Wetlands (2021) 41:110 https://doi.org/10.1007/s13157-021-01510-w CONSTRUCTED WETLANDS Pollution or Protection - What Early Survey Data Shows on Rapid Waterbird Utilisation of a Newly Established Sewage Treatment Plant in Urban Ghana, West Africa Lars Haubye Holbech1  · Cara Caroline Cobbinah1 Received: 16 April 2021 / Accepted: 26 October 2021 © The Author(s), under exclusive licence to Society of Wetland Scientists 2021 Abstract Rapid urbanisation increasingly isolates and exerts pressure on natural wetlands, particularly in the fast-growing developing countries of the tropics, including those of West Africa. Constructed wetlands such as sewage treatment plants, may unin- tendedly offer wildlife protection due to prohibitive access control and limited use, thereby attracting wary and specialised waterbirds in otherwise heavily disturbed formally protected wetlands with less polluted waterbodies. We present data from a rapid survey on 1-year post-opening colonisation and use of waterbirds in a recently constructed 11 ha restricted-access sewage treatment plant, situated in Ghana’s capital, Accra. During November-December 2013 and January 2014, nine daily counts in each month produced an accumulated count of >4200 observations belonging to 26 species of waterbirds, including several important Afro-Palaearctic and intra-African migrants, hereunder ardeids, piscivorous divers, waterfowl and waders. The distributional patterns of waterbirds clearly reflected local foraging opportunities and water quality parameters in the system of 12 inter-connected waste stabilisation ponds. A nearby semi-natural wetland with cleaner waterbodies, but higher levels of human interference, supported fewer waterbirds, predominantly commensal gregarious species. Our data suggests that strict protection from disturbances outweighs possible negative implications attributed to mere pollution of waterbodies supporting various waterbird guilds, thus highlighting the potential importance of informally protected sewage treatment plants distributed in functional networks, as a complement to designated wetlands. We anticipate that establishing similar or larger plants jointly will improve sewage treatment and waterbird conservation in urban Ghana, and West Africa in general. Keywords Aquatic birds · Abundance · Colonisation · Constructed wetland · Diversity · Water quality Introduction for agriculture, farming, fishing, hunting, livestock rear- ing, mining, and pollution from sewage encroach upon and Wetlands are high on the conservation agenda across the degrade waterbodies with associated wildlife (e.g. Schuyt globe due to decades of unsustainable anthropogenic exploi- 2005; Verhoeven et al. 2006; Junk et al. 2013; De Troyer tation and degradation (e.g. Dudgeon et al. 2006; Keddy et al. 2016). Among the vulnerable wetland fauna are vari- et al. 2009; Davidson 2014), but also by virtue of their piv- ous guilds of waterbirds, including many migrants (Okes otal role in ecosystem functioning and services related to et al. 2008; Sutherland et al. 2012; Runge et al. 2015). Con- climate change, hereunder flood control (Knapp et al. 2019; servation efforts to safeguard wetlands include regulations Shokoufeh et al. 2021), drought management (Dean et al. and protection of key sites (Beatty et al. 2014; Kleijn et al. 2015; Dixon et al. 2021) and carbon sequestration (Day- 2014), but such efforts are often hampered by increasing athilake et al. 2021). Wetlands are subjected to heavy distur- human population and associated economic growth, as well bance regimes, particularly in urban areas, where draining as inadequate management, legislation and law enforce- ment (O’Connell 2000; Aynalem and Bekele 2008; Gbogbo 2007a; Gbogbo et al. 2008, 2009). Across most developing * Lars Haubye Holbech tropical countries, wetland conservation and management l.holbech@gmail.com are therefore typically curtailed by unsustainable human 1 Department of Animal Biology and Conservation Science, activities, particularly in densely populated urban areas of University of Ghana, P.O. Box LG 67, Legon, Accra, Ghana sub-Saharan Africa (Mitchell 2013; Vickery et al. 2014), Vol.:(012 3456789) 110 Page 2 of 15 Wetlands (2021) 41:110 hereunder West Africa (Adams 1993; Uluocha and Okeke be inferior to designated protected areas such as Ramsar 2004), including Ghana (Gbogbo 2007b; Lamptey and sites (Hamdi and Ismail-Hamdi 2014; Kleijn et al. 2014), Ofori-Danson 2014). substantial evidence suggests that man-made wetlands With the current prospects of unpredictable and unu- may increasingly contribute to waterbird conservation in sual rainfall patterns, related to global warming, wetlands, the near future (Murray and Hamilton 2010; Wang et al. whether natural or man-made, are increasingly a focal inte- 2016; van Biervliet et al. 2020). As such, although often grated part of urban landscape and environmental planning comparatively small, isolated and situated far from other (Erwin 2009; Junk et al. 2013). As such, albeit constituting larger protected wetlands, artificial wetland habitats can seriously threatened ecosystem components, rivers, streams, increasingly serve as replacement or complementary ref- lakes, dams and ponds likewise offer great potentials for uges for lost or degraded natural wetland biota, including mitigation against environmental and economic disasters vulnerable waterbird guilds (Afdhal et al. 2012; Murray related to rainstorms and flooding (Douglas et al. 2008; et al. 2012; Wiegleb et al. 2017; Giosa et al. 2018). The Knapp et al. 2019; Shokoufeh et al. 2021), as well as pro- efficiency and success of STPs for waterbird conserva- longed periods of drought (Dean et al. 2015; Dixon et al. tion, however, depend on the degree and extent of applied 2021). Their importance for sustained ecosystem functions ecology-based management practices and access control and services therefore cannot be over-emphasised, not the (Ashkenazi 2001; Hsu et al. 2011; Murray et al. 2014; least across the African continent burdened by low agricul- Wang et al. 2016; Wiegleb et al. 2017; van Biervliet et al. tural production, poor infrastructure, urban congestion and 2020). impoverished health facilities (Douglas et al. 2008; Belle Majority of African studies that assess waterbird diver- et al. 2018; Dixon et al. 2021). sity and habitat utilisation in STPs are from the southern Formally protected wetlands in Africa, including Ram- and eastern regions of the continent, with apparently limited sar sites, are increasingly subjected to over-exploitation information from the northern, western and central parts and illegal activities (Schuyt 2005; Gbogbo et al. 2008; (Ashkenazi 2001; Harebottle et al. 2008; Harrison et al. Finlayson 2012; Junk et al. 2013; Lamptey and Ofori-Dan- 2010; Wang et al. 2014). Moreover, few studies from Africa son 2014; Dixon et al. 2021). Waterbirds and their habitats document the early phases of STP waterbird colonisation are often threatened by illegal and unsustainable utilisation (Ashkenazi 2001; Dean et al. 2015), just as most data col- of natural resources, including fish stock, invertebrates lected are from coastal areas (Harrison et al. 2010) or inland and fuel wood (O’Connell 2000; Willoughby et al. 2001; plants, integrated with natural wetlands (Harebottle et al. Gbogbo et al. 2008; Okes et al. 2008). Alongside unsus- 2008). Ghana, and Accra in particular, has in the past dec- tainable resource extraction that interferes with waterbird ade initiated new strategies for improved sewage treatment foraging and nesting ecology, the avifauna is also indi- to curb the heavy pollution that threatens many waterbod- rectly affected by water pollution and draining, as well as ies in the urban coastal zone (Nixon et al. 2007). Since the directly by hunting, water sports and other recreational early 2000s, this has resulted in the planning and initial con- activities (O’Connell 2000; Uluocha and Okeke 2004; struction of improved sewage systems and different types of Mitchell 2013). Thus, informally protected or unman- STPs, one of which is the Legon Sewage Treatment Plant aged wetlands serve as important habitat supplements (hereafter called LSTP), situated amidst a densely populated and sometimes alternative refuges for waterbirds (Attu- area in the Accra metropolis, which is part of the Accra quayefio and Gbogbo 2001; Gbogbo 2007b; Harebottle Sewerage Improvement Project (ASIP). et al. 2008; Gbogbo and Attuquayefio 2010; Murray and In this study, we present data on the early-phase (~1 year) Hamilton 2010). Artificial or constructed wetlands (CW) colonisation by waterbirds at the