Eutrophication induced changes in benthic community structure of a flow-restricted tropical estuary (Cochin backwaters), India

The influence of anthropogenic loading on the distribution of soft bottom benthic organisms of a tropical estuary (Cochin backwaters) was examined. The industrial activities were found to be high in the northern and central part of the estuary, where dissolved inorganic nitrogen (DIN > 210 ??M) and phosphorus (DIP > 6.5 ??M) have caused high abundance of chlorophyll a (up to 73 mg m^???3) and accumulation of organic carbon in sediments (up to 5%). Principal component analysis distinguished three zones in the estuary. The central zone (Z1) was characterized by organic enrichment, low species diversity, and increased number of pollution tolerant species. Long-term deterioration of the estuary is indicated by an increase in the nutrients and chlorophyll a levels by sixfold during the last few decades. Flow restrictions in the lower estuary have lead to a fourfold increase in sediment organic carbon over the period of three decades. The reduced benthic diversity followed by an invasion of opportunistic polychaetes (Capitella capitata), are indicative of a stress in the estuary.     

Spatio-temporal variations of organic carbon and chlorophyll degradation products in the surficial sediments of Izmir Bay (Aegean Sea/Turkey)

The aim of this research is to determine the effects of Izmir Big Channel Waste Water Treatment Project on the sediment quality of Izmir Bay. Wastewater treatment improves the water quality. However, sediment does not respond to this treatment as fast as water column. Monitoring of bottom water and sediment quality is necessary for identification of the recovery of the whole ecosystem. For this purpose, bottom water and sediment samples were collected from three stations which are located in the middle and inner parts of the Izmir Bay on a monthly basis between January 2003 and December 2003. Values measured at stations ranged between; 0.54-12.82 microg/L for chlorophyll-a, 0.09-9.32 microg/L for phaeopigment, 0.05-1.91 mg/L for particulate organic carbon in bottom waters, 11.88-100.29 microg/g for chlorophyll degradation products and 1.12-5.39% for organic carbon in sediment samples. In conclusion, it was found that grazing activity explained carbon variations in sediment at station 2, but at station 1 and station 3 carbon variations in sediment were not related to autochthonous biological processes.     

Monsoon-induced changes in the size-fractionated phytoplankton biomass and production rate in the estuarine and coastal waters of southwest coast of India

Changes in the autotrophic pico- (0.2–2 μm), nano- (2–20 μm), and microplankton (>20 μm) biomass (chlorophyll a) and primary production were measured in the estuarine and coastal waters off Cochin, southwest coast of India during the onset and establishment of a monsoon. During this period, the estuary was dominated by nutrient-rich freshwater, whereas the coastal waters were characterized with higher salinity values (>30 psu) and less nutrients. The average surface chlorophyll a concentrations and primary production rates were higher in the estuary (average 13.7 mg m^???3 and 432 mgC m^???3 day^???1) as compared to the coastal waters (5.3 mg m^???3 and 224 mgC m^???3 day^???1). The nanoplankton community formed the major fraction of chlorophyll a and primary production, both in the estuary (average 85 ± SD 8.3% and 81.2 ± SD 3.2%) and the coastal waters (average 73.2 ± SD 17.2% and 81.9 ± 15.7%). Nanoplankton had the maximum photosynthetic efficiency in the coastal waters (average 4.8 ± SD 3.9 mgC mgChl a m^???3 h^???1), whereas in the estuary, the microplankton had higher photosynthetic efficiency (average 7.4 ± 7 mgC mgChl a m^???3 h^???1). The heavy cloud cover and increased water column turbidity not only limit the growth of large-sized phytoplankton in the Cochin estuary and coastal waters but also support the proliferation of nanoplankton community during the monsoon season, even though large variation in nanoplankton chlorophyll a and production exists between these two areas.     

