Mohan P. Niraula

The paradox of enrichment in phytoplankton by induced competitive interactions

The biodiversity loss of phytoplankton with eutrophication has been reported in many aquatic ecosystems, e.g., water pollution and red tides. This phenomenon seems similar, but different from the paradox of enrichment via trophic interactions, e.g., predator-prey systems. We here propose the paradox of enrichment by induced competitive interactions using multiple contact process (a lattice Lotka-Volterra competition model). Simulation results demonstrate how eutrophication invokes more competitions in a competitive ecosystem resulting in the loss of phytoplankton diversity in ecological time. The paradox is enhanced under local interactions, indicating that the limited dispersal of phytoplankton reduces interspecific competition greatly. Thus, the paradox of enrichment appears when eutrophication destroys an ecosystem either by elevated interspecific competition within a trophic level and/or destabilization by trophic interactions. Unless eutrophication due to human activities is ceased, the worlds aquatic ecosystems will be at risk.

Evaluating the effectiveness of artificial marine structures as upwelling-generators to enhance oceanic CO2 sinks

Publisher Summary This chapter evaluates the effectiveness of an artificial marine structure as an upwell-generator to enhance oceanic CO 2 sequestration in the coastal areas of Japan. Results suggest that the processes responsible for vertical mixing between shallow waters and bottom waters were vertical shear of currents, internal wave breaking, and entrainment. It also found evidence that neap tides may enhance the mixing. The upwelling generated by the artificial marine structure, increased nutrient supply to the shallow layer. Coccoid pico-cyanobacteria represented about 25% to 30% of the total biomass produced during incubation. Diatoms of small size were abundant, among which Chaetoceros compressum and other Chaetoceros species predominated. Net organic production estimated over the year is 470 gC m -2 yr -1 using 1300 mgC m -2 day -1 . This value is the same order of magnitude as net organic production in temperate forests and mangroves. This, together with the contribution from forestation, could help enable Japan to reach its CO 2 -reduction target as set in the Kyoto Protocol. It is concluded that the use of marine biota, natural energy and this artificial upwelling system contributes effectively to increased CO 2 fixation.