Assessment Of Trophic Status Research Articles

Assessment of the trophic status in a tropical estuarine system

Estuaries are extremely valuable ecosystems and have been affected by several anthropogenic activities from urban growth and industrial development, such as the release of untreated efuents which decrease water quality. This study aimed to evaluate the seasonal and temporal trophic status variation in the Formoso River Estuarine System (FRES), a tropical estuary. Three campaigns were carried out in each season (rainy and dry), during which surface water was sampled for abiotic parameter analyses. The TRIX index was used for trophic status assessment. For the temporal evaluation, a review of literature addressing the matter in the study area was conducted. Between 2017 and 2018, the TRIX index varied from a mean of 6 ± 0.2 upstream to 5 ± 0.4 downstream during the rainy season, indicating eutrophic conditions throughout most of the FRES extension, especially near the Formoso River, and from 6 ± 1 to 3 ± 0.8 during the dry season. Temporal analyses showed that in 2002 the overall mean TRIX index was 5.72 ± 0.4, decreasing in 2005 and 2014, and followed by an upwards trend. We conclude that the FRES is impacted by the release of untreated efuents such as sewage and fertilizers from the city of Rio Formoso and from various agricultural activities, which are more intense during the rainy season. Nevertheless, over time there were more critical scenarios pertaining to the trophic status. The present diagnosis reinforces the importance of public sanitation policies in estuarine regions and spatial planning instruments for pollution control in fishery areas.

Assessment of Water Quality Based on Trophic Status and Nutrients-Chlorophyll Empirical Models of Different Elevation Reservoirs

Water quality degradation is one of the most pressing environmental challenges in reservoirs around the world and makes the trophic status assessment of reservoirs essential for their restoration and sustainable use. The main aims of this study were to determine the spatial variations in water quality and trophic state of 204 South Korean reservoirs at different altitude levels. The results demonstrated mean total phosphorus (TP), chlorophyll-a (CHL-a), total suspended solids (TSS), organic matter indicators (chemical oxygen demand: COD; total organic carbon: TOC), water temperature (WT), and electrical conductivity (EC) remain consistently higher in the very lowland reservoirs (VLLR) than those in other altitudes, due to sedimentary or alluvial watersheds. The average TP and CHL-a levels in VLLR crossed the limit of the eutrophic water, symptomizing a moderate risk of cyanobacterial blooms. Empirical models were developed to identify critical variables controlling algal biomass and water clarity in reservoirs. The empirical analyses of all reservoir categories illustrated TP as a better predictor of CHL-a (R2 = 0.44, p < 0.01) than TN (R2 = 0.02, p < 0.05) as well as showed strong P-limitation based on TN:TP ratios. The algal productivity of VLLR (R2 = 0.61, p < 0.01) was limited by phosphorus, while highland reservoirs (HLR) were phosphorus (R2 = 0.23, p < 0.03) and light-limited (R2 = 0.31, p < 0.01). However, TSS showed a highly significant influence on water clarity compared to TP and algal CHL-a in all reservoirs. TP and TSS explained 47% and 34% of the variance in non-algal turbidity (NAT) in HLR. In contrast, the TP and TSS variances were 18% and 29% in midland reservoirs (MLR) and 32% and 20% in LLR. The trophic state index (TSI) of selected reservoirs varied between mesotrophic to eutrophic states as per TSI (TP), TSI (CHL-a), and TSI (SD). Mean TSI (CHL-a) indicated all reservoirs as eutrophic. Trophic state index deviation (TSID) assessment also complemented the phosphorus limitation characterized by the blue-green algae (BGA) domination in all reservoirs. Overall, reservoirs at varying altitudes reflect the multiplying impacts of anthropogenic factors on water quality, which can provide valuable insights into reservoir water quality management.

Trophic status assessment of Central Eastern Adriatic Sea using water quality variables and loading capacity concept for estuaries

The temporal and spatial variability of pollution pressures of the coastal waters resulting from river discharges is the main cause of eutrophication along the coastline. This study aims to assess the water quality and trophic state of Kastela Bay and the river Jadro estuary located in the Croatian central Adriatic Sea. The trophic assessment is classified using the composite trophic status index (TRIX), originally developed for Italian coastal waters and modified for the eastern central Adriatic Sea using data series from 2012 to 2019 from 13 stations. The impact coming from the river Jadro estuary is analyzed using the loading capacity concept to examine the exchange flows and loading dynamics of nutrients discharged in the Kastela Bay. The results show that the trophic index is larger within the river Jadro estuary and maintains the increased values in the surface layer throughout Kastela Bay. The presented loading capacity concept, accounting for the exchange flows in transitional waters, may help better understand the trophic dynamics of the receiving waters. The loading capacity is changing with the river flow and daily loads from measurements can be used to assess the pattern of impairment.