Spatial and temporal variability of water quality in the coral reefs of Tayrona National Natural Park,Colombian Caribbean

Tayrona National Natural Park (TNNP) is a hotspot of coral reef biodiversity in the Colombian Caribbean, located between the city of Santa Marta (>455,000 inhabitants) and several smaller river mouths (Rio Piedras, Mendihuaca, Guachaca). The region also experiences a strong seasonal variation in physical parameters (temperature, salinity, wind, and water currents) due to alternating dry seasons with coastal upwelling and rainy seasons. However, the spatial and temporal effects on water quality parameters relevant for coral reef functioning have not been investigated. Therefore, inorganic nutrient, chlorophyll a, and particulate organic carbon (POC) concentrations along with biological O₂ demand (BOD), pH, and water clarity directly above local coral reefs (~10 m water depth) were monitored for 25 months in four bays along a distance gradient (12–20 km) to Santa Marta in the southwest and to the first river mouth (17–27 km) in the east. This is by far the most comprehensive coral reefs water quality dataset for the region. Findings revealed that particularly during non-upwelling, chlorophyll a and POC concentrations along with BOD significantly increased with decreasing distance to the rivers in the east, suggesting that the observed spatial water quality decline was triggered by riverine runoff and not by the countercurrent-located Santa Marta. Nitrate, nitrite, and chlorophyll a concentrations significantly increased during upwelling, while pH and water clarity decreased. Generally, water quality in TNNP was close to oligotrophic conditions adequate for coral reef growth during non-upwelling, but exceeded critical threshold values during upwelling and in relation to riverine discharge.     

Evaluation of a combined macrophyte–epiphyte bioassay for assessing nutrient enrichment in the Portneuf River,Idaho, USA

We describe and evaluate a laboratory bioassay that uses Lemna minor L. and attached epiphytes to characterize the status of ambient and nutrient-enriched water from the Portneuf River, Idaho. Specifically, we measured morphological (number of fronds, longest surface axis, and root length) and population-level (number of plants and dry mass) responses of L. minor and community-level (ash-free dry mass [AFDM] and chlorophyll a [Chl a]) responses of epiphytes to nutrient enrichment. Overall, measures of macrophyte biomass and abundance increased with increasing concentrations of dissolved phosphorus (P) and responded more predictably to nutrient enrichment than morphological measures. Epiphyte AFDM and Chl a were also greatest in P-enriched water; enrichments of N alone produced no measurable epiphytic response. The epiphyte biomass response did not directly mirror macrophyte biomass responses, illustrating the value of a combined macrophyte–epiphyte assay to more fully evaluate nutrient management strategies. Finally, the most P-enriched waters not only supported greater standing stocks of macrophyte and epiphytes but also had significantly higher water column dissolved oxygen and dissolved organic carbon concentrations and a lower pH. Advantages of this macrophyte–epiphyte bioassay over more traditional single-species assays include the use of a more realistic level of biological organization, a relatively short assay schedule (~10 days), and the inclusion of multiple biological response and water-quality measures.     

Impact of artificial lagoons on seawater quality: evidence from 7 years of physicochemical seawater monitoring

Seven years (2010–2016) of data on the basic physicochemical properties of seawater, temperature, salinity, dissolved oxygen (DO), nutrients, chlorophyll a (Chl a), and hydrocarbons from two lagoons were used to evaluate the impact of the anthropogenic activities inside the lagoon on the water quality and to explore the relationship of any impact from the lagoons’ design. Statistical analysis shows the modification in water quality inside the lagoon compared to the ambient seawater is particularly evident for nitrate, silicate, and Chl a. The modification is attributed to the extensive boat activities in the lagoons and the limited water exchange between the lagoons and ambient seawater. However, the impact to both lagoons is generally limited to inside the lagoons. The oligotrophic state of the two lagoons was evaluated and it was found that the most marked code violations were found in DIN inside both lagoons. In order to explore the design importance, the water exchange and overall water quality was compared between the two lagoons. This study highlights the importance of an environmental design study before the construction of any lagoon project. Proper design would maintain acceptable water quality inside the lagoons, critical for environmental health and supporting continued recreational activities.     

Step-up multiple regression model to compute Chlorophyll a in the coastal waters off Cochin, southwest coast of India

The interaction effects of abiotic processes in the production of phytoplankton in a coastal marine region off Cochin are evaluated using multiple regression models. The study shows that chlorophyll production is not limited by nutrients, but their physiological regulations (responses to nutrients, pH, temperature and salinity) are mainly responsible for the increased biological production. The model explaining 77% of variability for chlorophyll a production is indicative of preconditioning of the coastal waters. The phytoplankton production is found to be sensitive to the environment, which varies seasonally. Further, the study suggests that supply of organic matter and grazing of zooplankton (not included) would improve the model efficiency. Despite this, the good agreement in the computed and measured chlorophyll a values shows that step-up multiple regression model is a useful tool to understand the influence of environmental variables on the production of phytoplankton in these coastal waters.     

