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Updated: Dec 4, 2025

Coral Reef Arks: An In Situ Mesocosm and Toolkit for Assembling Reef Communities

Coral Reef Arks: An In Situ Mesocosm and Toolkit for Assembling Reef Communities

Published on: January 6, 2023

Trophic downgrading reduces spatial variability on rocky reefs.

Matthew S Edwards¹, Brenda Konar²

¹Department of Biology, San Diego State University, 5500 Campanile Dr., San Diego, CA, 92182, USA. medwards@sdsu.edu.

Scientific Reports

|October 23, 2020

Summary

This summary is machine-generated.

Trophic downgrading impacts coastal ecosystems. Kelp forests show greater small-scale spatial variation than sea urchin barrens, suggesting a shift in ecological control mechanisms.

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Measuring the Structure, Composition, and Change of Underwater Environments with Large-area Imaging

Measuring the Structure, Composition, and Change of Underwater Environments with Large-area Imaging

Published on: April 18, 2025

Area of Science:

Marine Ecology
Ecosystem Dynamics
Conservation Biology

Background:

Globally, coastal waters experience trophic downgrading, leading to kelp deforestation and sea urchin barrens on temperate rocky reefs.
Predatory sea otter loss in the Aleutian Archipelago has caused significant trophic downgrading of kelp forests.

Purpose of the Study:

To test the hypothesis that intact kelp forest communities exhibit greater spatial variability than degraded sea urchin barren communities.
To determine if differences in spatial variability are scale-dependent and influenced by trophic interactions.

Main Methods:

Conducted benthic community surveys across nine islands in the Aleutian Archipelago, covering 1230 km.
Compared community composition and spatial variation in kelp forests versus sea urchin barrens.
Analyzed spatial variability at small (within-forest/barren) and large (among-island) spatial scales.

Main Results:

Kelp forests contained more species and exhibited greater overall spatial variation in community composition than urchin barrens.
Kelp forest communities were most variable at small scales and least variable at large scales.
Urchin barren communities showed the opposite pattern: low small-scale variability but high large-scale variation across the archipelago.

Conclusions:

Aleutian kelp forests create diverse microhabitats, leading to high within-forest variability but similarity across islands.
Urchin barrens display limited internal variability but significant differences among barrens, indicating a shift from biological to oceanographic control.
Trophic downgrading fundamentally alters spatial community structuring in these marine ecosystems.