Apportioning sources of chemicals of emerging concern along an urban river with inverse modelling.

Concentrations of chemicals in river water provide crucial information for assessing environmental exposure and risks from fertilisers, pesticides, heavy metals, illicit drugs, pathogens, pharmaceuticals, plastics and perfluorinated substances, among others. However, using concentrations measured along waterways (e.g., from grab samples) to identify sources of contaminants and understand their fate is complicated by mixing of chemicals downstream from diverse diffuse and point sources (e.g., agricultural runoff, wastewater treatment plants). To address this challenge, a novel inverse modelling approach is presented. Using waterway network topology, it quantifies locations and concentrations of contaminant sources upstream by inverting concentrations measured in water samples. It is computationally efficient and quantifies uncertainty. The approach is demonstrated for 13 contaminants of emerging concern (CECs) in an urban stream, the R. Wandle (London, UK). Mixing (the forward problem) was assumed to be conservative, and the location of sources and their concentrations were treated as unknowns to be identified. Calculated CEC source concentrations, which ranged from below detection limit (a few ng/L) up to 1µg/L, were used to predict concentrations of chemicals downstream. Using this approach, >90% of data were predicted within observational uncertainty. Principal component analysis of calculated source concentrations revealed signatures of two distinct chemical sources. First, pharmaceuticals and insecticides were associated with a subcatchment containing a known point source of treated effluent from a wastewater treatment plant. Second, illicit drugs and salicylic acid were associated with multiple sources, interpreted as input from untreated sewage including Combined Sewer Overflows (CSOs), misconnections, runoff and direct disposal throughout the catchment. Finally, a simple algorithmic approach that incorporates network topology was developed to design sampling campaigns to improve resolution of source apportionment. Inverse modelling of contaminant measurements can provide objective means to apportion sources in waterways from spot samples in catchments on a large scale.

Understanding seasonal variations in As and Pb river fluxes and their regulatory mechanisms through monitoring data.

The Doce River Basin (DRB) suffers with the adverse impacts of mining activities, due to its high level of urbanization and numerous industrial operations. In this study, we present novel insights into contaminant flow dynamics, seasonal variations, and the primary factors driving concentration levels within the region. We conducted an extensive analysis using a database sourced from the literature, which contained data on the contamination of arsenic (As) and lead (Pb) in the Doce River. Our primary aim was to investigate the patterns of As and Pb flow throughout the entire basin, their response to seasonal fluctuations, and the key parameters influencing their concentration levels. The results showed significant seasonal fluctuations in As and Pb fluxes, peaking during the rainy season. The 2015 Fundão dam breach in the DRB led to notable changes, elevating elemental concentrations, particularly As and Pb, which were subsequently transported to the Atlantic Ocean. These increased concentrations were primarily associated with iron and manganese oxides, hydroxides, and sulfates, rather than precipitation, as evidenced by regressions with low R2 values for both As (R2 = 0.07) and Pb (R2 < 0.001), concerning precipitation. The PCA analysis further supports the connection between these elements and the oxides and hydroxides of Fe and Mn. The approach employed in this study has proven to be highly effective in comprehending biogeochemical phenomena by leveraging data from the literature and could be a model for optimizing resources by capitalizing on existing information to provide valuable insights for drainage basin management, particularly during crises.

Research on the non-point source pollution of microplastics.

Microplastics are characterized with universality, persistence and toxicity to aquatic organisms, the pollution of microplastics has attracted worldwide attention. At present, studies on microplastic pollution were mainly focused on the composition, abundance and species of microplastics in water bodies and sediments, and few studies were focused on the source and influence characteristics of microplastics in surface water bodies. Starting from the sources of microplastic pollution in surface water of this paper, the pollution status of agricultural microplastics was analyzed, and the importance and urgency of studying microplastic pollution in agricultural non-point sources were put forward. Therefore, it was intended to provide effective scientific basis and technical support for the control of microplastics non-point source pollution in river basins.

Transformation of Aquatic Plant Diversity in an Environmentally Sensitive Area, the Lake Taihu Drainage Basin.

