Assessment and Management of Risks from Biofouling

<p>Vessel biofouling is a well recognised modern-day pathway for the transfer of nonindigenous species (NIS). However despite awareness of these risks, marine incursions as a result of vessel biofouling continue to occur at a growing rate. The objective of this thesis is to provide underpinning knowledge to improve pre- and post-border management strategies for vessel biofouling. Chapter 2 provides a baseline assessment of the biofouling extent and assemblage composition on slow-moving vessels arriving at New Zealand's border. Slow-movers were targeted because their operational profile is widely considered to favour the accumulation of extensive biofouling communities (i.e., potentially high risk vectors of NIS). Interestingly, this research revealed low fouling levels and a low incidence of NIS. Highest levels of fouling were observed in areas where antifouling paint condition was poor or absent (e.g., dry-docking support strips and niche areas), which is consistent with recent studies of biofouling on other vessel types. Despite these findings, there have been several documented examples where heavily fouled slow movers have had high risk NIS on them. As such, risk profiling of slow-moving vessels is recommended. This should be based on operational characteristics such as maintenance history, exposure to regions where pest species are known to be present and intended vessel movements in the recipient region, and should ideally be undertaken on a case-by-case basis prior to arrival from international or distant source-regions. There are limited biofouling risk mitigation options available upon the discovery of NIS at the border, particularly for large vessels (e.g., barges) or towed structures (e.g., oil rigs) where removal to land is often not feasible and in-water defouling may be the only option available. Chapter 3 provides a conceptual framework that identifies biosecurity benefits and risks posed by in-water defouling. Among the latter are the survivorship of defouled material, the release of viable propagules via spawning, and enhanced colonisation of recently defouled surfaces by high risk NIS. Chapter 4 then assesses the operational performance of two diver-operated defouling tools (rotating brush devices) that were designed to retain defouled material during operation (i.e., mitigating one of the main risks associated with in-water defouling identified in Chapter 3). These devices proved effective in removing low-to-moderate levels of fouling from flat and curved experimental surfaces. However, performance was generally poorer at removing more advanced levels of fouling. Furthermore, neither system was capable of retaining all material defouled; c. 4% was lost to the environment, of which around 20% was viable. A significant component of material lost comprised fragmented colonial organisms (e.g., the ascidian Diplosoma sp.), which are theoretically capable of forming new colonies from fragments. The study also concluded that the defouling brush devices were not suitable for treating niche areas of vessel hulls such as gratings and water cooling intakes, areas where earlier work in Chapter 2 identified fouling levels to be the greatest. Observations of fully intact and seemingly viable fragments being lost to the environment during in-water defouling trials led to a series of laboratory- and fieldbased experiments designed to elucidate factors influencing the survivorship of defouled material on the seabed (Chapter 5). This work showed that for some colonial organisms (e.g., ascidians), the size of fragments generated during removal affected reattachment success. Thus the defouling method is an important consideration for vessels fouled by colonial NIS. Manipulative field experiments demonstrated that exposure to sediments and benthic predation can play a major role in post-defouling survivorship. Sedimentinduced morality and susceptibility to predation was also taxon-specific. For example, soft-bodied organisms (e.g., sponges, colonial ascidians) were more affected by sedimentation and predation than calcareous taxa (e.g., tubeworms). Chapter 6 provides a "real world" example of in-water defouling. In December 2007, the defouling of an oil rig over soft-sediments in Tasman Bay, and the subsequent discovery of NIS amongst the defouled material on the seabed, led to a dredge-based incursion response whose goal was eradication of the NIS, in particular the brown mussel Perna perna. During the response, c. 35 tonnes of defouled material was removed from the seabed, and target pests were reduced to densities considered too low for successful reproduction (and therefore establishment in the region) to occur. This chapter evaluates the efficacy of the response method and demonstrates that where complete elimination of a pest (i.e., removal of all organisms) is not feasible, alternative eradication success criteria based on density thresholds can be developed to mitigate biosecurity risks posed by an incursion. The preceding technical chapters highlight the risks posed by biofouling and identify that there are presently limited post-border risk mitigation tools available. This reinforces the widely held belief that more effort should be put into pre-border management. In Chapter 7, I use two case studies of oil rig biofouling to highlight the many challenges associated with pre-border management, and identify the urgent need for the development of treatment tools and strategies to mitigate biosecurity risks posed by vessels and structures where removal to land (e.g., dry-docking) is not feasible.</p>

