Thesis (M.S.)--Naval Postgraduate School, 1971. / Includes bibliographical references (leaves 141-142).

Extensive experimental data is available from previous research into the behaviour of buoyant jets released into an unstratified ambient. The experimental data has been the basis for theoretical and numerical modelling work, and currently several numerical models exist that are employed in the design of engineering structures built for the disposal of wastewater in the ocean. However there are still flow configurations with limited or no available experimental data, and hence confidence in the use of the models under some circumstances is limited. These circumstances include two-dimensional trajectory flows that are discharged at oblique angles to the ambient and buoyant jet flows with three-dimensional trajectories. As part of the current project an experimental investigation is conducted into the behaviour of discharges that have either two-dimensional or three-dimensional trajectories, focussing particularly on those configurations with currently limited available experimental data. A light attenuation technique is developed for the investigation of such flows, largely because it enables the behaviour of discharges with three-dimensional trajectories to be recorded with relative ease. However, this technique provides integrated views of the flow and hence the interpretation of the integrated concentration data is aided by assumed mean cross-sectional concentration profiles. In the strongly advected region (with the exception of the weak-jet) a double-Gaussian approximation is shown to provide a reasonable representation of mean concentration profiles. In the weakly advected regions and the weak-jet region, it is well- known that a single Gaussian adequately represents the mean flow structure. A new numerical model, the Momentum Model, is developed to assist in the design and to monitor the performance of the experimental investigation. Unlike other models, the behaviour of the flow is determined by the relative magnitudes of the initial excess momentum flux, the buoyancy-generated momentum flux and the entrained ambient momentum flux. It is shown that ratios of these momentum fluxes are equivalent to the length-scales traditionally employed for this task. Predictions from the Momentum Model are compared with data from the current and previous experimental investigations and, in addition, predictions from two representative numerical models, VisJet and CorJet. Predictions from the Momentum Model are shown to be consistent with data for a wide variety of discharge configurations. These predictions are also generally consistent with those of VisJet and CorJet. However, the experimental results from the II buoyant jet discharged in a moving ambient show that the spreading rates of the strongly advected flows (puffs and thermals) differ, and while this difference is incorporated into the Momentum Model, it is not evident in the VisJet and CorJet predictions. Numerical model predictions of negatively buoyant discharges are shown to be inadequate. This discharge configuration is investigated in some detail experimentally and additional analytical solutions of the flow behaviour are developed to aid in the interpretation of the flow behaviour. The experimental results show that buoyancy-induced instabilities on the inner side of the jets, which generate additional vertical mixing, significantly alter the form of the mean concentration profiles in this region. This results in considerably higher integrated dilutions along the flow centreline. Another significant difference between the newly developed Momentum Model and the existing numerical models (VisJet and CorJet), is the approach taken to dealing with oblique discharges in a cross-flow. Experimental results in combination with additional analytical solutions show that for initial discharge angles of 20° and less, an oblique discharge in a cross-flow becomes a weak-jet in the strongly advected region, and for angles of 40° and above, the flow becomes a puff. The strongly advected behaviour predicted by the Momentum Model changes abruptly at the transition angle, and is reasonably consistent with the data. The gradual change in strongly advected behaviour employed by VisJet and CorJet does not appear to be appropriate in the puff region. Finally a preliminary experimental investigation of discharges with three-dimensional trajectories shows that there are significant discrepancies between the predicted behaviour and the experimental data. This is surprising given the numerical models are, for the most part, able to predict the behaviour of flows with two-dimensional paths with reasonable accuracy. It is evident that flows with three-dimensional paths are modified more severely by the different directions of the initial, buoyancy-generated, and entrained ambient momentum fluxes than the current models suggest.

