Assessment Of Trophic Status Research Articles

Total volatile solids may aid in trophic state assessment in subtropical reservoirs

Brazilian artificial reservoirs are multi-purpose systems of great importance for the community since they are used for drinking water supply, energy generation and agricultural irrigation. Anthropogenic eutrophication is an environmental problem of special concern because it can restrict water use due to aquatic systems deterioration. Therefore, trophic state prediction is an important tool for the rapid detection of water quality decrease and the identification of priority areas where action is needed. Within this context, the aim of this research was to assess the role of TVS (total volatile solids) in predicting the trophic status of subtropical reservoirs. To achieve this goal, four stations in the Itupararanga Reservoir (São Paulo State, Brazil) were sampled during dry, intermediate and rainy periods to determine total suspended solids concentrations in different depths of the water column, in addition to other variables (e.g. phosphorus, nitrogen, chlorophyll-a). Through a linear regression between TSI (trophic state index) and the TVS concentrations, an equation relating these two variables was generated (R2 = 0.67). New TSI values (named TSIcalc) were calculated and analyzed against the observed ones (TSIobs, determined through the total phosphorus and chlorophyll-a concentrations). The results suggested that TVS may be considered an interesting variable to predict the trophic state of subtropical reservoirs.

Estuarine trophic state assessment: New plankton index based on morphology of Keratella rotifers

A new estuarine trophic state index – Keratella-index (KIN), based on the relative abundance of two common rotifer species, Keratella cochlearis and Keratella tecta, was developed and tested for the Neva Estuary (Gulf of Finland, Baltic Sea). The morphological trait variation of these plankton species and their responses to different trophic conditions were investigated at three nearshore stations. The morphological data confirm that K. cochlearis and K. tecta are likely to be two distinct species (not two morphs) at our study site. The mean lorica length of K. cochlearis and K. tecta differ significantly and there were no K. cochlearis individuals with extremely short spines (<15.9 μm); therefore, variation of this trait was discontinuous. K. cochlearis spine length significantly decreases with an increase in trophic state (R2 = 0.71; p < 0.01) and unspined K. tecta prevailed in more eutrophic conditions. The proposed index (KIN) is calculated as the proportion of K. tecta in the total abundance of rotifers K. cochlearis and K. tecta, the increase of which indicates and increase in estuarine trophic state. The success of unspined K. tecta compared to spined K. cochlearis may be explained by the “rare-enemy effect”. There was a significant correlation (R2 = 0.76; p < 0.001; R2 = 0.68; p < 0.01) between KIN and the common trophic state indices (TSI and QB/T, respectively). The KIN values indicated meso-eutrophic to strongly eutrophic conditions at different nearshore sampling sites and hence indicated that the Neva Estuary is eutrophic.

Effects of environmental factors on nutrients release at sediment-water interface and assessment of trophic status for a typical shallow lake, northwest China.

Surface sediment and water samples were collected from Daihai Lake to study the biogeochemical characteristics of nitrogen and phosphorus, to estimate the loads of these nutrients, and to assess their effects on water quality. The contents and spatial distributions of total phosphorus (TP), total nitrogen (TN), and different nitrogen forms in sediments were analyzed. The results showed that concentrations of TN and TP in surface sediments ranged from 0.27 to 1.78 g/kg and from 558.31 to 891.29 mg/kg, respectively. Ratios of C : N ranged between 8.2 and 12.1, which indicated that nitrogen accumulated came mainly from terrestrial source. Ratios of N : P in all sampling sites were below 10, which indicated that N was the limiting nutrient for algal growth in this lake. Effects of environment factors on the release of nitrogen and phosphorus in lake sediments were also determined; high pH values could encourage the release of nitrogen and phosphorus. Modified Carlson's trophic state index (TSIM) and comprehensive trophic state index (TSIC) were applied to ascertain the trophic classification of the studied lake, and the values of TSIM and TSIC ranged from 53.72 to 70.61 and from 47.73 to 53.67, respectively, which indicated that the Daihai Lake was in the stage of hypereutropher.

