Search

Ecological studies about marine benthic communities received a major leap from the application of a variety of non-destructive sampling and mapping techniques based on underwater image and video recording. The well-established scientific diving practice consists in the acquisition of single path or 'round-trip' over elongated transects, with the imaging device oriented in a nadir looking direction. As it may be expected, the application of automatic image processing procedures to data not specifically acquired for 3D modelling can be risky, especially if proper tools for assessing the quality of the produced results are not employed. This paper, born from an international cooperation, focuses on this topic, which is of great interest for ecological and monitoring benthic studies in Antarctica. Several video footages recorded from different scientific teams in different years are processed with an automatic photogrammetric procedure and salient statistical features are reported to critically analyse the derived results. As expected, the inclusion of oblique images from additional lateral strips may improve the expected accuracy in the object space, without altering too much the current video recording practices. [ABSTRACT FROM AUTHOR]

Ampharetidae Malmgren, 1866 is a polychaete family of deposit-feeder species that flourishes in terms of individuals/m2and species richness in areas where large quantities of food may accumulate, such as Arctic and Antarctic fjords. Despite the common occurrence of ampharetids in benthic samples and their important ecological role, the nomenclatural status of several species and subspecies is unclear and a general revision of the family is highly needed. In this contribution we focus on the ampharetid genusAmphicteisGrube, 1850, assessing the status of the species currently included in it and describing a new one,Amphicteis teresaesp. nov., collected at Terra Nova Bay (Ross Sea, Antarctica). The new species has blunt and stout paleal chaetae, a feature that is known to occur only in northern hemisphereAmphicteiscounterparts. The new species closely resemble the ArcticA. ninonaeJirkov, 1985, to which it could also be phylogenetically related. The morphological re-analysis of theAmphicteistaxa showed that the subspecies of the purportedly cosmopolitanA. gunneri(M. Sars, 1835), which were mainly based on a geographical criterion, represent valid species. Molecular data will indeed be needed to define phylogeographic relationships within this widespread genus. http://zoobank.org/urn:lsid:zoobank.org:pub: 7F9E0E76-3168-439B-A45E-861F5CF77126 [ABSTRACT FROM AUTHOR]

Living diatoms are commonly found within Antarctic Porifera, and generally interpreted as additional food source, or as mutualists or parasites of sponge tissues. However, no data are available about temporal variations of the abundance of diatoms inside sponges especially during the winter period. In this paper we analysed the amount of diatom frustules and chlorophaeopigment concentration in six species of Antarctic sponges (Dendrilla antarctica, Homaxinella flagelliformis, Kirkpatrickia variolosa, Suberites montiniger, Haliclona dancoi, Haliclona penicillata) sampled weekly from November 2001 ­ before the ice melting ­ to February 2002. Frustule concentration in the sponge tissues was very low at the beginning of November in all the sponge species, and increased between 9 and 22 January, to reach maximum values between 29 January and 7 February. Diatom abundances were significantly higher in H. dancoi tissues, comparing to the other sponge species, reaching values up to 1217±178 cells *106 g-1 dw at the end of January. Chlorophaeopigments, very low at the beginning of November, increased between 5 and 19 December, before the peak of diatoms. Maximum chlphaeo values (650.5±5.9 μg g-1 dw) were observed in D. antarctica. The planktonic Fragilariopsis curta was the most common diatom species recorded inside sponges. These data clearly indicate that diatom concentration inside the sponge tissues is related to the summer phytoplankton bloom. The shift between the pigment and frustule peaks strongly suggests that diatoms are used as a food source by sponges and that their frustules are accumulated inside the sponge body. The lack of frustules at the beginning of summer indicates that diatom frustules are expelled or dissolved during the cold season. [ABSTRACT FROM AUTHOR]