities. The leading parameters in causing stress to Roodeplaat water quality in descending order were Escherichia coli (E. coli), Phosphate (PO43-), Total Oxidized Nitrogen (TON), Chemical Oxygen Demand (COD), Chlorophyll a (Chl a), Ammonia (NH3), Electrical Conductivity (EC) and Sodium (Na). One of the main reasons why poor effluent was released is limited financial investment to upgrade the treatment facilities. This research provided highlights on the need to enforce extra measures to guarantee compliance of treated effluent quality to the existing guidelines. Moreover it highlights the need for concerned department’s authorities to invest in water by allocating enough budget to address the challenge of wastewater treatment works upgrades. / Environmental Sciences / M. Sc. (Environmental Sciences)

Die pflanzliche Light-harvesting complex-Proteinfamilie besteht aus Proteinen mit vielfältigen Funktionen. Dabei ist die Funktion der Light-harvesting-like 3-Proteine (LIL3) sowie der One-helix-Proteine (OHPs) weitestgehend unbekannt. Im Rahmen dieser Arbeit wurde gezeigt, dass LIL3 nicht nur mit der Geranylgeranyl-Reduktase (CHLP), sondern auch mit der Protochlorophyllid-Oxidoreduktase (POR) interagiert. Sowohl CHLP als auch POR werden über die Interaktion zu LIL3 an die Thylakoidmembran gebunden und dadurch stabilisiert. Beide Enzyme liefern die direkten Vorstufen für den von der Chlorophyll-Synthase (CHLG) katalysierten finalen Chlorophyll-Syntheseschritt. Neben der Bestätigung der bereits früher gezeigten Chlorophyllbindung von LIL3 konnte eine Affinität zu den späten Intermediaten der Chlorophyllbiosynthese Proto IX, MgP, MgPMME und Pchlid nachgewiesen werden. Die größte Affinität bestand dabei gegenüber dem Substrat von POR, Pchlid. Basierend auf diesen Erkenntnissen wird LIL3 als Regulator der späten Chlorophyllbiosynthese-Schritte vorgeschlagen: LIL3 transportiert Substrate zwischen den Enzymen und ermöglicht durch die Bindung von CHLP und POR die Synthese der Chlorophyll-Edukte in räumlicher Nähe. Dadurch wird die Versorgung von CHLG mit dessen Edukten favorisiert. Beide OHP-Varianten (OHP1/2) bilden ausschließlich Heterodimere und binden Chlorophyll sowie Carotinoide im Verhältnis 3:1. Die Pigmentbindung basiert auf den konservierten Aminosäuren im Chlorophyllbindemotiv. An das OHP1-OHP2-Dimer bindet der PSII-Assemblierungsfaktor HCF244 und wird dadurch an der Membran verankert. HCF244 stabilisiert das OHP-Heterodimer und beide OHPs stabilisieren sich gegenseitig. Der heterotrimere OHP1-OHP2-HCF244-Komplex ist für die D1-Synthese wesentlich. Es wird vermutet, dass die OHPs an der co-translationalen Beladung von (p)D1 mit Pigmenten beteiligt sind sowie frühe Assemblierungsintermediate von PSII vor überschüssiger Anregungsenergie schützen. / The plant light-harvesting complex protein family comprises different members with a variety of functions. However, the function of the light-harvesting-like 3 proteins (LIL3) as well as the one-helix proteins (OHPs) is largely unknown. In this thesis, an interaction of LIL3 not only with geranylgeranyl-reductase (CHLP), but also with protochlorophyllide-oxidoreductase (POR) could be established. LIL3 tethers CHLP and POR to the thylakoid membrane, thereby conferring stability to both enzymes. Both CHLP and POR are synthesizing the direct chlorophyll precursors which are combined to chlorophyll by the subsequent chlorophyll synthase (CHLG). In addition to the chlorophyll binding ability of LIL3 reported earlier, an affinity of LIL3 towards the chlorophyll biosynthesis intermediates Proto IX, MgP, MgPMME, and Pchlide could be shown. Interestingly, the highest affinity of LIL3 was exerted towards Pchlide which is the substrate of POR. Therefore, LIL3 is postulated to shuffle the intermediates between enzymes and brings CHLP and POR in close proximity, which may help to supply CHLG with its substrates. Regarding the function of the OHPs an exclusive heterodimer formation of both the OHP1 and OHP2 variants could be shown. The OHP1-OHP2-heterodimer is able to bind chlorophyll and carotenoids in an approximate 3:1 ratio and pigment binding depends on dimer formation as well as the presence of the conserved amino acids in the chlorophyll binding motif. The PSII-assembly factor HCF244 is anchored to the thylakoid membrane by binding to both OHPs, thereby stabilizing the OHP-heterodimer. The heterotrimeric OHP1-OHP2-HCF244-complex is essential for D1 biosynthesis, although the exact molecular function of HCF244 is still unknown. It is suggested that the OHP-dimer is responsible for co-translational loading of (p)D1 with pigments as well as photoprotection of early PSII assembly intermediates.