LSTP, with emphasis on often receive informal protection, and include agro- and spatio-temporal abundance, distribution and diversity within aquaculture ponds, irrigation dams, salt ponds, drainage various components of a unique inland STP in urban Ghana. canals (Froneman et al. 2001; Otieno et al. 2015), as well The major objectives of this baseline study were to describe as sewage treatment plants (STP) of various types (Scholz and assess the waterbird fauna with regard to the: 1) early and Lee 2005; Wang et al. 2014). The construction of inflow and colonisation; 2) spatio-temporal patterns of dis- STPs is steadily expanding in many parts of the temperate tribution and diversity; 3) relative conservation importance zone (Scholz and Lee 2005; Knapp et al. 2019), subtropics of migrants and rarities; 4) protection potential for vulner- (Hsu et al. 2011; Wang et al. 2016; Giosa et al. 2018) and able and wary species; 5) relative importance of water pol- tropics (Murray and Hamilton 2010; Murray et al. 2012, lution versus unintended bird protection. We therefore aimed 2014), with a gradual increase in some parts of Africa at increasing the general knowledge base on waterbird uti- (Ashkenazi 2001; Kivaisi 2001; Harebottle et al. 2008; lisation of CWs in urban landscapes of West Africa. Our Wang et al. 2014; Dean et al. 2015; De Troyer et al. 2016). early data also serve to focus attention on the conservation Even though the waterbird diversity of CWs and STPs may potentials of newly established STPs, as well as highlighting 1 3 Wetlands (2021) 41:110 Page 3 of 15 110 the urgent need for additional and complementary refuges algal eutrophication level was moderate with a water trans- for vulnerable waterbirds, alongside improved sewage man- parency estimated at ~0.40-0.50 m during the peak of the agement in the West African sub-region. major dry and hot season in December-February, 2013-2014 (L.H. Holbech, pers. obs.). Incidentally, the Vaughan’s Dam underwent drastic changes in its human use along with the Methods operation of the LSTP in 2012-2013. Hence, intense anthro- pogenic disturbances were introduced abruptly in the form Study Area of commercial recreational activities, including angling, canoeing, cycling, jogging, play-grounds, group picnics, The LSTP (GPS: 5°39’50 N; 0°11’31 W) is situated ~14 km and large parties with loudspeakers. Moreover, small-scale north of the Accra coastline on a gentle slope (~25 m total aquaculture was established, and the old artificial wetland elevation gradient) adjacent to the main University of was manipulated by reed removal and thicket thinning, as Ghana, Legon campus (Fig. 1). It is bordered by the heav- well as deepening and cleaning of the banks by mechanical ily-trafficated Haatso-Atomic road, thickets and farmlands excavation (L.H. Holbech, pers. obs.). surrounding the Legon campus, as well as the Legon Botani- The LSTP measures ~0.11  km2 (~310 × 360  m), of cal Gardens with the integrated >60 yrs. old constructed which ~0.06  km2 are open water in the form of ponds Vaughan’s Dam, isolated from, but situated <200 m away lined by rocky banks, and access is restricted by 2.5 m from the LSTP. This nearby <0.02  km2 semi-natural wetland tall barbed wire fencing. It is a stabilisation pond system area comprises ~0.01 k m2 of open waterbodies bordered (Murray et al. 2014; Wang et al. 2014; Dean et al. 2015), by narrow verges of mixed swampy vegetation zones with constructed in 2010-2012 by an African Development dense reed beds, herbs and thickets (Fig. 1), and is supplied Bank project, and managed by the Accra Metropolitan by serene small streams that emanate from the adjoining Assembly under the ASIP. It consists of 12 ponds, with swampy areas of the Legon Botanical Gardens. The avi- four levels of three similar-sized ponds each (Figs. 1 and fauna of the Vaughan’s Dam was well-known >20 years 2). The four levels are inter-connected from upper level prior and up to the survey, and this waterbody was not con- A to lower level D as: A 1-3 = anaerobic ponds, 5 m deep, taminated by sewage or agricultural effluents, although the measuring ~60 × 40 m; B1-3 = facultative ponds, 2.5 m deep, measuring ~75 × 100 m; C1-3 = upper maturation ponds, 1.3 m deep, measuring ~85 × 75 m; D1-3 = lower maturation ponds, 1.3  m deep, measuring ~85 × 65  m (Fig. 2). Water flow is gravitational, with a maximum daily inlet capacity of ~9000  m3, receiving water from the campuses of Legon, the Presbyterian Boys’ Secondary School, and other surrounding state-owned institutions. The small anaerobic ponds are lined with a rubber mem- brane and flanked by three parallel concrete water-inlet ducts, measuring ~0.9 m wide and ~ 0.9 m deep (Figs. 1 and 2). These ponds were half covered with sludge at the time of our study, and fill up in about 5 years. The large facultative ponds are lined with granite rocks of ~0.1- 0.5 m diameter, each having a ~ 1.3 m wide rock intercept situated perpendicularly midway to reach halfway shore to shore (Figs. 1 and 2). The two similar three-set matura- tion ponds are likewise lined with granite rocks, but lack midway intercepts. At the time of our study, the granite rock linings were partially covered by pioneering sedge grasses, herbs and shrubs characteristic of nutrient-rich loamy soil, typically the Nut sedge grass Cyperus blepha- roleptos, the shrub White popinac Leucaena leucocephala, and the herbs Bachelor’s button Gomphrena celosioides, Hogweed Boerhavia diffusa, and Hornbeam-leaved cross- Fig. 1 a Aerial view of the Legon Sewage Treatment Plant (LSTP), berry Grewia carpinifolia, whereas the surroundings were with the surrounding urban areas and the Legon Botanical Gardens to the East; b Perpendicular perspective of the LSTP; images taken with dominated by 1-2 m tall and tough grasses such as Guinea a drone (DJI Mavic Pro®) grass Panicum maximum, partly covering the laterite 1 3 110 Page 4 of 15 Wetlands (2021) 41:110 Fig. 2 Map showing the position of the Legon Sewage Treatment Plant (LSTP), with surrounding coastal and inland wetlands within the Accra Plains (top), Southern Ghana (insert). LSTP only drawn approximately to scale (bottom) gravels. The vegetation lining the ponds, as well as float- maturation ponds, indicating explosive algal growth. The ing and submerged macrophytes were regularly (i.e. twice LSTP is the largest wetland in a radius of ~10 km from yearly) controlled mechanically or by Glyphosate herbi- the UGL campus, with the nearest other large constructed cide application, albeit not during our study period. Float- wetland ~9 km to the east, namely the ~1.40 k m2 Nungua ing or submerged macrophytes were only present in the C Agriculture Station Dam with its associated marshy areas and D ponds; D2 was particularly extensively covered by around the Ayensu River. The Sakumo Lagoon, a Ramsar water lilies (Nymphaea sp.) and reeds (Typha sp.) at the Site of ~13.40 k m2 which joins the Ashaiman Agricultural edges. Water clarity was least in the B and C facultative/ Dam, is situated ~17 km to the south-east (Fig. 2). 1 3 Wetlands (2021) 41:110 Page 5 of 15 110 Data Collection in each of the 12 ponds was undertaken on a single day in December 2013, with a Horiba U-52G multi-parameter Nine systematic bird counts per month, each typically water quality meter, including pH, turbidity (NTU) and total enduring 1.5-2 h, were conducted by two observers from dissolved oxygen (mg/l). November 2013 to January 2014, a period that constitutes the major dry season (November-February) on the Accra Data Analysis Plains, and coincides with the peak numbers of Afro-Palae- arctic waterbird migrants in Ghana (Ntiamoa-Baidu 1991; The three similar ponds at each level were regarded as repli- Lamptey and Ofori-Danson 2014). Given the likelihood that cate units in calculating monthly means ± SD of bird abun- the abundance of some species fluctuated throughout the dance based on counts at all the four pond levels over the day, three separate count periods were applied equally on three-month study period. We used the exponential of the each of the nine census days per month, i.e. in the morning Shannon-Wiener species diversity index (ExpH’) to calcu- (06 h00-08 h00), midday (12 h00-14 h00), and late after- late total effective species number (Jost 2006) for each pond noon (16 h00-18 h00). We anticipated that this systematic level based on the three replicate counts for each level over sampling of three time periods, repeated thrice per each the entire study period. Similarly, to quantitatively assess month, increased the probability of recording as many spe- the overall species similarity among