Ian C. Davidson

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.

Transformational climate adaptation requires coordinated action across sectors and scales, enabled by governance arrangements that can address systemic barriers. Public-private partnerships (PPP) may provide such a mechanism by aligning incentives, pooling resources and fostering collaboration between government and industry. In this paper, we evaluate a national PPP, The Aotearoa Circle (The Circle), and how it has catalysed climate adaptation in Aotearoa New Zealand’s seafood sector. Commissioned by The Circle, we conducted adaptation pathways planning, a decision-support process that identifies and sequences adaptation strategies and actions to reduce future climate risk, for two fisheries and two aquaculture industries. The process engaged company, government, research and civil society stakeholders to design suites of incremental and transformational strategies to reach long-term industry goals, and actions to implement them. We analysed these outputs to assess the PPP’s relevance in enabling implementation. Amongst the transformational pathways, 48% of actions required collaboration by public and private entities. Strategies were also identified to address systemic adaptation barriers across the sector (agile regulation, climate forecasting, fleet decarbonisation, oceans research). For these, the majortiy of actions required leadership by The Circle or public-private collaborations. Key informant interviews revealed challenges in implementation of immediate actions. While some were underway, shifts in national government policies had resulted in uneven progress amongst the industries. Interviewees emphasised the necessity for The Circle to convene stakeholders and sustain momentum, but resourcing was a constraint. Our results highlight The Circle’s core role in enabling transformational adaptation within industries and across the sector. Yet the PPP remains vulnerable to political cycles, shifting public sector commitment and risk aversion. Strengthening PPP resourcing arrangements is necessary to action long-term adaptation, and to ensure iterative pathways planning.

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.

Societal Impact Statement: The invasive species S. alterniflora and P. australis are fast growing coastal wetland plants sequestering large amounts of carbon in the soil and protect coastlines against erosion and storm surges. In this global analysis, we found that Spartina and Phragmites increase methane but not nitrous oxide emissions, with Phragmites having a lesser effect. The impact of the invasive species on emissions differed greatly among different types of native plant groups, providing valuable information to managers and policymakers during coastal wetland planning and restoration efforts. Further, our estimated net emissions per wetland plant group facilitate regional and national blue carbon estimates.Summary: Globally, Spartina alterniflora and Phragmites australis are among the most pervasive invasive plants in coastal wetland ecosystems. Both species sequester large amounts of atmospheric carbon dioxide (CO₂) and biogenic carbon in soils but also support production and emission of methane (CH₄). In this study, we investigated the magnitude of their net greenhouse gas (GHG) release from invaded and non‐invaded habitats. We conducted a meta‐analysis of GHG fluxes associated with these two species and related soil carbon content and plant biomass in invaded coastal wetlands. Our results show that both invasive species increase CH₄ fluxes compared to uninvaded coastal wetlands, but they do not significantly affect CO₂ and N₂O fluxes. The magnitude of emissions from Spartina and Phragmites differs among native habitats. GHG fluxes, soil carbon and plant biomass of Spartina‐invaded habitats were highest compared to uninvaded mudflats and succulent forb‐dominated wetlands, while being lower compared to uninvaded mangroves (except for CH₄). This meta‐analysis highlights the important role of individual plant traits as drivers of change by invasive species on plant‐mediated carbon cycles.

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.

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.

Pests of bivalve aquaculture are a challenging problem that can reduce productivity, profitability and sustainability. A range of pest management approaches have been developed for bivalve aquaculture, but a general absence of guiding frameworks has limited the scale and permanency of implementation. Applying principles of ‘integrated pest management’ (IPM) could change this paradigm to improve economic and environmental outcomes. We reviewed existing research and tools for pest management in bivalve aquaculture, with studies grouped under five pillars of IPM: pest ecology (25 studies), bioeconomic cost–benefits (4 studies), continual monitoring (17 studies), proactive prevention (32 studies) and reactive control (65 studies). This body of knowledge, along with insights from terrestrial agriculture, provide a strong foundation for developing and implementing IPM in bivalve aquaculture. For example, IPM principles have been applied by a regional collective of oyster farmers in the US Pacific Northwest to optimize pesticide application and search for other options to control problematic burrowing shrimps. However, IPM has not yet been broadly applied in aquaculture, and data gaps and barriers to implementation need to be addressed. Priorities include establishing meaningful pest–crop bioeconomic relationships for various bivalve farming systems and improving the efficacy and operational scale of treatment approaches. An IPM framework also could guide potential step‐change improvements through directing selective breeding for resistance to pests, development of bespoke chemical control agents, applying emerging technologies for remote surveillance and farm management, and regional alignment of management interventions. © 2022 Society of Chemical Industry.

Internal seawater systems (ISS) are critical to the proper functioning of maritime vessels. Sea water is pumped on board ships for a broad array of uses, primarily for temperature control (e.g., engine and electrical systems), cooling capacity (e.g., air conditioners and refrigeration), and water provision (e.g., drinking, firefighting, steam, and ballast). Although sea water may spend only a brief period within ISS of a vessel, it can carry microorganisms and larval stages of macroorganisms throughout the system leading to biofouling accumulation that can impair system function or integrity. ISS can also act as a sub-vector of species translocations, potentially facilitating biological invasions. This review describes ships’ ISS with a focus on operational impacts of biofouling and current drivers and barriers associated with ISS biofouling management. As ISS internal components are difficult to access, reports and studies of ISS biofouling are uncommon and much of the dedicated literature is decades old. The impact of biofouling on ISS and vessel operations is based on increased surface roughness of pipework and equipment, restricted water flow, corrosion and subsequent component impingement, reduced surface functional efficiency, and potential contamination by pathogens that can affect human and aquatic animal health. Biofouling management is primarily achieved using antifouling coatings and marine growth prevention systems, but independent and accessible data on their efficacy in ISS remain limited. Further research is required to resolve the extent to which biofouling occurs in ISS of the modern commercial fleet and the efficacy of preventive systems. Such information can ultimately inform decisions to improve operational efficiency for vessel operators and ensure any biosecurity risks are appropriately managed.