Eutrophic Water Research Articles

Investigation on Lanthanum Modified Kaolinite for Control of Cyanobacterial Growth and Microcystin Production

Eutrophication and its resultant cyanobacterial blooms are a severe environmental issue in global water bodies, and phosphate is regarded as one of the primary triggers. In this study, the in situ-synthesized heated kaolinite lanthanum hydroxide composite (HKL-LH) was used to treat cyanobacterial blooms through phosphate removal. A typical cyanobacteria species—Microcystis aeruginosa—was selected as the target organism. HKL-LH efficiently removed phosphate in the solution with the inoculation of M. aeruginosa over the course of one day. A good performance of HKL-LH on control cyanobacterial blooms with initial cell densities ranging from 104 cells mL−1 to 105 cells mL−1 was observed. Although the genetic expression relating to photosynthesis and cell division was upregulated under the stress of phosphorus deficiency, M. aeruginosa growth was significantly inhibited, i.e., the inhibition rate of up to 98% was achieved by 0.1g L−1 of HKL-LH. In addition to cell growth, the photosynthetic activity and viability of M. aeruginosa cells were decreased by HKL-LH. Furthermore, the production of associated toxins (microcystins) and algal organic matters were effectively inhibited, which can reduce the ecological risk and challenges that follow water treatment. In this study, it is shown that HKL-LH has excellent application potential in the mitigation of cyanobacterial blooms in eutrophic water.

Changes in land-leaching nitrogen and its linkages to lake algal blooms in China

Abstract Over the past 50 years, nutrient discharge into freshwater ecosystems has significantly increased due to intensive fertilizer applications in China. This has led to frequent environmental issues associated with nutrient enrichment, such as algal blooms, in a number of individual lakes. However, the link between terrestrial nutrient sources and algal bloom occurrences (BO) at large scales remains under-explored. Here, we simulated long-term changes in nitrogen leaching from terrestrial ecosystems at the national scale from 1979 to 2018, and examined its connection to satellite-derived BO in 56 large lakes across China. Our findings reveal that leached nitrogen exhibited significant increasing trends in 74.5% of the national landmass, with an average increase rate of 0.40 kg N ha-1 yr-2 over the past four decades. Using a 95% quantile regression model, we analyzed the linkage between nitrogen leaching and BO from 2003 to 2018. The results indicated significantly positive correlations in the lakes of the Yangtze Plain during autumn and the lakes of the Northern China and Yunnan-Guizhou Plateau during both summer and autumn. These findings suggest that terrestrial nitrogen discharge critically contributes to algal bloom variations in warmer seasons. Our study provides a comprehensive understanding of escalating nitrogen discharge from terrestrial ecosystems and highlights the potential benefits of fertilization management in mitigating and controlling inland water eutrophication in China.

Promoted growth with dynamic cellular stoichiometry driven by utilization of in-situ dissolved organic matter: Insights from bloom-forming dinoflagellate Prorocentrum donghaiense.

Mixotrophic dinoflagellates frequently cause harmful algal blooms (HABs) in eutrophic waters that contain diverse dissolved organic matter (DOM), especially intensive mariculture areas. Compared to the extensive investigation of phagotrophy and single organic molecule uptake by causative species, we have limited knowledge about the capability of mixotrophic dinoflagellates to utilize in-situ DOM in mariculture waters and its contribution to HABs. Here we use filtered in-situ mariculture water as the sole medium to examine the physiological response of Prorocentrum donghaiense to the natural mariculture DOM. Our results showed an 87.2% increase in the cell growth rate, as well as photosynthesis (16.8%-29.2%) and cellular chlorophyll a (32.4%-70.7%) when cultured with DOM compared to those grown in the inorganic medium. Meanwhile, cellular stoichiometry varied greatly among the groups supplied with mariculture DOM of different seasons, and the ecological implications were then discussed. Additionally, parallel cultures revealed the phycosphere bacterioplankton community compete with the algae cell regarding the nutrient utilization. This study quantifies the efficient utilization of in-situ mariculture DOM by P. donghaiense and indicates its vital role in sustaining HAB events and great effects on the biogeochemical cycle.

