Madrepora oculata forms large frameworks in hypoxic waters off Angola (SE Atlantic)

Covadonga Orejas,Claudia Wienberg,André Freiwald,Dierk Hebbeln,Jürgen Titschack,Leonardo Tamborrino

doi:10.1038/s41598-021-94579-6

Covadonga Orejas, Claudia Wienberg + Show 4 more

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https://doi.org/10.1038/s41598-021-94579-6

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Abstract

This study aims to map the occurrence and distribution of Madrepora oculata and to quantify density and colony sizes across recently discovered coral mounds off Angola. Despite the fact that the Angolan populations of M. oculata thrive under extreme hypoxic conditions within the local oxygen minimum zone, they reveal colonies with remarkable heights of up to 1250 mm—which are the tallest colonies ever recorded for this species—and average densities of 0.53 ± 0.37 (SD) colonies m−2. This is particularly noteworthy as these values are comparable to those documented in areas without any oxygen constraints. The results of this study show that the distribution pattern documented for M. oculata appear to be linked to the specific regional environmental conditions off Angola, which have been recorded in the direct vicinity of the thriving coral community. Additionally, an estimated average colony age of 95 ± 76 (SD) years (total estimated age range: 16–369 years) indicates relatively old M. oculata populations colonizing the Angolan coral mounds. Finally, the characteristics of the Angolan populations are benchmarked and discussed in the light of the existing knowledge on M. oculata gained from the North Atlantic and Mediterranean Sea.

Highlights

This study aims to map the occurrence and distribution of Madrepora oculata and to quantify density and colony sizes across recently discovered coral mounds off Angola
The highest average values for population density are documented for the NE Atlantic sites (Iceland, Ireland, Bay of Biscay) with values ranging from 0.53 ± 0.61 (SD) colonies m−2 to 1.64 ± 1.19 (SD) colonies m−24, whereas M. oculata populations in the Mediterranean display average densities ranging from 0.11 ± 0.44 (SD) colonies m −2 (Cap de Creus canyon, Gulf of L ions7) to averages of 0.81 ± 1.87 (SD) colonies m −2 (Cabliers coral mound province, Alborán Sea15)
Even though, M. oculata was found in comparably low numbers of live and dead colonies (Fig. 2, Table 1), the average density of M. oculata thriving on the Angola coral mounds (0.53 ± 0.37 (SD) colonies m−2) was in the same order of magnitude as previously documented for the Mediterranean Sea (0.30 ± 1.14 (SD) to 0.81 colonies m−27,15)

Summary

Introduction

Despite the fact that the Angolan populations of M. oculata thrive under extreme hypoxic conditions within the local oxygen minimum zone, they reveal colonies with remarkable heights of up to 1250 mm—which are the tallest colonies ever recorded for this species—and average densities of 0.53 ± 0.37 (SD) colonies m−2. This is noteworthy as these values are comparable to those documented in areas without any oxygen constraints. A mixed assemblage of L. pertusa and M. oculata colonizing coral mounds off Mauritania—though in low numbers and spatially dispersed—are exposed to even lower DO of 1.0–1.3 mL L −129,30

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