Key Words: bottom-up effects, community linkages, estuaries, local extinctions, mathematical modeling, monitoring, mudsnails, predictions, relative importance, top-down effects
The exotic mudsnail, Batillaria attramentaria, was introduced to the West Coast of North America in the early part of this century with aquaculture imports of Crassostrea gigas, and has been displacing the native mudsnail, Cerithidea californica. Using data from detailed experiments on these species, we parameterized a model that predicts long term outcomes of the two snails in computer simulations. Quantification of our model from a real system grounded the model in reality and also allowed us to test hypotheses not amenable to field manipulations. We first tested the relative importance of top-down vs. bottom-up effects in driving the invasion of Batillaria. Such an analysis pinpoints the key pathway through which the exotic species achieves the majority of its impact, and also suggests pathways of intervention that will be most successful in controlling or delaying the impact of the exotic species. Results indicate that, for this specific system, exploitative competition is an extremely strong pathway of interaction between the snails and is therefore the link that needs to be broken to hinder the invasion. Secondly, to determine the earliest point that a monitoring program could detect the impact of the invader in the native system, we tested many response variables of the system at the community, population, and individual levels. Examination of these variables over hundreds of simulation replicates indicated that no response variable was able to predict the ultimate demise of the native species until after the presence of the exotic species and its effect on the native species was essentially irreversible. Such a finding suggests drastic implications for how we should generally view monitoring programs and risk assessment analyses.
Author to contact: James Byers
Department of Ecology, Evolution, and Marine Biology
University of California
Santa Barbara, CA 93106
T 805-893-3116
F 805-893-3777
Key Words: ballast water, filtration, nonindigenous species introductions, plankton, pathogens
Three levels of filtration were tested for effectiveness
at screening fresh and salt water organisms from the ballast water
of ships. The three screen sizes (25 um, 50 um, and 100 um) were
evaluated aboard two experimental platforms -- an operating commercial
vessel in the fall of 1997, and a stationary barge in the fall of
1998 -- at a flow rate typical of Seaway-sized ocean-going ships
(1200 gallons per minute). The host ship, the M/V Algonorth, owned
by Algoma Central Marine, plies the Great Lakes/St. Lawrence System
allowing tests in both fresh and salt water. The ship-board experimental
platform consisted of the filter units and a pump mounted on the
deck with piping to matched control and test upper wing ballast
tanks. The stationary barge platform was docked at the Seaway Port
Authority of Duluth in Duluth/Superior Harbor, and consisted of
the same filter units and pump with piping to three identical catchment
tanks of 175 gallons each with bottom outlets. Biological effectiveness
was measured through comparing zooplankton, phytoplankton and microbial
concentrations with and without filtration treatment. Plankton samples
were collected using plankton nets. Whole water samples were collected
to examine chlorophyll and microbial content. The biological effectiveness
experimental design and methods will be summarized. Test results
for both planktonic and microbial organisms will be reported. The
presentation also will include a discussion of lessons learned regarding
experimental design and test procedures.
Author to Contact: Allegra A. Cangelosi
Northeast-Midwest Institute
218 D St. Se
Washington, DC 20003
T 202-544-5200
F 202-544-0043
E-mail: acangelo@nemw.org
top
In terms of broad subscription, the science of marine invasions is no more than 10 years old but, as with all sciences, huge demands are now placed upon it to be robustly predictive. Prediction can be found down several paths, including synthesis and experimentation. Relative to synthesis, because we have so few rigorous regional assessments of bioinvasion diversity, we suffer from a Swiss cheese view of invasion ecology, with far too many holes to produce broad compelling predictions. Critical to the production of such assessments is to attack taxonomic illiteracy -- to revitalize the ability to recognize and identify marine organisms, an ability which is the sine qua non of all ecology and evolution. Critical to the analysis of such assessments will be the resolution of "correction" factors that take into account the profound differences in regional data sets. Relative to experimentation, vastly more effort must be placed on both autexperimental and synexperimental work. Fundamental to all invasion science is a need to be far more rigorous and forthright relative to such concepts as the "effects" of invasions (both in general and relative to individual species), which invasions are "successful" and "unsuccessful" and when invasions will occur (the "Ascidiella Paradox"), the role of "disturbance" in mediating invasions, the reality of selecting "top" invaders, vector complexity, isolation genetics, the geographic origins of specific invaders coupled with the antiquity of invasions (the ubiquity of pre-science shiprints), biases in the recognition of microscopic invasions, the real economic costs of invasions, and the "management" of established invasions. In short, invasion science must become far more quantitative and experimental. Finally, the importance of invasions in coastal community ecology and evolution needs to be seen as a more integral and fundamental element of change in the sea.
