Strong Eutrophication Research Articles

Large shallow lake response to anthropogenic stressors and climate change: Missing macroinvertebrate recovery after oligotrophication (Lake Balaton, East-Central Europe)

East-Central Europe's largest shallow lake, Balaton, experienced strong eutrophication in the 1970–80s, followed by water quality improvement and oligotrophication by 2010 CE. Recently however, repeated cyanobacterial blooms occurred and warned that internal P-recycling can act similarly to external P load, therefore we need a better understanding of past water level (WL) and trophic changes in the lake. In this study we discuss the last 500-yr trophic, WL and habitat changes of the lake using paleoecological (chironomids, pollen) and geochemical (sediment chlorophyll, TOC, TS, TN, C/H ratio, major and trace element) methods. We demonstrate that the most intensive and irreversible change in the macroinvertebrate fauna occurred during the period of economic boom between the First and Second World War (∼1925–1940 CE), when large-scale built-in and leisure use of the lake has intensified. At that time, the Procladius-Microchironomus-Stempellina dominated community transformed to Procladius-Chironomus plumosus-type-Microchironomus community that coincided with land use changes, intensified erosion and water-level regulation in the lake with the maintenance of year-round high WL. This was followed by the impoverishment and population size decrease of the chironomid fauna and Procladius dominance since 1940 CE, without any recovery after 1994 CE despite the ongoing oligotrophication. Accelerated rate of change and turnover of the fauna was connected to an increase in the benthivorous fish biomass and eutrophication. The basin lost almost completely its once characteristic Stempellina species between 1927 and 1940 CE due to trophic level increase and seasonal anoxia in the Szemes Basin. Reference conditions for ecosystem improvement were assigned to 1740–1900 CE. We conclude that in spite of the ongoing oligotrophication, the re-establishment of the Procladius-Microchironomus-Stempellina assemblage is hampered, and requires fish population regulation.

Environmental Parameters Related to Hypoxia Development and Persistence in Jinhae Bay from 2011 to 2016 and Their Potential for Hypoxia Prediction

Jinhae Bay, a semi-enclosed bay on the southern coast of Korea, is a major aquaculture area that forms a spawning ground and nursery for commercially important fishes. Since the late 1960s, industrial and domestic waste from adjacent cities and industrial complexes has been released into the region, resulting in chronic hypoxia and red tides. As a central site of environmental monitoring efforts for aquaculture and fisheries in southeastern Korea, Jinhae Bay was surveyed every 2 months usually, and every 2–3 weeks during the hypoxia season, with the seawater properties observed at approximately 31–34 stations. The maximum area and duration of hypoxia in Jinhae Bay occurred in 2016 (316 km2 and 26 weeks, respectively), with minima of area in 2013 (213 km2) and duration in 2011 (15 weeks). Correlation analyses of the seawater properties, weather parameters, and hypoxia indices showed that the hypoxic area was positively correlated with the surface-water temperature, air temperature, and rainfall; the minimum dissolved oxygen concentrations were negatively correlated with the air and water temperatures and bottom-water nutrient levels; and the water stability was negatively correlated with the surface-water salinity and positively correlated with both the surface- and bottom-water nitrate and silicate concentrations. These findings imply that the air temperature and precipitation may be important factors in the development and persistence of hypoxia in Jinhae Bay via the control of the stratification intensity and eutrophication of the water column. Therefore, we tested these parameters for their potential to predict hypoxia. Based on our results, we propose the following trends of hypoxia in Jinhae Bay: the initial hypoxia development generally depends on the criteria of an air temperature ≥ 19.5 °C for 1 week and total precipitation > 100 mm over 4 weeks, and it becomes more severe (≥50% coverage) under strong eutrophication, mainly due to organic matter discharge following heavy rainfall, based on the logarithmic correlation with the 4-week rainfall (R2 = 0.6). Therefore, the hypoxic area index can be predicted using its linear regression relationships with the 1-week air temperature and 4-week precipitation (R2 = 0.56). This study tested the prediction of the hypoxic area based on a simple calculation method and weather parameter criteria, and it demonstrated the potential of this method for precisely forecasting hypoxia in combination with biogeochemical models or other mathematical solutions to prevent massive fishery damage.