Plants, Mosses, Charophytes, Protozoan, and Bacteria Water Quality Indicators for Assessment of Organic Pollution and Trophic Status of Continental Water Bodies

Abstract This paper presents data compilation for indicator species of organic pollution and trophic state of continental waters. Information was collected from research papers, monographs, electronic resources, and our research. Altogether 316 species of higher plants, plants, mosses, charophytes, protozoan, and bacteria from 11 taxonomical phyla are represented with ecological preferences for saprobity indicators with saprobity index (S) and indicators of trophic state. This comprehensive data can be used for the purpose of aquatic ecosystem assessment and monitoring of water quality based on bioindication methods.

Trophic Status of Lake Phewa and Kulekhani Reservoir, Nepal

Eutrophication is one of the growing environmental concerns and is affecting and compromising freshwater bodies across the world making the trophic status assessment of water bodies crucial for their restoration and sustainable use. This paper describes the trophic status of Lake Phewa and Kulekhani Reservoir from Nepal. Sampling was conducted during October 2017 (post-monsoon), April 2018 (Pre-monsoon), July 2018 (Monsoon) and February 2019 (Winter). Trophic State Index (TSI) as given by Carlson (1977) and Trophic State Index Deviation given by Carlson (1991) were estimated to assess trophic status and deviations between the Trophic State Indices. One-way analysis of variance showed significant seasonal variation (p < 0.05) in Secchi depth, total phosphorus (TP), TSI in both the water bodies. Both the water bodies were classified as eutrophic during pre-monsoon and post-monsoon, and hypereutrophic during the monsoon indicating the increased flow of allochthonous inputs from their respective catchments. Non-algal turbidity was found to be the limiting factor for productivity. There is a need for sustainable watershed management in order to reduce the nutrients runoff and accumulation in the water bodies.

Fuzzy logic approach for the assessment of trophic state of water bodies

Eutrophication has emerged as one of the main threats to surface water bodies. The parameters for assessing eutrophication are not generally measured regularly from the lakes of India as part of monitoring programmes and it is necessary to express the trophic status in terms of secondary indicator variables that are included in the routine analysis by the State/Central government. In this paper, the trophic status of Ashtamudi Lake has been studied, considering its international importance and socio-economic relevance. The cause and response variables such as total phosphorus, Secchi disc depth, chlorophyll-a and the secondary indicator variables such as pH, turbidity, DO, EC, Salinity, TDS and BOD were analysed during the pre-monsoon season. The lake was predominantly classified as eutrophic, with some areas coming under a hypereutrophic state. A comparison was made among the five methods of water quality index by the use of secondary indicator variables to identify the appropriate method for simulating trophic status and the WQI based on the logarithmic method considering pH, turbidity, DO and BOD was identified to predict the trophic state very well. Further, the application of numerical strategy such as fuzzy logic was used to determine water quality indexes and trophic status, which can define the quality of a water body as a consequence of the variation of environmental parameters. The developed approach was further validated by using historical data for the years 2013–2015, which were regularly monitored by the Kerala State Pollution Control Board. The trophic state predicted by the approach was found to be in agreement with that estimated using Carlson's method. Thus the developed model, based on secondary indicator parameters that are readily available from government agencies, can be used to assess the trophic state of lakes, thereby assisting policy makers to frame regulations to minimize eutrophication.

Remote Estimation of Trophic State Index for Inland Waters Using Landsat-8 OLI Imagery

