Macrobenthos associated with a population of Anthothoe chilensis (Lesson, 1830) (Cnidaria, Actiniaria) in Mar del Plata Harbor, Argentina

Abstract

Diversity and seasonal variations of 54 macrobenthic taxa associated with a population of the sea anemone Anthothoe chilensis were studied at Mar del Plata harbor, Argentina. Sea anemones and their associated flora and fauna were collected seasonally by diving between 2 and 3 m depth. The number of associated individuals was variable, with highest values in summer (2110.7 ± 368.8 ind/100 cm²). In the community analyzed, crustaceans were dominant; amphipods were the most abundant, but only gammarids showed a seasonal abundance, being dominant during summer (1868 ± 373.2 ind/100 cm²). Therefore, diversity and evenness showed the lowest values during this season, but the decrease in the number of crustaceans in late summer resulted in greater uniformity of abundance and diversity in the other periods. Nematodes (174.9 ± 34.2 ind/100 cm²) and cirratulid polychaetes (80.5 ind/100 cm²) were most abundant during the cold season. Pycnogonids showed their greatest abundance (63.97 ind/100 cm²) and species richness (4) in spring; these organisms find refuge and substrate among the bryozoans Bugula stolonifera and Bicelariella sp., which were most abundant in the same season. Anthothoe chilensis was found throughout the year forming dense patches, with minimal abundance in spring (91.5 ± 1.0 ind/100 cm²). The actiniarian Tricnidactis errans was observed coexisting with A. chilensis, but in low number (0.5 ± 0.5 to 4.33 ± 2.92 ind/100 cm²).