“Assessment of potential eutrophication in coastal waters of Gran Canaria: Impact on plankton community under CO2 depletion”

“Assessment of potential eutrophication in coastal waters of Gran Canaria: Impact on plankton community under CO2 depletion”

Ocean acidification and its regulating factors in the East China Sea off the Yangtze River estuary.

This study examines the seasonal variations in carbonate system parameters in the East China Sea (ECS) off the Yangtze River estuary (YRE) and analyzes the contributions of anthropogenic CO₂ and eutrophication to acidification. Carbonate parameters data were collected during summer 2019 and combined winter 2011. During winter, acidification is primarily driven by rising atmospheric CO₂, with minimal impact from biological processes. In contrast, summer presents a different pattern: enhanced photosynthesis due to eutrophication in surface waters helps mitigate the acidification effects of atmospheric CO₂ increases, while in bottom waters, the combined pressures of atmospheric CO₂ and intensified aerobic respiration leads to more severe acidification. Notably, biological processes now contribute more to acidification than increasing atmospheric CO₂ in the bottom waters. Our projections indicate that the summer bottom waters will experience the most pronounced acidification, with average pH levels expected to decline from 8.04 to 7.82 and aragonite saturation state (Ωar) values decreasing from 2.24 to 1.38 between 2000 and 2100. Additionally, our study indicates that winter acidification trends are also concerning, with pH only slightly higher than in summer bottom waters. The buffering capacity and the DIC:TA ratio play significant roles in determining the rate of future pH and Ωar declines. The strong buffering capacity in summer surface waters mitigates the pH decline, while the low DIC:TA ratio results in a rapid drop in Ωar.

Weak interaction strategy enables enhanced selectivity and reusability of arginine-functionalized imprinted aerogel for phosphate adsorption.

Efficient phosphate adsorption from eutrophic waters remains challenging, fundamentally due to inherent trade-off in common adsorbents: high-binding energy between adsorbent and phosphate compromises reusability while low-binding energy suppresses selectivity. Herein, an innovative arginine-functionalized imprinted aerogel (AFIA-1:4) was fabricated by click chemistry and imprinting modification for overcoming this trade-off through synergistic weak interactions. Results shown that AFIA-1:4 exhibited high adsorption capacity (Qmax of 40.65mg/g, 30.44% higher than phoslock), rapid kinetics (15min), and broad pH applicability (3-11) at 2mg P/L solution. Moreover, its selectivity coefficient ranged from 10 to 90 even with 15- to 125-fold excess interfering anions, surpassing common adsorbents. After 10 cycles, AFIA-1:4 still maintained 98.15% regeneration rate with 99.14% phosphate desorption. Characterizations and calculations confirmed core roles of multiple hydrogen bonds and shape screening in maintaining selectivity and reusability. These findings advanced development of next-generation of phosphate adsorbents, which contributed to sustainable prevention and management of eutrophication.

Ditch management using low-grade weirs: an opportunity for mitigating water quality and quantity impacts