Die Tetrapyrrol-Biosynthese der Pflanzen ist ein hoch konservierter Prozess, indem sich die Häm- und Chlorophyllsynthese gemeinsame Syntheseschritte von der 5-Aminolävulinsäure (ALA)- bis hin zur Protoporphyrin IX (Proto)-Bildung teilen. Zur Hämsynthese sind in Arabidopsis thaliana zwei Isoformen der Ferrochelatase (FC) vorhanden, welche die Insertion von Eisenionen in Proto katalysieren. In dieser Arbeit wurden fc1 und fc2 Mutanten analysiert und für Komplementationsversuche mit nativen und modifizierten FC1/FC2-Sequenzen genutzt. Die in der fc1-2 Mutante gestörte Embryonalentwicklung infolge des FC1 Mangels konnte durch Expression eines pFC1::FC1 Genkonstruktes komplementiert werden. Die Expression von FC2 unter dem FC1 Promoter (pFC1::FC2) konnte die fc1-2 Mutante unter Standard-Wachstumsbedingungen vollständig komplementieren, jedoch nicht unter Salzstress. Zusätzlich zu den Komplementationsversuchen der fc1 Mutanten wurde auch eine fc2 Null-Mutante zur Expression der beiden genomischen FC Sequenzen herangezogen, um die spezifischen Funktionen der FC2-Varianten zu untersuchen. Während die pFC1FC2 (fc2/fc2) Pflanzen unter Dauerlicht eine vollständige Komplementation zeigten, konnte unter Kurztagbedingungen nur eine partielle Komplementation beobachtet werden. Versuche geben erste wichtige Hinweise, dass auch FC2 an der Regulation der ALA-Synthese infolge ihrer Interaktion mit PORB beteiligt ist. Dies deutet darauf hin, dass der Häm- und der Chlorophyllzweig eine gemeinsame Regulation der ALA-Synthese teilen, um das Gleichgewicht der TBS zu wahren. Neben der Funktion der FC2 in der Regulation der TBS konnte die vorliegende Arbeit ebenfalls die Rolle der FC2 in der Assemblierung der PSII-LHCII Superkomplexe offenlegen. Basierend auf den Ergebnissen, dieser Studie können Modelle für die funktionale Verteilung der beiden FC-Isoformen in unterschiedlichen Geweben und Entwicklungsstadien, sowie die Funktionen in verschiedenen biologischen Prozessen postuliert werden. / In plants, heme and chlorophyll synthesis share the common synthetic steps from 5- aminolevulinic acid (ALA) formation to Protoporphyrin IX (Proto) production in the conserved Tetrapyrrole biosynthesis (TBS) pathway. Arabidopsis thaliana utilizes two ferrochelatses (FC) to catalyse the insertion of ferrous iron into Proto to yield heme. In this study, the fc1 and fc2 defective mutants have been re-analysed and used for complementation tests with expression of a native or modified FC1/FC2 sequence. The pFC1FC1 (fc1/fc1) complementation plants confirmed that the defective embryo maturation in homozygous fc1-2 seeds is attributed to a lack of FC1. Expression of FC2 under the FC1 promoter contributed to a full complementation of fc1-2 under standard growth conditions, but not under salt stress. A fc2 null mutant has been used to express the two FC genomic sequences to substantiate the specific functions of FC2. Expression of FC2 under its own promoter was able to rescue fc2-2 mutants under both SD and CL conditions. However, pFC2FC1 (fc2/fc2) plants showed a partial complementation under SD condition. Via multiple interaction assays and mutant analyses, this thesis uncovered a mechanism of FC2 action on ALA synthesis regulation via interaction of FC2 and PORB. The results indicate that both branches of heme and chlorophyll synthesis share a common regulation to balance the TBS pathway. Apart from a role of FC2 involved in the regulation of TBS pathway, the presented study also revealed FC2 function in the assembly of the PSII-LHCII supercomplexes. Based on all the results obtained in this study, the functional distribution models of the two FC in different tissues and development stages, as well as diverse biological processes, have been proposed. In addition, to which extent that FC1/FC2 could compensate the function of the other isoform has been discussed.

