EPA's Vessel General Permit and Small Vessel General

(Kahng and Grigg 2005).
The introduction of novel pathogens into a habitat can cause overwhelming infections,
particularly when coupled with stresses of a disturbed environment which corals must already
cope (Lesser et al. 2007). In the Caribbean, endangered elkhorn and staghorn coral (Acropora
palmate and A. cervicornis) face severe declines in part due to diseases, including white pox and
white plague type II. These coral diseases are caused by various species of the genus Vibrio,
which have been identified in ballast water of vessels (Anguiano-Beltrán et al. 1998, Ben-Haim
and Rosenberg 2002, Aguirremacedo et al. 2008). Thus ANS invasions are likely to reduce the
survival of corals through competition and disease.
Johnson’s Seagrass
The species is likely to be adversely affected by ANS through the mechanisms of competition
and disease transmission. For example, the introduced seagrass, Zostera japonica, has led to the
decline of native seagrasses and ecosystem function (Williams 2007). The “wasting disease”
that devastated New England eelgrass populations in the 1930 has be transmitted to native
seagrass communities via ANS (Minchin 2007). Johnson’s seagrass has the most limited
geographic distribution of any seagrass in the world (Kenworthy 1997). In its native Florida
habitat, 50 ANS have become established (Courtenay 1997), 23 of which are aquatic plant
species (McCann et al. 1996). Disease would likely spread quickly through the small population.
An invasive seagrass is likely to overgrow the endangered seagrass beds throughout its small
range. Therefore, we conclude that ANS are likely to reduce the survival of Johnson’s seagrass
through disease and competition.
Extinction and Endangerment as a Result of ANS Invasions
In our Exposure Analysis, we concluded that threatened and endangered species and their
designated critical habitat are likely to be exposed to ANS in the following discharges: ballast
water, hull fouling/underwater husbandry, sea cooling systems, and chain lockers. In our
Response Analysis, we concluded that listed individuals exposed to ANS invasions are likely to
experience reduced fitness as a result. Here we ask whether these reductions in fitness are likely
to reduce the viability of populations and species. We start by reviewing the published scientific
literature on species endangerment and extinction as a result of ANS invasions.
The introduction of non-native species poses one of the greatest threats to biodiversity, second
only to habitat loss (Wilcove et al. 1998). In the United States, more than 40% of species listed
under the ESA are threatened by invasive species (Wilcove et al. 1998). The ANS Task Force
identifies ANS as a major cause of decline of species and a significant impediment to their
recovery (http://www.anstaskforce.gov). The detrimental effects of ANS have contributed to
68% of North American fish extinctions over the past century, including two Oncorhynchus
species (Miller et al. 1989). A study by USGS (2012) identified ANS as a contributing factor in
the listing of more than 50% of fish species and 33% of invertebrate species listed under the
ESA. Some argue whether invasive species are the primary cause of endangerment or
extinction, but it is widely agreed that listed species become further imperiled as a result of ANS
invasions (Gurevitch and Padilla 2004, Clavero and Garcia-Berthou 2005).
237