Outbreak of Cholera in Angola.

Angola has been suffering a severe Cholera outbreak, with the first cases reported in January 2025, with 8543 reported cases and 329 fatalities, 112 occurred in the community, by 23 March, according to a press release issued by the World Health Organization. From the outset of the outbreak, the number of cases rose steadily until the first week of February, when over 1000  cases were reported in a single week. The number of cases then fell slightly, plateauing at slightly over 800 cases a week through most of February and March, before starting to rise again at the end of March.

Number of Cholera cases by epidemiological week of reporting, as of 23 March 2025. World Health Organization.

Younger people have been particularly badly hit by the outbreak, with 1976 reported cases (23.1% of the total) among 6-14-year-olds, 1850 cases (21.7% of the total) among 15-24-year-olds, and 1475 cases (17.3%) of cases among 25-34 year-olds. Males have been slightly more affected than females, making up 55.3% of the total (4725 cases). Cases have been reported in 16 of Angola's 21 provinces, with the worst affected provinces being Luanda, with 4143 cases (48.5% of the total) and Bengo, with 2485 cases (29.1% of the total).

Map of Cholera cases by province, as of 23 March 2025. World Health Organization.

Cholera is an acute enteric infection caused by ingesting the Bacterium Vibrio cholerae a Gram-negative, comma-shaped Gammaproteobacterium, related to other pathogenic Bacteria such as Yersinia pestis (Bubonic Plague), and Esherchia coli (food poisoning), which present in contaminated water or food. It is mainly linked to insufficient access to safe drinking water and inadequate sanitation. Cholera is an extremely virulent disease that can cause severe acute watery diarrhoea resulting in high morbidity and mortality, and can spread rapidly, depending on the frequency of exposure, the exposed population and the setting. Cholera affects both children and adults and can be fatal if untreated.

Scanning electron microscope image of Vibrio cholerae Bacteria. Kim et al. (2000).

The incubation period is between 12 hours and five days after ingestion of contaminated food or water. Most people infected with Vibrio cholerae do not develop any symptoms, although the bacteria are present in their faeces for 1-10 days after infection and are shed back into the environment, potentially infecting other people. The majority of people who develop symptoms have mild or moderate symptoms, while a minority develop acute watery diarrhoea and vomiting with severe dehydration. Cholera is an easily treatable disease. Most people can be treated successfully through prompt administration of oral rehydration solution.

The consequences of a Humanitarian crisis, such as disruption of water and sanitation systems, or the displacement of populations towards inadequate and overcrowded camps, can increase the risk of Cholera transmission, should the Bacteria be present or introduced. A multisectoral approach including a combination of surveillance, water, sanitation and hygiene, social mobilization, treatment, and oral Cholera vaccines is essential to control Cholera outbreaks and to reduce deaths.

Angola has suffered recurrent Cholera outbreaks since the 1970s, with a major outbreak in 1987 which infected around 16 000 people were infected and 1460 people died. Outbreaks were recorded every year from 1987 till 1996, after which the disease disappeared for a decade. Cholera returned in 2006, with another major outbreak in which around 67 000 people were infected and 2700 people died. Subsequent outbreaks were recorded in 2011-13 and 2016-18. Cholera infections generally peak in the rainy season (mid-October to mid-April), and outbreaks in Angola are often linked to outbreaks in the neighbouring Democratic Republic of Congo.

See also...

Sesamothamnus leistneri: A new species of Sesame Tree fromthe Kaokoveld Region of Namibia and Angola.

The Sesame Family, Pedaliaceae, contains eleven genera of shrubs and trees, including the True Sesames, Sesamum spp.. Eight of these genera are confined to Africa, where the family is thought to have originated, while one, Uncarina spp., if found only on Madagascar. Of the remaining two genera, Pedalium (which contains only a single species, Pedalium murex) is found across much of Africa and South and Southeast Asia as far east as Java, while Sesamum spp. has a near global distribution, although it is likely to have been introduced to many places by Humans, due to the use of its seeds as a food crop.

Phylogenetic studies of the Family Pedaliaceae have suggested that the basalmost genera is Sesamothamnus, the Sesame Trees or Sesame Bushes, a group found in arid areas of Africa, split into two groups with a bimodal distribution. The first group of species is found in East Africa, from Ethiopia and Somalia south into Kenya and Tanzania, and are large, tree forming plants, the second group has a Southern African distribution, being found in Angola, Namibia, Botswana, Zambia and Zimbabwe, and are smaller, shrubby plants, with a bulbus base from which a single, taperinc stem arises.

The most recent species of Sesamothamnus to have been described was Sesamothamnus lugardii in 1906, however, in 1957 the South African botanists Bernard de Winter and Otto Albrecht Leistner recorded seeing a tree-like species of Sesamothamnus while on an expedition to the Kaokoveld Region of northwestern Namibia, and in addition brought back sterile samples which were stored in the collections of the South African National Biodiversity Institute in Pretoria and the National Botanical Research Institute in Namibia, where they were tentatively identified as Sesamothamnus benguellensis, a shrub-like form found in Namibia and Angola. In 1966 the Namibian botanist Heinrich Johann Wilhelm (Willy) Giess collected fertile specimens of the tree, which were stored in the National Botanical Research Institute in Namibia under the name 'Sesamothamnus leistneranus' apparently in honour of Otto Albrecht Leistner, although he never published a description of this material.