Comparative impacts of stormwater runoff on water quality of an urban, a suburban, and a rural stream

Water quality data at 12 sites within an urban, a suburban, and a rural stream were collected contemporaneously during four wet and eight dry periods. The urban stream yielded the highest biochemical oxygen demand (BOD), orthophosphate, total suspended sediment (TSS), and surfactant concentrations, while the most rural stream yielded the highest total organic carbon concentrations. Percent watershed development and percent impervious surface coverage were strongly correlated with BOD (biochemical oxygen demand), orthophosphate, and surfactant concentrations but negatively with total organic carbon. Excessive fecal coliform abundance most frequently occurred in the most urbanized catchments. Fecal coliform bacteria, TSS, turbidity, orthophosphate, total phosphorus, and BOD were significantly higher during rain events compared to nonrain periods. Total rainfall preceding sampling was positively correlated with turbidity, TSS, BOD, total phosphorus, and fecal coliform bacteria concentrations. Turbidity and TSS were positively correlated with phosphorus, fecal coliform bacteria, BOD, and chlorophyll a, which argues for better sedimentation controls under all landscape types.     

Spatio-temporal variations of carbon dioxide and its gross emission regulated by artificial operation in a typical hydropower reservoir in China

Supersaturation and excess emission of greenhouse gases in freshwater reservoirs have received a great deal of attention in recent years. Although impoundment of reservoirs has been shown to contribute to the net emission of greenhouse gases, reservoir age, geographical distribution, submerged soil type and artificial regulation also have a great impact on their emissions. To examine how large scale reservoir operation impact the water column CO₂ and its air–water interface flux, a field study was conducted in 2010 to evaluate potential ecological processes that regulate the partial pressure of CO₂ (pCO₂) in the water column in the Pengxi River backwater area (PBA), a typical tributary in the Three Gorges Reservoir, China. Measurements of total alkalinity (TA), pH and water temperature were applied to compute the pCO₂. And this approach was also validated by calculation of pCO₂ from the dissolved inorganic carbon data of samples. Partial least squares (PLS) regression was used to determine how the dynamics of the water pCO₂ were related to the available variables. The estimated pCO₂ in our sample ranged from 26 to 4,087 μatm in the surface water. During low water operation from July to early September, there was an obvious pCO₂ stratification, and pCO₂ in the surface was almost unsaturated. This phenomenon was also observed in the spring bloom during discharge period. Conversely, there was no significant pCO₂ stratification and the entire water column was supersaturated during high water operation from November to the following February. Significant correlation was observed between the magnitude of pCO₂, DO and chlorophyll a, suggesting that phytoplankton dynamics regulate pCO₂ in the PBA. The average areal rate of CO₂ emissions from the Pengxi River ranged from 18.06 to 48.09 mmol m^?2 day^?1, with an estimated gross CO₂ emission from the water surface of 14–37 t day^?1 in this area in 2010. Photosynthesis and respiration rates by phytoplankton might be the dominant processes that regulated pCO₂ in the water column. We conclude that pCO₂ values in the surface water of Pengxi River could be regarded as potential sources of CO₂ to the atmosphere were smaller or similar to those that have been reported for many other reservoirs to date.     

Perfluorooctane sulfonate (PFOS) distribution and effect factors in the water and sediment of the Yellow River Estuary, China

The distribution of perfluorooctane sulfonate (PFOS) was investigated in a total of 15 water and sediment samples from the Yellow River Estuary, China in April 2011. The results indicated that the concentrations of PFOS in the water and sediment samples averaged 157.5 ng/L and 198.8 ng/g and ranged from 82.30 to 261.8 ng/L and 75.48 to 457.0 ng/g, respectively. The concentrations of PFOS in the sediment column increased from 45.32 to 379.98 ng/g with the decrease of the sampling depth, which showed that the increased PFOS pollution in the sediment appeared in this region in over recent years. The distribution coefficient (K _d) of PFOS between water and sediment linearly increased from 0.37 to 4.80 L/g as the salinity (S‰) increased from 0.18 to 4.47. Correlation analysis revealed that K _d was significantly and positively correlated to the contents of total organic carbon and clay of the sediment, and salinity. Therefore, salinity was an important parameter in controlling the sediment–water interactions and the fate or transport of PFOS in the aquatic environment. The results of this study showed that the estuary was an important sink for PFOS and suggested that PFOS might be carried with the river water and transported for long distances before it reached to the sea and largely scavenged to the sediment in the estuaries due to the change in salinity.     

