Effects of trampling by humans on animals inhabiting coralline algal turf in the rocky intertidal

This paper investigates the effects of trampling by humans on the fauna ass ociated with articulated coralline algal turf. Patches of intertidal turf i n a low-use area of the Cape Rodney to Okakari Point Marine Reserve tin nor th-eastern New Zealand) were experimentally trampled over 5 days at three l evels that fell within those measured in a part of the reserve subject to h eavy visitor use. Two days after trampling ended there were similar to 2 . 10(5) individual macrofauna (> 500 mu m) per m(2) in control plots, but den sities declined with increasing trampling intensity in the treatment plots, and were reduced to 50% of control values at the highest trampling intensi ty. Densities of five of the eight commonest taxa were negatively correlate d with trampling intensity, with polychaetes being particularly susceptible to low levels of trampling. Three months after trampling ended densities o f all taxa had returned to control values, with the exception of polychaete s. Reductions in animal densities are tentatively attributed to the loss of turf and associated sand caused by trampling, rather than direct destructi on of the organisms. Given the likely importance of these abundant and prod uctive animals in the rocky reef ecosystem, and their vulnerability to low levels of trampling by humans, we conclude that the effective management of marine protected areas may necessitate total exclusion of humans in some c ases. (C) 1999 Elsevier Science B.V. All rights reserved.