Consumers in marine and estuarine environments have a strong reliance on planktonic and benthic primary production. These two basal resources form the foundation of aquatic food webs, yet the abundance of phytoplankton and benthic algae are frequently inversely related due to competition for light and nutrients. As a result, optimal habitats for benthic and planktonic consumers vary spatially and temporally. To investigate these trends, three studies were conducted focusing on light attenuation and basal resources in a bay, river, and on a continental shelf. δ13C and δ15N stable isotopes can be used as endogenous tracers to determine both the trophic level and basal resource use of consumers. δ13C values of primary producers are determined by the isotopic values of available CO2 and by the degree of photosynthetic fractionation (εp) that occurs during photosynthesis. εp by aquatic algae is greater in high CO2concentrations, high light, during slow growth rates, and for cells with a small surface area to volume ratio. Interaction among these parameters complicates prediction of algal εp in a natural setting, prompting the investigation as to which factors would impact εp and δ13C in a dynamic estuary. Community-level fractionation of an assemblage of filamentous algae, pennate diatoms, and centric diatoms grown on glass plates was found to be positively correlated with photosynthetically active radiation (PAR), resulting in higher δ13C values for organic matter in low-light conditions. These results support the concept that the low-light benthic environment may contribute to the widely observed phenomenon of ~5 / higher δ13C values in benthic algae compared to phytoplankton. Spatial and temporal variability in the isotopic baseline provides evidence of shifting biogeochemical controls on primary production. The West Florida Shelf in the eastern Gulf of Mexico transitions from a eutrophic ecosystem near the Mississippi River to an oligotrophic ecosystem in offshore continental shelf waters. Spatiotemporal variability in the δ13C and δ15N signatures of primary producers and fish populations were examined along this gradient. Muscle δ15N from three widely distributed fish species exhibited strong longitudinal isotopic gradients that coincided with the principal trophic gradient, whereas δ13C values of fish muscle and benthic algae were correlated with depth. The three fish species had relatively high site fidelity, as isotopic gradients were consistent between seasons and years. Isotopic mixing models showed all three fish species had a significant reliance on benthic algae as a basal resource. Dynamic models of the West Florida Shelf isotopic baseline were created using spatial data and satellite-derived water quality characteristics as predictors. Models were constructed using data from three fish species and tested on four other species to determine if the models could be extrapolated to new taxa. Both dynamic and static δ15N models had similar predictive capabilities, indicating a fairly stable δ15N baseline. The satellite-derived dynamic variables explained more variation in baseline δ13C than static spatial descriptors. Planktonic primary production can directly impact benthic food chains through phytoplankton deposition. A novel phytoplankton deposition detection method that combined water-column and benthic fluorometry with surficial sediment sampling was developed and assessed in a two-year study of the Caloosahatchee River estuary. Classifications based upon this detection method showed phytoplankton deposition dominated the upstream region and deposition was associated with reduced dissolved oxygen concentrations. Benthic algae dominated in downstream regions, particularly during low freshwater flow conditions when light absorption by colored dissolved organic matter was low. This same Caloosahatchee River estuary study was used to determine if zooplankton aggregate in regions with optimal basal resource availability. The isopod Edotia triloba was found to associate with chlorophyll peaks when freshwater velocity was constant. Chlorophyll peaks were offset downstream or upstream from isopod aggregations when freshwater flow was accelerating or decelerating, implying that phytoplankton and isopods have different response times to changes in flow. Temporal and spatial fluctuations in water quality and primary production introduce instability to aquatic consumers that primarily rely on one basal resource. The current global trends in eutrophication and increasing planktonic production are likely to be a liability for benthic consumers due to increased benthic hypoxia and light attenuation. The results of these studies indicate that both the location of consumers and their isotopic signatures can be impacted by factors, such as light attenuation, that control benthic and planktonic primary production.