Eutrophication increases the similarity of cyanobacterial community features in lakes and reservoirs

Eutrophication of inland waters is a mostly anthropogenic phenomenon impacting aquatic biodiversity worldwide, and might change biotic community structure and ecosystem functions. However, little is known about the patterns of cyanobacterial community variations and changes both on alpha and beta diversity levels in response to eutrophication. Here, we investigated cyanobacterial communities sampled at 140 sites from 59 lakes and reservoirs along a strong eutrophication gradient in eastern China through using CPC-IGS and 16S rRNA gene amplicon sequencing. We found that taxonomic diversity increased, but phylogenetic diversity decreased significantly along the eutrophication gradient. Both niche width and niche overlap of cyanobacteria significantly decreased from low- to high-nutrient waterbodies. Cyanobacterial community distance-decay relationship became weaker from mesotrophic to hypereutrophic waterbodies, while ecological uniqueness (i.e., local contributions to beta diversity) tended to increase in high-nutrient waterbodies. Latitude and longitude were more important in shaping cyanobacterial community structure than other environmental variables. These findings suggest that eutrophication affects alpha and beta diversity of cyanobacterial communities, leading to increasingly similar community structures in lakes and reservoirs with a higher level of eutrophication. Our work highlights how cyanobacterial communities respond to anthropogenic eutrophication and calls for an urgent need to develop conservation and management strategies to control lake eutrophication and protect freshwater biodiversity.

Functional diversity and redundancy of rotifer communities affected synergistically by top-down and bottom-up effects in tropical urban reservoirs

Rotifers are one of the most important functional groups in lentic freshwaters, and mainly structured by predation or competition from crustaceans and food availability from phytoplankton. Their functional traits involving in defense and food utilization provides insights into the functional diversity and assembly of their communities. Tropical urban reservoirs are commonly subjected to intense fish culture and strong eutrophication, and rotifers become the dominant component of the zooplankton communities and play an important role in ecosystem functioning. Knowledge about the functional diversity and functional redundancy of rotifers is therefore of relevance for effective ecosystem management. In tropical reservoirs, we hypothesized that functional diversity and redundancy of rotifer communities are synergistically affected by top-down and bottom-up effects, and that they strongly change seasonally with environmental conditions at local scale as well as with connectivity between reservoirs at regional scale. To test these hypotheses, we investigated the seasonal dynamics of taxonomic and functional diversities in twenty-five tropical urban reservoirs. Traits of rotifers mainly associated with body size, feeding behavior, and defensive strategies were used to explore the drivers of functional diversity and functional redundancy. We found that, at the local scale, both taxonomic alpha and functional alpha diversities of rotifers increased from the wet to the dry season, whereas the functional alpha redundancy showed no significant change. Crustacean abundance (top-down effect) and phytoplankton biomass (bottom-up effect) were the dominant variables explaining the variation of taxonomic and functional alpha diversities. At the regional scale, both the taxonomic and the functional beta diversities of rotifer communities decreased from the wet to the dry season. However, functional beta redundancy increased, accompanied by a reduction in environmental distance, i.e., biological and physicochemical distance. Thus, weakened environmental heterogeneity and strengthened homogenization of biological selection resulted in a more similar functional trait composition than a more similar taxonomic composition between reservoirs.

Spatio-temporal Dynamics of the Aquatic Plant Colonisation of Lake Dang in the Sudano-Guinean Zone (Adamaoua-Cameroon)

Very little information exist on lake environment in Northern Cameroon. The objective of this study is to determine the colonisation plant of Lake Dang using field and remote sensing data from LM, Landsat5, Landsat7 and Landsat8 images, over a 45-year period (1975-2020), spaced 15 years apart (1975; 1990; 2005; 2020). The method of diachronic analysis of satellite data was used and the supervised classification approach based on colour compositions and bands were chosen for class discrimination. The overall accuracies obtained ranged from 96.35 to 89.28%, followed by Kappa indices of 74.43 to 90.18% for the years 1975 and 2020 respectively. The results on the spatio-temporal dynamics of water bodies from 1975 to 2020 show an average annual rate of regression of the water surface of -1.35%/year, i.e. 0.099 km2/year, in favour of vegetation. The period from 1987 to 2002 shows a more marked evolution, with a rate of plant colonisation of 1.98%/year, i.e. 0.145 km2/year, compared to the periods from 1975 to 1990 (rate of plant colonisation of 0.85%/year, i.e. 0.062 km2/year) and 2005-2020 (1.23%/year, i.e. 0.090 km2/year). Today, 73% (5.376 km2) of the total surface area (7.365 km2) of the water body is colonised by vegetation. Moreover, bathymetry shows a maximum depth of 2.70 to 2.80 m, which is discriminating for a lake ecosystem in the Sudano-Guinean zone. Consequently, the preliminary results of this study shows that Lake Dang is marked by a strong eutrophication due to anthropic activities caused by agriculture, urbanization and non-rational deforestation which have strongly affected the occupation of the lake banks.

