Eutrophication Parameters Research Articles

Lake eutrophication associated with geographic location, lake morphology and climate in China

Lake eutrophication is influenced by both anthropogenic and natural factors. Few studies have examined relationships between eutrophication parameters and natural factors at a large spatial scale. This study explored these relationships using data from 103 lakes across China. Eutrophication parameters including total nitrogen (TN), total phosphorus (TP), TN:TP ratio, chemical oxygen demand (CODMn), chlorophyll-a (Chl-a), Secchi depth (SD), and trophic state index (TSI) were collected for the period 2001–2005. Sixteen natural factors included three of geographic location, five of lake morphology, and eight of climate variables. Pearson correlation analysis showed that TP and TSI were negatively related to elevation, lake depth, and lake volume, and positively related to longitude. All eutrophication parameters, except for CODMn and Chl-a, showed no significant correlation with climate variables. Multiple regression analyses indicated that natural factors together accounted for 13–58% of the variance in eutrophication parameters. When the 103 study lakes were classified into different groups based on longitude and elevation, regression analyses demonstrated that natural factors explained more variance in TN, TP, CODMn, Chl-a, and TSI in western lakes than in eastern lakes. Lake depth, volume, elevation, and mean annual precipitation were the main predictors of eutrophication parameters for different lake groups. Although anthropogenic impacts such as point- and nonpoint-source pollution are considered as the main determinants of lake eutrophication, our results suggest that some natural factors that reflect lake buffer capacity to nutrient inputs can also play important roles in explaining the eutrophication status of Chinese lakes.

Water-Quality Variables Across Sekisei Reef, A Large Reef Complex in Southwestern Japan

Abstract: At Sekisei Reef in southwestern Japan (24° N), coral cover dramatically decreased in the mid-1980s, probably due to a population outbreak of the coral predator Acanthaster planci. Coral communities subsequently recovered well outside the semiclosed lagoon, but recovery has been poor inside it. Hence, water-quality degradation including eutrophication has been a concern inside the lagoon. In addition, temporal variation in eutrophication parameters is common among high-latitude coral reefs, resulting in difficulties in evaluating them. Therefore, to address these issues, we monitored temperature, salinity, turbidity, chlorophyll-a, NO x -N (NO3-N + NO2-N), and NH4-N concentrations year-round across the lagoon at Sekisei Reef. Turbidity and NO x -N concentration increased with increasing wind velocity, suggesting that variation in turbidity and NO x -N concentrations was attributed to resuspension of bottom sediments, and NO x -N release through regeneration processes of micro-organisms from the s...

Effects of Anthropogenic Influences on the Trophic State, Land Uses and Aquatic Vegetation in a Shallow Mediterranean Lake: Implications for Restoration

Lake Pamvotis, NW Greece is a shallow Mediterranean eutrophic lake that has changed drastically over the past 50 years. Strong effects, resulted mainly from anthropogenic causes, in the hydrological regime are shown for this area using long term hydrological data and a GIS system for extracting land cover/use changes. A set of aerial imagery acquired in 1945 through 2002 were used to monitor and assess the spatial and temporal changes in land cover/use, focused mainly on the lake’s surface area and its surrounding ecosystem (Natura 2000 area). The significance of the changes in land cover/use distribution within Pamvotis wetland is further discussed depicting the role of the anthropogenic influence on the fragile ecosystem that resulted in the shrinkage of lake’s habitats extent. The purpose of this analysis was to examine the long-term changes on macrophyte community composition, species occurrence and relative abundance with water quality and water level changes over the past century, using historical data, aerial photos and GIS techniques. The results showed that for the last 25 years annual water level fluctuation ranged from 70 to 159 cm. Water level starts decreasing in mid June and increasing again gradually from November until March–April. Intra annual water level fluctuation seems to be affected by land use for agricultural purpose through intensive irrigation and the summer drought as well. A dramatic decline of the submerged vegetation is apparent mainly attributed to anthropogenic pressures. Regarding the land cover/use changes, the most notable and significant alterations are concerning the urban development around the lake, the disappearance of wet meadows and the extension of reed beds. Finally it seems that water budget data as well as the response of the key eutrophication parameters are affected from both hydrological alterations and point/non-point pollution sources.

Establishing reference conditions for Polish lakes - preliminary results

Abstract Establishing reference conditions is essential for performing ecological status assessments of surface waters according to the EU Water Framework Directive. Ecological status is described as the deviation from undisturbed (reference) conditions. This paper presents the process of establishing preliminary reference values for chlorophyll a, total phosphorus, and Secchi disc readings in different types of Polish lakes. This was done by selecting potential reference lakes and performing statistical analysis of the values of the main eutrophication parameters. The preliminary reference values for total phosphorus, chlorophyll, and Secchi disc depth were defined as 0.033 mgP dm-3, 3.75 μg dm-3, and 3.6 m for stratified lakes, and 0.048 mgP dm-3, 5.80 μg dm-3, and 2.5 m. for polymictic lakes, respectively.