This dissertation describes investigations of fully turbulent decelerating hydraulically roughbed flow over gravel and the development of technology to measure turbulence and associated sediment transport in streams. Theory is developed for predicting velocity distributions in simple uniform flow using the asymptotic invariance principle and tested using laboratory and field collected data. A mixed scale is developed that accounts for bed derived turbulent structures throughout the flows depth and is used to parameterize the external boundary’s effect on the flow for the logarithmic and outer layers. The asymptotic invariance principle and similarity analysis is conducted for the equations of motion in the outer region of decelerating flow over gravel to define equilibrium conditions for this class of flows with the velocity scale is the freestream velocity. The combination of time series and time averaged statistical analysis of turbulent flow is used to elucidate the structure of flow under decelerating conditions. Time averaged statistical measures of turbulence confirm results of others for higher Froude number approaching transcritical and time series analysis shows the effects of decelerating flow on turbulence to be frequency dependent. Wireless velocity sensors were developed and found capable of measuring time averaged velocity and able to resolve macroturbulence from time series data. A semi-theoretical model of elastic deformation of cantilever beams under hydraulic forcing was coupled with circuit theory to develop a calibration procedure for the VBS that requires only three measurement points, one of which is at zero velocity. Light based sensors are developed to estimate light attenuation in water for ecological research or estimating sediment concentration in water. A semi-theoretical scaling of light attenuation and sediment properties was developed which predicts light attenuation from sediment properties. The combination of new theory on open channel velocity, turbulent structure and field sensors for measuring turbulence and sediment offers the possibility to extend our laboratory knowledge to realistic flow situations.

The quest to discover simple, sensitive and global bioindicators of nutrient enrichment and ecological health continues. The present study is the first to address this quest in Hervey Bay by investigating links between key physico-chemical water quality parameters and two diatom forms. Free floating in the water column as phytoplankton, and attached to seagrass leaves and artificial substrates as microalgal epiphytes, diatoms are assessed for their abundance and diversity along an environmental gradient. Relationships between Secchi depth (Zsd), light attenuation coefficient (Kz) and minimum seagrass compensation depth (Zc) are established for the recovery, growth and survival of aquatic plants following disturbance, with equations derived specifically for this region to allow conversions from Zsd to Kz. These relationships allow predictions to be made and provide a management tool to meet water quality targets and combat elevated nutrient and sediment loads that result from anthropogenic activity and affect all marine life, from microalgae to marine mammals. Environmental links, identified as drivers of change to biodiversity, focus research effort and provide predictive management tools. Consequently, catchment and coastal activities such as dredging, construction and canal development, with the potential to increase nutrient and sediment loads, can be managed and scheduled at times least likely to adversely impact near shore ecosystems and therefore improve the balance between growth and sustainability. Seasonal and zone differences were significant for many of the water quality parameters monitored in Hervey Bay during 1994. Water clarity measures consistently showed significant differences between near and offshore zones (Secchi depth; P<0.01, turbidity; P<0.05 and TSS; P<0.01) as well as oxygen (P<0.01), soluble reactive phosphate (SRP, P<0.05), oxides of nitrogen (NOx, P<0.01), chlorophyll a (Chl a, P<0.01) and pH (P<0.01). Some default trigger values for water quality targets listed by ANZECC/ARMCANZ (2000) for concentrations of key indicators, a threshold for risk of adverse biological effects, were exceeded in dry and flood periods during the 1993 to 1995 survey. The community structure of phytoplankton and seagrass epiphytes were examined by monitoring changes to and 35 seagrass epiphyte species coincident with changes in some key water quality parameters along a water quality gradient. Chl a, Secchi depth (Zsd), soluble reactive phosphate (SRP) and pH were found to be the best subset of water quality parameters to maximise the rank correlation with phytoplankton communities whereas NOx and temperature maximised the rank correlation with the Halophila ovalis seagrass epiphyte communities. These parameters statistically link key water quality parameters to changes in phytoplankton and seagrass epiphyte density and assemblage structure and are supported as significant drivers of change in biodiversity research. Evidence for nitrogen limitation was found in the post flood surveys for phytoplankton and the growth and assemblage structure for seagrass systems and their epiphytes. Seasonal and zone differences in phytoplankton assemblage structure were most apparent with some site influence detected. Cylindrotheca closterium dominated the phytoplankton assemblage structure at the near shore zone while Thalassionema nitzschioides and Chaetoceros sp. differentiated the river from the Waste Water Treatment Plant (WWTP) creek site. Rhizolsolenia and Guinardia sp. were found in significantly higher concentrations at offshore sites (P < 0.01) and