Response of planktonic diatoms to eutrophication in Nyanza Gulf of Lake Victoria, Kenya

Simiyu, Benard Mucholwa; Kurmayer, Rainer

doi:10.1016/j.limno.2022.125958

Cited by 9 publications

(6 citation statements)

References 33 publications

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“…Since the 1960s, 30%–50% of the oxygenated waters have disappeared, restricting the variety of creatures vulnerable to low oxygen levels (Mugidde et al., 2005). This is clear from Simiyu and Kurmayer's (2022) research that the majority of invertebrates have relocated from deep to intermediate and surface waters as a result of anoxia, leaving them exposed to selective fish predation. Several zooplankton species have also come under threat from pollution and changes in the phytoplankton's composition.…”

Section: Resultsmentioning

confidence: 99%

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Threats to aquatic biodiversity and possible management strategies in Lake Victoria

Muthoka,

Ogello,

Outa

et al. 2023

Aquaculture Fish & Fisheries

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Lake Victoria is the second‐largest freshwater lake in the world, with a surface area of 68,800 km2. The lake is rich in natural resources that are essential to the local economy and livelihoods. However, International Union for Conservation of Nature (IUCN) ranks 76% of freshwater species endemic to the Lake Victoria Basin as threatened with extinction. The biodiversity richness of the lake is still diminishing, and the risk of species extinction is increasing. Many species are yet to be identified, and thus the number of species threatened with extinction exceeds what is currently known. Furthermore, the lake is home to species that are found nowhere else on the planet, but its protection is never given the attention it needs. Genetic diversity loss is harmful to future populations and influences sustainability of the ecosystem. The decline in Lake Victoria's biodiversity is primarily attributed to various pressing issues, including water pollution, invasive species, climate change, overexploitation and the challenges stemming from high human population density. These problems are exacerbated by inadequate regulatory enforcement and a lack of comprehensive data and information to inform and guide conservation efforts. If these factors are not addressed, they may have a detrimental impact on Lake Biodiversity. This article aims to document the main threats to aquatic biodiversity as well as potential management strategies for preventing further losses of the aquatic biodiversity in Lake Victoria. The study recommends reviewing, bolstering and reinforcing the rules and regulations governing the extraction, accessibility and discharge of nutrients into the lake. The national governments should work with local governments, non‐governmental organizations and local people to safeguard and conserve the lake's biodiversity. The national governments of the riparian nations should also reserve funds each fiscal year specifically for research that would inform effective management measures to prevent further losses of the lake's biodiversity.

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Section: Resultsmentioning

confidence: 99%

“…and Cosmarium spp., as well as diatoms such as Aulocoseria spp. ( Aulacoseira agassizii and Aulacoseira nyassensis ), are reportedly highly vulnerable to excessive phosphorus (Simiyu & Kurmayer, 2022). Fish and invertebrates prefer these species because they have a high nutritional value.…”

Section: Resultsmentioning

confidence: 99%

Threats to aquatic biodiversity and possible management strategies in Lake Victoria

Muthoka,

Ogello,

Outa

et al. 2023

Aquaculture Fish & Fisheries

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“…Especially, Aulacoseira granulata (Ehrenberg) Simonsen, a globally distributed species within its genus, displays adaptability and tolerance to a broad spectrum of environmental conditions (Wang et al, 2015). Blooms of A. granulata are typically associated with eutrophication (Gomes, 2000;Kamenir et al, 2004;Lepistö et al, 2006), increased turbidity and nutrient availability (Simiyu and Kurmayer, 2022). The morphological variability of this taxon has also been analysed to investigate its relationship with freshwater environmental features, such as the species valve diameter and mantle height positively correlating with more than one nutrient component (Gómez et al, 1995;Mohanty et al, 2022;O'Farrell et al, 2001;Poulickova, 2003;Turkia and Lepistö, 1999;Wang et al, 2015), or mantle height/valve diameter (H/D) and surface area/volume (SA/V) ratios negatively related to lake water-level and mixing (O'Farrell et al, 2001;Wang et al, 2009Wang et al, , 2015.…”