In a paper published in the journal Phytotaxa on 14 November 2023, Wessel Swanepoel, an independent researcher from Windhoek and Abraham van Wyk, from the H.G.W.J. Schweickerdt Herbarium at the University of Pretoria, formally describe the Kaokoveld Sesame Tree as a new species.

The species is described as Sesamothamnus leistneri, rather than Sesamothamnus leistneranus, as this implies that it was discovered by Leistner, rather than simply named in his honour. Wessel Swanepoel and first observed an unfamiliar Sesame Tree while visiting the Kaokoveld in 1990, although at that time the tree was not in flower or fruit, making identification very hard. In 2005 Swanepoel and van Wyk observed another Sesame Tree in the Otjitanda area of the Kaokoveld. This time the tree was producing both flowers and fruit, and samples were taken which enabled it to be compared to the material previously collected by de Winter, Leistner, and Giess.

Sesamothamnus leistneri, habitat and habit. (A) Multi-stemmed tree with distinct browse line caused by domestic stock. (B) & (C) Trees showing typical upright habit and relatively dense green foliage during the rainy season. Swanepoel and van Wyk (2023).

Sesamothamnus leistneri is a single or (more-commonly) multi-trunked succulent tree, reaching about 8 m in height. Branches are formed high on these trunks, and covered with sharp spines up to 30 mm in length, formed from modified petioles (leaf stalks). The bark of the tree is creamy yellow, and peels away from the trunks in papery strips. The trees are deciduous, producing waxy green leaves 40-70 mm in length and 15-40 mm. Flowers are produced from January to June and are large and cylindrical, reaching 150 mm in length and 55 mm in width, white or cream on the outside and bright yellow on the interior. Flowers of this type are likely to be pollenated by Long-tongued Hawkmoths, as is the case with other members of the genus. The fruit, produced from February onwards is a green-to-yellow rigid woody capsule, 65-90 mm in length and 25-32 mm in width, which splits open during the dry season releasing a large number of small, winged seeds.

Sesamothamnus leistneri, habitat and habit. (A) Typical single-stemmed tree. (B) Tree with foliage starting to turn yellow in autumn. (C) Leafless tree during the dry season (winter), with persistent dehisced fruit. Swanepoel & van Wyk (2023).

Sesamothamnus leistneri was found growing in mountainous regions on both sides of the Kunene River, which forms the border between Namibia and Angola. In Namibia it was found from the Ehomba Mountain and Zebra Mountains in the east throughout the Baynes Mountains to the Otjihipa Mountains in the west, and south as far as Sesfontein. In Angola Sesamothamnus leistneri was observed near the summit of Serra Tchamalindi in the Iona National Park, and is thought likely to be fairly widespread.

Sesamothamnus leistneri, vegetative morphology. (A) Single-stemmed tree showing fluted trunk. (B) Bark peeling in papery pieces. (C) Long shoot with leaves clustered on lateral short shoots. (D) Mature leaves showing green colour and glossy upper surface. (E) Long shoot with spines derived from petioles; one dried leaf blade still attached. Swanepoel & van Wyk (2023).

Sesamothamnus leistneri grows on rocky mountain and valley slopes, in kloofs (gorges), less often on plateaus and at the base of hills, in Colophospermum-Commiphora woodland at elevations of 1000–1600 m, Between 83 and 220 km from the Atlantic Ocean. Rainfall in this area is typically 100-300 mm per year. This area is sparsely populated by Humans, and the tree does not appear to be utilised by Humans in any way, though it is browsed by livestock during periods of drought. As such Swanepoel and van Wyk assess that it should be classified as being of Least Concern under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species.

Sesamothamnus leistneri, flower morphology. (A) Inflorescence showing one open flower, several flowers in different stages of development, and persistent styles (whitish, tipping blackish ovaries) of faded flowers following shedding of the corolla. (B) Flowers, open and in bud; note both stamens and stigma positioned in mouth of the corolla tube, also the lack of a spur at the base of the tube. (C) Flower showing style with bilobed stigma exserted about 10 mm from the mouth of the corolla tube. (D) Distal part of corolla tube opened out to show the yellow inner surface of the tube, white filaments, and anthers positioned at the level of the corolla mouth. Swanepoel & van Wyk (2023). 

The tree-like general habit of Sesamothamnus leistneri suggests that it is more closely related to the Sesame Trees of northern East Africa than the shrubby forms of Southern Africa. This is not altogether surprising, as while these areas are now separated by humid tropical forests where these Plants are unlikely to be able to survive, it is thought that the two zones would have been connected by bands of arid land several times during the Pleistocene glacial phases, when the climate of Africa would have been cooler and dryer.

Sesamothamnus leistneri, fruit morphology. (A) Two almost mature fruit and a dehisced one. (B) Old dehisced fruit persist for some time on trees. Swanepoel & van Wyk (2023).

