Key Words: botryllid ascidian, species identification, genetic markers, life-history variation
Successful invasions of botryllid ascidians have been documented worldwide both recently and over the past 50-100 years. Ascidians, including botryllids, are now recognized as important invaders overtaking fouling communities and interfering with bivalve culture. What are the sources of these invasions, how many species are involved, and how might these invasions be controlled? These questions have not been easily answered due to problematic taxonomy for many ascidians including the botryllids. Molecular identification of problematic taxa, by comparing known voucher specimens from potential source populations with specimens from invading populations, is a promising technique for invasion tracking. Here, I show that genetic markers such as small ribosomal subunit and mitochondrial cytochrome oxidase DNA sequence data may be used to distinguish species of botryllids. Genetic information on North American botryllids on both coasts reveals more distinct species than previously understood from morphological characters. Behavioral and life-history variation between populations has raised the possibility of rapid differentiation or plasticity in introduced populations. I discuss multiple character approaches to distinguishing botryllid species including methods for collecting and preserving useful voucher specimens. Careful study of botryllid invasions should answer questions about mechanisms of invasion for a diversity of taxa with limited natural mechanisms of dispersal.
Author to contact: C. Sarah Cohen
Zoology Dept./Shoals Marine Lab
Univ. of New Hampshire
Durham, NH 03824
T 603-862-1023
F 603-862-3784
Email: cscohen@hopper.unh.edu
Key Words: public education and outreach, non-indigenous species
The introduction of non-indigenous species into the coastal waters of the Pacific Northwest poses a serious economic and environmental threat. Adverse impacts are of increasing concern to resource managers, the aquaculture industry, non-governmental organizations and concerned citizens. Recognition that invasive species can affect fisheries, waterways, public and private facilities, as well as the functioning of natural ecosystems, is increasing.
An informed and educated public is widely recognized as the cornerstone of effective prevention and control of aquatic nonindigenous species (Jensen 1998). To achieve this end, it is essential that information/education efforts convey up-to-date and accurate facts that are appropriately targeted and offer a consistent message. Washington Sea Grant Program has begun developing a series of NIS educational products in collaboration with the State of Washington, the National Estuary Program, the U.S. Fish and Wildlife Service, and the Georgia Basin/Puget Sound International Task Force. The goal of these educational products is to increase awareness of NIS and their potential impacts on the environment and economy.
Public awareness is a realistic and cost-effective method to prevent or slow the introduction of NIS. Although the need to regulate intentional introductions of non-native species has long been recognized, we are only beginning to understand some of the pathways that transport new species into coastal and inland waters. Many of these pathways cannot be regulated. Since a single boat carrying zebra mussel or a boat trailer with Brazilian Elodea tangled on it can bring an infestation to a watershed, it is only with the aid of an educated public that we can block the introduction of NIS through certain of these pathways. Yet the concept of NIS is often unknown to large sectors of the public. Greater public awareness of the problem and how individual actions play a role in the transmission of NIS is essential to slowing or preventing introductions.
Among the educational products being produced by
the Washington Sea Grant Program are:
A 20 pp. booklet entitled "Bio-invasions: Breaching Natural Barriers,"
which explains in simple, clear terms the threat of non-native aquatic
species and potential impacts on the economy and on the environment;
Fact sheets on common pathways for aquatic NIS introductions and
the European green crab (Carcinus maenas);
A full color identification card for the European green crab, including
features that distinguish them from similar-looking native crabs;
A training workshop on identification of the European green crab
for volunteer groups, industry workers, tribes and agencies;
A poster and T-shirts introducing the concept of invading species
with an eye-catching design and a simple explanation of what invading
species are and how they can be transported; and
A card for distribution at pet stores and other venues explaining
why aquarium hobbyists should not release pets or plants into the
wild and suggesting alternatives to dumping.
Strategies for targeting appropriate audiences, determining vehicles and delivery mechanisms for reaching those audiences, and evaluation methods for determining their effectiveness will be discussed.
References
Jensen, D. 1998. Make public information and education your priority.
