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Ocean acidification (OA) presents a fundamental challenge to marine biodiversity and sustained ecosystem health. Reproductive and developmental processes are considered to be particularly vulnerable to OA. My PhD research examined reproductive response (measured as nauplii production), cuticle composition and stage specific growth for the copepod Tisbe battagliai over three generations at four tightly regulated pH conditions (pH 7.67, 7.82, 7.95±0.02; pH 8.l±0.06) and for combined impact ofOA and environmentally relevant copper concentrations. As part of my case studentship with the MBA I also examined OA effects on spermatophore attachment and seminal fluid stores in the female reproductive system. A significantly increased naupliar production at pH 7.95 was attributable to an initial stress response which was succeeded by a hormesis- like response at pH 7.67. The significantly decreased naupliar production at pH 7.82 was the first part of a biphasic reproductive response followed by a compensatory increase in naupliar production at pH 7.67 remaining below control levels. This pattern was consistent across all generations and broods. A mixed effects model predicted a gradual decline in naupliar production over the next 100 years (equivalent to approximately 2,430 generations). Growth (mean length integrated across all developmental stages) decreased significantly below control values at pH 7.82, and 7.67. Cuticle elemental analysis indicated significant alterations in oxygen and carbon content as seawater pH decreased. Changes in growth, cuticle composition and nauplii production strongly suggest that when under OA-induced stress copepods will preferentially reallocate resources in favour of maintaining reproductive output at the expense of somatic growth and cuticle integrity. Experiments incorporating additional copper with increasing OA observed significantly increased naupliar production at pH 8.10, this was followed by a significant reduction in naupliar production beyond that of OA alone from pH 7.95, to pH 7.82, and 7.67. Growth significantly increased with addition of copper, compared to OA impact alone. Cuticle elemental composition observed significant reductions in sulphur, phosphorus and calcium concentrations for those copepods subjected to combined OA and copper. Copepods subjected to additional copper with increasing OA were taking up copper which not only increased metabolism observing a significant increase in growth, but also became toxic observed with a significant further reduction in naupliar production. Addition of copper was seen to have an additive detrimental effect on naupliar production and the copepod population as observed from the mixed effects model output. Techniques developed in . ii. confocallaser scanning microscopy enabled the comparison of seminal fluid stores within the female reproductive system. No significant differences were observed between female reproductive structures and seminal fluid stores with increasing OA from pH 8.1 0 to pH 7.67. Spermatophore size significantly decreased with increasing OA, however to the same extent of female copepod size.

Cette thèse contient quatre études majeures ciblant l'aquaculture des copépodes : (1) les conditions optimales de la culture de deux espèces tropicales, le calanoide Acartia bilobata et le cyclopoide Apocyclops royi ; (2) les œufs de résistance d'A. bilobata ; (3) les effets d'une sélection d’une souche performante d’A. royi en utilisant un nouveau protocole multi-générationnel et thermique ; (4) la pertinence de l’introduction des copépodes dans le régime alimentaire des larves de poissons. Pour le nourrissage des copépodes, les micro-algues de petites tailles (3-6 µm) riches en acides gras polyinsaturés (AGPI) sont plus avantageuses pour les deux espèces testées dans cette étude. De plus, nous avons démontré qu’A. royi, contrairement à A. bilobata, est capable de synthétiser des chaines longues d’AGPI à partir de chaines plus courtes d’AGPI. La salinité optimale pour le développement de la population est égale à 20. Les différentes caractéristiques de production d'œufs quiescents et de diapause, viables pendant plusieurs mois après stockage à 4°C, ont été identifiées chez deux souches d'A. bilobata. Une expérience de sélection de femelles d’A. royi a combiné les critères de productivité et du profil lipidique. Basé sur nos résultats obtenus sur l’élevage de larves de poissons, le régime alimentaire basé sur les nauplii d’A. tonsa obtenus en utilisant les œufs de résistance stockés à faible température, pourrait être avantageux pour des larves pélagiques; cependant, l'utilisation d'A. royi comme proie vivante devrait être soigneusement évaluée par la considération spécifique du comportement de nage de l'espèce de poisson ciblée. / The present thesis contains four major studies addressed on copepod aquaculture: (1) optimal culture conditions of two tropical copepod species Acartia bilobata (Calanoida) and Apocyclops royi (Cyclopoida); (2) resting eggs of A. bilobata; (3) effects of thermal selective breeding on A. royi; (4) feeding suitability of copepod-based diets on larval fish. For copepod feeding, small-sized microalgae (3-6 μm) with rich polyunsaturated fatty acids (PUFAs) are preferable for both copepod species. Furthermore, we found that the cyclopoid A. royi, contrary to the calanoid A. bilobata, is capable of synthesizing long-chain PUFAs from short-chain PUFAs. The salinity affects differently the A. royi at different life stages, but it is suggested to cultivate this species at salinity 20 for the highest productivity. Various features of quiescent and diapausing eggs productions are identified in two culture strains of A. bilobata with different domestication levels, and those eggs remain viable after several months of cold storage (4°C). The larger female with higher nauplii production and compensative fatty acid increase were obtained in the cold-selected strain of A. royi. Based on our results found in fish larvae feeding trials, the diet based on A. tonsa nauplii derived from quiescent eggs could be beneficial for pelagic fish larvae; however, the use of A. royi as live prey should be carefully evaluated by the specific consideration of swimming behavior of targeted fish species. This thesis reveals the biological and physiological understandings on copepods, and provides implications on the application of copepods as promising live prey for larviculture.