Hierarchical control of phytoplankton succession by physical factors

The influence of physical factors on phytoplankton succession was assessed during an annual cycle in the St. Lawrence Estuary (Canada), where nutrients remain abundant throughout the whole year. Typically, the phytoplankton production period is short (Jun to Sep) and characterized by the occurrence of 3 distinct peaks. The July bloom was dominated by the 2 diatoms Thalassiosira nordenskioldii and Chaetoceros debilis, while Leptocylindrus minimus and Nitzschia seriata were dominant a t the beginning and at the end of September, respectively. The occurrence of the 3 bloom periods is related to an increase in mean light intensity in the mixed layer, caused by strong density stratification which decreases the depth of the mixed layer. During these bloom periods, the succession of diatom species is mainly controlled by variations in temperature. Flagellates were observed all yearround, although they were more abundant during the diatom bloom periods. Their abundance is related to variations in surface temperature. In the Estuary, where nutrients are usually non-limiting, the observed succession of taxa is restricted to the first stage of the Margalef (1958) succession model (small cells with high growth rates, which are typical species for frequently destabilized environment). Our results demonstrate that the frequency of destabilization of the water column selects the growth rates of the cells, through nutrient conditions. Mean light intensity in the mixed layer determines the occurrence of non-motile forms such as diatoms, and temperature sets the conditions for optimal metabolic activity (flagellate numbers and succession of diatom species). This results in a conceptual model where stability conditions, mean light in the mixed layer and temperature hierarchically control phytoplankton succession.

[1]  R. Margalef,et al.  On Certain Unifying Principles in Ecology , 1963, The American Naturalist.

[2]  R. Margalef.  Life-forms of phytoplankton as survival alternatives in an unstable environment , 1978 .

[3]  R. Margalef,et al.  Sorne concepts relative to the organization of plankton , 1967 .

[4]  R. Perry,et al.  Tidal Mixing and Summer Plankton Distributions in Hecate Strait, British Columbia , 1983 .

[5]  L. Ignatiades.  The influence of water stability on the vertical structure of a phytoplankton community , 1979 .

[6]  H. Sverdrup,et al.  On Conditions for the Vernal Blooming of Phytoplankton , 1953 .

[7]  F. Briand.  Seasonal Variations and Associations of Southern Californian Nearshore Phytoplankton , 1976 .

[8]  P. Koeller,et al.  Winter condition of marine plankton populations in Saanich inlet, B.C., canada. I. Phytoplankton and its surrounding environment , 1978 .

[9]  Graham P. Harris,et al.  Temporal and Spatial Scales in Phytoplankton Ecology. Mechanisms, Methods, Models, and Management , 1980 .

[10]  M. Sinclair.  Summer Phytoplankton Variability in the Lower St. Lawrence Estuary , 1978 .

[11]  G. Hitchcock,et al.  The importance of light in the initiation of the 1972‐1973 winter‐spring diatom bloom in Narragansett Bay1 , 1977 .

[12]  Marta Estrada,et al.  Functional morphology of organisms involved in red tides, as adapted to decaying turbulence , 1979 .

[13]  R. Holmes,et al.  THE SECCHI DISK IN TURBID COASTAL WATERS1 , 1970 .

[14]  W. Richard,et al.  TEMPERATURE AND PHYTOPLANKTON GROWTH IN THE SEA , 1972 .

[15]  L. Legendre.  Hydrodynamic Control of Marine Phytoplankton Production: The Paradox of Stability+ , 1981 .

[16]  G. Bugden.  Salt and Heat Budgets for the Gulf of St. Lawrence , 1981 .

[17]  R. Iverson,et al.  Chlorophyll and nitrate fine structure in the southeastern Bering Sea shelf break front , 1979, Nature.

[18]  T. Malone,et al.  Parameters of light-dependent photosynthesis for phytoplankton size fractions in temperate estuarine and coastal environments , 1981 .

[19]  C. Lorenzen.  Extinction of Light in the Ocean by Phytoplankton , 1972 .

