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Article

Returners and New Arrivals After the Crash: Intermediate Hosts and Global Invaders Dominate Gastropod Fauna of Lake Naivasha, Kenya

by
Christian Albrecht
1,2,3,*,
John Kochey Kipyegon
4,
Annett Junginger
5,6 and
Catharina Clewing
1
1
Department of Animal Ecology & Systematics, Justus Liebig University Giessen, 35392 Giessen, Germany
2
Department of Biology, Mbarara University of Science and Technology, Mbarara P.O. Box 1410, Uganda
3
Center for International Development and Environmental Research (ZEU), Justus Liebig University Giessen, 35390 Giessen, Germany
4
Zoology Department, Invertebrate Zoology Section, National Museums of Kenya, Nairobi P.O. Box 40658-00100, Kenya
5
Department of Geosciences, Tuebingen University, 72074 Tuebingen, Germany
6
Senckenberg Center for Human Evolution and Paleoenvironment (SHEP), Tuebingen University, 72074 Tuebingen, Germany
*
Author to whom correspondence should be addressed.
Diversity 2025, 17(4), 265; https://doi.org/10.3390/d17040265
Submission received: 28 February 2025 / Revised: 31 March 2025 / Accepted: 5 April 2025 / Published: 9 April 2025
(This article belongs to the Special Issue Advances in Freshwater Mollusk Research)
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Abstract

:
Aquatic alien species (AAS) have had a major impact on freshwater ecosystems, including Lake Naivasha in Kenya. Here, the ecosystem has undergone tremendous changes and multiple species introductions over the past 100 years, and molluscs have experienced a major decline in species diversity. The East African Rift Lakes have experienced a steady rise in lake levels since 2010. We investigated the impact of recent ecosystem changes on the lakes’ molluscs by determining the current mollusc diversity and its composition. We also reconstruct the history of faunal change and turnover over the last 100 years and discuss the future of molluscs in the lake and the implications in a One Health context. The combined effects of rising water levels and the decline of the crayfish Procambarus clarkii are likely to be responsible for the resurgence of Lake Naivasha’s mollusc fauna. The current fauna consists of three global invaders of American origin, one of which is new to East Africa (Pseudosuccinea columella) and another of which has only recently begun to spread (Pomacea canaliculata). A further three species are native to Africa, two of which are known from historical records, while one is new to Lake Naivasha (Bulinus forskalii). All native species are of public health (Biomphalaria sudanica) and veterinary health (Bulinus tropicus, Bulinus forskalii) concern. The current biodiversity of molluscs has reached the same level as in historical times, but the species composition is remarkably different.

