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Open research questions in Aquatic Ecosystems and Phytoplankton Dynamics

35 unresolved questions extracted from the limitations and future-work sections of 1,034 Aquatic Ecosystems and Phytoplankton Dynamics papers in our library. Each links back to the study that raised it.

What the literature leaves open

  • To evaluate the pollution status of the lakes, the single factor pollution index (STP) analysis was conducted on the profile sediments, while the Nemerow integrated pollution index (F) was applied to surface sediments, as they can reflect the recent pollution status of the lakes. Based on F values, Xianghu Lake, Qianhu Lake and Aixihu Lake were all classified as heavily polluted (Table 2), with Qianhu Lake showing the highest level (F ≥ 2.26), followed by Aixihu Lake (F ≥ 2.04) and Xianghu Lake (F ≥ 1.92) (Fig. 6a and Table 2). According to the STP index, the surface sediments of profiles XH2 and XH3 in the Xianghu Lake were moderately polluted (Fig. 6a and Table 2), with STP values consistently exceeding 1.0 within the 0–10 cm depth (Fig. 6a and Table 2). Profile XH1 exhibited the most severe pollution, with the pollution peak concentrated at 8–12 cm (STP >3.0) (Fig. 6a and Table 2). In Qianhu Lake, the STP values of the three profiles (2.20–3.88) indicated severe pollution (Fig. 6b and Table 2), with QH1 and QH3 showing peak values (STP >2.0) at 4–8 cm depth (Fig. 6b and Table 2), and QH2 at 10–20 cm depth (Fig. 6b and Table 2). In Aixihu Lake, profiles AXH1 and AXH3, which had heavy pollution, exhibited their highest STP values at the surface and decreased with depth (Fig. 6c and Table 2). At the same time, AXH2 showed moderate pollution at the surface and a heavy pollution peak at 5–10 cm depth (Fig. 6c and Table 2). Page 13/27 Table 2 The pollution indices of profile sediments in the urban lakes from Nanchang Sediment profile STP (pollution grade) F (pollution grade) XH1 XH2 XH3 QH1 QH2 QH3 AXH1 AXH2 AXH3 1.40 (moderate) ~ 3.53 (heavy) 1.28 (moderate) ~ 2.79 (heavy) 1.40 (moderate) ~ 2.67 (heavy) 2.20 (heavy) ~ 3.29 (heavy) 2.22 (heavy) ~ 3.79 (heavy) 2.21 (heavy) ~ 3.88 (heavy) 1.79 (heavy) ~ 2.60 (heavy) 1.47 (heavy) ~ 2.63 (heavy) 2.06 (heavy) ~ 3.65 (heavy) 2.91 (heavy) 1.92 (heavy) 2.46 (heavy) 2.64 (heavy) 2.75 (heavy) 2.26 (heavy) 2.63 (heavy) 2.33 (heavy) 2.04 (heavy) Note: STP and F denoted single factor pollution index and Nemerow integrated pollution index, respectively. In summary, the sediments of urban lakes in Nanchang generally suffer from heavy phosphorus pollution, underscoring the need for comprehensive and targeted mitigation strategies to alleviate current pollution levels and prevent further deterioration. Given that Xianghu Lake, Qianhu Lake and Aixihu Lake share similar land-use patterns in their surroundings, mitigation should include optimizing urban planning, strengthening the construction and maintenance of wastewater treatment facilities and improving farmland irrigation and drainage systems.

    Chemical speciation, source apportionment, and pollution assessment of phosphorus in sediments from typical urban lakes in Southern China · 2026 · DOI

  • The coupled EFDC machine learning-remote sensing framework was calibrated and validated using data from a single subtropical reservoir system with specific thermal stratification and cyanobacteria community characteristics. Transferability of the calibrated parameter set (cyanobacteria growth rate 8 d⁻¹, nitrification rate 1 d⁻¹, nutrient cycling rates 0.001–0.15 d⁻¹) to other data-scarce reservoirs with different morphometry, nutrient loading patterns, and phytoplankton composition has not been empirically tested.

    Enhancing reservoir water quality simulation through machine learning-driven remote sensing integration with EFDC: a coupled framework for eutrophication management in data-scarce regions · 2026 · DOI

  • Water surface level abstraction in the natural river-reservoir system is subject to inherent uncertainty from secondary currents and complex boundary geometries at inflow junctions. While log-law vertical profile parameterization was applied to estimate inflow velocity distributions, the simplified one-dimensional stage-discharge assumptions at HK and RX inflow boundaries remain inadequately constrained, particularly during high-flow events when three-dimensional secondary flow effects are pronounced.

    Enhancing reservoir water quality simulation through machine learning-driven remote sensing integration with EFDC: a coupled framework for eutrophication management in data-scarce regions · 2026 · DOI

  • The study acknowledges that advanced calibration strategies such as acoustic Doppler current profiler (ADCP)-based velocity vector matching or adjoint-based data assimilation are absent from the current framework. Implementation of ADCP measurements at inflow cross-sections (particularly at HK station contributing ~90% of total inflow) during high-flow events is needed to reduce boundary condition uncertainty and validate helical flow structure representation in the 3D hydrodynamic-water quality coupled model.