Located downstream of the Yangtze River Delta, the Lake Taihu drainage basin (LTDB) is one of the most developed areas in China. This area currently faces population and development issues, as well as many environmental problems, such as cultural eutrophication, algal blooms, and loss of native aquatic plants. Changes in aquatic biodiversity have received less attention than have changes in terrestrial habitats because relevant observations are lacking. In this study, information from 2010, 2014, and 2018 concerning the transformation of the aquatic plant biodiversity was obtained. The results showed that the dominant aquatic plants have changed from native plants to invasive plants. Aquatic plant biodiversity showed a decreasing trend, which may reduce the freshwater ecosystem function, and anthropogenic activities accounted for these changes. How to prevent the decline in aquatic plants and control the invasion of introduced aquatic plants should be a priority in the management of aquatic plants in the LTDB.

Spatially differentiated regulation: Can it save the Baltic Sea from excessive N-loads?

The Baltic Sea Action Plan and the EU Water Framework Directive both require substantial additional reductions of nutrient loads (N and P) to the marine environment. Focusing on nitrogen, we present a widely applicable concept for spatially differentiated regulation, exploiting the large spatial variations in the natural removal of nitrate in groundwater and surface water. By targeting mitigation measures towards areas where nature's own capacity for removal is low, spatially differentiated regulation can be more cost-effective than the traditional uniform regulation. We present a methodology for upscaling local modelling results on targeted measures at field scale to Baltic Sea drainage basin scale. The paper assesses the potential gain and discusses key challenges related to implementation of spatially differentiated regulation, including the need for more scientific knowledge, handling of uncertainties, practical constraints related to agricultural practice and introduction of co-governance regimes.

Lanlabeo duanensis, a new genus and species of labeonin fish (Teleostei: Cyprinidae) from southern China.

Lanlabeo, a new genus of fish belonging to the family Cyprinidae, is described from the Pearl River drainage basin in Guangxi Province, southern China. This new genus is distinguished from all other genera of the cyprinid tribe Labeonini by a combination of morphological and phylogenetic characters. It differs morphologically from all other Asian labeonins in its uniquely modified oromandibular morphology. For example, this genus has a frenum connecting the upper jaw and lower lip at the corner of the mouth, regularly arranged papillae densely scattered over the ventral margin of the rostral cap, a vestigial upper lip, a rostral cap overlying the upper jaw and with a fimbriate posterior margin, and a lower lip divided into two lateral fleshy lobes and one central plate. These two lateral fleshy lobes are small and translucent, and the median lobe of the lower lip is large and has papillae regularly arranged in many transverse rows. In the lower jaw, the dentary is transversely L-shaped in ventral view because its anterior part forms a right-angle turn and its transverse branch is anterioposteriorly expanded. In addition, analyses of four nuclear gene datasets indicate that this new genus forms a highly divergent lineage within the Labeonini, and that Lanlabeo is closely related to the genus Ptychidio. Therefore, based on morphometric differences and phylogenetic relationships, we describe this new genus herein as Lanlabeo, containing the new species Lanlabeo duanensis.

Geostatistics as a tool to improve the natural background level definition: An application in groundwater.

The Natural Background Level (NBL), suggested by UE BRIDGE project, is suited for spatially distributed datasets providing a regional value that could be higher than the Threshold Value (TV) set by every country. In hydro-geochemically dis-homogeneous areas, the use of a unique regional NBL, higher than TV, could arise problems to distinguish between natural occurrences and anthropogenic contaminant sources. Hence, the goal of this study is to improve the NBL definition employing a geostatistical approach, which reconstructs the contaminant spatial structure accounting geochemical and hydrogeological relationships. This integrated mapping is fundamental to evaluate the contaminant's distribution impact on the NBL, giving indications to improve it. We decided to test this method on the Drainage Basin of Venice Lagoon (DBVL, NE Italy), where the existing NBL is seven times higher than the TV. This area is notoriously affected by naturally occurring arsenic contamination. An available geochemical dataset collected by 50 piezometers was used to reconstruct the spatial distribution of arsenic in the densely populated area of the DBVL. A cokriging approach was applied exploiting the geochemical relationships among As, Fe and NH4+. The obtained spatial predictions of arsenic concentrations were divided into three different zones: i) areas with an As concentration lower than the TV, ii) areas with an As concentration between the TV and the median of the values higher than the TV, and iii) areas with an As concentration higher than the median. Following the BRIDGE suggestions, where enough samples were available, the 90th percentile for each zone was calculated to obtain a local NBL (LNBL). Differently from the original NBL, this local value gives more detailed water quality information accounting the hydrogeological and geochemical setting, and contaminant spatial variation. Hence, the LNBL could give more indications about the distinction between natural occurrence and anthropogenic contamination.

