Episodes Of Eutrophication Research Articles

Paleoceanographic changes across OAE 2 inferred from resilient foraminifera and XRF data at southern high latitudes (IODP Sites U1513 and U1516, Mentelle Basin, SW Australia)

The Oceanic Anoxic Event 2 (OAE 2), across the Cenomanian-Turonian boundary interval, was characterized by global environmental perturbations in the carbon cycle that affected the abundance and biodiversity of marine biota and their paleoecological preferences. International Ocean Discovery Program (IODP) Sites U1513 and U1516 in the Mentelle Basin (offshore SW Australia) reveal a continuous foraminiferal record that document the adaptative response of biota, suitable to reconstruct paleoenvironmental conditions in the water column and at the seafloor. Below and during the initial part of the OAE 2, we do not observe changes in the benthic foraminiferal assemblages dominated by Gavelinella, Gyroidinoides and Stensioeina. Agglutinated foraminifera are rare, whereas Microhedbergella and Muricohedbergella dominate the planktonic foraminiferal assemblage, indicating possible eutrophication episodes below and during the OAE 2 associated to an increase in terrigenous sediments.However, a positive peak in Zr/Rb ratios, the unique occurrence of Stensioeina truncata, and the increase in epifaunal- infaunal ratio, particularly at Site U1516, indicate a greater eolian transportation of sediments and an enhanced oxygenation at the seafloor, which might be related to the identification of the Plenus Cold Event (PCE) at high latitudes. An interval of low CaCO3 content within the peak of OAE 2 is characterized by the absence of foraminifera and dominance of siliceous organisms. It is also marked by a sudden enhancement of the hydrological cycle, probably causing a shoaling of the Calcite Compensation Depth (CCD). However, Site U1516 shows few samples with a change in the planktonic and benthic foraminiferal assemblage.Above this interval, both sites are characterized by a different benthic foraminiferal assemblage with the occurrence of Conorboides claytonensis in the uppermost part of OAE 2. At Site U1513, epi-infaunal ratio increase, planktonic foraminifera show the highest diversification, rainfall decreases, indicating a recovery towards a well-stratified water column with mesotrophic regimes and a drier environment, whereas Site U1516 shows a slower recovery.

Assessing habitat microscale conditions underlying with mortality and survival of Pinna nobilis in the Mar Menor coastal lagoon (SE Spain)

Pinna nobilis Linnaeus, 1758 is a Mediterranean endemic bivalve critically endangered due to a severe epidemic caused mainly by the parasite Haplosporidium pinnae. Presently, live populations in Spanish waters are restricted to the Ebro Delta (Catalonia) and the Mar Menor (Murcia). The coastal lagoon of the Mar Menor has faced several eutrophication crises since 2016, which pose a threat to the survival of P. nobilis. Since 2016, >95% of the specimens of this species have died due to recurrent episodes of eutrophication in the lagoon. An analysis of the mortality within the relict population of P. nobilis in the Mar Menor lagoon after the last population survey in 2019 has been carried out, together with a characterisation of some microscale factors that describe its current habitat in the lagoon. For this purpose, three sampling localities were selected along the east coast of the lagoon, where a study of both live and dead individuals was conducted. Additionally, a characterisation of the macrophyte beds and the sediment conditions surrounding these individuals was carried out, comparing the sediment near the recently dead and live individuals. All studied localities exhibit similar mixed macrophyte beds of Cymodocea nodosa (Ucria) Asch., 1870 and Caulerpa prolifera (Forsskål) J.V. Lamouroux, 1809. At the location where significantly less C. nodosa cover was observed, the mortality of P. nobilis individuals was higher, and the sediment near the dead individuals was also more disturbed (with a more negative Eh and higher percentage of organic matter). These results contribute to a better understanding of the dynamics of microscale factors following P. nobilis mortality events, facilitating the identification of potential survival areas.

Looking for the surviving optimal areas for the threatened species Pinna nobilis in a highly anthropized coastal lagoon (Mar Menor, SE Spain)

Pinna nobilis, an endemic bivalve species in the Mediterranean Sea, is critically endangered mainly due to the devastating impact of the protozoan parasite Haplosporidium pinnae. The population within the Mar Menor lagoon (Murcia, Spain) represents one of only two surviving populations along the Spanish coast. This relict population has witnessed a significant decline since 2016, primarily due to eutrophication episodes and other anthropogenic impacts affecting the lagoon. It is imperative to identify the most suitable zones for the survival of this species, where adult individuals could be translocated from affected areas to enhance their chances of survival. In the present study, we identify these zones through a Multi-Criteria Evaluation considering several factors that pose a threat to the species. This evaluation was complemented using Geographic Information Systems based multi-criteria decision analysis (GIS-MCDA). A total of 18 factors were weighted and combined, resulting in a surface area of 307.92 hectares (2.28% of the lagoon) with over 70% high suitability for species survival.

