A Two-Ocean Bouillabaisse

Imagine a world where engineers planned to use hydrogen bombs to blast a path between oceans—a visionary project that promised to reshape global trade while threatening to scramble the very biology of our planet's oceans. This was no science fiction scenario, but a serious U.S. government proposal in the mid-1960s to create a sea-level canal connecting the Atlantic and Pacific Oceans. As the Panama Canal approached its fiftieth anniversary, American officials grew concerned about the strategic limitations and maintenance costs of the existing lock-system canal. Their solution? Harness the "peaceful" power of nuclear excavation to carve a new waterway at sea level through Central America, eliminating the need for locks altogether ⁷ .

What began as an engineering challenge soon exploded into a scientific controversy that would help redefine humanity's relationship with the marine environment. At the heart of this conflict stood two competing visions: one seeing the oceans as impervious to human manipulation, the other recognizing their exquisite biological vulnerability. This confrontation between atomic-age ambition and ecological awareness would forge new understandings about marine conservation and mark a pivotal moment in how we perceive humanity's ability to alter marine ecosystems on a planetary scale ⁷ .

While engineers celebrated the potential of nuclear excavation, biologists grew increasingly concerned about a different type of explosion—a biological detonation that would occur if Atlantic and Pacific marine life mixed freely for the first time in millions of years. The Isthmus of Panama had formed approximately 3 million years ago, creating a land bridge between North and South America while separating marine ecosystems that had previously been connected. This geological event allowed Pacific and Atlantic marine species to evolve in isolation, resulting in dramatically different biological communities on either side of the isthmus ⁷ .

An obscure group of marine biologists from the Smithsonian Tropical Research Institute in Panama began raising questions that neither engineers nor government officials had considered: What would happen when species from two long-separated oceans mixed? Could introducing new predators or diseases devastate fisheries? Might the canal inadvertently create a pathway for species that would fundamentally alter both marine ecosystems? These researchers understood that the biological exchange potential represented an ecological and evolutionary experiment on a scale never before attempted by humans ⁷ .

These concerns gained traction through the efforts of biologists seeking funding for radiological-safety studies, who realized that the biological exchange issue represented an even greater potential threat than radiation. They argued that while radiological effects would be limited and relatively short-lived, biological exchange could permanently transform the oceans' ecological balance. For scientists like those at the Smithsonian, the proposed canal wasn't just an engineering project—it was a potential catastrophe that could unravel millions of years of evolutionary history in both oceans ⁷ .

In response to growing scientific concern, the National Academy of Sciences established a special committee in 1968 to evaluate the biological implications of a sea-level canal. Chaired by Ernst Mayr, one of the 20th century's most influential evolutionary biologists, the committee brought together experts in marine biology, ecology, and evolution. Their mandate was straightforward but monumental: determine the risks of marine species exchange and recommend a research program to address the most critical uncertainties ⁷ .

Mayr's committee faced an enormous challenge. The baseline data needed to predict the effects of mixing two oceans was largely nonexistent. Marine biologists had documented the different species on either side of the isthmus, but understood little about their ecological relationships, competitive abilities, or disease susceptibilities. The committee recognized that even identifying which species might become invasive predators or competitors would require extensive research ⁷ .

The committee's report, published in 1970, acknowledged the profound uncertainties surrounding the biological consequences of a sea-level canal. Mayr himself drew parallels between the proposed canal and some of history's most ecologically disruptive species introductions, noting that the effects could be far more extensive than any previous human-mediated biological exchange. The report concluded that the ecological risks were substantial enough to warrant a comprehensive 10-year research program before any construction should proceed ⁷ .

Faced with potentially catastrophic ecological consequences and limited existing data, the Mayr Committee outlined an ambitious research program that would need to answer fundamental questions about marine biology in record time. The proposed studies focused on understanding both the current state of Atlantic and Pacific ecosystems and predicting how they might change if connected ⁷ .