See also...

Follow Sciency Thoughts on Facebook.

Follow Sciency Thoughts on Twitter.

Investigating the origin of a gold-coloured talc bead from the Kongo Kingdom of West-Central Africa.

Personal adornments are considered one of the key cultural traits of Modern Humans, and appear to have been more-or-less ubiquitous in all Human societies for at least the past 40 000 years. Adornments are used to convey information about an individuals social status, beliefs, gender identity, kinship, and affiliations, as well as personal taste, with these symbols typically being recognizable to other members of the society in which they live. Early adornments, in the form of perforated shells presumed to have been strung together as beads, appear in Africa north and south of the Sahara, as well as parts of the Middle East from about 82 000 years ago, with possible earlier use by the Aterian Culture of North Africa as long as 130 000 years ago (claims have been made for beads older than this, although these are not generally accepted anymore).

However, while there is strong evidence for these ancient items having been beads, with examples such as shells from Blombos Cave in South Africa, which show signs both of having sustained wear while hanging on a string, and of having been painted with red ochre, there is a gap in the archaeological record between about 70 000 and 450 0000 years ago, during which no beads are known, followed by a sudden re-appearance of beads, and their spreading to every inhabited landmass by about 40 000 years ago. These later beads are no longer made exclusively of shell, with bone and stone also being used as bead-making materials, and the appearance of pendants as well as simple strings of beads, and evidence that beads were being traded over quite long distances, at least in Southern Africa.

By the middle of first millennium BC, semi-precious stones were being widely used to make beads, and traded over wide areas, with examples having been used to demonstrate trade links between West and East Africa, the Indian Ocean rim, and Europe. However, while these high-status items appear to have been traded over wide areas, many people were still using beads made from local materials, with examples of locally-produced-and-used beads from Africa including the jasper beads known from Niger, a variety of stone and mineral beads from around Lake Turkana, in Kenya, and the stone beads of Njoro River Cave, also in Kenya.

Talc, talc-schist, soapstone, and steatite, are soft rocks easily carved into beads or other items, found widely in sub-Saharan Africa. Despite this, beads made from these materials are somewhat unusual on the continent. Talc is the softest of these minerals, and with a rating of 1 on the Mohs scale, is generally rated the softest mineral of any kind. It is variable in colour, ranging from white to green, depending on the nature and position of the metal ions within its crystal structure. Furthermore, while it's softness makes it easy to carve, it can be hardened by heating, reaching 3-5 on on the Mohs scale when heated to above 800°C and as much as 7 (equivalent to quartz) when heated to above 1000°C.

Talk which had apparently been collected with the intention of manufacturing something has been recovered from the Iron Age Thaba ya Batswana archaeological site, a stone walled enclosure to the south of Johannesburg, thought to date to about 1700 AD. Talk and soapstone were also utilized by early herders in East Africa to make beads and pendants. Away from Africa, soapstone items were widely used to make personal adornments in the Near East during the Neolithic, with items known from sites such as Çatalhöyük in Turkey, and Abu Hureyra, Tell Aswad, Dja’de el-Mughara, and Tell Halula, all in Syria, as well as sites in Israel, as well as and several Upper Palaeolithic Aurignacian sites from France, several sites associated with the Indus Valley Civilization in northern India, dated to between the 5th and 2nd millennia BC, the 10 000-year-old Arch Lake human burial site in New Mexico, and 15-16th century AD sites in eastern North America.

In a paper published in the journal Archaeological and Anthropological Sciences on 7 February 2023, Mafalda Costa of the HERCULES Laboratory at the University of Évora, and the Archaeometry Research Group at Ghent University, Pedro Barrulas, also of the HERCULES Laboratory at the University of Évora, Maria da Conceição Lopes of the Research Center in Archaeology and the Department of History, Archaeology and Arts at the University of Coimbra, João Barreira, also of the Research Center in Archaeology at the University of Coimbra, Maria da Piedade de Jesus of the Angolan Instituto Nacional Do Património Cultural, Sónia da Silva Domingos of the Angolan Centro Nacional de Investigação Científc, Peter Vandenabeele, also of the Archaeometry Research Group, and of the Raman Spectroscopy Research Group, at Ghent University, José Mirão, also of the HERCULES Laboratory, and of the Department of Geosciences at the University of Évora, present the results of a chemical and mineralogical characterization of a broken mustard-gold-colored stone bead excavated from the Lumbu archaeological site within Mbanza Kongo, the pre-colonial capitol of the  Kongo Kingdom, which covered much of what if now northern Angola and the west of the Democratic Republic of Kongo between the thirteenth and nineteenth centuries AD.