Gold mine tailings material facilities are characterized by sparse vegetation and an abundance of dust. Mine tailings facilities are examples of extreme geotechnical and geochemical conditions which make it almost impossible for higher plants to establish and grow without rehabilitation intervention. In most cases higher plants such as grasses and trees are the focus areas for rehabilitation, but, having a look at something a little smaller such as biological crusts, it is seen that these micro-organisms play very important roles in any ecosystem. Various studies have shown that biological crusts, consisting of micro-organisms such as lichens, algae and cyanoprokaryotes enhance the soil quality by binding soil particles together, forming aggregates which counteract the erosive forces of wind and water. They play a part in nitrogen and carbon fixation, increase the soil surface temperature and increase the water retention of the soil. Thus, these organisms improve the overall health of the soil, which will in time encourage the successful establishment of higher plants. The aim of this study was to investigate the presence of cyanoprokaryotes and soil algae on mine tailings storage facilities that have been rehabilitated for different periods of time as well as to correlate the presence of these species with the physical and chemical characteristics of the mine tailings material. Chemical, physical and biological analyses of soil samples were done. Some of the ecologically important and dominant species were isolated and protocols were developed in order to identify the most successful manner in which to re-inoculate the organisms to a chosen substrate and how to measure biomass. Due to the immense cost of standard rehabilitation practices there is a need for a more cost effective, sustainable manner in which to protect the tailings material against the erosive forces of wind and water with as little input as possible. The influence of an organism cultured in normal Bold’s Basal medium (BBM) growth medium, BBM growth medium with half the phosphate concentration and BBM growth medium with half the nitrate concentration on the establishment of a biological soil crust (BSC) was tested. To test the influence of the inoculums already present in the tailings material and in the air, trials with mulch, water and nutrients without the addition of an organism was also investigated. This was done in the controlled environment of a glasshouse, as well as in field conditions. The biomass of the cyanoprokaryotes and algae, as well as the soil surface strength was also tested. The results show that the time of rehabilitation did not have an influence on the cyanoprokaryotes as well as algal species that occurred on the tailings material. Chlorella sp., Chlorococcum sp. and Klebsormidium sp. were present on all six sites, except on the fresh material and 15 year old material where no rehabilitation has been done. As for dominance; Chlamydomonas sp., Chlorococcum sp., Klebsormidium sp. and Phormidium sp. were dominant on all six sites except for the fresh material, where nothing grew. An array of methods exists for measuring algal biomass as a measure of growth. During the development of protocols for further use in investigating the growth of algae, the extraction solvent ethanol, for use in chlorophyll a extraction, was identified as the most sufficient. The re-inoculation of cyanoprokaryotes and soil algae onto a chosen substrate is most successful when pouring the organisms, cultured in growth medium and 0.1% agar, over the substrate. During the glasshouse trials the influence of the growth medium and growth medium with half the nitrate and half the phosphate concentrations showed that Chlamydomonas sp. produced the highest biomass when cultured in BBM. With Nostoc sp. the highest biomass occurred with culturing in BBM and BBM with half the phosphate concentration. Microcoleus vaginatus showed no significant difference when cultured in the three different growth mediums (BBM, BBM with half the nitrate concentration and BBM with half the phosphate concentration). Overall Nostoc sp. produced the highest biomass (34.33 μg/g), followed by Microcoleus vaginatus (17.05 μg/g) and Chlamydomonas sp. (6.12 μg/g). Soil surface strength, measured with a hand held penetrometer showed that Chlamydomonas sp. cultured in BBM growth medium produced the most stable crust (2.58 kg/cm2), although it had the lowest biomass measurements (6.12 μg/g). Nostoc sp. produced the highest biomass (34.44 μg/g), but had the lowest soil surface strength results (1.75 kg/cm2). Microcoleus vaginatus proved to be the species with high biomass production (17.05 μg/g), as well as high soil surface strength (2.08 kg/cm2). M. vaginatus is also a pioneer species and is therefore a good choice as primary inoculum on bare tailings material. It was decided to use Nostoc sp. in the field trials due to its high biomass and Microcoleus vaginatus due to the high soil surface strength produced. Despite the occurrence of a severe thunder storm on the afternoon of application and poor water management during the field trials the significance of water on the establishment of soil algae and cyanoprokaryotes on tailings material was determined. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014