Author to Contact: James T. Carlton, Director
Maritime Studies Program
Williams College - Mystic Seaport
Mystic, CT 06355-9000
Email: jcarlton@williams.edu
Key Words: Japanese Shore Crab, Green Crab, interspecific competition, and primary prey species, niche habitat, sediment selectivity
The Japanese Shore Crab (Hemigrapsus sanguineus de Haan) was first introduced to Atlantic waters through ballast water on September 24, 1988 in Cape May, New Jersey. Since then, Hemigrapsus sanguineus has spread at an alarming rate and has become well established on the Atlantic coast. Hemigrapsus sanguineus is now extremely abundant on the Connecticut coastline. H. sanguineus is thought to exploit the different but overlapping habitats on cobble and boulder shores in rocky intertidal habitats (Fukui 1988). In areas where Carcinus maenas (the Green Crab), used to be abundant H. sanguineus is the dominant species and few Carcinus maenas are found. This study focuses on the relative abundance, distribution, and feeding habits of Hemigrapsus sanguineus. Principle prey species for each size class of Hemigrapsus sanguineus was evaluated through stomach content analysis, and competition between these crabs and other indigenous crab species for niche habitat through sediment selectivity was evaluated. The introduction of nonindigenous species and their effects on native habitats is an area of growing concern as commerce and shipping increases. Little is known about this topic especially for marine habitats. This study will provide important base-line data and possible management strategies for future studies concerning Hemigrapsus sanguineus.
Author to Contact: Tara Casanova
Southern Connecticut State University
39 Duncan Street
Wallingford, CT 06492
(203) 269-2117
Project Period: March 1, 1998 - August 1, 2000
This project will provide an outreach program to educate the shipping
industry, government agencies, and the general public about ANS
and ballast management issues relevant to the United States West
Coast and Pacific Region. The three overall objectives of the project
are as follows: (1) to provide education on ANS and ballast management
issues for the maritime industry, resource agencies, and the general
public, and to demonstrate the key role of preventing introductions
of exotic species (and the difficulties and costs associated with
post-invasion control), (2) to educate the maritime industry about
ballast management practices and technologies, and to facilitate
communication and cooperation between the maritime industry, regulators,
and researchers concerned with ballast water management, and (3)
to facilitate industry interest and participation in the development
of ballast management techniques or technologies to provide an alternative
to open ocean exchange. The project will be comprised of five major
components:
(1) A general education publication on West
Coast ANS and ballast management issues. The publication will be
provided to a variety of audiences including the West Coast and
Pacific Region shipping industry, the general public, and natural
resource professionals. The brochure will be utilized for uses ranging
from general education to assisting natural resource professionals
with identification of exotics.
(2) A series of eight video-conferenced educational forums
to increase industry awareness and knowledge of ballast management
issues. Forums will be one-half day events where individuals involved
with the ANS research and the development of ballast management
or ballast technology approaches will be invited to provide a presentation
to representatives of the shipping industry. Locations of the forums
will be rotated between major West Coast ports in California, Oregon,
Washington, Alaska, and Hawaii, and video-conferencing will be provided
to allow for real-time participation by industry members who are
unable to attend the meeting on-site.
(3) The first biannual newsletter and website focused on
ballast management and West Coast ANS issues. The newsletter will
provide summary proceedings from the project forums, as well as
current information on nationwide ballast technology and management
research, and West Coast ANS issues. The project web site will contain
the newsletter, a current article bibliography, announcements, and
linkages to other web sites. Additional general outreach will
be pursued through providing articles and announcements to existing
ANS and maritime publications and websites.
(4) The formation of an industry working group which will
provide a basis for initiation and funding of future West coast
ballast management demonstration projects.
(5) Evaluations conducted for all project activities, and
a final report which will summarize the response of project audiences
to outreach methodologies, and discuss future needs for ballast
water technical assistance and outreach.
This paper will provide an overview of the project, and our project outcomes to date.
