Chad L. Hewitt

Introduced Macroalgae – a Growing Concern

Introductions of non-indigenous species to new ecosystems are one of the major threats to biodiversity, ecosystem functions and services. Globally, species introductions may lead to biotic homogenisation, in synergy with other anthropogenic disturbances such as climate change and coastal pollution. Successful marine introductions depend on (1) presence of a transport vector, uptake of propagules and journey survival of the species; (2) suitable environmental conditions in the receiving habitat; and (3) biological traits of the invader to facilitate establishment. Knowledge has improved of the distribution, biology and ecology of high profile seaweed invaders, e.g. Caulerpataxifolia, Codium fragile ssp. tomentosoides, Sargassummuticum, and Undariapinnatifida. Limited, regional information is available for less conspicuous species. The mechanisms of seaweed introductions are little understood as research on introduced seaweeds has been mostly reactive, following discoveries of introductions. Sources of introductions mostly cannot be determined with certainty apart from those directly associated with aquaculture activities and few studies have addressed the sometimes serious ecological and economic impacts of seaweed introductions. Future research needs to elucidate the invasion process, interactions between invaders, and impacts of introductions to support prevention and management of seaweed introductions.

Microcosms as Models for Generating and Testing Community Theory

Microcosms as biological models have played a central role in the development of contemporary ecological though. From Gause`s (1934) pioneering analysis of competitive exclusion to Huffaker`s (1958) explicit examination of a spatial resource and Tilman`s (1977,1982) elegant exploration of competitive mechanisms, laboratory analyses have provided essential insight into real-world ecology. Conversely, phenomena encountered in the field have been systematically examined in the laboratory, extending and refining our understanding of the dynamical range of both mechanism and process. Extension of these model-driven insights to the field has been integral in the development of important themes within the collective gestalt of academic ecology. This interchange between laboratory and field studies is typified by recent laboratory models of competition, predation, community, assembly, and landscape assembly. 74 refs., 3 figs.

Impacts of introduced seaweeds.

Abstract We analyzed 69 publications on the impacts of introduced seaweeds. The predominant impacts were changed competitive relationships in the recipient habitat, indicated by high abundances of invaders, resultant space monopolization, and reduced abundances/biomass of native macrophytes. Changes in biodiversity, effects on fish and invertebrate fauna, toxic effects on other biota, and habitat change were also identified. The mechanisms underlying the manifestation of impacts are uncertain and inferences about common patterns were hampered because impact studies were available for only a few introduced seaweeds, covered only a fraction of their introduced distribution and generally were conducted over short time scales. There was no information about evolutionary effects or changes of ecosystem processes. Knowledge of socio-economic impacts of invasive seaweeds is poor. We collated costs associated with control/eradication activities and for national spending on marine biosecurity in Australia, New Zealand and the United States. Prevention of impacts is the driving force for costly surveillance, eradication and control programs. Until we are able to understand, predict and measure impacts of introduced seaweeds, the management of species incursions needs to remain focused on early detection, rapid response and control to reduce the likelihood of negative impact effects.

Marine introductions in the Southern Ocean: an unrecognised hazard to biodiversity

This study investigated the potential for transport of organisms between Hobart, Macquarie Island and the Antarctic continent by ships used in support of Antarctic science and tourism. Northward transport of plankton in ballast water is more likely than southward transport because ballast is normally loaded in the Antarctic and unloaded at the home port. Culturing of ballast water samples revealed that high-latitude hitchhikers were able to reach greater diversities when cultured at temperate thermal conditions than at typical Southern Ocean temperatures, suggesting the potential for establishment in the Tasmanian coastal environment. Several known invasive species were identified among fouling communities on the hulls of vessels that travel between Hobart and the Southern Ocean. Southward transport of hull fouling species is more likely than northward transport due to the accumulation of assemblages during the winter period spent in the home port of Hobart. This study does not prove that non-indigenous marine species have, or will be, transported and established as a consequence of Antarctic shipping but illustrates that the potential exists. Awareness of the potential risk and simple changes to operating procedures may reduce the chance of introductions in the future.

Ships' sea-chests: an overlooked transfer mechanism for non-indigenous marine species?