Thalassionema nitzschioides (P < 0.01), Thalassiosira sp. (P < 0.01) and Pseudonitzschia sp. (P < 0.05) were found in significantly higher abundance in the near shore zone A Trichodesmium bloom was examined and post flood changes to the phytoplankton assemblage structure associated with increased nutrient loads, reduced water clarity (Secchi depth, TSS and turbidity) and changes to pH and salinity were assessed. The results of analyses of variance provided support to multivariate statistical analyses to identify phytoplankton as a useful and sensitive bioindicator of environmental change. Post flood phytoplankton cell density increased and species diversity rose from 10 to 38 species at the Mary River mouth however, the changes to cell density and assemblage structure were not reflected in Chl a concentrations. The Mary River mouth experienced growth of mainly small phytoplankton species (< 20 µm) while Pulgul Creek, a source of WWTP effluent, experienced a disproportional increase in the larger phytoplankton species (>20µm). The increase in phytoplankton cell density at offshore sites occurred for both large and small species. Phytoplankton species dominance changed at each site during the postflood period. C. closterium remained the dominant species but increased from 34 to 648 cells/mL at Pulgul Creek however, C. similis, the second most dominant species was replaced by Pseudonitszchia sp., whose cell density rose from 2.0 to 320 cells/mL. A recent study also found that Cylindrotheca closterium, Skeletonema costatum, and Cyclotella choctawhatcheeana had strong positive relationships with coastal nutrients and suggested these species be used as potential reliable indicators of eutrophication (Toming and Jaanus, 2007). Some Pseudonitszchia sp. and dinoflagellate species have previously been noted as toxic and Chaetoceros sp. are associated with gill damage and fish kills. Rhizosolenia sp. and the Guinardia species G. flaccida and G. striatula, were indicators for the offshore relatively pristine sites, which may conversely, determine these species as indicators of environmental health in this waterway. Specificity of epiphyte attachment to particular seagrass species were detected and microalgal epiphyte assemblages on Halophila ovalis were identified as useful bioindicators of environmental gradients as this seagrass species is located at intertidal, shallow and deep water sites for a substantial part of the year. H. ovalis also recorded the highest average annual epiphyte loads (3873 ± 1882 cells/mm2) with the diatoms Diatoma vulgare and Cocconeis scutellum representing 19.6% and 17.2% of the total epiphyte cover. Highest cell density was recorded in autumn, followed by summer and winter: spring recorded the lowest epiphyte cover. Micro-algal epiphyte load was assessed as dry weight (g/m2), Chl a (µg/L) and cell density (cells/mm2) on artificial seagrass deployed along a water quality gradient. Equations were derived to describe percentage light transmission as a function of each measure of epiphyte load which allows transformation of data from one unit of expression to another and hence, allow comparison of past, current and future studies. Water column light attenuation was evaluated along a water quality gradient and linked to Secchi depths (Zsd) to derive equations that describe this relationship where for Hervey Bay, when Zsd < 4.26m, Kz = -1.2 ln Zsd + 1.74 and when Zsd ≥ 4.26m, Kz=1.37/Zsd. Species succession, diversity and seagrass growth were monitored for the first time during a recovery phase and limits for the seagrass compensation depth (Zc), were established on a seasonal basis for five seagrass species at four locations within intertidal, shallow and deep water zones in Hervey Bay and the Great Sandy Straits. Conceptual models for each site were constructed to describe habitat characteristics and include nutrient concentrations for SRP, NOx and ammonia (NH4+), Chl a, phytoplankton density, epiphyte density and light requirements measured as light attenuation, total suspended sediment, turbidity and Secchi depth at each location. The study provides a descriptive model for light attenuation and establishes (1) an annual and seasonal baseline water quality data set that characterises the waterways of Hervey Bay and the Great Sandy Straits (2) identification of phytoplankton species in Hervey Bay and their response to post flood changes in water quality (3) phytoplankton density and diversity along an environmental gradient with links established to Chl a, Secchi depth, SRP and pH (4) seagrass epiphyte assemblage structure along an environmental gradient with links established to NOx and temperature (5) conversion factors for epiphyte load expressed as dry weight, Chl a and cell density (6) functions to convert Secchi depth to light attenuation coeffiecients (Kz) (7) seagrass species succession at intertidal, shallow and deep water sites during a recovery growth phase in Hervey Bay (8) seagrass compensation depths (Zc) for five seagrass species at four locations and (9) habitat characterisation for seagrass recovery in Hervey Bay. Identification catalogues for phytoplankton and seagrass epiphytes were prepared with light and electron micrographs to assist future identification studies of diatoms in this region and for other similar biogeographical areas. The management of water quality to reach specific targets requires the capacity to predict seagrass compensation depth (Zc) as a function of water quality. Seasonal and annual light attenuation measurements are derived as a function of water quality at intertidal, shallow and deep water habitats during the colonisation of Zostera Capricornii, Halodule uninervis, Halophila ovalis, Halophila spinulosa and Halophila decipiens.

