Distribution of meroplankton communities in the Bransfield Strait, Antarctica

Abstract

The spatial distribution of meroplankton in Bransfield Strait, Antarctica, and its relationships with hydrographical conditions are described. Biological sampling was carried out with BIONESS sampling gear at 19 stations and at 5 depths between 10 and 300 m. The main hydrographic features were a shallow hydrographic front in the southern part of the strait that separates Transitional Zonal Water with Bellingshausen influence (TBW) from Transitional Zonal Water with Weddell influence (TWW) and a slope front, the so-called Bransfield front, along the South Shetland Islands Slope (SSI). A northeastward baroclinic jet known as the Bransfield Current (BC) originates from this slope front. The meroplankton community was very diverse and included 12 types of larvae, dominated by polychaete and echinoderm larvae. The meroplankton were more abundant closer to the SSI in the BC and decreased in number towards the Antarctic Peninsula. Polychaete larvae were found close to both shores but mainly close to the SSI in TBW; they were very sparse in the central basin, appeared again below 100 m depth in TWW, and increased in abundance in upper layers at stations between the hydrographic front and the Antarctic Peninsula, in TWW. By contrast, echinoderm larvae mainly occupied the central basin and were always associated with the upper 100 m in TBW, just above the polychaete larvae; they were almost absent from TWW. In summary, meroplanktonic larval exhibit a strong dependence on water masses, depth, and fronts.

Brooding and Species Diversity in the Southern Ocean: Selection for Brooders or Speciation within Brooding Clades?

“…Similarly, Thatje et al (2005b) argue that the predominance of developmental lecithotrophy in the Antarctic is the consequence of the near-complete extinction of benthic communities during glacial maxima and recolonization from deeper waters where species had undergone an "evolutionary temperature adaptation" that led to lecithotrophy. However, no evidence supports the idea that either nonpelagic development or lecithotrophy is an adaptation to low temperature, and the fact that a wide variety of both planktotrophic and lecithotrophic pelagic larvae have been found in both Antarctic and Arctic waters (e.g., Thorson, 1936;Stanwell-Smith et al, 1999;Sewell, 2005;Palma et al, 2007;Vázquez, 2007;Fetzer and Arntz, 2008) persuasively indicates that marine invertebrate larvae are able to survive and grow at freezing temperatureseven under high pressures found in the deep sea (Tyler et al, 2000), where many species have pelagic, planktotrophic larvae (Gage and Tyler, 1991;however, see below).…”

“…This notion was persuasively reinforced by Thorson (1936Thorson ( , 1950, who focused on gastropods in the Northern Hemisphere, and Mileikovsky (1971), who termed it "Thorson's rule." Both Thorson (1936) and Mileikovsky (1971), however, recognized many exceptions, and subsequently, with more information and reanalyses of earlier data, the generality of Thorson's rule weakened substantially (Pearse et al, 1991;Clarke, 1992;Hain and Arnaud, 1992;Pearse, 1994;Young, 1994;Stanwell-Smith et al, 1999;Arntz and Gili, 2001;Schluter and Rachor, 2001;Absher et al, 2003;Sewell, 2005;Vázquez et al, 2007;Fetzer and Arntz, 2008). We now know that many of the most abundant species in Antarctic waters, especially those in shallow water, have pelagic larvae as in other areas of the world.…”

Abundance and distribution of invertebrate larvae in the Bellingshausen Sea (West Antarctica)

“…Although most benthic invertebrates display indirect development, with pelagic larval stages at temperate latitudes, the lack of larvae in polar waters led to believe that Antarctic benthic invertebrates reproduce without a planktonic stage (Murray 1895;Thorson 1950). However, recent studies in the Southern Ocean have revealed a relatively high diversity and abundance of larval forms (Shreeve and Peck 1995;Stanwell-Smith et al 1999;Arntz and Gili 2001;Absher et al 2003;Sewell 2005;Freire et al 2006;Vázquez et al 2007;Bowden et al 2009), some of which are planktotrophic. Moreover, some of the most abundant species in these cold-water habitats reproduce seasonally, usually in late winter and early spring, so that the planktotrophic larvae coincide with the summer phytoplankton bloom (Pearse et al 1991;Stanwell-Smith et al1999;Pearse and Bosch 2002;Pearse and Lockhart 2004;Bowden et al 2009).…”

The meroplankton communities from the coastal Ross Sea: a latitudinal study

“…Latitude does not appear to be a driver of the observed patterns in the meroplankton, and we hypothesize that the nature of the benthic assemblages (Gallego et al, 2014), hydrographical conditions (e.g. Vázquez et al, 2007) and/or levels of primary production (Ameneiro et al, 2012) may be of more importance. Companion studies on variation of benthic assemblages along the Victoria Land Coast (Cummings et al, , 2010Rehm et al, 2006;Thrush et al, 2006;Rehm et al, 2011) have shown that most of the benthic variation occurs on the local scale-metres to hundreds of metres within sites -and that latitude is not a main driver of change in community composition (Cummings et al, 2010).…”