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Key Words: biological control, marine pests, safety
We now have a broad scientific consensus that introduced marine species sometimes become serious environmental pests, and that actions to reduce their transport, entry, and establishment are very necessary. After their establishment at a point of entry, we presently have neither practical tools to prevent their further spread, nor to significantly reduce their impact on native organisms. Recently, the use of natural enemies, as developed for the classical biological control of introduced weeds and agricultural insect pests, has been proposed to significantly reduce the impact of those established marine pests that have the potential to cause great economic and ecological damage. The key issues concerning such an approach are clearly its efficacy and safety. Many marine biologists see this as a fruitful avenue for investigation. The cost of inaction is considered great enough to assume some risk towards its resolution. Others, however, fear that this approach has the potential to cause more harm than benefit. They raise two general arguments. Potential natural enemies are seen as a coming plague. Reference points include cane toads, rabbit calicivirus and some predatory land snails. For some, the irreversible nature of a biocontrol agent argues against even its further investigation. Somewhat paradoxically, the other argument is that a biocontrol agent will not be effective because the pest is common where it is native. Thus, the natural enemy cannot effectively reduce its density where the pest has been introduced.
Analyses from the studies of the efficacy and safety of weed and insect pest biological control will be applied to its potential use against introduced marine pests. The campaign against the endemic coconut moth of Fiji will be examined as an exemplar of the scientific, cultural and economic values that may lead to conflict in the application of a biological control program for a pest.
Author to Contact: Armand Kuris
Key Words: Hemigrapsus sanguineus, crustacean, distribution, ecology, rocky intertidal, feeding rates
The Asian shore crab Hemigrapsus sanguineus was introduced to the mid-Atlantic coast in the late 1980ís. We have been studying population density and distribution on a cobble/boulder beach in central Long Island Sound. We have also done preliminary experiments on feeding activity. Average seasonal abundance on the cobble shore at Crane Neck Point during 1997-1998 ranged from 7-9 m-2. During the summer, the crabs were fairly evenly distributed at different elevations in the intertidal zone; however, they appeared to move from high to low elevation during the winter. The crabs readily consumed all common species of macroalgae and invertebrates occurring at Crane Neck Point. Based on laboratory experiments, we estimate that approximately 49-162 juvenile (<10mm) Littorina littorea and 28-171 small (<20mm) Mytillus galloprovincalias could be consumed daily per m2. Reduced foraging efficiency in the field where more cover is available for prey items, may result in actual predation rates that are considerably lower than these estimates. However, based on high crab densities and feeding rates on the early stages of these keystone species, we predict that this recent invader will strongly impact the community structure of the rocky intertidal in the western north Atlantic. Ironically, much of the impact may occur through predation on Littorina, a previously introduced species which itself has had a major impact on these communities.
Author to contact: Amy Larson
Key Words: Baltic Sea, Black Sea, introduced species, macrobenthos
Fauna and flora of the worldís two largest brackish water bodies, the Baltic and Black Seas, have been changed during the recent centuries. Until now, more than 100 of known or thought to be non-native species have been included in a Baltic and Black Sea Alien Species Database created by the Baltic Marine Biologistsí expert group (http://www.ku.lt/nemo/mainnemo.htm). We define this "foreign" biological diversity as xenodiversity in order to indicate the diversity caused by non-native species both at species and functional groups/life forms levels.
Out of the 52 unintentional introductions into the Baltic Sea with more or less known dispersal history, 32 are transoceanic; among them there are 15 trans-Atlantic ones of American origin. Typically the Atlantic coast of North America has exported more marine species to Europe than the other donor areas. This successfulness might be related more to the successive opening of routes of commerce in the post-Columbian and post-Cookian era than to the competitive vigor of the invaders from America. Once established, the most successful non-native, invasive species have spread rapidly, among them some Neo-Europeans of American origin. The soft-shell clam, Mya arenaria, is thought to be transported by the Vikings in the 13th century, the barnacle Balanus improvisus appeared in the late 1800's, and the polychaete, Marenzelleria viridis, in the 1990's.
The recent deterioration history of the Black Sea ecosystem offers a dramatic example of an ecological catastrophe caused by alien species. Within ten years (since 1982), a decrease of anchovy catch took place simultaneously with the expansion of the American comb jelly, Mnemiopsis leidyi.