Historically, hull fouling associated with slow-moving, wooden-hulled vessels has been recognized as the primary transport mechanism responsible for the dispersal of non-indigenous marine species (NIMS) around the world and the fouling of hulls may have contributed significantly to the current patterns of bi-ogeographic distributions of many marine organisms (e.g., Carlton and Hodder, 1995). Over the past three decades however, ballast water has been identified as the primary causal mechanism and has been the focus of international concern (e. suggest that the attachment of organisms on the hulls of vessels remains a significant vector in modern times, possibly equal to ballast water, although further conclusive evidence is required. Currently , there is no concerted effort to evaluate the relative importance of these disparate mechanisms in the transfer of NIMS to new locations. The discussion of transfer mechanisms has identified that numerous locations within and on a vessel may afford distinct environments (e. discussed sea-chests (sea inlet boxes, or suction bays) as environments linked with hull fouling assemblages. Similarly, Gollasch (2002) has discussed the role of sea-chests in the transport of fouling organisms. Sea-chests provide a unique part of the vessel for the transport of marine organisms, dissimilar to ballast water and the exposed surface of the hull. Sea-chests are recesses built into a ships hull located beneath the waterline on the side and/or on the bottom near the engine room. They are designed to reduce water cavitation, and thus increase pumping efficiency when seawater is pumped aboard the vessel for engine cooling, ballast, and fire fighting purposes. The size, number and dimensions of sea-chests vary considerably with vessel size and type. As a general rule, the larger the vessel, thus increasing demand for ballast water, the greater the size and number of sea-chests. Sea-chests are protected by metal grates, which have holes (15–25 mm in diameter) or slots (20–35 mm width) to prevent foreign matter entering and damaging the ships pumps. These grates are held in place by a number of bolts, and therefore sea-chests are usually only accessible during dry-docking. In order to ascertain the extent to which sea-chests provide a unique habitat and contribute to the transport of NIMS, we undertook a preliminary investigation of the passenger ferry Spirit of Tasmania, which operates in southeastern Australia. The hull of the Spirit of Tasmania was surveyed for fouling at the Australian Defence Industries Limited dry-dock at Garden Island, Sydney, on …

‘Double trouble’: the expansion of the Suez Canal and marine bioinvasions in the Mediterranean Sea

‘‘Egypt to build new Suez canal... ‘This giant project will be the creation of a new Suez canal parallel to the current channel’ said Mohab Mamish, the chairman of the Suez Canal Authority, in a televised speech.’’ (http://www.theguardian.com/world/2014/aug/05/ egypt-build-new-suez-canal, viewed August 13, 2014). This is ominous news. Expected to double the capacity of the Suez Canal, the expansion is sure to have a diverse range of effects, at local and regional scales, on both the biological diversity and the ecosystem goods and services of the Mediterranean Sea. Of nearly 700 multicellular non-indigenous species (NIS) currently recognized from the Mediterranean Sea, fully half were introduced through the Suez Canal since 1869 (Galil et al. 2014). This is one of the most potent mechanisms and corridors for invasions by marine species known in the world. Further, molecular methods demonstrate high levels of gene flow between the Red Sea and the Mediterranean populations

New Zealand marine biosecurity: delivering outcomes in a fluid environment

Abstract Marine biosecurity, the protection of the marine environment from impacts of non‐indigenous species, has a high profile in New Zealand largely associated with a dependence on shipping. The Ministry of Fisheries is the lead agency for marine biosecurity and is tasked with managing the risks posed by pests and non‐indigenous marine species. Much like the terrestrial environment, multiple pathways provide ample opportunities for new species to arrive. The Marine Biosecurity Team was established in 1998, and under the Biodiversity package delivered by government, has undertaken an ambitious programme to deliver biosecurity outcomes by reducing the knowledge gaps and establishing management frameworks. A Risk Management Framework aids decision‐making and operational planning. Despite significant progress, a number of gaps have been identified in our knowledge base, capability, and capacity that require attention.

Efficacy of physical removal of a marine pest: the introduced kelp Undaria pinnatifida in a Tasmanian Marine Reserve.

The tools available for incursion response in the marine environment are limited, both in number and in situations where they can be appropriately applied. The ability to make decisions as to when and where a response should occur is limited by knowledge of the efficacy and costs. We undertook an evaluation of manual removal of Undaria pinnatifida sporophytes in a new incursion in the Tinderbox Marine Reserve in Tasmania over a 2.5 year study period. Plants were removed, from a 800 m2 area, on a monthly basis to minimise the likelihood of maturation of sporophytes and subsequent release of zoospores. While manual removal appears to have significantly reduced the number of developing sporophytes, the persistence of ‘hot spots’ through time suggests that either microscopic stages (zoospores, gametophytes or sporelings) create a ‘seed bank’ that persists for longer than 2.5 years or selective gametophyte survival in microhabitats occurs. In order for manual removal of Undaria to be effective a long-term commitment to a removal activity needs to be coupled with vector management and education initiatives to reduce the chances of re-inoculation and spread, with monitoring (and response) on a larger spatial scale for the early detection of other incursion sites, and with a treatment to remove persistent microscopic stages.

