Hydrocarbons in seawater: Sources, fate, impacts, and remediation strategies

Hydrocarbon contamination in marine environments poses a significant global environmental challenge, impacting ecosystems, human health, and economic activities. The present review provides a comprehensive overview of hydrocarbons in seawater, addressing their diverse sources, complex fate and transport mechanisms, ecological and toxicological impacts, and various remediation strategies. Both natural seepages from geological formations and a wide array of anthropogenic inputs are discussed as primary contributors to marine hydrocarbon burdens. Anthropogenic carbon inputs include large-scale accidental oil spills, chronic operational discharges from shipping and offshore platforms, industrial effluents, and diffuse urban runoff carrying petrogenic and pyrogenic hydrocarbons, during the past 50 years. In the sea, hydrocarbons undergo a series of interconnected physical, chemical, and biological transformations that mediate their persistence, bioavailability, and spatial distribution. The specific environmental conditions, such as temperature, nutrient availability, and microbial community composition, significantly influence the rate and extent of these natural attenuation processes. The ecological consequences range from acute lethal impacts causing immediate mortality in marine organisms to chronic sublethal effects on reproduction, growth, immune response, and behavior across a wide range of taxa, from plankton to marine mammals. Furthermore, long-term ecosystem disruptions, including habitat degradation of vital coastal areas, such as mangroves and coral reefs, and bioaccumulation within the food web, pose serious threats to ecosystem health and biodiversity. To mitigate these adverse effects, a range of remediation strategies has been developed and implemented; their mechanisms, effectiveness in various scenarios, inherent limitations, and potential secondary environmental considerations are explored in this review. Emphasis is placed on the importance of integrated approaches that combine rigorous prevention measures, rapid and effective response protocols during spill events, and sustainable, environmentally sound long-term remediation techniques. Understanding the intricate interplay between the sources, transformations, impacts, and potential solutions for hydrocarbon contamination is crucial for developing robust management plans and safeguarding the long-term health and resilience of marine ecosystems.