| dc.description.abstract | A survey of aquatic macroinvertebrates associated with water
hyacinth Eichhomia crassipes (Mart.) Solms (Pontederiaceae) in Kenya
waters of Lake Victoria was carried out from January to December
1998. Samples of aquatic macroinvertebrates associated with the
water hyacinth were obtained from five major ecological zones of the
lake. Water hyacinth plants were sampled for the macroinvertebrates
by easing a standard handnet of mesh size 300flm under the mats
and lifting out one or a clump of plants (= 1 sample). Triplicate
samples were collected per habitat per sampling campaign. The
macroinvertebrates were found on the roots of water hyacinth and
between the stems of plants under water. Concurrently, water
parameters: dissolved 02, pH, temperature, conductivity, turbidity and
transparency were measured at the same sites as the
macroinvertebrates. The water parameters were measured at each site
at depth of 25cm below the water surface using appropriate meters.
Overall 130 taxa were collected during the survey. These fell within
seven classes: Insecta, Crustacea, Oligo,.chaeta, Hirudinea, Arachnida, Gastropoda and Bivalvia. Insecta dominated in species richness, ..
abundance and biomass in all ecological zones. Mean (± S.E) total
invertebrate abundance on the landward zones of the fringe ranged
from 2512 ± 413 to 4666 ± 912 indio kg-I of hyacinth dry root.
Whereas in the lakeward zone and on free floating rafts of water
hyacinth plants, the mean abundance ranged from 7576 ± 1502 to
10168 ± 1995 indio kg-1of hyacinth dry root. Overall, free-floating rafts
harboured significantly more macroinvertebrates than fringe mats on
the landward side (F 0.05(15),, 61, P < 0.05). Adult coleopterans were
significantly more in the landward side of hyacinth fringe than on the
lakeward side and in the free floating rafts (F 0.05(1),5,198, P < 0.05).
The mean total invertebrate biomass ranged from 31.806 ± 6.202 to
137.293 ± 39.397 g kg-l of hyacinth dry root. The distribution of the
organisms was strongly influenced by water quality beneath the water
hyacinth plants.
Species diversity was high in all the zones. The mean (± S.E)
species richness ranged from 12.167 ± 1.775 to 15.833 ± 1.4. On the
hand, the mean (± S.E) species heterogeneity ranged from 1.179 ±
0.088 to 1.593 ± 0.075. Both species richness (F 0.05 (1) 4, 120 = 7.585,
P < 0.001) and heterogeneity (F 0.05 (1) 4, 120 = 5.045, P < 0.001) were
significantly different in the various ecological zones/habitat.
Molluscs that are vectors of vanous flukes causmg
Schistosomiasis and related diseases in man and his domestic stock
were collected. These were Bulinus qlobosus, Bulinus nasutu s, Bulinus
ugandae and Biomphalaria pfeifferi. Lymnaea natalensis a vector of
flukes, which cause fascioliasis, was also found associated with water
hyacinth. The distribution of the vectors can be used in the control of
schistosomiasis. Other vectors of human diseases, which were found
on water hyacinth, were larvae of mosquitoes of the genera Anopheles}
Aedes} Culex and Culiseta.
Keywords: Tropical invertebrates, vectors,abundance, biomass and
diversity | en |
