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Seasonal Phytoplankton Demographic Processes and Experiments on Interspecific Competition
Author(s) -
Carney Heath J.,
Richerson Peter J.,
Goldman Charles R.,
Richards Robert C.
Publication year - 1988
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1941015
Subject(s) - epilimnion , interspecific competition , competition (biology) , phytoplankton , biology , ecology , water column , nutrient , eutrophication , hypolimnion
Population dynamics of Lake Tahoe phytoplankton species were studied during 1985. Four dominant diatoms were examined: Cyclotella glomerata, Cyclotella ocellata, Synedra amphicephala, and Synedra radians. The role of interspecific resource—based competition during spring and summer was tested in three ways: (1) species distribution patterns along the vertical gradient (upper 100 m of the water column), (2) measurements of in situ growth and loss (sinking, grazing, natural death, diffusion) processes, and (3) transplants of assemblages between depths. All three tests indicated that resource—based competition was important. Species clearly segregated with thermal stratification and nutrient depletion in the epilimnion. C. glomerata peaked within the epilimnion (0—20 m), S. radians became dominant in the deep chlorophyll maximum region (60—90 m), and the other species peaked at intermediate depths. Resource—limited growth was a dominant process during this time, and sinking and natural death were significant losses. Experimental transplants of assemblages between two depths (15 and 75 m) demonstrated competitive interactions in the phosphate—limited region near the surface, but there was no evidence of competition in the deeper light—limited region. This suggested asymmetrical competition along the vertical gradient. Primary productivity nutrient—enrichment bioassays and growth kinetic assays (phosphate, nitrate, light) also indicated that phosphate and light limitation were important bases of species interactions.