The Ecological Condition of Veracruz, Mexico Estuaries

During June and July, 2002, forty-seven stations were sampled within estuaries along the gulf coast of the state of Veracruz, MX, using a probabilistic survey design and a common set of response indicators. The objective of the study was to collect information to assess the condition of estuarine waters within the state of Veracruz, and to provide data that would strengthen future assessments of Gulf of Mexico estuaries. Samples for water quality, sediment contaminants, sediment toxicity, and benthic populations were collected in a manner consistent with EPA’s National Coastal Assessment (NCA). Data were evaluated by comparing indicator measurements to tropical waters threshold values cited in US EPA’s National Coastal Condition Report II, 2004, for tropical waters. In Veracruz, 75% of the area sampled rated poor for water quality, attributed primarily to high concentrations reported for chlorophyll a, and dissolved nutrients. One percent of the area exhibited poor sediment quality, based on PAH and metals concentrations. Compared to US estuaries of the Gulf of Mexico, water quality observed in Veracruz estuaries was more affected by nutrient over-enrichment. The probabilitistic nature of the survey design allowed for the comparison of the condition of Veracruz and the US GOM estuaries.     

Agricultural Lakes in Finland: Current Water Quality and Trends

Agriculture is the largest source of nutrients into surface waters in Finland, and yet relatively little is known about the actual impact of the agricultural load on the state of lakes. We analysed the water quality data of 20 Finnish agricultural lakes and found that they had higher levels of nutrients, chlorophyll a and turbidity than did the other types of lakes (e.g. those receiving point-source load) in the national monitoring network (the Finnish Eurowaternet). Currently, six of the agricultural lakes can be classified as eutrophic and 14 as hypertrophic. Trend analysis (based on Kendall's tau-b) indicated that during 1976–2002 the water quality of the lakes either remained constant or showed signs of increasing eutrophication and elevated turbidity. Decreasing nutrient concentrations were found only in one intensively restored lake. In none of the lakes had the chlorophyll a concentration decreased. The results of the trend analysis are compatible with the recent finding that, despite vigorous efforts, the nutrient load from agriculture has not declined in Finland. Recovery of the most eutrophied agricultural lakes would call for a drastic reduction in the external nutrient load, possibly supplemented with in-lake restoration.     

Temporal and spatial variability of phytoplankton monitored by a combination of monitoring buoys,pigment analysis and fast screening microscopy in the Fehmarn Belt Estuary

For 2 years, a baseline investigation was carried out to collect reference information of the present environmental status in the Fehmarn Belt and adjacent area. The temporal and spatial variability of phytoplankton was monitored by a combination of monitoring buoys, pigment analysis and fast screening microscopy. The overall phytoplankton succession in the Fehmarn Belt area was found to be influenced primarily by the seasonal changes, where various diatoms dominated the spring and autumn blooms and flagellates like Chrysochromulina sp., Dictyocha speculum and various dinoflagellates were occasionally abundant in late spring and summer. The phytoplankton groups were remarkably uniform horizontally in the investigation area while large differences in both biomasses and composition of individual phytoplankton groups were seen vertically in the water column, especially in the summer periods, in which the two-layer exchange flow between the North Sea and the Baltic Sea is showing a particularly strong stratification in the Fehmarn Belt. The chlorophyll a concentrations ranged continuously from 1 to 3 μg/L at the three permanent buoy stations during the 2 years of monitoring, except for the spring and autumn blooms where chlorophyll a increased up to 18 μg/L in the spring of 2010 and up to 8 μg/L in the autumn of 2009. Recurrent blooms of filamentous cyanobacteria are common during the summer period in the Baltic Sea and adjacent areas, but excessive blooms of cyanobacteria did not occur in 2009 and 2010 in the Fehmarn Belt area. The combination of the HPLC pigment analysis method and monitoring buoys continuously measuring fluorescence at selected stations with fast screening of samples in the microscope proved advantageous for obtaining information on both the phytoplankton succession and dynamic and, at the same time, getting information on duration and intensity of the blooms as well as specific information on the dominant species present both temporally and spatially in the large Fehmarn Belt area.     