[20]  W.W.C. Gieskes,et al.  The phytoplankton spring bloom in Dutch coaqtal waters of the North Sea , 1975 .

[21]  R. Margalef,et al.  Temporal succession and spatial heterogeneity in natural phytoplankton , 1958 .

[22]  Gordon A. Riley,et al.  Phytoplankton of the North Central Sargasso Sea, 1950–521 , 1957 .

[23]  E. Durbin,et al.  Seasonal studies on the relative importance of different size fractions of phytoplankton in Narragansett Bay (USA) , 1975 .

[24]  K. Banse,et al.  The dynamics of phytoplankton blooms in puget sound a fjord in the Northwestern United States , 1975 .

[25]  C. Lorenzen,et al.  Fluorometric Determination of Chlorophyll , 1965 .

[26]  T. Parsons,et al.  A practical handbook of seawater analysis , 1968 .

[27]  T. Malone.  Environmental regulation of phytoplankton productivity in the lower Hudson Estuary , 1977 .

[28]  L. Watling,et al.  Seasonal variations in Delaware Bay phytoplankton community structure , 1979 .

[29]  E. Durbin.  STUDIES ON THE AUTECOLOGY OF THE MARINE DIATOM THALASSIOSIRA NORDENSKIÖLDII
CLEVE. 1. THE INFLUENCE OF DAYLENGTH, LIGHT INTENSITY, AND TEMPERATURE ON GROWTH 1 , 1974 .

[30]  P. Holligan,et al.  The vertical distribution and succession of phytoplankton in the western English Channel in 1975 and 1976 , 1977, Journal of the Marine Biological Association of the United Kingdom.

[31]  G. E. Hutchinson,et al.  A treatise on limnology. , 1957 .

[32]  T. Platt,et al.  Variations in assimilation number of coastal marine phyto-phytoplankton: Effects of environmental co-variates , 1980 .

[33]  J. Sévigny,et al.  Summer Plankton Distributions Associated with the Physical and Nutrient Properties of the Northwestern Gulf of St. Lawrence , 1979 .

[34]  B. C. Patten,et al.  An annual phytoplankton cycle in the lower Chesapeake Bay , 1963 .

[35]  J. Ryther,et al.  Experimental Evidence of Zooplankton Control of the Species Composition and Size Distribution of Marine Phytoplankton , 1980 .

[36]  J. Lund,et al.  The inverted microscope method of estimating algal numbers and the statistical basis of estimations by counting , 1958, Hydrobiologia.

[37]  E. Durbin.  Aspects of the biology of resting spores of Thalassiosira nordenskioeldii and Detonula confervacea , 1978 .

[38]  John H. Martin.  PHYTOPLANKTON‐ZOOPLANKTON RELATIONSHIPS IN NARRAGANSETT BAY. IV. THE SEASONAL IMPORTANCE OF GRAZING1 , 1970 .

[39]  T. Malone,et al.  The production and fate of phytoplankton size fractions in the plume of the Hudson River, New York Bight1 , 1979 .

[40]  R. Cǒté,et al.  Influence de débits élevés et variables d'eau douce sur le régime saisonnier de production primaire d'un fjord subarctique , 1979 .

[41]  C. Yentsch,et al.  A method for the determination of phytoplankton chlorophyll and phaeophytin by fluorescence , 1963 .

[42]  J. Barlow.  Spring Changes in Phytoplankton Abundance in a Deep Estuary, Hood Canal, Washington , 1961 .

[43]  R. Margalef.  Succession in marine populations , 1962 .

[44]  J. Wilson,et al.  Influence of the Shelf-Break Front Off Nova Scotia on Phytoplankton Standing Stock in Winter , 1979 .

[45]  T. Malone.  Light-saturated photosynthesis by phytoplankton size fractions in the New York bight, USA , 1977 .

[46]  P. Holligan,et al.  The effects of vertical stability on phytoplankton distributions in the summer on the northwest European Shelf , 1978 .