Investigating the role of SPECT/CT in dynamic sentinel lymph node biopsy for penile cancers.

PURPOSE: Currently, most centres use 2-D planar lymphoscintigraphy when performing dynamic sentinel lymph node biopsy in penile cancer patients with clinically impalpable inguinal nodes. This study aimed to investigate the role of SPECT/CT following 2-D planar lymphoscintigraphy (dynamic and static) in the detection and localization of sentinel lymph nodes in the groin. METHODS: A qualitative (visual) review was performed on planar followed by SPECT/CT lymphoscintigraphy in 115 consecutive patients (age 28-86 years) who underwent injection of 99mTc-nanocolloid followed by immediate acquisition of dynamic (20 min) and early static scans (5 min) initially and further delayed static (5 min) images at 120 min followed by SPECT/CT imaging. The lymph nodes detected in each groin on planar lymphoscintigraphy and SPECT/CT were compared. RESULTS: A total of 440 and 467 nodes were identified on planar scintigraphy and SPECT/CT, respectively. Overall, SPECT/CT confirmed the findings of planar imaging in 28/115 cases (24%). In the remaining 87 cases (76%), gross discrepancies were observed between planar and SPECT/CT images. SPECT/CT identified 17 instances of skin contamination (16 patients, 13%) and 36 instances of in-transit lymphatic tract activity (24 patients, 20%) that had been interpreted as tracer-avid lymph nodes on planar imaging. In addition, SPECT/CT identified 53 tracer-avid nodes in 48 patients (42%) that were not visualized on planar imaging and led to reclassification of the drainage basins (pelvic/inguinal) of 27 tracer-avid nodes. CONCLUSIONS: The addition of SPECT/CT improved the rate of detection of true tracer-avid lymph nodes and delineated their precise (3-D) anatomic localization in drainage basins.

Integrating High Resolution Water Footprint and GIS for Promoting Water Efficiency in the Agricultural Sector: A Case Study of Plantation Crops in the Jordan Valley.

Addressing the global challenges to water security requires a better understanding of humanity's use of water, especially the agricultural sector that accounts for 70% of global withdrawals. This study combined high resolution-data with a GIS system to analyze the impact of agricultural practices, crop type, and spatial factors such as drainage basins, climate, and soil type on the Water Footprint (WF) of agricultural crops. The area of the study, the northern Lower Jordan Valley, covers 1121 ha in which three main plantation crops are grown: banana (cultivated in open-fields or net-houses), avocado and palm-dates. High-resolution data sources included GIS layers of the cultivated crops and a drainage pipe-system installed in the study area; meteorological data (2000-2013); and crop parameters (yield and irrigation recommendations). First, the study compared the WF of the different crops on the basis of yield and energy produced as well as a comparison to global values and local irrigation recommendations. The results showed that net-house banana has the lowest WF based on all different criteria. However, while palm-dates showed the highest WF for the yield criteria, it had the second lowest WF for energy produced, emphasizing the importance of using multiple parameters for low and high yield crop comparisons. Next, the regional WF of each drainage basin in the study area was calculated, demonstrating the strong influence of the Gray WF, an indication of the amount of freshwater required for pollution assimilation. Finally, the benefits of integrating GIS and WF were demonstrated by computing the effect of adopting net-house cultivation throughout the area of study with a result a reduction of 1.3 MCM irrigation water per year. Integrating the WF methodology and local high-resolution data using GIS can therefore promote and help quantify the benefits of adopting site-appropriate crops and agricultural practices that lower the WF by increasing yield, reducing water consumption, and minimizing negative environmental impacts.

Distribution characteristics and source apportionment of polycyclic aromatic hydrocarbons (PAHs) in the Liao River drainage basin, northeast China.

The Liao River drainage basin, which is one of China's seven major rivers basins, is located in northeast China. This region is characterized by important industrial bases including steel factories and oil and chemical plants, all of which have the potential to contribute pollutants to the drainage basin. In this study, 16 polycyclic aromatic hydrocarbons (PAHs) in water and suspended particulate matter (SPM) in the major rivers of the Liao River drainage basin were identified and quantified by gas chromatography mass spectrometry (GC/MS). The total PAH concentrations ranged from 0.4 to 76.5 µg/g (dry weight) in SPM and 32.6 to 108 ng/L in surface water, respectively. Low-ring PAHs (including two- and three-ring PAHs) were dominant in all PAH samples, and the level of low-ring PAHs in surface water was higher than that in SPM. The proportion of two-ring PAHs was the highest, accounting for an average of 68.2 % of the total PAHs in surface water, while the level of three-ring PAHs was the highest in SPM, with an average of 66.3 %. When compared with other river systems, the concentrations of PAHs in the Liao River drainage basin were lower. Identification of the emission sources based on diagnostic ratios suggested petroleum and fossil fuel combustion were important contribution to PAHs in the study area.