Section: Introductionmentioning

confidence: 99%

Diatom-based indications of an environmental regime shift and droughts associated with seasonal monsoons during the Holocene in Biển Hồ maar lake, the Central Highlands, Vietnam

Đào-Trung,

Fukumoto,

Nguyễn-Thùy

et al. 2024

The Holocene

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The interactions of the different monsoon systems across Southeast Asia create extreme climate phenomena. Central Vietnam, located near the centre of this transitional region, has encountered numerous effects. As a result, its sediments from lakes or speleothems are valuable archives for interpreting past climate variability. However, there is still a lack of high-resolution paleoenvironmental and palaeoclimatic reconstructions during the Holocene in Vietnam. Our study presents a paleoenvironmental diatom-based record of sediment cores collected from Biển Hồ maar lake (14°03′N, 108°00′E) in the Central Highlands of Vietnam covering nearly the entire Holocene. Based on changes in diatom assemblages in the sediment sequence, we identified two periods of the Early Holocene (~11,700–7800 cal BP) and the Mid- to Late-Holocene (~7800–360 cal BP), which mark a remarkable shift in the environment around Biển Hồ. Alternations of key diatom species during the Early Holocene indicate intensity variations between water-mixing and thermal stratification mechanisms in meso-eutrophic conditions. During the Mid- to Late-Holocene, the complete dominance of Aulacoseira granulata var. granulata implies year-round destratification and intense mixing of the lake water column in a permanently eutrophic environment. Its morphological variability reveals intervals of dry environmental conditions driven by pronounced droughts across the Asian continent.

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“…To our knowledge, there have been few studies characterizing water column bacterial communities through 16S rRNA gene amplicon sequencing over the entire Winam Gulf, particularly at regular limnological monitoring sites. Primarily, characterization of cyanobacteria has been done through morphological classifications (Lung'Ayia et al, 2000 ; Simiyu & Kurmayer, 2022 ; Sitoki et al, 2012 ). There are limited molecular studies that have been done in Lake Victoria or the Winam Gulf.…”

Section: Introductionmentioning

confidence: 99%

Bacterial community and cyanotoxin gene distribution of the Winam Gulf, Lake Victoria, Kenya

Brown,

Barker,

Wagner

et al. 2024

Environ Microbiol Rep

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The Winam Gulf (Kenya) is frequently impaired by cyanobacterial harmful algal blooms (cHABs) due to inadequate wastewater treatment and excess agricultural nutrient input. While phytoplankton in Lake Victoria have been characterized using morphological criteria, our aim is to identify potential toxin‐producing cyanobacteria using molecular approaches. The Gulf was sampled over two successive summer seasons, and 16S and 18S ribosomal RNA gene sequencing was performed. Additionally, key genes involved in production of cyanotoxins were examined by quantitative PCR. Bacterial communities were spatially variable, forming distinct clusters in line with regions of the Gulf. Taxa associated with diazotrophy were dominant near Homa Bay. On the eastern side, samples exhibited elevated cyrA abundances, indicating genetic capability of cylindrospermopsin synthesis. Indeed, near the Nyando River mouth in 2022, cyrA exceeded 10 million copies L−1 where there were more than 6000 Cylindrospermopsis spp. cells mL−1. In contrast, the southwestern region had elevated mcyE gene (microcystin synthesis) detections near Homa Bay where Microcystis and Dolichospermum spp. were observed. These findings show that within a relatively small embayment, composition and toxin synthesis potential of cHABs can vary dramatically. This underscores the need for multifaceted management approaches and frequent cyanotoxin monitoring to reduce human health impacts.

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Response of planktonic diatoms to eutrophication in Nyanza Gulf of Lake Victoria, Kenya

Cited by 9 publications

References 33 publications

Threats to aquatic biodiversity and possible management strategies in Lake Victoria

Threats to aquatic biodiversity and possible management strategies in Lake Victoria

Diatom-based indications of an environmental regime shift and droughts associated with seasonal monsoons during the Holocene in Biển Hồ maar lake, the Central Highlands, Vietnam

Bacterial community and cyanotoxin gene distribution of the Winam Gulf, Lake Victoria, Kenya

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