Chlorophyll-α forecasting using LSTM, bidirectional LSTM and GRU networks in El Mar Menor (Spain)

Abstract The objective of this research is to develop accurate forecasting models for chlorophyll-α concentrations at various depths in El Mar Menor, Spain. Chlorophyll-α plays a crucial role in assessing eutrophication in this vulnerable ecosystem. To achieve this objective, various deep learning forecasting techniques, including long short-term memory, bidirectional long short-term memory and gated recurrent uni networks, were utilized. The models were designed to forecast the chlorophyll-α levels with a 2-week prediction horizon. To enhance the models’ accuracy, a sliding window method combined with a blocked cross-validation procedure for time series was also applied to these techniques. Two input strategies were also tested in this approach: using only chlorophyll-α time series and incorporating exogenous variables. The proposed approach significantly improved the accuracy of the predictive models, no matter the forecasting technique employed. Results were remarkable, with $\overline{\sigma}$ values reaching approximately 0.90 for the 0.5-m depth level and 0.80 for deeper levels. The proposed forecasting models and methodologies have great potential for predicting eutrophication episodes and acting as decision-making tools for environmental agencies. Accurate prediction of eutrophication episodes through these models could allow for proactive measures to be implemented, resulting in improved environmental management and the preservation of the ecosystem.

136 Years of variation of sediment-associated metals in a subtropical reservoir in southern Brazil: Implications for the environmental change

Urban water supply reservoirs, their quality and quantity of water are affected by anthropogenic activities and environmental changes. They are aquatic ecosystems that respond to the dynamics of organic loads and nutrients, and episodes of eutrophication. Past disturbances in the watersheds and the water column can be noticed by the vertical distribution of heavy metals and trace metals in the sedimentary core. In this study, two sediment cores from the Passauna reservoir in Curitiba, Brazil were examined to assess the accumulation of heavy metals such as lead (Pb), cadmium (Cd), chromium (Cr), copper (Cu), zinc (Zn), and nickel (Ni), and other major elements such as aluminum (Al), iron (Fe), manganese (Mn), potassium (K) and barium (Ba), and their association to pollution. Enrichment factor (EF) and geoaccumulation index (Igeo) were applied to the identified accumulation of metals as well as to the level of pollution. The decay of radionuclides, including 210Pb and 137Cs, were used to find the rate of sedimentation over 136 years. The results showed a spatial variation, with the highest concentration of metals found in the upstream part of the reservoir. The EF values of the following metals decreased: in core I, EF(Fe) > EF(Mn) > EF(Cd) > EF(Sb) > EF(Zn) > EF(Cu) > EF(Cr) > EF(Pb); and in core II, EF(Sb) > EF(Pb) > EF(Cd) > EF(Cr) > EF(Fe) > EF(V) > EF(Zn) > EF(Cu) > EF(Ni) > EF(Mn). The Igeo values of the metals decreased in core I Igeo(Fe) > Igeo(Sb) > Igeo(Al) > Igeo(Zn) > Igeo(Cd) > Igeo(Cd) > Igeo(Ni) > Igeo(Cr) > Igeo(Mn) > Igeo(Pb) > Igeo(V); and in core II, Igeo(Sb) > Igeo(Cd) > Igeo(Pb) > Igeo(Al) > Igeo(Cr) > Igeo(V) > Igeo(Fe) > Igeo(Cu) > Igeo(Ni) > Igeo(Zn) > Igeo(Mn). We used the Mn/Fe, Cu/Ni, and V(V + Ni) ratio to evidence changes in productivity and redox conditions in the water column over time.We observed that during the period 1930–1970 anthropogenic activities controlled the impacts on reservoir and water quality. The changes in the distribution of metals coincided with the expansion of agriculture and urban area. In addition, redox and productivity showed periods with different rates of productivity as well as alternate periods of trophic levels. In sum, this paper provides information on how the depositional environment affects the geochemical characteristics of sediment, explaining past environmental changes.

