Bioremediation in Coastal Marine Ecosystems

Harnessing Nature’s Microbes and Plants to Clean the Sea

As coastal regions face growing threats from pollution—whether from agricultural runoff, industrial discharge, sewage, pharmaceuticals, microplastics or oil spills—biotechnological interventions are increasingly viewed as sustainable lifelines for marine remediation. A timely new review by Adenike A. Akinsemolu & Helen N. Onyeaka, published in Applied Sciences in June 2025, offers a comprehensive evaluation of microbial and plant-based strategies to tackle organic pollutants in coastal and marine environments (MDPI).

This post explores the findings of their review and situates them within the broader landscape of biostimulation, bioaugmentation, nanotech-enhanced uptake, and phytoremediation, examining benefits, limitations, and prospects for coastal ecosystem recovery.

1. Coastal Marine Pollution: A Critical Challenge

Coastal marine environments—including estuaries, wetlands, mangroves, seagrass meadows, and shallow coastal waters—act as dynamic interfaces between land and sea, providing crucial services such as water purification, carbon sequestration, habitat provision and food sources (MDPI).

However, these ecosystems are increasingly burdened by organic contaminants:

• Persistent organic pollutants (POPs) such as PCBs, certain pesticides and industrial chemicals
• Pharmaceuticals and personal-care residues entering via sewage and runoff
• Polycyclic aromatic hydrocarbons (PAHs) associated with oil spills and combustion by-products
• Microplastics and plastic-associated chemicals that accumulate and act as pollutant vectors
• Agricultural agrochemicals, including herbicides and fertilisers leaching into coastal zones (MDPI)

These pollutants can bioaccumulate, disrupt endocrine systems, damage reproductive health, disturb microbial community structure, and threaten biodiversity and human health. The complexity and persistence of many pollutants demands remediation beyond conventional physical and chemical treatments.

2. Biotechnology as an Eco‑Friendly Alternative

Akinsemolu & Onyeaka emphasise that biotechnology—in particular, microbial and plant-based techniques—offers a sustainable, cost-effective, and biologically driven alternative to traditional remediation methods (MDPI).

These approaches leverage:

• Microorganisms: bacteria, fungi, algae, archaea
• Photosynthetic coastal plants and microalgae capable of biosorption and pollutant uptake
• Modern tools: nanotechnology, bio-surfactants, electrochemistry, synthetic biology and genetic enhancement (bohrium.com, MDPI)

Importantly, for coastal applications, these technologies minimise habitat disruption and avoid secondary chemical pollution.

3. Bioremediation Strategies and Mechanisms

3.1 Bioaugmentation

This involves introducing specialised pollutant-degrading microbes—often bacteria, fungi or yeast—to boost removal of targeted contaminants. Examples include oil-degrading bacterial consortia or engineered yeasts targeting pharmaceutical residues (MDPI, ResearchGate).

3.2 Biostimulation

Here, native microbial populations are stimulated—often via nutrient amendments (nitrogen, phosphorus) or oxygenation—to increase degradation rates. Notably, applications after the Exxon Valdez spill showed doubling of hydrocarbon biodegradation by fertilising shoreline soils (en.wikipedia.org).

3.3 Nanotechnology‑Assisted Uptake

The review highlights emerging techniques where nanomaterials, such as nano‑iron, graphene composites or biosurfactants, are used to enhance bioavailability and uptake of pollutants by plants or microbes, improving remediation rates in saline environments (MDPI, bohrium.com).

3.4 Phytoremediation Techniques

Complex coastal plants (e.g. mangroves, seagrass) and microalgae offer a suite of mechanisms including:

• Phytoextraction: uptake and accumulation of contaminants
• Phytostabilisation: immobilising pollutants in root zones
• Phytofiltration: filtering pollution from water column through roots or submerged leaves
• Phytodegradation/Phytovolatilisation: enzymatic breakdown or gaseous release of certain compounds (MDPI)

While phytoremediation is more established for heavy metals, its potential for organic pollutant removal—especially when combined with microbial inoculation—is gaining interest.