To improve productivity, extensive agricultural areas in the Midwest United States require drainage systems consisting of subsurface drainage (tile) and open ditches. Transport of sediment, pathogens, pesticides, and nutrients from runoff and drainage from crop fields contributes to eutrophication and degradation of surface waters. Solutions are needed to improve environmental quality and reduce the negative impacts from runoff and agricultural drainage systems. This study assessed the effect of low-grade weirs on discharge and nitrate-nitrogen concentration and loss from a pair of experimental drainage ditches. One control (without weirs) and one treatment (with weirs) ditch were studied from 2017 through 2023 at the University of Minnesota, Southwest Research and Outreach Center near Lamberton, MN, United States. This study was the first evaluation of agricultural ditches, with and without low-grade weirs, and their potential to mitigate discharge and nitrogen loss in a cold climate. Stage-discharge data were collected using a data logger and bubble level sensor. Water samples were collected for water quality analysis daily using automated samplers. Analysis of the data was conducted using paired t-tests and a paired analysis approach. Analysis of covariance and linear regression of the treatment ditch against the control ditch were highly significant for nitrate-nitrogen concentration and load. The ditch with the low-grade weir was found to significantly decrease nitrate-nitrogen concentration and load. More specifically, the treatment ditch reduced discharge, nitrate-nitrogen concentration and load by 51%, 22% and 58%, respectively. The greatest discharge from the ditches occurred in March while most nitrogen losses occurred between May and June. This study provides evidence and highlights the potential of ditches equipped with low-grade weirs to reduce nitrate-nitrogen losses when compared to ditches without low-grade weirs in a cold climate. In addition, the study also emphasizes the importance of climate as a driver of nitrate-nitrogen loss from crop lands and ditches which is amplified by monthly precipitation variability.

Water Quality Trends and Eutrophication Indicators in a Large Subtropical Estuary: A Case Study of the Greater Charlotte Harbor System in Southwest Florida

Water Quality Trends and Eutrophication Indicators in a Large Subtropical Estuary: A Case Study of the Greater Charlotte Harbor System in Southwest Florida

Spatial-Temporal Dynamics of Adventitious Roots of Typha domingensis Pers. Seedlings Grown with Auxin/Cytokinin.

The spatial-temporal dynamics of an in vitro radicular system of Typha domingensis for the development of rhizofiltration technologies, with the potential for use as a phytotreatment of eutrophicated water, were studied for the first time in the roots of seedlings and in rhizotron systems. The effect of indole-3-acetic acid (AIA) in combination with kinetin (CIN) or 6-benzylaminopurine (BAP) on seedlings cultivated in the light and dark in three radicular systems and in a rhizotrophic regime for the screening of dynamic rhizogenic lines, by weekly allometric measurements of the length and number of roots, were studied. Inhibition of the elongation and branching velocities of roots by BAP and light was observed but CIN increased elongation and branching. In rhizotrons cultivated in light and dark conditions with different AIA/CIN ratios, isolated root explants remained inactive; however, roots attached to a meristematic base presented a significant increase in growth development, with values comparable to those of roots attached to seedlings cultivated in light without hormones. The results revealed that six adventitious rhizogenic root lines with basal meristems have the potential for use in a wide range of environmental and innovative applications in phytotreatment technologies involving eutrophicated water.

Temperature Is a Key Factor Affecting Total Phosphorus and Total Nitrogen Concentrations in Northeastern Lakes Based on Sentinel-2 Images and Machine Learning Methods

Nitrogen and phosphorus are limiting nutrients in freshwater ecosystems, and the remote estimation of total phosphorus (TP) and total nitrogen (TN) in eutrophic waters is of great significance. This study utilized machine learning algorithms based on Sentinel-2 satellite imagery for remote estimation of TP and TN concentrations in Lake Xingkai, Chagan and Songhua. Results indicate that random forest (RF) and XGBoost regression algorithms perform better. The performance of the GBDT algorithm was slightly lower than that of the RF and XGBoost regression algorithms, the BP algorithm had overfitting, and the SVR algorithm had poor fitting performance. Results showed that the TN concentration inversion model based on the RF algorithm had the highest accuracy (R2 = 0.98, RMSE = 0.09, MAPE = 19.74%). The Extreme Gradient Boosting (XGB) model also performed well, though slightly less accurately than RF (R2 = 0.97, RMSE = 0.14, MAPE = 20.67%). For TP concentration, the XGB model’s performance (R2 = 0.82, RMSE = 0.08, MAPE = 24.89%) was comparable to that of the RF model (R2 = 0.82, RMSE = 0.07, MAPE = 29.55%). The RF algorithm was applied to all cloud-free Sentinel-2 satellite images of these typical lakes in northeastern China during the non-glacial period from 2017 to 2023, generating spatiotemporal distribution maps of TP and TN concentrations. Between 2017 and 2023, TP concentrations in Lake Xingkai, Chagan and Songhua showed increasing, decreasing, and initially decreasing then increasing patterns, respectively. A positive correlation between temperature and TP concentration was observed, as higher temperatures enhance biological activity. In contrast, a negative correlation was found with TN concentration, as higher temperatures promote phytoplankton growth and reproduction. This study not only offers a new method for monitoring eutrophication in lakes but also provides valuable support for sustainable water resource management and ecological protection goals.

