Climate Mitigation through Biological Conservation: Extensive and Valuable Blue Carbon Natural Capital in Tristan da Cunha’s Giant Marine Protected Zone

Carbon-rich habitats can provide powerful climate mitigation if meaningful protection is put in place. We attempted to quantify this around the Tristan da Cunha archipelago Marine Protected Area. Its shallows (<1000 m depth) are varied and productive. The 5.4 km2 of kelp stores ~60 tonnes of carbon (tC) and may export ~240 tC into surrounding depths. In deep-waters we analysed seabed data collected from three research cruises, including seabed mapping, camera imagery, seabed oceanography and benthic samples from mini-Agassiz trawl. Rich biological assemblages on seamounts significantly differed to the islands and carbon storage had complex drivers. We estimate ~2.3 million tC are stored in benthic biodiversity of waters <1000 m, which includes >0.22 million tC that can be sequestered (the proportion of the carbon captured that is expected to become buried in sediment or locked away in skeletal tissue for at least 100 years). Much of this carbon is captured by cold-water coral reefs as a mixture of inorganic (largely calcium carbonate) and organic compounds. As part of its 2020 Marine Protection Strategy, these deep-water reef systems are now protected by a full bottom-trawling ban throughout Tristan da Cunha and representative no take areas on its seamounts. This small United Kingdom Overseas Territory’s reef systems represent approximately 0.8 Mt CO2 equivalent sequestered carbon; valued at >£24 Million GBP (at the UN shadow price of carbon). Annual productivity of this protected standing stock generates an estimated £3 million worth of sequestered carbon a year, making it an unrecognized and potentially major component of the economy of small island nations like Tristan da Cunha. Conservation of near intact habitats are expected to provide strong climate and biodiversity returns, which are exemplified by this MPA.

Benthic Assemblage Composition of South Atlantic Seamounts

Seamounts and oceanic islands rise from the seafloor and provide suitable habitat for a diverse range of biological assemblages including Vulnerable Marine Ecosystems (VMEs). Whilst they have been the focus of some work globally, there has been little description of the biological and physical environments of seamounts in the South Atlantic Ocean. In this study, we characterized benthic assemblage composition from 13 seamounts and oceanic islands spanning 8–40°S within the exclusive economic zones (EEZs) of Ascension Island, Saint Helena and Tristan da Cunha. Drop camera imagery was collected between 170 and 1000 m. All fauna present in images were identified and quantified, and multivariate statistics were used to describe biological assemblages and identify their environmental drivers. Benthic communities of temperate regions (Tristan da Cunha archipelago) were shown to be distinct from those found in the tropics, with latitude and depth identified as key environmental drivers of assemblage composition. Our results are consistent with the current understanding of the biogeography of the South Atlantic, both in terms of the distinction between tropical and temperate regions, and the influence of depth and water mass structure on assemblage distribution. Faunal assemblages are similar to those observed in the North Atlantic in terms of functional groups. VMEs are present within the EEZs of all three territories and are potentially protected from some threats by large marine protected areas (MPAs). Our imagery, data and analyses provide a baseline for south Atlantic seamounts so that future monitoring can establish whether existing protected status is sufficient to conserve both unique biodiversity and considerable potential for vital ecosystem services.

Breeding biology of two sympatric Nesospiza finches at Nightingale Island, Tristan da Cunha

Nesospiza finches are a classic example of a simple adaptive radiation, with two ecologically distinct forms confined to the Tristan da Cunha Archipelago, South Atlantic Ocean: an abundant, small-billed dietary generalist, and a scarce, large-billed specialist. These have segregated into two species at Nightingale Island, but there is still local introgression between the two forms at Inaccessible Island. We describe the phenology and breeding behaviour of the two sympatric species at Nightingale Island (2.6 km2): Wilkins’s Finch Nesospiza wilkinsi (Endangered) and Nightingale Island Finch N. questi (Vulnerable). The finch breeding season starts in late October-November but the onset of breeding varies by 4–5 weeks among years. The small-billed Nightingale Island Finch typically (two of three study seasons) starts breeding 1–3 weeks earlier than the large-billed Wilkins’s Finch, unlike at Inaccessible Island where the Wilkins’s Finches start breeding first. Laying of initial clutches was quite well synchronised, peaking 1–2 weeks after the first nests were found. Females constructed the nests, which were mostly (>90%) in dense Spartina arundinacea tussock grass stands and occasionally in ferns or sedge grasses. Clutches comprised one or two eggs, with no difference between Wilkins’s (1.66 ± 0.48) or Nightingale Island finch clutches (1.71 ± 0.46). Incubation periods averaged longer for Wilkins’s Finch (18.3 ± 0.5 d) than Nightingale Island Finch (17.7 ± 0.5 d), but this difference was not statistically significant. Females incubated the eggs, and were fed by the males. The difference in egg volume within two-egg clutches was 2–13% for Wilkins’s Finches (mean 5.9 ± 3.3%) and 1–19% for Nightingale Island Finches (mean 8.4 ± 5.3%). At least 31% of pairs re -laid after their first breeding attempt failed but there was no evidence of double brooding. Repeat nests were 0–20 m (mean 5.6 ± 4.9 m) from the initial nest site and inter-seasonal nest sites for 38 known pairs were 0–33 m apart (mean 12 ± 9 m). No inter-species pairs or hybrid birds were seen, but two instances of inter-species fledgling provisioning were observed.