Can Zn isotopes in sediments record past eutrophication of freshwater lakes? A pilot study at Lake Baldegg (Switzerland)

In this study, the speciation and isotopic composition of Zn were traced across the sediments of a freshwater lake that experienced one hundred years of strong eutrophication, in order to assess the potential of sedimentary Zn isotopes to record such an environmental disturbance. The results indicate that the sedimentary Zn isotope signal varied with the change from pre-eutrophic to eutrophic conditions in the investigated lake. The average δ66ZnJMC value of the dominantly allochthonous lithogenic sediments deposited during the pre-eutrophic period was +0.27‰ ±0.05‰ (i.e. similar to the δ66ZnJMC value of +0.28‰ ±0.05‰ proposed for Bulk Silicate Earth), while enhanced autochthonous biochemical sedimentation during the eutrophic period resulted in significantly lower δ66ZnJMC values down to +0.04‰ ±0.06‰. Synchrotron-based X-ray absorption spectroscopy data revealed a concomitant change in Zn speciation from a dominant fraction of Zn in clay minerals during the pre-eutrophic period to a major fraction of Zn in ZnS during the eutrophic period. A linear regression relating the sedimentary Zn isotope signal to the fraction of Zn in ZnS indicated δ66ZnJMC values of +0.27‰ ±0.06‰ and 0.00‰ ±0.08‰ for Zn in clay minerals and in ZnS, respectively. The enrichment of light Zn in ZnS in the eutrophic sediments is tentatively attributed to enhanced biological uptake of light Zn in the water column, which resulted in an enhanced flux of organic-bound Zn towards the sediments and further transformation of organic Zn into ZnS upon biomass mineralization during early diagenesis. This hypothesis is in agreement with the fractionation towards lighter Zn reported for both biological uptake of Zn and ZnS precipitation. The results of this study emphasize the potential of sedimentary Zn isotopes to register past eutrophic periods in freshwater lakes, and thus to serve as a probe of paleo-environmental conditions and/or past land use at the catchment scale.

Phosphorus spatial distribution and mass balance in the Itaipu lagoon (Rio de Janeiro, Brazil)

The degradation of tropical coastal lagoon systems in urban areas of the least developed countries has been associated with an increase in impermeable areas and poor domestic sewage treatment, increasing land-based runoff of nutrients and suspended solids from catchments. This study aimed to assess the biogeochemical changes caused by human interventions through the analysis of the spatial distribution of sedimentary phosphorus (P) and its mass balance in the Itaipu lagoon, located on the east coast of the state of Rio de Janeiro. Human intervention in the Itaipu lagoon system has caused severe imbalances in biogeochemical cycles over the past decades. Watercourses have been channeled to normalize the hydrological regime and increase hydraulic energy, improving sediment transport capacity. In this context, the increase in runoff from the coastal urban basin into the Itaipu lagoon has buried an increasing amount of phosphorus in the sediment. Recently, a regional increase in storm events caused a series of landslides and floods, which have been reported as possible consequences of global climate change. In recent decades, the synergy between landslides and river channeling has increased TP loads, accelerating phosphorus settling and changing P spatial distribution in surface sediments. This has accelerated siltation of the lagoon with an accumulation of nutrients and organic matter, leading in some cases to sediment anoxia. The lagoon has undergone strong eutrophication, changing its trophic state from meso- to hypertrophic in less than 30 years, even though P loads are not as high as in other coastal lagoons. Our findings confirm that human intervention impacts nutrient loads, which in turn disrupt the balance of biogeochemical cycles, compromising coastal water resources. This leads to the collapse of ecosystem services, another step towards degrading planetary boundaries.

