OIKOS 70: 107-120. Copenhagen 1994 Succession, environmental fluctuations, and stability in experimentally manipulated microalgal communities Marco A. Rodriguez Rodriguez, M. A. 1994. Succession, environmental fluctuations, and stability inexperi- mentally manipulated microalgal communities. - Oikos 70: 107-120. Periphy algaewere experimentally manipulated over a 20-week period toevaluate theinfluence of environmental fluctuations andcommunity age on succession and community stability fluctuations were generated byperiodically trans- ferring artificial substrata between stations in an oligotrophic lake during 9 or 10 weeks. Developing communities exposed to induced fluctuations of two- andfour- weekperiods did nottrack thefluctuations. Instead, succession was slowed and followed a trajectory intermediate between those ofunmanipulated control communi- ties representing the two extremes ofthe fluctuation cy Thefluctuations favored the growth ofsome earlysuccessional taxa while strongly suppressing the growth ofat leastone late successional taxon. Responses of other late successional taxa were intermediate. After ending thefluctuations twoseparate experiments assessed ad- justment stability ("resilience") byfollowing convergence of the "fluctuating" commu- nities andof "earlysuccessional stage" communities to a control during a recovery period lasting 10or 11weeks. The detection of convergence depended onthe commu- nityproperty measured. Although thetotal densityof thefluctuating and control communities had converged 3 weeks into the recovery period, taxonomic composition did not converge during the recovery period, presumably because both sets of commu- nities werestillfarfrom maturity and therefore thecontrol was moving toward maturity almost as rapidlyas thefluctuating communities. The total density and taxonomic composition of the earlysuccessional stage communities had not converged tothose of the control bythe end of the recovery period. Slowcommunity recovery in this oligotrophic lake is inagreement with theoretical work showing increased recov- erytime in model ecosy with reduced nutrient input. M. A. Rodriguez,Inst. of Animal Resource y , Univ. of British Columbia, Vancouver, B. C., Canada V6T I W5 (present address: De'partement de biologieet des sciences de la sante, Univ.du Qu6bec a Rimouski, Rimouski (Quebec), Canada G5L 3A]). Natural populations and communities are often subject to considerabletemporal variation in environmental fea- tures (Wiens 1977,Connelland Sousa 1983). This obser- vation, coupledwith concern about the appropriateness of equilibrium-based analy has motivated much theoret- ical work dealingwith thedy of populations (Le- vins 1969, Lewontin and Cohen 1969, Roughgarden 1975a, Whittaker and Goodman 1979, Boy and Daley 1980,Leigh 1982),andcommunities orecosy (May 1973, 1974,Botkin and Sobel 1975,Roughgarden 1975b, Yodzis1978, Levins 1979, Chesson 1988) influctuating environments. Aspects analy in the community and ecosy studies include species coexistence, lim- its toniche overlap, "communication" ofstochastic fluc- tuation between species, and stability in the context of environmental stochasticity y a more management-oriented perspective, Holl- ing (1973) and Peterman (1980) have dealtwith the effects ofenvironmental fluctuations on community re- coveryIn these authors' scheme, the historical disturb- Accepted 10 November1993 Copy (? OIKOS 1994 ISSN 0030-1299 Printed in Denmark - all rights reserved OIKOS 70:1 (1994) 107