Graphical Abstract

1. Introduction

Aquatic alien species (AAS) have had a global impact on freshwater ecosystems, their diversity, food chains, functioning and ecosystem services [1]. Lakes, as often closed systems, are particularly vulnerable to the impacts of AAS. Lake Victoria in East Africa is a prime example for the multiple impacts of alien species introduction and overexploitation (e.g., [2,3]). Another lake in East Africa, Lake Naivasha, has become a well-studied example of the effects of so-called allodiversity [4].This lake is heavily impacted by a variety of human activities, and its food webs have been controlled by alien species for more than 50 years [2]. The evidence on the impacts of aquatic species in Lake Naivasha is based on introductions that began over 100 years ago. These include neutral effects and even the disappearance of some previously introduced species but also major ecological changes caused by individual species such as the red swamp crayfish Procambarus clarkia (Girard, 1852). Others, such as the common carp (Cyprinus carpio Linnaeus, 1758), benefit local people. Most introductions were from the Americas or were secondary [4]. Significant plant introductions to the lake include Pontederia crassipes Mart., 1823 (water hyacinth) and Salvinia molesta D.S. Mitch., 1972, which are among the worst invasive plant species worldwide [5]. These alien species often affect more than one ecosystem service, most often after active release into the lake. Most alien species in Lake Naivasha have negative impacts not only on the ecosystem but also on the riparian and dependent human populations [2,4].
Environmental changes have been monitored using various paleolimnological [6,7,8] and ecological proxies [2,9]. Pesticides and pollution with a range of toxic chemicals from intensive agricultural facilities originate in the immediate vicinity of flower farms located around the lake [10]. Pollution is accompanied by excessive water abstraction [11], the overexploitation of fish and other major impacts [2], leading to a decline in ecosystem health [12]. Ecological degradation continues, and no sustainable management system has been established, although attempts have been made [2,3].
Molluscs are an important component of freshwater lake ecosystems in Africa [13]. While the large lakes of the Western African Rift are comparatively well known for their mollusc diversity (e.g., [14,15,16,17]) and spectacular radiations (e.g., [18]), this is usually not the case for smaller lakes. There are far fewer examples of freshwater lakes in the Eastern Rift. Lake Naivasha is a notable exception, as its mollusc fauna has been studied over the last 100 years [13,19,20,21]. This lake was recognised due to the disappearance of the native mollusc fauna in the 1980s [13]. The presence of a single snail, the globally invasive Physella acuta (Draparnaud, 1805), was recognised early [4]. This species has been the only surviving snail in the lake for decades [4,13,22].
The East African Rift Lakes have experienced a steady rise in lake levels since 2010, leading to major flooding with drastic consequences for the people living along the lakes [23]. By 2020, lake levels had peaked in many lakes, mostly due to excessive rainfall [23]. In the Kenyan Rift Lakes, a new drastic rise was observed throughout 2024 (A.J., C.A. pers. obs.). Rising lake levels have potentially catastrophic ecological consequences, for example, through the reconnection of alkaline and freshwater lakes in Kenya [24]. The associated flooding could create new habitats and expand existing habitats for freshwater organisms. It is therefore interesting to study the consequences of ecosystem changes. Macrobenthic organisms, especially invasive molluscs, are known for their colonisation potential and (passive) dispersal capacity [25]. Lake Naivasha, with its depauperate mollusc fauna, is an ideal model case to test the impact of recurrent lake-level rise events in African rift lakes on invasive species and biomedically relevant taxa.
Based on a lake-wide sampling, including tributaries and surrounding water bodies, conducted in December 2024, we (1) determine the current mollusc diversity and its composition. By reviewing previous records, we (2) reconstruct the history of faunal change and turnover over the last 100 years or so. Finally, we (3) discuss the future of molluscs in the lake and the implications in a One Health context, i.e., considering the health of people, animals and the environment.

2. Material & Methods

2.1. Study Area

Lake Naivasha is one of the few freshwater lakes in the Central Kenya Rift. It is a closed-basin, high-altitude lake (about 1890 m a.s.l.) and an important RAMSAR site [2]. The surface area varies from about 110 to 170 km2 [26]. Lake Naivasha consists of a main body of water (Figure 1). Lake Oloidien (Oloiden) is a partially separated extension to the southwest of the main Lake Naivasha [26]. Another embayment to the south-east connects the main lake to a former volcanic crater (Crater Lake or Crescent Island Bay; Figure 1).
The lake has undergone major climatic changes over hundreds of years [6]. These natural climatic variations affecting the lake occurred mainly up to 1950 AD. In the period since 1950, strong effects of anthropogenic activities have contributed to the natural impacts [7]. Currently, the catchment is highly important for the supply of drinking water to the towns of Nakuru County and irrigation water for the nationally important industries of horticulture, fisheries and power generation.

2.2. Field Sampling

Field sampling in Lake Naivasha was carried out over two days in February 2010, one day in August 2021 and five days in 2024 (Figure 1). Van Veen grabs and triangular dredges were used to sample the lake’s offshore soft substrata. Samples from the shore (0–0.5 m depth) and tributaries were collected using a scoop net (diameter: 20 cm, mesh size: 1 mm) or by hand picking from hard substrates or macrophytes. Sites were selected along the shoreline and tributaries to reflect different microhabitat types (Figure 2).
The water depth, geographic coordinates and substrate type (vegetation, rocks, stones, sand, mud, detritus, sapropel, artificial substrates) of each site were recorded (Table 1). All samples were preserved in 80% ethanol and labelled accordingly. The material is stored at the Systematics and Biodiversity Collection of the University of Giessen (UGSB), Germany. Specimens were identified to species level where possible, based on shell morphology according to [13]. For each site, two specimens of each species were selected and photographed using a Keyence digital microscope system (KEYENCE VHX-2000; Keyence Deutschland GmbH, Neu-Isenburg, Germany) prior to laboratory processing.
The Global Biodiversity Information Facility (GBIF) and the collections of the National Museums of Kenya, Nairobi, were also consulted for potential unpublished historical records of molluscs from Lake Naivasha.

