Subsurface chlorophyll maximum (SCM) location and extension in the water column as governed by a density interface in the strongly stratified Kattegat estuary

The aims of the study were to analyse the relations between the physics of a water column and the location of the subsurface chlorophyll maximum (SCM) peaks in a strongly stratified estuary. Could extension and depth location of the SCM be explained by the physical conditions in terms of water column stratification and density interface? Questions were addressed by obtaining data on water column density (CTD), chlorophyll a (Chl a), nutrients, (Fv/Fm), σPSII and Kd(PAR) at 15 positions along a 575 km transect in the Kattegat estuary. Results showed that the estuary was strongly stratified with mixed surface and bottom layers intercepted by a layer where density increased with depth. The SCM occurred only in this density interface, and widths of SCM and density interface were highly correlated. The surface waters were nearly depleted of inorganic nitrogen, phosphate and silicate though with significant higher concentrations in the waters below the interface. The Chl a concentration was comparatively higher in the SCM peak as well as maximum quantum efficiency (Fv/Fm) and functional cross sectional area (σPSII). The SCM was maintained at very low light levels and by a diapycnal nitrogen flux, with a stratified water column and nutrient depleted surface waters as predecessors. It was concluded that the depth location and vertical extension of the SCM in the estuary were closely linked to the physical structure of the water column in terms of density interface and stratification.

[1]  F. G. Figueiras,et al.  Microplankton assemblages in three Bias Baixas (Vigo, Arosa and Muros, Spain) with a subsurface chlorophyll maximum: their relationships to hydrography , 1991 .

[2]  Zbigniew S. Kolber,et al.  Variations in Chlorophyll Fluorescence Yields in Phytoplankton in the World Oceans , 1995 .

[3]  Jonathan Sharples,et al.  Phytoplankton motility and the competition for nutrients in the thermocline , 2007 .

[4]  M. Pejrup,et al.  Sediment Fluxes, Re-suspension and Accumulation Rates at Two Wind-exposed Coastal Sites and in a Sheltered Bay , 1997 .

[5]  K. Richardson,et al.  Multiple subsurface phytoplankton blooms occurring simultaneously in the Skagerrak , 2003 .

[6]  Patrick M. Holligan,et al.  Phytoplankton distribution and survival in the thermocline , 2001 .

[7]  P. Falkowski,et al.  Nitrogen- and irradiance-dependent variations of the maximum quantum yield of carbon fixation in eutrophic, mesotrophic and oligotrophic marine systems , 1996 .

[8]  K. Furuya,et al.  Well-developed subsurface chlorophyll maximum near Komahashi No. 2 Seamount in the summer of 1991 , 1998 .

[9]  L. Lund-Hansen.  Development and dynamics of a coastal sub-surface phytoplankton bloom in the southwest Kattegat, Baltic Sea* , 2006 .

[10]  Elena Litchman,et al.  Phytoplankton growth and stoichiometry under multiple nutrient limitation , 2004 .

[11]  D. Moorhead,et al.  Environmental Factors Associated with Deep Chlorophyll Maxima in Dry Valley Lakes, South Victoria Land, Antarctica , 2006 .

[12]  L. Lund-Hansen,et al.  An inflow and intrusion event in the Little Belt at the North Sea-Baltic Sea transition and a related sub-surface bloom of Pseudo-nitzschia pseudodelicatissima , 2004 .

[13]  L. Harding,et al.  SeaWiFS retrievals of chlorophyll in Chesapeake Bay and the mid-Atlantic bight , 2005 .

[14]  J. Sharples,et al.  Swimming for survival: A role of phytoplankton motility in a stratified turbulent environment , 2008 .

[15]  R. Bidigare,et al.  Light driven seasonal patterns of chlorophyll and nitrate in the lower euphotic zone of the North Pacific Subtropical Gyre , 2004 .

[16]  K. Richardson,et al.  Dynamics of a subsurface phytoplankton maximum in the Skagerrak , 1993 .

[17]  F. Kestner,et al.  Estuaries : a physical introduction , 1974 .

[18]  D. Mills,et al.  Primary production in the deep chlorophyll maximum of the central North Sea , 2005 .

[19]  J. Aiken,et al.  A methodology to determine primary production and phytoplankton photosynthetic parameters from Fast Repetition Rate Fluorometry , 2004 .

[20]  L. Edler,et al.  Fifty years of primary production measurements in the Baltic entrance region, trends and variability in relation to land-based input of nutrients , 2006 .

[21]  Hugh L. MacIntyre,et al.  Evaluation of biophysical and optical determinations of light absorption by photosystem II in phytoplankton , 2004 .