The success of elutriate tests in extended prediction of water quality after a dredging operation under freshwater and saline conditions

Dredging simulation by elutriate tests accurately predicted concentrations of Hg, Cu, Mn and Fe released to the water column from contaminated sediment to within 1 order of magnitude. Hg and Cu concentrations increased by up to 7-fold after dredging, but declined to background concentrations within 48 h. Maximum loadings of Hg and Cu coincided with Fe and total organic carbon (TOC) water column concentrations, suggesting Hg and Cu are adsorbed onto particulates of Fe oxides and organic material. Seasonal changes in redox potential and temperature did not significantly affect metal release from sediments. Saline water did not cause significant increases in contaminant release from sediments to the water column over that observed for freshwater. Water quality standards of 1 µg l^–1 Hg and 28 µg l^–1 Cu as annual averages were not breached by dredging operations. Long-term effects of dredging on Hg and Cu availability, due to deposition of contaminated material as surficial sediments, is, however, of concern.     

Investigating the impacts of treated effluent discharge on coastal water health (Visakhapatnam,SW coast of Bay of Bengal,India)

The present study investigated the impacts of treated effluent discharge on physicochemical and biological properties of coastal waters from three pharmaceuticals situated along the coast of Visakhapatnam (SW Bay of Bengal). Seawater samples were collected (during the months of December 2013, March 2014 and April 2014) from different sampling locations (Chippada (CHP), Tikkavanipalem (TKP) and Nakkapalli (NKP)) at 0- and 30-m depths within 2-km radius (0.5 km = inner, 1 km = middle and 2 km?=?outer sampling circles) from the marine outfall points. Physicochemical and biological parameters, which differed significantly within the stations, were likely to be influenced by strong seasonality rather than local discharge. Dissolved oxygen variability was tightly coupled with both physical and biological processes. Phytoplankton cell density and total chlorophyll (TChla) concentrations were significantly correlated with dissolved inorganic nutrient concentrations. CHP (December) represented a diatom bloom condition where the highest concentrations of diatom cells, total chlorophyll (TChla), dissolved oxygen coupled with lower zooplankton abundance and low nutrient levels were noticed. The centric diatom, Chaetoceros sp. (>?50%) dominated the phytoplankton community. TKP (March) represented a post-diatom bloom phase with the dominance of Pseudo-nitzschia seriata; zooplankton abundance and nutrient concentrations were minimum. Conversely, NKP (April) represented a warm well-stratified heterotrophic period with maximum zooplankton and minimum phytoplankton density. Dinoflagellate abundance increased at this station. Relatively higher water temperature, salinity, inorganic nutrients coupled with very low concentrations of dissolved oxygen, TChla and pH were observed at this station. Copepods dominated the zooplankton communities in all stations and showed their highest abundance in the innermost sampling circles. Treated effluent discharge did not seem to have any significant impact at these discharge points.     

Water and sediment quality in Qinghai Lake,China: a revisit after half a century

Qinghai Lake, situated on the Qinghai–Tibet plateau, is the largest lake in China. In this study, the water and sediment quality were investigated in Qinghai Lake, three sublakes, and five major tributaries. Both Na⁺ and Cl^? were found to be the major ions present in Qinghai Lake and the three sublakes, while Ca²⁺ and HCO^3? dominated the tributaries. Compared with historical data from the 1960s, the concentrations of NH₄ ⁺, NO₃ ^?, and soluble reactive silica have increased considerably, likely caused by increased human activities in the area. Compared to the historical data, chemical oxygen demand has increased and lake water transparency has decreased, likely related to an increase in nutrient levels. Relatively high concentrations of total nitrogen (TN) and total phosphorus (TP) were observed in Qinghai Lake sediments, although P fraction types and low water concentrations of these two indicate low possibility of transfer into the water column. The ratios of C/N suggest that the organic matter in the sediments are primarily from autochthonous sources. TN and total organic carbon in the sediment cores increased slowly up the core while TP and total inorganic carbon have been fairly constant.     