Water quality and eutrophication status of the Zarivar Wetland (Iran)

Wetlands are critically impacted by a variety of pollutants, primarily due to their position at the terminus of both surface and subsurface water flows. This study aims to assess the eutrophication status of Zarivar Wetland, situated in Kurdistan Province, Iran. To evaluate the eutrophication levels, the research employed the Iranian Water Quality Index for Surface Water Resources-Conventional Parameters (IRWQISC) and the Carlson’s Trophic State Index (TSI) during two sampling periods in July and September 2021. The findings indicate that in July, the wetland exhibited an upper-mesotrophic condition, with an average Carlson index value of 52.2, while in September, it transitioned to both upper-mesotrophic and eutrophic conditions, reflected by an average Carlson index value of 60.17. The zoned map of the eutrophication index identified domestic sewage from Marivan city as a significant contributor to elevated eutrophication levels in the southeastern region. Additionally, runoff from irrigated agricultural lands, orchards, and domestic wastewater from surrounding villages contributed to heightened eutrophication in the northeastern and eastern areas of the wetland. A comparative analysis of water quality between July and September 2021 revealed IRWQISC values ranging from 3.57 to 9.72 in July and from 2.63 to 4.72 in September, categorizing them as relatively good and good, respectively. To safeguard Zarivar Wetland, it is recommended to implement measures that prevent livestock waste discharge into the wetland, manage urban and rural sewage systems, control agricultural runoff, and optimize fertilizer application practices.

Seasonal agricultural activities and monsoon shifts drive fluctuations in nitrogen levels in eutrophic coastal waters: A case study of Xiangshan Bay, China.

Xiangshan Bay, one of China's most eutrophic semi-enclosed bays, was studied to examine the seasonal distributions of salinity, temperature, nutrients, and nitrate isotopes (δ15N and δ18O) to elucidate seasonal variations in nitrate sources and the key factors driving nitrogen level fluctuations. Based on nitrate δ15N (6.1-8.9‰) and δ18O (0-5.7‰) values, the primary nitrogen sources in Xiangshan Bay were identified as domestic sewage and agricultural runoff, influenced by seasonal agricultural activities and monsoon-driven Changjiang Diluted Water (CDW) dynamics. Nitrate levels peaked in autumn (53.1±1.6μmol/L), due to intensive agricultural activity and strong CDW intrusion driven by the northeast monsoon. Conversely, the southwest monsoon in summer, coupled with higher nitrogen uptake due to warmer temperatures and increased light availability, resulted in the lowest nitrate levels (35.2±5.4μmol/L). In winter, reduced nitrate inputs were observed, reflecting minimal agricultural activity and weaker Changjiang discharge. Differences in nitrate levels between the upper and lower bay were attributed to weaker mixing and stronger local inputs in the upper bay.