The Kongo Kingdom is considered to have been highly socially stratified and centralized society prior to its first contact with Portuguese explorers in 1483. The Portuguese introduced Christianity to the nation, as well as a range of new technologies, and integrated it into a transatlantic trade network. The capital of this kingdom, Mbanza Kongo, was founded in the mid fourteenth century, and is considered to be the oldest continuously occupies settlement in West Central Africa, today being the capital of Zaire Province in northwest Angola. The Lumba archaeological site, uncovered during a three-month archaeological site in 2014, is thought to have either been a royal residence or a ceremonial court. The site comprises a dry-stone building made from irregularly shaped blocks, arranged in an uneven fashion, which led to the walls having considerable variation in thickness. Two radiocarbon dates have been obtained from pieces of charcoal from different parts of the site, these being 1637 and 1950.

The 2014 excavations produced a range of ceramic vessels, including Portuguese-made pottery, fragments of clay pottery, and a total of 53 beads, 52 of which were glass 'trade-beads' of European manufacture, but one, identified as 'Type 44' is a broken mustard-gold-colored bead, made from a softer material, initially thought to be clay. The surviving bead-fragment is about 8.7 mm in width, 9.0 mm long, and has a maximum thickness of 8.9 mm, with a central perforation with a maximum diameter of 5.6 mm. The unbroken end is rounded, possibly by contact with other beads on a string. In form, the bead resembles a monochrome elongate glass bead. It was found in Stratigraphic Unit 6 of area H17 at Lumba, along with several hexagonal blue glass beads made in Bohemia in the nineteenth century, and some blue and green glass beads thought to be of Venetian manufacture.

Stereomicroscope images of Type 44 bead found in Lumbu (Mbanza Kongo, Angola). Costa et al. (2023).

Examination of Type 44 under a stereomicroscope revealed it was made from a fine-grained material, with white, black, and dark brown mineral inclusions. The fine grains were found to be made from platy grains of magnesium silicate with a maximum size of 10 µm, making the substance talc. The mineral inclusions range from 5 to 30 µm in size, and appear to be a mixture of zircons, iron oxides, and iron-titanium oxides. During the examination, the bead was accidentally scratched with a fingernail, suggesting it has a hardness of about 2.5 on the Mohs scale. This could be consistent with a talc bead which has been heat-treated to harden it although mineral inclusions can also harden talc this much.

Trace element, and rare earth element, analysis has been used to distinguish talc-minerals from different environments. Talc which formed in marine environments tend to be more enriched in heavier rare earth elements, and depleted in lighter members of the group, as well as having very low levels of cerium and high levels of lanthanum, while talcs from terrestrial hydrothermal systems tend to be enriched in both heavy and light rare earth elements, but deficient in those in the middle of the range. Talcs from ultramafic environments tend to be enriched in chromium and nickel, which often reach levels around 2000 parts per million, while talcs from carbonate environments tend to be very low in these elements.

Type 44 is enriched in heavy rare earth elements, depleted in cerium, and enriched in lanthanum, suggesting that it is made from talc which was precipitated from seawater. The specimen also has a boron concentration typical of seawater, and very low levels of both chromium and nickel, with suggests it formed in a carbonate-rich marine environment, probably with a small amount of detrital material.

Mbanza Kongo sits on rocks of the 575-550-million-year-old Schisto-Calcaire Subgroup, a sequence of sedimentary rocks including of limestones, dolostones, siltstones, and shales with rare intercalations of sandstones, cherts, and evaporites. Two types of talc have been recovered from this sequence, the Pseudo-Oolithe de Kisantu, in which talk oolites are found within quartz-rich layers within a dolomite, and an authigenic hydrothermal talc, which is found associated with copper and lead-zinc mineralizations.

The talc oolites appear to have been formed diagenetically from the remineralization of magnesium-rich clay, and are quite unlike the material from which Type 44 was made. The low levels of chromium and nickel in the material appear to rule out the hydrothermal talc. The talc-schists of Nigeria can also be ruled out as an origin, as these formed within an ultramafic environment. The pattern of rare earth elements and boron concentration seen in the material from which Type 44 is made could support it having been manufactured from an unknown talc-source within the Schisto-Calcaire Subgroup, although such a talc would be likely to have aluminum and iron oxide levels similar to those of the Pseudo-Oolithe de Kisantu, while these are at much higher levels in the Type 44 than in the oolites. However, the Schisto-Calcaire Subgroup outcrops over a wide area in northern Angola, as well as in the vicinity of the Congo River near Luozi, and near Inkisi and Kisantu within the Democratic Republic of Congo, with much of this area, including the area directly around Mbanza Kongo, being very poorly explored by geologists, making it quite possible that unknown talc-deposits within this sequence. Furthermore, the range of materials used in pottery-making in the Kongo Kingdom suggests that the people of the kingdom had a good understanding of the local geology prior to contact with the Portuguese. and even produced talc-rich pottery in the provinces of Nsundi, Mbata, and Mpemba (which is where Mbanza Kongo is located). Since carved talc objects are known from other African kingdoms which were contemporary with Kongo, and likely to have been in contact with it, such as Esie in southwestern Nigeria and Great Zimbabwe in the southeast of modern Zimbabwe, it is quite likely that the people of Kongo had the geological knowledge to seek, locate, and exploit talc resources.