In: Proceedings of the Eighth International Zebra Mussel and Aquatic
Nuisance Species Conference, J. Cassell, Ed., University of California,
Davis, California, pp. 163.
Author to Contact: Nancy Lerner
Washington Sea Grant Program
Office of Marine Environmental and Resource Programs
University of Washington
3716 Brooklyn Avenue, NE
Seattle, WA 98105-6716
T 206-616-8403
F 206-685-0380
Email: njlerner@u.washington.edu
Keywords: Habitat modification; facilitation; scale-dependence; mussel mats
Nonindigenous species capable of physically altering habitats can have a wide variety of effects on resident biota. One such introduced habitat modifier (or ecosystem engineer) is the small mytilid mussel, Musculista senhousia. The effects of this invader, which can form high-density mats on the surface of soft sediments, appear scale-dependent. At larger scales, surface-dwelling, suspension-feeding clams are competitively inhibited. At smaller scales, however, the mussels benefit a variety of resident biota. These facilitory effects are mediated primarily by the physical architecture provided by the mats, although the activities of living mussels influence some species. The effects observed for M. senhousia appear to be general for a variety of aquatic and terrestrial invaders capable of altering the physical nature of habitats, and include positive effects of invaders that increase habitat complexity.
Jeff Crooks
Scripps Institution of Oceanography
Mail Code 0218
La Jolla, CA 92093-0218
T 619-534-3579
F 619-822-0562
Email: jcrooks@ucsd.edu
Key Words: eradication, marine pest, sabellid, polychaete, abalone
Once a marine invader has become established its subsequent control has been met with little more than fatalism. However, as illustrated by the case of the sabellid worm, such an outlook may not be warranted. A previously unknown species, this sabellid polychaete arrived as a contaminant on imported South African abalone and was initially contained in California abalone mariculture facilities. The sabellid infestation caused shell deformation and slowed growth of the cultured abalone, resulting in great economic losses to the industry. However, having broad host specificity, its potential impacts are not confined to just abalone; it can readily infest many other native California gastropods. We detected an established population at an intertidal site near Cayucos, California in 1996. To mitigate the impact of this introduced marine pest at this site and prevent or slow its geographic spread, we proposed an eradication program based on the epidemiological theory of the threshold of transmission. That is, if the density of transmissive stages and the density of highly susceptible hosts are reduced below the replacement transmission rate, successive generations of the pest will damp out. Specifically, our eradication program includes three components: (1) prevention of further release of adult worms from the facility, (2) reduction of the adult pest population and (3) reduction of the most susceptible native host population. This three-fold approach is unique in that it not only targets the pest, but also a component of the pestís life cycle - the host - which is required for continuance of the established population. The eradication program has been implemented in collaboration with the associated mariculture facility and the California Department of Fish & Game. Using transect surveys and mark and recapture studies, we have monitored the success of the eradication efforts. April 1998 surveys found new infestations had, at least temporarily, been eliminated. This potentially successful eradication program suggests the need for - and has depended on: (1) early detection, (2) cooperation between commercial interests, regulatory agencies and pest control scientists, (3) rapid response (avoidance of analysis paralysis), (4) development of a control strategy with a theoretical basis, (5) persistent efforts beyond the point where the situation has merely improved and (6) monitoring of eradication efficacy through use of sentinel habitat experiments. The current status of our eradication program and implications for use with other introduced species will be discussed.
Author to Contact: Carolynn (Carrie) Culver
Marine Science Institute
University of California
Santa Barbara, CA 93106
T 805-893-3998
F 805-893-8062
Email: c_culver@lifesci.ucsb.edu
Key Words: management, Delaware, pathways
The introduction of aquatic nonindigenous species has the potential to cause significant environmental and economic harm in Delaware waters, as it has throughout the world. To date, the extent to which Delaware waters are invaded by nonindigenous species has not been assessed. Likewise, an examination as to effectiveness of Delaware's current management framework to prevent and control nonindigenous species has yet to be conducted.
