Revista Chilena de Historia Natural 79 (3): 353-368, 2006
RESEARCH ARTICLE
Community structure of the macroinfauna in the sediments below an
intertidal mussel bed (Mytilus chilensis (Hupe)) of southern Chile
The mytilid mussel Mytilus chilensis (Hupe) can form dense
beds in sedimentary areas of the inland coast of the Nord-Patagonic archipelagos of the Chilean coast (ca. 40-43° S). During the
autumn of 2002, we collected replicated samples at five intertidal stations in Panitao (Golfo de Reloncaví) ordered along a transect
parallel to the low tide level and extended from the center of the bank (stations one and two with 100 and ca. 25 % of mussel cover,
respectively) to the bare sediments of the intertidal (stations 3, 4 and 5, without mussels). The macroinfauna was numerically
dominated by Polychaeta, Oligochaeta and Crustacea Peracarida. The total number of species collected was 14, being the most
abundant the polychaete Perinereis vallata, oligochaetes from the family Tubificidae and the crustacean amphipod
Corophium insidiosum. The number of species, Shannon-Wiener diversity and total abundance of the macroinfauna did
not differ significantly among stations. However, the percent contribution of polychaetes was significantly higher at the sediments
sampled outside the mussel bed (stations three, four and five), while the percentual contribution of oligochaetes was significantly
higher at the sediments sampled in the mussel bed (stations one and two). No significant differences were found between the
percentual contribution of peracarid crustaceans between stations sampled in the mussel bed versus that sampled on the bare
intertidal. The graphic results of NMMDS show that the macroinfaunal assemblage of the stations located inside the mussel bed
differed from that of stations located outside the bed. Results of SIMPER and ANOSIM showed that the macroinfaunal composition of
stations one and two was significantly dissimilar (61-54 %) to that of the stations located outside the mussel bed, which had similar
composition. The graphic results of a NMMDS based upon sedimentological characteristics show that most replicates of station one
and some of station two separate from that of the other stations (i.e. located outside the mussel bed). Results of ANOVA showed
significant differences for all sediment variables, with the exception of percentages of gravel particles and mean grain size of sands.
The most noticeable difference was that shown by station 1 (lower contents of sand and higher content of mud, biogenic aggregates
and total organic matter). The results of BIO-ENV routine showed that the best fit between the taxonomic composition of the
macroinfauna and single sediment variables, was reached with percentages of sand and mud. It is concluded, that mussel beds of
sedimentary bottoms of southern Chile have a significant role on the sediment quality and community structure of the macroinfauna, a
probable combined effect of physiological processes (ingestion of larvae, biodeposition) and the complex physical matrix of the
bed.
Key words:
mussel beds,
Mytilus chilensis, macroinfauna, southern Chile