    Enhancing reservoir water quality simulation through machine learning-driven remote sensing integration with EFDC: a coupled framework for eutrophication management in data-scarce regions · 2026 · DOI

  • Continuous dissolved reactive phosphorus (DRP) monitoring was not available for temporal validation of simulated PO₄ dynamics across the full simulation period; validation relied on only six discrete sampling dates (r² = 0.71). High-frequency DRP monitoring at multiple reservoir depths and locations is required to robustly validate phosphorus cycling representation in machine learning-remote sensing coupled EFDC frameworks.

    Enhancing reservoir water quality simulation through machine learning-driven remote sensing integration with EFDC: a coupled framework for eutrophication management in data-scarce regions · 2026 · DOI

  • Nitrogen and phosphorus speciation into model-required fractions (refractory/labile particulate organic, dissolved organic, and inorganic forms) was based solely on literature values and iterative calibration due to limited observational data. Direct measurements of individual nitrogen and phosphorus species across the full simulation period are needed to validate the assumed partition ratios (RPOP 39%, LPOP 7%, DOP 27%, PO₄ 26% for phosphorus; RPON 35%, LPON 8%, DON 22%, NH₄⁺ 18%, NOₓ 17% for nitrogen) in subtropical eutrophic reservoir conditions.

    Enhancing reservoir water quality simulation through machine learning-driven remote sensing integration with EFDC: a coupled framework for eutrophication management in data-scarce regions · 2026 · DOI

  • While the study applies Palmer's Pollution Index and mentions the Trophic Diatom Index (TDI) and Specific Pollution Sensitivity Index (IPS), it does not actually calculate or compare results from multiple diatom indices to validate the ecological assessment.

    Limnology and Algal Bioassessment of Erin-Ijesha (Olumirin) Waterfall, Southwestern Nigeria · 2026 · DOI

  • While the paper documents algal composition and PPI values at a single waterfall site, it does not establish baseline or reference conditions for similar waterfall systems in southwestern Nigeria, limiting comparative assessment.

    Limnology and Algal Bioassessment of Erin-Ijesha (Olumirin) Waterfall, Southwestern Nigeria · 2026 · DOI

  • The study highlights the value of algal bioindicators in assessing subtle changes in water quality that may not be immediately evident from physicochemical parameters alone, but does not systematically compare the sensitivity of algal indices versus physicochemical measurements.

    Limnology and Algal Bioassessment of Erin-Ijesha (Olumirin) Waterfall, Southwestern Nigeria · 2026 · DOI

  • The increasing number of reports regarding detections of cyanobacteria and their toxins in water pose a high risk to the aquatic ecosystems and endanger public water suppliers (Sukenik & Kaplan, 2021). Managing, controlling, and treating cyanobacteria and cyanotoxins in drinking, recreational, and raw water sources are important in protecting public health, aquatic organisms, and to protect living. In preventing the formation of blooms in the environment, proper conventional treatment plants should be designed to reduce turbidity, remove intact algal cells, and reduce the levels of toxins. Also, it should be recommended that a proper plan for nutrient capture, immobilization and/or immediate repurposing be considered before certain industrial activities (e.g., mining, detergent manufacture and farming) commence full scale. Regular monitoring of water sources and public awareness regarding the economic impacts of cHABs and other HABs would be appreciated to promote precautionary measures principally when risk assessments lead to restrictions of its use. This will help in safeguarding water resources, public health, and making predictions of the occurrence of algal blooms (Schmale et al., 2019). Similarly, to help prevent the impacts of cHABs, public-health strategies should include rapid diagnosis, surveillance of exposure, infection, seafood testing, and treatment of HABrelated infections. From a community perspective in preventing the impacts of cHABs, the following strategies should be adopted. (i) To create other recreational centers to keep tourism and this will help local businesses during bloom incidence. (ii) To develop private or public programs that will provide social and economic support to temporarily unemployed workers such as fishermen. (iii) To develop educational programs that will help ethnically diverse residents to avoid exposure. For resource management measures, effective, proper, and continuous water monitoring and management approaches should be adopted to help protect consumers, animals, the public, and fisheries as well as to help prevent risks associated with cHABs. From a preventive perspective in regions where cHABs and other HABs have been connected to anthropogenic sources of nutrients, compulsory nutrient management plans will be significant to help reduce the nutrient load in the environment. In this regard sanctions and incentives must be given to ensure the compliance of nutrient management below eutrophication thresholds.

    Cyanobacteria Harmful Algae Blooms: Causes, Impacts, and Risk Management · 2024 · DOI

  • Similarly, increased irradiance in spring can promote growth of motile phytoplankton or, if radiatively driven convection occurs, more nutritious diatoms, but links between functional trait selection, trophic transfer to zooplankton and fish, and the prevalence of microbial versus classical food webs in seasonally ice‐covered lakes remain unclear.