I quantified seasonal variations in corticular photosynthesis in 1st through 5th order branches of Myrica cerifera L. (Myricaceae) in order to determine whether corticular photosynthesis contributes to whole plant carbon gain by reducing respirational CO2 loss. Maximum % refixation was 110 ± 39 % of CO2 efflux in the dark (Rd) in 1st order branches during winter, minimum was 18 ± 3 % in 5th order branches during summer. Variations in % refixation paralleled changes in photosynthetically active radiation (PAR). As light attenuated with increasing branch order % refixation decreased. Increased PAR in the winter due to a more sparse canopy lead to increases in % refixation. Total chlorophyll content and chlorophyll a:b ratios were consistent with shade acclimation as branch order increased. Corticular photosynthesis may be a mechanism to enhance shrub expansion due to increased whole plant carbon use efficiency (CUE) and water use efficiency (WUE) attributed to refixation.

Solar energy is incident on the earth's surface in both short-wave and long-wave parts of the spectrum. The short-wave part of the spectrum is of special interest to oceanographers since the vertical distribution of temperature in the top layer of the ocean is mostly determined by the vertical attenuation of short-wave radiation. There are numerous studies regarding the temperature evolution as a function of time (see Chapter 2 for details). The diurnal and seasonal variation of the heat content (and hence temperature) of the ocean is explored in this thesis. The basis for such heat budget simulation lies in the fact that the heat budget is the primary driver of ocean currents (maybe secondary to wind effects) and these circulation features affect the biological and chemical effects of that region. The vertical attenuation of light (classified to be in the 300-700 nm range) in the top layer of the ocean has been parameterized by several authors. Simpson and Dickey (1981) in their paper have listed the various attenuation schemes in use till then. This includes a single-exponential form, a bimodal exponential form, and a spectral decomposition into nine spectral bands, each with their specific exponential functions with depth. The effects of vertical light attenuation have been investigated by integrating the light models into a 1D and a 3D turbulence closure model. The main part of the thesis is the inclusion of a bottom effect in the shallow waters. Bottom serves two purposes, it reflects some light based on its albedo and it radiates the rest of the light as heat. 1-D simulation including bottom effects clearly indicates the effect of light on the temperature profile and also the corresponding effect on salinity profiles. An extension of the study includes a 3D simulation of the heat budget and the associated circulation and hydrodynamics. Intense heating due to the bottom leads to the formation of hyper-saline waters that percolate down to depths of 50 m in the summer. Such plumes have been simulated by using a 3D numerical ocean model and it is consistent with observations from the Bahamas banks.

