Some ecological observations on a permanent pond in southern England: Primary production and planktonic seasonal succession
✍ Scribed by Anthony R. Russo
- Publisher
- Springer
- Year
- 1978
- Tongue
- English
- Weight
- 911 KB
- Volume
- 60
- Category
- Article
- ISSN
- 1573-5141
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✦ Synopsis
A one year study of a o.9 hectare permanent alkaline pond (mean depth lm) in southern England has shown that phytoplankton productivity was highest during fall and spring . Hourly rates of photosynthesis ranged from almost zero in the winter to a peak of 475 mgC/m 3 /h in the fall . Daily gross primary productivity per unit area varied from 0.1-2 .5 gC/ m 2 / d . The annual gross primary productivity of phytoplankton was estimated to be .157 KgC/m 2 /y .
The submerged angiosperm, Ceratopyllum demersum was the dominant macrophyte covering over 55% of the pond in the summer . It reached a peak biomass of 235 g/m 2 (ash free) in July . This macrophyte had a net annual primary productivity of 2 .89 metric tons (ash free)/ ha/ y . When phytoplankton gross production was converted to net, it showed an energy production of 3 .29 x 106 J/m 2/y compared with 6 .25 x 106 J/m2 /y for macrophytes . Values of net production efficiencies ranged from . i 1% for phytoplankton to .21% for macrophytes .
Cryptomonas dominated the microphytoplankton in terms of numbers for most of the year. Diatoms were abundant especially during the spring bloom . The genus Cocconeis dominated fall and winter diatom standing crops while Cyclotella and Navicula dominated the spring peak . Diatom abundance varied inversely with silica concentrations . Peridinium, the dinoflagellate, seemed to prosper when Cryptomonas was scarce . The colonial alga, Volvox aureus, had an intense growth in October probably due to heavy rains and relatively low nitrogen levels .
The pond zooplankton diversity was low . Copepod and cladoceran populations were predominantly of one species. The copepod Cyclops fimbriatus and the cladoceran Chydorus sphaericus were fall/winter forms . They were succeeded by Cyclops vicinus and Bosmina longirostris in the spring. Rotifers were very abundant during a spring peak prospering on alga] cells produced in the spring bloom two weeks earlier .