The European history of non-native aquatic species can be divided in three eras: 1) early accidental introductions; 2) period of experimenting with economically beneficial species; 3) modern time introductions, with intentional ones more or less banned, but unintentional increasing, mainly due to ballast travelers. The role of non-native species in ecosystem functions and their ability to displace native species in the Baltic Sea is still badly understood. Especially in coastal inlets and lagoons, they tend to markedly alter the habitats they invaded or were introduced to. They increase the 3-dimensionality of the benthic habitats, broaden the food base of bottom and plankton eating fish, link benthic and pelagic subsystems, and create new microhabitas for associated fauna.
Author to Contact: Erkki Leppäkoski
Key Words: Hemigrapsus sanguineus, crabs, niche theory, framework, prediction
One of the primary questions at the heart of invasion
ecology is why some exotic organisms can succeed in "fitting" into
communities with which they have no shared evolutionary history
while resident community members fail to evade those same exotic
organisms. Ecological niche theory, specifically the theory of limiting
similarity, provides an excellent framework for addressing this
question. Patterns among successfully invasive organisms (e.g.,
life history characteristics; trophic position) or among the ecological
communities they invade (e.g., community diversity/richness; level
of habitat disturbance) have been difficult for invasion ecologists
to fully elucidate. Presented here are theoretical models of invasion,
based on niche theory, that provide a predictive context for research
on new invasions. Further, we provide a case study applying this
framework to the recently introduced Western Pacific shore crab,
Hemigrapsus sanguineus, using field data collected from its
native (Japan) and invaded (southern New England) range. A systematic
examination of other species introductions using this framework
should clarify the most common patterns, thereby enabling better
predictions of potential ecological and economic impacts of alien
Key Words: feeding mode, prey selection, whelk
A novel function may provide an invasive species with advantages relative to natives. In particular, invasive predators might have an advantage if they introduce a novel functional feeding mode to native prey. Models of coevolution can both support and refute this assertion. A lack of coevolution may provide invasive predators with an advantage, because native prey have ineffective or inappropriate anti-predatory defenses. Conversely, invasive predators may be outcompeted by native predators for native prey. The recent expansion of Kellet's whelk, Kelletia kelletii, from south of Point Conception northwards to Monterey Bay, California introduced a novel feeding mode to the guild of invertebrate predators preying on trochid snails in central California. Before the appearance of Kelletia in 1980, sea stars (an ecological equivalent of whelks) were the primary invertebrate predators of trochids in central California. Stars feed using an eversible stomach while Kelletia feeds with a prehensile proboscis.
I used native and non-native sea stars and whelks as predators and allopatric Tegula spp. as prey in a series of non-choice and choice experiments to: 1) compare consumption rates between different functional feeding modes; and 2) assess prey anti-predatory defenses within the genus Tegula. I used the southern rainbow star, Astrometis sertulifera, which feeds on trochids but occurs only in southern California to represent a non-coevolved predator in central California, and the giant spined star, Pisaster giganteus, which occurs in both southern and central California to represent a coevolved predator. Three subtidal macroherbivores in the genus Tegula were used as prey, one from central California (T. brunnea) and two from southern California (T. aureotincta, T. eiseni). In a non-choice experiment, I compared T. brunnea and T. aureotincta, both of which are poorly defended relative to sympatric congeners. Consumption rates were always highest for T. aureotincta. In a second non-choice experiment, I compared T. eiseni, which is well-defended, to T. brunnea. Astrometis consumed both prey species at equal rates, while both Pisaster and Kelletia ate significantly more T. brunnea than T. eiseni. Deep withdrawal by T. brunnea was a partially effective defense against sea stars, but it was less effective against the novel feeding mode of Kelletia. Escape frequency and consumption time were greater for T. eiseni. Among predators, Kelletia ate a significantly higher proportion of T. brunnea than either Pisaster or Astrometis. In a binary choice experiment using only southern California prey, all predators consumed T. aureotincta almost exclusively. Combining these results, T. aureotincta was most preferred, followed by T. brunnea, and T. eiseni was consumed when other prey were unavailable. The high performance of the whelk relative to the native and non-native sea stars indicates that its novel functional feeding mode is advantageous.