ABSTRACT INVESTIGATION OF LIGHT ATTENUATION IN LAKE EYMIR Selen ATIKER M.Sc, Department of Environmental Engineering Supervisor: Assoc. Prof. Dr. Ayseg&uuml / l Aksoy Co-Supervisor: Assoc. Prof. Dr. Selim Sanin January 2012, 164 pages. Light penetration and attenuation has significant impact on the water quality of lakes. Algal activity, which is important for the levels of several water quality parameters, is dependent on light penetration besides availability of nutrients. In this study, change in light penetration and attenuation in Lake Eymir was studied. The relationships of extinction coefficient (ke), and water quality parameters were investigated. The effect of ke on Chl-a over nutrients were investigated. The water quality parameters measured were / total suspended solid (TSS), phosphate, ammonium, nitrate, photosynthetically active radiation (PAR), chlorophyll-a (Chl-a), Secchi disk depth and lake Depth. The measurements were conducted at five different stations in Lake Eymir. Secchi disk, PAR and lake depth measurements were done on site, while TSS, Chl-a and phosphate analyses were done in laboratory, using standard methods. Nitrate and ammonium analyses were conducted through laboratory kits. Linear and non-linear regression models of ke and Chl-a were developed to understand their relationships with the the measured parameters, using XLSTAT software. Analyses of the data at sampling stations revealed that Station 2 and 3 were the most representative stations in general. The model results indicated that ke is as important as nutrients for Chl-a abundance. Secchi disk and Chl-a are the most correlated parameters with ke. Moreover Secchi disk depth is nonlinearly correlated with ke, while linearly correlation is present between Chl-a and ke. &emsp

Submitted by Ana Carolina Campos Gomes (carol.campos01@hotmail.com) on 2018-04-20T17:35:54Z No. of bitstreams: 1 AnaCarolina.pdf: 2801427 bytes, checksum: 1809e31f1376c275f1b3a1c9eca5cf6f (MD5) / Approved for entry into archive by Claudia Adriana Spindola null (claudia@fct.unesp.br) on 2018-04-20T19:06:20Z (GMT) No. of bitstreams: 1 gomes_acc_me_prud.pdf: 2801427 bytes, checksum: 1809e31f1376c275f1b3a1c9eca5cf6f (MD5) / Made available in DSpace on 2018-04-20T19:06:20Z (GMT). No. of bitstreams: 1 gomes_acc_me_prud.pdf: 2801427 bytes, checksum: 1809e31f1376c275f1b3a1c9eca5cf6f (MD5) Previous issue date: 2018-03-23 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O presente trabalho teve como objetivo estimar as profundidades da zona eufótica (Zeu) e do disco de Secchi (ZSD) a partir do coeficiente de atenuação da luz (kd) utilizando dados do sensor Operational Land Imager (OLI)/Landsat-8 no reservatório de Bariri. Como importantes parâmetros de medida da claridade da água, kd, Zeu e ZSD são afetados pelas substâncias opticamente significativas (SOS). A caracterização óptica do reservatório foi realizada a partir de duas campanhas de campo realizadas no período seco, aqui nomeadas como BAR1 (agosto/2016) e BAR2 (junho/2017), que contaram com análises das propriedades ópticas inerentes (POIs), das SOS e da coleta de dados radiométricos para o cálculo da reflectância de sensoriamento remoto (Rsr). A localização do reservatório de Bariri como o segundo do Sistema de Reservatórios em Cascata (SRC) do Rio Tietê promove a heterogeneidade dos seus níveis de eutrofização na direção montante-jusante além de caracterizá-lo como altamente produtivo. As campanhas de campo foram marcadas por uma significativa diferença nos valores de concentração de clorofila-a ([Chl-a]) que apresentou variação média entre 7,99 e 119,76 μg L-1 com os maiores valores em BAR1, com decréscimo das SOS em BAR2 em relação a BAR1 e predomínio de material particulado orgânico (MPO) nas duas campanhas de campo; a turbidez variou entre 5,72 e 16,60 NTU. A absorção por matéria orgânica colorida dissolvida (aCDOM) foi predominante nas duas campanhas de campo, sendo mais expressiva em BAR2. Para as estimativas de kd, nove modelos empíricos e três modelos semi-analíticos baseados em dados radiométricos como razões entre as bandas azul/verde e azul/vermelho do sensor OLI/Landsat-8 e baseados em [Chl-a] foram avaliados. Considerando a propriedade