Mosaicism of microplankton communities in the northern Strait of Georgia, British Columbia

The Sechelt Inlet complex (British Columbia, Canada), Including Narrows and Salmon Inlets, was sampled from h4ay 1988 to September 1990 in order to d e s c r~b e the nutrient and plankton regimes. Species succession w i t h~n the inlet was typical for temperate unpolluted waters despite aquaculture activity and nutrient-loading from the town of Sechelt at the southern end. The N : P ratio in the upper 21 m of 8.3, which is well below the Redfield ratio of 16, suggests an N-limited system. The ratio is also lower than those found in adjacent systems, and supports the a s s u~n p t~o n that Sechelt Inlet is the least influenced by oceanic waters. The N : P ratio also c o~n c~d e s with the optimum ratio for Skeletonerna costaturn of 8.1 which suggests that either the system provided an optimal nutrient regime for this diatom or the dominance of S. costatum determined ambient N:P ratios. The spring bloom, dominated by S. costatum and ThalaSS~~Sira nordenskioeldii, occurred early (in March) due to the combined influence of stratification, created by runoff from Salmon Inlet, and shelter from wind exposure. By summer the waters became depleted of nitrate down to 5 m, and nanoplankton, composed chiefly of cryptomonads and Chrysochrornulina spp., prevailed. Bimodal peaks in nanoflagellate biomass occurred each summer, with the cryptomonads remaining regular components. Under normal meteorological conditions Chrysochromulina spp. \vould codominate but during 1989, storm activity in May somehow caused the replacement of the prymnesiomonads by the silicoflagellate Dictyocha speculurn. The latter occurred In ~t s askeletal form during the late summer nanoflagellate peak. The water injected through the mouth of Sechelt Inlet by a tidal jet combined with water overlying the anoxic bottom of inner Narrows Inlet and caused stimulation of plankton growth at the confluence of these 2 inlets. There was also h~g h biomass at the shallow southern end possibly due to increased mixing over a sill and m~l d eutrophication.

Section: Spring Bloommentioning

confidence: 97%

“…Consequently, a plankton study was needed for industry to choose optimal sites: those which balance high productivity and potentially harmful effects due to noxious plankton. This was not done prior to the establishment of farms and there was a loss to the local industry of Can$2.5 million (Taylor et al 1991).…”

Section: Introductionmentioning

confidence: 99%

Phytoplankton ecology of Sechelt Inlet, a fjord system on the British Columbia coast. I. General features of the nano- and microplankton

Haigh¹,

Taylor²,

Sutherland³

1992

“…Studies indicate that: (1) oligotrichs similar to those presented in Table 4 are almost always present at average concentrations of 1 to 10 cells ml-' (Fenchel 1987, Lynn & Montagnes 1991, therefore ciliates must be surviving in situ; (2) estimates of prey biomass (2 to 20 pm in diameter) In coastal waters, where ciliates have been examined, often range between 5 and 50 ng C ml-' (e.g. Smetacek 1981, for Kiel Bight, Andersen & Smensen 1986, for Danish waters; , for the NW Mediterranean Sea; Haigh & Taylor 1991, Halgh et al 1992, for NE Pacific waters); (3) oligotrich maxlmum growth rates occur at concentrations > l 0 0 ng C m l l (Table 4), which are above typical prey biomass levels: (4) ciliate threshold concentrations range around 10 to 100 ng C ml-' (Table 4 ) , which are also near or above typical prey biomass levels; and (5) cillates die over a period of hours to days when food levels are depleted below threshold concentrations. These data suggest that since cillates are present In the plankton, they must encounter prey concentrations of > l 0 ng C ml-' to survive.…”

Section: An Ecological Implication Of the Numerical Responsesmentioning

confidence: 99%

Growth responses of planktonic ciliates in the genera Strobilidium and Strombidium

Montagnes¹

1996

145

147

Intrinsic growth and mortality rates need to be estimated to assess the potential for oligotrich ciliate populations to exploit prey populations, and since species specific differences exist, data for a variety of ciliates grazing on a variety of prey are also needed. In this paper, data are presented on the growth and mortality rates of 4 planktonic oligotrichs (2 Strobilidium species and 2 Strombidium species), at a number of prey concentrations. Growth and mortality data for these and other species in these 2 genera are reviewed. In general, these oligotrichs have maximum growth rates (p, d-l) ranging from -0.3 to 2.2 (at temperatures ranging from 6 to 31°C); they have similar threshold concentrations (the food concentration where growth rate equals zero) of 10 to 100 ng C ml-'; they have rapid mortality rates at sub-threshold concentrations (cells only survive 1 to 3 d), and the range of food concentrations where the growth rate increases from zero to near its maximum is 20 to 300 ng C ml-l Although generalities can be made about ciliates in these 2 genera, the data suggest that in terms of growth and mortality rates, planktonic oligotrichs cannot be considered a single functional group. There is, however, a need to predict 'typical' oligotrich growth rates. To this end, several formulae have been established to predict maximum growth rates from ciliate cell volume and ambient temperature. In this paper, the growth data for Strobilidii~m and Strombidium are reviewed and compared to the predicted values from formulae In the literature; the formula presented by Muller & Geller (1993, Arch. Hydrobiol. 126: 315-327) appears to be the best pred~ctor of maxlmum growth rate from cell volume and ambient temperature. Finally, based on the review of growth data for these 2 genera, some speculations are made as to how these ciliates may exploit prey populations in a planktonic environment composed of small-scale patches.

“…1). The most likely source of error introduced months (Haigh & Taylor 1991). This observation sugby using t h~s sampling platform was the inclusion of gests that differences in species compositions of phytobenthic species with pelagic ones, particularly during plankton across fronts can be caused by variations in storms.…”

Section: Introductionmentioning

confidence: 99%

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

La¹,

Mr²

1997

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.