Although Type 44 is only a single (broken) bead, it represents the first known example of a locally made item apparently used for personal adornment. The bead appears to have been made within the Kongo Kingdom, using a source of material familiar to the people of the kingdom, but lost to modern geologists, although it is (obviously) not possible to say quite where this source was. The bead bears a notable resemblance to the elongated monochrome glass beads made in Europe from the sixteenth century onwards, and known to have been exported to the Kongo Kingdom, where glass-making was not known, and appears to represent local craftsmen responding to an introduced European fashion trend.

See also...

Follow Sciency Thoughts on Facebook.

Follow Sciency Thoughts on Twitter. 

Democratic Republic of Congo to seek compensation after Angolan mine tailings dam poisons rivers.

The Democratic Republic of Congo is to seek compensation for people affected by a major pollution incident in July 2021, in which the breach of a mine tailings dam in Angola led to thousands of people living on the banks of the River Tshikapa being poisoned and at least twelve dying. The dam, at the Catoca Diamond Mine in northern Angola, failed on July 15, dumping the water it contained into the Lova River, a tributary of the Tshikapa, reaching that river on 25 July, and eventually spreading downstream into the Kasaï. The pollution turned the water red, and caused a mass die off of Fish and other aquatic Animals (including Hippos) but authorities in Angola apparently did not warn those in the Democratic Republic of Congo, who were taken unaware when people in communities reliant on the river for Fish and water began to fall ill with diarrhoea and vomiting. An investigation by the Congo Basin Water Resources Research Centre found that about 1.4 million of the roughly 2 million people living along the banks of the Tshikapa and Kasaï rivers had been affected by the incident, with about 4400 being made seriously ill and twelve dying.

 

Immediate effects of pollution disaster from the Tshikapa and Kasaï Rivers in the Democratic Republic of Congo. Congo Basin Water Resources Research Centre (2021).

Now the Democratic Republic of Congo's Environment Minister, Eve Bazaiba, has stated that her government will be brining legal action against the mine's owners, Sociedade Mineira de Catoca, itself a joint operation between the Angolan state diamond company Endiama and Russian mining giant Alrosa. Neither the Sociedade Mineira de Catoca nor the Angloan Government has officially responded to this to date, although the Sociedade Mineira de Catoca has claimed to have donated food baskets to communities affected by the incident. Both Endiama and Alrosa have denied any direct involvement in the mine's management, and have stated that it is up to the management of the Sociedade Mineira de Catoca to resolve these issues.

 

Location of the pollution source in the Tshikapa and Kasai rivers from Angola. Congo Basin Water Resources Research Centre (2021).

Tailings dams are used to store sediment-laden waters from mines; such waters typically contain a high proportion of fine silt and clay particles, which take time to settle out of the water. The resulting water may be fairly clean, or may contain other pollutants (typically acids, either generated by the local geology or used in the mining process), and need further treatment. In some instances, acid is added to such pools in order to dissolve the product, which is then released from the resultant chemical slurry by further treatment.

There have been a number of high-profile incidents with mine tailings dams in recent years. leading to the International Council on Mining and Metals (of which Alrosa is not a member) drawing up a set of standards for operating such dams, although these standards are voluntary, with no legal standing. The International Council on Mining and Metals has reportedly offered assistance to the Sociedade Mineira de Catoca following a number of incidents at the operation, but again has not received a response. 

See also...

Follow Sciency Thoughts on Facebook.

Follow Sciency Thoughts on Twitter.

Lophelia pertusa: Cold-water Corals found living in strongly anoxic conditions off the coast of Angola.

Being ecosystem engineers, framework-forming Scleractinian Cold-water Corals provide habitat for thousands of deep-sea species, revealing equally remarkable levels of biodiversity as found in tropical Coral Reefs. Lophelia pertusa is the dominant reef-forming Cold-water Coral in the Atlantic, and based on its distribution correlated with ocean conditions, upper and lower tolerable limits for basic oceanographic parameters were proposed for this species. Among them, dissolved oxygen concentrations can exert control on its biogeographic distribution. However, lowest dissolved oxygen concentrations inhabited by this species apparently differs between the northeast Atlanatic, where it can tollerate levels as low as about 2 millilitres of oxygen per litre of seawater, and the northwest Atlanatic, where it can tollerate levels as low as about 3.7 millilitres of oxygen per litre of seawater. These observations are corroborated by laboratory experiments, revealing that Lophelia pertusa individuals collected from waters on the the Scottish margin in the northeast Atlantic, where there is a dissolved oxygen concentration of about 6 milligrams per litre of seawater, Atlantic, were unable to maintain normal aerobic functions at dissolved oxygen concentrations of less than 3.2 millilitres per litre of seawater. Moreover, for Lophelia pertusa specimens collected from areas of the Gulf of Mexico with dissolved oxygen concentrations of about 2.8 millilitres per litre of seawater, a 7-day exposure to a dissolved oxygen concentration of 1.5 millilitres per litre of seawater proved fatal. However, discoveries of Lophelia pertusa in the oxygen minimum zones of the subtropical eastern Atlantic have hinted at an even wider tolerance of Lophelia pertusa to low dissolved oxygen concentrations. Nevertheless, the limited capability of Lophelia pertusa to thrive under dissolved oxygen concentrations (artificially) reduced below those of their natural environment questions its ability to cope with the global change-induced ocean deoxygenation expected for the coming century.

