Patterns in the chaos: Scale and the spatiotemporal dynamics of coral reef fish assemblages on the Great Barrier Reef

Ecosphere, Journal Year: 2025, Volume and Issue: 16(5)

Published: May 1, 2025

Abstract In the Anthropocene, understanding and managing ecological communities requires characterization of natural spatiotemporal ecosystem dynamics. Complex ecosystems may appear chaotic unstructured, making long‐term monitoring programs with hierarchical sampling designs ideal for investigating patterns at multiple scales. Here, we use a dataset spanning entire Great Barrier Reef (GBR) decades to determine spatial distribution abundance, how these change through time, in 233 reef‐associated fish species. Community composition was strongly structured by position across continental shelf, distinct inner outer shelf assemblages. Latitudinal differences were smaller, except distinctive assemblages southernmost Swain Capricorn‐Bunker regions. GBR‐wide summaries total density species richness did not show directional shifts, it only after analyzing metrics subregional scale that wider range temporal oscillations identified, indicating responses perturbations require examination smaller than GBR Within most subregions (65%), has undergone clear ongoing shift away from community identified 1990s. These changes generally due reduction numbers coral‐dependent an increased dominance grazers generalists. Among species, there have been more “winners” “losers” whole GBR, but this masks tendency reefs central over time. on are dynamic recovery potential disturbance events. Despite some pervasive community‐level shifts last decades, biogeographic characteristics each subregion remain intact. We pose question whether is reasonable expect highly reach relatively stable “climax community,” posit answer scale‐dependent and, currently resolved scale, which stakeholders decision‐makers operate.

Language: Английский

Effects of flow speed and prey density on the rate and efficiency of prey capture in zooplanktivorous coral-reef fishes

Frontiers in Marine Science, Journal Year: 2024, Volume and Issue: 11

Published: March 21, 2024

Holling’s classical functional response model describes the mechanistic foundations of relationships between predation rate and prey density. As such, is pertinent to predators that actively search for prey, but not stationary in which additional factors, such as flow speed, determine rates encounter. The main objective this study was measure corresponding efficiencies zooplanktivory among different common species coral-reef fishes under a wide range densities current speeds. All our experiments were carried out flume with combinations speeds (3-28.5 cm/s) (210 - 1050 m -3 ). Nauplii Artemia salina used prey. Despite major differences taxonomic origin studied species, their morphologies, types shelters they use, foraging performances fish, rates, way those affected by density speed surprisingly similar. Under fixed density, capture did change much function speed. conditions equal flux, always higher high weaker than lower faster flow. A sharp decline efficiency increasing explained narrowing fish’s body orientation relative In other words, fish gradually became more-narrowly oriented head-on onto flow, exhibiting decrease frequency turns (“maneuverability”). These trends, especially reduced maneuverability strong currents, can explain findings increase when hence increased. Inter-specific efficiencies, however small, agree well observed type habitats occupy.

Language: Английский