Assessment and Management of Risks from Biofouling

<p>Vessel biofouling is a well recognised modern-day pathway for the transfer of nonindigenous species (NIS). However despite awareness of these risks, marine incursions as a result of vessel biofouling continue to occur at a growing rate. The objective of this thesis is to provide underpinning knowledge to improve pre- and post-border management strategies for vessel biofouling. Chapter 2 provides a baseline assessment of the biofouling extent and assemblage composition on slow-moving vessels arriving at New Zealand's border. Slow-movers were targeted because their operational profile is widely considered to favour the accumulation of extensive biofouling communities (i.e., potentially high risk vectors of NIS). Interestingly, this research revealed low fouling levels and a low incidence of NIS. Highest levels of fouling were observed in areas where antifouling paint condition was poor or absent (e.g., dry-docking support strips and niche areas), which is consistent with recent studies of biofouling on other vessel types. Despite these findings, there have been several documented examples where heavily fouled slow movers have had high risk NIS on them. As such, risk profiling of slow-moving vessels is recommended. This should be based on operational characteristics such as maintenance history, exposure to regions where pest species are known to be present and intended vessel movements in the recipient region, and should ideally be undertaken on a case-by-case basis prior to arrival from international or distant source-regions. There are limited biofouling risk mitigation options available upon the discovery of NIS at the border, particularly for large vessels (e.g., barges) or towed structures (e.g., oil rigs) where removal to land is often not feasible and in-water defouling may be the only option available. Chapter 3 provides a conceptual framework that identifies biosecurity benefits and risks posed by in-water defouling. Among the latter are the survivorship of defouled material, the release of viable propagules via spawning, and enhanced colonisation of recently defouled surfaces by high risk NIS. Chapter 4 then assesses the operational performance of two diver-operated defouling tools (rotating brush devices) that were designed to retain defouled material during operation (i.e., mitigating one of the main risks associated with in-water defouling identified in Chapter 3). These devices proved effective in removing low-to-moderate levels of fouling from flat and curved experimental surfaces. However, performance was generally poorer at removing more advanced levels of fouling. Furthermore, neither system was capable of retaining all material defouled; c. 4% was lost to the environment, of which around 20% was viable. A significant component of material lost comprised fragmented colonial organisms (e.g., the ascidian Diplosoma sp.), which are theoretically capable of forming new colonies from fragments. The study also concluded that the defouling brush devices were not suitable for treating niche areas of vessel hulls such as gratings and water cooling intakes, areas where earlier work in Chapter 2 identified fouling levels to be the greatest. Observations of fully intact and seemingly viable fragments being lost to the environment during in-water defouling trials led to a series of laboratory- and fieldbased experiments designed to elucidate factors influencing the survivorship of defouled material on the seabed (Chapter 5). This work showed that for some colonial organisms (e.g., ascidians), the size of fragments generated during removal affected reattachment success. Thus the defouling method is an important consideration for vessels fouled by colonial NIS. Manipulative field experiments demonstrated that exposure to sediments and benthic predation can play a major role in post-defouling survivorship. Sedimentinduced morality and susceptibility to predation was also taxon-specific. For example, soft-bodied organisms (e.g., sponges, colonial ascidians) were more affected by sedimentation and predation than calcareous taxa (e.g., tubeworms). Chapter 6 provides a "real world" example of in-water defouling. In December 2007, the defouling of an oil rig over soft-sediments in Tasman Bay, and the subsequent discovery of NIS amongst the defouled material on the seabed, led to a dredge-based incursion response whose goal was eradication of the NIS, in particular the brown mussel Perna perna. During the response, c. 35 tonnes of defouled material was removed from the seabed, and target pests were reduced to densities considered too low for successful reproduction (and therefore establishment in the region) to occur. This chapter evaluates the efficacy of the response method and demonstrates that where complete elimination of a pest (i.e., removal of all organisms) is not feasible, alternative eradication success criteria based on density thresholds can be developed to mitigate biosecurity risks posed by an incursion. The preceding technical chapters highlight the risks posed by biofouling and identify that there are presently limited post-border risk mitigation tools available. This reinforces the widely held belief that more effort should be put into pre-border management. In Chapter 7, I use two case studies of oil rig biofouling to highlight the many challenges associated with pre-border management, and identify the urgent need for the development of treatment tools and strategies to mitigate biosecurity risks posed by vessels and structures where removal to land (e.g., dry-docking) is not feasible.</p>

Organism motility in an oxygenated shallow-marine environment 2.1 billion years ago