Monitoring Sand Spit Variability Using Sentinel-2 and Google Earth Engine in a Mediterranean Estuary

Estuarine degradation is a major concern worldwide, and is rapidly increasing due to anthropogenic pressures. The Mediterranean Guadiaro estuary, located in San Roque (Cadiz, Spain), is an example of a highly modified estuary, showing severe negative effects of eutrophication episodes and beach erosion. The migration of its river mouth sand spit causes the closure of the estuary, resulting in serious water quality issues and flora and fauna mortality due to the lack of water renewal. With the aim of studying the Guadiaro estuary throughout a 4-year period (2017–2020), the Sentinel-2 A/B twin satellites of the Copernicus programme were used thanks to their 5-day and 10 m temporal and spatial resolution, respectively. Sea–land mapping was performed using the Normalized Difference Water Index (NDWI) in the Google Earth Engine (GEE) platform, selecting cloud-free Sentinel-2 Level 2A images and computing statistics. Results show a closure trend of the Guadiaro river mouth and no clear sand spit seasonal patterns. The study also reveals the potential of both Sentinel-2 and GEE for estuarine monitoring by means of an optimized processing workflow. This improvement will be useful for coastal management to ensure a continuous and detailed monitoring in the area, contributing to the development of early-warning tools, which can be helpful for supporting an ecosystem-based approach to coastal areas.

Use of Artificial Neural Networks as a Predictive Tool of Dissolved Oxygen Present in Surface Water Discharged in the Coastal Lagoon of the Mar Menor (Murcia, Spain).

The Mar Menor is a Mediterranean coastal saltwater lagoon (Murcia, Spain) that represents a unique ecosystem of vital importance for the area, from both an economic and ecological point of view. During the last decades, the intense agricultural activity has caused episodes of eutrophication due to the contribution of inorganic nutrients, especially nitrates. For this reason, it is important to control the quality of the water discharged into the Mar Menor lagoon, which can be performed through the measurement of dissolved oxygen (DO). Therefore, this article aimed to predict the DO in the water discharged into this lagoon through the El Albujón watercourse, for which two theoretical models consisting of a multiple linear regression (MLR) and a back-propagation neural network (RPROP) were developed. Data of temperature, pH, nitrates, chlorides, sulphates, electrical conductivity, phosphates and DO at the mouth of this watercourse, between January 2014 and January 2021, were used. A preliminary statistical study was performed to discard the variables with the lowest influence on DO. Finally, both theoretical models were compared by means of the coefficient of determination (R2), the root mean square errors (RMSE) and the mean absolute error (MAE), concluding that the neural network made a more accurate prediction of DO.

Long-term forecasting in a coastal ecosystem: case study of a Southern restored Mediterranean lagoon: The North Lagoon of Tunis

Eutrophication episodes are common in freshwater and coastal environments, causing significant damage to drinking water and aquaculture. Predictive models are efficient approaches for anticipating eutrophication or algal blooms because ecologists and environmentalists can estimate water pollution levels and take appropriate precautionary steps ahead of time. In aquatic ecosystems, chlorophyll-a (Chl-a) can be employed as a water quality indicator, revealing information on man-made physical, chemical, and biological changes variations or seasonal interventions. In the present study, a Seasonal AutoRegressive Integrated Moving Average (SARIMA) model was developed to forecast monthly Chl-a concentrations in the North Lagoon of Tunis, a Ramsar site, and one of the most important lagoons in Tunisia, using approximately three decades of historical data, starting from January 1989 to April 2018. SARIMA (2,0,2)(2,0,2)12 was found to be the best-fitting model for Chl-a forecasting in the North Lagoon of Tunis. The resulting SARIMA model was validated with actual monthly Chl-a concentrations from our last observations. Furthermore, with only one input variable, the SARIMA model showed greater applicability as a eutrophication early warning system using actual past Chl-a data. Finally, the SARIMA model was utilized to anticipate Chl-a levels from May 2018 to December 2025 as an early warning system for ecosystem managers and decision-makers for next generations.

