Depth-Dependent Diversity Patterns of Rocky Subtidal Macrobenthic Communities Along a Temperate Fjord in Northern Chilean Patagonia

Understanding the distribution of biodiversity along environmental gradients allows us to predict how communities respond natural and anthropogenic impacts. In fjord ecosystems, overlap strong salinity temperature provides with opportunity assess spatial variation abiotic gradients. However, in Northern Chilean Patagonia (NCP), a unique at same time threatened system, macrobenthic is still poorly known. Here, we tested whether species diversity community structure followed systematic patterns according Comau Fjord, NCP. A spatially extensive nested sampling design was used quantify abundance subtidal axis (fjord sections: head, middle, mouth) depth gradient (0–21 m). The vertical water column strongly stratified head fjord, characterized by superficial (depth ca. 5 m) low-salinity relatively colder layer that shallowed decayed toward mouth fjord. biotic followed, part, this pattern. Species richness peaked high salinities (>27 psu) between 10 m section 15 21 middle sections. Diversity evenness were also highest these ranges sections, but shallower mouth. Information theory-based model selection provided empirical support depth- section-dependent salinity, not temperature, effects on three metrics. Erect algae edible mussel Aulacomya atra numerically dominated shallow (0–3 coinciding horizontal extension low-density layer—these taxa further replaced crustose Lithothamnion sp. deep-dwelling suspension filters (e.g., corals, polychaetes, sponges) gradient. Macrobenthic correlated, therefore, influence freshwater inputs density-driven stratification ecosystem. variable (across both, axes) thresholds observed our study question widely accepted pattern increasing distance from estuarine ecosystems. Finally, non-linear stress models provide predictive power understand responses ecosystems changes.