the four pond levels, we cies as possible, as well as reflecting the true spatio-temporal used the Morisita-Horn index (CMH), which is an abundance- abundance at the plant. Each of the three replicate ponds based index resistant to under-sampling biases, and sensitive (1-3) at each level (A-D) was considered as a unit, within to the most abundant species, thus having a good discrimi- which all birds were counted, before moving on to the next nant ability for differences in functional diversity between pond, starting from either A1 or D 3 (Fig. 2) on each day, on compared sites (Jost et al. 2011). As such, we were able to a day-wise rotational basis. Total counts in each of the 12 assess the spatio-temporal abundance, diversity and simi- ponds were done from vantage points with good visibility larity of waterbirds distributed at the LSTP. Likewise, for and aided by a pair of 10 × 42 binoculars, and occasionally a the water quality parameters, the mean ± SD was calculated telescope (20-60×). Care was taken to avoid repeat-counting based on the replicate ponds (1-3) at each of the four levels. individuals that moved from pond to pond, particularly for These parameters were then related to the abundance and wary and mobile species such as ducks and other gregarious diversity of birds in order to evaluate any apparent implica- birds. This was done by constantly observing the movements tions for the waterbirds present at the four pond levels (A-D). of flushed individuals when cautiously approaching a pond. To assess any relationships between each of the three water The A-C ponds could comfortably be surveyed and moni- quality parameters (pH, TDO, turbidity) and the distribu- tored in this way, whereas D ponds were not visible from the tion of waterbirds across the four pond levels, we performed levels of A and B ponds. Most flocks relocated from only Pearson’s r-correlations of the parameters as explanatory one level to the adjacent, and rarely did so more than two variables (i.e. the mean of the three replicate ponds for each levels apart. In the case of large numbers of White-faced pond level) with the total abundance of each of the six forag- Whistling Duck Dendrocygna viduata and other gregarious ing guilds counted over the total period of three months, as birds, recounting several times with subtractions and addi- the respondent variables, and applied the best curve fits for tions or averaging were often deemed necessary; counts of r-values at n = 4. such species were associated with an error of ~10%. Notes Each waterbird species was classified into six overall for- on breeding were taken of nests, eggs, juvenile or immature aging guilds based on information in Ntiamoa-Baidu et al. birds. Other vertebrates, invertebrates and characteristic (1998), as: Guild 1 = Herbivorous waterfowl (ducks); Guild plants observed were also recorded opportunistically. 2 = Visual surface foraging waders; Guild 3 = Tactile surface As the lead author (LHH) had been resident in the Legon foraging waders; Guild 4 = Pelagic foraging waders; Guild campus area for >15 years during the period of 1990-2014, 5 = Stalking herons; Guild 6 = Diving waterfowl (grebes the presence and relative abundance of the avifauna in and cormorants). Based on this classification, the modes and around the Vaughan’s Dam and the Legon Botanical of foraging employed by the species with their respective Gardens was thoroughly known, and this familiarity was abundances could be compared, in order to assess the habitat based on years of observations during regular birdwatch- and niche provisions provided for by the four levels (ponds ing and walks (L.H. Holbech, pers. obs.). Similarly, non- A-D). Such assessment is important for understanding the systematic observations of nocturnal flight activities of spatial distribution of birds in various types of STPs, and ducks and ardeids were made during occasional birding or this information can be used to optimize construction design regular walks and runs in the vicinity (<0.5-1 km) of the and management practices in order to increase waterbird LSTP (L.H. Holbech, pers. obs.). Besides bird counting, on protection and conservation. Each species was also classified site sampling of physico-chemical water quality parameters according to migratory status, as Afro-Palaearctic migrant, 1 3 110 Page 6 of 15 Wetlands (2021) 41:110 intra-African migrant, and resident for Ghana (Dowsett- other waders. Similarly, at B ponds, common and wood Lemaire and Dowsett 2014), as well as global conservation sandpipers dominated, together with black-winged stilts, status following the IUCN Red List criteria (Handbook of spur-winged lapwings, as well as Senegal thick-knees, the Birds of the World Alive/BirdLife, online data). common greenshanks and cattle egrets (Table 1). The C The coincidence of the LSTP inception with the drastic and D ponds differed from A and B, having a dominance environmental changes at the Vaughan’s Dam in 2012-2013, of particularly White-faced Whistling Duck, as well as provided us with a unique opportunity to compare the early relatively higher numbers of cattle egrets and little grebes. development of the avifaunal colonisation at the LSTP with Although C and D ponds were very similar, C had par- the avifaunal changes at the Vaughan’s Dam, before and after ticularly high dominance of white-faced whistling ducks, these disturbances were introduced. As such, even though whereas cattle egrets dominated at D (Table  1). Total the in depth knowledge on the waterbird fauna of the nearby monthly counts from November 2013 to January 2014 Vaughan’s Dam that LHH had obtained during regular bird- were 1463, 1164 and 1597, respectively, indicating a con- watching in 1990-2014 (L.H. Holbech, pers. obs.), was not sistently high presence of most species during the study an integral part of the systematic LSTP data sampling, we period. However, the overall abundance was significantly were able to relate the LSTP waterbird composition with (χ2 = 36.3, p < 0.00001, df = 2) lower in December, pri- the avifaunal changes detected at the Vaughan’s Dam, up to marily attributed to relatively lower numbers of the three and during 2012-2013. We therefore performed a qualitative most abundant species, White-faced Whistling Duck, comparison (see Discussion) of the waterbird presence and Cattle Egret and Common Sandpiper (Table 1). The daily relative abundance, by converting the quantitative LSTP data count periods of morning-midday-afternoon did not show into five approximate abundance categories that were then any significant differences indicating stable populations related to similar abundance categories based on the data throughout the daytime hours. Cattle egrets and white- gathered at the Vaughan’s Dam during 1990-2014; namely: faced whistling ducks displayed the highest daily and ‘Abundant’ = ~20-25 or more birds observed on any visit; monthly abundance fluctuations during the study period, ‘Common’ = 10-20 birds observed on ~50-100% of visits; for which the latter were often flight-active after sunset ‘Frequent’ = 5-10 birds observed on ~50-75% of visits; and throughout the night (L.H. Holbech, pers. obs.). ‘Uncommon’ = 3-5 birds observed on ~25-50% of visits; ‘Rare’ = singletons or a pair observed on ~25% or less of visits (L.H. Holbech, pers. obs.). Species Richness, Diversity and Similarity in Relation to Pond Levels Results We recorded a total of 26 waterbird species during the three-month study period, including 11 waders, eight Total Abundance of Birds in Relation to Pond Levels ardeids, six waterfowl and the Malachite Kingfisher Corythornis cristatus (Table 1). Only seven species were We accumulated a total of 4224 bird observations counted recorded at A ponds, which contrasted with 19 or 20 at B, on 27 days over the three-month study period, translating C and D ponds. Species diversity was highest at C ponds, into a mean of 156 birds per day-count (Table 1). The six whereas it was very similar at B and D ponds (Table 1). most abundant species comprised ~82% of individual birds The distinctively higher species diversity at C ponds is counted, and were in the following order of descending attributable to a higher evenness and lower dominance of dominance; White-faced Whistling Duck (~20%), Cattle the most abundant species (Table 1). Likewise, abundance- Egret Bubulcus ibis (~17%), Common Sandpiper Actitis based species similarity (CMH) was highest between A hypoleucos (~14%), Black-winged Stilt Himantopus him- and B ponds, with ~86% species similarity (~54% shared antopus (~13%), Wood Sandpiper Tringa glareola (~11%) species), whereas C and D ponds had ~60% similarity and Spur-winged Lapwing Vanellus spinosus (~7%). Other and ~ 81% shared species (Table 2). In contrast, D ponds common species were Little Grebe Tachybaptus ruficollis versus A and B ponds, respectively, displayed relatively (~4%), Common Greenshank Tringa nebularia (3%) and low similarities of 15-20%, albeit with ~31-62% shared Senegal Thick-knee Burhinus senegalensis (3%). Abun- species. C ponds versus A and B ponds, respectively, had dance was significantly lower at A ponds (χ2 = 526.3, medium similarity of ~31-32%, but with ~42-58% shared p < 0.00001, df = 3), and 4-5 times higher at B, C and D species (Table 2). In summary, C and D ponds were most ponds, amongst which abundance did not differ signifi- similar with regard to abundances of particular species cantly (χ2 < 1.3, p > 0.5, df = 2). The most abundant birds as well as number of total shared species, with the least at A ponds were Common Sandpiper, Black-winged Stilt, similarity between A and D ponds, and moderate similar- Spur-winged Lapwing and Wood Sandpiper, with a few ity between B and C ponds. 