Is long-term change in the abyssal Northeast Atlantic driven by qualitative changes in export flux? Evidence from selective feeding in deep-sea holothurians

• Main Authors: Wigham, Benjamin D., Hudson, Iain R., Billett, David S.M., Wolff, George A.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2003
• Subjects: Northeast Atlantic
• Online Access: https://eprints.soton.ac.uk/11186/

The Porcupine Abyssal Plain (NE Atlantic) time-series has shown large, wide-scale, changes in the composition of the benthic community at 4800 m depth (48°50?N, 16°30?W). The abundance of holothurians has increased significantly since 1996 and one species in particular, Amperima rosea, has increased in abundance by three orders of magnitude. Environmental forcing in the form of phytodetrital food supply to the benthos is believed to be driving these changes. Chlorophyll and carotenoid pigments were determined from the gut sediments of seven species of abyssal holothurian, sampled from the Porcupine Abyssal Plain during Autumn 2000 and Spring 2002. These two samples fell either side of the main phytoplankton bloom in the NE Atlantic, providing an opportunity for seasonal comparisons. Significant inter-species differences in pigment profiles were observed among the seven species. Seasonal differences were noted among four species sampled in both time periods. All seven species were collected from the same geographical area and depth. As algal pigments cannot be synthesised by the holothurians, they provide good biomarkers for the composition of the phytodetritus. Differences in pigments from gut sediment profiles are indicative of selective feeding among the holothurians. A. rosea had a gut profile dominated by the pigments zeaxanthin, chlorophyll a/echineone and beta-carotene; these pigments were all present in significantly smaller quantities in the other species. The high quantities of these pigments are indicative of a diet rich in cyanobacteria. The gut sediments of A. rosea also lacked many chloropigments characteristic of other phytoplankton groups, which were observed in the guts of other holothurian species. Ovarian tissue for the five species taken in the pre-spring bloom 2002 sample were examined. All species showed similar carotenoid profiles, dominated by zeaxanthin, echinenone and beta-carotene, all of which are important compounds for reproductive success in echinoderms. The differences in gut ...