Application and sensitivity testing of a eutrophication assessment method on coastal systems in the United States and European Union

The Assessment of Estuarine Trophic Status (ASSETS) screening model has been extended to allow its application to both estuarine and coastal systems. The model, which combines elements of pressure, state and response, was tested on four systems: Maryland Coastal Bays and Long Island Sound in the United States and The Firth of Clyde (Scotland) and Tagus Estuary (Portugal) in the European Union. The overall scores were: Maryland Coastal Bays: Bad; Firth of Clyde: Poor; Tagus Estuary: Good. Long Island Sound was modelled along a timeline, using 1991 data (score: Bad) and 2002 data (score: Moderate). The improvement registered for Long Island Sound is a consequence of the reduction in nutrient loading, and the ASSETS score changed accordingly. The two main areas where developments are needed are (a) In the definition of type-specific ranges for eutrophication parameters, due to the recognition that natural or pristine conditions may vary widely, and the use of a uniform set of thresholds artificially penalizes some systems and potentially leads to misclassification; (b) In the definition and quantification of measures which will result in an improved state through a change in pressures, as well as in the definition of appropriate metrics through which response may be assessed. One possibility is the use of detailed research models where different response scenarios potentially produce changes in pressure and state. These outputs may be used to drive screening models and analyze the suitability of candidate metrics for evaluating management options.

Eutrophication patterns in an eastern Mediterranean coastal lagoon: Vassova, Delta Nestos, Macedonia, Greece

The results of an intensive monitoring study of main eutrophication parameters in relation to fish farming management, climate and hydrography in the Vassova coastal lagoon (Nestos Delta) are presented. The overall aim is to produce basic knowledge in order to contribute to the management of eutrophication of coastal lagoons at local and national levels. Due to extensive spatiotemporal variability of the measured parameters correlation and regression polynomial analysis was used to identify patterns (p<0.05). Freshwater was the main source of nitrate and phosphate in the lagoon. This finding has justified the reduction of freshwater inflow in the past, which, however, has increased mean salinity to 30 PSU and reduced spatial salinity gradients. Maximum nitrate values in winter coincided with adverse climatic and hydrographic conditions (high precipitation, strong NE to E winds and low tide) and fish farming management that hinder water circulation. Dissolved phosphorus variability indicated the combination of the external (freshwaters) and internal (sediment) P-sources. N/P water values indicated nitrogen being the most important nutrient for primary producers throughout the year, except in winter, when phosphorus was the most important nutrient. Practical measures for improving fish farming practices to decrease “eutrophication risk” during winter are suggested. Existing nutrient data from the Vassova and from other Greek lagoons in comparison were also presented and discussed.

Eutrophication in the Krka estuary

Abstract Changes in longitudinal distribution of eutrophication parameters in brackish and marine layers of a stratified karstic estuary have been investigated from December 1988 until October 1989 on a gradient between a pristine and a moderately polluted area. In the estuary, only marine phytoplankton blooms were found to develop. Near the head of the estuary, blooms develop below the halocline. Marine phytoplankton is fed by nutrients released from the decay of sinking freshwater phytoplankton. Phytoplankton growth is P-limited. Hypoxia near the bottom follows the decay of occasionally large quantities of allochtonous freshwater and of autochthonous marine phytoplankton. In the lower estuary, blooms have been observed to develop in the brackish layer above the halocline due to high salinity in the layer and the existence of a local anthropogenic nutrient input.

Abundance and productivity of bacterioplankton in a eutrophication gradient of Shimoda Bay

Abundance, specific growth rate, and productivity of bacterioplankton were investigated over a year in Shimoda Bay, Japan, with reference to the eutrophication parameters such as dissolved organic carbon (DOC) concentration. The results from six stations in the bay indicated the formation of a eutrophic gradient ranging from eutrophic (at a river mouth) to mesotrophic (at the bay mouth) levels. Both DOC concentration and UV absorbance were found to have good correlations to bacterioplankton abundance and productivity within the eutrophication range of Shimoda Bay.

Regionalization of the Upper Great Lakes with Respect to Surveillance Eutrophication Data

Data on six eutrophication parameters routinely measured on surveillance cruises were used to statistically (P ≥ 0.10) regionalize the Upper Great Lakes, using a zonation technique. Inputs and currents played an important role in defining the aeral extent of the regions produced. Regionalization of North Channel–Georgian Bay and Lake Huron compared favourably to that developed by the International Joint Commission, whereas differences in the number of zones used to characterize Lake Superior resulted.