1 3 Wetlands (2021) 41:110 Page 7 of 15 110 Table 1 Total number of species, species diversity and accumulated Plant, Accra (Ntotal = 27). Numbers in brackets represent the mean number of birds counted during nine counts ( Nmonth) in each month abundance ± SD across the three pond replicates (1-3) for each level of November 2013 - January 2014, at the Legon Sewage Treatment (A-D) Species Forag. g uildc Status Pond l evele All ponds English namea Scientific Localb IUCNd A B C D namea White-faced Dendrocygna 1 RB LC – 20 (7 ± 10) 564 275 859 (286 ± 116) whistling viduata (188 ± 31) (92 ± 106) duck Knob-billed Sarkidiornis 1 A LC – 1 (0 ± 1) – – 1 (0 ± 1) duck melanotos Common Gallinula 1 RB LC – – 17 (6 ± 6) 14 (5 ± 2) 31 (10 ± 6) moorhen chloropus Senegal thick- Burhinus sen- 2 A/RB LC – 110 (37 ± 24) – 20 (7 ± 12) 130 (43 ± 35) knee egalensis Common Charadrius 2 P LC 6 (2 ± 2) 6 (2 ± 4) 1 (0 ± 1) – 13 (4 ± 2) ringed hiaticula plover Spur-winged Vanellus 2 RB LC 53 (18 ± 1) 66 (22 ± 7) 64 (21 ± 1) 105 (35 ± 6) 288 (96 ± 11) lapwing spinosus African wat- Vanellus 2 RB LC – – – 64 (21 ± 12) 64 (21 ± 12) tled lapwing senegallus African Actophilornis 2 RB LC – 4 (1 ± 2) 35 (12 ± 3) 5 (2 ± 3) 44 (15 ± 8) jacana africanus Common Gallinago 2 P LC – 1 (0 ± 1) – – 1 (0 ± 1) snipe gallinago Common Actitis 2 P LC 93 (31 ± 16) 419 57 (19 ± 14) 37 (12 ± 8) 606 (202 ± 27) sandpiper hypoleucos (140 ± 57) Wood sand- Tringa 2 P LC 41 (14 ± 5) 314 84 (28 ± 20) 41 (14 ± 10) 480 (160 ± 37) piper glareola (105 ± 27) Common Tringa tota- 2 P LC – 1 (0 ± 1) – – 1 (0 ± 1) redshank nus Little stint Calidris 3 P LC 1 (0 ± 1) 1 (0 ± 1) – – 1 (1 ± 1) minuta Black-winged Himantopus 4 RB/P? LC 91 (30 ± 24) 205 (68 ± 41) 192 (64 ± 40) 46 (15 ± 6) 534 (178 ± 32) stilt himantopus Common Tringa nebu- 4 P LC 1 (0 ± 1) 68 (23 ± 7) 49 (16 ± 20) 18 (6 ± 7) 136 (45 ± 24) greenshank laria Green-backed Butorides 5 RB LC – – 8 (3 ± 2) 2 (1 ± 1) 10 (3 ± 2) heron striata Squacco Ardeola ral- 5 P LC – 4 (1 ± 2) 23 (8 ± 6) 6 (2 ± 3) 33 (11 ± 10) heron loides Cattle egret Bubulcus ibis 5 A/RB LC – 39 (13 ± 15) 114 (38 ± 25) 571 724 (241 ± 44) (190 ± 24) Grey heron Ardea cinerea 5 P/RB LC – 2 (1 ± 1) 11 (4 ± 1) 9 (3 ± 2) 22 (7 ± 3) Intermediate Ardea inter- 5 A/RB? LC – 1 (0 ± 1) 16 (5 ± 3) 7 (2 ± 2) 24 (8 ± 5) egret media Black heron Egretta ard- 5 RB LC – – 6 (2 ± 2) 7 (2 ± 3) 13 (4 ± 4) esiaca Little egret Egretta 5 P/RB? LC – – 13 (4 ± 4) 2 (1 ± 1) 15 (5 ± 4) garzetta Western reef Egretta 5 RB LC – – 7 (2 ± 1) – 7 (2 ± 1) egret gularis Little grebe Tachybaptus 6 RB LC – 4 (1 ± 2) 57 (19 ± 4) 99 (33 ± 5) 160 (53 ± 2) ruficollis Long-tailed Microcarbo 6 RB LC – – 22 (7 ± 13) – 22 (7 ± 13) cormorant africanus 1 3 110 Page 8 of 15 Wetlands (2021) 41:110 Table 1 (continued) Species Forag. guildc Status Pond levele All ponds English namea Scientific Localb IUCNd A B C D n amea Malachite Corythornis 6 RB LC – 1 (0 ± 1) 1 (0 ± 1) 2 (1 ± 1) 4 (1 ± 1) kingfisher cristatus Total accumulated abundance of 27 daily counts (9 counts per 286 (95 ± 19) 1267 1341 1330 4224 month) (422 ± 133) (447 ± 97) (443 ± 136) (1408 ± 222) Species richness (S) 7 19 20 19 26 Species diversity (ExpH’) 4.23 6.21 7.58 6.59 10.01 a,b Dowsett-Lemaire and Dowsett (2014): RB = Resident breeding; P = Palaearctic migrant; A = African migrant; c Ntiamoa-Baidu et al. (1998); d LC = Least concern; e A = anaerobic (5 m), B = aerobic facultative (2.5 m), C and D = aerobic maturation (1.3 m) Table 2 Abundance-based species similarity (CMH) among the four chloropus, exclusively and equally found in C and D ponds, pond levels A-D, during November 2013 to January 2014 at the and a single Knob-billed Duck Sarkidiornis melanotos in LSTP, Accra. Shared species in % is shown in brackets January 2014 at B ponds (Table 1). Visual surface forag- Level A B C D ing waders (Guild 2), as the most diverse foraging guild with nine species, was represented at all levels, but with the A 0.863 (53.8) 0.322 (42.3) 0.154 (30.8) highest abundance and diversity at B ponds, a pattern simi- B 0.311 (57.7) 0.199 (61.5) larly displayed by the two very abundant small sandpipers C 0.603 (80.8) (Tables 1 and 3). Only one tactile surface foraging species D (Guild 3), Little Stint Calidris minuta, was detected, indicat- ing the lack of exposed mud flats during the study period. In contrast, the pelagic foraging waders (Guild 4), notably Distribution of Foraging Guilds in Relation to Pond represented by black-winged stilts, showed high affiliation to Levels and Water Quality B and C ponds, moderate for A ponds, and only occasional at D ponds. The very diverse guild of eight piscivorous The White-faced Whistling Duck (Guild 1) was absent from stalking or darting ardeids (Guild 5) showed outstandingly A ponds, scarce at B ponds, fairly abundant at D ponds, and high diversity and abundance at C and D ponds (7-8 spe- most abundant at C ponds (Table 3). Only two other species cies respectively), the latter dominated by large cattle egret in Guild 1 were observed; the Common Moorhen Gallinula flocks. This guild, however, was not recorded at A ponds. Table 3 Total waterbird Foraging guilda Pond Level (n = 3) All ponds abundance distributed on (n = 12) foraging guilds (1-6), ecological A B C D diversity (ExpH’) across all foraging guilds, and physico- 1 – 21 (0.5) 581 (13.8) 289 (6.8) 891 (21.1) chemical parameters for each 2 193 (4.6) 921 (21.8) 241 (5.7) 272 (6.4) 1627 (38.5) pond level (A-D) and all ponds 3 1 (< 0.1) 1 (< 0.1) – – 2 (< 0.1) combined, during November 2013 to January 2014 at the 4 92 (2.2) 273 (6.5) 241 (5.7) 64 (1.5) 670 (15.9) LSTP, Accra. Numbers in 5 – 46 (1.1) 198 (4.7) 604 (14.3) 848 (20.1) brackets are % of all 4224 birds 6 – 5 (0.1) 80 (1.9) 101 (2.4) 186 (4.4) counted or % of all 26 species Total N (%) 286 (6.8) 1267 (30.0) 1341 (31.7) 1330 (31.5) 4224 (100.0) observed Total S (%) 7 (26.9) 19 (73.1) 20 (76.9) 19 (73.1) 26 (100.0) Exp(H′) 1.92 2.18 4.18 3.88 4.27 pH 7.9 ± 0.1 8.8 ± 0.2 10.6 ± 0.1 8.8 ± 0.4 9.1 ± 1.0 TDO (mg/l) 9.7 ± 7.8 16.1 ± 3.1 24.7 ± 1.5 8.5 ± 3.2 14.7 ± 7.7 Turbidity (NTU) 301.3 ± 11.5 358.3 ± 25.2 369.0 ± 83.2 18.0 ± 0.9 261.7 ± 154.0 Water depth (m) 5.0 2.5 1.3 1.3 – a 1 = Herbivorous waterfowl (ducks/moorhens), 2 = Visual surface foraging waders, 3 = Tactile surface for- aging waders, 4 = Pelagic foraging waders, 5 = Stalking herons, 6 = Diving piscivorous birds (waterfowl/ kingfishers) 1 3 Wetlands (2021) 41:110 Page 9 of 15 110 Similarly, the guild of diving piscivores (Guild 6), repre- a sented primarily by the Long-tailed Cormorant Microcarbo africanus and Little Grebe, showed highest affinity for C and D ponds, with a few of the latter species at B ponds, and a complete absence of the guild at A ponds. The levels of pH showed weak to moderate alkalinity, and there were significant differences among the four pond levels (Kruskal-Wallis H-test = 9.359, p = 0.02488, df = 3), with A ponds lowest, C ponds highest, and B and D ponds similar (Fisher’s LSD test) (Table 3). Total dissolved oxygen (TDO) showed significant differences across the pond levels (Kruskal-Wallis H-test = 8.128, p = 0.04344, df = 3), with C ponds higher than both A and D ponds, whereas B and C ponds, as well as A, B and D ponds were similar (Fish- er’s LSD test). Turbidity also varied significantly among b the four levels (Kruskal-Wallis H-test = 8.744, p = 0.0329, df = 3), with D ponds significantly lower than A, B and C ponds. However, turbidity levels in the three latter ponds were not significantly different (Fisher’s LSD test). In sum- mary, ponds B