September 2024
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126 Reads
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2 Citations
Marine Biology
Holopelagic Sargassum spp. (sargassum) are the founding species of diverse communities in the Sargasso Sea. Since 2011, a new area of concentration of these algae was formed in the equatorial North Atlantic and Caribbean Sea. We analyzed elemental composition, and the small mobile fauna associated with sargassum collected at 41 stations, during two expeditions in the Caribbean Sea in 2018 and 2019, that covered open-sea stations in two marine ecoregions, and coastal stations (< 20 km from the shore) in one of them. Metal(loid) concentrations generally followed the order As > Zn > Cu > Cd > Se > Pb > Hg, and contents of As (195.5 ± 13.7 µg g⁻¹), Cd (0.59 ± 0.02 µg g⁻¹), and Hg (0.22 ± 0.09 µg g⁻¹) were highest in S. fluitans III in the South-Western-Caribbean ecoregion. Mean [Ctot] per ecoregion varied between 26.1 and 30.1 mg g⁻¹, and variation was mainly accounted for by higher [Cinorg] (likely produced by calcifying epibionts) in the South-Western Caribbean (10.12) compared to the Western Caribbean (8.92 and 7.19); this tendency that was also found for [Ntot] (between 1.06 and 1.27), and these contents were positively correlated with seawater chlorophyll concentrations. Sixty-six taxa of mobile fauna were identified, with the phylum Arthropoda being most abundant and diverse. The faunal community composition was similar in both open-sea regions, but differed in the coastal stations, which was mostly explained by differential relative abundance of Latreutes fucorum, Carpias minutus, Litiopa melanostoma, and some fish species. The Caribbean open-sea rafts harbor a diverse fauna comparable to that found in the Sargasso Sea, and likely provide similar ecosystem services, and thus merit similar protective efforts as those directed towards sargassum in the Sargasso Sea.