Ecological assessment of groundwater trophic status by using artificial substrates to monitor biofilm growth and activity

The European water legislation highlights the necessity of developing ecological criteria for assessing the quality of aquatic ecosystem. While a multitude of ecological indicators has been proposed and validated for streams, rivers and lakes, these indicators are not available for groundwater ecosystems. In the present study, we developed a method based on the measurements of the growth and activity of microorganisms developed on artificial substrates (glass beads) incubated in wells to characterize the trophic status of groundwater. Incubation sites were selected in an urban aquifer where previous works showed contrasting trophic conditions in groundwater due to artificial groundwater recharge practices. Total proteins, total carbohydrates, dehydrogenase and hydrolytic activities were measured on glass beads incubated in wells for two periods of 2 months (October–December 2010 and April–June 2011). Biofilm measured on glass beads was significantly more developed and active in wells where groundwater was enriched with dissolved organic matter due to artificial groundwater recharge. Indeed, most microbial variables (total proteins and dehydrogenase activities for the two incubation periods and hydrolytic activities for the second incubation period) were significantly and positively correlated with the concentrations of dissolved organic carbon (DOC) in groundwater. The availability of phosphorus also tended to influence biofilm growth (assessed by total carbohydrates) when PO43− concentrations were lower than 50μg/l. Overall, our study clearly demonstrated that artificial substrates acting as colonisable area for microorganisms could be used to efficiently monitor nutrient enrichment in aquifers.

Assessment of the trophic status of four coastal lagoons and one estuarine delta, eastern Brazil

Anthropogenic eutrophication of aquatic ecosystems continues to be one of the major environmental issues worldwide and also of Brazil. Over the last five decades, several approaches have been proposed to discern the trophic state and the natural and cultural processes involved in eutrophication, including the multi-parameter Assessment of Estuarine Trophic Status (ASSETS) index model. This study applies ASSETS to four Brazilian lagoons (Mundaú, Manguaba, Guarapina, and Piratininga) and one estuarine delta (Paraíba do Sul River), set along the eastern Brazilian coast. The model combines three indices based on the pressure-state-response (PSR) approach to rank the trophic status and forecast the potential eutrophication of a system, to which a final ASSETS grade is established. The lagoons were classified as being eutrophic and highly susceptible to eutrophication, due primarily to their longer residence times but also their high nutrient input index. ASSETS classified the estuary of the Paraíba do Sul river with a low to moderate trophic state (e.g., largely mesotrophic) and low susceptibility to eutrophication. Its nutrient input index was high, but the natural high dilution and flushing potential driven by river flow mitigated the susceptibility to eutrophication. Eutrophication forecasting provided more favorable trends for the Mundaú and Manguaba lagoons and the Paraíba do Sul estuary, in view of the larger investments in wastewater treatment and remediation plans. The final ASSETS ranking system established the lagoons of Mundaú as "moderate," Manguaba as "bad," Guarapina as "poor," and Piratininga as "bad," whereas the Paraíba do Sul River Estuary was "good."

An algorithm for detecting trophic status (chlorophyll-a), cyanobacterial-dominance, surface scums and floating vegetation in inland and coastal waters

