Oceanic islands are natural laboratories for investigating species diversity and richness patterns. Changes in abiotic parameters may induce shifts in marine biota. Seaweeds are recognized as bioindicators, though those from remote tropical islands have been rarely studied. This study updates the diversity, richness and distribution of macroalgae from Trindade, a Brazilian volcanic island located 1140 km off the coast. Biotic data, obtained in a global database and in situ and compiled in a new records list, were associated with abiotic parameters. Conservation and ecological issues were discussed in the context of the observed greater richness, expansion of the distributional range and low endemism. A total of 141 species were identified, including 60 new records and 20 taxa of filamentous cyanobacteria. The greater richness, including potential cryptogenic species, may primarily be associated with past incomplete samplings, current new techniques and combined taxonomical methods, including molecular analysis for cryptic species. However, on the macroscale, this study provides information for the re-evaluation of aspects of endemism, connections and biogeographical distribution shifts of seaweed as­semblages, considering environmental changes. In addition, this updated checklist establishes a baseline for further compara­tive studies, reinforcing the hypothesis that biogeographical isolation can be disrupted by meteorological and oceanographic shifts, altering dispersal patterns and resulting in higher ecosystems connectivity.

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Despite therapeutic advances in recent decades, colorectal cancer is still the third most frequent neoplasm worldwide, with significant morbidity and mortality in young and middle-aged adults. Therefore, advance in treatment options for patients who are afflicted with tumor subtypes without effective therapies is needed. Antarctica macroalgae are substances-producing organisms with important biological activities, in which antitumor properties are investigated, showing promising cytotoxic results. There are no reports so far showing antitumor activity of macroalgae Palmaria decipiens extracts against colorectal tumors. This study aims to evaluate the effect of macroalgae P. decipiens extract from Antarctic on tumor cell HCT-116 and non-tumor cell HaCaT lines. The phenolic compounds present were identified by high performance liquid chromatography. The antioxidant activity of the extracts was determined by the DPPH radical inhibition method and cytotoxicity was evaluated through MTT assay. Cell death events were identified using dual staining with acridine orange/ethidium bromide and flow cytometry. The quantification of phenolic compounds present in the extracts identified the presence of three main compounds among them is kaempferol. The metanolic extract showed inhibition within 72 h of treatment in HCT-116 and potential antioxidant activity. The results presented in this study point out an im-How to cite this paper: Giustina, M.D.,

This study provides new species records (NRs) of macroalgal assemblages present in rocky habitats from the South Shetland Islands (SSI) and north-eastern Antarctic Peninsula (EAP), Weddell Sea. Surveys were conducted during the summers of 2013/2014 to 2017/2018 at Elephant, Deception, Half Moon and Vega islands. Data from the present study and those available in the literature from the western Antarctic Peninsula (WAP) were combined to provide an updated checklist, giving insights into macroecology and potential changes in thermohaline circulation patterns. A total of 48 macroalgal taxa were identified from our sampling, with eight representing NRs to the EAP sector of the Weddell Sea and five representing NRs to the SSI. Statistical differences among the assemblages from the SSI, WAP and EAP were identified. NRs, including opportunistic species and new information about the biogeographical distributions of species reported here, give insights into ecoregional connectivity and environmental changes. This study updates macroalgal diversity records in regions that are currently experiencing the impacts of climate change. Future and ongoing monitoring for conservation purposes is required to detect non-native species, new dispersal pathways and patterns related to thermohaline anomalies in Antarctic waters.