Responses of multiple facets of macroinvertebrate alpha diversity to eutrophication in floodplain lakes

The accelerated eutrophication of freshwater lakes has become an environmental problem worldwide. Increasing numbers of studies highlight the need to incorporate functional and phylogenetic information of species into bioassessment programms, but it is still poorly understood how eutrophication affects multiple diversity facets of freshwater communities. Here, we assessed the responses of taxonomic, phylogenetic and functional diversity of benthic macroinvertebrates to water eutrophication in 33 lakes in the Yangtze River floodplain in China. Our results showed that macroinvertebrate assemblage structure was significantly different among four lake groups (river-connected, macrophyte-dominated, macrophyte-algae transition, and algae-dominated). Three taxonomic, two phylogenetic and two functional diversity indices were significantly different among the lake groups. Except for the increasing trend of Lambda+, these metrics showed a clear decreasing trend with increasing levels of eutrophication, with highest values detected in river-connected and macrophyte-dominated lakes, followed by macrophyte-algae transition lakes and algal-dominated lakes. Although differing in the number and identity of key environmental and spatial variables among the explanatory models of different diversity indices, environmental factors (eutrophication-related water quality variables) played more important role than spatial factors in structuring all three facets of alpha diversity. The predominant role of environmental filtering can be attributed to the strong eutrophication gradient across the studied lakes. Among the three diversity facets, functional diversity indices performed best in portraying anthropogenic disturbances, with variations in these indices being solely explained by environmental factors. Spatial factors were mostly weak or negligible in accounting for the variation in functional diversity indices, implying that trait-based indices are robust in portraying anthropogenic eutrophication in floodplain lakes. However, variation in some taxonomic and phylogenetic diversity indices were also affected by spatial factors, indicating that conservation practitioners and environmental managers should use these metrics with caution when providing solutions for addressing eutrophication in floodplain lakes.

Multiproxy analysis of paleoenvironmental, paleoclimatic and paleoceanographic changes during the early Danian in the Caravaca section (Spain)

After the Chicxulub impact and mass extinction at the Cretaceous-Paleogene boundary (K-PgB), ecosystems haltingly recovered under unstable conditions. An early Danian (65.9 Ma) perturbation of the carbon cycle known as Dan-C2, which includes two carbon isotopic excursions (CIEs), has been ascribed to inputs of greenhouse gases through large-scale volcanism of the Deccan Traps. However, the relationship between Dan-C2, volcanism and environmental and climatic changes during the early Danian remains ambiguous. Based on stable isotopes, calcium carbonate content, magnetic susceptibility and planktic foraminifera, we present a paleoenvironmental, paleoclimatic and paleoceanographic reconstruction of the early Danian from the Caravaca section, Spain, one of the most complete and continuous K-PgB sections worldwide. The paleobiological response of planktic foraminifera suggests very volatile environmental conditions during the first 230 kyr of the Danian, as reflected in the rapid succession of opportunistic/generalist blooms and episodic high occurrences of aberrant specimens. According to our age model, the Dan-C2 has been identified at the Caravaca section from 65.92 to 65.74 Ma. No evidence of strong carbonate dissolution through ocean acidification was observed in the Dan-C2 interval or the rest of the studied section, excluding the K-PgB clay bed. We find that blooms of highly eutrophic Chiloguembelitria and increases in aberrant planktic foraminifera coincided with a major early Danian eruptive episode of Deccan Traps (Ambelani Formation), occurring before the Dan-C2. Conversely, during both Dan-C2 CIEs, less opportunistic taxa thrived, indicating changes in the upper part of the water column. This study demonstrates that the relationship between marine biota and climate change was very complex and rapidly changing during the early Danian. In addition, we propose that the Deccan volcanism had adverse effects on marine plankton, mostly through strong eutrophication, while an increased water column stratification during the Dan-C2 event resulted in a transient boost in the recovery of ecosystems.

