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140200 - Latitude and protection affect decadal trends in reef trophic structure over a continental scale.pdf (1.04 MB)
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Latitude and protection affect decadal trends in reef trophic structure over a continental scale

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journal contribution
posted on 2023-05-20, 16:35 authored by Madin, EMP, Madin, JS, Harmer, AMT, Neville BarrettNeville Barrett, Booth, DJ, Caley, MJ, Cheal, AJ, Graham EdgarGraham Edgar, Emslie, MJ, Gaines, SD, Sweatman, HPA
The relative roles of top‐down (consumer‐driven) and bottom‐up (resource‐driven) forcing in exploited marine ecosystems have been much debated. Examples from a variety of marine systems of exploitation‐induced, top‐down trophic forcing have led to a general view that human‐induced predator perturbations can disrupt entire marine food webs, yet other studies that have found no such evidence provide a counterpoint. Though evidence continues to emerge, an unresolved debate exists regarding both the relative roles of top‐down versus bottom‐up forcing and the capacity of human exploitation to instigate top‐down, community‐level effects. Using time‐series data for 104 reef communities spanning tropical to temperate Australia from 1992 to 2013, we aimed to quantify relationships among long‐term trophic group population density trends, latitude, and exploitation status over a continental‐scale biogeographic range. Specifically, we amalgamated two long‐term monitoring databases of marine community dynamics to test for significant positive or negative trends in density of each of three key trophic levels (predators, herbivores, and algae) across the entire time series at each of the 104 locations. We found that trophic control tended toward bottom‐up driven in tropical systems and top‐down driven in temperate systems. Further, alternating long‐term population trends across multiple trophic levels (a method of identifying trophic cascades), presumably due to top‐down trophic forcing, occurred in roughly fifteen percent of locations where the prerequisite significant predator trends occurred. Such alternating trophic trends were significantly more likely to occur at locations with increasing predator densities over time. Within these locations, we found a marked latitudinal gradient in the prevalence of long‐term, alternating trophic group trends, from rare in the tropics (<5% of cases) to relatively common in temperate areas (~45%). Lastly, the strongest trends in predator and algal density occurred in older no‐take marine reserves; however, exploitation status did not affect the likelihood of alternating long‐term trophic group trends occurring. Our data suggest that the type and degree of trophic forcing in this system are likely related to one or more covariates of latitude, and that ecosystem resiliency to top‐down control does not universally vary in this system based on exploitation level.

Funding

Australian Research Council

Department of Environment, Water and Natural Resources

Department of Natural Resources and Environment Tasmania

Department of Parks and Wildlife (Western Australia)

Department of Primary Industries NSW

Parks Victoria

Smithsonian Institution

History

Publication title

Ecology and Evolution

Volume

10

Issue

14

Pagination

6954-6966

ISSN

2045-7758

Department/School

Institute for Marine and Antarctic Studies

Publisher

John Wiley & Sons Ltd.

Place of publication

United Kingdom

Rights statement

© 2020 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Repository Status

  • Open

Socio-economic Objectives

Marine biodiversity