Coral reef sedimentation on Rodrigues and the Western Indian Ocean and its impact on the carbon cycle

2005 ◽  
Vol 363 (1826) ◽  
pp. 101-120 ◽  
Author(s):  
Siwan A. Rees ◽  
Bradley N. Opdyke ◽  
Paul A. Wilson ◽  
L. Keith Fifield
Keyword(s):  
Coral Reef ◽  
Calcium Carbonate ◽  
Indian Ocean ◽  
Carbon Cycle ◽  
Spring Tide ◽  
Western Indian Ocean ◽  
Southwest Indian Ocean ◽  
Tourist Attractions ◽  
Aeolian Dunes ◽  
Warming World

Coral reefs in the southwest Indian Ocean cover an area of ca. 18530 km 2 compared with a global reef area of nearly 300000 km 2 . These regions are important as fishing grounds, tourist attractions and as a significant component of the global carbon cycle. The mass of calcium carbonate stored within Holocene neritic sediments is a number that we are only now beginning to quantify with any confidence, in stark contrast to the mass and sedimentation rates associated with pelagic calcium carbonate, which have been relatively well defined for decades. We report new data that demonstrate that the reefs at Rodrigues, like those at Réunion and Mauritius, only reached a mature state (reached sea level) by 2–3 ka: thousands of years later than most of the reefs in the Australasian region. Yet field observations show that the large lagoon at Rodrigues is already completely full of carbonate detritus (typical lagoon depth less than 1 m at low spring tide). The presence of aeolian dunes at Rodrigues indicates periodic exposure of past lagoons throughout the Pleistocene. The absence of elevated Pleistocene reef deposits on the island indicates that the island has not been uplifted. Most Holocene reefs are between 15 and 20 m in thickness and those in the southwest Indian Ocean appear to be consistent with this observation. We support the view that the CO 2 flux associated with coral–reef growth acts as a climate change amplifier during deglaciation, adding CO 2 to a warming world. southwest Indian Ocean reefs could have added 7–10% to this global flux during the Holocene.

scholarly journals Post-bleaching mortality of a remote coral reef community in Seychelles, Western Indian Ocean

2019 ◽  
Vol 18 (1) ◽  
pp. 11
Author(s):  
Elena Gadoutsis ◽  
Clare A.K. Daly ◽  
Julie P. Hawkins ◽  
Ryan Daly
Keyword(s):  
Coral Reef ◽  
Indian Ocean ◽  
Western Indian Ocean ◽  
Coral Reef Community ◽  
Reef Community

scholarly journals Disentangling drivers of the abundance of coral reef fishes in the Western Indian Ocean

2019 ◽  
Vol 9 (7) ◽  
pp. 4149-4167 ◽  
Author(s):  
Melita A. Samoilys ◽  
Andrew Halford ◽  
Kennedy Osuka
Keyword(s):  
Coral Reef ◽  
Indian Ocean ◽  
Western Indian Ocean ◽  
Reef Fishes ◽  
Coral Reef Fishes

Vulnerability to collapse of coral reef ecosystems in the Western Indian Ocean

2021 ◽  
Author(s):  
David Obura ◽  
Mishal Gudka ◽  
Melita Samoilys ◽  
Kennedy Osuka ◽  
James Mbugua ◽  
...  
Keyword(s):  
Coral Reef ◽  
Indian Ocean ◽  
Western Indian Ocean ◽  
Coral Reef Ecosystems

Associations between climate stress and coral reef diversity in the western Indian Ocean

2011 ◽  
Vol 17 (6) ◽  
pp. 2023-2032 ◽  
Author(s):  
TIM R. McCLANAHAN ◽  
JOSEPH M. MAINA ◽  
NYAWIRA A. MUTHIGA
Keyword(s):  
Coral Reef ◽  
Indian Ocean ◽  
Western Indian Ocean ◽  
Climate Stress

Tree-climbing behaviour of Cerithidea decollata, a western Indian Ocean mangrove gastropod (Mollusca: Potamididae)

2006 ◽  
Vol 86 (6) ◽  
pp. 1429-1436 ◽  
Author(s):  
Marco Vannini ◽  
Rocco Rorandelli ◽  
Outi Lähteenoja ◽  
Elisha Mrabu ◽  
Sara Fratini
Keyword(s):  
Indian Ocean ◽  
Neap Tide ◽  
High Tide ◽  
Spring Tide ◽  
Western Indian Ocean ◽  
High Water ◽  
Avicennia Marina ◽  
Single Individual ◽  
Night Time ◽  
Mangrove Tree

The behaviour of Cerithidea decollata, a common western Indian Ocean mangrove tree climbing gastropod, was studied in Mida Creek, Kenya. At the study site, this snail mainly lived in Avicennia marina dominated areas, i.e. in the mangrove belt between high water spring tide and high water neap tide levels. Not a single individual was found on the less common mangrove tree Lumnitzera racemosa, living just above the A. marina level (together with terrestrial grass), and was very rarely recorded on the common Rhizophora mucronata, bordering the seaward side of the A. marina belt. No significant gradient of C. decollata density was found within the whole 150–200 m wide belt. The majority of C. decollata rested on tree trunks during high tide, creeping on the mud flat below the tree for part of low tide, and returning on the trunks well before being reached by the water. This migratory pattern was more evident at spring than at neap tide, at day than at night time and it was strongly influenced by the shore level of the mangrove zone in which animals resided. While C. decollata from lower shore levels neatly massively migrated twice a day, individuals from upper levels showed a more continuous and irregular activity, sometimes crawling on the mud even at high water of spring tide, when they experience just a few centimetres of water for no more than one to two hours.

