Eighteen Pediococcus strains were screened for their potential as silage inoculants. Pediococcus acidilactici G24 was found to be the most suitable, exhibiting a short lag phase on both glucose and fructose, a rapid rate of acid production, a high sugar-to-lactate conversion efficiency, no detectable breakdown of proteins or lactic acid, and the ability to grow within a broad range of pH and temperature. When tested in laboratory silos using grass with a water-soluble carbohydrate content of 24 gfkg of aqueous extract, P. acidilactici G24 stimulated the natural LactobaciUus plantarum population and accelerated the rates of lactic acid production and pH decrease. After 6 days of fermentation, the inoculated silage exhibited a 12% decrease in ammonia nitrogen and an 11% increase in crude protein levels compared with uninoculated controls. The use of an L. plantarum inoculant at a rate of 104 bacteria per g of grass in conjunction with P. acidilactici G24 produced no additional beneficial effect. Inoculation of grass with a water-soluble carbohydrate level of 8 g/kg of aqueous extract with P. acidilactici G24 led to no acceleration in the rate of L. plantarum growth or pH decrease. However, after 7 days of fermentation the inoculated silage had a 14% lower ammonia nitrogen protein content than did uninoculated controls. The results suggest that P. acidilactici G24 may be useful as a silage inoculant for crops with a sufficiently high water-soluble carbohydrate level.

The abundances, population dynamics and production of the rotifer community of Lough Neagh were examined for a three year period. Keratella cochlearis was the most abundant species accounting for over 40% of biomass followed by Polyarthra dolichoptera and Notholca acuminata. The mean standing crop for the rotiferan zooplankton increased in successive years (41, 51, 75 mg dwt m-2) as did production (1037, 1322, 1417 mg dwt m-2 y-'). The seasonal pattern of biomass expression and production varies markedly in different years. Instantaneous birth rates tend to be lower but more consistent for the more abundant species, instantaneous death rates show periods of negative mortality indicating an inadequacy of the model employed but explicable as hatching of resting eggs. K. cochlearis as the most successful species is explained as its perennial appearance and adaptation to the low annual temperature cycle found in the lough. The population succession and the annual occurrence of species differs in each year.

A Limnological Reconnaissance of the Lough Erne System, Ireland key words: Lough Erne, Ireland, phosphorus budget, chlorophyll a map Abstract The Lough Erne System (Northwest Ireland) consists of two linked eutrophic lakes. Phosphorus input budgets suggested mean catchment exports of 30-62 kg total P km-2 a-1, resulting in a heavy P loading to the small upper lake. The export of soluble P is related t o the human population density in the catchment. Although complex in outline, the upper lake has similar phytoplankton populations throughout, but the populations in the simpler shaped lower lake differ quantitatively and qualitatively from place to place. This is probably due to differences in mixed depth. A chlorophyll a map of the surface water of the lower lake, obtained by fluorometry, showed the relationship between algal biomass and depth of water.

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An amylolytic LactobaciUus plantarum silage strain with the starch-degrading ability displayed by Lactobacilus amylovorus was developed. An active fragment of the gene coding for ca-amylase production in L. amylovorus was cloned and integrated into the chromosome of the competitive inoculant strain L. plantarum Lp8O at the cbh locus. The a-amylase gene fragment was also introduced into L. plantarum Lp8O on an autoreplicative plasmid. Both constructions were also performed in the laboratory strain L. plantarum NCIB8826. All four recombinant strains secreted levels of amylase ranging from 23 to 69 U/liter, compared with 47 U/liter for L. amylovorus. Secretion levels were higher in L. plantarum NCIB8826 than in L. plantarum Lp8O derivatives and were higher in recombinant strains containing autoreplicative plasmids than in the corresponding integrants. The L. plantarum Lp8O derivative containing the L. amylovorus a-amylase gene fragment integrated into the host chromosome secreted at-amylase to a level comparable to that of L. amylovorus and was stable over 50 generations of growth under nonselective conditions. It grew to a higher cell

1. Reduced total phosphorus concentrations in the summer which followed the addition of iron aluminium sulphate to White Lough failed to reduce significantly the phytoplankton. which continued to be dominated by Oscitlatoria agardhii var. isothrix Skuja. This species was present throughout the 4 years studied, forming over 50% of the algal volume in 80% of samples. In contrast, species which occurred principally in the summer months were found lo be severely curtailed when sediment release of phosphorus was suppressed.2. The phosphorus: carotenoid ratio was used to assess the extent of phosphorus limitation because laboratory studies on O. agardhii var. isothrix showed that this ratio was a much better indicator of cell phosphorus content than the phosphorus:chlorophyll a ratio. Reduced summer phosphorus concentrations in White Lough caused a transition from intermittent to continuous phosphorus limitation rather than a proportional reduction in the summer phytoplankton.3. Reduced autumn grazing pressure by Daphnia hyatina Leydig allowed large algal populations to develop in the winters following phosphorus reduction despite a 50% decline in total phosphorus. The combination of increased winter phytoplankton and lower total phosphorus reduced soluble reactive phosphorus concentrations to less than 5,«g P r^ which in turn curtailed the spring diatom pulse.

A procedure for isolating axenic cultures of planktonic blue-green algae is described that relies on a filtration procedure to produce a high filament : bacteria ratio and a subsequent serial dilution to isolate axenic algal filaments. Six axenic cultures have been prepared and their growth kinetics compared with the corresponding bactericized cultures. In continuous light, two axenic cultures exhibited sub-optimal growth whereas the remainder grew essentially as well as their bactericized counterparts. By contrast, under a light : dark regime two axenic cultures exhibited significantly better growth, and another, significantly poorer

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