The study “From Greenland to green lakes: Cultural eutrophication and the loss of benthic pathways in lakes” offers a sweeping exploration of how human-driven nutrient enrichment reconfigures the basic energy pathways of lakes. The authors compare shallow, pristine Greenland lakes, forested lakes in the United States, and eutrophic Danish lakes to trace a planetary-scale pattern: as phosphorus increases, the architecture of lake productivity fundamentally shifts.
In oligotrophic Greenland lakes, sunlight reaches the entire lake bottom. Under such conditions, benthic algae thrive, generating as much as 80 to 98 percent of total primary production. Field measurements were supported by precise dissolved inorganic carbon analyses conducted with UIC Inc. carbon analyzers, ensuring accurate estimates of benthic and pelagic productivity. These tools anchored a clear picture of how energy flows when nutrients are scarce.
Across more nutrient-rich lakes, however, the story changes dramatically. Phytoplankton bloom, darkening the water and preventing light from reaching the sediments. As these suspended algae proliferate, they suppress their benthic counterparts, breaking the energetic link between lake bottoms and the organisms that rely on them. Even though phytoplankton production rises with increasing phosphorus, total lake-wide primary production increases only modestly because benthic losses counterbalance pelagic gains.
Stable isotope analyses add another dimension. By comparing the carbon signatures of grazers, predators, and filter feeders, the researchers reveal a striking shift in diet. In clear lakes, invertebrates feed heavily on benthic algae. As eutrophication intensifies, their isotopic signatures converge toward values characteristic of phytoplankton detritus. This indicates not only a loss of benthic production, but also a rewiring of entire food webs. Page 7 visuals illustrate this shift clearly, showing the declining difference in carbon signatures between feeding groups.
The implications stretch far beyond these three regions. The study suggests that eutrophication erodes one of the fundamental pathways through which energy enters lake ecosystems. It hints at long-term consequences for biodiversity, fish populations, and the resilience of shallow lakes to environmental change. As climate and land-use pressures intensify, understanding these benthic–pelagic transitions becomes essential for freshwater management.
Reference: Vadeboncoeur, Y., Jeppesen, E., Vander Zanden, M. J., Schierup, H.-H., Christoffersen, K., & Lodge, D. M. (2003). From Greenland to green lakes: Cultural eutrophication and the loss of benthic pathways in lakes. Limnology and Oceanography, 48(4), 1408–1418. https://doi.org/10.4319/lo.2003.48.4.1408
