Marine algal (seaweed) flora of Graciosa Island, Azores

Background
The macroalgal flora of Graciosa (central group of Azores archipelago) is poorly known, the published information reflecting occasional collections from sporadic field visits to the island. To overcome this, a thorough investigation under the Expedition “GRACIOSA/2004”, the Campaigns “PADEL/2006”, “MACROBIOLMOL/2014” and “PIMA-BALA/2017” involving sample collecting and presence data recording, was undertaken over an area of 19 km2 encompassing littoral and sublittoral levels down to about 40 m. This paper lists the taxonomic records and provides information on species ecology and occurrence around the island improving the knowledge of the Azorean macroalgal flora at both local and regional scales.
New information
A total of 1692 specimens belonging to 250 taxa of macroalgae (and including 55 taxa identified only at the genus level) are registered, comprising 166 Rhodophyta, 36 Chlorophyta and 48 Ochrophyta (Phaeophyceae). From these, 195 are identified to the species level (126 Rhodophyta, 31 Chlorophyta and 38 Ochrophyta) and comprise 156 native, 20 of uncertain origin and 14 introductions to the island. Predaea feldmannii subsp. azorica Gabriel is an Azorean endemic, whereas Codium elisabethiae O.C. Schmidt, Botryocladia macaronesica Afonso-Carrillo, Sobrino, Tittley & Neto, Phyllophora gelidioides P.Crouan & H.Crouan ex Karsakoff and Laurencia viridis Gil-Rodríguez & Haroun represent Macaronesian endemics. Seventy-nine species are newly recorded to the island.
Introduction
Around 400 species have been recorded in the isolated mid-Atlantic Azores archipelago so far (Freitas et al. 2019). When compared to that of other remote oceanic islands (e.g. the Shetlands and Faroes in the colder North Atlantic, and Ascension and Tristan da Cunha in the Southern Atlantic), the algal flora of the Azores can be considered relatively rich (Tittley 2003, Neto et al. 2005; Tittley & Neto 2005; Tittley & Neto 2006, Wallenstein et al. 2009). It is a cosmopolitan flora with species shared with Macaronesia, North Africa, the Mediterranean Sea, Atlantic Europe and America. Overall, it shares more species with the east Atlantic flora than with the west (Tittley & Neto 2006, Wallenstein et al. 2009).
Although São Miguel has been thoroughly investigated, most of the Azorean islands have received little attention, there algal flora being scarcely studied. To overcome this, and improve the understanding of the archipelago’s seaweed flora, research has been conducted over the past three decades. This paper presents both physical and occurrence data, and information gathered from macroalgae surveys undertaken on Graciosa (central group of the archipelago) by the Island Aquatic Research Group of the Azorean Biodiversity Centre of the University of the Azores (https://ce3c.ciencias.ulisboa.pt/sub-team/island-aquatic-ecology) the MARBE, Marine Biodiversity and Environment Research Group of CIBIO-Açores at the University of the Azores (http://cibio.uac.pt/en/research-groups/marbe-marine-biodiversity-and-environment), and the OKEANOS Centre of the University of the Azores (www.okeanos.uac.pt). In these surveys particular attention was given to the small filamentous and thin sheet like forms that are often short-lived and fast-growing species, very difficult to identify in the wild, requiring the aid of a microscope.
The paper aims to provide a practical resource for biological studies, such as systematics, diversity and conservation, biological monitoring, climate change and ecology, and also for academics, students, government, private organizations, and the general public.
Purpose
In this contribution we list taxonomic records for Graciosa and present general information for the occurrence of each taxon around the island. By doing this, we are contributing to address several biodiversity shortfalls (see Hortal et al. 2015), namely the need to catalogue the Azorean macroalgae (Linnean shortfall) and improve the current information on their local and regional geographic distribution (Wallacean shortfall), as well as on species abundances and dynamics in space (Prestonian shortfall).

