Impact of hydrographic parameters and seasonal variation in sediment fluxes on coral status at Chumbe and Bawe reefs, Zanzibar, Tanzania

Muzuka, Alfred N. N.; Dubi, Alfonse M.; Muhando, Christopher A.; Shaghude, Yohanna W.

doi:10.1016/j.ecss.2010.05.007

Cited by 18 publications

(18 citation statements)

References 32 publications

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“…For example, some features of its tidal dynamics have been identified [e.g., Shaghude et al, 2002;Mahongo and Francis, 2010], and the local dynamics near coral reefs have been studied at several locations [e.g., Muzuka et al, 2010]. This paper complements these previous studies by presenting the seasonal and tidal dynamics of the ZCM and showing that the dynamics is consistent with observations.…”

Section: 1002/2015jc010879supporting

confidence: 70%

On the dynamics of the Zanzibar Channel

et al. 2015

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The Zanzibar Channel lies between the mainland of Tanzania and Zanzibar Island in the tropical western Indian Ocean, is about 100 km long, 40 km wide, and 40 m deep, and is essential to local socioeconomic activities. This paper presents a model of the seasonal and tidal dynamics of the Zanzibar Channel based on the Regional Ocean Modeling System (ROMS) and a comparison of the model and observations. The seasonal dynamics of the channel is forced by remote processes and the local wind. Remote forcing creates the East African Coastal Current, a portion of which flows through the channel northward with a seasonally varying magnitude. The local wind enhances this seasonality in the surface Ekman layer, resulting in a stronger northward flow during the southwest monsoon season and a weak northward or occasionally southward flow during the northeast monsoon season. The tidal flows converge and diverge in the center of the channel and reduce the transport in the channel. The remotely forced, wind‐forced, and tidal dynamics contain 5%, 3%, and 92% of the total kinetic energy, respectively. Despite their low kinetic energy, the remotely forced and wind‐forced flows are most relevant in advecting channel water to the open ocean, which occurs in 19 days at the peak of the southwest monsoon season. The channel is well mixed, except during brief periods in the two rainy seasons, and temporarily cools between December and February. The dispersion of passive tracers is presented as an example of potential model applications.

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Section: 1002/2015jc010879supporting

confidence: 70%

On the dynamics of the Zanzibar Channel

et al. 2015

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“…In our study, several sites showed comparatively high deposition rates (see EDMUNDS; DAVIES, 1989;NZALI et al, 1998;WOOLFE, 1999;BARNES;LOUGH, 1999;LARCOMBE et al, 2001). Some studies related high sediment deposition rates with a decrease in coral diversity and abundance (ROGERS, 1990;RICE;HUNTER, 1992;RIEGL, 1995).…”

Section: Discussionmentioning

confidence: 99%

“…This explains the relatively high carbonate content when compared with the bottom sediment adjacent to the reefs . Sediment deposition rates are related to wind/wave direction (MUZUKA et al, 2010), site positioning on the reef (windward or leeward to a particular wind), reef morphology, and reef site surroundings (STORLAZZI et al, 2009). The positive correlation of sediment deposition at Guaratibas station with average northeasterly winds (Table 2) is possibly a result of sediments resuspended on the windward side traveling over or through the sides of the reef and depositing on the more sheltered (and with lower hydrodynamics) leeward side.…”

Section: Discussionmentioning

confidence: 99%

Four-year monthly sediment deposition on turbid southwestern Atlantic coral reefs, with a comparison of benthic assemblages

Castro

Segal

Negrão³

et al. 2012

Braz. j. oceanogr.

