Ecological health of coral reefs in Zanzibar

Bravo, Henrique; Cannicci, Stefano; Huyghe, Filip; Leermakers, Martine; Sheikh, Mohammed Ali; Kochzius, Marc

doi:10.1016/j.rsma.2021.102014

Cited by 6 publications

(5 citation statements)

References 59 publications

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“…Patrizia is documented as a reefal genus in lower littoral zone along the eastern coast of tropical Africa (Jellinek, 1993). It dominated the relatively deep fringing-reef faunas of Biofacies 4, which were subject to sewage-derived nutrient and trace metal pollution from the Zanzibar Town (Narayan et al, 2022;Bravo et al, 2021). Different from all the above-discussed genera, Hiltermannicythere and Perissocytheridea are restricted to shallow intertidal environments as phytal and sediment-dwelling taxa, respectively (Jellinek, 1993), which explains their abundance in our Biofacies 3.…”

Section: Discussionmentioning

confidence: 90%

“…2-3) (Bravo et al, 2021;Larsen et al, 2023). Consistently, foraminifera and coral surveys indicated early stages of reef degradation there (Narayan et al, 2022;Bravo et al, 2021;Thissen and Langer, 2017) It is possible that ongoing anthropogenic disturbances near the Stone Town will eventually exceed the critical threshold levels to cause more pronounced changes in ostracod faunal structures in terms of dominant species through a shift in benthic habitat (Narayan et al, 2022;Hong et al, 2022). Other than Biofacies 1 and 4, Biofacies 2 represented a different type of reefal habitat of Ras Nungwi, Chole Bay, Mafia outside, and Mnemba Atoll (Fig.…”

Section: Discussionmentioning

confidence: 92%

“…Noticeably, the major islands are subject to very different degrees of human exploration, as Zanzibar is densely populated and highly urbanized while Mafia and Pemba are largely uninhabited (Narayan et al, 2022). Stone Town and Bawe, in particular, are faced with a direct discharge of untreated domestic sewage along the western coast of Zanzibar Island, where moderate levels of reef deterioration have been found with diversity decrease and coral cover loss (Bravo et al, 2021;Larsen et al, 2023).…”

Section: Regional Settingmentioning

confidence: 99%

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Reefal ostracod assemblages from the Zanzibar Archipelago (Tanzania)

Tian,

Langer,

Yasuhara

et al. 2024

Preprint

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Abstract. Tropical reefs encompass tremendous biodiversity yet are imperiled by increasing natural and anthropogenic disturbances worldwide. Meiobenthic biotas on coral reefs, for example, ostracods, may experience substantial diversity loss and compositional changes even before being examined. In this study, we investigated the reefal ostracod assemblages from the highly diverse and productive ecosystem in Zanzibar Archipelago (Pemba, Zanzibar, and Mafia islands), Tanzania, to understand how their diversity and faunal structure vary in response to water depth, benthic community type, and human impacts. We characterized four distinct ostracod faunas associated with different benthic habitats, which were deep fore reefs, shallow fringing reefs, degraded fringing reefs, and algal covered intertidal flats. We identified typical ostracod associations, i.e., Bairdiidae versus Loxoconchidae-Xestoleberididae, that showed affinities to hard corals or algae on the reef platforms, respectively. Highest diversity was found on shallow fringing reefs where reefal and algal taxa exhibited maximum overlap of their distributional ranges, while the sand flats, mangrove, and marginal reefs within the intertidal zone had much lower diversity with high dominance of euryhaline taxa. Along the western coast of Zanzibar, coastal development likely resulted in a unique faunal composition and comparatively low diversity of ostracod assemblages among those in reefal habitats, in conjunction with overall reef ecosystem degradation. This study represents the first large-scale assessment of shallow-marine ostracods in the Zanzibar Archipelago. It lays a solid foundation for future research into the ecological significance of ostracods on coral reefs.

