03 Oct Heavy metals and seasonality compromise the reproduction of black kelp in Quintero-Puchuncaví: new study warns of ecological and productive impacts

A study led by researchers from the Millennium Institute of Coastal Socio-Ecology (SECOS) revealed that pollution, together with seasonal effects, impacts the early reproductive stages of black kelp, a key resource for artisanal fishers. The findings warn of ecological and economic impacts in the Quintero-Puchuncaví area and call for integrating environmental variables into coastal management policies.

The bay of Quintero-Puchuncaví, located in the Valparaíso region, has for decades been a symbol of industrial pollution in Chile. The area hosts an industrial complex that included a copper smelter, coal-fired power plants, and hydrocarbon discharges.

The result has been a process of chronic environmental degradation, widely documented in the scientific literature. Studies have reported heavy metal levels well above international water quality standards, as well as evidence of contaminant transfer from algae to marine invertebrates. Now, a new scientific study provides novel evidence on how the combination of heavy metals and seasonal variability compromises the reproduction of black kelp (Lessonia spicata), one of Chile’s most important brown algae, both ecologically and economically.

A key species at risk

The research, recently published in the Journal of Applied Phycology, was led by Loretto Contreras, researcher at SECOS, CAPES, and faculty at Universidad Andrés Bello, along with a team of researchers from SECOS and various universities. The study was conducted at two sites in central Chile with contrasting conditions: Horcón, a bay in the Puchuncaví municipality exposed to high levels of pollution, and Quintay, considered a low-impact site with minimal contamination.

Spores were collected at both sites during spring 2023 and autumn 2024 to evaluate the species’ reproductive effort and monitor its development over 28 days under controlled culture conditions. During this period, key variables were recorded to compare the performance of populations across different environments and seasons.

The results show that while kelp reproduction tends to peak in autumn—a natural pattern of the species—this window of success is strongly disrupted by pollution, creating a “bottleneck effect” that decimates populations in their most vulnerable phases. In highly impacted areas such as Horcón, the most sensitive stages of the kelp’s life cycle are severely affected, reducing its ability to regenerate and persist over time, thereby undermining the species’ capacity to renew its populations.

“In polluted sites such as Horcón, we observed problems in the early reproductive stages: lower gametophyte survival, imbalances in sex ratios, and sporophyte necrosis. Although sometimes there seems to be high fertility, it is actually an artificial effect caused by the mortality of many individuals,” explains Contreras.

A life cycle under pressure

The study places special emphasis on the microscopic phases of the kelp life cycle—a critical moment often overlooked in research and conservation policy. “Kelp can reproduce more than once a year, but it seeks ideal conditions to maximize success in autumn. In Horcón, we found that those conditions were interrupted by stressors such as pollution, which caused bleaching in microscopic stages and subsequent necrosis in sporophytes,” says Geraldine Véliz, a SECOS-UNAB researcher who conducted her undergraduate thesis as part of this study.

According to Véliz, the vulnerability of early stages can trigger a domino effect across the entire life cycle: “If the early stages fail to develop, genetic diversity and the species’ resilience to other stressors—such as rising temperatures driven by climate change—are reduced.”

Beyond the ecological impact, the findings have profound implications for the local economy. In Chile, seaweed harvesting is a source of income for thousands of families engaged in artisanal fishing. “If populations cannot regenerate properly, seaweed availability decreases over time. This directly impacts fishers and harvesters who depend on kelp extraction for their livelihoods,” warns Contreras.

In the medium term, the study suggests a decline in the amount of seaweed available for harvest. In the long term, if degradation persists, there is a risk that natural kelp beds could disappear in areas like Quintero-Puchuncaví, threatening local economic activity.

Researchers stress that these findings, which deepen the understanding of pollution’s role on key coastal species, must serve as a basis for adjusting marine resource management and conservation policies in Chile. “Policies must recognize that pollution not only damages ecosystem health but also jeopardizes local livelihoods. We need differentiated management plans, extraction limits tailored to each area, and initiatives for the restoration of kelp forests,” concludes Contreras.