Community composition, structure, and interrelationships in the marine intertidal Endocladia muricata – Balanus glandula association in Monterey Bay, California

Abstract

Studies of the community composition, structure and species interrelationships of the Endocladia-Balanus association were carried out on the rocky shores at the Hopkins Marine Station, Pacific Grove, California, over the period 1959—1961. The organisms making up this biotic association form a horizontal band approximately two feet wide on intertidal rocks. The center of this belt averaged 4.6 ft in surveyed height above tidal datum, but field observations showed that the periods of exposure and submersion actually experienced under a variety of conditions at this level are those predicted for a level of about 3.8 ft above tidal datum. Selected aspects of the relatively mild marine and terrestrial climates were studied in relation to the high and low water periods. The composition of the association was determined from quadrat samples, qualitative collections and field observations. A total of at least 93 benthic and transient species was enumerated, belonging to 15 major groups. Samples taken near the center of the association in different areas and at different seasons demonstrated great similarity and stability in species composition. Thirty-five of the species present in the assemblage were of common occurrence, and where feasible the following aspects of the biology of each were studied: (a) habitat niche, (b) activity patterns, (c) organic matter content of the body (based on the dry weight and nitrogen content), (d) seasonal occurrence, (e) population structure, (f) reproductive activity, (g) food relationships, and (h) growth rate. The most characteristic species were: Rhodophyta-Endocladia muricata, Gigartina agardhii; Platyhelminthes-Notoplana acticola; Nemertea- Emplectonema gracile, Nemertopsis gracilis; Annelida-Syllis spenceri, S. vittata, S. armillaris, Nereis grubei, Perinereis monterea; Bryozoa- Filicrisia franciscana; Mollusca (8 gastropods, 1 chiton, and 3 bivalves)- Acmaea digitalis, A. scabra, A. pelta, Littorina scutulata, L. planaxis, Acanthina spirata, Thais emarginata, Tegula funebralis, Cyanoplax dentiens,