Eutrophication Induction Via N/P and P/N Ratios Under Controlled Conditions\u2014Effects of Temperature and Water Sources

The current research outlines the course of eutrophication processes emerging when some critical physical and chemical factors interact altogether. For this purpose, investigations were carried out, where nitrogen [N as (NH4)2HPO4 and KNO3] and phosphorus [P as (NH4)2HPO4] were added to three different water sources (double distilled water, DDW; tap water, TW; and lacustrine water, LW) and the solutions were incubated at two distinct temperatures (17 and 23 °C). Treatments were kept in 1 dm3 glass jars and the incubation time lasted 7 weeks. The eutrophication process emerged only at 23 °C and was stronger for the lacustrine water (LW). In the case of DDW treatments, this process was observed at N/P = 5.1 and even at 60.0, whereas for the TW, no algal blooming was detected (N/P ratio 17.7–640.0). The lacustrine water (LW) outlined patterns with strong eutrophication at N/P = 4.40, but also at ratios 20.9–71.1. Algal blooming significantly intensified according to LW > TW > DDW but was reversely dependent on the P/N ratios, which followed the range DDW (P/N, 1.6–3.78) > TW (P/N, 0.050–0.100) > LW (P/N, 0.016–0.023). At P = constant (P = 0.10 mg dm−3) and the N inputs varying from 0.010 to 2.0 mg dm−3, it appeared that the higher the N concentrations, the more intensive the eutrophication process. For N/P ratios, phosphorus regulated for most of the intensity of the process, whereas in the case of P/N, the role of N and P was interchangeable. The main finding of the research is that nitrogen revealed in many cases to be a powerful eutrophication-regulating factor than did phosphorus.

Paleoclimate reconstruction and mire development in the Eastern Great Hungarian Plain for the last 20,000 years

We present the reconstruction of mire vegetation changes and fire history recorded in a continuous sediment profile that spans the last 20,000 cal yr BP from the Late Pleniglacial to Holocene in North-eastern Hungary. We also aimed to reveal past climate changes by using ecological requirements of specific aquatic plants as summer temperature indicators. Our results suggest the formation of a mesotrophic mire around 20,000 cal yr BP with brown moss, Betula sp. and Selaginella selaginoides cover beside the occurrence of Phragmites australis, Typha latifolia and T. angustifolia suggesting base-rich fen and tundra-like wet-ground habitats on the lakeshore. This community shifted to reed dominated swamp at c. 18,300 cal yr BP with inferred min. July temperatures of 12–15.7 °C. pinus sp., Betula nana, B. pendula/pubescens, Hippuris vulgaris and P. australis dominated until 16,600 cal yr BP pointing to shallow muddy stagnant water and colder climatic conditions than in the preceding interval. The most warmth-demanding species, T. latifolia and T. angustifolia indicated July mean temperatures >14–15.7 °C soon after the LGM. The formation of biogenic carbonate also started at an early stage; major accumulation occurred between 15,200 and 10,000 cal yr BP. In the Early Holocene, environmental indicator species (e.g., Phragmites australis and T. latifolia) pointed to warmer and shallower conditions, while the late Holocene was characterized by strong eutrophication and reed swamp dominance on the lakeshore. Elevated macrocharcoal concentration, wood fragments and remains of Typha species suggested frequent local fires and dry mire surface conditions during the last 1700 years.

A shallow lake in an agricultural landscape – water quality, nutrient loads, future management

Abstract Qualitative analyses of nitrogen and phosphorus loads reaching the lake ecosystem provide a basis for pollution control, which is of paramount importance in shallow lakes due to the rapid turn-over of matter and energy. The studies of both external and internal loading were conducted in Lake Łeknenskie, a very shallow, through-flow lake situated in Western Poland. Strong eutrophication is manifested in rich rush vegetation and a lack of submerged macrophytes as well as nitrogen and phosphorus concentrations (max 13.04 mg N dm−3 and 0.32 mg P dm−3, respectively). Constant domination of cyanobacteria in the phytoplankton community was noted in almost all seasons with a 98% share in summer, resulting in 20 cm water transparency and 223 μg dm−3 of chlorophyll-a. The zooplankton community was dominated by rotifers. The main source of nutrients was the River Nielba. Spatial external nutrient loading was 1.93 g P m−2 yr−1 and 77.55 g N m−2 yr−1. An even higher load of phosphorus was released from the bottom sediments, 2.18 g P m−2 yr−1. A comprehensive action plan is required, aiming at the reduction of both external and internal nutrient loading. A series of solutions regarding local environmental conditions should be applied in the lake catchment, including biogeochemical barriers, denitrification walls, artificial retention basins or wetlands, but most of all – improvement in the functioning of the wastewater treatment plant. Restoration is possible, however, protection measures reducing external loading should be undertaken prior to phosphorus inactivation in the water column and in the bottom sediments, supported by biological methods e.g. biomanipulation.

