Monterey Bay Phytoplankton. II. Resting Spore Cycles in Coastal Diatom Populations

The purpose of this study is to examine the role of "restingspores" in natural population cycles of temperature, neriticdiatoms. Resting spores are a conspicuous element of centricdiatom populations in most neritic and some deep-water environmentsof the world oceans. Until recently the spores have been accepted,almost axiomatically, as surviving as a seasonal benthic stagewhich reinoculate the water column at the onset of favorablegrowth conditions. Data to support this hypothesis, however,is limited and contradictory. In my study, I am examining theoccurrence of resting spores in relation to vegetative cellcycles and oceanographic conditions in Monterey Bay, California,a nearshore upwelling-dominated system. I have utilized samplesfrom the water column, from settling-tubes, and from sedimentcores to document the cycles. Resting spore cycles were observed for many neritic species,and spore cycles for abundant species were considered in detail.Resting spore formation was associated with low nitrate concentrationsin surface waters. After spore formation in the water columnspores were found in settling-tubes and in sediment samples.Spore formation was a frequent event and spores were often presentin the water column and in the sediments. Observations of spore cycles in the present study were consistentwith the prevailing idea that resting spores function as benthicresting stages in coastal populations. The pelagic retentionand/or dispersal in coastal circulation cells, however, alsoappeared to be highly likely. The study has demonstrated thepotential for resting spores to function as survival stagesin Monterey Bay and in other regions with similar hydrographicconditions. The present evidence regarding the role of restingspores suggests that resting spores may have a wide range offunctions, and a more inclusive (or alternate) resting sporehypothesis is suggested.