MEPS 556:45-57 (2016)  -  DOI: https://doi.org/10.3354/meps11822

Rocky islands in a sea of mud: biotic and abiotic factors structuring deep-sea dropstone communities

Kirstin S. Meyer1,*, Craig M. Young1, Andrew K. Sweetman2, James Taylor3, Thomas Soltwedel3, Melanie Bergmann3

1Oregon Institute of Marine Biology, 63466 Boat Basin Road, Charleston, OR 97420, USA
2The Lyell Centre for Earth and Marine Science and Technology, Heriot Watt University, Edinburgh, UK
3Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany
*Corresponding author:

ABSTRACT: Stones released by melting icebergs are called dropstones, and these stones constitute island-like hard-bottom habitats at high latitudes. In 2012, dropstone megafauna in the HAUSGARTEN observatory in the Fram Strait was sampled photographically. We tested the hypothesis that dropstones would have the same species distribution patterns as terrestrial islands, using 5 patterns commonly found in the classical island literature. Higher richness, diversity, and abundance of fauna occurred on larger stones and on stones near a deep-water rocky reef. These patterns can be explained by the greater surface area of larger stones, the exposure of larger stones to faster current higher in the benthic boundary layer, and increased larval supply from the rocky reef. Some pairs of morphotypes (12 pairs out of 56 morphotypes and 1540 possible pairs) co-occurred less often than expected by chance. While similar patterns have been attributed to interspecific competition in the classical island literature, we offer alternative mechanisms for dropstones. Non-random co-occurrence on dropstones may be explained by larval dispersal. Dropstone fauna had an overdispersed (clumped) distribution, so pairs of morphotypes may have negative non-random co-occurrence simply because short larval life and limited dispersal ability prevent them from having randomly overlapping distributions. In addition, we found 8 morphotype pairs that co-occurred more often than expected by chance because of epibiontism. The patterns found in dropstone communities resemble terrestrial islands, but different mechanisms may be responsible.


KEY WORDS: Assembly rules · Island biogeography · HAUSGARTEN · Megafauna · Encrusting fauna · Hard substrata


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Cite this article as: Meyer KS, Young CM, Sweetman AK, Taylor J, Soltwedel T, Bergmann M (2016) Rocky islands in a sea of mud: biotic and abiotic factors structuring deep-sea dropstone communities. Mar Ecol Prog Ser 556:45-57. https://doi.org/10.3354/meps11822

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