Whittaker, J.E. 1980 The Fleet, Dorset - a seasonal
study of the watermass and its vegetation. Proceedings
of the Dorset Natural History and Archaeological
Society, 100 (for 1978).
Hourly water samples were taken, and measurements
made of salinity, pH, calcium, magnesium, dissolved
oxygen and temperature. Tidal measurements were
made at half hourly intervals over 12-13 hours.
A preliminary bathymetric map was also produced.
Seasonal pH ranges in the Fleet present a picture
of high alkalinity of Fleet waters, especially in
spring and summer months - pH mean of 7.8 in autumn
and winter, but around 8.5 or higher in spring and
summer (pH of seawater is 7.8-8.2). This is considered
to be due to photosynthesis by Zostera in
shallow waters - highest values occurred on Zostera
flats, with lowest values around Abbotsbury in summer
and autumn when water stagnates, and Zostera
is rare. In august 1969 the water of West Fleet
was dark brown with a lower pH than normal, with
associated fish mortality. This was attributed to
a phytoplankton bloom, possibly triggered by farm
pollution. A similar occurrence was reported to
have occurred during the severe drought of 1976.
Dissolved oxygen values of >200% saturation
were recorded from the Fleet in spring and summer,
assumed to be due to photosynthesis by Zostera.
Values of >150%, however, were also recorded
during winter when Zostera has died back.
These were attributed to colder water being able
to take up more oxygen.
Calcium and magnesium values showed a simple linear
relationship with salinity.
Freezing of the Fleet was reported for winter 1963.
Diurnal variations in water temperature of >5EC
from early morning to late afternoon were reported.
algae and Zostera occur in luxuriant abundance
in the Fleet for much of the year; only in winter
and spring are there large tracts of bare mud. Zostera
dies back by late June. Green algae are particularly
common in the lower salinities of West Fleet where
many species form dense mats of vegetation on the
beds of Zostera and often cover large tracts
of the water surface in spring. ... Epiphytic growth
on all seaweeds and Zostera is very well
Ulva is reported as abundant from March to
April, especially in the lower salinities, with
(a number of filamentous species of mainly Cladophora
and Enteromorpha species with some reds),
which dies back in late autumn and may often be
washed ashore in gales. Chaetomorpha spp.
grows mainly in the low salinities around Abbotsbury,
and, to a lesser extent, as far as Lynch Cove. It
is most noticeable in late spring and summer. Two
species of Zostera are recorded from the
Fleet, the more common Z. angustifolia, and
Zostera nana. AZostera
marina is not found in the Fleet, but it does
occur in Weymouth Bay.@
also occurs in West Fleet@.