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A B S T R A C THigh sedimentation is often related to stress in coral reef communities. Most southwestern Atlantic reefs are characterized by high sedimentation. However, there are no temporal series of sediment deposition rates. We evaluated sediment deposition, the sediment carbonate composition and coral and zoanthid covers on six reefs in Brazil over four-years. Sediment deposition rates varied from near zero to 233 mg cm -2 day -1 , with peaks between August and December, and yearly averages ranging from nine to 104 mg cm -2 day -1 . Deposition rates presented site-specific correlations with wind, indicating that resuspension must be a major factor. The presence of carbonates varied from 38% to 90%, with two sites showing seasonal differences. Benthic communities were fairly similar among sites, but the analyses suggested particular frequencies at each site. There was no significant correlation between sediment and benthic communities. However, Palythoa caribaeorum usually occur in high sediment deposition areas. Our results did not corroborate previous data that suggested that a 10 mg cm -2 day -1 would be a "critical limit for coral survival". Some coral reefs may be associated with high sedimentation environments including carbonatic fractions, but which does not per se hinder the development of southwestern Atlantic coral reef communities. R E S U M OA sedimentação é freqüentemente relacionada a estresse em recifes de coral. Os recifes do Atlântico sul ocidental possuem grande sedimentação, entretanto carecem de séries temporais das taxas de deposição de sedimento. Foram avaliadas estas taxas e a composição carbonática do sedimento, além da cobertura de corais e zoantídeos em seis recifes brasileiros durante quatro anos consecutivos. A deposição variou de zero a 233 mg cm -2 dia -1, com picos entre agosto e dezembro e médias anuais variando de nove a 104 mg cm -2 dia -1. As taxas de deposição apresentaram correlação com o vento, indicando que a ressuspensão deve ser o fator preponderante. A contribuição do carbonato variou de 38% a 90%, com dois locais apresentando diferenciação sazonal. As comunidades bênticas foram similares entre locais, entretanto as análises sugerem freqüencias diferenciadas para cada local. Não houve correlação significativa entre sedimentação e a comunidade bêntica. Entretanto, maior cobertura de Palythoa caribaeorum normalmente ocorreu em áreas de maior sedimentação. Nossos resultados não corroboraram resultados prévios sugerindo que 10 mg cm -2 dia -1 seria "limite crítico para sobrevivência" dos corais. Recifes brasileiros podem estar associados a ambientes de alta deposição de sedimento com elevadas frações carbonáticas, o que não impede o desenvolvimento das comunidades recifais do Atlântico sul ocidental.

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“…In a study conducted in Tanzania over a two-year period from October 2006 to March 2009, monthly sedimentation rate monitored ranged from 0.2 to 41.5 mg/cm 2 /day at the Bawe reefs, and from 0.8 to 65.8 mg/cm 2 /day at the Chumbe reefs, with both sites having high live coral covers and high coral genera diversity [23]. This suggests that corals at Chumbe and Bawe have probably adapted to the sedimentation situation and thus are able to overcome the sediment lethal limit of 10 mg/cm 2 /day suggested by Rogers [19].…”

Section: A Tolerance Of Corals To Sedimentation: Intensity Durationmentioning

confidence: 99%

Modeling Drill Cuttings Sedimentation on Corals for Exploration Wells Z-1 and B-1, Offshore Sabah

Teh¹,

Koh²

2016

IJESD

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Abstract-Oil well drilling activities generate residues called drill cuttings that will be treated before being disposed onsite. When drill cuttings are released into the sea, drill cutting piles or mounds will form on the seabed. These pile formations may hinder future under-sea operation. They may have adverse impacts on corals if the thickness of the pile over the coral beds is persistently high. This simulation study is conducted at the drill cuttings release sites Z-1 and B-1 in the South China Sea off the coast of Sabah. This modelling study will assess the potential impacts of the pile formation on coral community and on the ecology in the dive site (shipwreck) nearby. For Z-1, the particles settle on the seabed far away from the corals and far away from the shipwreck sites. Hence they will have no adverse impact on the corals nor on the shipwreck site environment and ecology. For B-1, the coral site is located at a shorter distance from the discharge location. The pile height at the coral site varies between 0.05 mm to 0.5 mm. The average sedimentation rate varying between 3.1 to 31 mg/cm 2 /day occurs over a short duration of 3.875 days. This low sedimentation rate over a short duration will have insignificant impact on the corals.Index Terms-Corals, drill cuttings, oil and gas, TUNA-PT.

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Impact of hydrographic parameters and seasonal variation in sediment fluxes on coral status at Chumbe and Bawe reefs, Zanzibar, Tanzania

Cited by 18 publications

References 32 publications

On the dynamics of the Zanzibar Channel

On the dynamics of the Zanzibar Channel

Four-year monthly sediment deposition on turbid southwestern Atlantic coral reefs, with a comparison of benthic assemblages

Modeling Drill Cuttings Sedimentation on Corals for Exploration Wells Z-1 and B-1, Offshore Sabah

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