Remote monitoring of trophic state for inland waters is a hotspot of water quality studies worldwide. However, the complex optical properties of inland waters limit the potential of algorithms. This research aims to develop an algorithm to estimate the trophic state in inland waters. First, the turbid water index was applied for the determination of optical water types on each pixel, and water bodies are divided into two categories: algae-dominated water (Type I) and turbid water (Type II). The algal biomass index (ABI) was then established based on water classification to derive the trophic state index (TSI) proposed by Carlson (1977). The results showed a considerable precision in Type I water (R2 = 0.62, N = 282) and Type II water (R2 = 0.57, N = 132). The ABI-derived TSI outperformed several band-ratio algorithms and a machine learning method (RMSE = 4.08, MRE = 5.46%, MAE = 3.14, NSE = 0.64). Such a model was employed to generate the trophic state index of 146 lakes (> 10 km2) in eastern China from 2013 to 2020 using Landsat-8 surface reflectance data. The number of hypertrophic and oligotrophic lakes decreased from 45.89% to 21.92% and 4.11% to 1.37%, respectively, while the number of mesotrophic and eutrophic lakes increased from 12.33% to 23.97% and 37.67% to 52.74%. The annual mean TSI for the lakes in the lower reaches of the Yangtze River basin was higher than that in the middle reaches of the Yangtze River and Huai River basin. The retrieval algorithm illustrated the applicability to other sensors with an overall accuracy of 83.27% for moderate-resolution imaging spectroradiometer (MODIS) and 82.92% for Sentinel-3 OLCI sensor, demonstrating the potential for high-frequency observation and large-scale simulation capability. Our study can provide an effective trophic state assessment and support inland water management.

An assessment of the temporal alterations in the trophic status and habitat heterogeneity of the anthropogenically influenced Bhagirathi-Hooghly estuary in reference to phytoplankton community and environmental variables.

The Bhagirathi-Hooghly estuary represents one of the most populated estuaries in the Indian subcontinent with dense settlements along its course. The concomitant high anthropogenic influences and enhancement of nutrient load due to uncontrolled discharges from non-point source in monsoon play important role in habitat variability and consequential changes in the water quality of the estuary. Even though such nutrient loadings are expected to cause significant changes in the ecosystem functioning, a documentation of the habitat heterogeneity has largely remained unavailable from this important yet unmonitored estuary. Thus, the present work aims at assessment of water quality and trophic status of the habitat by application of a combination of abiotic and phytoplankton-specific indices as recommended by different international and national authorities. Results suggest that water quality deteriorated during periods of seasonal precipitation due to enhanced nutrient loadings that culminated in altering the trophic status of habitat. Comparisons with regard to international standards further corroborated the influence of seasonal precipitation on water quality and trophic status of the habitat. Phytoplankton functional groups largely reflected the changing nature of the habitat well, with dominance of those taxa that are more persistent under warm, nutrient replete shallow euphotic depths of the habitat. These findings further suggest that it is essential to regularly monitor the health of this estuarine ecosystem to as to sustain the different life forms that will be essential for the livelihood of people in this area.

Trophic state assessment based on summer phytoplankton community structure and trophic indices: a small tectonic lake in Turkey

Trophic state assessment based on summer phytoplankton community structure and trophic indices: a small tectonic lake in Turkey

Sedimentary organic matter composition from tropical ports with distinct geographic and morpho-hydrodynamic characteristics: Evaluation through multiple biochemical markers

Increasing coastal urbanization and shipping activity-related environmental pollution advocate the importance of assessment of port ecosystems. Fatty acid biomarkers, elemental components, and biopolymers were used to evaluate the composition of sedimentary organic matter and benthic trophic status of Kolkata (freshwater, enclosed docks) and Kandla (seawater, macrotidal) ports of India. The sediment fatty acid composition indicated relatively fresh and energy-rich organic matter of phytoplankton and bacterial origin inside Kolkata port than the outside riverine station and Kandla port. Biopolymeric carbon (BPC), used as an indicator of trophic status, revealed eutrophic condition in Kolkata port with high accumulation of organic matter of autochthonous origin, attributed to poor water flushing and input of anthropogenic wastes. In contrast, Kandla port was meso-oligotrophic, rich in bacteria, and terrestrial plant-derived materials. Such an assessment of ports' trophic status helps to evaluate the health of the ecosystem and in management practices.

“Assessment of Spatiotemporal Water Quality Variations, Impact Analysis and Trophic Status of Big Soda Lake Van, Turkey

