Anthropogenic Activities Producing Sink Habitats
for Amphibians in the Local Landscape: A Case Study of Lethal and Sublethal
Effects of Coal Combustion Residues in the Aquatic Environment
Christopher L. Rowe and William A. Hopkins
Introduction
When examining the issue of global amphibian population declines, it is
important to consider amphibian population responses to environmental
changes operating at local scales, influencing specific populations or
habitats and perhaps contributing to larger-scale phenomena (e.g., Rowe,
Hopkins, Coffman, Congdon 2001). Localized effects on habitat quality,
when considered in toto, may result in a landscape that is characterized
by regions of low environmental quality and subsequent negative effects
on amphibian populations. It is thus useful to invoke a "source versus
sink" perspective on the landscape as a whole (sensu Pulliam 1988),
recognizing that a landscape visualized on the basis of habitat quality
will be interrupted in places by regions of low quality associated with
localized anthropogenic activities such as contaminant release (Figure
8E-1). Thus, habitat quality within a landscape will change abruptly from
areas of relatively high quality (source habitats in which recruitment
occurs) to areas of relatively low quality (sink habitats in which immigrants
experience recruitment failures; Figure 8E-1). While adult amphibians
may continue to be present in sink habitats due to migration from nearby
ar- eas, their contribution to the entire population is limited due to
reduced reproductive suc- cess mediated by reduced reproductive output
and/or high embryonic or larval mortality. In such a way, environmental
contamination may produce regions in the landscape (re-productive "black
holes") into which adults fron110cal populations make repeated, losing
investments in reproduction (e.g., Figure 8E-1).
Not all contaminant releases to the environment will result in severe
enough reductions in habitat quality such that amphibian population sinlcs
form in tl1e landscape. The specific effects of contaminants on amphibians
(e.g., their ability to influence recruitment or performance of recruits),
the spatial and temporal nature of contaminant inputs, and the location
of the contamination events within the landscape will determine whether
local amphibian populations may be at risk of contaminant effects. For
example, some contaminants may not affect larval amphibians at environmental
concentrations and, thus, have
SREL Reprint #2767
Rowe, C.L.
and W.A. Hopkins. 2003. Anthropogenic activities producing sink habitats
for amphibians in the local landscape: A case study of lethal and sublethal
effects of coal combustion residues in the aquatic environment. p. 271-282.
In Amphibian Decline: An Integrated Analysis of Multiple Stressor Effects,
edited by G. Linder, S. Krest and D. Sparling. Society of Environmental
Toxicology and Chemistry.
