| Title: | Latitude and protection affect decadal trends in reef trophic structure over a continental scale |
| Author(s): | Madin EMP; Madin JS; Harmer AMT; Barrett NS; Booth DJ; Caley MJ; Cheal AJ; Edgar GJ; Emslie MJ; Gaines SD; Sweatman HPA; |
| Address: | Department of Biological Sciences Macquarie University Sydney NSW Australia. School of Life Sciences University of Technology Sydney Sydney NSW Australia. Hawai'i Institute of Marine Biology University of Hawai'i Kane'ohe HI USA. School of Natural and Computational Sciences Massey University Auckland New Zealand. Institute for Marine and Antarctic Studies University of Tasmania Hobart TAS Australia. School of Mathematical Sciences Queensland University of Technology Brisbane QLD Australia. Australian Research Council Centre of Excellence for Mathematical and Statistical Frontiers The University of Melbourne Parkville VIC Australia. Australian Institute of Marine Science Townsville QLD Australia. Bren School of Environmental Science and Management University of California Santa Barbara CA USA |
| ISSN/ISBN: | 2045-7758 (Print) 2045-7758 (Electronic) 2045-7758 (Linking) |
| Abstract: | "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" |
| Keywords: | coral reef cross-ecosystem fisheries food web kelp forest marine reserve; |
| Notes: | "PubMed-not-MEDLINEMadin, Elizabeth M P Madin, Joshua S Harmer, Aaron M T Barrett, Neville S Booth, David J Caley, M Julian Cheal, Alistair J Edgar, Graham J Emslie, Michael J Gaines, Steven D Sweatman, Hugh P A eng England 2020/08/08 Ecol Evol. 2020 Jun 29; 10(14):6954-6966. doi: 10.1002/ece3.6347. eCollection 2020 Jul" |
