Did the loss of phytoplanktivorous fish contribute to algal blooms in the Mwanza Gulf of Lake Victoria?

Witte, Frans; Silsbe, Gregory M.; Hecky, Robert E.; Goudswaard, P.C.; Guildford, Stephanie J.; Kishe-Machumu, Mary A.; Wanink, Jan H.

doi:10.1007/s10750-011-0893-z

Cited by 19 publications

(13 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…They suggested that the destruction of these forms may have changed the phytoplankton and promoted the development of blue-green algal blooms. This was countered by Witte et al (2012), who concluded that the algal blooms of the 1980s were unlikely to have been caused by decreased phytoplankton grazing by fish. However, they reached this conclusion using a model on phytoplankton consumption rates of two species from Lake George, Uganda, where they fed almost exclusively on Microcystis (Moriarty and Moriarty 1973).…”

Section: Ecological Consequences Primary and Secondary Producersmentioning

confidence: 98%

Nile perch and the transformation of Lake Victoria

Taabu‐Munyaho

Marshall²,

Tómasson

et al. 2016

African Journal of Aquatic Science

View full text Add to dashboard Cite

The transformation of Lake Victoria that began in 1980 followed the population explosion of Nile perch Lates niloticus, causing the apparent extirpation of 500+ endemic haplochromine species and dramatic physico-chemical changes. Officially introduced in 1962-1963, but present earlier, the reasons for the long delay before its population exploded are discussed. The hypothesis that it occurred only after the haplochromine decline is evaluated, but haplochromines declined only after the Nile perch expansion began. The sudden eutrophication of the lake was attributed to Nile perch, but evidence of eutrophication from 1950 onwards led some researchers to conclude that it was the result of climatic changes. We conclude that the haplochromine destruction disrupted the complex food webs that existed prior to the upsurge of Nile perch. The depletion of fish biomass by Nile perch may have been the source of extra phosphorus responsible for the eutrophication of the lake. After the Nile perch explosion in 1980 the fish population came to be dominated by only three species, but fisheries productivity increased at least 10-fold. Fishing has caused demographic changes in Nile perch, which may have allowed some haplochromine species to recover. The condition of the lake appears to have stabilised since 2000, partly because the fish biomass has risen to at least 2 × 10 6 t, replacing the 'lost' biomass and restoring some ecosystem functioning.

show abstract

Section: Ecological Consequences Primary and Secondary Producersmentioning

confidence: 98%

Nile perch and the transformation of Lake Victoria

Taabu‐Munyaho

Marshall²,

Tómasson

et al. 2016

African Journal of Aquatic Science

View full text Add to dashboard Cite

show abstract

“…A one hour tow of a bottom otter trawl (head rope 25 m) contained on average 1140 kg of haplochromines, of which 27% (more than 100,000 individuals) were zooplanktivores (Goldschmidt et al 1993, Witte et al 2012b). During the 1980s it became clear that the ecosystem of Lake Victoria was subject to a perturbation of an enormous magnitude.…”

Section: Introductionmentioning

confidence: 99%

Two new species of zooplanktivorous haplochromine cichlids from Lake Victoria, Tanzania

Zeeuw¹,

Westbroek²,

Oijen³

et al. 2013

View full text Add to dashboard Cite

Two new species of zooplanktivorous haplochromine cichlids from Lake Victoria, Tanzania, are described and illustrated. These species closely resemble each other. Their affinities to other zooplanktivorous haplochromines from Lake Victoria are discussed. Haplochromis argens sp. n., which featured under nicknames (mainly Haplochromis “argens”) in more than 50 papers, was caught both in the Mwanza Gulf and the Emin Pasha Gulf, whereas Haplochromis goldschmidti sp. n. was only found in the Emin Pasha Gulf. Of the latter species only males are available, but it seems unlikely that it represents a case of male colour polymorphism as several presumably unrelated characters differ in sympatry between the two species, suggesting that there is no gene flow. Statistical analysis revealed that the overall difference between the two species is greater than that between the populations from the two locations. Body depth of the two species in sympatry in the Emin Pasha Gulf was more similar than that of Haplochromis goldschmidti sp. n. and the allopatric population of Haplochromis argens sp. n. from the Mwanza Gulf,which mayindicate an overall environmental effect. However, several measurements related to the width of snout and mouth differed more between the populations of the two species in sympatry than between the allopatric populations. In contrast to a group of zooplanktivorous species that recovered successfully after environmental changes in the lake, Haplochromis argens sp. n. is among a group that became extremely rare and probably is in danger of extinction; the conservation status of Haplochromis goldschmidti sp. n. is currently unknown.

show abstract

“…We did not have access to data on aqueous Hg concentrations in different locations, making it difficult to disentangle the effects of chlorophyll a and Hg bioavailability. Also, the present chlorophyll a data often came from single measurements that may not be representative of a given system and seasonal fluctuations in chlorophyll a concentrations [45,46]. Overall, these results suggest that chlorophyll a would not serve as an appropriate proxy measurement to estimate Hg concentrations in African fish.…”

Section: Discussionmentioning

confidence: 89%

A review of mercury concentrations in freshwater fishes of Africa: Patterns and predictors

Hanna

Solomon

Poste

et al. 2014

Enviro Toxic and Chemistry

View full text Add to dashboard Cite

The methylated form of mercury (methylmercury) is a potent neurotoxic chemical and a contaminant of concern for fisheries because of its potential effects on ecosystem and human health. In Africa, inland fisheries are a crucial component of food and economic security, yet little information is available on mercury (Hg) contamination trends. The authors compiled published data on Hg contamination in African freshwater fishes, invertebrates, and plankton, as well as on potential drivers of Hg concentrations in these organisms. From 30 identified studies the authors assembled 407 total Hg concentrations from 166 fish species, 10 types of invertebrates, and various plankton, distributed across 31 water bodies in 12 countries. In fishes, total Hg concentrations, expressed as mean (AE standard deviation) per location, averaged 156.0 AE 328.0 ng/g wet weight and ranged from 5.5 ng/g wet weight to 1865.0 ng/g wet weight. Only locations with nearby artisanal and small-scale gold mining operations had mean Hg concentrations above the World Health Organization/Food and Agriculture Organization's recommended guideline for fish (500 ng/g wet wt). The authors used mixed models to detect relationships between fish Hg concentrations and trophic level, mass, latitude, and chlorophyll a. Mass, trophic level, and latitude were all positive predictors of Hg concentration, confirming the presence of Hg bioaccumulation and biomagnification in African fishes. Although strong trends in Hg concentrations were evident, the present study also highlights limited availability of Hg data in Africa. Environ Toxicol Chem 2015;34:215-223. # 2014 SETAC

show abstract

Did the loss of phytoplanktivorous fish contribute to algal blooms in the Mwanza Gulf of Lake Victoria?

Cited by 19 publications

References 40 publications

Nile perch and the transformation of Lake Victoria

Nile perch and the transformation of Lake Victoria

Two new species of zooplanktivorous haplochromine cichlids from Lake Victoria, Tanzania

A review of mercury concentrations in freshwater fishes of Africa: Patterns and predictors

Contact Info

Product

Resources

About