In a paper published in the journal Coral Reefs on 6 April 2020, Dierk Hebbeln and Claudia Wienberg of the MARUM Center for Marine Environmental Sciences at the University of Bremen, Wolf-Christian Dullo of the GEOMAR Helmholtz Centre for Ocean Research, André Freiwald of the Marine Research Department at Senckenberg am Meer, Furu Mienis of the NIOZ Royal Netherlands Institute for Sea Research and Utrecht University, Covadonga Orejas of the Centro Oceanogra´fico de Baleares of the Instituto Español de Oceanografía, and Jürgen Titschack, also of the MARUM Center for Marine Environmental Sciences at the University of Bremen, and the Marine Research Department at Senckenberg am Meer, present the discovery of Lophelia pertusa-dominated Cold-water Coral reefs thriving in the hypoxic oxygen minimum zone off Angola in the southeast Atlantic. The regional adaptation of the Angolan Cold-water Corals to such extreme conditions sheds new light on their potential capability to cope with expected future environmental changes in the ocean.

During RV Meteor expedition M122 in January 2016, in situ oceanographic parameters such as dissolved oxygen concentrations and temperature were recorded off Angola. Data were collected during eight dives with the Remotely Operated Vehicle Marum Squid, carried out three benthic lander deployments, and 17 conventional conductivity, temperature, and depth instrument casts. The conductivity, temperature, and depth instrument was additionally equipped with a non-calibrated fluorescence sensor only providing relative values shown as means per water depth averaged from all conductivity, temperature, and depth instrument casts.

Multibeam bathymetry map showing the distribution of coldwater Coral reefs off Angola. Locations of conductivity, temperature, and depth (CTD) casts, benthic lander deployments, and remotely operated vehicle (ROV) dives are indicated. Hebbeln et al. (2020).

Remotely operated vehicle video observations revealed the presence of Cold-water Coral Reefs dominated by Lophelia pertusa, which colonise the slopes and summits of up to 100 m high Coral mounds. While dispersed Cold-water Coral colonies were found in a depth range of 250–500 m, large aggregates of healthy colonies were restricted to 330-470 m water depth. The observation of over 50 cm high colonies clearly evidenced the continuous proliferation of Cold-water Coral off Angola for many years.

Thriving Cold-water Corals observed in the oxygen minimum zone off Angola. (a), (b) Lophelia pertusa reefs in the center of the  oxygen minimum zone (350 m water depth). (c) Transported but alive Lophelia pertusa colony in the lower oxygen minimum zone (500 m depth). (d) Lophelia pertusa colony with many living polyps (439 m depth) (ROV images). Hebbeln et al. (2020).

The available oceanographic data revealed water temperatures of 6.8–14.2°C around the Cold-water Corals at depths of 250–500 m. The corresponding dissolved oxygen concentrations of 0.6-1.5 millilitres per litre of seawater are the lowest ever obtained from waters bathing flourishing Lophelia pertusa colonies.

To gain insight into the seasonal variability of  dissolved oxygen concentrationsoff Angola, as the M122 data only represent an 8.5-day snapshot from January 2016, Hebbeln et al. included further 21  conductivity, temperature, and depth instrumentcasts obtained within the mapped area off Angola between 1995 and 2013. These data, spanning from March to September, almost completely correspond to the M122 data or reveal even lower  dissolved oxygen concentrations. Interestingly, even in this hypoxic environment, most prolific Cold-water Coral Reefs are bound to the center of the Angolan oxygen minimum zone where lowest dissolved oxygen concentrations prevail, which coincide with enhanced water-column fluorescence pointing to an increased availability of relatively fresh organic matter.

Based on field observations in the northwest and northeast Atlantic, the assumed lower limit of Lophelia pertusa’s oxygen tolerance ranges around 2-3.7 millilitres per litre of seawater. This has recently been challenged by very low dissolved oxygen concentrations of 1.1-1.4 millilitres per litre of seawater reported from Cold-water Coral sites off Mauritania, which, however, are associated with only sporadic occurrences of small Lophelia pertusa colonies. The new Angolan data documented for the first time Lophelia pertusa’s ability to develop thriving reefs even under dissolved oxygen concentrations of under 1 milligram per litre of seawater.

In addition, off Angola Lophelia pertusa lives at temperatures of up to 14.2° C, which are among the highest temperatures ever observed for this species. Thus, off Angola, the partly high temperatures could act as a second stressor since respiration rates of Lophelia pertusa increase with increasing temperature. 

Stress induced by low dissolved oxygen concentrations and relatively high temperatures is energetically a challenge for the metabolism of most marine species, but can be compensated by the availability of large quantities of high-quality organic matter. The Angolan and Mauritanian margins belong to highly productive upwelling systems triggering extensive oxygen minimum zones. Also at many other Atlantic reef sites, Lophelia pertusa is most abundant at depth intervals with highest oxygen depletion, most likely linked to highest concentrations of suspended food particles in this layer, which also applies to Angola. Comparing ambient dissolved oxygen concentrations and temperature with site-specific net primary productivity, used as a food supply indicator, for several Atlantic Cold-water Coral sites, it appears plausible that the negative effects of hypoxia and high temperatures on Lophelia pertusa seemingly could be compensated by significantly enhanced food supply.