2.3. DNA-Barcoding

Initial species identification followed traditional shell parameters [13]. Given the plasticity of shells and the virtual impossibility of distinguishing some species using only morphology, we used a DNA barcoding approach using partial sequences of cytochrome c oxidase subunit I (COI). We selected two specimens from each pre-identified species for DNA barcoding. Genomic DNA was extracted from a small piece of foot muscle using the CTAB protocol of [27]. The DNA amplification of the COI was performed according to the procedures described in [28]. Sanger sequencing was performed on an ABI 3730xl DNA analyser using the BigDye Terminator Kit (Life Technologies, LGC Genomics GmbH, Berlin, Germany). All new sequences were deposited in NCBI GenBank (GenBank accession numbers: PV350789–PV350799). The sequences obtained were compared to the NCBI GenBank nucleotide database using BLAST (BLASTn suite: megablast) to find the most similar sequences [29]. BLAST hits were sorted by maximum score (default setting), and the top two hits for each of our samples were selected.

3. Results

3.1. Species Diversity and Distribution

The current mollusc fauna of Lake Naivasha consists of at least six species (Table 1). Physella acuta is a long-established global invader, while Pseudosuccinea columella (Say, 1817) and Pomacaea canaliculata (Lamarck, 1822) are new arrivals to the lake. Both species are also global invaders. The other three pulmonate species found are native African species, Biomphalaria cf. sudanica, Bulinus tropicus (Krauss, 1848) and Bulinus forskalii (Ehrenberg, 1831). While Biomphalaria cf. sudanica and Bulinus tropicus are part of the original fauna historically known from Lake Naivasha, Bulinus forskalii is a new arrival. However, Bulinus tropicus was found in a nearby tributary a few meters from the inflow rather than in the lake itself. No snails were found in the main tributaries to the north of the lake or on the lake’s soft substrata.
The barcoding results confirm the original identifications and partly indicate biogeographical affinities of the Lake Naivasha populations (Table 2). Pomacea canaliculata was identical to haplotypes from Malaysia, whereas Physella acuta haplotypes were identical to published sequences from Australia and Greece. Pseudosuccinea columella haplotypes were identical to those from Australia and Argentina. Bulinus forskalii was most closely matched with samples from Zimbabwe and Kenya, and Bulinus tropicus with regional samples from Kenya (Table 2). Biomphalaria cf. sudanica was almost identical to samples from Lake Victoria (Tanzanian and Kenyan parts).
Diversity 17 00265 g002
Figure 2. Impressions of Lake Naivasha. Southwestern shoreline without macrophytes in February 2010 (A) in contrast to August 2021 (B). Potential transmission site for snail-borne diseases along the southern shoreline (C), floating Pontederia mats at Elsamere in December 2024 (D), the northern tributaries of Lake Naivasha did not support live mollusc populations in 2024 (E), high lake levels have led to a significant expansion of littoral habitat and the submergence of shoreline vegetation over the last decade (F), shoreline properties and facilities have been submerged due to recurrent flooding (G). All images taken by C.A. except E (image by Namakau Muyumbana).
Figure 2. Impressions of Lake Naivasha. Southwestern shoreline without macrophytes in February 2010 (A) in contrast to August 2021 (B). Potential transmission site for snail-borne diseases along the southern shoreline (C), floating Pontederia mats at Elsamere in December 2024 (D), the northern tributaries of Lake Naivasha did not support live mollusc populations in 2024 (E), high lake levels have led to a significant expansion of littoral habitat and the submergence of shoreline vegetation over the last decade (F), shoreline properties and facilities have been submerged due to recurrent flooding (G). All images taken by C.A. except E (image by Namakau Muyumbana).
Diversity 17 00265 g002
Table 2. BLAST (blastn) results of the COI partial sequencing including species name, country (in brackets), accession number, and % identity (in squared brackets). In addition, shell images of the processed specimens are shown for each taxon (invasive species are marked with a red exclamation mark).
Table 2. BLAST (blastn) results of the COI partial sequencing including species name, country (in brackets), accession number, and % identity (in squared brackets). In addition, shell images of the processed specimens are shown for each taxon (invasive species are marked with a red exclamation mark).
FamilySpeciesSpecimen ImageVoucher No.LocationBLAST Results 1
AmpullariidaePomacea canaliculata
(Lamarck, 1822)		Diversity 17 00265 i001UGSB 31089 *LN02Pomacea canaliculata (MYS)
MG230745 [100%]
Pomacea canaliculata (MYS)
MG230743 [100%]
UGSB
31090		LN02Pomacea canaliculata (MYS)
MG230745 [100%]
Pomacea canaliculata (MYS)
MG230743 [100%]
BulinidaeBulinus forskalii
(Ehrenberg, 1831)		Diversity 17 00265 i002UGSB
31085		LN01Bulinus forskalii (ZWE)
PP468526 [99.8%]
Bulinus forskalii (KEN)
OP233129 [99.7%]
UGSB 31086 *LN01Bulinus forskalii (ZWE)
PP468526 [99.8%]
Bulinus forskalii (KEN)
OP233129 [99.7%]
Bulinus cf. tropicusDiversity 17 00265 i003UGSB 31093 *LN03Bulinus tropicus (KEN)
ON112314 [100%]
Bulinus tropicus (KEN)
OP233128 [99.7%]
UGSB
31094		LN03Bulinus tropicus (KEN)
ON112314 [100%]
Bulinus tropicus (KEN)
OP233128 [99.7%]
LymnaeidaePseudosuccinea columella
(Say, 1817)		Diversity 17 00265 i004UGSB 31083 *LN01Pseudosuccinea columella (AUS)
MG976151 [100%]
Pseudosuccinea columella (ARG)
MW830999 [100%]
UGSB
31084		LN01Pseudosuccinea columella (AUS)
MG976151 [100%]
Pseudosuccinea columella (ARG)
MW830999 [100%]
PhysidaePhysella acuta
(Draparnaud, 1805)		Diversity 17 00265 i005UGSB 31091 *LN02Physella aff. acuta (AUS)
MG976187 [100%]
Physella acuta (GRC)
KF737936 [100%]
PlanorbidaeBiomphalaria cf. sudanicaDiversity 17 00265 i006USGB 31087 *LN01Biomphalaria sp. (TZA)
KY745885 [99.7%]
Biomphalaria cf. sudanica (UGA)
HM768904 [99.7%]
UGSB
31088		LN01Biomphalaria sp. (?)
HM769143 [99.8%]
Biomphalaria sp. (TZA)
KY745885 [99.7%]
* specimen voucher image shown, note that these images are not to scale; 1 country codes used: ? = unclear, AUS = Australia, ARG = Argentina, GRC = Greece, MYS = Malaysia, ZWE = Zimbabwe, KEN = Kenya, TZA = Tanzania, UGA = Uganda.