    Winter Limnology: How do Hydrodynamics and Biogeochemistry Shape Ecosystems Under Ice? · 2021 · DOI

  • These results most likely reflect differences in the exact parameters quantified by the two methods, as the BenthoTorch does not account for variability in cell size and the presence of non-chlorophyll bearing biomass in estimating the proportion of different algal groups, and does not distinguish red algal chlorophyll from that of other algal groups.

    Comparing new and conventional methods to estimate benthic algal biomass and composition in freshwaters · 2014 · DOI

  • Natural processes of water oxygenation are not too intensive, because they are practically limited to the epilimnion layer, connected as they are with the activity of aquatic plants of the littoral and sublittoral zone (which tends to disappear in contaminated lakes) and wind energy (the effect of waving).

    Efficiency of pulverizing aeration on Lake Panieńskie · 2012 · DOI

  • The lake remains oligotrophic with productivity limited by availability of labile NP, although worrisome blooms of algae, including Anabaena flos-aquae, occurred several times during the period of record.

    Alternate States in a Large Oligotrophic Lake: A Retrospective Analysis of Nutrient Loading and Food Web Change · 2007

  • Despite reductions in atmospheric SO4(2-) deposition and resultant decreases in surface water acidity, widespread biological recovery from acidification has not yet been documented.

    Recovery of Crustacean Zooplankton Communities from Acidification in Killarney Park, Ontario, 1971–2000: pH 6 As a Recovery Goal · 2003 · DOI

  • However, as a relatively sensitive organism in aquatic ecosystems, there are relatively few studies on its toxicity, which is insufficient to comprehensively assess its environ- mental risks. The water ecological toxicity data of SCCPs is relatively scarce.

    Responses of Phaeodactylum tricornutum to short-chain chlorinated paraffins: growth inhibition, photosynthetic damage and oxidative stress · 2026 · DOI

  • Amongst the extreme events linked to warming, heatwaves are of growing concern, yet their ecological effects on the functioning of Mediterranean aquatic systems remain poorly investigated.

    Methodological design to study the effects of heatwaves on natural plankton communities from Mediterranean vulnerable ecosystems · 2026 · DOI

  • Cyanobacterial toxins (cyanotoxins) threaten aquatic ecosystems and human health, yet the factors influencing their production and distribution in freshwater remain unclear.

    Tracking Toxins: A Pilot Investigation of Cyanotoxins in North-Central Tennessee’s Surface Waters and Wells · 2026 · DOI

  • Future research should focus on elucidating structure– activity relationships, optimizing extraction and purification methods, and evaluating ecological safety to support practi- cal applications of the floating-leaf pondweed.

    Insights into the Floating-Leaf Pondweed Potamogeton natans L.: Ecological Significance and Bioactive Compounds for Sustainable Aquatic Management · 2026 · DOI

  • The study is limited to a single waterfall site; broader spatial sampling across multiple waterfalls in southwestern Nigeria is needed to determine if patterns of moderate organic pollution and algal assemblage composition are regionally representative.

    Limnology and Algal Bioassessment of Erin-Ijesha (Olumirin) Waterfall, Southwestern Nigeria · 2026 · DOI

  • The integrated assessment framework combining water chemistry, diurnal patterns, and biological indicators is described as robust, but its applicability to other tropical waterfall systems or freshwater ecosystems is not demonstrated.

    Limnology and Algal Bioassessment of Erin-Ijesha (Olumirin) Waterfall, Southwestern Nigeria · 2026 · DOI

  • The paper mentions that conditions reflect low-intensity human activities such as tourism and localized runoff but does not quantify the specific contribution of different pollution sources or establish source-receptor relationships.

    Limnology and Algal Bioassessment of Erin-Ijesha (Olumirin) Waterfall, Southwestern Nigeria · 2026 · DOI

  • The study identifies moderate organic pollution at Erin-Ijesha Waterfall attributed to tourism activities and surface runoff, but lacks temporal monitoring data to assess seasonal variation and long-term trends in water quality and algal community dynamics.

    Limnology and Algal Bioassessment of Erin-Ijesha (Olumirin) Waterfall, Southwestern Nigeria · 2026 · DOI

  • However, the long-term effectiveness of restoration remains uncertain, so the monitoring programme will continue to address still unresolved questions, particularly to distinguish between seasonal and anthropogenic effects on ecosystems.

    Restoration of high-mountain lakes: effects on nutrient concentrations and biological communities · 2025 · DOI

  • In this review, we summarize what is known about the Great Lakes during their 3–6 months of winter and identify key open questions about the physics, chemistry, and biology of the Laurentian Great Lakes and other large, seasonally frozen lakes.

    The Changing Face of Winter: Lessons and Questions From the Laurentian Great Lakes · 2021 · DOI

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35 open questions have been extracted from the limitations and future-work passages of 1,034 Aquatic Ecosystems and Phytoplankton Dynamics papers in our library. Each one below links back to the study that raised it, so you can read the original claim in context.

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