Science, politics and economics of the Peruvian anchoveta fishery

Studies of oceanic paleoproductivity have lagged in part because of the absence of a suitable proxy for measuring paleoproductivity. A transfer function has recently been proposed which directly translates carbonate mass accumulation rates into a quantitative measure of productivity. This transfer function ha been applied at six ODP sites in the Indian Ocean in order to investigate temporal and spatial changes in Indian Ocean productivity during the Tertiary Period. Early Paleogene productivity in the Indian Ocean was considerably higher than in the late Paleogene and Neogene. A warmer, more confined sea, with large riverine nutrient input from close lying land masses may account for the generally higher early Paleogene productivity. Productivity increased dramatically at two times during the Paleogene: during early Paleocene calcareous nannofossil Zone NP5 and during early Eocene Zone NP11. These productivity increases may be related to abrupt climatic changes which reorganized oceanic circulation and stimulated major changes in productivity. Productivity began to fall in the Oligocene as a result of global cooling and the initiation of the modern Indian Ocean circulation system. This trend continued into the Neogene, which was characterized by generally low productivity, interspersed with occasionally higher levels, especially at the more northern sites in the Indian Ocean.

Paleoproductivity of the Indian Ocean during the Tertiary Period

The American physical oceanographer Henry Stommel and co-workers proposed “the perpetual salt fountain” and suggested the possibility of upwelling deep seawater without an energy source. In the open ocean, deep seawater containing rich nutrients becomes a source of primary production. Previously, we have tested Stommel's hypothesis by numerical simulations and in ocean experiments, and confirmed the upwelling of a perpetual salt fountain. In the present study, we conducted an open-ocean experiment in the Philippines Sea, and succeeded to demonstrate an increase in chlorophyll concentration. The chlorophyll concentration at the pipe outlet was much greater than that in the surrounding seawater. Satellite ocean-color image around the pipe was analyzed, and the signal of artificial upwelling is investigated. Composite analysis of satellite chlorophyll image indicates an increased surface chlorophyll distribution in the vicinity of pipe position, in which the increasing signal is much larger than the expected production based on nutrient supply. Although the problem must be further discussed, this increased signal is shown to be statistically significant. This mechanism may contribute to effective utilization of fishery resources in subtropical oligotrophic region.

Evidences of increasing primary production in the ocean by Stommel's perpetual salt fountain

Effects of paleosedimentary environment on organic matter enrichment in a saline lacustrine rift basin - A case study of Paleogene source rock in the Dongpu Depression, Bohai Bay Basin

Upwelling: Effects on Air Temperatures and Solar Irradiance

Desertification can be a particularly visible consequence of climatic change. While considerable research has been devoted to terrestrial desertification in recent years, it is in the sea that biological deserts comprise 90% of the total area. Productive ocean ‘oases’ or coastal upwelling areas comprise less than .1% of the total ocean area but yield up to half the world's fish catch. Since these high productivity zones occur near coastal margins they are closest to man's pollution and his tools for species decimation. In this paper we examine the notion of biological deserts in the sea and assess the limitation of the ocean as a biological resource. Since climatic conditions favorable for above average ocean productivity are often conducive to the creation of coastal deserts, the connections between ocean and atmosphere in these regions are examined. Finally, the impacts of natural climatic and biological variability, marine pollution, and over-fishing on the process of biological desertification in the sea are explored.

J. Dana Thompson

Papers

Ocean Deserts and Ocean Oases