Changes in benthic assemblages near boardwalks in temperate urban mangrove forests

Boardwalks allow easy access to mangrove forests and are built to enhance their recreational and educational potential. Nevertheless, little is known about any potential impacts of boardwalks on plants and animals in the mangrove habitat. This study investigated the effects of disturbances associated with boardwalks on mangrove macrofauna. Influences at several spatial scales were examined by testing hypotheses about macrofaunal assemblages at different distances from a boardwalk. To examine the generality of findings about an impact, the hypotheses were tested for boardwalks in several mangrove forests around Sydney. At one location (Buffalo Creek), the assemblage of benthic macrofauna was affected within 3 m of the boardwalk. There were fewer of the amphipod Paracalliope australis, the gastropod Assiminea buccinoides and insect larvae near the boardwalk than in areas up to 24 m away. Similar local impacts were found around boardwalks in other mangrove forests, but the taxa affected differed from place to place. At Homebush and Woolooware Bays. there were more polychaetes and fewer gastropods directly adjacent to the boardwalk than in areas further away. Thus, boardwalks were associated with localised, but measurable disturbances to the macrofauna. Responses to disturbances differed from one location to another.