Gold mine tailings material facilities are characterized by sparse vegetation and an abundance of dust. Mine tailings facilities are examples of extreme geotechnical and geochemical conditions which make it almost impossible for higher plants to establish and grow without rehabilitation intervention. In most cases higher plants such as grasses and trees are the focus areas for rehabilitation, but, having a look at something a little smaller such as biological crusts, it is seen that these micro-organisms play very important roles in any ecosystem. Various studies have shown that biological crusts, consisting of micro-organisms such as lichens, algae and cyanoprokaryotes enhance the soil quality by binding soil particles together, forming aggregates which counteract the erosive forces of wind and water. They play a part in nitrogen and carbon fixation, increase the soil surface temperature and increase the water retention of the soil. Thus, these organisms improve the overall health of the soil, which will in time encourage the successful establishment of higher plants. The aim of this study was to investigate the presence of cyanoprokaryotes and soil algae on mine tailings storage facilities that have been rehabilitated for different periods of time as well as to correlate the presence of these species with the physical and chemical characteristics of the mine tailings material. Chemical, physical and biological analyses of soil samples were done. Some of the ecologically important and dominant species were isolated and protocols were developed in order to identify the most successful manner in which to re-inoculate the organisms to a chosen substrate and how to measure biomass. Due to the immense cost of standard rehabilitation practices there is a need for a more cost effective, sustainable manner in which to protect the tailings material against the erosive forces of wind and water with as little input as possible. The influence of an organism cultured in normal Bold’s Basal medium (BBM) growth medium, BBM growth medium with half the phosphate concentration and BBM growth medium with half the nitrate concentration on the establishment of a biological soil crust (BSC) was tested. To test the influence of the inoculums already present in the tailings material and in the air, trials with mulch, water and nutrients without the addition of an organism was also investigated. This was done in the controlled environment of a glasshouse, as well as in field conditions. The biomass of the cyanoprokaryotes and algae, as well as the soil surface strength was also tested. The results show that the time of rehabilitation did not have an influence on the cyanoprokaryotes as well as algal species that occurred on the tailings material. Chlorella sp., Chlorococcum sp. and Klebsormidium sp. were present on all six sites, except on the fresh material and 15 year old material where no rehabilitation has been done. As for dominance; Chlamydomonas sp., Chlorococcum sp., Klebsormidium sp. and Phormidium sp. were dominant on all six sites except for the fresh material, where nothing grew. An array of methods exists for measuring algal biomass as a measure of growth. During the development of protocols for further use in investigating the growth of algae, the extraction solvent ethanol, for use in chlorophyll a extraction, was identified as the most sufficient. The re-inoculation of cyanoprokaryotes and soil algae onto a chosen substrate is most successful when pouring the organisms, cultured in growth medium and 0.1% agar, over the substrate. During the glasshouse trials the influence of the growth medium and growth medium with half the nitrate and half the phosphate concentrations showed that Chlamydomonas sp. produced the highest biomass when cultured in BBM. With Nostoc sp. the highest biomass occurred with culturing in BBM and BBM with half the phosphate concentration. Microcoleus vaginatus showed no significant difference when cultured in the three different growth mediums (BBM, BBM with half the nitrate concentration and BBM with half the phosphate concentration). Overall Nostoc sp. produced the highest biomass (34.33 μg/g), followed by Microcoleus vaginatus (17.05 μg/g) and Chlamydomonas sp. (6.12 μg/g). Soil surface strength, measured with a hand held penetrometer showed that Chlamydomonas sp. cultured in BBM growth medium produced the most stable crust (2.58 kg/cm2), although it had the lowest biomass measurements (6.12 μg/g). Nostoc sp. produced the highest biomass (34.44 μg/g), but had the lowest soil surface strength results (1.75 kg/cm2). Microcoleus vaginatus proved to be the species with high biomass production (17.05 μg/g), as well as high soil surface strength (2.08 kg/cm2). M. vaginatus is also a pioneer species and is therefore a good choice as primary inoculum on bare tailings material. It was decided to use Nostoc sp. in the field trials due to its high biomass and Microcoleus vaginatus due to the high soil surface strength produced. Despite the occurrence of a severe thunder storm on the afternoon of application and poor water management during the field trials the significance of water on the establishment of soil algae and cyanoprokaryotes on tailings material was determined. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014

As land use transformations are the main driver of biological diversity loss at the global scale, it is essential to provide predictions and understanding of their impacts in order to improve the mitigation of ecosystem perturbations. The first objective of this project was to describe the response of biological assemblages along a gradient of urbanization and to compare metrics of watershed imperviousness in order to determine, as has been suggested in the literature, whether effective imperviousness, which represents the proportion of impervious area directly connected to the stream by storm sewers, is a better predictor of stream impairement than total imperviousness in the watershed. Decline in sensitive taxa abundance is initiated at 14% total imperviousness and 3% effective imperviousness in the Ottawa-Carleton region and, total and effective imperviousness have equivalent predictive power. The second objective of this project was to describe how the structure of metazoan assemblages in urban streams, as described by size spectra attributes (i.e. slopes, intercepts, number of logarithmic size classes occupied, and residual variance), varies with watershed size, land use and water quality. Streams size spectra of the Ottawa-Gatineau region have relatively shallow slopes, reflecting relatively higher densities of organisms in the larger size classes compared to other ecosystem types (e.g. lakes, oceans, soils, coastal waters). Size spectra slopes, density corrected for size, number of size classes, and residual variance vary predictably along gradients of watershed size, watershed proportion of natural land use and periphyton chlorophyll a. A systematic trend of declining spectra slopes with increasing periphyton biomass suggests that ecological efficiency declines in urban eutrophic streams.