4. Highlights from the June 2025 Review

4.1 Scope and Methodology

Akinsemolu & Onyeaka’s review synthesised peer-reviewed studies (2010–2025) to map biotechnological interventions addressing POPs, pesticides, pharmaceuticals, PAHs and microplastic‑associated pollutants in coastal ecosystems (MDPI).

4.2 Key Findings

• Bioaugmentation and biostimulation are among the most widely reported and effective methods for hydrocarbon and pesticide remediation.
• Phytoremediation, while promising, is underutilised in organic pollutant contexts—most research focuses on inorganic pollution in freshwater settings. The authors call for more studies combining plants with microbial/engineered supports (MDPI).
• Nanotechnology and biosurfactants are emerging enablers, improving pollutant solubility and uptake by microbes or plants, especially in saline and dynamic coastal conditions (MDPI, bohrium.com).

4.3 Research Gaps & Recommendations

Notable gaps include:

• Limited field-scale validation in diverse coastal settings (e.g. estuaries, salt marshes, mangroves)
• Underexploited potential of microalgae or cyanobacteria-based phytoremediation in saline water
• Need for long-term monitoring of ecological effects and biomagnification risks
• Requirement for multi-disciplinary studies integrating genetic engineering, electro-biosensors, and smart delivery systems to optimise biological efficacy in situ (MDPI, ResearchGate).

5. Broader Context: What Other Research Shows

5.1 Oil-Spill Degradation & Environmental Conditions

Bacosa et al. (2022) review how abiotic parameters—temperature, nutrient availability, oxygenation, salinity, shoreline energy—govern hydrocarbon biodegradation in coastal marine environments. Enhanced microbial diversity and sunlight exposure accelerate degradation, whereas high oil concentration and low oxygen slow it down (MDPI).

5.2 Marine Heavy-Metal and Organic Detoxification

Separate studies highlight biosorption, bioaccumulation, biotransformation, and bioreduction by marine bacteria, fungi, microalgae and yeast, showing effective removal of heavy metals and persistent organics in bay and estuary sediments (pmc.ncbi.nlm.nih.gov).

5.3 Nanotech Biosurfactants and Green Materials

Other authors emphasise green-based nanotechnologies (e.g. nano-iron, graphene composites) to improve pollutant degradation or microbial uptake—a theme echoed in the review by Akinsemolu & Onyeaka (bohrium.com, sciencedirect.com).

6. Techniques in Practice: Case Studies and Use Scenarios

6.1 Biostimulation for Oil Impacted Beaches

An oil-contaminated shoreline is treated with nutrient fertiliser to stimulate indigenous hydrocarbon-degrading bacteria. Enhanced oxygenation and sunlight exposure accelerate microbial breakdown. Bacosa et al. report improved degradation rates where these conditions align (MDPI).

6.2 Bioaugmentation with Specialized Microbial Consortia

A carefully formulated bacterial or fungal consortium is introduced to estuarine sediments rich in PAHs and pharmaceutical residues, accelerating removal. Laboratory studies show multi-species consortia outperform single-strain applications.

6.3 Algae and Seagrass Phytoremediation

Microalgae blooms or seagrass beds are planted to absorb pollutants. When co-inoculated with rhizosphere-enhancing microbes or nanomaterial carriers, they show enhanced removal of herbicides and antibiotics—a promising tunnel for future field trials.

6.4 Nanotech‑Enabled Delivery

Nanoparticle-encapsulated enzymes or biosurfactants are delivered via hydrogel matrices in sediments or around root zones. These materials increase the area of pollutant contact and speed enzymatic breakdown by enhancing bioavailability.