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Section: Discussionmentioning

confidence: 90%

Section: Discussionmentioning

confidence: 92%

Section: Regional Settingmentioning

confidence: 99%

See 1 more Smart Citation

Reefal ostracod assemblages from the Zanzibar Archipelago (Tanzania)

Tian,

Langer,

Yasuhara

et al. 2024

Preprint

View full text Add to dashboard Cite

show abstract

“…For instance, reef flats with lower water depths are more likely to be prone to bleaching and among coral taxa, branching corals (taxa: Acropora) are more sensitive to elevated SST (Loya et al, 2001;Bridge et al, 2014;Pisapia et al, 2019). A cumulative effect of these two factors may account for the high coral mortality observed in the protected reefs of Chumbe and Kwale, which feature shallower reef flats with dominating branching corals (Obura et al, 2017;Bravo et al, 2021). The lower coral mortality observed in the unprotected reefs may be attributed to the fact that these reefs are already eroded to the level that more resilient coral species with higher thermal tolerance are likely present.…”

Section: Influence On Benthic Community Structurementioning

confidence: 99%

Post-bleaching alterations in coral reef communities

Elma

Gullström

Yahya

et al. 2023

Marine Pollution Bulletin

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“…The Western Indian Ocean (WIO) is home to approximately 16% of the world's reef species, and after the coral triangle, it hosts the second peak of global coral-reef biodiversity and productivity (Obura, 2012;Johnstone et al, 1998). The coral reefs of the Zanzibar Archipelago are an important regional asset supporting the local economy, including smallscale artisanal fisheries and tourism activities, however, they are vulnerable to increasing degradation (Rehren et al, 2022;Staehr et al, 2018;Lange and Jiddawi, 2009) from pollution (Bravo et al, 2021;Nyanda et al, 2016) and climate-related disturbances, such as the strong El Niño-driven mass coralbleaching events (Staehr et al, 2018;McClanahan et al, 2007;Obura, 2005). Effective conservation of coral reefs here is critical to ensure that they continue to maintain their ecosystem functions and services.…”

Section: Introductionmentioning

confidence: 99%

Local Persistence of Large Benthic Foraminifera (LBF) under Increasing Urban Development: A Case Study from Zanzibar (Unguja), East Africa

et al. 2022

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Coastal marine management is vital for socio-ecological sustainability of developing, tropical ecosystems, which calls for diverse tools to monitor and assess water quality. The carbonate-dominated habitats off Zanzibar were chosen for study due to potential water quality degradation in a rapidly developing tourist destination heavily reliant on its coral reefs. These reefs are largely unmonitored and subject to local and global stressors. A widely used method for assessing reef health, as an early detection method of ecological changes, is the application of large benthic foraminiferal bioindicators, i.e., the FoRAM Index. We expected to find poor water quality conditions in the unmanaged reefs supported by stress-toelerant (opportunistic) foraminiferal assemblages. The dissolved inorganic nitrogen and phosphate values derived from untreated sewage effluent from Stone Town were highly variable (ranging 0.05–3.77 and 0.05–1.45 µM, respectively), moderate, and occasionally approached or exceeded critical threshold values for oligotrophic ecosystems. The analysis of total assemblages indicated an abundance of symbiont-bearing large benthic foraminifera, dominated by prolific Amphistegina species, comparatively low-moderate diversity, high FI values (7.6 on average), and high coral cover. A water quality gradient was reflected by subtle assemblage differences, suggesting that LBF can provide early warning signals of benthic changes, indicating the importance of long-term monitoring programs in vulnerable, rapidly developing coastal ecosystems exposed to increasing pressures.

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Ecological health of coral reefs in Zanzibar

Cited by 6 publications

References 59 publications

Reefal ostracod assemblages from the Zanzibar Archipelago (Tanzania)

Reefal ostracod assemblages from the Zanzibar Archipelago (Tanzania)

Post-bleaching alterations in coral reef communities

Local Persistence of Large Benthic Foraminifera (LBF) under Increasing Urban Development: A Case Study from Zanzibar (Unguja), East Africa

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