Selective removal of microcystin from eutrophic water by a nanobody-metal hybrid photocatalyst

Selective removal of microcystin from eutrophic water by a nanobody-metal hybrid photocatalyst

Mechanism of electrochemical oxidation of gold surfaces in a novel cobalt(II)-glycine-thiosulfate leaching system: An electrochemical experiments and DFT study

The thiosulfate gold leaching system is a promising alternative to cyanide gold leaching because of its low cost, environmental friendliness, and selectivity for gold ore. However, in the traditional thiosulfate leaching gold system, copper(II)–ammonia–thiosulfate (Cu2+–NH3–S2O32-), copper ions increase the consumption of thiosulfate, and excessive ammonia causes water eutrophication and other problems. Therefore, this paper investigated the redox mechanism of gold electrodes in the cobalt(Ⅱ)-glycine-thiosulfate (Co2+-Gly-S2O32-) composite system by electrochemical techniques. The reaction on the surface of the gold electrode was inferred by CV, and the anodic oxidation of the gold electrode was studied by LSV, i-t, and thermodynamic and kinetic parameters obtained from Tafel plots and kinetic parameters obtained from EIS. Finally, the products on the surface of the gold electrode were analyzed by SEM, AFM, FT-IR, and XPS. In addition, the oxidation mechanism was discussed by quantum chemical calculation using DFT method. The results show that thiosulfate concentration does not alter the oxidation mechanism but affects the kinetic process. High concentration of thiosulfate favors the oxidation tendency of gold, therefore, the concentration of thiosulfate should not be too low. In addition, when additional driving force (high potential) is provided will favor the oxidation of S0 and reduce the hindrance to the oxidation of the gold surface. Meanwhile, we also obtained a model of the electrochemical oxidation mechanism of the gold surface.

Microbial community assembly and co-occurrence patterns in Sanmen bay: A comparative analysis before and after nuclear power plant operation.

The limited availability of historical data has resulted in the ongoing debate regarding the short-term effects of thermal discharge from nuclear power plants (NPPs) on microbial communities, including both prokaryotes and microeukaryotes. This study focused on the co-occurrence patterns, assembly processes, and community functions in the eutrophic coastal waters of Sanmen Bay (SMB) before and after NPP operation. Gammaproteobacteria and Alphaproteobacteria were the dominant prokaryotic taxa, while Dinoflagellates consistently maintained their prevalence in SMB. This suggests that short-term thermal discharge does not significantly alter the composition of microbial communities. The co-occurrence networks were primarily composed of Gammaproteobacteria, Alphaproteobacteria, Dinoflagellates, Diatoms, and Cryptophyta, with similar network topological properties across sampling groups. Homogeneous selection and dispersal limitation were the main mechanisms that controlled the assembly of microbial communities. Homogeneous selection was more significant for prokaryotes, while dispersal limitation was the dominant factor in microeukaryotes, irrespective of a thermal discharge. Prokaryotic β-diversity and nutrients showed substantially positive effects on the functional potential of the prokaryotic community. The findings indicate that short-term thermal discharge from the NPP, as long as they do not cause a significant overall temperature increase in the bay, are unlikely to impact the microbial communities within the coastal bay ecosystem.

Chromium, tungsten and vanadium sediment-porewater geochemistry under oxic and anoxic redox conditions: Implication for their remobilization.

Global chromium (Cr), tungsten (W), and vanadium (V) cycles are emerging concerns due to their toxicities to ecosystems. However, a comprehensive understanding of their geochemical reactions and controls at the sediment-water interface remains largely unknown. This knowledge gap hinders the assessment of their potential remobilization in Earth's surface environments threatened by hypoxic conditions. We collected pore water and sediment samples from the undisturbed Castle Lake, situated in the Klamath-Siskiyou Mountains of northern California, USA, to investigate the geochemical controls responsible for the fixation and release of Cr, W, and V under redox transitions from oxia to anoxia during early diagenesis. The results show that, under oxic conditions, authigenic Cr, W, and V ratios in porewater account for approximately 4.7%, <0.1%, and<0.1%, respectively, whereas their ratios display around ten times increase under anoxic conditions with average values of 62.4% for Cr, 4.1% for W, and 1.1% for V. Our combined thermodynamic calculation and diagenetic analyses show that the sequestration and release of Cr, W, and V are intimately associated with Fe cycle under anoxic conditions. In contrast, under oxygenated conditions, only Cr and V geochemical behaviors are significantly affected by Fe cycle, while the adsorption of W to Fe minerals is probably inhibited by dissolved organic matter. Furthermore, we suggest that the Cr, W, and V pollution could become significant in coastal and inland water areas where redox conditions oscillate between oxia and anoxia, with intensified water deoxygenation, acidity, and eutrophication.

