@phdthesis{fdi:010098094,
  title = {{M}arines heatwaves in the {S}outhwestern {T}ropical {P}acific : characteristics and impact on coastal fisheries},
  author = {{L}al, {S}.},
  editor = {},
  language = {{ENG}},
  abstract = {{M}arine heatwaves ({MHW}s), defined as discrete, prolonged periods of anomalously high ocean temperatures, have become an increasingly frequent environmental challenge for the global ocean, with significant consequences for certain species, ecosystems, communities and economies dependent on marine resources. {T}his {P}h{D} thesis investigates the characteristics, drivers, and ecological impacts on coastal fisheries from historic {MHW}s in the {S}outhwestern tropical {P}acific. {P}articular emphasis has been placed on characterizing these events within the {E}xclusive {E}conomic {Z}ones ({EEZ}s) and along the coastlines of 12 {P}acific {I}sland {C}ountries and {T}erritories ({PICT}s), to enhance the usefulness of this study's outputs for natural resource management efforts in these {PICT}s. {U}sing a range of oceanic temperature products, this research assessed {MHW}s at the surface and their subsurface extensions. {A} polygon-based spatial method was developed to quantify {MHW} spatial extent. {M}icroscale and macroscale {MHW}s were characterized based on their spatial extents and seasonality. {I}t was shown that distinguishing {MHW}s by size (spatial extent) and seasonality can greatly affect their characterisation (in terms of areas affected, duration and intensity) and help trace their physical drivers. {A}ll 12 {PICT}s experienced {MHW}s in the past 30 years with events getting more frequent with greater spatial extents, longer durations, but with less intensity. {A} significant long-term trend in the annual number of {MHW} days was also observed along coastlines of {S}olomon {I}slands, {V}anuatu, {T}onga, {F}iji and northern {N}ew {C}aledonia. {PICT}s in the {S}outhwest {P}acific ({N}ew {C}aledonia, {V}anuatu, {F}iji) were more exposed to higher intensity events, with {N}ew {C}aledonia and {V}anuatu also experiencing longer duration events. {T}hese {PICT}s were found to experience more macro-scale events, indicating possible links to heat flux changes over a large area in link with large-scale climate modes. {T}his thesis also highlighted that seasonality could play key roles in determining {MHW} vertical extent due to its effect on mixed layer depths. {S}easonality also affects how {MHW}s impact ecology, since they have more damaging effects in hot season compared to cold season. {T}his thesis also presents an analysis of the main mechanisms and drivers of a case study, the major {MHW} event which occurred in {F}ebruary 2016 resulting in massive coral bleaching in the region. {I}t was explained by a rare combination of a suppressed phase of the {M}adden {J}ullian {O}scillation superposing on the strong 2015-2016 {E}l {N}iño event, resulting in exceptional low winds and clear sky conditions. {T}his {MHW} dissipated after the passage of a tropical cyclone. {F}inally, this {P}h{D} examined the ecological response of coastal fish growth from otolith records to historic {MHW}s. {F}ish life history parameters from five coastal reef fish species; {C}ephalopholis argus, {N}aso lituratus, {C}tenochaetus striatus, {N}aso unicornis and {L}utjanus fulvus sourced from {T}onga and {C}ook {I}slands were used along with coastal {MHW} parameters to explain their growth rates (otolith increment rates), to understand the impact of {MHW}s. {R}esults revealed, first, the complexity of finding clear relationships between {MHW}s and marine species in general. {W}e showed that there was species-specific sensitivity, with only two species ({C}ephalopholis argus and {L}utjanus fulvus) showing significant negative growth responses. {T}his research highlights the importance of combining multiple approaches (physical oceanographic, ecological and socio-economic) to understanding environmental challenges as complex and at times controversial (due to choice of definition, baselines, detrending, resolution) as {MHW}s. {T}his thesis serves as a foundation and guide for future investigations into the physical and ecological dynamics of {MHW}s in the {P}acific and provides insights useful to inform conservation efforts in {PICT}s.},
  keywords = {{PACIFIQUE}},
  address = {{T}oulouse},
  publisher = {{U}niversit{\'e} de {T}oulouse 3 - {P}aul {S}abatier},
  pages = {203  multigr.},
  year = {2026},
  URL = {https://www.documentation.ird.fr/hor/fdi:010098094},
}