LIFE-CYCLE STRATEGIES OF COPEPODS IN COASTAL UPWELLING ZONES

Life cycles of copepods of coastal upwelling zones are of the multigen erational type-as many as 10 or more generations may be produced each year, depending upon water temperature, food concentration and length of the upwelling season. Abundant food resources and moderate temperat ure convey advantages to those copepods living in coastal upwelling zo nes, however, there is a clear disadvantage in that coastal upwelling zones are highly advective environments. Typically, water circulation patterns are such that surface waters are carried offshore, deeper wat ers carried onshore and most of the water column over the continental shelf is moving equatorward. The challenge to copepod species that inh abit upwelling systems is Life cycle closure-how do eggs, nauplii, juv eniles and adults avoid being swept out of these ecosystems in the fac e of persistent transport out of the system? In this review, I first l ist the species which dominate coastal upwelling ecosystems then discu ss three variations on the multigenerational life cycle scheme that ar e observed in upwelling systems. The latter part of the review is devo ted to discussion of how individuals are retained in the productive co ntinental shelf waters within coastal upwelling ecosystems. The sugges tion is made that the only copepod species that successfully achieve l ife cycle closure in such systems are those that are preadapted to upw elling circulation patterns. Our quantitative understanding of the rel ative importance of physical factors (such as advection) and biologica l factors (birth, growth, and mortality) on life cycle strategies and population dynamics is quite rudimentary. It would help our understand ing if there were more field studies and more computer modeling studie s that focused on seasonal cycles of abundance, development times and vertical distribution of life cycle stages, and measurements of water circulation patterns. (C) 1998 Elsevier Science B.V. All rights reserv ed.