Principal Investigator: Jodi Cassell, Marine Advisor
University of California Sea Grant Extension
300 Piedmont Avenue, Room 305A
San Bruno, CA 94066
t 650/871-7559, f 650/871-7399
Email: jlcassell@ucdavis.edu
Key Words: prey selection, amphipod, juvenile fish, experiment
Experiments were conducted to test for native and nonindigenous prey selection by juvenile English sole (Pleuronectes vetulus - native to the West coast of North America). Prey included native amphipods (Corophium salmonis and C. spinicorne) and Northwest Atlantic amphipods (C. acherusicum and C. insidiosum). Single-species and mixed-species predation experiments were utilized in tanks containing sand or mud substratum. Single-species prey consumption in sand substratum was higher for C. spinicorne and C. acherusicum than for C. insidiosum and C. salmonis. Mixed-species prey selection on nonindigenous species in mud substratum and on C. acherusicum in sand substratum was greater than on native amphipods. Predation was greater in sand substratum than in mud substratum on all species but C. insidiosum. No sex-selective predation occurred on any species in either substratum type. Prey size selection was suggested for C. acherusicum in both single and mixed species experiments. Interspecific prey selection may have been affected by water visibility, substratum type, prey exposure, and species composition of the prey population.
Author to Contact : Gonzalo Castillo
Department of Fisheries and Wildlife, Oregon Cooperative Fish and
Wildlife Research Unit. Nash Hall 104. Oregon State University,
Corvallis, OR 97331.
T 541-737-2465
F 541-737-3590
Email: castillg@ucs.orst.edu
Key Words: introduced species; Northeast Pacific; estuaries; global climate; risk analysis; Crustacea; Peracarida
Prolific invasions of northeastern Pacific estuaries by nonindigenous species (NIS) fit a global pattern in which the majority are indigenous to the western sides of the Pacific and the Atlantic. Within the Northeast Pacific, NIS numbers decline with latitude and few native species have invaded western ocean estuaries. Seasonal climate patterns of the northern hemisphere between 25 and 60o N. Lat. are assessed from sea surface temperature and salinity at the origins and at the destinations of common peracaridan crustacean NIS. The regional and global patterns of introductions coincide with variations in climate. Annual sea surface temperatures vary little in the Northeast Pacific relative to those of western ocean coasts and, below 50o N. Lat., low salinities occur in the coldest months rather than the warmest months. Introductions occur only in the range of climate conditions within which species evolve. The proliferation of introductions to the Northeast Pacific may result, in part, from the broad diversity of other climates that encompass the narrow range of climates in the region. Similarly, introductions of native species from the northeast Pacific to other regions may be rare because of the broader range of climate conditions they must endure there. The south to north decline of northeast Pacific NIS coincides with fewer species introductions occurring where greater annual variations in temperature and low summer salinities occur.
Author to Contact: John W. Chapman
Department of Fisheries and Wildlife
Hatfield Marine Science Center
Oregon State University
Newport, OR 97365-5296
T 541-867-0235
F 541-867-0105
Email: Chapman.John@EPA.GOV
Key Words: Membranipora membranacea, Lacuna
vincta, Laminaria spp.
Recently, several introduced species have become established in
benthic communities in the Gulf of Maine. These include the bryozoan,
Membranipora membranacea. The overgrowth of Membranipora
on kelps (Laminaria spp.) has a negative effect on the health
of kelps, and may also have an effect on other marine organisms
including Lacuna vincta that lives and feeds on kelps. To
examine the potential impact of Membranipora on Lacuna
populations, an experiment to determine the growth rate of Lacuna
fed on kelps with and without Membranipora was undertaken.
Lengths of Lacuna were measured every week for one month.
In addition, field samplings were conducted in different depths
of water to compare densities, lengths, and the number of egg masses
of Lacuna on Laminaria spp. with and without Membranipora.
The estimation of percent cover of Membranipora on Laminaria
spp. was also determined. The results suggest that Membranipora
may play an important role on Lacuna population dynamics.
Author to Contact: Suchana Chavanich
University of New Hampshire
Department of Zoology
Durham, NH 03824
T 603-862-1114
F 603-862-3784
Email: suchana@hopper.unh.edu
Key Words: Biological Invasions, Ballast Water, San Francisco Bay
Over the past 20 years, a rapidly accumulating body of knowledge has demonstrated that invasions by non-native organisms threaten the aquatic flora and fauna in the world's coastal regions and the human activities and economies that depend on them. Intensive research in the San Francisco Bay Estuary has provided data on striking alterations in biodiversity and ecosystem functioning. Over 230 exotic species, including protozoans, plants and animals, have become established in this estuary in salt-water and fresh-water habitats within the reach of the tides. Exotic organisms dominate several habitats, in which they account for 40% to 100% of the common species and sometimes over 90% of the number of individuals and total biomass. Furthermore, the rate of invasion has been dramatically increasing, from an average rate of less than one new species a year before 1960, to nearly four new species established each year since 1960. Other West Coast estuaries have been invaded to a lesser, though substantial, degree. Organisms introduced into one estuary may be rapidly spread to another by either natural mechanisms or human activities. For example the European green crab, Carcinus maenas, arrived in San Francisco Bay by 1990 and had spread to estuaries from Morro Bay, California to Grays Harbor, Washington--a range of around 900 miles--by 1998.
