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Structure of the intertidal fauna on a Galveston groin
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A Galveston groin was surveyed bimonthly from July 1991 through May 1992. Four transacts were established along one side of the groin. Four contiguous quadrats (QI-QIV), each 100 wide x 50 cm height, extended from the top of the groin to the water line, constituted each transect. Paired random numbers were used to locate the sampling points where counting or scraping was performed. Persistence of species was assumed when random ANOVA and Kulczynskils Similarity Index established no differences among the six different periods. Similarity Index detected some similarity when transacts were compared. Stratification indicated that species abundance changed along the four vertical quadrats. This was confirmed by randomized block ANOVA. Quadrat I (QI) was characterized by the presence of Nodilittorina lineolata (Order Mesogastropoda) in some seasons. QII was populated by the above species and Chthalamus fragilis (Subclass Cirripedia). Densities of these two species increased in the QIII zone; other common biota in QIII included Neanthes succinea (Order Phyllodocida), Balanus eburneus (Subclass Cirripedia), Corophium acherusicum (Order Amphipoda), and algae. QIV showed enhancement in diversity and abundance of some species, but abundances of others decreased. C. acherusicum was the overall numerically dominant species. Some physical and biological features may have increased diversity, and probably contributed to the huge densities observed. The two most important physical factors found in lower zones were the deposition of sediment and refuge provided by crevices. Biological factors included barnacles, oysters, and algal colonies, which created sheltered areas for many invertebrates. Other important members on the QIV area were Balanus amphitrite (Cirripedia), Caprelia equilibra (Amphipoda) , and Dynamenella dianae (Isopoda) . Detritivores and suspension feeders were the most abundant trophic categories, resembling, in part, communities on natural rocky shores. Experimental bricks were set in December. In January, they were colonized only by cirripeds. In later months diversity and live coverage increased during spring. In summer those parameters decreased. Distribution of intertidal fauna may be controlled by the interactions of exposure periods, temperature, radiation, sedimentation, shelter, substratum microtopography, predation and dispersionpersistance strategies.
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Includes bibliographical references.
Barraza Sandoval, Jose Enrique (1993). Structure of the intertidal fauna on a Galveston groin. Master's thesis, Texas A&M University. Available electronically from
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