Distribution and Conservation Status of Pylaiella littoralis (L.) Kjellm., nom. cons. (Ectocarpales, Heterokontophyta) in the Northern Black Sea Region

A new locality of &lt;i&gt;Pylaiella littoralis&lt;/i&gt; has been identified in the coastal marine waters off the Cape Martyan Reserve (Southern Coast of Crimea, the Black Sea). In the Northern Black Sea region, which covers the coastal area from the Danube Delta to the Northern Caucasus, this species is considered a rare element of the natural flora with decreasing populations. However, in the Mediterranean Sea, &lt;i&gt;P. littoralis&lt;/i&gt;, first recorded in 1960, is categorized as an alien species. Since the Black Sea regional conservation documents emphasize the Caspian-Mediterranean range of &lt;i&gt;P. littoralis,&lt;/i&gt; we analyzed original publications for a period of more than two hundred years. Together with the results of our own observations, it showed that the species does not usually form abundant growths and thickets in the Northern Black Sea region, but it is widespread enough. &lt;i&gt;Pylaiella littoralis&lt;/i&gt; was first identified in the Northern Black Sea (and in the Black Sea in general) in the early 1930s in Odesa Bay as an alien species, which was later overlooked. The erroneous idea about the occurrence of &lt;i&gt;P. littoralis&lt;/i&gt; in the Caspian Sea before the launch of the Volga-Don Canal (1952) arose due to an inaccuracy made in the 1950s in the succession of citations that began with a publication from 1800. We believe that this multizonal eurybiont was introduced by sea transport through the straits into the Mediterranean and Black Seas almost simultaneously - around the early 1930s. After the end of the lag-phase of invasion, a rapid expansion of the species occurred. This could have been triggered by the intensification of marine traffic, climatic changes or progressive eutrophication of waters. By the 1960s, &lt;i&gt;P. littoralis &lt;/i&gt;had colonized the coastal areas of both seas, and through the canal, it penetrated into the previously isolated Caspian Sea, where it had also spread widely by the early 1970s. Thus, &lt;i&gt;P. littoralis&lt;/i&gt; is also a naturalized alien species in the Northern Black Sea region as well as in the entire Black Sea and the Caspian Sea. Its introduction, and rapid, widespread distribution did not result in a transformation of the native phytocenoses and biotopes of the Northern Black Sea region. However, the erroneous inclusion of &lt;i&gt;P. littoralis&lt;/i&gt; in the rarity fraction of the natural flora of the region and the unreasonable conservation measures are obvious. KEY WORDS: Northern Black Sea region, macrophytobenthos, &lt;i&gt;Pylaiella littoralis&lt;/i&gt;, distribution, conservation, biological invasion, alien species

Vertical mass exchange in wetland flows with shear layers

Vertical mass exchange hugely changes the solute distribution with the effects of shear layers and multiple-scale turbulent vortices, and then impacts the effectiveness of wetlands in purifying eutrophic water bodies. This study aims to investigate vertical mass exchange mechanisms in wetland systems and to provide theoretical guidance for optimizing the purification efficiency of wetland water quality. We simulate solute diffusion behaviors originating from a continuous point source with vegetated shear layers and bed absorptions through the adopted numerical simulation method, random walk method. The simulated results mainly contributed to three findings: (1) Vegetation features (density and height) inhibit solute diffusion, resulting in a prolonged steady time required for the cross-sectional concentration to reach equilibrium. (2) There is a threshold for the bed absorption probabilities to impact near-bed concentration distribution, that is the 10% absorption probability, over which the variation of bed absorption has few effects on the solute concentration. (3) The shear layer at the top of vegetation promotes vertical mass exchange while preventing solutes above the wake zone from being absorbed by the bed. In practice, the dual effects of submerged vegetation on vertical mass exchange should be comprehensively considered to ensure the effective functioning of wetland ecosystems.

