Location: Great Lakes Environmental Research Laboratory
2205 Commonwealth Blvd.
Ann Arbor, MI 48105-2945
Date: Friday, February 23rd, 2001
Time: 10:30am
Room: 105 (Main Conference Room)
ABSTRACT: The Law of the Minimum states that the resource in shortest supply controls biological productivity. In general, nutrient supply restricts the accumulation of biomass (yield limitation) whereas energy supply controls the velocity of growth (rate limitation). In most marine systems energy supply is ample during summer, allowing the complete exhaustion of the least available nutrient, most frequently nitrogen, whereas during winter, deep mixing recharges the euphotic zone with nutrients which, however, cannot be fully utilized due to shortage of radiant energy.The Gulf of Aqaba at the Northern end of the Red Sea can serve as an example for a purely nutrient-controlled system. During most years, radiant energy supply is sufficient for the complete exhaustion of nitrate within the mixed layer, even in winter. Because winter mixing depths vary between years, phytoplankton development and productivity exhibit pronounced inter-annual variations.
For years it has been hypothesized that energy supply in the Southern Ocean is insufficient to allow the complete depletion of nutrients for the build-up of phytoplankton biomass throughout the year (HNLC-Region). However, since the Equatorial Pacific and the Central North Pacific are also HNLC-Regions, low energy supply cannot serve as the only explanation for this pattern. Iron fertilization experiments in the Equatorial Pacific and, more recently, in the Southern Ocean suggest that also in the Southern Ocean, iron limitation might act at least as an additional mechanism controlling the primary production process.
For further information, please contact:
Dr. John Robbins
NOAA Great Lakes Environmental Research Laboratory
2205 Commonwealth Blvd.
Ann Arbor, MI 48105-2945
734-741-2283
robbins@glerl.noaa.gov
http://www.glerl.noaa.gov/news/seminars/2001/tilzer.html