and C showed highest levels of both TDO and turbidity, indicating highest levels of algal growth, whereas the anaerobic nature of A ponds was evidenced by very low TDO and moderately high turbidity. The relatively low tur- bidity and TDO in D ponds indicated lower algal densities. The respective correlations between each of the three water quality parameters (pH, TDO and turbidity), meas- ured within the four pond levels (A, B, C, D), as against total abundances of each of the six foraging guilds counted over the 3 months, did not show significant relationships for any of the best-fitted trend lines at the 5% level. However, Fig. 3 Correlation between overall bird abundance (total accumulated with regard to turbidity versus total abundances of forag- counts over 3  months) versus turbidity (mean turbidity across three ing guilds, Guild 2 and 4 showed positive correlations, in replicates for each of the four pond levels, A, B, C, D) at the Legon Sewage Treatment Plant; (a) Guild 2 and 4; (b) Guild 5 and 6 contrast to Guild 5 and 6, indicating negative relationships (Fig. 3). These non-significant correlations suggest that piscivorous divers (i.e. cormorants and grebes) or dart- numbered at most 17 species (~65%), including Little Egret ers (ardeids) are favoured in D ponds with lower turbidity Egretta garzetta and Intermediate Egret Ardea intermedia, (i.e. higher water clarity), also shown by the significantly both with uncertain breeding status in Ghana (Dowsett- higher abundances of those two guilds, particularly in the Lemaire and Dowsett 2014). Four species were intra-African D ponds (Table 3). In contrast, for Guild 2 and 4, and partly migrants, including Intermediate Egret. Overall, the pro- also for Guild 1, the high turbidity, particularly in B and C portions of resident breeders therefore seemed higher than ponds, appeared to favour the presence of waterbirds forag- migrants. Even amongst migrants, Afro-Palaearctics were in ing either visually on the surface (Guild 2), or by tactile the majority. All species recorded had IUCN Red List status of (Guild 4) or filtering (Guild 1) means in the pelagic water ‘Least Concern’, and except for Knob-billed Duck, all species zones with high turbidity, attributed to either algal growth are commonly recorded in coastal habitats of Ghana (Ntiamoa- or dead organic matter in the suspended sludge of the turbid Baidu 1991; Lamptey and Ofori-Danson 2014). waterbodies of B and C ponds. Migratory and Conservation Status of Waterbirds Discussion We recorded a total of 11 Afro-Palaearctic migrants (~42% Distributional Patterns of Waterbirds at the LSTP of overall species richness), including Black-winged Stilt, whose migration status remains uncertain in Ghana (Dowsett- The LSTP waterbird fauna was represented by six separate Lemaire and Dowsett 2014). Resident breeders within Ghana foraging guilds, two of which dominated in terms of both 1 3 110 Page 10 of 15 Wetlands (2021) 41:110 species number and abundance, namely visual surface wad- the size of wetland (Beatty et al. 2014; van Biervliet et al. ers (Guild 2) and stalking ardeids (Guild 5), in addition to 2020), the proximity and connectivity to other wetlands two non-diverse but abundant guilds, herbivorous waterfowl (Erwin 2002; Knapp et al. 2019), the surroundings (Dean (Guild 1) and pelagic foraging waders (Guild 4). This guild et al. 2015), food availability (Afdhal et al. 2012; Murray pattern, with relatively low abundance of diving piscivores et al. 2014), and protection against disturbances (Harrison (Guild 6) and tactile foraging waders (Guild 3) suggests that et al. 2010; Dean et al. 2015). Nevertheless, it would be turbidity was excessively high and/or that prey availability inappropriate to explain away the significant bird numbers was limited in water columns and on exposed mudflats. The counted at the LSTP, as attributed to mere random events, university community and its co-users of the LSTP went on particularly as several other formally protected or more natu- vacation during the months of December and January (i.e. ral wetlands of considerable size are within relatively short two of the driest months on the Accra Plains), causing the flight distances, including the 13.40  km2 Sakumo Ramsar facility to run at low capacity. It was only during this period site, only 17 km away. Two obvious questions are appar- of low water levels at C and D ponds that foraging conditions ent, though: 1) are other nearby wetlands increasingly less were favourable for Guild 3, which included little stints. Par- attractive or insufficient to hold increasing waterbird popula- ticularly D ponds with the highest water clarity (i.e. low tur- tions?; 2) is the LSTP offering superior protection, and as bidity) supported piscivorous darters and divers (Guild 5 and such, despite its heavier pollution levels, still particularly 6), although C ponds were also frequented relatively often attractive to wary species? Indeed, both explanations are not by ardeids, cormorants, grebes and kingfishers. At the time mutually exclusive, and probably valid, given the currently of the study, it was unlikely that fishes may have been intro- challenged status of wetlands in the urban areas of the Accra duced by natural means from the nearby small Vaughan’s Metropolis (Gbogbo and Attuquayefio 2010; Lamptey and Dam, although pelagic invertebrates that constitute major Ofori-Danson 2014). food sources for pursuit-diving little grebes may have been For instance, although not completely comparable with abundant (Santoul and Mastrorillo 2004). Likewise, the few regard to size and structure of the LSTP, it is remarkable long-tailed cormorants suggested that, although these were that the nearby Vaughan’s Dam (hereafter only VD), sup- attracted to the ponds, successful prey captures were most plied with rain water from adjoining serene environments, likely large invertebrates (Otieno et al. 2015). Although it and thus obviously with a superior water quality and clarity is possible that particular pelagic invertebrates (e.g. preda- as compared to the turbid and highly eutrophicated LSTP ceous diving beetles, Dysticidae) were most abundant in the ponds, only supported ~5-10 regular or frequent waterbird B and C ponds, the significantly higher turbidity measured species, up to and during the same study period (L.H. Hol- there, most likely, may have limited actual prey availability bech, pers. obs.; Table 4). Most plentiful were gregarious, for both diving and darting foragers, as compared to the D commensal and least wary species, such as the abundant ponds with more transparent water, even if the latter were Cattle Egret with a rookery of ~500 birds (L.H. Holbech, supporting lower prey densities. In summary, the distribu- pers. obs.), the commonly breeding Long-tailed Cormorant, tion of waterbirds at LSTP largely followed the ecological as well as the frequent-common Squacco Heron Ardeola ral- requirements for each of the six foraging guilds, thus prob- loides and Black-crowned Night Heron Nycticorax nycti- ably reflecting a compromise between prey abundance and corax (Table 4). After 2012-2013, the same period that the availability versus water level (Ntiamoa-Baidu et al. 1998; operation of the LSTP initiated, the VD had been subjected Gbogbo et al. 2009) and clarity (Holbech et al. 2018), with to intensification of small-scale aquaculture and commercial the latter related to nutrient concentrations and algal blooms recreational activities, thus rapidly reducing the numbers of (Lamptey and Ofori-Danson 2014). wary waterfowl and wader species, hereunder sandpipers, lapwings, moorhens and jacanas, with a complete absence of Significance and Potential Implications of LSTP Data ducks and little grebes (Table 4). This semi-natural wetland, for Waterbird Conservation in Urban Ghana both with a higher aesthetic value and better water quality, thus supported far fewer waterbirds than the ‘repugnant’ This study was conducted ~1 year post-opening of the sew- LSTP, hence most likely attributed to its small size, com- age inlet, October 2012, and documented at least 26 water- bined with the much higher anthropogenic disturbance lev- bird species with average day-counts of ~160 birds, and els, thereby preventing wary species from seeking adequate occasionally up to >220 birds. Notable abundant species refuge. Indeed, we find it very likely that many of the for- were White-faced Whistling Duck (up to ~50-100 at a time), merly more regularly recorded wary waterbirds (e.g. water- Common Sandpiper, Black-winged Stilt, Wood Sandpiper, fowl) at the VD may have found refuge at the LSTP, which is