Diet of the introduced Gough Moorhen Gallinula comeri on Tristan da Cunha

Gough Moorhens Gallinula comeri were introduced to Tristan da Cunha in the 1950s, and are now numerous in lowland habitat, filling the ecological niche of the extinct Tristan Moorhen G. nesiotis. On their native Gough Island, moorhens have a varied diet, ranging from vegetation and fruits to scavenging and even predatory behaviour. Here, we examined the stomach contents of four birds on Tristan da Cunha to provide insight into their diet. Moorhens mostly ate vegetation, but we also recorded spiders (Arthropoda: Aranea), earthworms (Oligochaeta: Lumbricidae), remains of introduced rodents (Mus musculus), and anthropogenic debris. As on Gough Island, moorhens on Tristan have a generalist diet, and the impact of ecosystem restoration (and of the moorhens themselves) should be considered.

English in Madeira: History and features of a lesser-known variety in the Atlantic

‘Lesser-known varieties of English’ (Schreier, 2009; Schreier et al., 2010) have received increasing attention in the last decade. In particular, Englishes on islands with historical and political ties to the United Kingdom or the United States have been described, such as the varieties in Bermuda (Eberle, 2021), Samoa (Biewer, 2020), and Tristan da Cunha (Schreier, 2009). However, Madeira has hitherto received extraordinarily little attention, although it used to be home to a small but enormously influential group of British expatriates who controlled large parts of the economy and owned a considerable amount of land on the island. Even today, approximately 1,000 emigrants from the United Kingdom live permanently in Madeira, which constitutes the second largest group of foreign residents (DREM, 2020b: 11). ‘Madeira’ refers to both a Portuguese archipelago and this archipelago's main island located ca. 737 km west of Morocco's coast (see Figure 1). Overall, Madeira had a population of 267,785 in the last official census from 2011 and is a highly popular tourist destination, with roughly 8 million overnight stays by visitors in 2019 (DREM, 2020a).

Some free-living laelapid mites (Acari: Mesostigmata: Laelapidae) from Tristan da Cunha and Nightingale Islands, with description of a new species of Gaeolaelaps Evans & Till (Acari: Laelapidae) and the first afrotropical record of the genus Nidilaelaps Shaw

This paper reports on four species of free-living mites of the family Laelapidae from Tristan da Cunha and Nightingale Islands: Cosmolaelaps claviger (Berlese), Gaeolaelaps aculeifer (Canestrini), G. furcatus sp. nov., and Nidilaelaps annectans (Womersley). The new species has the unique character states of the paradactyli on pretarsi II–IV being very elongated and the pulvillar lobe well developed in shape of a fork on ambulacra II–IV. The genus Nidilaelaps Shaw is here reported for the first time from Afrotropical realm.

Cetaceans Sightings During Research Cruises in Three Remote Atlantic British Overseas Territories

Marine mammal sightings were recorded during research cruises to three remote, mid-ocean British Overseas Territories in the South Atlantic and Southern Ocean. In March to April 2018 and 2019, the Exclusive Economic Zones (EEZs) of tropical St Helena and temperate Tristan da Cunha were surveyed. The sub-polar waters of South Georgia and the South Sandwich Islands (SGSSI) were surveyed in February to March 2019. At St Helena in 2018, five species were recorded during 11 sightings, and in 2019, four species, with one additional unidentified species, during seven sightings. Most of these sightings were of dolphin species, which are known to be resident around the Island and seamounts. In Tristan da Cunha in 2018, a total of five identified and one unidentified species were recorded during six sightings, half of which were associated with the Islands or seamounts. In 2019, due to rough weather, no sightings were recorded in the Tristan da Cunha waters. Around SGSSI, 162 sightings of 236 cetaceans were made in 2019, mostly of baleen whales, with seven species identified with certainty. Sightings around the southern South Sandwich Islands included beaked whales and large dolphins, whereas baleen whales dominated in the northern South Sandwich Islands. These results provide new data for rarely surveyed regions, helping to build a spatial picture of important areas for marine mammals, which will help inform marine spatial protection strategies.