Temporal variations among planktonic diatom assemblages in a turbulent environment of the southern Strait of Georgia, British Columbia, Canada

Abstract

We examined the species composition and concentrat~on of planktonic algae as well as irradiance and near-surface temperature and sal~nity 3 times per week for 1 yr in a turbulent marine environment with con.tinuously high nutrient concentrations Seasonal variations in tempera.ture and sahn~ty were small, and diatoms composed the largest percentage of phytoplankton (25 pm) cell numbers throughout the year. We observed at least 96 diatom species, of which some were present throughout most of the year while others were observed for periods as short as 1 to 2 wk. Diatom species diversity reached minimum and maximum values during wlnter and summer months, respectively, and was positively correlated to temperature and daylength and negatively correlated to salinity. Winter and spring blooms occurred and were numerically dominated by small and large cells of Skeletonema costatum, respectively, and Pseudo-nitzschia delicatissirna, resulting in minimum seasonal values of species evenness, which peaked during summer months. The first 4 axes of a canonical correspondence analysis (CCA) explained 76 % of the variance in the diatom data; the measured environmental variables explained 90% of this variation, of which temperature had a dominant role. We discuss possible environmental optima of 44 diatom species based on results of CCA and make suggestions regarding altered measures of diversity.

Influence of nutrients, temperature, light and salinity on the occurrence of Paralia sulcata at Helgoland Roads, North Sea

“…A negative correlation of the abundance of Paralia sulcata and temperature was described by Hobson & McQuoid (1997). Although temperatures in the southern part of Vancouver Island were slightly higher in winter (mean of 8.1°C) and cooler in summer (mean of 13.7°C) (Hobson & McQuoid 1997), the abundance pattern of P. sulcata shows similar seasonal patterns to those found at Helgoland Roads.…”

“…In waters off the southern part of Vancouver Island (British Columbia, Canada), Paralia sulcata was found year-round in cell concentrations of 1500 cells l -1 reaching maximum numbers in winter blooms of 3000 to 6000 cells l -1 (Hobson & McQuoid 1997). As a coldwater alga, P. sulcata shows a growth optimum at a temperature of 7 ± 1°C (Hobson & McQuoid 1997, Zong 1997.…”

“…As a coldwater alga, P. sulcata shows a growth optimum at a temperature of 7 ± 1°C (Hobson & McQuoid 1997, Zong 1997. P. sulcata displays a competitive advantage under low light conditions (Hobson & McQuoid 1997) and prefers low temperatures and short day lengths with high irradiance (Roelofs 1984, Zong 1997, McQuoid & Nordberg 2003b.…”

“…Often found in the benthos, the presence of Paralia sulcata in the phytoplankton could be dependent on vertical transport processes and resuspension into the plankton by strong winds and tidal mixing (Roelofs 1984, Hobson & McQuoid 1997. Increased vertical mixing in the water column brings nutrient-rich, saline water to the surface, thus creating conditions which favour the occurrence of P. sulcata (McQuoid & Nordberg 2003b).…”

Reconstruction of Oceanographic Changes Based on the Diatom Records of the Central Okhotsk Sea over the last 500000 Years

“…The most common interpretation of P. sulcata is as an indicator of coastal upwelling situations which result in high primary production (Abrantes 1988a(Abrantes , b, 1991. Paralia sulcata does not typically form large blooms in plankton, but high proportions can be found in the water column during winter (Sancetta 1989;Hobson and McQuoid 1997). Since P. sulcata grows primarily in benthic habitats, physical forces such as strong winds (Haggart 1988;Cullingford et al 1989) and tidal mixing (Oh and Koh 1995) may be primary mechanisms for the transport of cells into the plankton.…”