The Vessel as a Vector – Biofouling, Ballast Water and Sediments

Human-mediated marine bioinvasions have altered the way we view the marine environment – virtually all regions of the global oceans have experienced the introduction of marine species (e.g., Carlton 1979; Coles et al. 1999; Cranfield et al. 1998; Cohen and Carlton 1998; Hewitt et al. 1999, 2004; Orensanz et al. 2002; Leppakoski et al. 2002; Lewis et al. 2003; Castilla et al. 2005; Wolff 2005; Gollasch and Nehring 2006; Minchin 2006), placing marine and coastal resources under increased threat. Humans have almost certainly transported marine species since early attempts to voyage by sea. These ancient transport vectors were slow, and for the most part restricted to small spatial scales. The beginning of significant exploration and subsequent expansion by Europeans (post 1500 AD) has resulted in the transport of many thousands of species across all world oceans (Crosby 1986; diCastri 1989; Carlton 2001). The transport of species by human vectors was recognized by early workers (Ostenfeld 1908; Elton 1958), but it is only in the last few decades that significant progress on identifying patterns and processes has been made (e.g., Carlton 1985, 1996, 2001; Ruiz et al. 2000; Hewitt et al. 2004; Castilla et al. 2005; Minchin 2006). Numerous transport vectors have been identified and described (Carlton 2001; Chap. 5, Minchin et al.); however the majority of species appear to have been associated with vessel movements, either as exploratory, military, commercial or recreational vessels (e.g., Carlton 1985, 2001; Cohen and Carlton 1998; Hewitt et al. 1999; Gollasch et al. 2002, Minchin and Gollasch 2003). The ship as a transport vector is comprised of several sub-vectors. These include (1) the hull and other ‘niche’ areas, such as the propeller, rudder, on exposed surfaces of water piping, seachests, and thruster tunnels, where accumulations of growths of organisms develop (typically known as hull fouling), (2) the boring of organisms into the structure of the vessel (primarily limited to wooden hulled vessels), and (3) the uptake of organisms in association with wet or dry ballast (Carlton 1985, 1996; Ruiz et al. 2000). Several of these ship sub-vectors are no longer active. Hull boring for example, virtually ceased to exist with the use of steel G. Rilov, J.A. Crooks (eds.) Biological Invasions in Marine Ecosystems. 117 Ecological Studies 204, © Springer-Verlag Berlin Heidelberg 2009 118 C.L. Hewitt et al. as the primary ship-building material in merchant and naval vessels. However, many pleasure boats and fishing craft are still constructed of wood (Nagabhushanam and Sarojini 1997). Similarly, dry-ballast made up of sand, gravel and rock taken from littoral environments was replaced with water as ballast beginning in the late 1800s and had become phased out by 1950. None of these sub-vectors is species-specific, and each is likely to transport entire assemblages of species. Each may also facilitate the transport of a differing suite of species with different physiological and ecological characteristics (see Table 6.1). Biofouling primarily transports species that have attached sedentary or sessile, benthic habits, or species associated with these communities (e.g., living in, between or on other organisms) (Minchin and Gollasch 2003). In contrast, ballast water transports species associated with the plankton either as holo-plankton (species that have their whole life-cycle in the water column), mero-plankton (species with a portion of their life-cycle in the water column), or tycho-plankton (species accidentally swept into the water column), and often include pelagic species. It is difficult to establish a firm link between an already established introduced species and the vector (or sub-vector) by which it arrived in the new location (Minchin 2007). Nevertheless, attempts at assigning linkages to sub-vectors based on life history modes, timing of invasions, and association between location of incursion and subvectors have been deduced by reasoned argument (e.g., Hewitt et al. 1999, 2004, in press; Fofonoff et al. 2003; Ruiz et al. 2000).

Characterizing Vectors of Marine Invasion

The arrival of an invasive species in a new region is the culmination of a set of relatively discrete steps, including the invader’s initial association with a transport vector, its tolerance of environmental conditions encountered during transit, and its survival upon entering its new ecosystem (Ruiz and Carlton 2003). In the chapters that follow, a number of issues related to this process are presented. Chapter 6, Hewitt et al., discusses shipping, the most important of the marine invasion pathways. Chapter 7, Johnston et al., discusses the role of propagule pressure, how the quantity and quality of invader propagules determine invasion success. Chapter 8, Miller and Ruiz, follows with a framework for considering the distinct roles of source region, vector, and recipient region in assessing invasion success or failure within species pools. In addition, several vectors are discussed in relation to specific species and locales in the Geographic Perspectives section, which includes some assessments of temporal shifts in trading patterns (e.g. Chap. 24, Hayden et al.; Chap. 28, Fofonoff et al.). The importance of pathways, vectors, and modelling human activities is discussed in previous sections (Chap. 2, Carlton; Chap. 4, Wonham and Lewis).