Prosperity and limitation of sponge fauna on the former ice-shelf Larsen A-B and adjacent areas west of the Antarctic Peninsula
Final Report Abstract
Utilising the powerful combination of ROV imagery and taxonomic identification of sponge samples collected by trawls in 2007 and 2011, as well as exhaustive comparisons with reference stations at the Antarctic Peninsula and Eastern Weddell Sea regions, we analyzed the zoogeographic affinities of Larsen AB sponges communities and investigated their role in the re-colonization of this area. The unprecedented colonisation by hexactinellids and demosponges at Larsen A South between 2007 and 2011 was an exception in terms of ecological succession, compared to other sectors of the Larsen AB region at this time. Within just 4 years, a doubling respectively tripling of hexactinellid biomass and abundance at Larsen A South has been observed, thereby highlighting the importance of hexactinellids (Rossella and Anoxycalyx spp.) as pioneers and colonisers in the Larsen AB region. However, comparing with known sponge pioneer species in the Antarctic, it can be seen that there has been a reduction particularly in early pioneer species in Larsen A South from 2007 to 2011, compared to an increase at Larsen B during the same time period. These results highlight the dynamic re-colonisation processes at Larsen AB. The ice-scour sponge assemblages of Snow Hill and Dundee islands are not similar to the Larsen AB ice-shelf collapse region, and some of the AB sponge assemblages are found to be richer in sponges than ice-scour assemblages. With the exception of one Larsen B station, deep-sea sponge species assemblages have little in common with Larsen AB assemblages. Larsen AB sponge assemblages are distinct. They are not a subset of any other of the analysed sponge communities or Antarctic Peninsula communities, although several sites on the shelf in the NE Weddell Sea and Antarctic Peninsula do share similarities with certain richer and more diverse sponge sectors of the Larsen AB region. Microbial screening shows that taxonomically distant sponges from the Antarctic Peninsula exhibit characteristic, rich and diverse bacterial communities. While host-specificity is a found to be a common phenomenon, in this present study one group of different sponge species clustered together in terms of bacterial communities, indicating that in this group of Antarctic cold water sponges the same symbiotic bacteria perform the same metabolic processes in different sponge taxa, which is contrary to earlier findings. Biochemical analysis of the sponges for natural products revealed a wide range of highly bioactive compounds against cancer cells, bacteria, fungi and others. Especially a new class of Discorhabdin alkaloids isolated from two Latrunculia spp., was proven to be an effective cholinesterase inhibitor for treatment of patients with Alzheimer’s disease. Generally, our findings show that Antarctic marine sponges represent a valuable source of biologically active compounds with high pharmacological potential. Analysing environmental variables and sponge assemblages around the Antarctic Peninsula has found that cold and nutrient-rich bottom water support richer sponge communities. This result has implications on sponges and their symbionts in case of future increases of water temperatures in the Southern Ocean.
Publications
- 2013. Rapid glass sponge expansion after climate-induced Antarctic ice helf collapse. Current Biology, Vol. 23. pp. 1330-1334
Fillinger, L., Janussen, D., Lundalv, T., Richter, C.
(See online at https://doi.org/10.1016/j.cub.2013.05.051) - (2014): Porifera. In: C. De Broyer et al. (Eds.), Biogeographic Atlas of the Southern Ocean, Chapter 5.5: 94-102. CAML-SCAR Marine Biodiversity Information Network
Janussen, D. & Downey, R. V.
- (2015): Rossella podagrosa Kirkpatrick, 1907 – A valid species after all.- Zootaxa, 4021 (1): 169–177
Göcke C., Janussen D., Reiswig H. M., Jarrell S.C. & Dayton P.K.
(See online at https://doi.org/10.11646/zootaxa.4021.1.7) - (2016): Macro-epibenthic communities at the tip of the Antarctic Peninsula, an ecological survey at different spatial scales.- Polar biology (2016) 39: 829–849
Gutt J., Alvaro M. C., Barco A., Böhmer A., Bracher A., David B., De Ridder, C., Dorschel B., Eléaume M., Janussen D., Kersken D., López-González P. J. Martínez-Baraldés I., Schröder M., Segelken-Voigt A. & Teixidó N.
(See online at https://doi.org/10.1007/s00300-015-1797-6) - (2016): Screening of the Antarctic marine sponges as a source of bioactive compounds.- Polar Biology 39: 947–959
Berne S., Kalauz M., Lapat M., Savin L., Janussen D., Kersken D., Avguštin J. A., Jokhadar S. Z., Domen Jaklič5, Gunde-Cimerman N., Lunder M., Roškar I. Eleršek T., Turk T. & Sepčić K.
(See online at https://doi.org/10.1007/s00300-015-1835-4) - (2016): Sponge communities of the Antarctic Peninsula - Influence of environmental variables on species composition and richness- Polar Biology (2016) 39: 851–862
Kersken D., Feldmeyer, B. & Janussen D.
(See online at https://doi.org/10.1007/s00300-015-1875-9)