A novel algorithm is presented for detecting trophic status (chlorophyll-a), cyanobacterial blooms, surface scum and floating vegetation in coastal and inland waters using top-of-atmosphere data from the Medium Resolution Imaging Spectrometer (MERIS). The maximum peak-height algorithm (MPH) uses a baseline subtraction procedure to calculate the height of the dominant peak across the red and near-infrared MERIS bands between 664 and 885nm caused by sun-induced chlorophyll fluorescence (SICF) and particulate backscatter. Atmospheric correction of the MERIS TOA reflectance data for gaseous absorption and Rayleigh scattering proved adequate given the spectral proximity of the relevant bands and the sufficiently large differential spectral signal. This avoided the need to correct for atmospheric aerosols, a procedure which is typically prone to large errors in turbid and high-biomass waters. A combination of switching algorithms for estimating chl-a were derived from coincident in situ chl-a and MERIS bottom-of-Rayleigh reflectance measurements. These algorithms are designed to cover a wide trophic range, from oligotrophic/mesotrophic waters (chl-a<20mgm−3), to eutrophic/hypertrophic waters (chl-a>20mgm−3) and surface scums or dry floating algae or vegetation. Cyanobacteria-dominant waters were differentiated from those dominated by eukaryote algal species (dinoflagellates/diatoms) on the basis of the magnitude of the MPH variable. This is supported by evidence that vacuolate cyanobacteria (Microcystis aeruginosa) possess enhanced chl-a specific backscatter which is an important bio-optical distinguishing feature. This enables these phytoplankton groups to be distinguished from space. An algorithm derived from cyanobacteria-dominant waters had a r2 value of 0.58 for chl-a between 33 and 362mgm−3 and an error of 33.7% (N=17). The operational algorithm for eukaryote-dominant algal assemblages gave a coefficient of determination of 0.71 and a mean absolute percentage error of 60% for chl-a in the range 0.5–350mgm−3 (N=48). A flag based on cyanobacteria-specific spectral pigmentation and fluorescence features was used to identify cyanobacterial-dominance in eutrophic waters. Global applications demonstrate how the MPH algorithm can offer rapid and effective assessment of trophic status, cyanobacterial-dominance, surface scums and floating vegetation in inland and coastal waters.

Shifts in taxonomical and guild composition of littoral diatom assemblages along environmental gradients

Diatoms are commonly and frequently used as water quality indicators, but only a few studies have been done to evaluate the importance of littoral, contemporary diatoms as bioindicators. This study aims to determine the main predictors of diatom community composition from 73 Swedish lakes. Canonical correspondence analysis (CCA) revealed pH, phosphate, nitrite/nitrate levels, longitude and percentage of forest in the catchment to be the most important factors of 51 environmental variables for structuring diatom assemblages. Cluster analysis separated the lakes into three groups based on the diatom community composition. Lakes belonging to these groups were characterised as: (1) acidic, nutrient-poor; (2) circumneutral, nutrient-poor and (3) alkaline, nutrient-rich, according to the results of a discriminant function analysis and dominant diatom taxa revealed by similarity percentage analysis. Ecological guilds according to growth morphology and the ability of nitrogen-fixation were assigned to all diatom taxa. All three lake groups exhibited a distinct guild composition. Nitrogen-fixing diatoms were found in nutrient-rich lakes, only. Our results indicate that taxonomical composition of littoral diatom assemblages can be applied in the assessment of nutrient and acidity status of Swedish lakes. Differences in distribution of the ecological guilds were connected to several environmental factors such as nutrients, light and grazing; their application in assessment of trophic status of lakes is therefore precarious.

Eutrophication Assessment in Basque Estuaries: Comparing a North American and a European Method

Eutrophication in marine ecosystems is an important problem that requires an accurate assessment. Although Basque estuaries (northern Spain) have historically been under high anthropogenic pressure, no specific eutrophication assessment method had been applied in these waters. In this study, a method employed in the Basque Country (BC) to assess the “risk of failing to achieve good ecological status” under the requirements of the Water Framework Directive (WFD) was adapted to exclusively assess the risk of eutrophication. This method is based on the driver–pressure–state–impact–response approach. The results from this method (called WFD-BC method) were compared to the results from Assessment of Estuarine Trophic Status (ASSETS; a specific method developed in the US to assess estuarine trophic status in a pressure–state–response approach). The nutrient pressure was better characterized with the WFD-BC method due to the local hydrographic conditions (i.e., small and river-influenced estuaries) that were not well accommodated by the ASSETS method. In contrast, the WFD-BC results for assessment of state generally reflected worse conditions than the results from the ASSETS method due to the different indicators employed and the way these are integrated in the WFD-BC method. Overall, the WFD-BC method showed a good potential to assess eutrophication. However, to improve it, a lower weight for the benthos and macroalgae is recommended for evaluating state.