Evaluation of a membrane bioreactor on dairy wastewater treatment and reuse in Uruguay

Eutrophication episodes have been recently observed in the Santa Lucia river basin (SLRB) in Uruguay, the main drinking water source for approximately 60% of the Uruguayan population. The local environmental authorities have been strengthening the discharge standards for that particular river basin. There are several industries currently discharging their wastewater directly into the SLRB; some of these industries are required to upgrade their current wastewater treatment systems to comply with the new regulations. This study evaluated the performance of a membrane bioreactor (MBR) on dairy wastewater as a potential treatment technology for fulfilling the new discharge standards. A pilot MBR was placed at the dairy industry wastewater treatment system at two different locations: (i) receiving the wastewater from the industrial process after passing through a grease removal pond (high load stream); and (ii) receiving the wastewater after passing through the grease removal pond and an anaerobic pond (low load stream). The pilot MBR was operated at the following conditions for approximately four months: total sludge retention, hydraulic retention time (HRT) of 25 h, an average influent flow rate of 1.3 m3 day−1, and at two different average chemical oxygen demand (COD) influent concentrations: 1300 mg L−1 (high load stream) and 385 mg L−1 (low load stream). The average reported removal efficiencies on COD, biological oxygen demand (BOD), and ammonium (NH4-N) were 94.1, 98.1, and 99.6%, respectively. In addition, it was observed that for a COD/N ratio above 10, total nitrogen (TN) and total phosphorous (TP) were well removed with average removal efficiencies of 93.1 and 91.0%, respectively. The MBR effluent met the new Uruguayan standards for discharging into the SLRB, and it can be further considered for water reuse at the industrial process. Moreover, a financial feasibility study was carried out for the implementation of a full scale MBR at the existing dairy facility. The results of the feasibility study suggested to accept the investment for the implementation of the MBR technology at the dairy industry. The results of the feasibility analysis considered the high impact of penalties and fines imposed by the local government to the industry when not complying with the effluent discharge standards, as well as the critical situation regarding eutrophication of the SLRB while being the most important source for drinking water in Uruguay.

Long term evolution of fisheries in a coastal lagoon related to changes in lagoon ecology and human pressures

Mediterranean coastal lagoons are among the most productive of marine ecosystems but, at the same time, they are strongly affected by anthropogenic pressures that could alter their fisheries. This work looks at how the Mar Menor coastal lagoon fishery evolved from the eighteenth century to 2012, and provides data about landings, effort and gears. The relationships between fishing yields and the environmental consequences of the most important human activities in the lagoon (including the dredging and widening of inlets in the last two centuries and eutrophication episodes in the 1990s) are examined using uni- and multi-variate analysis. While mean total yield tended to remain constant, significant changes in the specific composition of the catch and in the dominance of the main target species have occurred. The lagoon seems to have the ability to support a wide range of pressures and environmental changes, since it has been seen to recover each time from specific human impacts, maintaining the fishery yields close to the total maximum sustainable yield. However, other factors, like climate change or the spread of aquaculture exploitations, may have overlapping effects, introducing long term trends in the fisheries concerned.

Phosphorus budget in the water‐agro‐food system at nested scales in two contrasted regions of the world (ASEAN‐8 and EU‐27)

AbstractPhosphorus (P) plays a strategic role in agricultural production as well as in the occurrence of freshwater and marine eutrophication episodes throughout the world. Moreover, the scarcity and uneven distribution of minable P resources is raising concerns about the sustainability of long‐term exploitation. In this paper we analyze the P cycle in anthropic systems with an original multiscale approach (world region, country, and large basin scales) in two contrasting world regions representative of different trajectories in socioeconomic development for the 1961–2009 period: Europe (EU‐27)/France and the Seine River Basin, and Asia (ASEAN‐8)/Vietnam and the Red River Basin. Our approach highlights different trends in the agricultural and food production systems of the two regions. Whereas crop production increased until the 1980s in Europe and France and has stabilized thereafter, in ASEAN‐8 and Vietnam it began to increase in the 1980s and it is still rising today. These trends are related to the increasing use of fertilizers, although in European countries the amount of fertilizers sharply decreased after the 1980s. On average, the total P delivered from rivers to the sea is 3 times higher for ASEAN‐8 (300 kg P km−2 yr−1) than for EU‐27 countries (100 kg P km−2 yr−1) and is twice as high in the Red River (200 kg P km−2 yr−1) than in the Seine River (110 kg P km−2 yr−1), with agricultural losses to water in ASEAN‐8 3 times higher than in EU‐27. Based on the P flux budgets, this study discusses early warnings and management options according to the particularities of the two world regions, newly integrating the perspective of surface water quality with agricultural issues (fertilizers, crop production, and surplus), food/feed exchanges, and diet, defining the so‐called water‐agro‐food system.