3.2. Mollusk Faunal Change

The original fauna of the lake in the pre-Mid-1980s consisted of a lymnaeid species, Radix natalensis (Krauss, 1848), and the planorbid species Afrogyrorbis natalensis (Krauss, 1848) and Biomphalaria sudanica (E. von Martens, 1870), as well as Bulinus tropicus (Bulinidae). Sphaeriid clams were recorded in the early 1970s, and the freshwater limpet Ferrissia sp. in 1982/83 (Figure 3), as well as Bulinus tropicus, Biomphalaria sp., Physella acuta, and Radix natalensis around 1982 (Figure 3, Table 3). By the mid-1980s the native fauna had been drastically reduced. Basically, only Physella acuta, an invasive species present since 1950, was found. With the exception of Bulinus truncatus found on Crescent Island in 1987/88, Physella acuta remained the only mollusc in the lake and we found it exclusively in 2010. It was not until the lake level rose in 2021 that Physella acuta and a new invasive species, Pseudosuccinea columella, were recorded in the eastern part of the lake (Figure 1), before the four additional species were discovered in 2024. The current ratio of native to invasive species is therefore 50/50. Three species are completely new to the lake fauna (Pomacea canaliculata, Pseudosuccinea columella, Bulinus forskalii). No bivalves were recorded in the recent survey, nor were any of the historical faunal elements (Radix natalensis, Afrogyrorbis natalensis, Ferrissia sp., Sphaeriidae).
Table 3. Historical records and faunal change of molluscs in Lake Naivasha, Kenya.
Table 3. Historical records and faunal change of molluscs in Lake Naivasha, Kenya.
PublicationTime of CollectionSpecies Found *
[19]1929Radix natalensis, Bulinus tropicus, Afrogyrorbis natalensis
[30]1971–1973Sphaeriidae
[20]1982Bulinus tropicus, Radix natalensis, Biomphalaria sp.
[31]1987/88Bulinus truncatus
[21]1982/1983
1984		Radix natalensis, Afrogyrorbis natalensis, Physella acuta, Ferrissia sp.
Physella acuta, Ferrissia sp.
[32]N/ABulinus tropicus
[13]1970s
1984/85		Physella acuta, Bulinus tropicus, Radix natalensis, Biomphalaria sudanica, Afrogyrorbis natalensis
Physella acuta
[22]2010Physella acuta
* Some species names have been adapted to the recent nomenclature.