Eutrophication of Tenkiller Reservoir, Oklahoma, from nonpoint agricultural runoff

Tenkiller Ferry Reservoir, a large (51.6 km2) US midcontinent reservoir in Oklahoma, switched from oligo-mesotrophic prior to 1975 to eutrophic by 1986, evidenced by changes in phytoplankton taxa, chlorophyll (Chl), total phosphorus (TP), transparency, and areal hypolimnetic oxygen deficit. External TP loading increased 2.5-fold between 1974 and 2004, mainly as nonpoint loading from disposal of an annual (2001–2004) average 406,818 metric tons (mt) of untreated poultry litter on watershed pastures, which added an annual (2001–2006) average 4120 mt of TP. Phosphorus runoff from litter, estimated as 5 % of applied, was 63 % of external loading to the Illinois River from 2001– 2004, 71 % after the 2004 waste water treatment plant upgrade. The 9 % load decrease from the upgrade did not affect Chl. Sediment TP release, seldom determined for reservoirs, accounted for 16 % of annual external plus internal TP load. Trophic state graded from riverine to lacustrine zone. In wet summers with low residence times, the lacustrine zone was eutrophic; in dry summers it was mesotrophic. Transition and riverine zones were always eutrophic or hypereutrophic. Trophic state assessment ideally requires multiple sampling years in all reservoir zones. A similar Oklahoma reference reservoir, Broken Bow, with modest watershed poultry activities and low inflow TP concentrations, was oligo-mesotrophic. Rehabilitation of Tenkiller Reservoir requires large reductions of TP loading by ceasing watershed litter disposal, changes in watershed management practices, and application of in-reservoir procedures. [Supplemental materials are available for this article. Go to the publisher's online edition of Lake and Reservoir Management to view the supplemental file.]

Assessment of benthic trophic status of marine coastal ecosystems: Significance of meiofaunal rare taxa

Eutrophication enhances organic C inputs to the sea bottom, so that the quantity and biochemical composition of sedimentary organic matter are expected to change under different trophic status conditions. In turn, changes in the trophic status are often associated with shifts in the abundance and community structure of the benthos. We investigated the quantity and biochemical composition (protein, carbohydrate, lipid and phytopigment) of sedimentary organic matter together with abundance and community structure of meiofauna in two regions of the Mediterranean Sea characterized by different levels of primary productivity. At each region, five transects were randomly selected along the coastline. At each transect, three stations located at increasing distance from the shore and different water depth were investigated. Uni- and multivariate analyses of variance revealed that the quantity and biochemical composition of sediment organic matter displayed the most relevant differences between stations, suggesting their potential use as descriptor of the benthic trophic state at the small spatial scale (i.e. <2 km). The correlation analyses, corroborated by nMDS dispersion plots and cluster analyses highlighted that the biopolymeric C content of the sediment and the algal fraction of sediment organic matter were inversely related and able to discriminate the trophic status at the scale of region, transect and station. Uni- and multivariate analyses on meiofaunal assemblages revealed that differences at different spatial scales were less evident in terms of abundance and richness of meiofaunal taxa but were more evident in terms of taxonomic composition. Furthermore, these differences were enhanced when the analyses were restricted using the meiofaunal rare taxa (i.e. those taxa representing <1% of the total meiofaunal abundance) as an input. The results of the multivariate multiple regression analyses revealed that the taxonomic composition of meiofaunal assemblages was driven mostly by protein, biopolymeric C and chlorophyll-a concentrations but also by the algal fraction of biopolymeric C. We conclude that, the study of the quantity and biochemical composition of sediment organic matter coupled with an analysis of the rare meiofaunal taxa allows an ecosystem-oriented assessment of the trophic status of marine benthic environments.

