Effects of piers on assemblage composition, abundance, and taxa richness of small epibenthic invertebrates
2017
Cordell, Jeffery R. | Munsch, Stuart H. | Shelton, Melora E. | Toft, Jason D.
We examined the effects of two types of piers on composition, abundance, and diversity of small epibenthic invertebrates and on several taxa known to be important prey for juveniles of three species of Pacific salmon. Using an epibenthic pump, invertebrates were sampled under and away from piers. Piers located within a dense urban aggregation of overwater structures and ferry piers occurring singly in less urbanized landscapes negatively impacted small invertebrates. Except for polychaetes at ferry piers and the harpacticoid copepods Tisbe species at urban piers, taxa richness and densities of invertebrate groupings and several juvenile salmon prey taxa were significantly decreased underneath both pier types and also near the edge of ferry piers. Assemblage structure was also greatly influenced by piers, with under-pier assemblages dominated by Tisbe species and several other taxa, and assemblages outside piers characterized by many taxa. Many of the negatively impacted taxa are associates of algae and seagrasses that were reduced under the piers. For juvenile salmon and other fish, reducing shade under piers by adding light to the environment may improve habitat access and quality in areas where piers decrease fish feeding opportunities.
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