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Metazooplankton distribution across the Southern Indian Ocean with emphasis on the role of Larvaceans

View Article: PubMed Central

ABSTRACT

The abundance and depth distribution of metazoans >20 μm were investigated at seven stations across the Southern Indian Ocean (SIO), October–November 2006. Copepod nauplii, copepodites and larvaceans dominated the metazooplankton community. Copepodites were most abundant within Agulhas Current and Southern Ocean waters, decreasing toward subtropical/tropical areas, whereas larvaceans showed the inverse pattern. The fraction <200 μm contained the majority of the zooplankton enumerated, including 81, 23 and 93% of the larvacean, copepodite and nauplii abundances, respectively. The relative abundance of larvaceans compared with copepodites increased from 7 to 44% from South Africa towards Australia. Peak copepodite biomass was observed off South Africa, while larvacean biomass was <1% of the copepodite biomass there, increasing to 6% in tropical waters. Both copepodite and nauplii biomass were positively correlated to total Chl a (P < 0.0001), larvacean biomass was only significantly related to temperature (P = 0.0213). Despite their low biomass, larvacean production was estimated to exceed the copepod production up to five times. It appears that the abundance and role of larvaceans in the SIO has been severely underestimated in previous studies; thus future investigations into the fate of organic matter will remain incomplete if this group is not adequately considered.

No MeSH data available.


Sea surface temperatures, cruise track and station locations, illustrating the frontal systems of the Southern Indian Ocean present during October–November 2006 superimposed from Satellite images: ENVISAT, NOAA 17 and 18, MODIS Aqua and AMSR-E. From Visser et al. submitted for publication.
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FBP002F1: Sea surface temperatures, cruise track and station locations, illustrating the frontal systems of the Southern Indian Ocean present during October–November 2006 superimposed from Satellite images: ENVISAT, NOAA 17 and 18, MODIS Aqua and AMSR-E. From Visser et al. submitted for publication.

Mentions: The investigation of the SIO was conducted during the Danish Galathea3 Expedition (leg 7) from Cape Town, South Africa to Broome, NW Australia, from 17 October to 5 November 2006 (Fig. 1). A detailed description and analysis of the oceanography and the base of the food web are presented in Visser et al. (submitted for publication). The oceanography of the SIO covers several frontal systems consisting of the Northern Subtropical Front (NSTF), the Southern Subtropical Front (Subtropical Convergence) (SSTF) and the Agulhas Front (AF), associated with the eastward propagation of the Agulhas Current up to 70°–80° E. The SSTF (Subtropical Convergence) separates warm and saline subtropical Indian Ocean waters from cooler and fresher ones of the Southern Ocean (Kostianoy et al., 2003).


Metazooplankton distribution across the Southern Indian Ocean with emphasis on the role of Larvaceans
Sea surface temperatures, cruise track and station locations, illustrating the frontal systems of the Southern Indian Ocean present during October–November 2006 superimposed from Satellite images: ENVISAT, NOAA 17 and 18, MODIS Aqua and AMSR-E. From Visser et al. submitted for publication.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2667276&req=5

FBP002F1: Sea surface temperatures, cruise track and station locations, illustrating the frontal systems of the Southern Indian Ocean present during October–November 2006 superimposed from Satellite images: ENVISAT, NOAA 17 and 18, MODIS Aqua and AMSR-E. From Visser et al. submitted for publication.
Mentions: The investigation of the SIO was conducted during the Danish Galathea3 Expedition (leg 7) from Cape Town, South Africa to Broome, NW Australia, from 17 October to 5 November 2006 (Fig. 1). A detailed description and analysis of the oceanography and the base of the food web are presented in Visser et al. (submitted for publication). The oceanography of the SIO covers several frontal systems consisting of the Northern Subtropical Front (NSTF), the Southern Subtropical Front (Subtropical Convergence) (SSTF) and the Agulhas Front (AF), associated with the eastward propagation of the Agulhas Current up to 70°–80° E. The SSTF (Subtropical Convergence) separates warm and saline subtropical Indian Ocean waters from cooler and fresher ones of the Southern Ocean (Kostianoy et al., 2003).

View Article: PubMed Central

ABSTRACT

The abundance and depth distribution of metazoans >20 μm were investigated at seven stations across the Southern Indian Ocean (SIO), October–November 2006. Copepod nauplii, copepodites and larvaceans dominated the metazooplankton community. Copepodites were most abundant within Agulhas Current and Southern Ocean waters, decreasing toward subtropical/tropical areas, whereas larvaceans showed the inverse pattern. The fraction <200 μm contained the majority of the zooplankton enumerated, including 81, 23 and 93% of the larvacean, copepodite and nauplii abundances, respectively. The relative abundance of larvaceans compared with copepodites increased from 7 to 44% from South Africa towards Australia. Peak copepodite biomass was observed off South Africa, while larvacean biomass was <1% of the copepodite biomass there, increasing to 6% in tropical waters. Both copepodite and nauplii biomass were positively correlated to total Chl a (P < 0.0001), larvacean biomass was only significantly related to temperature (P = 0.0213). Despite their low biomass, larvacean production was estimated to exceed the copepod production up to five times. It appears that the abundance and role of larvaceans in the SIO has been severely underestimated in previous studies; thus future investigations into the fate of organic matter will remain incomplete if this group is not adequately considered.

No MeSH data available.