Environmental heterogeneity analysis, assessment of trophic state and source identification in Chaohu Lake, China

Environmental heterogeneous methods were used for analysing data sets of trophic state with 11 parameters measured at 12 different sites at Chaohu Lake for the period 2004 to 2006. The aim of this research was to determine spatial/temporal variations in water quality, to assess trophic state and to identify pollution sources. Protective measures and schemes were proposed to improve water quality in the lake. Hierarchical cluster analysis (CA) grouped the 12 sampling sites into two clusters (Eastern Chaohu Lake and Western Chaohu Lake). Temporal CA classified the 12 months into four periods (March-May; June-August; September-November; January, February and December) with a distinct regular seasonal cycle in Eastern Chaohu Lake and four periods (January-April and December; May, July and November; June, September and October; August) with an irregular seasonal cycle in Western Chaohu Lake. Trophic state index analysis showed that Eastern Chaohu Lake was in mesotrophic levels, while Western Chaohu Lake was in eutrophic and hypereutrophic levels. Based on pollutant source statistics data, the dominant pollution sources were identified as domestic sewage and non-point pollution in Eastern Chaohu Lake. Domestic sewage, industrial and non-point sources were contributed to eutrophication in Western Chaohu Lake.

Scaling the trophic index (TRIX) in oligotrophic marine environments

The TRIX index used for the assessment of trophic status of coastal waters has been applied in many European seas (Adriatic, Tyrrhenian, Baltic, Black Sea, and North Sea). However, all these waters are characterized by high nutrient levels and phytoplankton biomass; index calibration based on systems that are principally eutrophic may introduce bias to the index scaling. In the present work the TRIX trophic index is evaluated using three standard sets of data characterizing oligotrophy, mesotrophy, and eutrophication in the Aegean (Eastern Mediterranean) marine environment. A natural eutrophication scale based on the TRIX index that is suitable to characterize trophic conditions in oligotrophic Mediterranean water bodies is proposed. This scale was developed into a five-grade water quality classification scheme describing different levels of eutrophication. It is questionable whether this index can form a universal index of eutrophication or the scaling of TRIX should be region specific.

Carlson’s Index, a poor cursor of trophic status assessment of Pulicat Lagoon, southeast coast of India

Pulicat Lagoon is a productive coastal lagoon on the southeast coast of India. Several studies of its physico‐chemical and biological characteristics have been undertaken. This project was the first to attempt to represent the lagoon’s ecological status in the form of a trophic state index. The investigation applied Carlson’s Trophic State Index (TSI) to determine the trophic status of Pulicat lagoon over the years 2005 and 2006. The observations corresponding to the TSI scores for the transparency of the water column (represented by Secchi Disk Depth, an important parameter for calculating TSI) were compared with observations obtained during field sampling. Discrepancies were observed in the representation of the transparency of the water column as well as the trophic condition and those predicted by the TSI. These discrepancies suggested that TSI was not an effective index of the trophic status of Pulicat lagoon. The study thus proves the fallibility of classical indices for a case‐specific scenario. The investigation points out that there is a need to develop newer and more accurate indices to represent water quality in a lagoon.

Austrian Index Macrophytes (AIM-Module 1) for lakes: a Water Framework Directive compliant assessment system for lakes using aquatic macrophytes

We describe a new macrophyte-based assessment tool for Austrian lakes elaborated according to the requirements of the European Water Framework Directive. Data from 38 out of 45, WFD-relevant (≥50 ha) lakes in Austria collected with the help of a new mapping procedure form the basis for a macrophyte-based lake typology and the definition of reference conditions. Module 1 of the Austrian Index Macrophytes (AIM) focuses on the assessment of trophic state and general impairment of lakes. Several metrics were developed and applied in combination with existing indices to classify lakes into five ecological status classes. The metric “vegetation density” focuses on the overall abundance of macrophytes. Since the lower limit of the macrophyte vegetation in lakes is mainly regulated by the water transparency, the metric “vegetation limit” is closely related to the trophic state of the lake. In deep lakes, macrophytes normally form different vegetation zones. As a result of alteration of the shoreline, artificial water level fluctuations or wave action and even eutrophication, specific zones can be missing. The metric “characteristic zonation” helps to check, if all type-specific vegetation zones are present. The metric “trophic indication” uses the Macrophyte Index after Melzer (Hydrobiologia, 395/396: 181–190, 1999). This term indicates the lake trophic state but, in contrast to the metric “vegetation limit”, it tends to show not only the trophic state of the water column but also, in particular, the nutrient conditions in the sediment. With the help of the metric “species composition,” the species spectrum and the species abundances of the current transect are compared with the species composition at reference sites. The similarity of the datasets is measured as Bray–Curtis Distance (Beals, Advances in Ecological Research, 14: 1–55, 1984). The established metrics cover different aspects of macrophyte vegetation and allow analysing the prevailing pressure. Since the different metrics have a different temporal response to eutrophication and reoligotrophication, additional information on the current state of the lake in relation to these processes can be derived. The successful application of AIM-Module 1 is presented for two Austrian lakes and discussed in relation to other assessment tools.