4. Discussion

Following the documented return of native snail species to Lake Naivasha and the establishment of three globally invasive gastropod species, we discuss the causes of the decline and the observed faunal changes. We also interpret this for other lakes throughout the Rift and for mitigation and management strategies for Lake Naivasha.

4.1. Drivers of Decline

The crayfish invasion (Procambarus clarkii) led to a significant decline in native plant species [4]. Blue water-lily (Nymphaea nouchalii Burm. Fil, 1768) and other floating-leaved and submerged macrophytes declined in parallel with the expansion of the crayfish population between 1974 and 1980 (Figure 3). This loss of native vegetation disrupted the classic zonation of vascular plants from land to open water, altering the ecological structure of the lake and in particular the habitat of most of the native molluscs. These either lived in direct association with the plants or in less oxygen-depleted bottom habitats. The water quality of Lake Naivasha has deteriorated significantly due to a number of factors. The main causes include unsustainable agricultural practices and pollution from pesticides, chemicals and sewage from flower farms along the shorelines. At the same time, excessive water withdrawals for flower farming and domestic use, combined with occasional droughts, led to a sharp decline in water levels from 1980 to around 2010 (Figure 3). Recent studies indicate that Lake Naivasha is currently moving from a eutrophic to a hypertrophic state, especially during the rainy season [9]. The accidental introduction of water hyacinth in 1988 has further exacerbated the lake’s problems, leading to oxygen depletion as the dense mats of water hyacinth reduce dissolved oxygen levels, affecting benthic organisms such as molluscs. Although there are not many records from the mid-1980s to essentially 2024, the absence of molluscs other than Physella acuta coincides with well-documented changes in the lake. Direct pressure on mollusc populations resulted from the predatory behaviour of Procambarus clarkii, which feeds extensively on molluscs (e.g., [33]). A combination of habitat loss and degradation and predation stress likely have led to the decades of almost mollusc-free Lake Naivasha from mid-1980 to at least 2010, more likely towards the end of the decade.
Diversity 17 00265 g003
Figure 3. Changes in lake level, species invasions and mollusc dynamics in Lake Naivasha over the last 100 years. The presence of mollusc species is shown for native species (blue) and invasive species (red) (see Table 3 for details). Lake level data are from [34] for the period 1925–2021 and from the Database for Hydrological Time Series of Inland Waters (DAHITI), available at https://dahiti.dgfi.tum.de/en/13610/water-level-altimetry/ (accessed on 27 February 2025) for the period 2021–2025. Significant losses of native plants and introductions of aquatic plants are shown, as well as introduction dates for a non-native crayfish and selected fish species (compiled from [2,4]).
Figure 3. Changes in lake level, species invasions and mollusc dynamics in Lake Naivasha over the last 100 years. The presence of mollusc species is shown for native species (blue) and invasive species (red) (see Table 3 for details). Lake level data are from [34] for the period 1925–2021 and from the Database for Hydrological Time Series of Inland Waters (DAHITI), available at https://dahiti.dgfi.tum.de/en/13610/water-level-altimetry/ (accessed on 27 February 2025) for the period 2021–2025. Significant losses of native plants and introductions of aquatic plants are shown, as well as introduction dates for a non-native crayfish and selected fish species (compiled from [2,4]).
Diversity 17 00265 g003