The study was conducted in order to assess the spatiotemporal variations of selected water quality parameters, impact analysis, and trophic status on the Edremit shores of Lake Van. Water samples were collected from 10 representative sampling stations taken from the influent, effluent, and from Lake Van itself in order to analyze the physicochemical parameters in both dry and wet seasons. The trophic status of the lake was determined using Carlson trophic state index. Impact analysis was conducted based on the method most commonly used in management strategies related to surface waters in Turkey. The results of the study show that five factors obtained from principal component indicated that the parameters responsible for water quality changes were mostly related to salts and soda, physicochemical parameters, point and diffuse pollutions discharge, and other organic pollutants. In the impact analysis pH, COD (chemical oxygen demand), BOD (biological oxygen demand), and TP (total phosphorus) (except for EC (electrical conductivity)) parameters were found to have medium impact, while DO (dissolved oxygen) and TN (total nitrogen) parameters had no impact. The pH, EC, SO4−2, Cl−, TP, COD, and BOD values measured at 10 sampling stations were considered to be Class IV according to national regulations. The final trophic status of lake, according to the Carlson trophic index, was assessed to be eutrophic. Understanding this variation is important so as to develop new ways to resolve issues of sustainable water management. In addition, it is considered essential to prepare guidelines for the trophic status of Lake Van.

Trophic state assessment using hybrid classification tree-artificial neural network

The trophic state is one of the significant environmental impacts that must be monitored and controlled in any aquatic environment. This phenomenon due to nutrient imbalance in water strengthened with global warming, inhibits the natural system to progress. With eutrophication, the mass of algae in the water surface increases and results to lower dissolved oxygen in the water that is essential for fishes. Numerous limnological and physical features affect the trophic state and thus require extensive analysis to asses it. This paper proposed a model of hybrid classification tree-artificial neural network (CT-ANN) to assess the trophic state based on the selected significant features. The classification tree was used as a multidimensional reduction technique for feature selection, which eliminates eight original features. The remaining predictors having high impacts are chlorophyll-a, phosphorus and Secchi depth. The two-layer ANN with 20 artificial neurons was constructed to assess the trophic state of input features. The neural network was modeled based on the key parameters of learning time, cross-entropy, and regression coefficient. The ANN model used to assess trophic state based on 11 predictors resulted in 81.3% accuracy. The modeled hybrid classification tree-ANN based on 3 predictors resulted to 88.8% accuracy with a cross-entropy performance of 0.096495. Based on the obtained result, the modeled hybrid classification tree-ANN provides higher accuracy in assessing the trophic state of the aquaponic system.

Trophic status assessment of small turbid lakes comparing remote sensing and in situ data: case study at lower Danube floodplain

The aim of the study was to compare in situ and remote sensing data, in order to assess the applicability of satellite images in water quality monitoring of floodplain lakes. Two indicators of trophic status were compared: chlorophyll a and total suspended matter. Two lakes on Lower Danube floodplain were selected: Srebarna and Malak Preslavets. Data were obtained in July and August 2018. Sentinel 2 MSI L1c images were analyzed in SeNtinel Application Platform (SNAP), (v. 6.0). According to in situ data, Srebarna Lake indicated status of eutrophication, while Malak Preslavets experienced hypertrophic conditions. Satellite data indicated eutrophic conditions for both lakes. Comparing the results from in situ and satellite data, chlorophyll a showed higher correlation (r = 0.66) and comparable results. On the other hand, significantly overestimation of suspended matter according to satellite data were found, as well weaker correlation (r = 0.57) between both methods. Remote sensing i.e. Sentinel products are emerging as a powerful tool in environmental observation. Although weather conditions could have significant impact on environmental dynamic especially in floodplain lakes, combining and comparing of different methods could improve the preciseness of the methodology as well as assessment reliability.

Quality Assessment of Some Freshwater Resources Located in Bucharest and Surrounding Areas. III. Case Study: Trophic Status Assessment of Mogosoaia, Herastrau and Pantelimon Lakes

The aim of this paper is the evaluation of the trophic status of three lakes riparian to the Colentina River, namely Mogosoaia, Herastrau, Pantelimon, as Part III of an extended study on evaluation of the freshwater resources quality in Bucharest and surrounding areas [1, 2], supplementing the general quality assessment based on indices and indexes presented in Part I with a more in depth analysis of nutrient speciation and partitioning between water and upper sedimentary layers. Water and sediment samples were taken from the inlet and outlet areas of each lake in two sampling campaigns in July 2016 and September 2016. Some of the nutrient related water quality parameters presented in Part I of this series have been used here, together with the analysis of total nitrogen and total phosphorus content in sediments, to assess the general trophic state of the lakes and to highlight the relationships between the nitrogen and the phosphorus content from water and sediments.The studied lakes were found to be eutrophic, Mogosoaia and Pantelimon being in the most advanced state. A significant amount of nitrogen and phosphorus was detected in all sediments analysed, constituting a high accumulation of nutrients from anthropogenic activities. Actions to improve local sanitation infrastructure and to prevent anaerobic leakage of nutrients from sedimentary deposits are recommended.