Long-Term Dynamics of Biological Diversity in Water Basins

The structural complexity of communities of living organisms can be assessed in various ways, including diversity indices. For these purposes, the Shannon index (H) was used in the present study. Based on the scarce available published data and our own data, the rates of changes in the number of species and complexity of the community structure of aquatic organisms were determined with reference to macrobenthos communities. The considered changes were described by equations of specific functions that were mathematically analyzed. It was suggested that, in a temperate climate and the absence of strong contamination or eutrophication of water bodies, 12–14 years on average are required for the formation of a complex structure (3–4 bits) of benthic animals under favorable conditions. The complex structure of communities formed in polluted waters remains rather constant. Longer studies (at least 20–30 years) than those used in the present work are necessary to verify and refine the above assumptions

The role of European smelt Osmerus eperlanus in fish fauna structure of the Imandra Lake Basin (Murmansk Province)

The current trends of the fish community transformation processes in the Imandra Lake Basin (Murmansk Province) under processes of climate and hydrological regime changes, intensification of water eutrophication and pollution were studied. The continuing anthropogenic pollution load on the lake together with the uncontrolled fishery and the lack of favorable conditions for fish reproduction led to a decrease of quantity and share of long-cycle stenobiont fall-spawning salmonid and coregonid species in fish fauna structure. At the same time the amount of eurybiont spring-spawning low commercial value species, such as a European smelt Osmerus eperlanus (Linnaeus) was seriously increased. It was found that the smelt population growth is accompanied by an increase in its size and weight parameters. The highest size values of this species now are comparable to smelt of the Onega and Ladoga lakes. It was also mentioned that smelt demonstrates quite an intense self-dispersion within the Imandra Lake Basin. Smelt expands rapidly within the subordinate lake and river system of Bolshaya Imandra Lake. One of the most interesting phenomena now is a process of fish self-dispersion along the Bolshaya Belaya River. It was found that the smelt shows a very active expansion of habitat, despite of the intense impact of apatite-nepheline production and strong eutrophication of water. It is shown that European smelt have good opportunity to naturalize and form an isolated self-reproducing population in a typical mountain reservoir – Bolshoi Voodyavr Lake, influenced by intensive mining industry. The observed expansive strategy of low commercial value species could be consider as invasion of alien species, reducing resistance and resource potential of the freshwater ecosystems of the North.

Combining conflicting, economic, and environmental pressures: Evaluation of the restored Lake Karla (Thessaly-Greece)

In this paper, the restoration of Lake Karla's ecosystem is studied through the evaluation of its current status. Lake Karla was one of the most important wetlands of Greece with many benefits not only to biodiversity preservation, to water balance of the watershed, but also to local economy in terms of fisheries. Its drainage, in 1962, created a lot of environmental problems and led to the local economy shrinking. After its refilling, the newly re-established water body is considered a vital aquatic ecosystem since it is listed in the network of Natura 2000. The monitoring results, the pressures and their causes that affected the restoration effort are presented. The assessment of the water quality is achieved by evaluating the results of the monitoring and fieldwork programs that Management Body of Eco-development Area of Lake Karla has performed during the last four years funded by the European Union. The results indicate strong eutrophication along with threats to biodiversity. The delay of implementation of Lake Karla reconstruction project, the decline from the proposed Environmental Terms and the lack of environmental policy are the most important causes of pressures.

Nutrient Level Change Based on Calcareous Nannofossil Assemblages During Late Miocene in Banyumas Subbasin

DOI:10.17014/ijog.3.3.183-194Hydrographic situation on surface waters is more challenging to be understood, related to global and regional climate change in tropical regions. In addition, records from these tropical areas are limited compared to other areas of subtropical and polar regions. The aim of this study is to reconstruct Cenozoic paleoceanography, in particular nutrient level, using outcrop samples from Kali Pasir, Banyumas, Indonesia. This study is focused on the relationships of the relative abundance of Discoaster, coccolith size of Reticulofenestra, and lithofacies characteristics. Nutrient level is reconstructed using quantitative analysis of calcareous nannofossil by counting calcareous nannofossils on 400 fields of View (FOV) for each sample. The abundance of Discoaster and the large Reticulofenestra represent a deep thermocline and nutricline, which is a typical of oligotrophic condition. This condition also associated with the muddy facies in the early stages of Late Miocene (NN8-NN10a). Conversely, decreasing Discoaster abundance and the abundance of small Reticulofenestra indicate a shallow thermocline and nutricline, resulting strong eutrophication of surface waters in the later stage of Late Miocene (NN10b-NN11). A high nutrient content in this stage is related to classical turbidite deposits. A change in a sea surface resulted in strong eutrophication, which is in this section similar to the eastern Indian Ocean micropaleontology records during the Late Miocene (NN10). This finding shows that strong eutrophication in Kali Pasir section is probably driven by nutrient-rich terrestrial material related to the onset of Indian monsoon during the Late Miocene.