óptica aparente (POA) do kd, um modelo semi-analítico baseado em POIs e na distribuição angular da luz apresentou os menores erros (erro médio percentual absoluto – MAPE) de 40% em relação aos modelos empíricos de [Chl-a] com 60% e de 80% para os modelos empíricos baseados em razões de bandas. A partir das estimativas de kd, modelos de estimativa de Zeu e ZSD foram avaliados. Para as estimativas de Zeu, cinco modelos empíricos, baseados na relação entre o coeficiente de atenuação da luz da radiação fotossinteticamente ativa [kd(PAR)] e de kd em 490 nm [kd(490)], e um modelo semi-analítico, baseado na equação de transferência radiativa, foram considerados; para as estimativas de ZSD, um modelo semi-analítico foi testado. Os resultados obtidos foram melhores para um modelo empírico (erro percentual absoluto – ε) de Zeu com 16% em relação ao modelo semi-analítico (ε 30%) e os erros nas estimativas de ZSD foram de 57%. Os erros nas estimativas de kd revelaram que a acurácia dos modelos empíricos foi comprometida devido à influência por CDOM e que o modelo semi-analítico, por considerar a natureza óptica de kd como uma POA, apresentou os melhores resultados. As estimativas de ZSD também foram afetadas pelas características ópticas de Bariri, não apresentando correlação com a matéria orgânica em BAR2, marcado pelo decréscimo de [Chl-a] e aumento dos valores de aCDOM. Zeu mostrou melhores resultados a partir de um modelo empírico calibrado com dados ópticos semelhantes aos do reservatório de Bariri em comparação ao modelo semi-analítico, desenvolvido para abranger as variações bio-ópticas sazonais e regionais. kd, Zeu e ZSD foram espacializados a partir de imagens do sensor OLI/Landsat-8 permitindo a avaliação espaçotemporal desses parâmetros que apresentaram um padrão sazonal quando analisados em relação aos dados de precipitação. kd apresentou variação entre 0,89 e 5,60 m-1 para o período analisado (2016) e Zeu e ZSD apresentaram variação entre 0,30 e 7,60 m e entre 0,32 e 2,95 m, respectivamente, para o período de 2014-2016. Pode-se concluir então, que apesar das estimativas de kd, Zeu e ZSD terem sido afetadas pela influência de CDOM no reservatório de Bariri, o esquema semi-analítico foi capaz de estimar kd com menor erro e permitiu as estimativas de Zeu e ZSD. / The objective of this present work was estimate the euphotic zone (Zeu) and Secchi disk (ZSD) depths from the light attenuation coefficient (kd) using the Operational Land Imager (OLI)/Landsat-8 data in Bariri reservoir. The kd, Zeu and ZSD are important water clarity parameters and are influenced by the optically significant substances (OSS). The optical characterization was carried out with data collected in two field campaigns in the dry period, here called BAR1 (august/2016) and BAR2 (june/2017), that included analysis of the inherent optical properties (IOPs), of the OSS and radiometric data to calculate the remote sensing reflectance (Rrs). The location of Bariri reservoir as the second of the Cascading Reservoir System (CRS) of Tietê River promotes the heterogeneity of the eutrophication levels from upstream to downstream besides characterizes the reservoir as highly productive. The field campaigns presented a significant difference in chlorophyll-a concentrations ([Chl-a]) with mean variation between 7.99 and 119.76 μg L-1 with the highest values in BAR1, with reduce of the OSS in BAR2 in relation to BAR1 and predominance of organic particulate matter (OPM) in both field campaigns and variation in turbidity from 5.72 to 16.60 NTU. The absorption of chromophoric dissolved organic matter (CDOM) was dominant in both field campaigns and more expressive in BAR2. For the kd estimates, nine empirical models and three semi-analytical models based on radiometric data such as ratios of blue-green and blue-red bands of (OLI)/Landsat 8 sensor and based on [Chl-a] were evaluated. Considering the apparent optical property (AOP) of kd, a semi-analytical model based on IOPs and the light angular distribution presented the lowest errors (mean absolute percentage error – MAPE) of 40% in relation to the empirical models of [Chl-a] with 60% and of 80% for the empirical models based on the band ratios. Through