Quality Assessment of Some Freshwater Resources Located in Bucharest and Surrounding Areas. III. Case Study: Trophic Status Assessment of Mogosoaia, Herastrau and Pantelimon Lakes

The aim of this paper is the evaluation of the trophic status of three lakes riparian to the Colentina River, namely Mogosoaia, Herastrau, Pantelimon, as Part III of an extended study on evaluation of the freshwater resources quality in Bucharest and surrounding areas [1, 2], supplementing the general quality assessment based on indices and indexes presented in Part I with a more in depth analysis of nutrient speciation and partitioning between water and upper sedimentary layers. Water and sediment samples were taken from the inlet and outlet areas of each lake in two sampling campaigns in July 2016 and September 2016. Some of the nutrient related water quality parameters presented in Part I of this series have been used here, together with the analysis of total nitrogen and total phosphorus content in sediments, to assess the general trophic state of the lakes and to highlight the relationships between the nitrogen and the phosphorus content from water and sediments.The studied lakes were found to be eutrophic, Mogosoaia and Pantelimon being in the most advanced state. A significant amount of nitrogen and phosphorus was detected in all sediments analysed, constituting a high accumulation of nutrients from anthropogenic activities. Actions to improve local sanitation infrastructure and to prevent anaerobic leakage of nutrients from sedimentary deposits are recommended.

Compound eutrophication index: An integrated approach for assessing ecological risk and identifying the critical element controlling harmful algal blooms in coastal seas.

Current ecological risk assessment and controlling element identification methods of harmful algal blooms (HABs) are not connected. Here, we identified the controlling elements by correlation and principal component analyses, and the analytic hierarchy process. A compound eutrophication index (CEI) integrating risk assessment with controlling element identification was constructed and verified using data collected from Jiaozhou Bay, China. The CEI results agreed with the chlorophyll-a concentration and the main eutrophication assessment results. The HAB risk assessment of the CEI was more efficient than that of the nutrient quality index and Assessment of Estuarine Trophic Status. The contribution ratio of the loads and concentrations of nutrients (nitrogen, phosphorus, and chemical oxygen demand) to HABs in Jiaozhou Bay was 70%. In the high-risk areas, the contribution ratio of nutrients to HABs was 77%. Therefore, terrestrial nutrient inputs must be reduced to prevent and control HABs in the north-eastern areas of Jiaozhou Bay.

Potentially toxic elements and biochemical components in surface sediments of NW Mexico: An assessment of contamination and trophic status

Abstract Concentrations of Potentially Toxic Elements (PTEs) were determined in sediments from Santa Maria La Reforma (SAMARE) coastal lagoon and Mocorito River, Mexico. Furthermore, biochemical composition of organic matter in sediments was analyzed to assess their trophic status. The PTEs concentrations followed the order Fe > Pb ∼ Zn > Cr ∼ Cu > Ni ∼ As ∼ Co > Cd. Except for As, PTEs showed correlation between them indicating a common source. As and Pb were above the threshold levels of toxic effect, but they did not exceed the levels of probable effect for biota. Metals were correlated with carbohydrates and As with lipids. Low protein/carbohydrate ratios suggest that decomposed detritus of nitrogen-rich algae as well as fresh mangrove litter can be present. These biochemical proxies suggest that meso-oligotrophic conditions prevail in SAMARE. Considering that fishing activities are practiced and that the northern portion of SAMARE was classified as a RAMSAR site, the information presented is useful to generate strategies for the management of this ecosystem.

Characterization of CDOM in reservoirs and its linkage to trophic status assessment across China using spectroscopic analysis