研究背景
格拉西奥萨岛（Graciosa，亚速尔群岛中部岛群）的大型藻类区系（macroalgal flora）研究程度极低，已发表的相关信息仅来自对该岛零星野外考察所获得的偶发采集样本。为填补这一研究空白，依托"GRACIOSA/2004"考察航次、"PADEL/2006"、"MACROBIOLMOL/2014"及"PIMA-BALA/2017"调查项目开展了全面调查：研究区域覆盖19平方千米，涵盖潮间带至约40米水深的潮下带区域，内容包括样本采集与物种出现数据记录。本文整理了该岛的分类学记录，并提供各物种的生态特征与分布情况相关信息，旨在提升亚速尔群岛大型藻类区系在局地与区域尺度上的认知水平。

新报道数据
本次研究共登记1692份大型藻类标本，隶属于250个分类单元（taxon，复数taxa，其中55个仅鉴定至属级），包括红藻门（Rhodophyta）166种、绿藻门（Chlorophyta）36种以及不等鞭毛藻门（Ochrophyta，褐藻纲Phaeophyceae）48种。其中195个分类单元鉴定至物种级：红藻门126种、绿藻门31种、不等鞭毛藻门38种，包含156个本土物种、20个起源未定物种以及14个外来引入物种。其中*Predaea feldmannii subsp. azorica Gabriel*为亚速尔群岛特有亚种；*Codium elisabethiae O.C. Schmidt*、*Botryocladia macaronesica Afonso-Carrillo, Sobrino, Tittley & Neto*、*Phyllophora gelidioides P.Crouan & H.Crouan ex Karsakoff*以及*Laurencia viridis Gil-Rodríguez & Haroun*为马卡罗尼西亚（Macaronesia）特有种。另有79个物种为该岛首次记录。

引言
截至目前，这片地处大西洋中部的偏远群岛——亚速尔群岛（Azores Archipelago）已记录到约400种大型藻类（Freitas等，2019）。相较于其他偏远海洋岛屿（如北大西洋寒冷海域的设得兰群岛与法罗群岛，南大西洋的阿森松岛与特里斯坦-达库尼亚群岛），亚速尔群岛的大型藻类区系相对丰富（Tittley，2003；Neto等，2005；Tittley & Neto，2005、2006；Wallenstein等，2009）。该群岛的藻类区系属于广布型区系，与马卡罗尼西亚、北非、地中海、大西洋沿岸欧洲及美洲共享大量物种。整体而言，其与大西洋东部藻类区系的物种重合度高于西部（Tittley & Neto，2006；Wallenstein等，2009）。
尽管圣米格尔岛（São Miguel）已得到全面调查，但亚速尔群岛的多数岛屿仍未受到足够关注，其藻类区系研究程度极低。为填补这一研究空白、加深对该群岛海藻区系的认知，过去三十年间学界开展了多项相关研究。本文整理了针对格拉西奥萨岛（该群岛中部岛屿）的大型藻类调查所获得的物理环境数据、物种出现数据及相关信息，相关调查由亚速尔大学亚速尔生物多样性中心岛屿水生研究组（https://ce3c.ciencias.ulisboa.pt/sub-team/island-aquatic-ecology）、亚速尔大学CIBIO-Açores的MARBE海洋生物多样性与环境研究组（http://cibio.uac.pt/en/research-groups/marbe-marine-biodiversity-and-environment）以及亚速尔大学OKEANOS中心（www.okeanos.uac.pt）共同完成。本次调查特别关注了小型丝状与薄片状藻类：这类物种通常寿命短、生长速度快，野外难以直接鉴定，需借助显微镜辅助。
本文旨在为分类学、物种多样性与保护、生物监测、气候变化及生态学等生物学研究提供实用参考资源，同时面向科研人员、学生、政府机构、民间组织及普通公众。

研究目的
本研究整理了格拉西奥萨岛的大型藻类分类学记录，并介绍各分类单元在该岛周边的分布概况。通过此项工作，我们旨在填补多项生物多样性研究缺口（Hortal等，2015）：即完善亚速尔群岛大型藻类的编目工作（林奈缺口（Linnean shortfall））、提升其局地与区域地理分布的现有数据水平（华莱士缺口（Wallacean shortfall）），以及补充物种空间丰度与动态相关数据（普雷斯顿缺口（Prestonian shortfall））。