Patchiness of phytoplankton and primary production in Liaodong Bay, China

<div><p>A comprehensive study of water quality, phytoplankton biomass, and photosynthetic rates in Liaodong Bay, China, during June and July of 2013 revealed two large patches of high biomass and production with dimensions on the order of 10 km. Nutrient concentrations were above growth-rate-saturating concentrations throughout the bay, with the possible exception of phosphate at some stations. The presence of the patches therefore appeared to reflect the distribution of water temperature and variation of light penetration restricted by water turbidity. There was no patch of high phytoplankton biomass or production in a third, linear patch of water with characteristics suitable for rapid phytoplankton growth; the absence of a bloom in that patch likely reflected the fact that the width of the patch was less than the critical size required to overcome losses of phytoplankton to turbulent diffusion. The bottom waters of virtually all of the eastern half of the bay were below the depth of the mixed layer, and the lowest bottom water oxygen concentrations, 3–5 mg L^–1, were found in that part of the bay. The water column in much of the remainder of the bay was within the mixed layer, and oxygen concentrations in both surface and bottom waters exceeded 5 mg L^–1.</p></div

Study area, sampling stations (● and △) and ¹⁴C incubation stations (△) in Liaodong Bay, China.

<p>Study area, sampling stations (● and △) and ¹⁴C incubation stations (△) in Liaodong Bay, China.</p

Contour maps of photosynthetic rates (Panel A, in mg C m^–3 h^–1), concentrations of Chl <i>a</i> (Panel B, in mg m^–3) and assimilation numbers (Panel C, in mg C mg^–1 Chl <i>a</i> h^–1), dissolved inorganic nitrogen (DIN, Panel D, in μM), silicate (SiO₃-Si, Panel E, in μM), and phosphate (PO₄-P, Panel F, in μM).

<p>Triangles in F denote stations with phosphate concentrations less than 25 nM.</p

Contour maps and/or corresponding location maps of temperature (Panels A and B, in °C), Secchi-disk depth (Panels C and D, in meters), Secchi-disk depth associated with temperature (Panel E), and dissolved oxygen (DO, Panel F, in mg L^–1).

<p>Contour maps and/or corresponding location maps of temperature (Panels A and B, in °C), Secchi-disk depth (Panels C and D, in meters), Secchi-disk depth associated with temperature (Panel E), and dissolved oxygen (DO, Panel F, in mg L^–1).</p

Relationship between DO concentrations and salinity (Panel A) and location of stations in three groups with different DO concentrations (Panel B).

<p>In Panels A and B, circle dots denote stations with high DO of more than 13 mg L^–1 at a salinity of 1 to low DO concentrations of 3–5 mg L^–1 at salinities of 16–26; Triangles and plus signs denote stations with DO concentrations of roughly 7–9 mg L^–1 and 9–11 mg L^–1, respectively, in both cases at salinities of 20–28.</p