Chromophoric dissolved organic matter (CDOM) represents the optically active component of the DOM pool, and originates from both allochthonous and autochthonous sources. The fluorescent characteristics of dissolved organic matter (FDOM) has been widely used to trace CDOM sources and infer its composition. However, little is known about the optical and fluorescent properties of CDOM in drinking water reservoirs, and the variability of CDOM properties along trophic gradients in these aquatic systems. A total of 536 water samples were collected between 2015 and 2017 from 131 reservoirs across China to characterize CDOM and FDOM properties using both light absorption and fluorescence spectroscopies, and examine relationships with water-quality condition as expressed by the modified trophic state index (TSIM) of the reservoirs (range: 12 < TSIM < 78). With increased reservoir trophic status, CDOM absorption coefficients at 254 nm (aCDOM(254)) and total fluorescence of FRI-EEMs (excitation-emission matrix coupled with fluorescence regional integration) increased significantly (p < 0.01). Our results indicated that the nutrients in aquatic systems and the social economy factors (including wastewater, sewage, cultivated land, GDP, population) and altitude affect the CDOM absorption and fluorescence significantly (p < 0.05). Most importantly, we proposed a new classification standard associated with eutrophic status via CDOM humification index (HIX) due to the significant correlation between each other (p < 0.01). HIX less than 4 was corresponding to TSIM less than 30 as oligotrophic states; 4 < HIX ≤ 12 was corresponding to TSIM less than 50 as mesotrophic states; 12 < HIX ≤ 18 was corresponding to TSIM less than 70 as eutrophic states; HIX more than 18 is defined as hypereutrophic status with TSIM > 70. This method highlights the importance of CDOM fluorescence for aquatic DOM input and strengthens the linkage between the trophic status index and CDOM characteristics, it also contributes to establish a new rapid assessing model with quick experimental measurements to monitor the trophic status of water reservoirs.

Assessment of seasonal trophic state of tropical man-made lake, The Cirata Reservoir

Evaluation of 4-year data set (2013-2016) to define the trophic state of Cirata Reservoir among the seasons and its impact on the reservoir sustainability has been performed. Cirata is one of the cascade reservoirs located on the Citarum River, with the main purpose for electricity generation through a hydropower plant. Data were obtained from eleven sampling stations of monitoring programs in the Cirata Reservoir. The technique for water sample collection and analysis referred to SNI (Indonesian National Standard) 03-7016-2004 and standard method focussing on phosphate, Chlorophyll-a and transparency. This study indicated that the trophic condition of Cirata Reservoir, as a tropical man-made, was unique and dynamic compared to lakes in the temperate season. The results showed that the reservoir water in the last four years was already eutrophic whether in rainy, intermediate or dry seasons with Trophic State Index were 60.42; 59.00 and 57.32 respectively. This study showed that the inlet and centre area of the reservoir had a higher trophic index than the outlet area. This phenomenon indicated that the main sources of eutrophication in Cirata Reservoir came from both the catchment area of the reservoir (i.e. upper Citarum) and on-site the reservoir. Phosphate has been established as the nutrient that commonly limits the productivity in Cirata reservoir. Thereby, phosphate control is critical for the eutrophication mitigation in Cirata. To cope with this condition, strategies must be applied whether to control the phosphate utilization in the catchment or inside the reservoir area.

Color, chlorophyll a, and suspended solids effects on Secchi depth in lakes: implications for trophic state assessment.

Secchi depth (SD), a primary metric to assess trophic state, is controlled in many lakes by algal densities, measured as chlorophyll-a (chl-a) concentration. Two other optically related water quality variables also directly affect SD: non-algal suspended solids (SSNA ) and colored dissolved organic matter (CDOM, expressed as the absorption coefficient at 440nm, a440 ). Using a database of ~1,460 samples from ~625 inland lake basins in Minnesota and two other Upper Midwest states, Wisconsin and Michigan, we analyzed relationships among these variables, with special focus on CDOM levels that influence SD values and the Minnesota SD standards used to assess eutrophication impairment of lakes. Log-transformed chl-a, total suspended solids (TSS), and SD were strongly correlated with each other; log(a440 ) had major effects on log(SD) but was only weakly correlated with log(chl-a) and log(TSS). Multiple regression models for log(SD) and 1/SD based on the three driving variables (chl-a, SSNA , and CDOM) explained ~80% of the variance in SD in the whole data set, but substantial differences in the form of the best-fit relationships were found between major ecoregions. High chl-a concentrations (> 50μg/L) and TSS (> 20mg/L) rarely occurred in lakes with high CDOM (a440 >~4m-1 ), and all lakes with a440 >8m-1 had SD≤2.0m despite low chl-a values (<10μg/L) in most lakes. Further statistical analyses revealed that CDOM has significant effects on SD at a440 values > ~ 4m-1 . Thus, SD is not an accurate trophic state metric in moderately to highly colored lakes, and Minnesota's 2-m SD criterion should not be the sole metric to assess eutrophication impairment in warm/cool-water lakes of the Northern Lakes and Forest ecoregion. More generally, trophic state assessments using SD in regions with large landscape sources of CDOM need to account for effects of CDOM on SD.