The legacy of lead (Pb) in fluvial bed sediments of an urban drainage basin, Oahu, Hawaii.

The study of fluvial bed sediments is essential for deciphering the impact of anthropogenic activities on water quality and drainage basin integrity. In this study, a systematic sampling design was employed to characterize the spatial variation of lead (Pb) concentrations in bed sediment of urban streams in the Palolo drainage basin, southeastern Oahu, Hawaii. Potentially bioavailable Pb was assessed with a dilute 0.5 N HCl extraction of the <63 µm grain-size fraction from the upper bed sediment layer of 169 samples from Palolo, Pukele, and Waiomao streams. Contamination of bed sediments was associated with the direct transport of legacy Pb from the leaded gasoline era to stream channels via a dense network of storm drains linked to road surfaces throughout the basin. The Palolo Stream had the highest median Pb concentration (134 mg/kg), and the greatest road and storm drain densities, the greatest population, and the most vehicle numbers. Lower median Pb concentrations were associated with the less impacted Pukele Stream (24 mg/kg), and Waiomao Stream (7 mg/kg). The median Pb enrichment ratio values followed the sequence of Palolo (68) > Pukele (19) > Waiomao (8). Comparisons to sediment quality guidelines and potential toxicity estimates using a logistic regression model (LRM) indicated a significant potential risk of Palolo Stream bed sediments to bottom-dwelling organisms.

Landscape structure in the Pirapó, Paranapanema 3 and 4 Hydrographic Unit, in the state of Paraná, Brazil / Estrutura da paisagem na Unidade Hidrográfica Pirapó, Paranapanema 3 e 4, no estado do Paraná, Brasil

The aim of this study is to characterize the Pirapó, Paranapanema 3 and 4 Hydrographic Unit, emphasizing its physical attributes and processes of use and occupation, responsible for the structure of the current landscape and the state of its water resources. The recognition of the landscape’s spatial structure in the hydrographic unit and its drainage basins was obtained by integrated analysis of the main elements that compose it: geology, landforms (hypsometric and slope), soils, climate and land use. Analysis revealed that within each drainage basin several variations in the spatial structure of the landscape occur which produce an internal compartmentalization. Each compartment is defined by its own geo-ecological structure, physiognomic standards and dynamics, reflected in its potentialities and vulnerabilities and in the conditions of water resources in the wake of occupation and use over time.

Resumo O objetivo deste trabalho é caracterizar a Unidade Hidrográfica do Pirapó, Paranapanema 3 e 4, ressaltando os seus atributos físicos e os processos de uso e ocupação, responsáveis pela estrutura da paisagem atual e pelo estado dos seus recursos hídricos. O reconhecimento da estrutura espacial da paisagem na unidade hidrográfica e nas suas bacias foi obtido por meio da análise integrada dos principais elementos que a compõe: geologia, relevo, solos, clima e uso da terra. A análise mostrou que no interior de cada bacia hidrográfica ocorrem variações na estrutura espacial da paisagem que produzem uma compartimentação interna. Cada compartimento se define por uma estrutura geoecológica, padrões fisionômicos e dinâmicos próprios o que se reflete nas suas potencialidades e vulnerabilidades e nas condições dos seus recursos hídricos, em face das formas de ocupação e uso ao longo do tempo.

Landscape structure in the Pirapó, Paranapanema 3 and 4 Hydrographic Unit, in the state of Paraná, Brazil

The aim of this study is to characterize the Pirapó, Paranapanema 3 and 4 Hydrographic Unit, emphasizing its physical attributes and processes of use and occupation, responsible for the structure of the current landscape and the state of its water resources. The recognition of the landscapes spatial structure in the hydrographic unit and its drainage basins was obtained by integrated analysis of the main elements that compose it: geology, landforms (hypsometric and slope), soils, climate and land use. Analysis revealed that within each drainage basin several variations in the spatial structure of the landscape occur which produce an internal compartmentalization. Each compartment is defined by its own geo-ecological structure, physiognomic standards and dynamics, reflected in its potentialities and vulnerabilities and in the conditions of water resources in the wake of occupation and use over time.