While estuaries, bays and harbors have been the most affected areas, exotic species may also threaten marine habitats on the open coast. A New Zealand sea slug (Philine auriformis, although there may be more than one species involved) that arrived in San Francisco Bay by 1992 has spread both to other central California bays where it has become very abundant, and to sandy bottom on the outer coast where it is sometimes now the most commonly collected sea slug all the way to southern California. A yet-unnamed South African sabellid worm that parasitizes abalone, and threatens many other types of marine snails in rocky habitats, has been released and continues to be released by abalone farmers, and may have become established in at least one site. These developments are particularly alarming because, until quite recently on the West Coast, waters of the open coast were virtually untouched by biological invasions.
Over the years, exotic organisms have been transported to the West Coast by a variety of activities. Probably the most important mechanism at present is the release of exotic organisms in discharges of ships' ballast water. The introduction and passage of the National Invasive Species Act in 1996 provided a golden opportunity to begin controlling ballast water discharges. Unfortunately, the law that resulted made it officially voluntary for ships to do anything about their ballast water throughout most of the United States. Thus, while it is a crime for ordinary citizens to release exotic species, ships are allowed to routinely dump enormous numbers of exotic organisms into the nation's waters, without monitoring or regulation.
In frustration, citizens have taken steps to regulate ballast water at the state and local level. In the last two years petitions and administrative actions to regulate ballast water discharges (which have prepared the way for litigation, should that prove necessary) have been initiated or supported by environmental groups, fisherman's associations, water districts and regulatory agencies in the West. Thus far these actions have been pursued under sections of the federal Clean Water Act, Endangered Species Act or National Environmental Policy Act, or under state water quality or environmental mitigation laws. State fish and game and coastal protection laws, and state and federal restrictions on the importation of harmful species may offer additional avenues for action. Increasingly, however, the developing consensus is that ballast water is fundamentally a water quality problemó a waste discharge of a biological pollutant that should be regulated through a discharge permit system just as chemical pollutants are.
Author to Contact: Andrew N. Cohen
San Francisco Estuary Institute
1325 South 46th Street
Richmond, CA 94804 USA
T (510) 231-9423
F (510) 231-9414
Email: acohen@sfei.org
If we respond to the problem of biological invasions by focusing on controlling exotic organisms after they have been introduced into the environment, rather than on preventing their arrival and release in the first place, then we will have committed ourselves to failure. For example, there are on average at least four new exotic species arriving and becoming established in the San Francisco Bay Estuary each year, with over 230 exotic species now established. Within this same region, despite considerable expense and effort, there are control efforts underway for only seven species, all of them aquatic or marsh plants. For only one of these has a substantial level of control been achieved, and even that is intermittent. In general, control efforts can be difficult and expensive, can impose collateral damage or risk to the environment, and often don't work. They sometimes also generate civic strife: efforts to control exotic fish in California and exotic cordgrasses in Washington have lead to lawsuits, public protests and even arrests. In any event, we cannot possibly design, fund and implement control efforts fast enough to deal with the flood of exotic species arriving in our coastal waters.
With any serious effort we ought to be able to reduce the rate of introduction substantially. Currently, ballast water discharges are entirely unregulated in most of the United States; the aquarium, pet, and ornamental plant trades can freely import virtually all types of aquatic animals and plants, except for a small list of prohibited species; and many state agencies that are generally thought to be responsible for protecting native wildlife are busy promoting the expansion of aquaculture and mariculture, often without adequate safeguards to prevent the importation and release of exotic pests, parasites and diseases of fish and shellfish. Substantial gains could be made (with far better benefit/cost ratios than any control effort) by implementing common sense measures to regulate the importation and release of exotic organisms by these activitiesó including some measures that have been advocated by biologists and resource managers for decades.
Author to Contact: Andrew N. Cohen
San Francisco Estuary Institute
1325 South 46th Street
Richmond, CA 94804 USA
T (510) 231-9423
F (510) 231-9414
Email: acohen@sfei.org
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