Patrick Louis Cahill

Caulerpa seaweeds reproduce clonally via fragmentation, but sporadic sexual reproduction is also posited to be a common feature of their life cycles. Sexual reproduction of Caulerpa seaweeds is understudied, with evidence of gametogenesis reported for Caulerpa species and only one prior record from gametogenesis through to new juvenile plants (for Caulerpa racemosa ). In this study, laboratory experiments were conducted to observe and document the process of sexual reproduction in Caulerpa parvifolia and test the effect of light stress as an environmental trigger of gametogenesis. Sexual reproduction was observed via holocarpic production of male and female gametes from monoecious individuals. Gametes were released en masse from papillae and fused in the water column to form zygotes, which settled, expanded into spherical bodies, and elongated into primary germ tubes. By 35 days post spawning, these germ tubes had become juveniles comprising a stolon bearing fronds and rhizoids. Sexual reproduction was triggered by light levels that exceed the optima for C. parvifolia , supporting a hypothesis that stochastic environmental stressors may trigger gametogenesis. These findings add to the fundamental knowledge of reproduction in the genus Caulerpa and provide specific insights to help inform the management of invasive C. parvifolia populations.

Mimics of natural cationic antimicrobial peptides have demonstrated high antimicrobial activity, and their essential pharmacophore can be effectively incorporated into the cyclic 2,5-diketopiperazine scaffold. Control over bioactivity and selectivity can be achieved by altering the balance between charge and hydrophobicity and by employing a range of small electron-withdrawing and electron-donating substituents; compounds with good antibacterial potency (low μM) could be prepared. The lead compounds prepared in this study had comparable antimicrobial potency to the antibiotic positive controls and the antimicrobial peptide LTX-109, against both Gram-positive and Gram-negative bacteria and multidrug-resistant strains. The off-target toxicity against human red blood cells and VERO cells revealed a good cellular selectivity. Nontoxic and highly potent small compounds were thus prepared, which were comparable or superior to several short antimicrobial peptide mimics under clinical development. A clear link to N-substituent hydrophobicity was revealed, and hydrophobicity thresholds for both cellular selectivity and antimicrobial activity were identified.

Parasites can provide valuable insights into the ecology and health of their hosts and the state of the surrounding ecosystem. In this study, we describe the helminth parasite communities infecting penguin species in Otago, New Zealand (little blue penguin, Fiordland crested penguin, Snares crested penguin, erect crested penguin and yellow-eyed penguin). We investigate differences in parasite communities among penguin species, and changes over time for little blue penguins. In total, 19 parasite species representing 8 families (Desmidocercidae, Anisakidae, Acuariidae, Capillariidae, Tetrabothriidae, Heterophyidae, Renicolidae and Polymorphidae) were recorded from 121 penguin individuals. Parasite assemblages differed among penguin species, likely reflective of their differences in diet and feeding strategies. We also observed significant changes in the composition of parasite communities of little blue penguins using samples from a 30-year timespan (1993–2023). There was an overall increase in parasite diversity over time, including some species of potential disease concern, which could reflect a shift in prey availability of fish in the area. Our findings contribute to the understanding of penguin ecology and emphasise the use of parasites as indicators of ecological change.

ConspectusThe unwanted accumulation of marine micro- and macroorganisms such as algae and barnacles on submerged man-made structures and vessel hulls is a major challenge for any marine operation. Known as biofouling, this problem leads to reduced hydrodynamic efficiency, significantly increased fuel usage, microbially induced corrosion, and, if not managed appropriately, eventual loss of both performance and structural integrity. Ship hull biofouling in the international maritime transport network conservatively accounts for 0.6% of global carbon emissions, highlighting the global scale and the importance of this problem. Improved antifouling strategies to limit surface colonization are paramount for essential activities such as shipping, aquaculture, desalination, and the marine renewable energy sector, representing both a multibillion dollar cost and a substantial practical challenge. From an ecological perspective, biofouling is a primary contributor to the global spread of invasive marine species, which has extensive implications for the marine environment.Historically, heavy metal-based toxic biocides have been used to control biofouling. However, their unwanted collateral ecological damage on nontarget species and bioaccumulation has led to recent global bans. With expanding human activities within aquaculture and offshore energy, it is both urgent and apparent that environmentally friendly surface protection remains key for maintaining the function of both moving and stationary marine structures. Biofouling communities are typically a highly complex network of both micro- and macroorganisms, representing a broad section of life from bacteria to macrophytes and animals. Given this diversity, it is unrealistic to expect that a single antifouling "silver bullet" will prevent colonization with the exception of generally toxic biocides. For that reason, modern and future antifouling solutions are anticipated to rely on novel coating technologies and "combination therapies" where mixtures of narrow-spectrum bioactive components are used to provide coverage across fouling species. In contrast to the existing cohort of outdated, toxic antifouling strategies, such as copper- and tributyltin-releasing paints, modern drug discovery techniques are increasingly being employed for the rational design of effective yet safe alternatives. The challenge for a medicinal chemistry approach is to effectively account for the large taxonomic diversity among fouling organisms combined with a lack of well-defined conserved molecular targets within most taxa.The current Account summarizes our work employing the tools of modern medicinal chemistry to discover, modify, and develop optimized and scalable antifouling solutions based on naturally occurring antifouling and repelling compounds from both marine and terrestrial sources. Inspiration for rational design comes from targeted studies on allelopathic natural products, natural repelling peptides, and secondary metabolites from sessile marine organisms with clean exteriors, which has yielded several efficient and promising antifouling leads.