Eutrophication exacerbated organic pollution in lakes across China during the 1980s-2010s

Lakes are vital sources of drinking water and essential habitats for humans and various other living organisms. However, many lakes face organic pollution due to anthropogenic disturbance and climatic influence, and the spatiotemporal changes of organic pollution in lakes over a large area are still unclear. Based on three monitoring datasets of chemical oxygen demand (COD) in 390 lakes, this study demonstrated the apparent spatiotemporal differences of organic pollution in lakes during the 1980s-2010s and the effects of water eutrophication and salinization. Throughout China, lake organic pollution showed a general spatial trend of being more severe in the north compared to the south. This pattern is reflected in the positive linear correlations between in-situ COD concentrations and lake latitude, observed in both the 1980s (p < 0.05) and the 2010s (p < 0.01). In terms of spatial differences, the influence of total nitrogen concentrations increased from 0.27% in the 1980s to 35.24% in the 2010s. Moreover, with increasing human activity, 78.31% of the studied lakes (N = 83) showed increasing COD concentrations during the 1980s-2010s. In addition, the logarithmic dissolved organic carbon concentrations were linearly correlated with log water conductivities (Pearson's r = 0.49, p < 0.01), suggesting that lake expansion would attenuate organic pollution in saline lakes through dilution effects. These results are valuable for understanding the spatiotemporal dynamics of organic pollution and are crucial for effective management of organic pollution in different lakes.

Probable Record of Paleocene - Eocene Thermal Maximum in Southwestern Nigeria: Indications from Nannofossils of FA-1 Borehole, Eastern Benin Basin.

The Paleocene – Eocene Thermal Maximum (PETM) interval has been reported in several calcareous nannofossil studies from Paleogene basins around world including the Southern Tethys basins of North Africa. The Southern Tethys basins are believed to be connected to the Eastern Benin Basin through the Trans – Saharan Seaway during the Paleogene. Based on these reports, we carried out a biostratigraphic and paleoclimatic analyses of the calcareous nannofossils recovered from 25 ditch cutting samples in the FA-1 borehole to investigate possible record of the PETM in the Eastern Benin Basin, Southwestern Nigeria. The samples yielded characteristic Paleocene – Eocene calcareous nannofossils species (Coccolithus pelagicus, Coccolithus formosus, Chiasmolithus solitus, Sphenolithus moriformis, Pontosphaera plana, Pontosphaera multipora, Lophodolithus mochioporus, Lophodolithus nanscens, Neochiastozygus perfectus and Zeugrhabdotus sigmoides) and the Maastrichtian species, Arkhangeskiella cymbiformis. The assemblages allow the recognition of CC 22 (Maastrichtian) and NP 4 – NP 6 (early – late Paleocene) nannofossil zones. The relatively abundant occurrences of the genus Coccolithus and Sphenolithus in the carbonate interval of borehole suggest prevailing oligotrophic, warm water condition. The barren interval succeeding the peak nannofossil abundance at sample 159 m coincides with the onset of continuous clastic sedimentation in the FA-1 borehole. This is believed to have resulted from the shoaling of the Calcite Compensation Depth (CCD) and increased clastic input occasioned by the climatic and ocean water perturbations of the PETM interval. The emergence of the genus Pontosphaera (Pontosphaera plana and Pontosphaera multipora) at depth 87 m above the barren interval suggest a return to cooler, mesotrophic to eutrophic water condition after the drastic temperature rise and oligotrophic waters of the PETM. Key-words - Calcareous nannofossils, Paleocene - Eocene, Benin Basin, Thermal Maximum.