Coastal fish and ecological functions: Identifying the drivers of biodiversity and ecological functions across coastal seascapes
Creators: name: Mosman, Jesse
Publisher: name: University of the Sunshine Coast, Queensland
Year: 2024
Subjects: subject: ecological functions
subject: coastal fish
subject: biodiversity
subject: seascape context
subject: human disturbance
subject: Ecology
subject: FOS: Biological sciences

description: Coastal fishes perform numerous ecological functions, including predation, carrion consumption and herbivory, and these functions shape the condition of coastal ecosystems, alter the structure of food webs, and underpin the resilience of coastal ecosystems to disturbances. Biodiversity is commonly discussed as the driving component of coastal food webs, with greater biodiversity linked to increases in the delivery of multiple ecological functions. However, anthropogenic impacts have modified coastal ecosystems globally, and this has pervasive effects on coastal fish assemblages and the ecological functions they support. These impacts commonly lead to declines in the extent and connectivity of coastal ecosystems, and this seascape context is pivotal in shaping the abundance and diversity of fishes and the ecological functions they perform. Therefore, understanding what drives coastal fish biodiversity and ecological functioning across different coastal seascapes is critical for the management of coastal ecosystems, however, we lack this information in numerous ecosystems. Therefore, in this thesis, I quantified: (1) how scavenger richness and functional diversity modify carrion consumption in the surf zones of ocean beaches; (2); whether predation in three key estuarine habitats (mangroves, seagrass and unvegetated sediment) is modified by predator abundance, predator richness or the abundance of individual species (3); what environmental factors drive fish community composition around rocky headlands; and (4) the impact of urbanisation on coastal fish and crustacean assemblages and the function of carrion consumption across estuaries, rocky headlands and surf zones. Predation probability and rates of carrion were positively correlated with different forms of diversity (i.e. predator species richness, scavenger richness and functional diversity) and this was particularly important when species performing these functions did this in different habitats or spatially distinct areas (i.e. functional complementarity). Seascape context was important in shaping predation and carrion consumption and the abundance, diversity and functional group composition of coastal fish and crustaceans in surf zones. Generally, a greater abundance and diversity of coastal fishes and increased rates of these ecological functions were recorded in larger and well-connected habitats. Coastal urbanisation led to declines in rates of ecological functions, biodiversity and the abundance of harvestable fish species across estuaries, rocky headlands and surf zones, however, generalist species with wide ecological niches were able to dominate and take advantage of highly urbanised areas. These findings have significant implications for the management of coastal ecosystems as I highlight the importance of different forms of diversity in shaping ecological functions and quantifying the influence of seascape context and human disturbance on coastal fishes and the functions they support. I also describe how this information can allow for more informed and targeted management decisions aimed at conserving coastal fishes and the ecological functions they support.