Ice fish as sentinels for understanding how environmental changes impact food web diversity and stability in Antarctica

Investigating how environmental variation influences population, food web, and community dynamics is important for predicting the influence of climate change on ice covered ecosystems. The sea ice gradient that runs from north to south in McMurdo Sound presents a unique opportunity to study how locations with contrasting physical and biological properties influence the structure of marine food webs. Accordingly we have studied the ecological position of four ice fish species, at sites across the sea ice gradient, that occupy contrasting habitats in the Antarctic marine environment. These ice fish act as important sentinel species to better understand how environmental changes may impact food web diversity and stability in the region. The primary objective of the present study was to determine how changing resource availability, relating to the composition of primary producers, across the sea ice gradient, influences the trophic ecology of ice fish with pelagic and benthic habits. We also aimed to determine if resource availability effected aspects of growth and reproduction in the different ice fishes. Finally we aimed to see if chemical and chronological properties of ice fish otoliths could be used as environmental recorders, for conditions in the seasonal sea ice. Ice fish were collected from a range of sites across McMurdo Sound using the conventional hook and line method, as well as with hand nets used by divers. Dietary, stable isotope, age and growth, microscopic gonadal, and otolith trace element analyses were conducted on each of the ice fish collected. As a result of the analyses conducted, we concluded that the trophic dynamics of ice fish differ among species and among sites distributed along the sea ice gradient in McMurdo Sound. Benthic species located at the inner sites in McMurdo Sound derived the highest proportion of diet from food webs supported by the sea ice microbial community, indicating benthic communities at these sites may be more susceptible to changes in sea ice conditions. Age and growth trajectories, and reproductive strategies were found to differ between pelagic and benthic species. Benthic species were characterised as slower growing, summer spawners, while pelagic species displayed faster growth and are thought to spawn in winter. Our results also indicated that position along the sea ice gradient may affect aspects of growth and reproduction for ice fish. Lastly we identified ice fish otoliths as potential recorders of, the life history of ice fish species; and the physical and chemical conditions of contrasting habitats, linked with dynamics of sea ice conditions in Antarctica. From the present study we can conclude that climate related changes to sea ice conditions in Antarctica will effect populations of ice fish differently depending on their species, habitat, location, and sex ratios. The susceptibility of ice fish populations to environmental changes acts as an indicator for how other species connected to the same food webs will be effected by changes to sea persistence in Antarctica. The microchemistry of ice fish otoliths may offer a repeatable way to study the environmental history of ice covered habitats in Antarctica. This would allow environmental variation to be linked to the chemical, physical, and ecological changes occurring at a location

Tracking flow and fate of organic matter and contaminants within native food webs surrounding finfish aquaculture

The development of aquaculture to provide a source of protein has the potential to alleviate pressure on wild fish stocks, allowing marine systems to regenerate while providing livelihood to millions of people. Given the rapid expansion of aquaculture anticipated to occur in New Zealand, it is important that development of the industry is managed in a sustainable way so that detrimental impacts are mitigated, and opportunities for humans and native ecosystems are enhanced. Fin-fish aquaculture produces organic and nutrient waste which, in excess, can act to reduce productivity and diversity in communities. However, native marine communities, likely have some capacity to assimilate this waste and utilise it as a resource subsidy. This research firstly aimed to improve the ability of researchers to model resource use in coastal marine food webs associated with aquaculture. Baseline values for stable isotope (SI) and fatty acid (FA) biomarkers in key organic matter source pools available to consumer populations in the Marlborough Sounds were established (Chapter 2). Controlled experiments were then used to estimate parameters that predict the transfer of these signatures to consumer tissue over time (Chapter 2). Secondly, these experimentally determined biomarkers and mixing model parameters were applied to the Marlborough Sounds system to determine the extent at which soft sediment and rocky reef communities assimilate waste from farms, and the consequences this input has on food web structure (Chapters 3 and 4). Finally, after establishing assimilation of waste by reef consumers, organic contaminants were measured in feed and consumer tissues to determine whether imported feed acts as a significant source of these compounds to the New Zealand marine environment (Chapter 5). Stable isotope and fatty acid biomarkers of native marine production and aquaculture production were found to be distinct, establishing these tracers as suitable for use in in-situ systems. Mesocosm experiments found isotopic turnover rates and trophic discrimination of FAs and SIs to differ considerably among consumers and tissue types, underscoring the importance of establishing experimentally determined parameters when modelling resource use and trophic dynamics in marine ecosystems. Application of experimentally determined values to mixing models for the Marlborough Sounds system predicted assimilations of salmon farm waste in all farm associated soft sediment communities, and most farm associated reef consumers sampled. This finding suggests integrated multi-trophic aquaculture (IMTA) may have implications for a diverse range of species in New Zealand. The capacity of communities to uptake and process waste from farms showed high variability both across distance gradients from farms and among farm sites. Assimilation capacity of communities was strongly influenced by trophic structure with the presence of high trophic level consumers indicative of a greater potential to buffer detrimental effects from excess waste deposition. The results presented in Chapters 3 and 4 of this thesis have implications for determining suitable feed inputs to farms, identifying promising species for IMTA development, and informing remedial action to soft sediment communities. Levels of polychlorinated biphenyls, and polybrominated diphenyl ethers measured in both feed and consumer tissues were below limits set by the European Union and, in most consumers, levels were not significantly influenced by the presence of salmon farms. The exception was P. colias, in which PCB levels were elevated around farms potentially as a consequence of P. colias’s trophic link to proximal benthic communities. Identifying P. colias as a candidate for bioaccumulation and/or biomagnification of harmful compounds may guide future monitoring of organic contaminants in species interacting with aquaculture operations. The sustainable development of aquaculture will be essential not only in New Zealand but also globally if we are to ensure a reliable source of protein to the world’s growing population while addressing the impacts of climate change and environmental degradation on natural resource bases. Implications of the present research include, understanding ecosystem structure and function and how this relates to finfish aquaculture, guiding future management and monitoring programmes, and evaluating marine systems and their capacity to recycle organic waste from aquaculture

Transformation of cytogenetically normal chronic myelomonocytic leukaemia to an acute myeloid leukaemia and the emergence of a novel +13,+15 double trisomy resulting in an adverse outcome

A 58-year-old man was admitted with symptoms of lethargy and easy bruising for four months duration. Peripheral blood (PB) analysis revealed a white blood cell count (WBC) of 15.9 × 109/l with monocytes 5.4 × 109/l. Bone marrow (BM) was hypercellular with 15% blasts, monocytosis and trilineage dysplasia. Conventional cytogenetic analysis (G-banding) detected an apparently normal male karyotype (46,XY). A diagnosis of chronic myelomonocytic leukaemia (CMML) was made. After 3 years, PB analysis revealed a WBC count of 22 × 109/l and a predominance of blasts. BM aspirate analysis also revealed 89% myeloid blasts and G-banding detected the emergence of an abnormal clone harbouring an extra copy of chromosomes 13 and 15. A diagnosis of disease transformation to acute myeloid leukaemia (AML) was made. Post chemotherapy BM aspirate was very hypocellular and the abnormal +13,+15 clone was still present suggesting primary refractory disease. A second course of chemotherapy was only administered for 24 hours due to complications. The abnormal +13,+15 clone was still present and it was decided that no further treatment apart from palliative care could be offered. The patient died 11 weeks later, five months after AML transformation. This is the first description of a cytogenetically normal CMML patient transforming to AML with the emergence of a unique +13, +15 double trisomy resulting in an adverse outcome