Partition of heavy metals in a tropical river system impacted by municipal waste

A research program was established to identify the governing factors for the partition coefficient (K _D ) of heavy metals between suspended particulate and dissolved phases in the Day River system a tropical, highly alluvial aquatic system, in Vietnam. The targeted river system, draining an urbanized–industrialized catchment where discharged wastewater is mostly untreated, could be separated into the least impacted, pristine area, and the most impacted, polluted area. Organic matter degradation was shown to govern the variation of parameters like total organic carbon, biochemical oxygen demand, chemical oxygen demand, nutrients, conductivity, or redox potential. Heavy metals in both dissolved and particulate phases were enriched in severely polluted area because of wastewater inflow that contains concentrated metals and intensification of metal influx from sediment. Results show log K _D in the order Mn?<?As?<?Zn?<?Hg?<?Ni?<?Cu?<?Cd?<?Co?<?Pb?<?Cr?<?Fe and As?<?Zn?<?Ni?<?Mn?<?Cr?<?Cu?<?Co?<?Fe in the polluted zone and the pristine zone, respectively. A decreasing tendency of partition coefficients of 11 heavy metals considered from the pristine to the impacted zones was observed. Three explanations for the difference are: (1) increase of solubility of most heavy metals in low redox potential, (2) competition for the binding sites with major and minor cations, and (3) complexation with dissolved organic matter concentrated in municipal waste impacted water. Apart from domestic waste impact, statistical analysis has contributed to identify the influence of climate condition and hydrological regime to the partition of heavy metals in the area.     

Diurnal variations in bacterial and viral production in Cochin estuary, India

Microbes play a central role in the decomposition and remineralization of organic matter and recycling of nutrients in aquatic environments. In this study, we examined the influence of physical, chemical, and biological parameters on the rate of bacterial production (BP) and viral production (VP) with respect to primary production over a diurnal period in Cochin estuary. Time series measurements were made every 2 h for 12 h (6 a.m.–6 p.m.) during periods of low and high salinities. The light intensity as photosynthetically active radiation, temperature, salinity, nutrients like NO₃–N, SiO₄–Si, and PO₄–P, and chlorophyll a (Chl a) were measured along with BP, VP, and net primary production (NPP). NPP showed a strong positive correlation with light and Chl a (r ²?=?0.56 and 0.47, respectively), while VP showed a strong positive correlation with light, salinity, and Chl a (r ²?=?0.37, 0.58, and 0.37, respectively) and a negative correlation with BP (r ²?=??0.39) at P?≤?0.05. We observed a diurnal pattern in BP but did not have any significant correlation with light. Similar diurnal pattern was seen in VP, the peak of which was in succession with BP, suggesting that virus-mediated lysis plays an important role in loss processes of bacteria in Cochin estuary. The results of our study highlight the light-dependent and physicochemical-dependent diurnal variation in virioplankton production in a tropical estuarine ecosystem.     

An assessment of water quality and primary productivity in Perdido Bay,a Northern Gulf of Mexico Estuary

Perdido Bay is a shallow estuarine system of approximately 130 km² with three major freshwater inputs. On a seasonal basis the productivity and chlorophyll a concentration of phytoplankton in Perdido Bay are controlled by temperature. One input, Eleven Mile Creek, is influenced by a paper mill discharge. Eleven Mile Creek exhibits high levels of light attenuation, high concentrations of dissolved nutrients, and low rates of carbon fixation that are significantly different from the other inputs or areas of Perdido Bay and productivity in Eleven Mile Creek is light limited. Upper Perdido Bay had slightly elevated concentrations of dissolved nutrients which correlate with significantly higher rates of carbon fixation and phytoplankton biomass. Nutrients and color from Eleven Mile Creck are diluted by the Perdido River inflow, restricting nutrient and light limitations to the area at the mouth of Eleven Mile Creek.     

Assessment of land influence on a high-latitude marine coastal system: Tierra del Fuego, southernmost Argentina

The study deals with the determination of physico-chemical parameters, inorganic nutrients, particulate organic matter, and photosynthetic pigments on a monthly basis during an annual cycle from nine sampling sites of the coastal zone of a high-latitude ecosystem (Tierra del Fuego, Argentina). Nitrites and phosphates concentrations were similar to other systems of the south Atlantic coast (median, 0.30 and 1.02 ??M, respectively), while nitrates were higher in all sampling periods (median, 45.37 ??M), and silicates were significantly smaller (median, 7.76 ??M). Chlorophyll a and phaeopigments have shown median values of 0.38 and 0.85 mg m^???3, respectively, while saturated values of dissolved oxygen were recorded throughout the study. The analysis reflected that nutrient enrichment seems to be linked to an anthropogenic source, the presence of peatlands areas, and a sink of Nothofagus pumilio woods. The area could be characterized in three zones related to (1) high urban influence, (2) natural inputs of freshwater, and (3) mixed inputs coming from moderate urban impacts.