Eutrophication of turbid tropical reservoirs: Scenarios of evolution of the reservoir of Cointzio, Mexico

This study provides the first numerical simulation of physical and biogeochemical processes in a very turbid and highly eutrophic tropical reservoir of the Trans-Mexican Volcanic Belt in Mexico. The Cointzio reservoir (capacity 66Mm3) is characterized by a lack of water treatment plants upstream and a high content of very fine clay particles. It suffers serious episodes of eutrophication associated with high levels of turbidity and benthic anoxia. Different scenarios for future climate inputs, nutrient inputs and water levels were simulated. The results pointed out the potential negative long-term impact of climate change on this reservoir. In this region, an increase of average air temperature as high as 4.4°C is expected by the end of the century. When coupled with a low water level, this increase could lead to critical conditions with a severe depletion of dissolved oxygen and important algal blooms with chlorophyll a reaching values of up to 94μgL−1. The calculations indicated that a drastic reduction of nutrient inputs (up to 90%) would be required to significantly reduce chlorophyll a concentrations. If such mitigation measures are adopted, the maximum peak of chlorophyll a would be reduced by 55% after a ten-year period of efforts, with corresponding positive effect on dissolved oxygen concentrations. The main limitation of the chosen numerical approach comes from the assumption of a constant water level in the model. This may be particularly critical for shallow type reservoirs.While this region remains poorly studied, this study brings original information that will help stakeholders to adopt appropriate strategies for the management of their waterbodies that experience critical eutrophication.

Late Hauterivian–early Barremian calcareous nannofossil biostratigraphy, palaeoceanography, and stable isotope record in the Subbetic domain (southern Spain)

Two sections in the Subbetic domain of the Betic Cordillera (Río Argos and Arroyo Gilico), encompassing the latest Hauterivian–earliest late Barremian interval, and including the Faraoni level equivalent (FLE) and the ‘Mid-Barremian event’ (MBE), were selected for stable isotope analyses and calcareous nannofossil investigation. Six calcareous nannofossil bioevents were identified throughout the study interval, which were used in the identification of NC5B, NC5C, NC5D and NC5E subzones. Calcareous nannofossil bioevents and subzones have been directly correlated to Tethyan ammonite biostratigraphical zonation and with respect to a detailed carbon and oxygen stable isotope stratigraphy. An integrated analysis of calcareous nannofossil assemblages and chemostratigraphic data (carbon and oxygen isotopes) enabled the reconstruction of the surface water conditions throughout the study interval. Calcareous nannofossil assemblages record several episodes of relative eutrophication of surface water that correlate with relative minimum values in the stable oxygen isotope curves. These eutrophication episodes are interpreted as the result of probably warmer and wetter climatic conditions in the continental hinterlands adjacent to the Subbetic Basin, which led to an enhanced runoff and increased freshwater input to the sea. During these episodes, surface waters were enriched in nutrients and probably had a lower salinity, favouring the development of a high nutricline and, occasionally, water stratification and development of localized dysoxic/anoxic bottom sedimentary environments. Most of these episodes are of minor importance, and only two of them (those correlating with FLE and MBE), had sufficient impact on the marine environments to generate deviations in the stable carbon isotope record and localized deposition of organic-rich sediments. This suggests that global dysoxic/anoxic episodes, such as those linked to OAEs, probably do not represent singular events in a normally undisturbed environment, but are part of long-lasting periods of environmental change.

Warm-phase ENSO events modulate the continental freshwater input and the trophic state of sediments in a large South American estuary

We studied the changes in geochemical variables in the middle section of Río de la Plata estuary during the 2009–2010 El Niño–Southern Oscillation (ENSO) event. Protein, organic matter, chlorophyll-a and phaeopigment content of surface sediments were significantly correlated with the increased continental freshwater input associated with high total monthly rainfall. During the warm-phase ENSO event, river flow was 5-fold larger than average historical levels, which led to a steady decrease in salinity values and the highest levels of geochemical variables. The evidence presented herein suggests that warm-phase ENSO events increase the trophic state of the sediments because of the increased freshwater input. Thus, our findings may be useful to anticipate potential eutrophication episodes in the study area.

