First Atlantic record of the green alga Parvocaulis exiguus from St. Eustatius, Dutch Caribbean

The Polyphysaceae is a well-studied family of green algae occurring in tropical and warm-temperate regions around the world. One of its species, Parvocaulis exiguus (Solms-Laubach) S. Berger et al. (Phycologia 42: 506-561, 2003), has previously been reported from both the Indian and the Pacific Oceans. This report presents the first record of Parvocaulis exiguus from the Atlantic Ocean. It was collected at 18 m depth from rocky substrata surrounded by seagrass off the Dutch Windward Caribbean island St. Eustatius. Owing to its small size and close resemblance to co-occurring species, it is possible that this species has been previously overlooked in the Atlantic. Although Polyphysaceae have been intensively studied in the Caribbean and other Atlantic regions, this is not the case for subtidal algal vegetation on St. Eustatius. Parvocaulis exiguus could have been present for a longer time around St. Eustatius or it could have been introduced with shipping. Future investigations may show if Parvocaulis exiguus will be observed in additional locations in the Caribbean

Beta diversity of macroalgal communities around St. Eustatius, Dutch Caribbean

This study provides a baseline of the marine algal flora composition around St. Eustatius, Dutch Caribbean, by describing algal community structure in terms of species richness and beta diversity, and by providing a taxonomically reliable DNA barcode collection. A total of 156 species was found, including 91 that represent new records for St. Eustatius. Subtidal assemblages (126 species) and intertidal assemblages (48 species) showed little overlap. Algae assemblages in seagrass beds differed from those on hard substrates in species composition. In addition, seagrass communities contained a relatively high number of associated green algae species. Artificial substrates (such as shipwrecks) mimicked natural hard substrates in terms of species richness and composition, but missed some key species that characterize natural reef floras. Species accumulation curves and asymptotic species richness estimators show that the expected species richness is higher than the observed number of species, indicating that additional sampling is needed to record rare species. The phylogenetic trees provided in this study identified the presence of cryptic species and fills knowledge gaps in our understanding of Caribbean macroalgae

Arctic rhodolith beds and their environmental controls (Spitsbergen, Norway)

Coralline algae (Corallinales, Rhodophyta) that form rhodoliths are important ecosystem engineers and carbonate producers in many polar coastal habitats. This study deals with rhodolith communities from Floskjeret (78°18′N), Krossfjorden (79°08′N), and Mosselbukta (79°53′N), off Spitsbergen Island, Svalbard Archipelago, Norway. Strong seasonal variations in temperature, salinity, light regime, sea-ice coverage, and turbidity characterize these localities. The coralline algal flora consists of Lithothamnion glaciale and Phymatolithon tenue. Well-developed rhodoliths were recorded between 27 and 47 m water depth, while coralline algal encrustations on lithoclastic cobbles were detected down to 77 m water depth. At all sites, ambient waters were saturated with respect to both aragonite and calcite, and the rhodolith beds were located predominately at dysphotic water depths. The rhodolith-associated macrobenthic fauna included grazing organisms such as chitons and echinoids. With decreasing water depth, the rhodolith pavements were regularly overgrown by non-calcareous Polysiphonia-like red algae. The corallines are thriving and are highly specialized in their adaptations to the physical environment as well as in their interaction with the associated benthic fauna, which is similar to other polar rhodolith communities. The marine environment of Spitsbergen is already affected by a climate-driven ecological regime shift and will lead to an increased borealization in the near future, with presently unpredictable consequences for coralline red algal communities