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Journal of Experimental Marine Biology and Ecology 247 2000 85–97
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Ecology and energetics of two Antarctic sponges
Jens Kowalke
Alfred Wegener Institute of Polar and Marine Research , Columbusstrasse, 27515 Bremerhaven, Germany
Received 8 October 1999; received in revised form 2 December 1999; accepted 20 December 1999
Abstract
Retention efficiencies, pumping and respiration rates of the two Antarctic sponge species Mycale acerata and Isodictya kerguelensis from Potter Cove, King George Island, were measured.
None of the species reached a 100 retention efficiency at any given particle size. This is probably due to the sediment-laden environment in which the animals were dwelling. A less
efficient retention decreases the risk of the filtering structures being clogged. Both species filter
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down into the bacterial size range. Pumping rates of the species were 180 ml h M
. acerata and
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220 ml h I
. kerguelensis per g ash free dry mass T 5 18C, being lower than measured in
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temperate water species. Oxygen consumption was 0.088 ml O h M
. acerata; T 5 1.88C and
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0.035 ml O h I
. kerguelensis; T 5 18C per g ash free dry mass.
2000 Elsevier Science
2
B.V. All rights reserved.
Keywords : Antarctica; Sponges; Retention efficiency; Pumping rate; Respiration rate
1. Introduction
Sponges account for a major proportion of Antarctic soft and hard bottom dwellers Voss, 1988; Barthel and Gutt, 1992; Starmans, 1997 and more than 300 species have
been described for the Southern Ocean of which 50 are endemic Koltun, 1970. Six species of hexactinellids dominate the Weddell Sea shelves Barthel and Tendal, 1994.
These animals structure the shelf habitats forming ‘multi-storied assemblages’ Gutt and Schickan, 1998 which form important secondary substrata for holothurians, crinoids,
¨ crustaceans and fishes Dearborn, 1977; Wagele, 1988; Barthel et al., 1991; Kunzmann,
1996; Barthel, 1997. Sponges have described as important benthos constituents from
Tel.: 149-471-4831-313; fax: 149-471-4831-149. E-mail address
: jkowalkeawi-bremerhaven.de J. Kowalke 0022-0981 00 – see front matter
2000 Elsevier Science B.V. All rights reserved.
P I I : S 0 0 2 2 - 0 9 8 1 0 0 0 0 1 4 1 - 6
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. Kowalke J. Exp. Mar. Biol. Ecol. 247 2000 85 –97
shallow waters around the Antarctic Peninsula King George Island: Sahade et al., 1998; Livingston Island: Saiz-Salinas et al., 1997; Signy Island: Barnes, 1995 and the
McMurdo Sound Dayton, 1978, but are, with the exception of McMurdo Sound, less numerous.
Sponges can be considered as a singular filter system, as the whole body functions as a filter. The water flows via numerous ostia formed by porocytes into branching
channels, which end in choanocyte chambers generating the water flow. From these chambers the water is discharged into outflowing channels into one or several osculae.
Particle uptake takes place at three different levels Johnston and Hildemann, 1982. The maximum size of filterable particles, around 50 mm, is determined by the diameter of the
ostia. Food particles as small as 1 mm are taken up through more or less specialised cells archaeocytes in the transmitting channels. Particles around 1 mm are filtered by the
bases of the choanocytes and particles down to 0.1 mm from microvilli, which form the choanocyte collar. Sponges are obviously unable to filter selectively and take up
particles regardless of their nutritive value Kilian, 1952; Reiswig, 1971; Wolfrath and Barthel, 1989.
Schmidt 1970 and Reiswig 1990 have shown that assimilation of dissolved organic material by choanocytes may also take place.
The food spectrum of Antarctic sponges is little known through a paucity of studies. Gaino et al. 1994 found diatoms, both of pelagic and benthic origin, in the cortex of
two Antarctic species, which shall act as an additional skeleton and, during the nutrient ¨
poor Antarctic winter, as a food reserve. Kloser personal communication found up to 70 of benthic diatoms in different sponges of nearby Maxwell Bay, King George
Island. Potter Cove is not a favourable habitat for sponges, as inorganic particles are abundant
in the water column throughout the year Kowalke, 1998, 1999. The same could be stated for the entire Antarctic Peninsula region, as glacial melting during spring and
summer bring sediments into the water column. Sponges, which are not able to close their inflowing channels, suffocate more easily than ascidians or bivalves, which can
better manage these concentrations of inorganic suspended material. Sponges thus play a major role in habitats without heavy sedimentation — the shelf areas and high Antarctic
sites like McMurdo Sound Dayton and Oliver, 1977; Barry, 1988.
Nevertheless six species of sponges were found to dwell on the soft bottoms of Potter Cove Kowalke, 1998. Mycale acerata, an important and fast growing species in
Antarctic shallow waters Dayton et al., 1974, occurs in densities of 0.02 individuals
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m and has a biomass of 5.83 g m
ash free dry mass unpublished data. It grows sporadically, but in colonies up to 1.5 m in height Kowalke, 1998. Although M
. acerata contains secondary metabolites, which are at least highly toxic for fishes, it is
predated by asteroids McClintock, 1987. Isodictya kerguelensis occurs in densities of
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0.10 individuals m and its ash free dry mass is 0.69 g m
in 30 m depth unpublished data.
In this investigation, retention efficiency, pumping rate and oxygen consumption of the two species Mycale acerata and Isodictya kerguelensis of Potter Cove King George
Island were measured to helping explain the differences in abundance and biomass.
J . Kowalke J. Exp. Mar. Biol. Ecol. 247 2000 85 –97
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2. Material and methods