With respect to Lophelia pertusa preferring regional oxygen minima, ambient dissolved oxygen concentrations cannot provide any information about its capability to also cope with lower dissolved oxygen concentrations. However, some information is provided by the aforementioned laboratory experiments. Lophelia pertusa collected in the northeast Atlantic and the Gulf of Mexico could not withstand dissolved oxygen concentrations of less than 40–50% of the ambient values. Consequently, the range of low dissolved oxygen concentrations tolerable by Lophelia pertusa, also beyond its natural environment, might depend on the conditions the corals are acclimated to, thus pointing to a possible genotypic adaptive capacity of Lophelia pertusa. Thus, although on a global scale the tolerable dissolved oxygen concentration limits for Lophelia pertusa range from less than 1 to more than 6 millilitres per litre of seawater, smaller ranges define these limits on regional scales.

Cold-water Coral Reefs are vulnerable marine ecosystems that are partly protected within marine protected areas. These can safeguard Cold-water Corals from destructive Human impacts (e.g., bottom trawling, hydrocarbon exploration), but offer no sustainable protection against global change-induced threats. In concert with ocean acidification and warming of intermediate waters, eoxygenation is expected to become a major stressor for  Cold-water Corals. However, Lophelia pertusa’s general capacity to thrive under well-oxygenated as well as hypoxic bottom waters reveals a rather high oxygen tolerance, although individual Lophelia pertusa populations appear to have limited adaptive capabilities to cope with reductions of 40–50% of ambient dissolved oxygen values. Consequently, the expected decrease in oxygenation of about 2% along the Atlantic continental margins by 2100 by itself might not exert a serious threat to Lophelia pertusa, except for already hypoxic settings like the Angolan margin. However, palaeotological studies revealed that during the last approximately 20 000 years regional changes in water column structure caused the collapse of Lophelia pertusa dominated ecosystems due to decreasing  dissolved oxygen concentrations. Thus, unlike a small overall decrease in dissolved oxygen concentrations, major regional reductions in dissolved oxygen concentration driven by global change-induced changes in ocean circulation have the potential to eradicate regional Lophelia pertusa populations.

Even if smaller decreases in dissolved oxygen concentration alone might not pose a serious threat to Lophelia pertusa reefs, these have to be considered in concert with other changing environmental parameters that might form additional stressors (e.g. temperature and pH) with largely unknown consequences for the Coral’s biological functions. Moreover, the flux of particulate organic carbon from the surface ocean might decline by about 30% by 2100 along the Atlantic margins, resulting in a lower food supply to the Cold-water Corals and deep-sea organisms in general, thus reducing their capacity to cope with increasing stress.

See also...

Follow Sciency Thoughts on Facebook.

Establishing the current rangers of the Cheetah and African Wild Dog in Angola.

Despite Angola’s high biodiversity, the political unrest during the period 1975-2002 took a heavy toll on its wildlife, which suffered from widespread poaching and bushmeat hunting. Although little is currently known about the status and trend of most Angolan wildlife populations, iconic and threatened species such as the Cheetah, Acinonyx jubatus, and African Wild Dog, Lycaon pictus, are presumed to have suffered drastic declines and range contractions. However, the Angolan government has recently shown signs of political will to improve knowledge of the country’s biodiversity, including for the large carnivore species.

In a paper published in the journal Orynx on 12 February 2020, Pedro Monteroso of the Centro de Investigação em Biodiversidade e Recursos Genéticos at the Universidade do Porto, Filipe Rocha, also of the Centro de Investigação em Biodiversidade e Recursos Genéticos, and of the Departamento de Biologia at the Universidade do Porto,  Stefan van Wyk of the Cuatir Private Reserve, Telmo António and Milcíades Chicomo of the Instituto Superior de Ciências da Educação da Huíla, Selma Kosmas, again of the Centro de Investigação em Biodiversidade e Recursos Genéticos at the Universidade do Porto, and of the Department of Wildlife Management and Ecotourism at the University of Namibia, Fernanda Lages, also of the Instituto Superior de Ciências da Educação da Huíla, Ezequiel Fabiano, also of the Department of Wildlife Management and Ecotourism at the University of Namibia, and Raquel Godhino, once again of the Centro de Investigação em Biodiversidade e Recursos Genéticos, and of the Departamento de Biologia at the Universidade do Porto, and of the Department of Zoology at the University of Johannesburg, present the results of a study which used camera traps to assess the status of these two species in two areas of southern Angola.

Globally, the African Wild Dog and Cheetah are categorized as Endangered and Vulnerable, respectively, on the  International Union for the Conservation of Nature's Red List of Threatened Species because of population declines, range loss and the fragmentation of populations. Although historical records indicate that both species formerly occurred widely in Angola, the majority of the country is currently classified as unknown range for both species. Updated knowledge about the distribution, abundance and population dynamics of both species, and any threats, is required for conservation planning.