Spur-winged Lapwing, Little Grebe, Common Greenshank just a very short flight distance away. Ironically, the attempts and Senegal Thick-knee. Many factors may contribute to to ‘beautify’ and make the VD more attractive to humans waterbird colonisation of constructed wetlands, hereunder also made it more repellent for many waterbirds, which then 1 3 Wetlands (2021) 41:110 Page 11 of 15 110 Table 4 Qualitative comparison Species LSTP Vaughan’s Dam of the waterbird faunas between the LSTP and the Vaughan’s 2013-2014 Before 2012-2013 During 2012-2013 Dam, before and during 2012- 2013. Abundance categories as White-faced whistling duck Abundant – – per the d efinitionsa Knob-billed duck Rare – – Common moorhen Frequent Frequent Uncommon Senegal thick-knee Common Common Frequent Common ringed plover Uncommon – – Spur-winged lapwing Abundant Uncommon Uncommon African wattled lapwing Common Uncommon Uncommon African jacana Frequent Frequent Uncommon Common snipe Rare – – Common sandpiper Abundant Frequent Frequent Wood sandpiper Common Uncommon Rare Common redshank Rare – – Little stint Rare – – Black-winged stilt Abundant Uncommon Rare Common greenshank Common Uncommon Rare Green-backed heron Frequent Frequent Rare Squacco heron Frequent Frequent Common Cattle egret Abundant Abundant Abundant Grey heron Frequent Rare – Purple Heron – Rare – Goliath Heron – Rare – Intermediate egret Frequent Rare – Black heron Frequent Uncommon Rare Little egret Frequent Rare – Western reef egret Uncommon Rare Rare Black-crowned Night Heron Rare (nocturnal) Uncommon-Frequent Common Dwarf Bittern – Rare – Little grebe Common Rare – Long-tailed cormorant Frequent Uncommon-Frequent Common African Darter – Uncommon Rare Giant Kingfisher – Rare – Pied Kingfisher – Frequent Uncommon Malachite kingfisher Rare Uncommon Rare a ‘Abundant’ = ~20-25 or more observed on visit, ‘Common’ = at least 10-20 observed on ~50-100% of vis- its, ‘Frequent’ = 5-10 observed on ~50-75% of visits, ‘Uncommon’ = 3-5 observed on ~25-50% of visits, ‘Rare’ = singletons or a pair observed on ~25% of visits, ‘-‘= not recorded (Absent) found refuge at the, for humans, repugnant LSTP. Future translates into a mean density of ~2700 birds/km2 (~27/ studies, involving capturing and colour marking, would ha), and occasionally up to ~3500-4000. In comparison the evaluate apparent LSTP-VD movements of waterbirds, here- mean density of birds at nearby coastal wetlands, includ- under to what extent true dispersal or mere commuting are ing Ramsar sites, ranges between 300 and 900 birds/km2 quantitatively involved in any source-sink dynamics between (Gbogbo and Attuquayefio 2010), given their much larger the two adjacent ‘contesting’ wetlands (Erwin 2002; Beatty areas (>2.50 k m2), such as Sakumo Lagoon (13.40  km2) and et al. 2014). We regularly observed cattle egrets, cormorants, Densu Delta (46.20  km2). Overall bird density at LSTP was night herons and squacco herons commuting between the also considerably higher than those recorded for rice fields two CWs, all gregarious species, and colonial breeders at across West Africa, ranging from 400 to 2000 birds/km2 the VD. (Wymenga and Zwarts 2010) or artificial wetlands of Tuni- The relatively small LSTP pond-bank-verges area sia with >100 birds/km2 (Hamdi and Ismail-Hamdi 2014). (~0.06 k m2) implies that the overall average bird abundances However, LSTP-density is similar to densities reported from 1 3 110 Page 12 of 15 Wetlands (2021) 41:110 a South African ~0.53  km2 large wastewater treatment plant as minimising the negative effects of sewage discharge of >2600 birds/ km2 (Harebottle et al. 2008). The relatively into natural waterbodies and the sea (Murray et al. 2014; high density of waterbirds recorded at the LSTP through- De Troyer et al. 2016). Likewise, monitoring and research out the study period, indicates that despite heavily polluted on waterbirds and their ecology at STPs, will provide more water bodies, foraging opportunities remain conducive for knowledge on the conservation impacts that these artifi- several waterbird guilds, thus highlighting the attractive- cial wetlands have in rapidly growing coastal (Ashkenazi ness to waterbirds with regard to abundant food sources. 2001; Harrison et al. 2010) or inland (Afdhal et al. 2012; Our results are consistent with small-medium sized STPs in Dean et al. 2015) urban zones, hereunder in West Africa. arid areas of Africa providing stable waterbodies even in the We therefore recommend a rapid expansion of STPs in driest months (Dean et al. 2015), although small shallow- Ghana and West Africa, and highlight the importance of water ponds with more eutrophic water, and thus higher pro- future monitoring and assessment of the impacts such plants ductivity, often support relatively higher bird densities than have on the abundance, diversity and distribution of water- larger, oligotrophic low-productivity dams (Afdhal et al. birds. State-owned lands, currently reserved for public green 2012; Hamdi and Ismail-Hamdi 2014). spaces and parks, including cemeteries and other recrea- The 26 waterbird species comprised six distinctive forag- tional sites without housing potentials, could be earmarked ing guilds that utilised water columns, banks, and associated for STP developments of variable size and inter-connectivity grounds and grassland verges. Apart from favourable forag- (Erwin 2002; Beatty et al. 2014). Areas adjoining govern- ing prospects, this diverse avian assemblage witnesses that mental institutions and facilities, including the military, fence-enclosure and staff surveillance of the plant provided aviation in-flight zones, power lines and plants could also sufficient protection for waterbirds against various human be integrated in networks of informally protected areas of interferences. In contrast, both formally protected Ramsar CWs (Beatty et al. 2014), hereunder STPs (De Troyer et al. sites (e.g. Sakumo and Densu Delta) and unprotected coastal 2016; Knapp et al. 2019). Additionally, focus should be on wetlands in the Accra Metropolis are prone to high levels the ecological and management implications of STPs for of natural resource exploitation (Attuquayefio and Gbogbo biodiversity complexity (Wiegleb et al. 2017), hereunder 2001; Lamptey and Ofori-Danson 2014), thus negatively vulnerable species (Ashkenazi 2001; van Biervliet et al. affecting waterbird food resources such as fish and crabs 2020), intra- and interspecific interactions (Afdhal et al. (Gbogbo et al. 2008). Furthermore, direct disturbances from 2012; Murray et al. 2014), including agonistic and inter- hunting (Afdhal et al. 2012), predation from carnivores ference competition (Harrison et al. 2010). Future impor- (Dean et al. 2015; Knapp et al. 2019), and other activities tant research aspects may include species’ susceptibility to that distress wary species such as waterfowl have a negative microbial diseases (Murray et al. 2014), the potentials for impact (Gbogbo 2007b; Gbogbo et al. 2008). We therefore heavy metal bioaccumulation (López-Perea et al. 2019), and believe that the combined effect of a nutrient rich and safe for zoonosis transmission. Finally, we recommend research environment (Dean et al. 2015) are prime factors for the into STP management practices that reconcile effective rapid waterbird colonisation at LSTP. Constructed wetlands water treatment with habitats that support a balanced and of this nature, even when located inland (Dean et al. 2015), diverse waterbird fauna (Harrison et al. 2010; Dean et al. may have positive implications for waterbird conservation 2015; Knapp et al. 2019; van Biervliet et al. 2020). in the urban areas of Ghana and West Africa in general, not- withstanding the poor conservation status of many formally protected wetlands in densely populated regions of Ghana Conclusion (Attuquayefio and Gbogbo 2001; Nixon et al. 2007; Lamptey and Ofori-Danson 2014) and the sub-region (Adams 1993; We demonstrate that a relatively small constructed urban Uluocha and Okeke 2004; Mitchell 2013). wetland situated far from the coast or other nearby large The ASIP, under the Accra Metropolitan Assembly, ini- inland wetlands was subjected to rapid colonisation by a tially planned for an additional similar STP adjoining the diverse assemblage of both migrant and resident waterbirds. Densu Delta Ramsar site, but further constructions ceased Waterbirds benefitted from the rich food sources of inverte- prior to the LSTP completion. Therefore, LSTP is presently brates and plankton, in combination with informal protection the only available waste stabilisation pond system in Accra by virtue of the restricted