The cover image for Journal of Ecology’s latest issue was taken by Robert Streit. Here Robert and co-authors, Sterling Tebbett and David Bellwood, discuss the story behind this amazing underwater photograph.

This photo relates to recently their published research article “A 3D perspective on sediment accumulation in algal turfs: Implications of coral reef flattening“

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Images of coral reefs usually show a bustling diversity of beautiful fishes swimming amongst colourful corals. But there is more to coral reefs than these photogenic celebrities. In our study (and cover photo) we focussed on an often undervalued wallflower of coral reefs: algal turfs.

Algal turfs are the greenish, brownish, fuzzy films that cover virtually all surfaces on reefs that aren’t already occupied (by corals or other organisms like sponges). They are highly productive, grow fast and get eaten by algae-feeding fishes, such as surgeonfishes, rabbitfishes and parrotfishes. Because they are everywhere and grow so quickly, they provide a lot of the energy that sustains coral reef productivity. But fishes won’t eat any old algal turf.

The turfs in our photo are fresh, small and clean. However, sediment can build up within these turfs making them unappealing for fishes to eat. As a result, turfs get longer and in turn can trap even more sediment until a vicious cycle leads to “long sediment-laden algal turfs” (LSATs) that are effectively a stable, but energetic dead-end on coral reefs.

In our study, we used 3D models and turf measurements to analyse how coral reef complexity influences the nature of these algal turfs and their propensity to retain sediments. We found that lower and flatter surfaces had longer and less nutritious algal turfs, while elevated peaks supported short, low-sediment turfs that are likely to be preferred feeding spots for herbivorous fishes.

Unfortunately, coral reefs seems to be heading towards a flatter future. Storms and coral bleaching that can kill and rubble-ise structurally complex coral, are only likely to become more intense and frequent because of climate change. Such effects of climate change have become clearly visible at our main study site. The cover photo was taken in the lagoon of Lizard Island in the northern Great Barrier Reef in Australia, just after the region had suffered through two back-to-back coral bleaching events.

The key now is not to despair, but to embrace the changes the ecosystem has undergone. For us, this means focussing on the ecological processes that will shape the reefs of the future. Algal turfs are quick to colonise the space vacated by coral and if we can keep them in a healthy state, and manage sedimentation and water quality, they may be the foundation for a thriving, if different, ecosystem.

The humble algal turfs may often fade in the background when we think about coral reefs, yet their role in the future of coral reefs will be centre-stage.

Sterling B. Tebbett, Robert P. Streit & David R. Bellwood
James Cook University, Australia
www.thebellwoodreeffishlab.com

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Read the full research article online: A 3D perspective on sediment accumulation in algal turfs: Implications of coral reef flattening by Tebbett, Streit & Bellwood

Find out what else features in Volume 108, Issue 1 of Journal of Ecology here: https://jecologyblog.com/2019/12/16/volume-108-issue-1/