7. Advantages and Challenges: A Balanced View

☀️ Advantages

• Eco‑friendly and low-impact: biology-based, minimal chemical footprint
• Cost‑effective at scale: minimal infrastructure; relies on nature’s machinery
• Flexible applications: in situ or ex situ; suited to fragile ecosystems
• Synergistic mechanisms: combining microbes and plants enables broad-spectrum pollutant targeting
• Public and regulatory appeal: green (or blue) remediation attracts support from stakeholders

⚠️ Challenges

• Environmental variability: salt levels, temperature, pH, nutrient status, and tidal dynamics affect efficacy
• Slow processes: bioremediation and phytoremediation can take weeks to months depending on pollutant complexity
• Pollutant accessibility: hydrophobic compounds or bound residues may be inaccessible without pre-treatment
• Ecological trade‑offs: risk of introducing non‑indigenous microbes or disrupting native community structures
• Scalability and monitoring: field-scale applications remain limited; long-term efficacy and ecosystem impacts need validation

The June 2025 review explicitly calls for more field-based experiments, ecological risk assessments, and integration with advanced biotechnology tools to address these challenges (MDPI).

8. Synergies: Coastal Bioremediation + Molecular Tools

Integrating microbial, plant-based and nanotechnological strategies offers a powerful toolkit, especially in complex or sensitive coastal ecosystems:

• Sequential bioremediation: begin with bioaugmentation or biostimulation to degrade bulk pollution; then deploy phytoremediation to polish residuals
• Microbial–plant co-cultivation: rhizosphere engineering using microbial inoculants to support pollutant uptake by seagrass or macroalgae
• Nanohydrogel carriers: deliver enzymes, nutrients, or microbial spores precisely to polluted zones
• Genetically enhanced organisms: engineered microbes or algae tuned for specific organic targets, with built-in biosafety constraints

9. Implications for Environmental Practitioners & Policymakers

Stakeholders engaged in coastal restoration and remediation should consider:

• Building holistic remediation programmes that combine traditional clean‑up methods with biotechnology
• Conducting site-specific pilot studies to adapt bioremediation strategies to local environmental conditions and pollutant profiles
• Collaborating across disciplines—marine biology, microbiology, nanotechnology, environmental engineering—to design resilient cleanup systems
• Securing long‑term monitoring protocols to verify ecosystem recovery and detect unintended impacts
• Advocating for policy frameworks that enable field deployment of green biotech solutions while ensuring ecological safety

10. Future Directions & Research Opportunities

Building on the insights from Akinsemolu & Onyeaka’s review, key avenues for innovation include:

• Scaling green phytoremediation: expanding microalgal or saltmarsh plant deployment for organic contaminants, paired with microbial inoculation
• Smart delivery systems: nanogel‑based carriers precisely targeting pollutant hotspots
• Synthetic biology for marine microbes: engineered strains able to degrade micropollutants with minimal ecological footprint
• Sensor-enabled monitoring: using biosensors to track pollutant breakdown in real time and adapt remediation dynamically
• Community-based restoration: involving coastal populations in low-cost bioremediation projects using local plant species and native microorganisms

Conclusion

Bioremediation—especially as articulated in Akinsemolu & Onyeaka (June 2025)—offers a scientifically robust and ecologically attuned pathway for restoring coastal and marine ecosystems besieged by organic contamination (MDPI, ResearchGate). By drawing upon bioaugmentation, biostimulation, phytoremediation, and nanotech‑assisted uptake, the field has positioned itself as a keystone in sustainable remediation.

As pollution challenges intensify, these biotechnologies empower us to align remediation with restoration—reviving seas not through harsh chemicals, but by harnessing the living organisms that call the coast home.

References

• Akinsemolu, A. A., & Onyeaka, H. N. (2025). Harnessing Biotechnology for the Remediation of Organic Pollutants in Coastal Marine Ecosystems. Applied Sciences, 15(12), 6921. (MDPI)
• Bacosa, H. P. et al. (2022). From Surface Water to the Deep Sea: Factors Affecting the Biodegradation of Spilled Oil. Journal of Marine Science & Engineering. (MDPI)
• Wikipedia. Bioremediation of Oil Spills (overview on mechanisms). (en.wikipedia.org)
• Reviews on marine heavy‑metal bioremediation and green nanotech biosurfactants. (pmc.ncbi.nlm.nih.gov, bohrium.com, ResearchGate, sciencedirect.com)

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