Produccion En Rios

Vol. 12: 107-113. 1983

MARINE ECOLOGY - PROGRESS SERIES
Mar. Ecol. Prog. Ser.

Published May 30

Influence of river-ocean plumes upon
bacterioplankton production of the Strait of
G eorgia, British Columbia
L. J. Albright
D epartment of Biological Sciences. Simon Fraser University, Burnaby. B. C., Canada V5A IS6

ABSTRACT: Stin~ulation bacterioplankton glucose heterotrophicactivities and productivities occurs
in
when river water (Fraser, Squamish and Homathko-Southgate rivers) enter the saline surface waters of
the Strait of Georgia, British Columbia, Canada. As the lower salinity water of the Fraser plume (ca.
half of the fresh water flow into this Strait comes from this river) mixes into adjacent surface waters of
the Strait, bacterioplankton production remainssignificant till the salinity exceeds ca. 20 % S. S ince
lower salinity water (i.e. 5 c a. 20 %o S) from rlver plumes covers extensive areas of the Strait of Georgia
during the annual freshet (ca. April to July) there 1s a significant annual bacterial contribution to total
microbial production within this estuarine ecosystem.

INTRODUCTION
T he Strait of Georgia which has a calculated volume
ofca. 1025 km3 of estuarine water, annually receives
about 145 km3 of runoff water, mainly from rivers,
creeks and streams (Waldichuk, 1957). This annual
fresh water addition is thus about 14 % of the volume of
water contained within this semi-enclosed marine
basin. However, because of density characteristics the
fresh water tends to remain at the surface where it
greatly dilutes the seawater. Fig. 1 i llustrates the
relative content of fresh and sea waters within the 0 to
10 m water column of the Northern (area north of the
southern tip of Texada Island) and Central (area
between Haro Strait and the southern tip of Texada
Island) Domains of the Strait of Georgia (Fig. 2). The
fresh water content varies from 14 to 39 % w ith peak
values occurring in the Central Domain inmid-summer. The lowest freshwater concentrations occur during winter (December-March).
The fresh waters of the rivers and creeks which flow
into this Strait are generally bacterial dominated and
many have relatively high silt loads (Seki et al., 1969;
Bell and Albright, 1981; Valdes and Albright, 1981).
The clearer and more stable euphotic waters of the
Straight of Georgia tend to b e microalgaldominated
ecosystems (Parsons et al., 1980).These 2 w ater types
meet and mix in river-ocean plumes where there is a
O I nter-ResearchIPrinted in F. R . G ermany

transfer of significant quantities of microbial biomasses, organic nutrients and silt loads into this strait.
To place this nutrient and microbial transfer by river,
creek and stream flow in perspective it is useful to
calculateapproximate autochthonous and allochthonous organic carbon additions to this strait. Based upon
a water surface area of 6420 km2 (Waldichuk, 1957)
and an estimate of 285 g C m -2 yr-' (Harrison et al.,

0
D

J

F

M

A

M

J

J

A

S

O

N

D

MONTH
Fig. 1. Percent content of fresh and sea waters within the 0 to
10 m w ater columns of Central ( a) a nd Northern(0)omains
D
of t he Strait of Georgia. Replot of data by Waldichuk ( 1957)

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Mar Ecol. Prog. Ser. 12: 107-113. 1983

i n press) as the mean primary production, the annual
phytoplankton production of this strait is ca.
18.3 X 10" g C yr-l. If the total organic carbon (TOC)
content of the lotic systems which enter the strait is
taken as 5 mg 1-' and the total runoff value is 145 km3yr-l this is a calculated addition of approximately
7.3 X 10" g C yr-' to the strait, which is approximately
40 % of the phytoplankton primary production. In an
earlier study Seki et al. (1969) concluded that the
allochthonous organic carbon addition to this strait
was approximately equivalent to the autochthonous
organic carbon production.
A proportion of the TOC of Fraser river fresh...