Temperature‐influenced species competition in mass cultures of marine phytoplankton

Abstract

SummaryFive marine phytoplankton species (Phaeodaetylum tricornutum, Thalassiosira pseudonana, Skeletonema costatum, Monochrysis lutheri, and Dunaliella tertiolecta) were grown in enriched laboratory continuous cultures and natural populations were mass cultured outdoors for 16 months. Competition among the species was shown to be highly dependent on temperature, although the actual production of plant organic matter at the low growth rates used was relatively independent of this variable. Control of marine species in mass cultures does not appear economically feasible, but this drawback may be overcome by selecting herbivorous shellfish that are capable of assimilating those temperature-dependent phytoplankton species dominating in a particular locale.

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“…Thus we hyp~thesized that in intensive cultures that are poorly buffered ~ tricornutum enjoys a competitive advantage that is related primarily to pH. This hypothesis is consistent with the repeated observation that in large-scale outdoor cultures in which pH is unregulated and allowed to rise above 10 ~ tricornutum often dominates (Goldman and Ryther, 1976;D'Elia et al, 1977;Goldman and Mann, 1980).…”

“…20°C (Goldman and Ryther, 1976); but when silicon is limiting the temper ature range favoring dominance by ~ tricornutum is .extended down to <SoC as other cold water and silicon-requiring diatoms are eliminated from -100 competition (Goldman and Mann, 1980). These observations, together with the pH data from Section 0 lead us to suggest that ~ tricornutum always· will be favored when the pH is >10 and the temperature is ;n the range 100_20 0 e.…”

“…Other hypotheses to explain the success of ~ tricornutum in large~ scale' cultures have been offered including allelopathy (Sharp.et al, 1979), light limitation , temperature (Goldman and Ryther, 1976'), and silicon limitation (D'Elia et al, 1979;Goldman and Mann, 1980). Both temperature and silicon limitation play impdrtant rol~s in establishing some of the conditions favoring ~ tricornutum.…”

“…For example) a com mon problem has been the infestation and rapid takeover of nonaxenic mass cultures of desired species by weed microalgae such as the chlorophyte Scenedesmus sp. in freshwater systems and the marine diatom Phaeodactylum tricornutum in marine counterparts (Oswald and Golueke) 1968;Goldman and Ryther, 1976). Goldman (1976) speculated that among a group of marine species possessing equal growth characteristics in intensive culture) P.…”

“…tricornutum often is the successful competitor because of its ability to tolerate high pH or excrete toxic compounds (allelopathy), or both; how ever, as shown by Goldman and Ryther (1976)) this competitive edge occurs only within a restricted temperature range of'-10o-20°C.…”