Pollution reduces native diversity and increases invader dominance in marine hard‐substrate communities

Abstract

Anthropogenic disturbance is considered a risk factor in the establishment of non‐indigenous species (NIS); however, few studies have investigated the role of anthropogenic disturbance in facilitating the establishment and spread of NIS in marine environments. A baseline survey of native and NIS was undertaken in conjunction with a manipulative experiment to determine the effect that heavy metal pollution had on the diversity and invasibility of marine hard‐substrate assemblages. The study was repeated at two sites in each of two harbours in New South Wales, Australia. The survey sampled a total of 47 sessile invertebrate taxa, of which 15 (32%) were identified as native, 19 (40%) as NIS, and 13 (28%) as cryptogenic. Increasing pollution exposure decreased native species diversity at all study sites by between 33% and 50%. In contrast, there was no significant change in the numbers of NIS. Percentage cover was used as a measure of spatial dominance, with increased pollution exposure leading to increased NIS dominance across all sites. At three of the four study sites, assemblages that had previously been dominated by natives changed to become either extensively dominated by NIS or equally occupied by native and NIS alike. No single native or NIS was repeatedly responsible for the observed changes in native species diversity or NIS dominance at all sites. Rather, the observed effects of pollution were driven by a diverse range of taxa and species. These findings have important implications for both the way we assess pollution impacts, and for the management of NIS. When monitoring the response of assemblages to pollution, it is not sufficient to simply assess changes in community diversity. Rather, it is important to distinguish native from NIS components since both are expected to respond differently. In order to successfully manage current NIS, we first need to address levels of pollution within recipient systems in an effort to bolster the resilience of native communities to invasion.

Patterns and processes of compositional change in a California epibenthic community

“…by increasing growth rate and competitive ability of nonnatives). Increases in pollution (Piola & Johnston 2007) or decreases in predators (Sutherland 1974, Karlson 1978, Nydam & Stachowicz 2007 are both known to influence the relative abundance of natives and non-natives in fouling communi- Non-native tunicates Non-native bryozoans Table S1 in the supplement at www.int-res.com/articles/suppl/m435p063_supp.pdf), and recruitment rates are inter polated between samplings to create a smoothed line. Missing data are as follows: April 2005, August 2007, and April to June 2008.…”

Latitudinal Patterns of Biological Invasions in Marine Ecosystems: A Polar Perspective

“…In marine systems, literature on the role of disturbance in invasions has focused primarily on anthropogenic sources of disturbance (e.g., Ruiz et al, 1999;Piola and Johnston, 2006). Past studies have especially considered effects of fi sheries exploitation, changes to habitat structure (whether physical or biological in nature), and chemical pollution.…”

Morphology of the Invasive Amphiphyte Alternanthera Philoxeroides Under Different Water Levels and Nitrogen Concentrations

“…One generally accepted idea is that a plant's invasiveness is enhanced by an increase in the amount of resources (Davis et al, 2000). According to this view of fluctuating resource availability, a disturbance can facilitate the invasion of an alien species into a community by increasing the resources available to the invasive species or by reducing the resource use of the native species (Hobbs and Huenneke, 1992;Davis et al, 2000;Piola and Johnston, 2008).…”