Oceanographic Research in the Thermaikos Gulf: A Review over Five Decades

The Thermaikos Gulf (TG) is a semi-enclosed, river-influenced, marine system situated in the eastern Mediterranean Sea, sustaining both urban coastal regions and ecologically preserved natural areas. Facing a plethora of environmental and anthropogenic pressures, the TG serves as a critical nexus where human activities intersect with marine ecosystems. The quality and health of the TG’s marine environment are tightly linked to the socioeconomic activities of the coastal communities comprising approximately 1.5 million inhabitants. The main features of the TG’s environmental dynamics and ecological status have been scrutinized by dedicated research endeavors during the last 50 years. This review synthesizes the seminal findings of these investigations, offering an evaluation of their contribution to research, their present collective impact, and their trajectory toward the future. A severe deterioration of the TG’s environmental quality was detected in the 1970s and 1980s when the treatment of urban wastewater was completely absent. A steady trend of recovery was observed after the 1990s; however, so far, the goal of a “good environmental state” mandated by national legislation and European directives has not been achieved. A clear reduction in research was detected after 2010, associated with the recession of the Greek economy, following the “golden period” for research in the TG from the mid-1990s until the late 2000s. The most important research gaps and uncertainties are discussed, while specific targeted recommendations for the improvement of monitoring and understanding of the physical, biochemical, and ecological state of the gulf are provided: (i) increase in permanent observational stations (temporally and spatially); (ii) inclusion of all major environmental parameters; (iii) monitoring of the quantity and quality of all land-originated freshwater discharges; (iv) monitoring and management of important aspects of the marine environment that have received minimal attention in the past (e.g., coastal erosion, plastic pollution); (v) development of accurate prediction tools (e.g., numerical techniques) to support first-level responders and efficient management; (vi) establishment of a supervising public entity that would support the holistic overview and management of the entire TG. These suggestions are directed at overcoming the existing uncertainties in the knowledge of the TG, safeguarding its ecological integrity and its role as a crucial link t