Abstract
Rhodoliths are benthic calcium carbonate nodules accreted by crustose coralline red algae which recently have been identified as useful indicators of biomineral changes resulting from global climate change and ocean acidification. This study highlights the discovery that the interior of rhodoliths are marine biodiversity hotspots that function as seedbanks and temporary reservoirs of previously unknown stages in the life history of ecologically important dinoflagellate and haptophyte microalgae. Whereas the studied rhodoliths originated from offshore deep bank pinnacles in the northwestern Gulf of Mexico, the present study opens the door to assess the universality of endolithic stages among bloom-forming microalgae spanning different phyla, some of public health concerns (Prorocentrum) in marine ecosystems worldwide.
Highlights
Volatile compounds such as dimethyl sulfide (DMS)
Field emission scanning electron microscopy (FESEM) images revealed in fractured cross sections that the inner cells of Lithothamnion sp. 1 rhodoliths harbored abundant spherical, oval and disk-shaped structures (Fig. 1B–E, arrows) occupying the lumen of the coralline’s calcified perithallial cells
Semi-thin sections (24 × 46 mm polished to ≈30 microns) through the rhodoliths revealed dark brown cells in the upper part of the sections with light microscopy (LM) (Fig. 2A), with the same cells in a fluorescence image seen as yellow (Fig. 2B)
Summary
Volatile compounds such as dimethyl sulfide (DMS). The latter has direct effects on the global sulfur cycle and global climate change[23]. Prior to the 2010 Deepwater Horizon oil spill (DWH), extensive rhodolith beds covering the flanks and tops of hard bank pinnacles offshore Louisiana in the NW Gulf of Mexico, such as Ewing Bank (vicinity of 28°05.7′N, 91°01.2′W), typically sustained a lush diversity of encrusting, filamentous and fleshy macroalgae growing on the rhodoliths’ surface[25]. After three weeks in the microcosms, diverse macroalgal growth emerged from the rhodoliths’ surface, a reflection of the algal community present at Ewing Bank prior to DWH25,26. It was newly hypothesized that since macroalgae emerged from the surface of the bare rhodoliths, the latter may serve as seedbanks[25,26], a hypothesis subsequently confirmed by metabarcoding[27]
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