Anthropogenic vectors (transfer mechanisms) can facilitate the introduction and spread of aquatic disease in marine farming regions. Preventing or interrupting pathogen transfers associated with movements of these vectors is key to ensuring productivity and profitability of aquaculture operations. However, practical methods to identify and manage vector risks are lacking. We developed a risk analysis framework to identify disease risks and management gaps associated with anthropogenic vector movements in New Zealand’s main aquaculture sectors - Chinook salmon (Oncorhynchus tshawytscha), green-lipped mussels (Perna canaliculus), and Pacific oysters (Crassostrea gigas). Vectors within each sector were identified and assigned categorical risk scores for (i) movement characteristics (size, frequency, likelihood of return to sea), (ii) biological association with pathogens (entrainment potential, contribution to previous aquaculture disease outbreaks) and (iii) available best practice biosecurity methods and tools, to inform unmitigated and mitigated risk rankings. Thirty-one vectors were identified to operate within the national network and association with livestock was found to be a primary driver of vector risk rankings. Movements of live growing stock and culture substrates (e.g., mussel ropes) in shellfish farming had high-risk vector profiles that are logistically challenging to address, while vessel vectors were identified as the salmon farming sector’s priority. The framework and rankings can be used to inform both research and management priorities in aquaculture and other primary production systems, including risk validation, vector roles in disease epidemiology, compliance with permit conditions, policy development, and treatment options.

This study reports the development of a class of eco-friendlyantifoulingbiocides based on a cyclic dipeptide scaffold, 2,5-diketopiperazine(2,5-DKP). The lead compound cyclo(N-Bip-l-Arg-N-Bip-l-Arg) (1) wassynthesized in gram amounts and used to assess the compatibility withan ablation/hydration coating, efficacy against biofouling, and biodegradation.Leaching of 1 from the coating into seawater was assessedvia a rotating drum method, revealing relatively stable and predictableleaching rates under dynamic shear stress conditions (36.1 +/- 19.7 to 25.2 +/- 9.1 ng(-1) cm(-2) day(-1)) but low or no leaching under static conditions.The coatings were further analyzed using time-of-flight secondaryion mass spectrometry (ToF-SIMS), with 1 seen to localizeat the surface of the coating in a surfactant-like fashion. When coatingswere deployed in the ocean, detectable reductions in biofouling developmentwere measured for up to 11 weeks. After this time, biofouling overwhelmedthe performance of the coating, consistent with leaching kinetics.Biodegradation of 1 in seawater was assessed using theoreticaloxygen demand and analytical quantification. Masking effects wereobserved at higher concentrations of 1 due to antimicrobialproperties, but half-lives were calculated ranging from 13.4 to 16.2days. The results can rationally inform future development towardcommercial antifouling products.

Biofouling of ships' internal seawater systems (ISS) can cause significant operational issues and is a potential transfer mechanism for marine nonindigenous species. This study used an engine room simulator and economic evaluation to quantify impacts on commercial ship performance of biofouling occlusion within various ISS nodes (sea chest, strainer, and heat exchangers). A characteristic hockey-stick relationship between occlusion and impact emerged, whereby engine room systems could tolerate up to 55% occlusion of a single node without operational impact, followed by rapid performance deterioration. The relative magnitude of impacts varied by ISS node and in response to changes in ambient seawater temperatures. System tolerance was much lower when simultaneous occlusion of multiple nodes was assessed. In economic terms, consequences included required freight rate increases of 1-26% prior to forced (automatic) slowdown of the ship and up to 82% increases if slowdown conditions were required.