Three-dimensional island wakes in the field, laboratory experiments and numerical models

Wolanski, Eric; Asaeda, Takashi; Tanaka, Akihiro; Deleersnijder, Éric

doi:10.1016/0278-4343(95)00087-9

Cited by 88 publications

(60 citation statements)

References 29 publications

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“…Island and headland wake systems are often comprised of 2 regions or water masses exhibiting extremely different current velocities and patterns. These regions are delineated by a flow-separation or shear line (Hamner & Hauri 1981, Geyer 1993, Wolanski et al 1996. The shear line represents a front between rapidly flowing water (that has separated from the edge of the island or headland) and more slowly moving water in the lee of the island or headland (Geyer 1993, Wolanski et al 1996.…”

Section: Discussionmentioning

confidence: 99%

“…The shear line represents a front between rapidly flowing water (that has separated from the edge of the island or headland) and more slowly moving water in the lee of the island or headland (Geyer 1993, Wolanski et al 1996. In this leeward region, 1 or more eddies usually form (Alldredge & Hamner 1980, Signell & Geyer 1991 within these eddies controls the aggregation of plankton and weak nekton into predictable locations (Wolanski & Hamner 1988, Wolanski et al 1996. The positions of both minke and fin whale surfacings were clearly located in areas of the wake that are known to exhibit slower current velocities.…”

Section: Discussionmentioning

confidence: 99%

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Fin whales Balaenoptera physalus and minke whales Balaenoptera acutorostrata exploit a tidally driven island wake ecosystem in the Bay of Fundy

Johnston¹,

Thorne²,

Read³

2005

Mar. Ecol. Prog. Ser.

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Marine predators forage in tidally induced oceanographic features, where they exploit predictable aggregations of prey. Very little, however, is known about how the physical forcing within these features affects their behaviour at a fine scale. During the summers of 2000 and 2002, we combined a series of cliff-top observations and boat-based surveys to describe the movements of fin whales Balaenoptera physalus and minke whales Balaenoptera acutorostrata within a predictable island wake occurring near Grand Manan Island in the Bay of Fundy, Canada. We recorded the location of fin and minke whales as they surfaced in or near the wake. We also examined the movements of individual fin whales using focal follow techniques to assess their habitat use within 3 distinct oceanographic regions (non-wake habitat, eddy habitat and free stream habitat) of the study area. Fin and minke whale occurrence was highest during flood tides and lowest during the mid-ebb phases. Fin (33) and minke whale (64) sightings were concentrated in areas characterised by slower current velocities -the region influenced by the eddy system formed within the wake. Nine individual fin whales, identified through photographs, spent a disproportionate amount of time within the eddy habitat portion of the study area, with occasional forays into free stream habitat. Foraging in the high-vorticity regions of the wake likely allows whales to exploit higher prey concentrations than in the free stream habitat or non-wake habitat.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Fin whales Balaenoptera physalus and minke whales Balaenoptera acutorostrata exploit a tidally driven island wake ecosystem in the Bay of Fundy

Johnston¹,

Thorne²,

Read³

2005

Mar. Ecol. Prog. Ser.

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“…This divergence in the regional waters (which are characterized as oligotrophic) and the regions nearby the vessel indicates that the MAR may be influencing the local dynamics, thereby altering the distribution of nutrients. As explained by Wolanski et al (1995) 14 , when shallow water flows around an obstacle, the currents can generate eddies in the shadows of these barriers, which can generate upwelling within these eddies and downwelling at the edges. This can increase the sediment load and, as a consequence, the nutrients in the water column.…”

Section: Resultsmentioning

confidence: 96%

Controls on Temporal and Spatial Variation of Nutrients in a Tropical Marine Artificial Reef: The Case of the Victory 8B on the Southeastern Brazilian Coast