4.2. Drivers of Revival of Mollusc Fauna

The water level of Lake Naivasha has been rising since 2010 due to hydro-meteorological and climatic variation [23]. This rise has led to the flooding of surrounding areas, (re)connection with Lake Oloidien, and a change in water quality from alkaline to fresh [26]. The rise in water level has not only increased the habitat for molluscs along the shallow littoral. It may also have had a dilution effect, improving the overall water quality but likely not yet the substrate structure, as indicated by the absence of molluscs from the lake’s interior. Rising water levels have contributed to an increase in vegetation. For example, water hyacinths (Pontederia crassipes) have spread extensively and cover large parts of the lake, especially near the mouth of the Malewa River and towards Lake Oloidien (CA, pers. obs. December 2024), and papyrus (Cyperus papyrus Linnaeus, 1753) growth has increased (CA, pers. observation). These plants provide habitat and, in the case of floating water hyacinth, means of the rapid dispersal and lake-wide distribution of snails, especially the pulmonates [5]. A direct link to Procambarus clarkii population declines was noted as early as 2000, when “aquatic snails were found in abundance on the north shore of Crescent Island during crayfish trawls in 2000, and in submerged aquatic vegetation in 2003, but not in late 1999” ([33], p. 198). In conclusion, Lake Naivasha’s ecosystem is undergoing significant changes due to rising water levels, affecting plant diversity, mollusc distribution and potentially predator populations. The combined effects of rising water levels and the decline of Procambarus clarkii are likely responsible for the revival of Lake Naivasha’s mollusc fauna. The current species richness of molluscs has reached the same level as in historical times; however, the species composition is remarkably different.

4.3. Implications for and Lessons Learnt from Mollusks

Today’s snail communities consist of global invaders, all of American origin. This does not mean that they came directly from these sources. Physella acuta has persisted since its first appearance in Lake Naivasha 75 years ago. It has a very complex invasion history in Africa, with multiple colonisations from different sources, reflected in genetic diversity [22]. A strikingly different pattern occurred with Pseudosuccinea columella and Pomacea canaliculata, both of which are genetically uniform [35,36]. Our samples from Lake Naivasha were consistent, with known global invasive haplotypes and the flash invasion type of colonisation [36]. To our knowledge, the population of Pseudosuccinea columella established in Lake Naivasha is the first record of this species in Kenya, and indeed in East Africa [37]. The veterinary and public health implications remain to be assessed, given the potential for Fasciola trematode transmission from Pseudosuccinea [38].
A major public health concern is the return of an intermediate host for intestinal schistosomiasis (Biomphalaria sudanica), a species involved in hotspots of schistosomiasis in East Africa (e.g., [39]). This revives concerns at Lake Naivasha that were raised in the 1960s and 70s [13,40]. It is also one of the highest elevation records of Biomphalaria snails in the region, which are generally predicted to expand with future climate change [41]. Extensive epidemiological studies around the basin are needed to determine the regional risk of increased human schistosomiasis (Figure 2). Although Bulinus tropicus and Bulinus forskalii are not intermediate hosts for Schistosoma haematobium (Bilharz, 1852), the cause of urogenital schistosomiasis, they are important hosts for a number of parasites of veterinary importance such as Schistosoma bovis Sonsino, 1876 [42,43]. This was also known from Lake Naivasha [20].
The apple snail Pomacea canaliculata is one of the most invasive snails in the world [44,45]. It was first found in Kenya in 2020 in the Mwea rice system and is currently spreading [46,47,48]. It is important to monitor its impact on the molluscs of Lake Naivasha, as the species may outcompete and predate native and non-native gastropods elsewhere [49].

5. Conclusions

The gastropod communities of Lake Naivasha reflect the dynamics of diversity change associated with changes in water levels. New species assemblages have formed over the years. Half of the current fauna now consists of alien species. Although it is not easy to compare Lake Naivasha with long-lived rift lakes such as those in the West African rift system, invasive snail species are also affecting the native fauna [28,50]. If changes in the lake’s ecosystem and functioning are accompanied by a facilitation of species introductions, there could be serious consequences for native and endemic communities and ecosystem health. Lake Naivasha remains a fascinating model lake for the study of human impacts and their interactions with natural phenomena of environmental change on decadal to millennial time scales. Mollusc communities in and around the lake should be monitored more closely, and a more detailed understanding of past dynamics could be achieved through the use of ancient environmental DNA.

