The Ecology of Phytoplankton

332 COMMUNITY ASSEMBLY IN THE PLANKTON
Table 7.5 Summary of phytoplankton seasonality in 19 stratifying lakes in the English Lake District,
according to Kadiri and Reynolds (1993), rendered in terms of the trait-differentiated functional-groups of
Reynolds et al. (2002) (see also Table 7.1)
TP, c.1991
Class Lake Area (km 2 ) (µg PL −1 ) Phytoplankton
Larger oligotrophic
lakes
Larger mesotrophic
lakes
Well-flushed
short-retention
lakes
Wast Water,
Ennerdale Water,
Thirlmere,
Crummock Water,
Buttermere
Derwent Water,
Hawes Water,
Coniston Water
Brothers Water, Rydal
Water, Grasmere,
Bassenthwaite Lake
Eutrophied larger lakes Windermere (North),
Ullswater,
Windermere
(South), Esthwaite
Water, Lowes
Water
Enriched small lakes Loughrigg Tarn,
Blelham Tarn
E. In summer, the biomass generally falls to
aphosphorus-depleted minimum during which
the nanoplankton diversifies with algae such as
Chrysococcus, Monochrysis, Pseudopedinella, Bicosoeca
tubiformis and Koliella longiseta recruiting (from
X3). Picoplankton may also be numerous, some of
which may well be Chroococcoid (Z) butsome is
eukaryotic (including Chlorella minutissima, which
Reynolds et al. (2002) placedinX3. These lakes
have the potential to support metalimnetic maxima
of (group-R) Planktothrix, although the numbers
of P. mougeotii produced are generally small.
Cyanobacteria are mainly represented by modest
growths of Anabaena solitaria and A. lemmermannii
(of group H2) andbycolonies of Woronichinia
(formerly Gomphosphaeria) that, together
with dinoflagellates Peridinium willei, P. inconspicuum
and Ceratium species, represent group LO.
Tabellaria flocculosa and Cosmarium species (including
C. abbreviatum and C. contractum) make up
0.9–3.0 3–9 A → Z/LO → N
3.9–5.4 7–11 B(C) → X2/F/E →
X3/Z/LO/Y → N/R
0.2–5.3 4–33 B or C → X1/X2 →
Y (E, F, H2, P)
0.6–9.0 14–40 C(B)
→X1/X2/Y/G→
H/LM/S/T → P
≤0.1 20–45 C/Y → X1/X2 /E/F
or H1 → LM → P/S
the phytoplankton stimulated by late-summer
and autumnal mixing. Phytoplankton biomass is
faintly diacmic in these lakes, the spring peak
(in the order of 6–15 µg chla L −1 )usually being
the larger. The level of MRP generally falls below
detection limits for between four (May–August)
and nine (March–November) months of the year.
The summary notation shown in Table 7.5 for
‘larger mesotrophic lakes’ also fits well to the patterns
among the greatest Scottish lochs (Bailey-
Watts and Duncan, 1981).
Several further lakes are, to varying extents,
enriched beyond the mesotrophic state. Since the
mid-1960s, Windermere and Ullswater have been
subject to the discharge of effluents from secondary
sewage-treatment works. Esthwaite Water
was already a eutrophic lake before sewage treatment
affected its waters. Lowes Water has a
low human population in its catchment and
the reason for its enrichment is not resolved.