For Pisaster and Kelletia, performance was not influenced by geographic origin; individuals from populations separated by 500 km consumed prey at nearly identical rates. This similarity between widely separated populations does not fit models of coevolution that predict local adaptation and thus differences between populations. Predator performance was enhanced by novelty of function, and not by novelty as a species.
Author to Contact: Steve I. Lonhart
Key Words: Rapana venosa, gastropod, Chesapeake
Bay, larvae, salinity tolerance, range
The Veined Rapa Whelk, Rapana venosa, has
recently been identified as present in the Hampton Roads region
of the Chesapeake Bay. The species is native to the Sea of Japan,
but was introduced to the Black Sea in the 1940ís, and has since
spread to the Aegean and Adriatic Seas. There is strong evidence
that range extension is mediated by transport of early life history
stages in ballast water. The current status of knowledge of distribution
of R. venosa in the Chesapeake Bay is described. There is
concern over the potential impact of Rapana venosa on local
shellfish populations and the industry that they support. Egg cases
of R. venosa have been collected from the field, and larval
forms cultured in the laboratory. Estimates of the salinity tolerance
of the larval stages of Rapana venosa are described as a
precursor to estimating a potential range of distribution of the
species within the Chesapeake Bay and its subestuaries. Such estimates
are crucial to establishing which shellfish resources are potentially
susceptible to predation by local Rapana venosa populations.
Zebra mussels are a vigorous mollusk thought to originate in the Black Sea. Given a foothold the zebra mussels will colonize the area, killing off native species, and populate structures and pipes which can reduce water flow in critical cooling and irrigation operations tounsatisfactory levels.
The literature suggests that pulse power can be an effective and potentially economic method as a primary or as a complement to a mix of chemical and/or mechanical prevention/control technologies currently in use. The pulsed power method stuns or kills the veligers in the pipe entrance and has no effect on animals upstream of the entrance, nor downstream from the system discharge.
An experimental 20Kv pulse will be described which has been used to suppress zebra mussel settlement by more than 80% in a power plant cooled by Mississippi River water. Methods for improving the effectiveness and cost will be described. Finally, application of this technique to control other marine species will be touched upon.
Key Words: molecular genetics, ballast water, origins of invasive species
Knowledge of the geographic origin of an invasive species can contribute to the identification of the vector responsible for its introduction. Although it is often difficult to determine the origin of introduced species, the use of molecular genetics can help to identify possible sources. In 1996, a large red alga, Grateloupia doryphora, was recorded for the first time in Narragansett Bay, RI. Since its arrival, it has continued to spread and will likely have an effect on native biota. In an effort to identify the geographic origin and vector, we have obtained G. doryphora individuals from locations around the world. Genetic analyses of these individuals (using ITS sequences and RAPDs) suggest that this introduction is not due to marginal dispersal. Based on the pattern of ship traffic in Narragansett Bay and the locations of the first G. doryphora populations, it seems likely that either hulls of ships or ballast water-dumping were involved in the introduction, and our genetic data provide further evidence for this mode of introduction.
Author to Contact: Marcia Marston
Key Words: Ballast water, treatment, management, disinfection, filtration, biocides, pilot scale studies, dinoflagellate
The environmental damages caused by transfer of unwanted organisms in ballast water are well understood and research efforts are needed for treatment and control. The Environmental Technology Institute (ETI), Singapore in collaboration with The Maritime Port Authority (MPA) and National University of Singapore (NUS) has initiated a multi-faced research and development project on ballast water including a pilot scale evaluation of possible ship-board treatment system to remove unwanted micro-organisms. The first phase of this project consists of a 250 gpm pilot plant, incorporating innovative self-cleaning strainers and multimedia pressure filtration systems. Inactivation studies of surrogate microorganisms using biocides have been initiated in parallel laboratory scale experiments. These studies are complemented with the development of a reliable bio-monitoring technique to determine the biocide (C · t) relationships using dinoflagellate cysts as indicator organisms. This paper discusses the status of this on-going research and preliminary findings.
Author to Contact: Dr. Jose T Matheickal
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