Invasions by non-indigenous species (NIS) are recognized as important stressors of many communities throughout the world. Here, we evaluated available data on the role of NIS in marine and estuarine communities and their interactions with other anthropogenic stressors, using an intensive analysis of the Chesapeake Bay region as a case study. First, we reviewed the reported ecological impacts of 196 species that occur in tidal waters of the bay, including species that are known invaders as well as some that are cryptogenic (i.e., of uncertain origin). Second, we compared the impacts reported in and out of the bay region for the same 54 species of plants and fish from this group that regularly occur in the region’s tidal waters. Third, we assessed the evidence for interaction in the distribution or performance of these 54 plant and fish species within the bay and other stressors. Of the 196 known and possible NIS, 39 (20%) were thought to have some significant impact on a resident population, community, habitat, or process within the bay region. However, quantitative data on impacts were found for only 12 of the 39, representing 31% of this group and 6% of all 196 species surveyed. The patterns of reported impacts in the bay for plants and fish were nearly identical: 29% were reported to have significant impacts, but quantitative impact data existed for only 7% (4/54) of these species. In contrast, 74% of the same species were reported to have significant impacts outside of the bay, and some quantitative impact data were found for 44% (24/54) of them. Although it appears that 20% of the plant and fish species in our analysis may have significant impacts in the bay region based upon impacts measured elsewhere, we suggest that studies outside the region cannot reliably predict such impacts. We surmise that quantitative impact measures for individual bays or estuaries generally exist for ,5% of the NIS present, and many of these measures are not particularly informative. Despite the increasing knowledge of marine invasions at many sites, it is evident that we understand little about the full extent and variety of the impacts they create—singly and cumulatively. Given the multiple anthropogenic stressors that overlap with NIS in estuaries, we predict NIS‐stressor interactions play an important role in the pattern and impact of invasions.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1999.44.3_part_2.0950

Non-indigenous species as stressors in estuarine and marine communities: Assessing invasion impacts and interactions

Pileated Woodpecker (Dryocopus pileatus)

Allocation of energy to growth and heat production was measured by constructing energy budgets of male and female Sigmodon hispidus (x Adult body mass = ABM = 113 g d; 105 g ?) and Neotoma floridana (ABM = 270 g d; 184 g ?) from birth to maturity. Energy ingested and oxygen consumption per gram of body mass of post-weaning animals were not significantly different between sexes within species, but did differ significantly between the species. In all animals the relation between post-weaning ingestion (per gram body mass) and body mass follows a negative power function. Post-weaning metabolic rate as a function of body mass follows a different negative power function. The pattern of change in metabolic rate prior to weaning is different in the two species. In Sigmodon, metabolic rate increases linearly from birth to about 20 g (or about 20%o of ABM). The rate at 20 g is about 5 cm3 g-1 h-1. In Neotoma metabolic rate remains constant at 1.7 cm3 -g- -h- from birth to about 26 g (or about 11% of ABM), then increases linearly to about 2.2 cm3 g-1 h-1 at 65 g (29%o ABM). In both species, the peak in metabolic rate and nutritional weaning coincide with development of homeothermy, (measured as ability to maintain adult-level

Relative Allocation of Energy to Growth and Development of Homeothermy in the Eastern Wood Rat (Neotoma floridana) and Hispid Cotton Rat (Sigmodon hispidus)

Much of the research on mercury (Hg) in wild vertebrates has focused on piscivores and other animals at high trophic levels. However, recent studies indicated that insectivorous terrestrial vertebrates may also be at risk. In the present study, we examined blood and fur Hg concentrations as well as the adrenocortical responses of insectivorous big brown bats (Eptesicus fuscus) near the Hg-contaminated South River, VA and a nearby reference area. Baseline glucocorticoids and adrenocortical responses to handling have been widely used to assess the influence of environmental stressors because plasma glucocorticoids rise in response to various physical, psychological, and physiological challenges. Female bats captured at the contaminated site had 2.6 times higher blood and fur Hg concentrations than those captured at the reference site (blood: 0.11 vs. 0.04 μg/g wet weight; fur: 28.0 vs. 10.9 μg/g fresh weight). Fur Hg concentrations at the contaminated site were higher than most wild omnivorous and carnivorous mammals reported in the literature. Although fur and blood Hg concentrations were tightly correlated, fur Hg concentrations averaged 260 times higher than concentrations in blood. This suggests that fur may be an important depuration route for bats, just as it is in other mammals. Despite the high Hg concentrations in bat tissue, we did not observe any site difference in adrenocortical responses. Our results suggest that the bats at the contaminated site were exposed to Hg concentrations below those causing adverse effects on their adrenal axis.

R. L. Livezey

Papers

The Mammals of Virginia.