[22]  B. Hodges,et al.  Simple models of steady deep maxima in chlorophyll and biomass , 2004 .

[23]  J. Seppälä,et al.  Spatial distribution of phytoplankton in the Gulf of Riga during spring and summer stages , 1999 .

[24]  G. Fahnenstiel,et al.  Subsurface chlorophyll maximum and associated Cyclotella pulse in Lake Superior , 1983 .

[25]  J. Aiken,et al.  The annual cycle of phytoplankton photosynthetic quantum efficiency, pigment composition and optical properties in the western English Channel , 2004, Journal of the Marine Biological Association of the United Kingdom.

[26]  B. Gustafsson.  Time-dependent modeling of the Baltic entrance area. 1. Quantification of circulation and residence times in the Kattegat and the Straits of the Baltic sill , 2000 .

[27]  Torkel Gissel Nielsen,et al.  Effects of a Chrysochromulina polylepis subsurface bloom on the planktonic community , 1990 .

[28]  M. Kahru,et al.  Coarse-Scale Spatial Structure of Phytoplankton Standing Crop in Relation to Hydrography in the Open Baltic Sea , 1981 .

[29]  L. Edler,et al.  Subsurface chlorophyll maxima in the Skagerrak-processes and plankton community structure , 1996 .

[30]  André W. Visser,et al.  Subsurface phytoplankton blooms fuel pelagic production in the North Sea , 2000 .

[31]  John P. Ryan,et al.  Interacting physical, chemical and biological forcing of phytoplankton thin-layer variability in Monterey Bay, California , 2010 .

[32]  John J. Cullen,et al.  The deep chlorophyll maximum comparing vertical profiles of chlorophyll a , 1982 .

[33]  G. Kullenberg.  ENTRAINMENT VELOCITY IN NATURAL STRATIFIED VERTICAL SHEAR FLOW. , 1977 .

[34]  L. Lund-Hansen,et al.  Modes of Stratification in a Semi-enclosed Bay at the North Sea–Baltic Sea Transition , 1996 .

[35]  C. Klausmeier,et al.  Phytoplankton nutrient competition under dynamic light regimes , 2004 .

[36]  T. Hori,et al.  Abundance of picophytoplankton in the subsurface chlorophyll maximum layer in subtropical and tropical waters , 1984 .

[37]  G. C. Anderson.  SUBSURFACE CHLOROPHYLL MAXIMUM IN THE NORTHEAST PACIFIC OCEAN1 , 1969 .

[38]  L. Lund-Hansen,et al.  Bio-optical properties and development of a sub-surface chlorophyll maxima (SCM) in southwest Kattegat, Baltic Sea , 2006 .

[39]  I. Hense,et al.  Revisiting subsurface chlorophyll and phytoplankton distributions , 2008 .

[40]  J. Heilmann,et al.  Annual distribution and activity of phytoplankton in the Skagerrak/ Kattegat frontal region , 1994 .

[41]  K. Richardson,et al.  Seasonal distribution and production of phytoplankton in the southern Kattegat , 1991 .

[42]  M. Gilmartin,et al.  Some Observations on the Chlorophyll Maximum and Primary Production in the Eastern North Pacific , 1973 .

[43]  K. Banse.  Clouds, deep chlorophyll maxima and the nutrient supply to the mixed layer of stratified water bodies , 1987 .

[44]  P. Boyd,et al.  A persistent subsurface chlorophyll maximum in the Interpolar Frontal Zone south of Australia: Seasonal progression and implications for phytoplankton-light-nutrient interactions , 2001 .

[45]  K. Kononen,et al.  Development of a subsurface chlorophyll maximum at the entrance to the Gulf of Finland, Baltic Sea , 1998 .

[46]  P. Falkowski,et al.  Measurements of variable chlorophyll fluorescence using fast repetition rate techniques: defining methodology and experimental protocols , 1998, Biochimica et biophysica acta.

[47]  R. Eppley,et al.  Chlorophyll maximum layers of the southern-california bight and possible mechanisms of their formation and maintenance , 1981 .

[48]  K. Kononen,et al.  Development of a deep chlorophyll maximum of Heterocapsa triquetra Ehrenb. at the entrance to the Gulf of Finland , 2003 .

[49]  P. Falkowski,et al.  Use of active fluorescence to estimate phytoplankton photosynthesis in situ , 1993 .

[50]  P. Ridd,et al.  Modelling of Suspended Sediment Transport in Coastal Areas Under Waves and Currents , 1997 .

[51]  B. Osborne,et al.  Light and Photosynthesis in Aquatic Ecosystems. , 1985 .

[52]  Ulf Larsson,et al.  Nutrient limitation of primary production in the Baltic Sea area , 1990 .