Evidence for macroscopic life in the Paleoproterozoic Era comes from 1.8 billion-year-old (Ga) compression fossils [Han TM, Runnegar B (1992) Science 257:232–235; Knoll et al. (2006) Philos Trans R Soc Lond B 361:1023–1038], Stirling biota [Bengtson S et al. (2007) Paleobiology 33:351–381], and large colonial organisms exhibiting signs of coordinated growth from the 2.1-Ga Francevillian series, Gabon. Here we report on pyritized string-shaped structures from the Francevillian Basin. Combined microscopic, microtomographic, geochemical, and sedimentologic analyses provide evidence for biogenicity, and syngenicity and suggest that the structures underwent fossilization during early diagenesis close to the sediment–water interface. The string-shaped structures are up to 6 mm across and extend up to 170 mm through the strata. Morphological and 3D tomographic reconstructions suggest that the producer may have been a multicellular or syncytial organism able to migrate laterally and vertically to reach food resources. A possible modern analog is the aggregation of amoeboid cells into a migratory slug phase in cellular slime molds at times of starvation. This unique ecologic window established in an oxygenated, shallow-marine environment represents an exceptional record of the biosphere following the crucial changes that occurred in the atmosphere and ocean in the aftermath of the great oxidation event (GOE).

Full allogeneic fusion of embryos in a holothuroid echinoderm

Whole-body chimaeras (organisms composed of genetically distinct cells) have been directly observed in modular/colonial organisms (e.g. corals, sponges, ascidians); whereas in unitary deuterostosmes (including mammals) they have only been detected indirectly through molecular analysis. Here, we document for the first time the step-by-step development of whole-body chimaeras in the holothuroid Cucumaria frondosa , a unitary deuterostome belonging to the phylum Echinodermata. To the best of our knowledge, this is the most derived unitary metazoan in which direct investigation of zygote fusibility has been undertaken. Fusion occurred among hatched blastulae, never during earlier (unhatched) or later (larval) stages. The fully fused chimaeric propagules were two to five times larger than non-chimaeric embryos. Fusion was positively correlated with propagule density and facilitated by the natural tendency of early embryos to agglomerate. The discovery of natural chimaerism in a unitary deuterostome that possesses large externally fertilized eggs provides a framework to explore key aspects of evolutionary biology, histocompatibility and cell transplantation in biomedical research.

Kleptopredation: a mechanism to facilitate planktivory in a benthic mollusc

Predation occurs when an organism completely or partially consumes its prey. Partial consumption is typical of herbivores but is also common in some marine microbenthic carnivores that feed on colonial organisms. Associations between nudibranch molluscs and colonial hydroids have long been assumed to be simple predator–prey relationships. Here we show that while the aeolid nudibranch Cratena peregrina does prey directly on the hydranths of Eudendrium racemosum , it is stimulated to feed when hydranths have captured and are handling prey, thus ingesting recently captured plankton along with the hydroid polyp such that plankton form at least half of the nudibranch diet. The nudibranch is thus largely planktivorous, facilitated by use of the hydroid for prey capture. At the scale of the colony this combines predation with kleptoparasitism, a type of competition that involves the theft of already-procured items to form a feeding mode that does not fit into existing classifications, which we term kleptopredation. This strategy of subsidized predation helps explain how obligate-feeding nudibranchs obtain sufficient energy for reproduction from an ephemeral food source.

Allometric growth in reef-building corals

Predicting demographic rates is a critical part of forecasting the future of ecosystems under global change. Here, we test if growth rates can be predicted from morphological traits for a highly diverse group of colonial symbiotic organisms: scleractinian corals. We ask whether growth is isometric or allometric among corals, and whether most variation in coral growth rates occurs at the level of the species or morphological group. We estimate growth as change in planar area for 11 species, across five morphological groups and over 5 years. We show that coral growth rates are best predicted from colony size and morphology rather than species. Coral size follows a power scaling law with a constant exponent of 0.91. Despite being colonial organisms, corals have consistent allometric scaling in growth. This consistency simplifies the task of projecting community responses to disturbance and climate change.

Politics for the Polyps

Daniel Harris, “Politics for the Polyps: The Compound Organism as a ‘Peculiar Form of Communism’ in Charles Kingsley’s Alton Locke and The Water-Babies” (pp. 64–88) Charles Kingsley’s novels and political writings are saturated with references to physiological processes in marine invertebrates. In particular, the forms of his novels take their inspiration from functional arrangements in colonial organisms such as corals, in which “individual” polyps are physiologically linked to their neighbors. Alton Locke (1851) and The Water-Babies (1863) attempt to explain the benefits of cooperative economic practices (e.g., the associative workshop) and the dangers of cooperative political practices (e.g., the Chartist mass meeting) by jettisoning British Enlightenment assumptions about personal identity. Instead, Kingsley’s novels use discontinuous and communal physiological processes in invertebrates, such as corals and jellyfish, as frameworks for representing psychological and political development. Ultimately, Kingsley seeks to intervene in mid-century debates about how to individuate members of the working class by suggesting that reformist measures must be grounded in a physiological understanding of individuation that contravenes psychological definitions of individuality.