Costa¹,

Andrade²,

Bazoni³

et al. 2014

Revista Virtual De Química

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Resumo: O objetivo deste estudo foi avaliar a distribuição temporal e espacial de nutrientes em torno do recife artificial marinho (MAR) 8B Victory, um navio afundado propositadamente em Guarapari (20 ° 40 ' S e 40 ° 30' W), no estado do Espírito Santo, em uma das mais ricas áreas de biodiversidade marinha na costa brasileira. Oito cruzeiros trimestrais de um dia foram realizados por mais de dois anos (de março de 2005 a abril de 2007) . As amostras foram coletadas em 12 estações diferentes ao redor do navio para a análise dos nutrientes inorgânicos dissolvidos (nitrito, nitrato, silício reativo e ortofosfato), clorofila a, phaeopigmentos, salinidade e temperatura. Correlações de ortofosfato e clorofila podem indicar que ele é limitante. As suas concentrações eram sempre baixas, o que pode ser devido à sedimentação de carbonato, pois a região é rica em sedimentos deste sal. Nutrientes nitrogenados foram enriquecidos, indicando que o MAR muda a dinâmica da água. Alternativamente, as ilhas próximas do navio também podem estar trabalhando como recifes, aumentando a concentração. Embora não tenha havido variação espacial significativa, mudanças sazonais controladas principalmente por direções atuais, rotas frias de entrada frontal e as chuvas foram encontradas, com uma influência menor da atividade biológica. Palavras-chave:Clorofila-a (Chl a); Guarapari; Nutrientes; Correntes; Afloramento. AbstractThe objective of this study was to evaluate the temporal and spatial nutrient distribution around the marine artificial reef (MAR) Victory 8B, a ship purposely sunk at Guarapari (20°40' S and 40°30' W), Espírito Santo State, in one of the richest marine biodiversity areas on the Brazilian coast. Eight trimestral one-day cruises were carried out from March 2005 to April 2007. Samples were collected at 12 different stations around the ship for the analysis of dissolved inorganic nutrients (nitrite, nitrate, reactive silicon and orthophosphate), chlorophyll a, phaeopigments, salinity and temperature. Orthophosphate correlations to chlorophyll a may indicate that it is limiting. Its concentrations were always low, which may be due to carbonate sedimentation, as the area is rich in calcium carbonate sediment. Nitrogenous nutrients were enriched, indicating that the MAR changes the water dynamics. Alternatively, islands nearby the ship may also be working as reefs to increase the concentration. Although there was no statistically significant spatial variation, seasonal changes controlled mainly by current directions, cold front entrance routes and rainfall were found, with a minor influence of biological activity.

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“…SLIM has an unstructured grid which can be made finer in areas where a high resolution is required and coarser in open areas, prioritizing the allocation of computational power. Unstructured grids are particularly useful in coral reef systems (Lambrechts et al, 2008) as a high spatial resolution is required to avoid erasing small reefs and to accurately simulate the current shear distribution near reef edges (Wolanski et al, 1996). SLIM has been used to effectively model the hydrodynamics of the GBR system (e.g., Lambrechts et al, 2008;Delandmeter et al, 2017;Wildermann et al, 2017).…”

Section: Biophysical Modelingmentioning

confidence: 99%

Wind Conditions on the Great Barrier Reef Influenced the Recruitment of Snapper (Lutjanus carponotatus)

et al. 2018

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Most coral reef fishes have a pelagic larval stage before recruiting to reefs. The survival of larvae and their subsequent recruitment can drive the dynamics of reef populations. Here we show that the recruitment of the snapper Lutjanus carponotatus to One Tree Island in the Capricorn Bunker Group, in the southern Great Barrier Reef, was highly variable over 23 years. We predicted that the currents in the Capricorn Bunker Group, including their wind driven components and the Capricorn Eddy (a nearby transient oceanic eddy), would affect patterns of recruitment. A biophysical model was used to investigate this prediction. L. carponotatus were collected from One Tree Island and the dates when they were in the plankton as larvae were determined from their otoliths. The winds present during the pelagic phases of the fish were examined; they were found to have survived either longshore (SSE) winds that induced little cross shelf movement in the larval plume or cross shelf (ENE) winds that induced little longshore movement. The unidirectional transportation of the larval plume in these conditions was favorable for recruitment as it kept the plume concentrated in the Capricorn Bunker Group. These winds were more prevalent in the periods of peak L. carponotatus production that preceded high recruitment. Dispersal under average winds (6.2 m s −1 from the prevailing ESE) and strong winds (velocity 1.5 times average), with and without the Capricorn Eddy, was also modeled. Each of these combinations were less favorable for recruitment than the longshore and cross shelf winds larval L. carponotatus survived before reaching OTI. The larval plume was comparatively less concentrated in the Capricorn Bunker Group under average winds. Strong winds transported the larval plume far longshore, to the NW, away from the Capricorn Bunker Group, while the Capricorn Eddy transported larvae seaward into oceanic waters. Larval swimming could counteract these dispersive forces; however, significant dispersion had occurred before larvae developed strong swimming and orientation abilities. This study provides a physical proxy for the recruitment of snapper. Further, we have demonstrated that great insights into recruitment variability can be gained through determining the specific conditions experienced by survivors.

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Three-dimensional island wakes in the field, laboratory experiments and numerical models

Cited by 88 publications

References 29 publications

Fin whales Balaenoptera physalus and minke whales Balaenoptera acutorostrata exploit a tidally driven island wake ecosystem in the Bay of Fundy

Fin whales Balaenoptera physalus and minke whales Balaenoptera acutorostrata exploit a tidally driven island wake ecosystem in the Bay of Fundy

Controls on Temporal and Spatial Variation of Nutrients in a Tropical Marine Artificial Reef: The Case of the Victory 8B on the Southeastern Brazilian Coast

Wind Conditions on the Great Barrier Reef Influenced the Recruitment of Snapper (Lutjanus carponotatus)

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