Group of African Wild Dogs, Lycaon pictus, detected through direct observation, in June 2018.  Milcíades Chicomo/Orynx.

Under the scope of ongoing institutional research and advanced training programmes, Monterosa et al. surveyed around 360 km² in Bicuar National Park, which lies in the transition between the Angolan Miombo Woodlands and Zambezian Baikiaea Woodlands ecoregions in the province of Huíla, and abou  300 km² in Cuatir Private Reserve in western Cuando Cubango province, along the Cuatir river, one of the main tributaries of the Cubango (Okavango) river on its Angolan side, also in the Zambezian Baikiaea Woodlands ecoregion. 

Monterosa et al. deployed camera-trapping stations uniformly spaced at about 2 km in the core of each study area). Fifty-one camera traps were deployed in Bicuar National Park during July 2017–June 2018 and 43 traps in Cuatir Private Reserve during June–December 2018. Cameras were inspected every 2 months. Additional records were obtained in Cuatir Private Reserve from unstructured surveys with six camera traps during August 2013–December 2018. Additional recent records of the Cheetah and African Wild Dog in Angola were obtained by reviewing surveys reports and the Global Biodiversity Information Facility database. Monterosa et al. considered as independent any camera-trapping detections within 30 minutes, unless animals were unambiguously identified.

Locations of camera traps in Bicuar National Park, Angola), with 2015 land cover at 100 m resolution. Monterosa et al. (2020).

In Bicuar National Park Monterosa et al. recorded 16 independent detections of two African Wild Dog groups over a total of 14 232 trapping-days. They were able to assign 15 individuals to one group and three to the other. African Wild Dogs were detected consistently throughout the sampling period at a mean detected group size of 3.6 individuals. No Cheetahs were detected.

Locations of camera traps in Cuatir Private Reserve, Angola, with 2015 land cover at 100 m resolution. Monterosa et al. (2020).

In Cuatir Private Reserve Monterosa et al. obtained 13 independent detections of at least two Cheetah individuals and no detections of African Wild Dogs over a total of 5173 trapping-days of systematic surveying. Unstructured camera trapping provided records of an individual cheetah in July 2014, and a coalition of two male Cheetahs in October 2017. They were not able to match any of these Cheetahs with those of the 2018 survey. A group with at least four African Wild Dog individuals was detected in July, August and October 2014, and another of at least five individuals in October 2016.

Monterosa et al.'s findings build on recent surveys that indicate the occurrence of cheetahs and African Wild Dogs in Luengue-Luiana and Mavinga national parks, and in the Cuanavale and Cuito river catchments. African wild dogs have also been observed in Bicuar National Park, and in Mupa National Park, and Mucusso Reserve, and Cheetahs in and around Iona and Cameia national parks. Monterosa et al. found no records of Cheetahs or African Wild Dogs for 2008-2018 in Angola in the Global Biodiveristy Information Facility.

Wild Cheetah, Acinonyx jubatus, detected through unstructured camera trapping in Cuatir Private Reserve, in July 2014. Stefan van Wyk/Orynx.

Monterosa et al.'s findings indicate that the African Wild Dog’s range as currently delimited should be extended about 750 km further west-north-west from the Angolan/Namibian border, beyond the Cunene river and including Bicuar National Park. As the species has been regularly detected in the Park since at least 2015, this complies with International Union for the Conservation of Nature's Canid Specialist Group criteria as an area of African Wild Dog residency, with groups of over 10 individuals and breeding confirmed through multiple observations of groups with pups, made by park rangers in 2016. It is likely that other large extents of good quality habitat in Angola also harbour resident populations, and further monitoring to assess presence and residency status are required. 

 

 Distribution status of the the African Wild Dog, Lycaon pictus, in Angola, Namibia, Zambia, Zimbabwe, and Botswana and recent (2008-2018) records in Angola. Study sites: BNP, Bicuar National Park; CPR, Cuatir Private Reserve. Monterosa et al. (2020).

 

Cheetahs have been observed regularly in the lower Angolan range of the Cubango River, and also in south-eastern, south-western and central-eastern Angola in the provinces of Namibe, Cuando Cubango and Moxico. These reports suggest that International Union for the Conservation of Nature's classification of the south-western Angolan range for the Cheetah should be changed from Possibly Extant to Extant.

Distribution status of the Cheetah, Acinonyx jubatus, in Angola, Namibia, Zambia, Zimbabwe, and Botswana, and of recent (2008-2018) records in Angola. Monterosa et al. (2020).

Monterosa et al.'s findings will support the new political willingnessin Angola to invest in wildlife conservation strategies and will help to unlock conservation funding for the Cheetah, African Wild Dog and other Carnivores. Given that the majority of the distribution of these two species potentially falls outside protected areas where they are more susceptible to anthropogenic threats, Monterosa et al. emphasize the urgency of identifying remnant populations in Angola and quantifying any threats to the species.

See also...

Follow Sciency Thoughts on Facebook.