nature of the managed STP. We and coastal Ghana, whilst other mechanical STPs have also anticipate that the abundance and species diversity of water- been constructed. Based on the rapid colonisation, con- birds will increase as other trophic levels and community sistent and significant use of the whole plant by a diverse components of the biota matures, and waterbirds habituate waterbird assemblage, we anticipate that the proliferation to this protected wetland oasis amidst an otherwise densely of similar STPs in urban and peri-urban Ghana, most likely populated urban coastal zone of West Africa. However, the will contribute positively to waterbird conservation, as well persistence of diverse bird populations at similar STPs will 1 3 Wetlands (2021) 41:110 Page 13 of 15 110 depend on careful habitat management. Future long-term Tropical Ecology 49(2):199–209 ISSN 0564-3295. https:// trope studies and population monitoring that encompasses the full col. com/ pdf/ open/ PDF_ 49_2/1 1%2 0Ayna lem. pdf calendar year could decipher such interactive relationships. Beatty WS, Kesler DC, Webb EB, Raedeke AH, Naylor LW, Humburg DD (2014) The role of protected area wetlands in waterfowl habi- tat conservation: implications for protected area network design. Acknowledgements Firstly, great thanks to Mr. Alfred Ali Nuoh, Cen- Biological Conservation 176:144–152. https://d oi. org/1 0.1 016/j. tre for African Wetlands, University of Ghana, who assisted in the iden- biocon.2 014. 05.0 18 tification and counting of birds at the LSTP. Secondly, we are grate- Belle JA, Andries J, Nacelle C (2018) Managing wetlands for disas- ful to the Managing Director, Mr. Deo Datus Appiah, Val Terra Ltd. ter risk reduction: a case study of the eastern Free State, South (Tema), in liaison with the Accra Metropolitan Assembly, for granting Africa. Jamba: J Disas Risk Stud 10(1):a400. https:// doi. org/ 10. permit, as well as encouragement of the work. Also great thanks to an 4102/ jamba. v10i1. 400 anonymous editorial assistant, and two reviewers for their constructive Davidson NC (2014) How much wetland has the world lost? Long-term criticism and editing of the manuscript. Finally, thanks to Dr. William and recent trends in global wetland area. Marine and Freshwater Gblerkpor for assistance with drone imaging at the LSTP. Research 65(10):934–941. https://d oi. org/ 10. 1071/ MF1417 3 Dayathilake D, Lokupitiya E, Wijeratne V (2021) Estimation of soil Code Availability Not applicable. carbon stocks of urban freshwater wetlands in the Colombo Ram- sar wetland city and their potential role in climate change mitiga- Authors’ Contributions Both authors contributed to the study, and read tion. Wetlands 41:29. https://d oi.o rg/1 0.1 007/s 13157-0 21-0 1424-7 and approved the final manuscript; LHH conceptualised, designed and De Troyer N, Mereta ST, Goethals PLM, Boets P (2016) Water quality supervised the study, participated in the initial data collection, per- assessment of streams and wetlands in a fast growing east African formed the majority of data analysis, initiated the draft, and prepared city. Water 8(4):123. https:// doi. org/ 10.3 390/ w8040 123 the final manuscript; CCC conducted the majority of data collection, Dean WRJ, Milton SJ, Forsyth HP, Tissiman DR (2015) Fluctuations in and made contributions to material preparation and data analysis. bird numbers on sewage treatment ponds in an arid environment, South Africa. Ostrich 86(1-2):145–153. https:// doi. org/ 10. 2989/ 003065 25. 2015. 102955 9 Funding This study did not receive any funding from any source or Dixon A, Wood A, Hailu A (2021) Wetlands in Ethiopia: lessons from institution. 20 years of research, policy and practice. Wetlands 41:20. https:// doi.o rg/ 10.1 007/ s13157-0 21-0 1420-x Data Availability The datasets used and/or analysed during the cur- Douglas I, Alam K, Maghenda M, Mcdonnell Y, Mclean L, Campbell J rent study are available from the corresponding author on reasonable (2008) Unjust waters: climate change, flooding and the urban poor request. in Africa. Environment and Urbanization 20(1):187–205. https:// doi.o rg/1 0. 1177/ 095624 78080 89156 Declarations Dowsett-Lemaire F, Dowsett RJ (2014) The birds of Ghana - a hand- book and atlas. Tauraco Press, Liège, p 714 Dudgeon D, Arthington AH, Gessner MO, Kawabata Z-I, Knowler DJ, Conflict of Interest The authors declare that they have no conflict of Lévêque C, Naiman RJ, Prieur-Richard A-H, Soto D, Stiassny interest. MLJ, Sullivan CA (2006) Freshwater biodiversity: importance, threats, status and conservation challenges. Biological Reviews Ethics Approval Prior consent and permissions were obtained from 81:163–182. https:// doi. org/ 10. 1017/ S14647 9310 500695 0 respective authorities. Erwin MR (2002) Managing wetlands for waterbirds: Integrated approaches. Waterbirds 25(Spec Publ 2):5–12 https:// www.j stor. Consent to Participate Not applicable. org/s table/1 5224 47 Erwin KL (2009) Wetlands and global climate change: the role of Consent for Publication Not applicable. wetland restoration in a changing world. Wetlands Ecology and Management 17:71. https://d oi. org/ 10.1 007/ s11273- 008- 9119-1 Finlayson CM (2012) Forty years of wetland conservation and wise use. Aquatic Conservation: Marine and Freshwater Ecosystems References 22(2):139–143. https://d oi.o rg/1 0. 1002/ aqc.2 233 Froneman A, Mangnall MJ, Little RM, Crowe TM (2001) Waterbird Adams WM (1993) Use of wetlands and sustainable development in assemblages and associated habitat characteristics of farm ponds West Africa. The Geographical Journal 159(2):209–218 https:// in the Western cape, South Africa. Biodiversity and Conservation www. jstor. org/s table/ 345141 2 10:251–270. https://d oi. org/1 0. 1023/A: 10089 04421 948 Afdhal B, Charfi-Cheikhrouha F, Moali A (2012) Tunisian man-made Gbogbo F (2007a) Impact of commercial salt production on wetland wetlands as alternative habitats for waterbirds and their role for quality and waterbirds on coastal lagoons in Ghana. Ostrich conservation. African Journal of Ecology 51:154–163. https://d oi. 78(1):81–87. https://d oi.o rg/1 0.2 989/O STRIC H.2 007.7 8.1.1 2.5 6 org/ 10. 1111/ aje. 12022 Gbogbo F (2007b) The importance of unmanaged coastal wetlands to Ashkenazi S (2001) Long-term trends in the breeding populations of waterbirds at coastal Ghana. African Journal of Ecology 45:599– waterbirds (1951-1985) at a sewage treatment plant. Ostrich 72(1- 606. https:// doi. org/ 10.1 111/j. 1365- 2028.2 007. 00778.x 2):10–19. https://d oi.o rg/1 0.2 989/ 00306 520109 4852 77 Gbogbo F, Attuquayefio DK (2010) Issues arising from changes in Attuquayefio DK, Gbogbo F (2001) Prospects of conserving wetlands waterbird population estimates in coastal Ghana. Bird Popula- along the Mukwe lagoon at Nungua in the Greater Accra region of tions 10:79–87 https:// www. birdp op. org/ docs/ journ als/ Volume- Ghana. West African Journal of Applied Ecology 2:65–75. https:// 10/ BPJ10- 09_ Gbogbo_ and_ Attuq uayefi o. pdf doi.o rg/ 10.4 314/w ajae.v 2i1. 45564 Gbogbo F, Oduro W, Oppong SK (2008) Nature and pattern of lagoon Aynalem S, Bekele A (2008) Species composition, relative abundance fisheries resource utilisation and their implications for waterbird and distribution of bird fauna of riverine and wetland habitats management in coastal Ghana. African Journal of Aquatic Science of Infranz and Yiganda at southern tip of Lake Tana, Ethiopia. 33(3):211–222. https://d oi.o rg/ 10.2 989/ AJAS. 2008. 33.3. 3. 615 1 3 110 Page 14 of 15 Wetlands (2021) 41:110 Gbogbo F, Oduro W, Oppong SK (2009) Response of waterbird spe- Environment 646:84–92. https://d oi.o rg/1 0.1 016/j.s citot env.2 018. cies to fluctuating water levels in tropical coastal wetlands. Afri- 07. 265 can Journal of Ecology 48:637–643. https:// doi.o rg/ 10. 1111/j. Mitchell SA (2013) The status of wetlands, threats and the predicted 1365-2 028.2 009. 01156.x effect of global climate change: the situation in sub-Saharan Giosa E, Mammides C, Zotos S (2018) The importance of artifi- Africa. Aquatic Sciences 75:95–112. https:// doi. org/ 10. 1007/ cial wetlands for birds: a case study from Cyprus. PLoS One s00027-0 12-0 259-2 13(5):e0197286. https://d oi.o rg/1 0.1 371/j ourna l.p one.0 19728 6 Murray CG, Hamilton AJ (2010) Perspectives on wastewater treatment Hamdi N, Ismail-Hamdi S (2014) Testing whether artificial wetlands wetlands and waterbird conservation. Journal of Applied Ecology as habitats for waterbirds are good alternatives to natural wet- 47:976–985. https://d oi. org/ 10. 1111/j. 1365- 2664.2 010. 