Resumo O objetivo deste trabalho é caracterizar a Unidade Hidrográfica do Pirapó, Paranapanema 3 e 4, ressaltando os seus atributos físicos e os processos de uso e ocupação, responsáveis pela estrutura da paisagem atual e pelo estado dos seus recursos hídricos. O reconhecimento da estrutura espacial da paisagem na unidade hidrográfica e nas suas bacias foi obtido por meio da análise integrada dos principais elementos que a compõe: geologia, relevo, solos, clima e uso da terra. A análise mostrou que no interior de cada bacia hidrográfica ocorrem variações na estrutura espacial da paisagem que produzem uma compartimentação interna. Cada compartimento se define por uma estrutura geoecológica, padrões fisionômicos e dinâmicos próprios o que se reflete nas suas potencialidades e vulnerabilidades e nas condições dos seus recursos hídricos, em face das formas de ocupação e uso ao longo do tempo.

Seasonality of macroalgal communities in a subtropical drainage basin in Paraná state, southern Brazil

Seasonal dynamics of macroalgal communities was analyzed monthly by samplings in three stream segments of the Pedras River Basin, mid-south region of Paraná State, southern Brazil, from April 2004 to March 2005. The seasonal fluctuations in macroalgal species richness and abundance were correlated with selected environmental variables. In general, the seasonal distribution patterns of these communities were distinct from those reported from other tropical and temperate regions, with higher macroalgal richness and abundance observed from late spring to late fall. Multiple linear regression analysis revealed that the stream variable most closely related with the temporal distribution pattern observed was temperature, which had a very similar seasonal pattern to the biological parameters. On the other hand, the floristic composition was quite diverse in the streams sampled. Among the 25 taxa identified, only two were common to the three streams whereas 15 were restricted to a single sampling site. These data indicate that, although temperature seems to be an effective relationship with global temporal pattern, particular characteristics of each stream can strongly influence the seasonal tendencies in local scale. The results of Detrended Correspondence Analysis (DCA) and Cluster Analysis corroborated this observation.

A dinâmica sazonal das comunidades de macroalgas foi analisada mensalmente através de amostragens em três segmentos de riachos da Bacia do Rio das Pedras, região centro-sul do Estado do Paraná, Sul do Brasil, de abril de 2004 a março de 2005. As flutuações sazonais na riqueza e abundância de espécies de macroalgas foram correlacionadas com variáveis ambientais selecionadas. Em geral, os padrões de distribuição sazonal destas comunidades foram distintos daqueles reportados para outras regiões tropicais e temperadas, com maiores valores de riqueza e abundância observados no período compreendido entre o final da primavera e o final do outono. As análises de regressão linear múltipla revelaram que a variável do riacho mais fortemente relacionada com o padrão de distribuição temporal observado foi a temperatura, que teve um padrão sazonal muito similar àqueles observados para os parâmetros biológicos. Por outro lado, a composição florística foi bastante diversa nos riachos amostrados. Dentre os 25 táxons identificados, somente dois foram comuns aos três riachos, enquanto que 15 foram restritos a um único ponto de amostragem. Estes dados indicam que, embora a temperatura pareça ter tido uma relação efetiva com o padrão temporal global, características particulares de cada riacho podem influenciar fortemente as tendências sazonais em escala local. Os resultados da Análise de Correspondência Destendenciada (ADC) e da Análise de Grupamento corroboraram esta observação.

Seasonality of macroalgal communities in a subtropical drainage basin in Paraná state, southern Brazil / Sazonalidade das comunidades de macroalgas em uma bacia de drenagem subtropical no estado do Paraná, sul do Brasil

Seasonal dynamics of macroalgal communities was analyzed monthly by samplings in three stream segments of the Pedras River Basin, mid-south region of Paraná State, southern Brazil, from April 2004 to March 2005. The seasonal fluctuations in macroalgal species richness and abundance were correlated with selected environmental variables. In general, the seasonal distribution patterns of these communities were distinct from those reported from other tropical and temperate regions, with higher macroalgal richness and abundance observed from late spring to late fall. Multiple linear regression analysis revealed that the stream variable most closely related with the temporal distribution pattern observed was temperature, which had a very similar seasonal pattern to the biological parameters. On the other hand, the floristic composition was quite diverse in the streams sampled. Among the 25 taxa identified, only two were common to the three streams whereas 15 were restricted to a single sampling site. These data indicate that, although temperature seems to be an effective relationship with global temporal pattern, particular characteristics of each stream can strongly influence the seasonal tendencies in local scale. The results of Detrended Correspondence Analysis (DCA) and Cluster Analysis corroborated this observation.