Effect of feed characteristics on the organic matter, nitrogen and phosphorus removal in an activated sludge system treating piggery slurry

Piggery wastewater is characterized by its high content in nitrogen and phosphorus, as well as by a low C/N ratio. This type of wastewater is traditionally spread to croplands (with its subsequent leaching to groundwater) or rarely discharged into natural water bodies, which ultimately cause severe episodes of eutrophication in aquatic ecosystems. In this context, activated sludge systems constitute a robust and efficient treatment option. The performance of an activated sludge process using a pre-denitrification configuration treating both sieved and flocculated swine slurry at a hydraulic retention time (HRT) of 7.7 days was evaluated. In order to avoid bacterial wash-out, sludge from the settler was recirculated to the anoxic tank to accomplish denitrification. Once the biomass was acclimatized, the reactor was fed with swine slurry containing 19, 2.6, and 0.27 g/L of total chemical oxygen demand (COD), total Kjeldhal nitrogen (TKN), and soluble P, respectively. Nitrogen removal showed a clear dependency on the influent composition. When the influent TKN/total COD and soluble COD/total COD ratios were respectively 0.12-0.15 and 0.7, the reactor exhibited good removal efficiencies (up to 99 and 91 for N-NH(4)(+), TKN, respectively) while PO(4)(3-) was removed up to 65%. However, when the influent TKN/total COD ratio rose to 0.26 and soluble COD/total COD decreased to 0.3, the denitrification process was severely hindered concomitant with and accumulation of nitrite. Nevertheless, organic matter degradation was not affected by influent composition. At the last stage of the experiment, removals of dissolved phosphorus fell to 40% when the redox potential (ORP) profile showed a constant value of -400 mV, likely due to phosphate released from bacterial sludge.

Thresholds of terrestrial nutrient loading for the development of eutrophication episodes in a coastal embayment in the Aegean Sea

1 - Thresholds of terrestrial nutrient loading (inorganic N and P) for the development of eutrophication episodes were estimated in an enclosed embayment, the gulf of Kalloni, in the Aegean, Eastern Mediterranean. Terrestrial loading was quantified by a watershed runoff model taking into account land use, geomorphology, sewerage, industrial and animal farming by-products. The eutrophication episodes were assessed by an existing scale for the Aegean coastal waters based on chl a, whereas the necessary nutrient concentrations (N and P) for the development of such episodes were defined using a probabilistic procedure. Finally, for the linking between nutrient loading arriving at the gulf and the resulting nutrient enrichment of the marine ecosystem, three loading factors were applied, developed by Vollenweider for lake and marine ecosystems. The first assumes no exchange between the embayment and the open sea, whereas the two others take into account water renewal time. Only the threshold for inorganic nitrogen estimated by the first factor was exceeded in the study area during February after a strong rainfall event coinciding with a eutrophication episode observed in the interior of the gulf, implying that the waters of the gulf are rather confined and the receiving body operates as a lake. The degree of confinement was further examined by studying the temperature, salinity, and density distributions inside the gulf and across the channel connecting the gulf to the open sea. It was found that the incoming freshwater from the watershed during winter results to the formation of a dilute surface layer of low salinity and density, clearly isolated from the open sea. The nutrients from the river inputs are diluted into this isolated water mass and the eutrophication threshold for nitrogen is exceeded. Although phosphorus loading was also high during winter, the corresponding limits were never exceeded. The proposed methodology sets a quantitative relationship between terrestrial nutrient loading and the development of eutrophication episodes in coastal embayments, assuming that information on the physical setting of the system is available. These cause-and-effect relationships can be invaluable tools for managers and decision makers in the framework of Integrated Coastal Zone Management.

The regional record of Albian oceanic anoxic events at the Apulian Platform Margin (Gargano Promontory, southern Italy)

The Gargano Promontory, located on the eastern margin of the Apulia Platform, represents a distinctive Tethyan area where the transition from carbonate platform to adjacent basin is exposed on land. The Albian stratigraphic record, represented by shallow-water, slope and deep-water deposits, provides a good opportunity to investigate the regional response to oceanic anoxic events (OAEs) in different depositional settings by using an integrated, high-resolution micropalaeontological (planktonic foraminifers and calcareous nannofossils) approach. Results show that organic matter preservation is confined to the more distal areas (Marne a Fucoidi Formation), and consists of black shale intervals from the middle and late Albian ( Ticinella primula/Prediscosphaera columnata Zones; upper Ticinella praeticinensis Subzone/ R. achlyostaurion Zone, respectively). Integrated biostratigraphic data correlate the intervals of black shale deposition to the Urbino and Amadeus levels, previously identified and named in the Umbria-Marche Basin. These black shales record the effects of OAEs 1b and 1c. The biotic changes in the pelagic Albian succession of the Apulian Platform Margin provide evidence for episodes of eutrophication that correlate to the deposition of these black shales. Genetic models for the two episodes of organic matter preservation are proposed, taking into account both global and local controlling factors.