01853.x lands: a case study of dams located in northern Tunisia. Vie et Murray CG, Loyn RH, Kasel S, Hepworth G, Stamation K, Hamilton Milieu 64:47–57 ISSN 0240-8759. https:// www. cabdi rect. org/ AJ (2012) What can a database compiled over 22 years tell us cabdir ect/a bstr act/2 01533 73721 about the use of different types of wetlands by waterfowl in south- Harebottle DM, Williams AJ, Weiss Y, Tong GB (2008) Waterbirds eastern Australian summers? Emu 112:209–217. https://d oi. org/ at Paarl waste water treatment works, South Africa, 1994– 10.1 071/M U110 70 2004: seasonality, trends and conservation importance. Ostrich Murray CG, Kasel S, Szantyr E, Barratt R, Hamilton AJ (2014) Water- 79(2):47–163. https://d oi.o rg/ 10.2 989/ OSTRI CH. 2008.7 9.2.4 . bird use of different treatment stages in waste-stabilisation pond 578 systems. Emu 114:30–40. https:// doi. org/1 0. 1071/M U121 21 Harrison JA, Williams AJ, MacIver M (2010) Breeding site selection Nixon SW, Buckley BA, Granger SL, Entsua-Mensah M, Ansa-Asare by colonial waterbirds given various combinations of constructed O, White MJ, McKinney RA, Mensah E (2007) Anthropogenic or natural alternatives over a 10-year period. Ostrich 81(3):197– enrichment and nutrients in some tropical lagoons of Ghana, 203. https:// doi.o rg/1 0. 2989/ 003065 25.2 010. 519535 West Africa. Ecological Applications 17(5):Supplement:S144– Holbech LH, Gbogbo F, Aikins TK (2018) Abundance and prey cap- Supplement:S164. https:// doi.o rg/ 10. 1890/ 05- 0684.1 ture success of common terns (Sterna hirundo) and pied king- Ntiamoa-Baidu Y (1991) Seasonal changes in the importance of coastal fishers (Ceryle rudis) in relation to water clarity in south-east wetlands in Ghana for wading birds. Biological Conservation coastal Ghana. Avian Research 9:25. https:// doi. org/ 10. 1186/ 57(2):139–158. https:// doi. org/ 10. 1016/0 006-3 207(91) 90135-V s40657- 018-0 116-7 Ntiamoa-Baidu Y, Piersma T, Wiersma P, Poot M, Battley P, Gordon Hsu C-B, Hsieh H-L, Yang L, Wu S-H, Chang J-S, Hsiao S-C, Su H-C, C (1998) Habitat selection, daily foraging routines and diet of Yeh C-H, Ho Y-S, Lin H-J (2011) Biodiversity of constructed waterbirds in coastal lagoons in Ghana. Ibis 140:89–103. https:// wetlands for wastewater treatment. Ecological Engineering doi.o rg/ 10. 1111/j.1 474-9 19X.1 998. tb045 45.x 37(10):1533–1545. https://d oi.o rg/1 0.1 016/j.e colen g.2 011.0 6.0 02 O’Connell M (2000) Threats to waterbirds and wetlands: implica- Jost L (2006) Entropy and diversity. Oikos 113(2):363–375. https://d oi. tions for conservation, inventory and research. Wildfowl 51:1–15 org/1 0.1 111/j. 2006. 0030- 1299.1 4714.x https://w ildfo wl.w wt.o rg.u k/i ndex.p hp/w ildfo wl/a rticl e/v iew/1 076 Jost L, Chao A, Chazdon RL (2011) Compositional similarity and beta Okes NC, Hockey PAR, Cumming GS (2008) Habitat use and life his- (ß) diversity. In: Magurran AE, McGill BJ (eds) Biological diver- tory as predictors of bird responses to habitat change. Conserva- sity - frontiers in measurement and assessment, 1st edn. Oxford tion Biology 22(1):151–162. https://d oi.o rg/1 0.1 111/j.1 523-1 739. University Press, New York, pp 66–84 2007. 00862.x Junk WJ, An S, Finlayson CM, Gopal B, Květ J, Mitchell SA, Mitsch Otieno NE, Mutati AS, Akoth C, Ogwanjg D, Mwinami T, Alaro P, WJ, Robarts RD (2013) Current state of knowledge regarding the Njoka J (2015) Role of invertebrate prey abundance on waterbird world’s wetlands and their future under global climate change: a distribution across rice field growth stages in Western Kenya. synthesis. Aquatic Sciences 75:151–167. https://d oi.o rg/1 0.1 007/ Waterbirds 38(1):47–57. https:// doi. org/ 10. 1675/ 063. 038. 0107 s00027- 012-0 278-z Runge CA, Watson JEM, Butchart SHM, Hanson JO, Possingham Keddy PA, Fraser LH, Solomeshch AI, Junk WJ, Campbell DR, Arroyo HP, Fuller RA (2015) Protected areas and global conservation of MTK, Alho CJR (2009) Wet and wonderful: the world’s largest migratory birds. Science 350(6265):1255–1258. https:// doi. org/ wetlands are conservation priorities. BioScience 59(1):39–51. 10. 1126/ scien ce. aac91 80 https://d oi.o rg/1 0.1 525/b io. 2009.5 9.1.8 Santoul F, Mastrorillo S (2004) Gravel pits as new wetlands for the Lit- Kivaisi AK (2001) The potential for constructed wetlands for waste- tle grebe Tachybaptus ruficollis. Vie et Milieu 54(1):31–36 https:// water treatment and reuse in developing countries: a review. Eco- hal. sorbon ne- univer site. fr/h al-0 32179 88/d ocum ent logical Engineering 16:545–560. https:// doi.o rg/1 0. 1016/S 0925- Scholz M, Lee B-h (2005) Constructed wetlands: a review. Interna- 8574(00) 00113-0 tional Journal of Environmental Studies 62(4):421–447. https:// Kleijn D, Cherkaoui I, Goedhart PW, Hout J, Lammertsma D, Fuller doi. org/ 10. 1080/0 02072 3050 011978 3 R (2014) Waterbirds increase more rapidly in Ramsar-designated Schuyt KD (2005) Economic consequences of wetland degradation for wetlands than in unprotected wetlands. Journal of Applied Ecol- local populations in Africa. Ecological Economics 53:177–190. ogy 51(2):289–298. https://d oi.o rg/1 0.1 111/1 365- 2664. 12193 https:// doi.o rg/1 0. 1016/j.e colec on.2 004.0 8.0 03 Knapp S, Schmauck S, Zehnsdorf A (2019) Biodiversity impact of Shokoufeh S, Almuktar SAAAN, Scholz M (2021) Impact of climate green roofs and constructed wetlands as progressive eco-technol- change on wetland ecosystems: a critical review of experimental ogies in urban areas. Sustainability 11(20):5846. https://d oi.o rg/ wetlands. Journal of Environmental Management 286:112160. 10.3 390/ su1120 5846 https://d oi.o rg/1 0.1 016/j.j envm an.2 021. 112160 Lamptey AM, Ofori-Danson PK (2014) Review of the distribution of Sutherland WJ, Alves JA, Amano T, Chang CH, Davidson NC, Max waterbirds in two tropical coastal Ramsar lagoons in Ghana, West Finlayson C, Gill JA, Gill RE, González PM, Gunnarsson TG, Africa. West African Journal of Applied Ecology 22(1):77–91 Kleijn D, Spray CJ, Székely T, Thompson DBA (2012) A hori- eISSN: 0855-4307. https:// www. ajol. info/ index. php/ wajae/ artic zon scanning assessment of current and potential future threats to le/v iew/1 08001 migratory shorebirds. Ibis 154:663–679. https://d oi.o rg/1 0.1 111/j. López-Perea JJ, Laguna C, Jiménez-Moreno M, Martín-Doimeadios 1474-9 19X. 2012. 01261.x RCR, Feliu J, Mateo R (2019) Metals and metalloids in blood Uluocha NO, Okeke IC (2004) Implications of wetlands degradation and feathers of common moorhens (Gallinula chloropus) from for water resources management: lessons from Nigeria. GeoJour- wetlands that receive treated wastewater. Science of the Total nal 61:151–154. https:// doi.o rg/ 10.1 007/ s10708-0 04- 2868-3 1 3 Wetlands (2021) 41:110 Page 15 of 15 110 van Biervliet O, McInnes RJ, Lewis-Phillips J, Tosney J (2020) Can Plateau Lakes. Wetlands 36:1087–1095. https:// doi.o rg/ 10. 1007/ an integrated constructed wetland in Norfolk reduce nutrient con- s13157-0 16-0 823-y centrations and promote in situ bird species richness? Wetlands Wiegleb G, Dahms H-U, Byeon WI, Choi G (2017) To what extent can 40:967–981. https:// doi. org/ 10. 1007/ s13157- 019- 01247-7 constructed wetlands enhance biodiversity? International Journal Verhoeven JTA, Arheimer B, Yin C, Hefting MM (2006) Regional of Environmental Science and Development 8(8):561–569. https:// and global concerns over wetlands and water quality. Trends in doi.o rg/1 0.1 8178/ ijesd. 2017.8.8 .1 016 Ecology & Evolution 21(2):96–103. https://d oi.o rg/1 0.1 016/j.t ree. Willoughby N, Grimble R, Ellenbroek E, Danso E, Amatekpor J (2001) 2005.1 1. 015 The wise use of wetlands: identifying development options for Vickery JA, Ewing SR, Smith KW, Pain DJ, Bairlein F, Škorpilová Ghana’s coastal Ramsar sites. Hydrobiologia 458:221–234. J, Gregory RD, Fox T (2014) The decline of afro-Palaearctic https:// doi. org/1 0. 1023/A:1 01315 8329 107 migrants and an assessment of potential causes. Ibis 156:1–22. Wymenga E, Zwarts L (2010) Use of rice fields by birds in West Africa. https:// doi. org/ 10. 1111/ ibi. 12118 Waterbirds 33(special Publication 1):97–104. https:// doi.o rg/ 10. Wang H, Wang T, Zhang B, Li F, Toure B, Omosa IB, Chiramba T, 1675/ 063. 033. s107 Abdel-Monem M, Pradhan M (2014) Water and wastewater treat- ment in Africa - current practices and challenges. Clean: Soil, Publisher’s Note Springer Nature remains neutral with regard to Air, Water 42:1029–1035. https://d oi.o rg/1 0.1 002/c len.2 01300 208 jurisdictional claims in published maps and institutional affiliations. Wang R, Wu F, Chang Y, Yang X (2016) Waterbirds and their habitat utilization of artificial wetlands at Dianchi Lake: implication for waterbird conservation in Yunnan–Guizhou 1 3