Author Contributions

Conceptualization, C.A.; Methodology, C.A. and C.C.; Validation; Investigation, J.K.K., C.C. and C.A.; Data Curation, C.A. and C.C.; Writing—Original Draft Preparation, C.A. and A.J.; Writing—Review and Editing, A.J., J.K.K. and C.A.; Visualization, C.A., A.J. and C.C.; Funding Acquisition, C.A. and A.J. All authors have read and agreed to the published version of the manuscript.

Funding

Funding was provided by the German Research Foundation (DFG) to CA (AL 1076/14-1, AL1076/5-2) and to AJ (JU 2868/9-1). Additional support came from the “Senckenberg Green Heart of Africa” seed funds.

Data Availability Statement

Data are either in the article or deposited at NCBI GenBank.

Acknowledgments

Thies Geertz, Kathrin Bößneck and Ulrich Bößneck (†) supported the fieldwork in 2010. In 2024, participants of the Lake Naivasha Aquatic Biodiversity Workshop kindly supported fieldwork. The National Museums of Kenya (Nairobi) is gratefully acknowledged for facilitating the necessary National Commission for Science, Technology & Innovation (NACOSTI) permits. We gratefully acknowledge the German Research Foundation (DFG) and Senckenberg Frankfurt for their funding support.

Conflicts of Interest

The authors declare no conflict of interest.

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Diversity 17 00265 g001
Figure 1. Mollusc sampling in Lake Naivasha in 2010, 2021 and 2024. Sites where no molluscs were found are marked with a cross, while sites with mollusc populations are marked with a dot. The years of sampling are colour-coded. See Table 1 for details of the sites.
Figure 1. Mollusc sampling in Lake Naivasha in 2010, 2021 and 2024. Sites where no molluscs were found are marked with a cross, while sites with mollusc populations are marked with a dot. The years of sampling are colour-coded. See Table 1 for details of the sites.
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Table 1. Localities and occurrences of mollusc species in 2024.
Table 1. Localities and occurrences of mollusc species in 2024.
LocalityLoc. CodeCoordinatesEcological ConditionsSpecies Found
Lake Naivasha,
Olsurwa water pump		LN01−0.73191° N/36.283763° EShoreline with spring inflow, macrophytes and muddy substrates;
water parameters: pH 7.34, conductivity 534 yS/cm, TDS 267, PSU 0.26, oxygen 86.5%, temp. 20.6 °C		Pseudosuccinea columella
Bulinus forskalii
Biomphalaria cf. sudanica
Lake Naivasha, Kwamoya beachLN02−0.82738° N/36.34021° EShoreline, macrophytes, muddy substrate, water parameters: pH 7.45, conductivity 426 yS/cm, TDS 213, PSU 0.20, oxygen 87.8%, temp. 24.4 °CPhysella acuta
Pomacea canaliculata
Huruma stream,
Lake Naivasha tributary, western shore near Hurumua 		LN03−0.74626° N/36.27507° EFast flowing stream with few macrophytes, very turbid, water level high, water parameters: pH 7.74, conductivity 753 yS/cm, TDS 377, PSU 0.37, oxygen 76.3%, temp. 20.75Bulinus tropicus
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Albrecht, C.; Kipyegon, J.K.; Junginger, A.; Clewing, C. Returners and New Arrivals After the Crash: Intermediate Hosts and Global Invaders Dominate Gastropod Fauna of Lake Naivasha, Kenya. Diversity 2025, 17, 265. https://doi.org/10.3390/d17040265

AMA Style

Albrecht C, Kipyegon JK, Junginger A, Clewing C. Returners and New Arrivals After the Crash: Intermediate Hosts and Global Invaders Dominate Gastropod Fauna of Lake Naivasha, Kenya. Diversity. 2025; 17(4):265. https://doi.org/10.3390/d17040265

Chicago/Turabian Style

Albrecht, Christian, John Kochey Kipyegon, Annett Junginger, and Catharina Clewing. 2025. "Returners and New Arrivals After the Crash: Intermediate Hosts and Global Invaders Dominate Gastropod Fauna of Lake Naivasha, Kenya" Diversity 17, no. 4: 265. https://doi.org/10.3390/d17040265

APA Style

Albrecht, C., Kipyegon, J. K., Junginger, A., & Clewing, C. (2025). Returners and New Arrivals After the Crash: Intermediate Hosts and Global Invaders Dominate Gastropod Fauna of Lake Naivasha, Kenya. Diversity, 17(4), 265. https://doi.org/10.3390/d17040265

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