Late glacial initiation of Holocene eastern Mediterranean sapropel formation.

Recurrent deposition of organic-rich sediment layers (sapropels) in the eastern Mediterranean Sea is caused by complex interactions between climatic and biogeochemical processes. Disentangling these influences is therefore important for Mediterranean palaeo-studies in particular, and for understanding ocean feedback processes in general. Crucially, sapropels are diagnostic of anoxic deep-water phases, which have been attributed to deep-water stagnation, enhanced biological production or both. Here we use an ocean-biogeochemical model to test the effects of commonly proposed climatic and biogeochemical causes for sapropel S1. Our results indicate that deep-water anoxia requires a long prelude of deep-water stagnation, with no particularly strong eutrophication. The model-derived time frame agrees with foraminiferal δ(13)C records that imply cessation of deep-water renewal from at least Heinrich event 1 to the early Holocene. The simulated low particulate organic carbon burial flux agrees with pre-sapropel reconstructions. Our results offer a mechanistic explanation of glacial-interglacial influence on sapropel formation.

High Frequency Records of Nutrients and Algal Biomass Pigments for Deciphering Biogeochemical Processes in the Loire River (France)

A high temporal hydro-biogeochemical monitoring based on daily discharges and Total Suspended Solids concentrations and on a three-day frequency survey of nutrients (NO3, PO4, SiO2) and algal biomass pigments was carried out during 2012 at three strategic stations in the Loire River. In a context of a strong eutrophication history, this survey aimed at observing temporal variability and deciphering biogeochemical processes at a fine temporal scale such as nutrients uptake by different phytoplankton species, P-limitation, N losses, and the impact of hydrological events on algal biomass.

ANALYSIS OF SEASONAL CHANGES IN WATER QUALITIES IN EUTROPHIC RESERVOIRS IN A FLAT LOW‐LYING AGRICULTURAL AREA USING AN ALGAE‐BASED ECOSYSTEM MODEL

ABSTRACTIn this study, a one‐box ecosystem model evaluating four algal groups (green algae, blue‐green algae, diatoms/dinoflagellates, and cryptophytes) was constructed for three eutrophic reservoirs in a flat, low‐lying agricultural area. These reservoirs are used as agricultural water resources, and they differ in characteristics such as water depth, storage capacity, and vegetation. Water quality surveys of the chlorophyll‐a concentration of each algal group, total organic carbon (TOC), dissolved organic carbon (DOC), total nitrogen (TN), total phosphorus (TP), and dissolved oxygen (DO) were conducted weekly, from July to November 2009, to verify the validity of the ecosystem model. The model evaluated seasonal changes in water qualities for the different eutrophic reservoirs and could estimate the dynamic characteristics of nutrients related to the seasonal changes in algae. The study showed promising results and the model could be used to simulate the relationship between phytoplankton and nutrients, as well as seasonal changes in the species composition of algae during the brief but critical period when strong eutrophication occurred. Copyright © 2013 John Wiley & Sons, Ltd.

Species introduction – a major topic in vegetation restoration

Holzel, N. (corresponding author, nhoelzel@uni-muenster.de): Institute of Landscape Ecology, University of Munster, Robert-Koch-Str. 28, 48149, Munster, Germany Buisson, E. (elise.buisson@univ-avignon.fr) & Dutoit, T. (thierry.dutoit@univ-avignon.fr): Institut Mediterraneen d’Ecologie et de Paleoecologie (UMR CNRS/IRD), IUT, Universite d’Avignon et des Pays de Vaucluse, site Agroparc BP 61207, 84 911, Avignon Cedex 09, France