CSIR-National Institute of Oceanography, Dona Paula, 403004, Goa, India.
School of Earth, Ocean and Atmospheric Sciences, Goa University, Taleigao Plateau, 403 206, Goa, India.
Environ Sci Pollut Res Int. 2024 Sep;31(44):56253-56271. doi: 10.1007/s11356-024-34913-3. Epub 2024 Sep 12.
Studies on dinoflagellate cysts in the Arabian Sea (AS) are limited to the coastal waters, but no information from the deeper depths. The dinoflagellate cyst assemblages in surface sediment samples (0-2 cm) from the deeper depths (up to ~ 4500 m) of central (oxygen minimum zone (OMZ)) and southeastern (oligotrophic) AS revealed that the relatively good numbers of cyst concentrations reach deeper depths of OMZ (3505 m) and oligotrophic (4368 m) regions, but the former harbored more cyst concentrations than the latter. The cyst concentration and species count (including HAB species) recorded here are lower compared to the eastern (EAS) and western (WAS) AS, but the autotrophic cyst dominance (74-83%) at deeper depths is in contrast with the heterotrophic dominance in coastal AS. Of the recorded 41 cyst species (belonging to 18 genera), four species (cyst of Cladopyxis sp., Operculodinium janduchenei, Stelladinium bifurcatum, and Protoperidinium monospinum) from the deepest part of oligotrophic AS form the first report. In contrast, Spiniferites and Lingulodinium cysts were common occurrences. Taxonomic comparison with literature revealed (i) the prevalence of more cosmopolitan species (32 species) which could be due to the prevalence of large and small-scale lateral transport of cysts in oligotrophic regions followed by OMZ and coastal regions, respectively, and (ii) very few region-specific species, i.e., cyst of Protoperidinium latissimum, Lejeunecysta sabrina, cyst of Protoperidinium denticulatum in EAS and Impagidinium patulum, and I. strialatum, in WAS. Interestingly, variability in the morphometry was evident between the coastal and open oceans in some cosmopolitan cysts, e.g., Operculodinium centrocarpum and Lingulodinium machaerophorum. These findings from the less studied pelagic regions will contribute to the growing knowledge of dinoflagellate cyst distribution patterns and highlight the significance of cyst taxa and morphology as potential ecological indicators for AS.
对阿拉伯海（AS）中甲藻孢囊的研究仅限于沿海水域，但对更深层水域没有任何信息。对来自中央（氧最小区（OMZ）和东南（贫营养）AS）更深层（高达~4500 米）的表层沉积物样品（0-2 厘米）中的甲藻孢囊组合的研究表明，相对较多的孢囊浓度可到达 OMZ（3505 米）和贫营养区（4368 米）的更深层，但前者的孢囊浓度高于后者。与东部（EAS）和西部（WAS）AS 相比，这里记录的孢囊浓度和种数（包括赤潮种）较低，但在更深的地方，自养孢囊的优势（74-83%）与沿海 AS 中的异养优势形成对比。在记录的 41 种孢囊（属于 18 属）中，有 4 种（Cladopyxis sp.、Operculodinium janduchenei、Stelladinium bifurcatum 和 Protoperidinium monospinum）来自贫营养区的最深处，这是首次报道。相比之下，Spiniferites 和 Lingulodinium 孢囊是常见的。与文献的分类学比较表明，（i）更多的世界性物种（32 种）较为普遍，这可能是由于贫营养区以及随后的 OMZ 和沿海水域中孢囊的大尺度和小尺度侧向输运所致，（ii）非常少的区域特异性物种，即 EAS 中的 Protoperidinium latissimum、Lejeunecysta sabrina、Protoperidinium denticulatum 的孢囊以及 WAS 中的 Impagidinium patulum 和 I. strialatum。有趣的是，在一些世界性的孢囊中，沿海和开阔海域之间的形态变化明显，例如 Operculodinium centrocarpum 和 Lingulodinium machaerophorum。这些来自研究较少的远洋区域的发现将有助于增加对甲藻孢囊分布模式的认识，并强调了孢囊分类群和形态作为 AS 潜在生态指标的重要性。
