Macro- and microplastics affect cold-water corals growth, feeding and behaviour

Abstract

Plastic contamination is now recognized as one of the most serious environmental issues for oceans. Both macro- and microplastic debris are accumulating in surface and deep waters. However, little is known about their impact on deep marine ecosystems and especially on the deep-sea reefs built by emblematic cold-water corals. The aim of this study was to investigate whether plastics affected the growth, feeding and behaviour of the main engineer species, Lophelia pertusa. Our experiments showed that both micro- and macroplastics significantly reduced skeletal growth rates. Macroplastics induced an increased polyp activity but decreased prey capture rates. They acted as physical barriers for food supply, likely affecting energy acquisition and allocation. Inversely, microplastics did not impact polyp behaviour or prey capture rates, but calcification was still reduced compared to control and in situ conditions. The exact causes are still unclear but they might involve possible physical damages or energy storage alteration. Considering the high local accumulation of macroplastics reported and the widespread distribution of microplastics in the world ocean, our results suggest that plastics may constitute a major threat for reef aggradation by inhibiting coral growth, and thus jeopardise the resilience of cold-water coral reefs and their associated biodiversity.

Figure 1

(A) Average net capture rates of A. salina per polyp during the first hour of feeding and (B) polyp activity after 7, 20 and 47 days of experiment. Values are normalised against controlled conditions (dotted line). All values presented are the median and quartiles.

Figure 2

Average (±SD) skeleton growth rates (mm y⁻¹) of Lophelia pertusa polyps in situ and under aquaria experimental conditions (control, microplastic and macroplastic exposure) after 69 days of incubation.

Figure 3

Representative views of plastic pollutions on Lophelia pertusa reefs in the Lacaze-Duthiers canyon, northwestern Mediterranean Sea. Different types of plastics are found in coral reefs, most of them are bags (A) and bottles (B). Dying (C) or dead (D) coral colonies covered by plastic bags. The distance between green dots is 6 cm. Fondation TOTAL/UPMC.