Exploring Biodiversity and Trophic Ecology in Portuguese Submarine Canyons

1. The Portuguese Submarine Canyons: biodiversity and trophic ecology Marina R Cunha, T Amaro, A Aranda, D van Oevelen, D Billett CESAM Centro de Estudos do Ambiente e do Mar Laboratório Associado|www.cesam.ua.pt

2. Submarine canyons Canyons are complex and heterogeneous systems in terms of topography, hydrography, sedimentology and biogeochemistry and their biological communities remain practically unknown. Canyons were therefore a prioritary target of the HERMES project. The Nazaré canyon, one of the largest submarine canyons in the world, is located is the Portuguese margin. Courtesy of IH

3. Submarine canyons Relevance Canyons are often referred to as depocenters and/or conduits for transport of particulate matter to the deep-sea and are recognised as organic enriched environments. Suspended particle load above the seabed in the axis of Nazaré canyon Tyler et al. 2010 Oceanography, 22

4. Submarine canyons Relevance Canyons also exhibit high levels of hydrodynamic disturbance. subsequent sediment gravity flow event tidal current peaks Middle section of Nazaré canyon (~3400m)

5. Biological research on the Portuguese canyons Megafauna – ROV observations The steep sides of the Nazaré canyon were dominated by a mixture of suspension and deposit feeders attached to the rock walls or in the sediments. Tyler et al. 2010 Oceanography, 22

6. The Portuguese canyons Particular assemblages Biodiversity studies Holothurian heaven at 3400m in Nazaré Giant Protozoa (Xenophyophores) at 4300m in Nazaré Trophic studies

7. Biodiversity Foraminifera Some examples of new Foraminifera species recently described Capsammina patelliformis gen. et sp. nov. Bithekammina oculta gen. et sp. nov Ana Aranda da Silva et al. (submitted)

8. 11°W 10°W 9°W 39°N D297 CD179 64PE252 38°N Biodiversity Macrofauna - Sampling Quantitative replicate sampling was carried out in the upper (~1000m), middle (~3400m) and lower (~4300m) sections of the Nazaré, Cascais and Setúbal canyons and at two locations in the open slopes (~1000m)

9. Species Richness 120 100 Echinodermata 80 Arthropoda 60 Annelida Mollusca 40 20 0 NM NL NM NL CM CL SM SL NU CU SU OSN OSS D297 CD179 64PE252 Chaetodermomorpha Holothurida Pholadomyoida Ophiurida Veneroida Decapoda Pterioida Mysidacea Mytiloida Tanaidacea Arcoida Isopoda Nuculoida Cumacea Bivalvia und. Amphipoda Gastropoda Canalipalpata Scaphopoda Aciculata Scolecida Sipuncula Biodiversity Macrofauna The assemblages showed different trends in abundance and biodiversity i) along the depth gradient; ii) between canyons; iii) between canyons and open slopes. 5000 Density (ind.m-2) 4000 3000 2000 1000 0 NM NL NM NL CM CL SM SL NU CU SU OSN OSS D297 CD179 64PE252

10. Biodiversity Macrofauna High density and dominance of the assemblages in the middle section of Nazaré and Setúbal was accompanied by depressed values in the expected species richness resulting in an inverted pattern of the parabolic unimodal bathymetric diversity trend. 70 North and Mid Atlantic 60 50 40 ES (100) 30 20 C S N 10 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Depth Cascais showed a better match to the parabolic trend, but maintained high expected species richness at the lower section

11. Biodiversity Macrofauna – link to organic loading Significant correlation betweenTN and faunal abundance - amount of nitrogen-rich constituents in the sediment may be more relevant than the total organic carbon loading. Significant negative correlation between ES(100) and TOC concentrations - in line with other studies. 10000 2.5 2.0 1000 Density (ind.m-2) 1.5 TN (mg.g-1) 100 (τ=0.714; p<0.05) 1.0 10 0.5 1 0 25 50 20 40 15 (τ=-0.843; p<0.05) 30 E(S100) TOC (mg.g-1) 10 20 5 10 0 0 NM 05 NM NL CM CL SM SL NL 05

12. Trophic ecology Food webs – linear inverse modeling The upper and lower regions are bacterially-dominated; OM input in the middle region is beneficial for deposit-feeding holothurians. The contribution by meiobenthos and macrobenthos was limited in all regions. Upper (8.41) Middle (12.0) Lower (2.48) All carbon flows (mmol C m-2 d-1) Bac Bac Hol maximum value of 1.5 mmol C m-2 d-1 Bac Mei Mei Hol Oevelen et al (submitted)

13. Bacteria Meiofauna Macrofauna Trophic ecology Food webs – fate of secondary production (%) The “meiobenthic food chain” is only loosely connected to the higher trophic levels. Lower Middle Upper Oevelen et al (submitted)

14. Trophic ecology Holothurians In situ trophic experiments followed by collection, dissection and analysis of possible trophic interactions with prokariotes. Amaro et al (submitted)

15. Trophic ecology Holothurians M. musculus use proteins as the main compound being digested Proteins Carbohydrates Lipids in holothurian gut in sediment enzymatic activity

16. Trophic ecology Holothurians M. musculus hosts a high diversity of bacteria that are not present in the sediments. Prokaryote diversity Prokaryote production in sediment in holothurians Prokaryotes are alive and stimulated in the oesophagus and are likely consumed in the gut

17. Conclusions • Organic loading is probably the major driver for the structure and functioning of canyon benthic assemblages. • Diversity is likely to be maintained by variations in food availability and partitioning of resources by different species. • Altered and localised environmental conditions in the Portuguese canyons play an important role and overwrite more general abundance and diversity bathymetric patterns. • Canyons may show multiple patterns of biodiversity in relation to the adjacent margins, generated by complex interactions of several environmental drivers and the differential response of organisms and populations.

18. CESAM DEEP-SEA BIOLOGY TEAM Thank You!