Associations among selected physico-chemical parameters and Simuliidae (Diptera) from 23 lake-outlet sites in Newfoundland

Pérez, J. M. (José M.) (1999) Associations among selected physico-chemical parameters and Simuliidae (Diptera) from 23 lake-outlet sites in Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The association between anthropogenic inputs, often the result of human activity within a watershed, and the structure of the simuliid community were investigated. The environmental analyses showed statistically significant regional and site differences related to the chemical stream variables, but the approach used showed no statistically significant differences in the physical stream variables, except for proximate vegetative cover and physical disturbance scores. The site differences in St. John's were attributed to urbanisation, but the site differences in the other regions could not be associated to specific environmental variables. -- Simuliids were selected for study because they have a passive filter-feeding stage which is susceptible to disturbances associated with increased human activities within a watershed and natural disturbances associated with stream processes. These relationships were investigated using 21 environmental variables correlated to pooled taxa richness, pooled taxa abundance, and final-instar head capsule size using univariate and multivariate statistical methods. -- The biological analyses showed no statistically significant differences in the pooled taxa richness and pooled taxa abundance per region. However, there were statistically significant site differences in the pooled taxa richness and pooled taxa abundance. These differences were correlated to SO₄²⁻, K⁺, Zn²⁺, and Cu²⁺ concentrations. The multivariate analyses, which statistically grouped chemical, physical, and biological variables into composite variables, showed a negative correlation between principal components Environmental Factor III (SO₄²⁻ and Cu²⁺ ion concentrations) and Presence/Absence Factor I (absence of Simulium decorum, S. tuberosum, Eusimulium canonicolum, Stegoptema mutata, and Prosimulium mixtum/fuscum complex). Principal component Environmental Factor III was also negatively correlated to principal component Abundance Factor I (scarcity of P. mixtum/fuscum complex, Cnephia omithophilia, and Simulium tuberosum, and Simulium vittatum). Principal components Environmental Factor II (stream order, average velocity, substrate type, and stream width) and Environmental Factor V (physical disturbance score) were positively and negatively correlated to principal component Abundance Factor II respectively (abundance of Simulium venustum/verecundum complex and E. furculatum, and scarcity of E. craigi/caledonense complex). Final-larval instars of S. vittatum had significantly larger mean head capsules than St. mutata than P. mixtum/fuscum complex. Final-larval instars collected from sites located in the lower reaches of a watershed had smaller mean head capsules compared to final-larval instars collected from the upper reaches which were more variable in size. The pooled taxa richness, pooled taxa abundance, and final-larval instar size of simuliids were useful in detecting environmental differences among regions and sites. However, it was difficult to distinguish among regions and sites with low-to-moderate or variable environmental conditions as in the case of Bonavista, Random Island, and Come-by-Chance.

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