Through literature searches and interviews with Delaware natural resource officials, approximately forty (40) nonindigenous species were found in Delaware's fresh, brackish, and marine waters. Six of these were considered nuisance species, costing the State a significant amount in control efforts. Of the five principal pathways of introduction highlighted in the literature (stocking programs, shipping, recreational boaters and anglers, aquarium and ornamental releases, and aquaculture), all five were likely responsible for some introductions into Delaware waters. Ballast water discharges and recreational boating and angling pose the greatest potential risk for introducing nonindigenous species into Delaware, although no one pathway appeared to be especially dominant. This rough assessment was based on the number of known harmful species likely being introduced (e.g., the number of ships discharging ballast water potentially containing harmful nonindigenous species into Delaware Bay).
Interviews were conducted with personnel in six state-level nonindigenous species management programs (Chesapeake Bay, Lake Champlain, New York, Michigan, Minnesota, and Puget Sound). Lessons drawn from these current efforts might prove helpful in devising a management strategy for Delaware. The majority of programs focused exclusively on aquatic species (rather than an all encompassing terrestrial and aquatic species approach) and utilized education as the primary management tool. Stakeholder inclusion was a key component of the development process. Many policies became stymied by low recognition of the issue, leading to deficiencies in staff and funding, which in turn adversely affected implementation.
Effective state-level nonindigenous species management is hampered by five shortcomings: inadequate baseline information, insufficient authority, delays in response time, lack of an institutional framework, and low levels of support for action. I addressed these deficiencies through five corresponding policy prescriptions. The proposed measures set forth to close loopholes in the current regulations, establish a nonindigenous species monitoring program, create a mechanism to coordinate management actions, and call for education targeted at the responsible parties.
Author to Contact: Forbes Darby
Center for the Study of Marine Policy
Graduate College of Marine Studies
Robinson Hall
University of Delaware
Newark, DE 19716
T (302) 831-8086 (W)
(410) 620-2179 (H)
F (302) 831-8086
Email: fdarby@udel.edu
Key Words: multilocus, genetic, DNA, population, source
Advances in genetic technology have enabled biologists to reconstruct the history of populations, their evolutionary relationships and geographical origins. Such information is essential in understanding the biology of invasions and in designing successful management responses. Unfortunately, the wholesale transfer of 'traditional' population genetic methodology to identify the origins of marine bioinvasions is inappropriate. By definition, invading populations are characterized by their rapid and recent range expansion. This has two important genetic consequences: (i) genetic diversity is often very low due to the bottlenecks in population size associated with the founding of new populations, and (ii) evolutionary relationships among genes may bear no relation to the history of populations. These characteristics of invading species limit our ability to reconstruct their geographic history. Here, we evaluate the genetic markers and statistical methods currently being used to determine the invasion pathways of species of economic importance in agriculture and fisheries. Analyses of molecular genetic data fall into two categories: those based on phylogenies, and those based on frequency differences of genetic markers. Here, we describe these two approaches and outline the conditions under which they are appropriate and useful in marine bioinvasions. Of critical importance are factors such as effective population size, time since the separation of populations, magnitude of gene flow among populations, and rates of genetic recombination. Despite its intuitive appeal, a phylogenetic analysis of genotypes relative to geography (known as phylogeography) is often inappropriate for tracing the history of very recently founded populations. Although phylogenies in such situations are useful for determining the homology of alleles and understanding patterns of mutation and recombination, statistical analyses of multilocus genotypes are required to resolve historical relationships for many invading populations.
Author to Contact: Neil Davies
Center for Conservation Research and Training
University of Hawaii
Gilmore 409, 3050 Maile Way
Honolulu, HI 96822
T 808-956-3744
F 808-965-9608
Email: ndavies@hawaii.edu
Key Words: microbial ecology, Biolog, Chesapeake Bay, ballast water
Microbiological studies of ballast water will help us understand the transfer, dynamics, and invasion potential of microorganisms carried by ships (see related abstracts by Rawlings et al. and Drake et al.). We have begun to characterize the ballast water bacteria in samples collected from ships arriving in the lower Chesapeake Bay. Such characterization is based on interpreting substrate-utilization patterns. We inoculate ballast-water samples into Biolog microtiter plates (Biolog, Inc., Hayward, CA), which contain 95 different carbon substrates in separate wells. These wells, and a control well, also contain a tetrazolium salt that indicates (via color development) microbial utilization of a substrate. The rate and extent of a substrate's utilization is determined through time-series measurements of a well's optical density.
