An ecological investigation of the intertidal benthic invertebrates of the Dee Estuary

Gillham, RM

Abstract

The aim of the thesis was the investigation of the intertidal macroinvertebrate distributions of the Dee Estuary and the factors controlling their distributions.
The work consisted of a series of extensive systematic grid
surveys over the Estuary in the Spring and Autumn covering a period from 1971-76, backed up with more intensive stratified random sampling in selected representative areas of the Estuary. The environmental factors investigated included salinity, temperature, particle size, percentage loss on ignition, tidal height but as the work progressed two other factors were found to be of great importance, these were the degree of protection from
wave action and the effect of predation.
Five consistent biological communities were defined for each of the surveys by objective numerical analysis techniques (Normal Association Analysis) and it was found possible to relate each of these communities to a unique set of physical/chemical factors.
The data obtained in the initial stages of the study revealed the possibility of a balance in the relationship between the invertebrates and their predators which included other invertebrates, estuarine fish and birds.
Analysis of the predation rate on Macoma balthica data revealed a mathematical relationship and an apparent minimum feeding density by the predators.
The hypothesis was tested further by a variety of techniques including experiments with netted exclosures constructed on the Estuary and all the available evidence from the study substantiated the hypothesis.

• Thesis Type: Thesis
• Deposit Date: Jun 16, 2009
• Publicly Available Date: Jun 16, 2009
• Additional Information: Additional Information : PhD supervisor: Dr M. Pugh Thomas
• Award Date: Jan 1, 1978