Paradox of the plankton

Diatoms through the microscope

Lytic cycle

Paradox of the Plankton refers to the ecological enigma that questions how a wide variety of plankton species can coexist in a relatively stable environment, such as a body of water, despite limited resources and competition. This paradox challenges the competitive exclusion principle, which suggests that when two species compete for the same limited resource, eventually the one with the slight advantage will dominate, leading to the extinction of the other.

Overview

The paradox was first introduced by G. Evelyn Hutchinson in 1961. Hutchinson observed that, in aquatic ecosystems, particularly in lakes and oceans, there is an astonishing diversity of plankton species coexisting despite the apparent homogeneity of their environment and the limited range of resources (mainly light and nutrients). According to the competitive exclusion principle, such a scenario should not allow for a high biodiversity, as competition over limited resources should lead to a few dominant species.

Explanations

Several hypotheses have been proposed to explain the paradox of the plankton. These include:

• Temporal and Spatial Heterogeneity: It suggests that environmental variability over time and space allows for multiple niches, enabling species to coexist by specializing in different conditions or areas.
• Intermediate Disturbance Hypothesis: This theory posits that periodic disturbances in the ecosystem, such as storms or nutrient influxes, prevent any one species from dominating, thus maintaining high diversity.
• Predator-Prey Interactions: Predation can prevent the dominance of a single species by culling the population of the most abundant prey, thereby allowing less competitive species to survive.
• Paradox of the Predator: Similar to predator-prey interactions, this concept focuses on how predators can maintain species diversity among their prey.

Implications

The paradox of the plankton has significant implications for ecology, biodiversity, and the understanding of ecosystem dynamics. It challenges simplistic models of competition and coexistence and highlights the complexity of natural systems. Furthermore, it underscores the importance of considering temporal and spatial scales, as well as the role of disturbances and predator-prey relationships, in the study of ecological communities.

See Also

• Competitive Exclusion Principle
• Ecological Niche
• Biodiversity
• Ecosystem Dynamics