The research methodology emphasized comparative studies of similar environments on either side of the isthmus. Scientists would identify habitats in the Atlantic and Pacific that matched as closely as possible in depth, temperature, salinity, and other physical parameters, then conduct detailed inventories of species present in each. By understanding how similar environments supported different biological communities, researchers hoped to predict which species might successfully cross the canal and establish populations in the other ocean ⁷ .

Experimental approaches formed another critical component of the research plan. Researchers proposed transferring organisms between oceans under controlled conditions to study their survival, growth, and reproductive success. Competition experiments would determine whether Atlantic or Pacific species had advantages under specific conditions. Physiological studies would measure tolerances to different environmental factors, helping predict which species might survive the transition through the canal itself ⁷ .

The research design also acknowledged the need for long-term monitoring both before and after any potential canal construction. The committee recognized that some effects might take years or decades to manifest, requiring ongoing observation to detect subtle changes in ecosystem structure and function. This represented a significant shift in ecological thinking, moving beyond short-term studies to recognize the value of sustained observation of complex biological systems ⁷ .

Understanding the potential impacts of a sea-level canal required developing specialized research approaches and tools. Scientists needed to simultaneously document existing biodiversity, predict future changes, and develop methods for detecting early signs of ecological disruption. The research program outlined by the Mayr Committee and other scientists emphasized interdisciplinary approaches combining traditional field biology with emerging technologies ⁷ .

Despite the Mayr Committee's urgent recommendations, the proposed 10-year biological research program never received adequate funding from Congress. The political momentum behind the sea-level canal project, combined with skepticism about ecological concerns, relegated the biological studies to a secondary priority. The scientific advocacy for comprehensive research faced opposition from several quarters ⁷ .

Engineers and government officials primarily concerned with radiological safety questioned whether biological exchange warranted extensive study. Many in the engineering community still viewed the oceans as too vast to be significantly affected by human activities, reflecting a common perspective of the era that marine systems were essentially immune to permanent alteration. This fundamental difference in perspective created a communication gap between biologists warning of ecological catastrophe and engineers confident in their technological solutions ⁷ .

The debate played out not only in government hearings but also in the scientific and popular press. Articles in publications like the New Yorker brought the once-obscure issue of marine species exchange to broader public attention. The imagery of "a two-ocean bouillabaisse"—the phrase that would later inspire the title of historian Christine Keiner's study of the controversy—captured the public imagination more effectively than technical reports had captured political will ⁷ .

By the early 1970s, the sea-level canal project began to lose momentum for reasons beyond the biological concerns. Growing anti-nuclear sentiment, questions about the economic viability of the project, and shifting political priorities all contributed to its eventual abandonment. The United States instead pursued negotiations that would eventually lead to the transfer of the existing Panama Canal to Panama, ending American control without constructing a sea-level alternative ⁷ .

Though the sea-level canal was never built, the controversy surrounding it left a lasting impact on marine science and environmental policy. The debate forced scientists, engineers, and policymakers to confront for the first time the potential for human activities to cause planetary-scale biological disruptions. The specific concerns about interoceanic species exchange anticipated later issues with invasive species and human-mediated biological introductions ⁷ .

The controversy also highlighted the importance of baseline data for understanding and predicting environmental change. The Smithsonian Tropical Research Institute's work in documenting marine biodiversity on both sides of the Isthmus of Panama took on new significance as scientists recognized the value of this information for detecting future changes, whether from canal construction or other human impacts. This emphasis on baseline data would influence subsequent environmental assessment protocols ⁷ .

Perhaps most importantly, the sea-level canal debate marked a shift in how scientists and the public perceived ocean conservation. The idea that the oceans were vulnerable to permanent ecological disruption gained credibility through these discussions, paving the way for later conservation movements focused on marine protection. The controversy served as a dress rehearsal for future environmental debates about humanity's ability to alter planetary systems, from ozone depletion to climate change ⁷ .