The Rio de la Plata and the adjacent Atlantic Ocean are covered by the most significant amount of environmental cooperation in the Southwest Atlantic. There are joint agreements between Uruguay and Argentina and their institutions, and there is a long history of bi-national fisheries management and maritime traffic organizations. However, these agreements do not cover many other activity sectors that come under different jurisdictions and regulatory instruments. Documentary sources spanning 30 years have been used to describe the spatial extent and evolution of more than 30 activities (grouped into main clusters), as well overlaps and conflicts between them. The higher number and diversity of activities were found in the coastal zone, while fisheries and spatially-defined management measures were dominant in common waters and on the continental shelf. Transport/navigation and communication cables were the most common clusters along surface and sub-bottom linear routes, respectively. The different and overlapping use of the water column and across multiple jurisdictions were the cause of sectoral conflicts, such as between fisheries-transport or fisheries-submarine cables. Under a sector-by-sector analysis, and in the absence of a comprehensive planning environment, many of these conflicts are resolved, at best, by legal proceedings. There have been significant advances in the governance and spatial organisation of fisheries and transport, while progress in conservation and infrastructure has not occurred at the same speed or by considering a broader vision of the system. Addressing the existing and increasing interferences or unresolved conflicts emphasises the need to consolidate multilevel governance frameworks and opportunities in order to advance in marine spatial planning in the Southwest Atlantic Ocean.