Application of excess carbon dioxide partial pressure (EpCO2) to the assessment of trophic state of surface water in the Red River Delta of Vietnam

For the first time in Vietnam, excess carbon dioxide partial pressure (EpCO2) was used to assess the trophic state of surface waters. Among five methods evaluated, that which takes into account the effect of temperature, salinity and of dissolved organic carbon content was selected, owing to the high temperature fluctuation (about 20°C) during the year, the strong tidal influence causing backwater in the downstream region, and the concentrated organic matter (OM) (up to 34.4 mg C/l in the polluted area). These three variables altogether can lead to a 20% difference in calculated EpCO2. The high EpCO2 values clearly indicated a deterioration of water quality at least as far as 60 km downstream from Hanoi, due largely to the impact of domestic wastewater from the city.

Assessment of fish trophic status and relationships by stable isotope data in the coral reef lagoon of New Caledonia, southwest Pacific

This study examines the trophic status and relationships of coral reef fish in the lagoon of New Caledonia, southwest pacific. The feeding habits of 34 fish species collected at three contrasted sites were first described using a compilation of gut contents observations and data from the literature. The carbon and nitrogen isotope signatures of these fish and of some of their potential ultimate food sources were also determined at each site. Despite some spatial variations in the isotopic signatures of most food sources and fish trophic groups, the overall trophic structures of fish assemblages were similar at the three sites. Stable isotope data were then used to re-assign fish species to trophic groups based on theδ 15 N signatures of fish and their food sources. Herbivorous fish species were clearly distinguished from the other trophic groups by their lower δ 15 N signatures, consistent with an estimated trophic position of ∼2 for all species examined. Scaridae were however characterized by relatively higher δ 13 Ca nd lowerδ 15 N, which is probably linked with the role of detritus in their diet. The estimated trophic positions of planktivorous fish species were consistent with their gut contents-based classification. Conversely, the isotopic signatures of carnivorous and piscivorous fish species largely overlapped, and their estimated trophic positions were much lower than expected. This suggests that these species feed over a broader range of trophic levels and food sources than implied by the gut contents observations, and indicates that their diet is partly omnivorous. Finally, the relationships between body mass and the isotopic signatures of four fish species were significant for at least one isotopic ratio for each species. Since ontogenetic variations and omnivorous diets are difficult to assess with gut contents data only, stable isotopes revealed essential in estimating the actual trophic status and relationships characterizing the fish species under study.

Trophic state assessment based on late summer phytoplankton community structure: a case study for epilimnetic lake water

Abstract Phytoplankton species composition, abundance and biomass were studied in samples taken from the epilimnion of Lake Strzeszyńskie in late August of each year from 2000-2005. The number of phytoplankton species was relatively low, with the greatest species diversity observed in the Chlorophyceae. Total phytoplankton abundance was high, with major contributions by picophytoplanktonic cyanobacteria, which formed aggregations. Total phytoplankton biomass was generally low, with the sum of the 2-5 biomass-dominant species always exceeding 50% of the total phytoplankton biomass. The taxonomic composition of the group of biomass dominants was relatively stable inter-annually. On the basis of phytoplankton biomass and chlorophyll a concentration, Lake Strzeszyńskie can be classified as oligo-mesotrophic and mesotrophic, respectively. Trophic index values calculated on the basis of abundance of phytoplankton indicator taxa were higher than the values based on their biomass, and mean values indicate that the lake is mesotrophic or intermediate between mesotrophic and eutrophic.

