The Line Islands Collection - a PeerJ Collection

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One of the tools used to investigate the influence of benthic primary producers on the surrounding ecosystem is the Benthic Isolation Tent, here deployed over a reef location dominated by corals on Jarvis, Northern Line Islands.

Coral reefs worldwide are in decline, likely as a result of human carelessness and exploitation. This has been documented by a multitude of studies conducted over the last few decades. But it becomes even more obvious just by looking at different reef locations along a gradient of human exposure. Past and upcoming expeditions to the Central Pacific, particularly to the Line Islands, provide an undeceiving picture of how anthropogenic influence – even as marginal as on those remote islands – changes the face of these remarkably complex ecosystems.

To better understand the mechanisms underlying the alterations in coral reef community compositions the research reported in the Line Islands Collection has focused around interactions between the microbial community and macro-organisms, like fish, coral, or algae, and on the reciprocal effects of both micro- and macro- organisms on key- water parameters like oxygen, carbon, or nutrient concentrations.

The Collection of studies presented here, from a variety of research teams, takes a multidisciplinary approach towards identifying mechanisms which shape the structure of different communities and understanding how these mechanisms are altered along a gradient of anthropogenic disturbance. We try to link abundance and performance of individual organisms or functional groups to the whole community ecology of coral reefs. Specifically, we want to understand what dictates the flow of energy and materials through coral reef ecosystems and how the pathways change following anthropogenic perturbation.

Our research demonstrates that organic matter dynamics are tightly coupled with benthic primary producers and the associated microbial communities. Human influences like fishing, or the input of surplus nutrients are thereby shifting bioavailable energy allocation towards microbes, at the expense of macro-organisms, a process called microbialization. These shifts may create positive feedback loops during transitions from pristine systems, inherently dominated by calcifying benthic organism, to more degraded states which are usually characterized by higher abundance of non calcifying macro- and turf algae. Algae-derived exudates will then select for ineffective and more pathogenic microbial communities, which facilitate regions of decreased oxygen availability through increased metabolic activity, and alter the transfer of energy to higher trophic levels.

Taken as a whole, this Collection investigates the biogeochemical processes, which shape coral reef ecosystems, spanning spatial scales from microns to thousands of kilometers. Presenting these and future studies together will help to understand the findings in their broader context, hopefully providing new aspects for the development of effective management, conservation, and restoration strategies for coral reefs. New articles will be added to the Collection as and when they are published.

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