Phytoplankton biomass and size structure in two South African eutrophic, temporarily open/closed estuaries

The biomass and size structure of phytoplankton were compared in the temporarily open/closed Mdloti and Mhlanga estuaries, in KwaZulu-Natal, South Africa. Samples and measurements were taken between March 2002 and March 2003, to assess the effects of differing mouth breaching regimes, freshwater inflow and nutrient loading on the dynamics of phytoplankton. The Mdloti Estuary exhibits a larger catchment area (≈500 km 2), substantial upstream impoundment (Hazelmere Dam) and little discharge of treated sewage waters in its upper reaches (8 Ml d −1). Conversely, the Mhlanga Estuary has a smaller catchment area (≈100 km 2), no upstream dams and a large inflow of treated sewage waters (20 Ml d −1), resulting in a capping flow of 0.23 m 3 s −1. DIN and DIP concentrations were usually well above the accepted threshold levels (2 μM for DIN and 0.5 μM for DIP) for nutrient-limited primary production and were also much higher in the Mhlanga than in the Mdloti. This led to episodes of eutrophication, with high levels of mean chl- a occurring in the Mhlanga Estuary in particular. In both estuaries, highest chl- a concentrations occurred during the closed phase, while the lowest occurred during the open phase. Phytoplankton biomass ranged from 0.869 to 111 mg chl- a m −3 in the Mdloti, and from 0.732 to 303 mg chl- a m −3 in the Mhlanga. The maximum value of 303 mg m −3 of chl- a, recorded at the Mhlanga in October 2002, is the highest chl- a concentration ever recorded in any South African estuary. In both estuaries, phytoplankton biomass was dominated by the nanophytoplankton fraction (2–20 μm) during the entire study period. This accounted for an average of 80.6% and 79.6% of the total phytoplankton biomass in the Mdloti and the Mhlanga, respectively. This was followed by the picophytoplankton (<2 μm), with 12.9% at the Mdloti and 11.9% at the Mhlanga and the microphytoplankton (>20 μm) with 6.53% at the Mdloti and 8.65% at the Mhlanga. Due to the large volumes of treated sewage released into the two estuaries, particularly the Mhlanga, they breached more frequently than they would have under natural circumstances. Thus, despite their high nutrient concentrations, eutrophic waters within the estuaries exhibited a short residence time, thereby restricting the time available for phytoplankton to take up enough nutrients to form more regular and intense blooms.

Evolution of sediment composition of the coastal Lake San Puoto (Latium, Italy) in the last two centuries

The sediment composition of the coastal Lake San Puoto (Central Italy) was studied to obtain information on its recent environmental evolution (last 200 years). The explorative fieldwork was performed within the framework of the EU-funded PALICLAS Project. Sediment and mass accumulation rates, calculated from 210Pb analysis, show mean values of 0.27 cm y-1 and 0.11 g cm-2 y-1 respectively, with increasing values from 10 cm to the top (i.e. from ca 1960 AD to the present). The evolution of the recent sedimentation of Lake San Puoto is characterized by the interplay of three main components: detrital (either siliciclastic and/or carbonatic), organic-rich and authigenic phases. The first reflects the input from coastal dunes and rocky outcrops; the other two indicate variations in lake productivity. Sedimentological, geochemical, and mineralogical analyses of two cores collected near the center of the lake were used to define five lithological units: i) a laminated unit representing the last eutrophication period, starting ca 1925 AD; ii) a few turbidite layers, probably due to a lowering of the lake level around 1920 AD; iii) a productive phase of the lake, which occurred around the end of the XIX and the beginning of the XX century; iv) a coarse siliciclastic sediment interval, possibly deposited following the digging of the channel connecting Lake San Puoto to Lake Lungo; and v) an older unit representing the natural allochthonous detritic sedimentation deriving from the present dune deposits surrounding the lake shores. Metal fluxes were calculated for recent times by means of 210Pb sedimentation rates. Zn, Cu and Pb record considerably higher fluxes above 10 cm depth (i.e. 1960 AD), as confirmed by Al-normalized metal depth profiles. Episodes of eutrophication occurred between 1890 and 1920 and between 1925 and the present.