A revisitation of TRIX for trophic status assessment in the light of the European Water Framework Directive: Application to Italian coastal waters

The trophic status classification of coastal waters at the European scale requires the availability of harmonised indicators and procedures. The composite trophic status index (TRIX) provides useful metrics for the assessment of the trophic status of coastal waters. It was originally developed for Italian coastal waters and then applied in many European seas (Adriatic, Tyrrhenian, Baltic, Black and Northern seas). The TRIX index does not fulfil the classification procedure suggested by the WFD for two reasons: (a) it is based on an absolute trophic scale without any normalization to type-specific reference conditions; (b) it makes an ex ante aggregation of biological (Chl- a) and physico-chemical (oxygen, nutrients) quality elements, instead of an ex post integration of separate evaluations of biological and subsequent chemical quality elements. A revisitation of the TRIX index in the light of the European Water Framework Directive (WFD, 2000/60/EC) and new TRIX derived tools are presented in this paper. A number of Italian coastal sites were grouped into different types based on a thorough analysis of their hydro-morphological conditions, and type-specific reference sites were selected. Unscaled TRIX values (UNTRIX) for reference and impacted sites have been calculated and two alternative UNTRIX-based classification procedures are discussed. The proposed procedures, to be validated on a broader scale, provide users with simple tools that give an integrated view of nutrient enrichment and its effects on algal biomass (Chl- a) and on oxygen levels. This trophic evaluation along with phytoplankton indicator species and algal blooms contribute to the comprehensive assessment of phytoplankton, one of the biological quality elements in coastal waters.

Assessment of trophic status in Changjiang (Yangtze) River estuary

The integrated methodology for the assessment of estuarine trophic status (ASSETS), which was extended and refined from the United States National Estuarine Eutrophication Assessment (NEEA), is a multi-parameter assessment system and has been widely used in eutrophication assessment in estuarine and coastal waters. The ASSETS was applied to evaluate the trophic status of the Changjiang (Yangtze) River estuary, one of the largest estuaries in the world. The following main results were obtained: (i) The estuarine export potential is "moderate susceptibility" due to the "moderate" dilution potential and "moderate" flushing potential; (ii) The overall human influence (OHI) index classified the impact of nutrients in the system as "high" due to the high level of nutrient discharge by the river which channels anthropogenic impacts in the catchments to the estuarine system; (iii) The overall eutrophic condition (OEC) in the estuary was classified into the "high" category due to frequent occurrence of nuisance and toxic algal blooms in the mixing and seawater zones; (iv) Since the nutrient loadings (e.g., DIN) in the river is expected to continue to increase in the near future following the population increase and rapid economic growth throughout the drainage basin, the nutrient-related symptoms in the estuary are likely to substantially worsen, which leads to the "worsen high" category for the definition of future outlook (DFO). The combinations of the three components (i.e., OHI, OEC, and DFO) lead to an overall grade as "bad" for the trophic status in the Changjiang River estuary.

Assessment of Chlorophyll-a Concentration and Trophic State for Lake Chagan Using Landsat TM and Field Spectral Data

In this study, we present the digital evaluation of Landsat TM data and field spectral measurements for retrieving chlorophyll-a (chl-a) concentration and trophic state index in Lake Chagan of Northeast China. Chl-a concentration of the lake can be estimated from the band ratio (TM4/TM3) and the field spectral data at 670 nm (absorption peak) and at 700 nm (reflectance peak). The results show that the best determination coefficient (R (2)) is 0.67 from the TM data, by which chl-a distribution can be mapped. Based on chl-a determination from laboratory analysis, field spectral and TM data, the modified trophic state index (TSI(M)) was applied to assess the lake's trophic state. With the available data in Lake Chagan, each algorithm demonstrates the similar result for assessing the lake's chl-a and trophic state. Our results indicate that Landsat TM and field spectral data could be used effectively to determine chl-a concentration and evaluate the trophic state of Lake Chagan in the study.