Linkage between fish functional groups and coral reef benthic habitat composition in the Western Indian Ocean

2016 ◽  
Vol 98 (2) ◽  
pp. 387-400 ◽  
Author(s):  
Kennedy Osuka ◽  
Marc Kochzius ◽  
Ann Vanreusel ◽  
David Obura ◽  
Melita Samoilys
Keyword(s):  
Coral Reef ◽  
Indian Ocean ◽  
Functional Groups ◽  
Habitat Type ◽  
Western Indian Ocean ◽  
Reef Fishes ◽  
Coralline Algae ◽  
Benthic Habitat ◽  
Habitat Types ◽  
Habitat Composition

Benthic habitat composition is a key factor that structures assemblages of coral reef fishes. However, natural and anthropogenic induced disturbances impact this relationship. This study investigates the link between benthic habitat composition and fish functional groups in four countries in the Western Indian Ocean (WIO). Benthic composition of 32 sites was quantified visually from percentage cover of hard and soft corals, rubble, turf, fleshy and crustose coralline algae. At each site, abundance of 12 coral-associated fish functional groups in 50 × 5 m transects was determined. Cluster analysis characterized reefs based on benthic cover and revealed five habitat types (A, B, C, D and E) typified by decreasing cover of hard corals, increasing cover of turf and/or fleshy algae and differences in benthic diversity. Habitat type A was present in all four countries. Other habitats types showed geographic affiliations: notably Comoros sites clustered in either habitats B or E, northern Madagascar had B, C and D type habitats, whereas sites in central Tanzania and northern Mozambique had habitats D and E. Fish functional groups showed significant linkages with some habitat types. The abundances of corallivores, invertivores, detritivores and grazers were higher in habitat B, whereas planktivores and small excavators showed lower abundances in the same habitat. These linkages between benthic habitat types and fish functional groups are important in informing priority reefs that require conservation and management planning.

scholarly journals Basin-scale estimates of pelagic and coral reef calcification in the Red Sea and Western Indian Ocean

2014 ◽  
Vol 111 (46) ◽  
pp. 16303-16308 ◽  
Author(s):  
Zvi Steiner ◽  
Jonathan Erez ◽  
Aldo Shemesh ◽  
Ruth Yam ◽  
Amitai Katz ◽  
...  
Keyword(s):  
Coral Reef ◽  
Indian Ocean ◽  
Red Sea ◽  
Western Indian Ocean ◽  
Basin Scale

scholarly journals Sea–air CO<sub>2</sub> fluxes in the Indian Ocean between 1990 and 2009

2013 ◽  
Vol 10 (7) ◽  
pp. 10759-10810
Author(s):  
V. V. S. S. Sarma ◽  
A. Lenton ◽  
R. Law ◽  
N. Metzl ◽  
P. K. Patra ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Carbon Cycle ◽  
Interannual Variability ◽  
Atmospheric Co2 ◽  
Co2 Uptake ◽  
Co2 Fluxes ◽  
Southwest Indian Ocean ◽  
Biogeochemical Models ◽  
The Indian Ocean ◽  
Atmospheric Inversions

Abstract. The Indian Ocean (44° S–30° N) plays an important role in the global carbon cycle, yet remains one of the most poorly sampled ocean regions. Several approaches have been used to estimate net sea–air CO2 fluxes in this region: interpolated observations, ocean biogeochemical models, atmospheric and ocean inversions. As part of the RECCAP (REgional Carbon Cycle Assessment and Processes) project, we combine these different approaches to quantify and assess the magnitude and variability in Indian Ocean sea–air CO2 fluxes between 1990 and 2009. Using all of the models and inversions, the median annual mean sea–air CO2 uptake of −0.37 ± 0.06 Pg C yr–1, is consistent with the −0.24 ± 0.12 Pg C yr–1 calculated from observations. The fluxes from the Southern Indian Ocean (18° S–44° S; −0.43 ± 0.07 Pg C yr–1) are similar in magnitude to the annual uptake for the entire Indian Ocean. All models capture the observed pattern of fluxes in the Indian Ocean with the following exceptions: underestimation of upwelling fluxes in the northwestern region (off Oman and Somalia), over estimation in the northeastern region (Bay of Bengal) and underestimation of the CO2 sink in the subtropical convergence zone. These differences were mainly driven by a lack of atmospheric CO2 data in atmospheric inversions, and poor simulation of monsoonal currents and freshwater discharge in ocean biogeochemical models. Overall, the models and inversions do capture the phase of the observed seasonality for the entire Indian Ocean but over estimate the magnitude. The predicted sea–air CO2 fluxes by Ocean BioGeochemical Models (OBGM) respond to seasonal variability with strong phase lags with reference to climatological CO2 flux, whereas the atmospheric inversions predict an order of magnitude higher seasonal flux than OBGMs. The simulated interannual variability by the OBGMs is weaker than atmospheric inversions. Prediction of such weak interannual variability in CO2 fluxes by atmospheric inversions was mainly caused by lack of atmospheric data in the Indian Ocean. The OBGM models suggest a small strengthening of the sink over the period 1990–2009 of −0.01 Pg C decade–1. This is inconsistent with the observations in the southwest Indian Ocean that shows the growth rate of oceanic pCO2 was faster than the observed atmospheric CO2 growth, a finding attributed to the trend of the Southern Annual Mode (SAM) during the 1990s.

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