Data and code for: Sand drives nonlinear declines in temperate reef algae and invertebrates: spatial variation over 23 years
Résumé fourni par la source
AbstractRocky subtidal reefs are highly productive and diverse coastal ecosystems, providing stable habitat for benthic organisms. Sediment movement across such reefs is common, yet a mechanistic understanding of the ecological responses to variation in sediment over space and time remains incomplete. We used a long-term (12–23 years), spatially replicated (44 transects) annual survey of 160 reef algal and invertebrate taxa to determine how sand dynamics affect reef communities. We quantified how the abundance, diversity, and composition of functional groups responded to spatiotemporal variation in sand cover. We also examined how algal recruitment, community structure, and species turnover responded to changes in sand cover. We investigated the oceanographic, meteorological, watershed, and reef-scale drivers of temporal variability in sand cover. Sand cover had negative, nonlinear effects on algal and invertebrate abundance and diversity, and sandier conditions reduced the likelihood of very high values. Invertebrate abundance also decreased with sand cover under experimental removal of giant kelp, ruling out a confounding effect of this foundation species. Macroalgal recruits were rarer and found in lower densities near sand than near rock. Functional group composition changed with sand variation and community dissimilarity covaried positively with sand-cover differences. Annual species turnover was mediated by year-to-year changes in sand cover. Lastly, temporal variation in sand cover decreased with reef rugosity. These results reveal how sediment dynamics mediate abundance, diversity, composition, and recruitment on temperate reefs, the consequences of spatial and temporal variation in sediment conditions, and the drivers of sediment variability.
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