the kd estimates, models to derive Zeu and ZSD were evaluated. For the Zeu estimates, five empirical models were considered based on the relation between the attenuation coefficient of the photosynthetically active radiation [kd(PAR)] and the kd at 490 nm [kd(490)], and one semi-analytical model, based on the radiative transfer equation; for the ZSD estimates, one semi-analytical model was tested. The empirical model of Zeu showed the better results with the (unbiased absolute percentage error – ε) 16% in relation to the semi-analytical model (ε 30%) and the estimates errors of ZSD were 57%. The errors in kd estimates revealed that the accuracy of the empirical models was affected by the CDOM influence in Bariri reservoir and the semi-analytical model presented a better performance when considering the optical nature of kd as an AOP. The ZSD estimates were also affected by the optical characteristics of Bariri with no correlation to the SPM in BAR2, where the [Chl-a] decreased and the aCDOM increased. Zeu showed better results from an empirical model calibrated with similar optical data to Bariri reservoir in relation to the semi-analytical model developed to be applied in a wide range of bio-optical seasonal and regional variations. The kd, Zeu and ZSD were spatially distributed through OLI/Landsat-8 images allowing the temporal-spatial assessment of theses parameters, which presented a seasonal pattern when analyzed in relation to rainfall data. kd presented variation from 0.89 to 5.60 m-1 to the analyzed period (2016) and Zeu and ZSD presented variations between 0.30 and 7.60 m and between 0.32 and 2.95 m, respectively, for 2014-2016 period. It can be concluded, therefore, that despite of the CDOM have affected the kd, Zeu and ZSD retrievals in Bariri reservoir, the semi-analytical scheme was able to estimate kd with lowest error and enable the Zeu and ZSD estimates. / CNPq: 131737/2016-3 / FAPESP: 2012/19821-1 e 2015/21586-9

The availability of light is a primary limiting factor for seagrass recovery and sustainability. Understanding not only the quantity but the quality of light reaching the bottom is an important component to successful seagrass management and the key focus of this study. This study explores the spectral properties of the sub-surface light field in four shallow Seagrass Management Areas (SMA) in Tampa Bay. Wavelength-specific photosynthetically active radiation (PAR(λ)) and the spectral light attenuation coefficient (Kd(λ)) are used to estimate the percent blue, green, and red light remaining at the bottom relative to the surface. LIDAR Bathymetry is combined with Kd(λ) to produce high-resolution maps of percent subsurface light along the seagrass deep edge. The absorptance spectra from two seagrass species together with PAR(λ) is used to calculate the photosynthetically useable radiation (PUR(λ)), a term describing the actual wavelengths of light being used by the seagrass. Based on the average annual Kd(λ) , 32% - 39% percent of PAR reached the bottom at the seagrass deep edge, while only 14% - 18% of blue light reached bottom, suggesting that seagrass may be blue-light limited. Analysis of PUR(λ) data further confirmed that seagrass are blue-light limited. Each SMA was characterized in terms of the inherent optical properties (IOP) of absorption and scatter. Tampa Bay is considered a chlorophyll-dominated estuary. However, in this study, colored dissolved organic matter (CDOM) was the major absorber of blue light, accounting for 60% of the total absorption. To infer past light conditions, the IOPs were related to parameters more commonly used in routine monitoring programs. To estimate Kd(λ) an empirically-derived model using only the total absorption and scatter coefficients was used and resulted in a good fit between measured Kd(480) and modeled Kd(480). A deck-mounted flow-through system was used to survey each SMA for CDOM and chlorophyll a fluorescence, among other properties. A series of SMA-specific predictor equations were empirically derived to relate raw fluorescence to the IOPs. The Kitchen SMA was used as a case study. Survey results show a strong connection between CDOM-rich waters and the mangrove-dominated shoreline.