Patterns of variability of sea surface chlorophyll in the Mozambique Channel: A quantitative approach

Tew-Kai, Emilie; Marsac, Francis

doi:10.1016/j.jmarsys.2008.11.007

Cited by 78 publications

(31 citation statements)

References 51 publications

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“…The dynamics associated with mesoscale eddies have a significant influence on biological communities [12][13][14]. An in situ investigation of the MB eddy one month after its formation showed a uniform distribution of chlorophyll a in the upper 100 m [16], as a result of the well mixed nature of the water column under strong wind conditions [15,16].…”

Section: Discussionmentioning

confidence: 99%

“…An increase in diadinoxanthin:chlorophyll a ratios and a decline in the quantum efficiency of It has been demonstrated that eddies in the southwest Indian Ocean have a significant influence on the structure of biological communities and on ecosystem functioning. Overall, it is typical to have elevated chlorophyll in cyclonic eddies, and lower concentrations in anticyclonic eddies [12][13][14]. However, there appear to be some differences in the characteristics of cyclonic eddies sampled during different seasons in the MC and MB.…”

Section: Introductionmentioning

confidence: 96%

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Variations in Remotely-Sensed Phytoplankton Size Structure of a Cyclonic Eddy in the Southwest Indian Ocean

2018

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Phytoplankton size classes were derived from weekly-averaged MODIS Aqua chlorophyll a data over the southwest Indian Ocean in order to assess changes in surface phytoplankton community structure within a cyclonic eddy as it propagated across the Mozambique Basin in 2013. Satellite altimetry was used to identify and track the southwesterly movement of the eddy from its origin off Madagascar in mid-June until mid-October, when it eventually merged with the Agulhas Current along the east coast of South Africa. Nano-and picophytoplankton comprised most of the community in the early phase of the eddy development in June, but nanophytoplankton then dominated in austral winter (July and August). Microphytoplankton was entrained into the eddy by horizontal advection from the southern Madagascar shelf, increasing the proportion of microphytoplankton to 23% when the chlorophyll a levels reached a peak of 0.36 mg·m −3 in the third week of July. Chlorophyll a levels declined to <0.2 mg·m −3 in austral spring (September and October) as the eddy propagated further to the southwest. Picophytoplankton dominated the community during the spring period, accounting for >50% of the population. As far as is known, this is the first study to investigate temporal changes in chlorophyll a and community structure in a cyclonic eddy propagating across an ocean basin in the southwest Indian Ocean.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Variations in Remotely-Sensed Phytoplankton Size Structure of a Cyclonic Eddy in the Southwest Indian Ocean

2018

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“…In addition to the usual central eddy pumping mechanism, observational and process-modelling studies have shown an enhancement of primary production and an accumulation of biomass on the edges of anticylonic eddies (Mizobata et al 2002) and at eddy-eddy interactions (Lima et al 2002). Eddies in the Mozambique Channel tend to advect coastal waters at their periphery when they run along the coast (Tew-Kai & Marsac 2008) and are thereby able to drain a significant amount of nutrient-rich waters towards the middle of the channel. Large micronekton aggregations are infrequent whithin eddies (low SLA gradient values), although high primary production can be observed at the centre of cyclonic eddies (Lima et al 2002).…”

Section: Discussionmentioning

confidence: 99%

Mesoscale eddies influence distribution and aggregation patterns of micronekton in the Mozambique Channel

Sabarros¹,

Ménard²,

Levenez³

et al. 2009

Mar. Ecol. Prog. Ser.

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Oceanic mesoscale circulation is a crucial structuring force in the marine environment. Dynamic processes associated with eddies, such as eddy-induced upwelling or eddy-eddy interaction, drive the transport and distribution of nutrients that support the whole food chain, presumably through bottom-up processes. Eddies can shape the distribution of organisms at both low (phytoplankton, zooplankton and fish larvae) and high trophic levels (top fish predators, seabirds or turtles), but the impact of mesoscale features on intermediate trophic levels (micronekton) remains poorly understood. We analysed the influence of eddies on the distribution of micronekton aggregations in the Mozambique Channel by combining data from acoustic surveys and satellite sea topography. We demonstrated that large aggregations of micronekton occurred mainly in areas where the local horizontal gradient of sea level anomalies is strong, i.e. at the periphery of eddies. We observed that, in this region, eddies running along the coast advect coastal nutrient-rich waters at their edges, which support the base of the food chain. We propose that eddies can shape the distribution and the aggregation patterns of the prey of marine top predators through bottom-up processes.

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“…Kai and Marsac 2010). Top predators, including tunas (Tew Kai and Marsac 2010) and frigatebirds (TewKai andMarsac 2009, Weimerskirch et al 2010), are known to associate with mesoscale eddies in the Mozambique Channel. According to Sabarros et al (2009), advection of coastal nutrient-rich waters and eddy-eddy interactions enhance biological production, which sustains the stocks of micronekton through bottom-up processes and in turn shape the distribution of top predators.…”

Section: Acquisition Of New Datamentioning

confidence: 99%

Predicting top predator habitats in the Southwest Indian Ocean

Mannocci¹,

Laran²,

Monestiez³

et al. 2013

Ecography

102

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International audienceTop predators need to develop optimal strategies of resources and habitats utilization in order to optimize their foraging success. At the individual scale, a predator has to maximize his intake of food while minimizing his cost of foraging to optimize his energetic gain. At the ecosystem scale, we hypothesized that foraging strategies of predators also respond to their general energetic constraints. Predators with energetically costly lifestyles may be constrained to select high quality habitats whereas more phlegmatic predators may occupy both low and high quality habitats. The objectives of this study were 1) to investigate predator responses to heterogeneity in habitat quality with reference to their energetic strategies and 2) to evaluate their responses to contemporaneous versus averaged habitat quality. We collected cetacean and seabird data from an aerial survey in the Southwest Indian Ocean, a region characterized by heterogeneous oceanographic conditions. We classified cetaceans and seabirds into energetic guilds and described their habitats using remotely sensed covariates at contemporaneous and time-averaged resolutions and static covariates. We used generalized additive models to predict their habitats at the regional scale. Strategies of habitat utilization appeared in accordance with predators energetic constraints. Cetaceans responded to the heterogeneity in habitat quality, with higher densities predicted in more productive areas. However, the costly Delphininae appeared to be more dependent on habitat quality (showing a 1-to-13 ratio between the lowest and highest density sectors) than the more phlegmatic sperm and beaked whales (showing only a 1-to-3 ratio). For seabirds, predictions primarily reflected colony locations, although the colony effect was stronger for costly seabirds. Moreover, our results suggest that predators may respond better to persistent oceanographic features. To provide a third dimension to habitat quality, cetacean strategies of utilization of the vertical habitat could be related to the distribution of micronekton in the water column

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Patterns of variability of sea surface chlorophyll in the Mozambique Channel: A quantitative approach

Cited by 78 publications

References 51 publications

Variations in Remotely-Sensed Phytoplankton Size Structure of a Cyclonic Eddy in the Southwest Indian Ocean

Variations in Remotely-Sensed Phytoplankton Size Structure of a Cyclonic Eddy in the Southwest Indian Ocean

Mesoscale eddies influence distribution and aggregation patterns of micronekton in the Mozambique Channel

Predicting top predator habitats in the Southwest Indian Ocean

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