There has been a wide range of response among the ships (n=13) sampled to date; clearly the bacterial assemblages of ballast waters vary considerably. In more than half the cases, however, there are commonalities in response that may be influenced by duration of voyage, source water, and exchange history. In addition to its furthering our understanding of ballast-water ecology, this technique potentially has uses for routine monitoring of arriving ships and evaluating the efficiency of water exchange or filtration.
Author to contact: Fred C. Dobbs
Department of Ocean, Earth and Atmospheric Sciences
Old Dominion University
4600 Elkhorn Avenue
Norfolk, VA 23529-0276
T 757-683-5329
F 757-683-5303
email: fdobbs@odu.edu
Key Words: Freezing tolerance, Geukensia demissa, Introduced Species, Supercooling
The Ribbed Mussel, Geukensia demissa, native to tidal marshes on the American Atlantic coast, was accidentally introduced to the American Pacific coast over 100 years ago. Mussels native to the Atlantic Northeast (NE) coast experience wide variation in seasonal temperature, including subfreezing winter conditions. To combat potentially lethal winter freezing temperatures, NE mussels use a variety of seasonally induced biochemical and physiological adjustments to tolerate ice in their extracellular fluids. Pacific coast mussels, however, are not exposed to freezing temperatures experienced by their NE counterparts. It was hypothesized that Pacific coast mussels may have lost the adaptive ability to withstand these freezing conditions. I examined the geographic and seasonal variations in the response of Geukensia to subfreezing conditions. Mussels from Connecticut and Southern California were exposed to a variety of subfreezing temperatures. Survival, supercooling point, and final temperature were used as indices of response to freezing. For all indices measured, in a given season there were no significant differences found between California and Connecticut mussels in freezing response. However, a significant difference existed between summer- and winter-acclimated mussels: both California and Connecticut winter-acclimated mussels had significantly different supercooling points (df=1, F=6.37, p<0.05) and final temperatures (df=1, F=24.6, p<0.01). These results support previous literature on changes in seasonal cold tolerance. The fact that mussels from California did undergo seasonal acclimation, despite the lack of strong seasonal temperature cues, lends itself to the role of other environmental cues in triggering winter acclimation. Introduction to the Pacific coast has not resulted in a loss of freezing tolerance of G. demissa.
Author to Contact: Nicole Dobroski
Pomona College Biology Department
609 N. College Ave.
Claremont, CA 91711
T: 909-607-2094
F: 909-621-8878
Email: ndobroski@pomona.edu
Key Words: risk assessment, introduction, pathways, transport vectors
Aquatic nuisance species (ANS) are a growing concern to natural resource and environmental managers. The alarming rate at which nonindigenous species are being both introduced and established is a driving force behind increasing awareness of and proposed actions aimed at ANS issues. However, it is not feasible to address every invasive species concern thus these issues must be prioritized. One conventional method by which land managers have ranked invasive species is via risk assessment. Before managers dealing with ANS rush to adopt these methodologies, we suggest that it is imperative that these tools be evaluated with special attention paid to their applicability in the aquatic realm. Do these risk assessment protocols produce answers that are important to ANS scenarios? That is, are we interested in the same questions that land managers need answers to or do ANS differ fundamentally from terrestrial invaders? Most terrestrial risk models for invaders follow a species oriented predictive risk assessment methodology. We suggest that in the aquatic realm the pathways or transport vectors by which ANS are introduced represent an important step in the invasion process, and one that is neglected in conventional risk assessment. We review risk assessment methodologies currently in use and demonstrate how pathways can be incorporated into these procedures to the benefit of managers concerned about both specific invasive species or general ANS issues.
Person to contact: Robyn Draheim
University of Washington - School of Marine Affairs
3707 Brooklyn Ave NE, Seattle, WA 98105
Phone: 206-685-3270
Fax: 206-543-1417
email: draheim@u.washington.edu
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