Fig. 2
From: Conceptualizing phytoplankton communities in the absence of resource based competitive exclusion
Lake analogy for nutrient competition concepts in steady-state plankton systems. (a) The ‘Glory Hole’ spillway of (b) Lake Berryessa, California. The small spillway can maintain lake levels across its ~ 80 km2 surface area because the strong force of gravity rapidly eliminates elevation differences across the lake and the spillway has a high flow capacity. Similarly, phytoplankton cells have the ability to rapidly take up nutrients at their cell surface, creating a strong concentration gradient in their boundary layers. Because diffusion acts to rapidly eliminate concentration differences, the discrete uptake by cells has the potential to rapidly deplete far-field concentrations in the absence of a resupply source. (c) A lake analogy of the R* rule, where the two spillways (A, B) represent populations of phytoplankton with different uptake capacities. In this panel, the lake level is initially above both spillways (dashed surface), water drained by the spillways is removed from the system, and there is no new source of water to the lake. Under these conditions, the B spillway is ‘outcompeted’ by the A spillway because of the latter’s greater drainage ability. In laboratory competition experiments, a superior resource competitor can exclude an inferior competitor, irrespective of distancing between cells, because the former can continue increasing its biomass until the concentration of limiting resource is sufficiently low that division rate of the inferior competitor is less than the experimentally imposed predation rate. (d) Lake analogy of steady-state plankton systems where water passing through the spillways (blue arrows) is redeposited on the lake’s surface. In this case, the drawdown potential of the different spillways does not alter the steady-state lake level and, consequently, spatial distancing of spillways A and B impedes the former from preventing flow through the latter. In phytoplankton communities, nutrient recycling and spatial distancing similarly allow coexistence of species with vastly different resource uptake potentials. These analogies are intended to provide intuition regarding plankton systems, rather than a robust depiction of the three-dimensional space defining growth conditions of phytoplankton cells. Image credit: (a) “Monticello Dam spillway, Lake Berryessa” by Jeremy Brooks; (b) “Aerial view of Lake Berryessa” by Dick Lyon. Both images can be found on commons.wikimedia.org, and are licensed under CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/).
