ECOLOGICAL STUDIES AT LOUBH INK
219
of the usual alkalinity for seawater (pH 8.8); the hypolimnion is cold
(8.25-8.5O0C), deficient in oxygen (about 3% saturated in July 1962),
and subnormally alkaline (pH 7.65). The thermocline is centred at about
25 m. In the middle of the South Basin the depth barely exceeds 20 m,
and near the bottom there is a sharp inflection in the curves for temperature, pH, and oxygen saturation, as though to begin a thermocline.
A sharp fall in oxygen saturation was also found near the bottom in the
North Basin. The salinity varies little with depth; all our readings in
July 1952 fell between 34*90x0 and 35.10%,,.
Buoy B
,
Y
#
p H 7 , 6
7,7
7 R
7 , ' )
8 0
R I
8 2
8 3
T
0
20
40
60
80
100%
0
10
#A
?
E
20
f n
n
30
40
8
- d I
nH
A#-- -*'
/C Oxygen solurnlion
FCQ. 17. Temperature, pH and percentage saturation with dissolved oxygen (Alsterberg's
modification of Winkler's method) i n centre of Western Trough on 20 July 1952. Continuous line 11.11-11.40 h. Broken line 16.40-18.03 h. (High slack water about 06.20
and 18.40; low slack water about 14.45 h.)
We have no information about conditions a t other times of year, but
we presume that there is complete mixing in winter.
The temperature of water flowing in through the Rapids ranges in
July between 11.5"C and 15OC; no doubt it depends on conditions in the
sea outside. Presumably the surface waters of the lough are warmed