A dinâmica sazonal das comunidades de macroalgas foi analisada mensalmente através de amostragens em três segmentos de riachos da Bacia do Rio das Pedras, região centro-sul do Estado do Paraná, Sul do Brasil, de abril de 2004 a março de 2005. As flutuações sazonais na riqueza e abundância de espécies de macroalgas foram correlacionadas com variáveis ambientais selecionadas. Em geral, os padrões de distribuição sazonal destas comunidades foram distintos daqueles reportados para outras regiões tropicais e temperadas, com maiores valores de riqueza e abundância observados no período compreendido entre o final da primavera e o final do outono. As análises de regressão linear múltipla revelaram que a variável do riacho mais fortemente relacionada com o padrão de distribuição temporal observado foi a temperatura, que teve um padrão sazonal muito similar àqueles observados para os parâmetros biológicos. Por outro lado, a composição florística foi bastante diversa nos riachos amostrados. Dentre os 25 táxons identificados, somente dois foram comuns aos três riachos, enquanto que 15 foram restritos a um único ponto de amostragem. Estes dados indicam que, embora a temperatura pareça ter tido uma relação efetiva com o padrão temporal global, características particulares de cada riacho podem influenciar fortemente as tendências sazonais em escala local. Os resultados da Análise de Correspondência Destendenciada (ADC) e da Análise de Grupamento corroboraram esta observação.

Seasonal variation in some physical and chemical parameters of three rivers belonging to a drainage basin in the mid-southern region of Paraná state, southern Brazil - DOI: 10.4025/actascibiolsci.v30i4.5873 / Variação sazonal de alguns parâmetros físicos e químicos em três rios pertencentes a uma bacia de drenagem na região centro-sul do Estado do Paraná, Sul do Brasil - DOI: 10.4025/actascibiolsci.v30i4.5873

Three small rivers belonging to the Rio das Pedras basin, located in the mid-southern region of Paraná state, were studied in order to evaluate the seasonal variation pattern of some physical and chemical parameters. Monthly samplings were carried out from April 2004 to March 2005. The following limnological parameters were measured: water temperature, specific conductance, oxygen saturation, pH, turbidity, current velocity and depth. The waters of the Rio das Pedras basin presented very peculiar characteristics, showing typical seasonal patterns for some of the studied limnological variables. An Analysis of Variance (Anova) showed significant differences only for pH and depth among streams. A Principal Component Analysis (PCA) showed a weak tendency to form groups based on seasons instead of sampling sites. The results, in general, indicate that temporal variations of the environmental parameters analyzed were not sufficient to draw a clear seasonal pattern in the Rio das Pedras basin. Most likely, the lack of an obvious seasonal pattern has been provoked by a particular regional precipitation regime, where rains are frequent and well-distributed throughout the year.

Três rios de pequeno porte pertencentes à bacia do rio das Pedras, localizada na região centro-sul do Estado do Paraná, foram estudados com o objetivo de se analisar o padrão de variação sazonal de alguns parâmetros físicos e químicos da água. Os trabalhos de campo foram realizados no período de abril de 2004 a março de 2005 por meio de amostragens mensais. Os seguintes parâmetros limnológicos foram avaliados: temperatura da água, condutividade específica, oxigênio dissolvido, pH, turbidez, velocidade da correnteza e profundidade. As águas da bacia do rio das Pedras mostraram características muito peculiares, apresentando um padrão sazonal típico para algumas das variáveis limnológicas estudadas. A Análise de Variância (Anova) mostrou diferenças significativas entre riachos apenas para pH e profundidade. A Análise dos Componentes Principais (PCA) revelou apenas uma sutil tendência para a organização de grupos por estação sazonal ao invés de pontos de amostragem, indicando que, de modo geral, as variações temporais dos parâmetros ambientais analisados não foram suficientes para caracterizar um padrão sazonal nítido na bacia do rio das Pedras. Provavelmente, a ausência de um claro padrão sazonal tenha sido provocada por um regime pluviométrico regional particular, onde as chuvas são frequentes e bem distribuídas ao longo do ano.