Inge van den Beld

Ecological Role of Submarine Canyons and Need for Canyon Conservation: A Review

Submarine canyons are major geomorphic features of continental margins around the world. Several recent multidisciplinary projects focused on the study of canyons have considerably increased our understanding of their ecological role, the goods and services they provide to human populations, and the impacts that human activities have on their overall ecological condition. Pressures from human activities include fishing, dumping of land-based mine tailings, and oil and gas extraction. Moreover, hydrodynamic processes of canyons enhance the down-canyon transport of litter. The effects of climate change may modify the intensity of currents. This potential hydrographic change is predicted to impact the structure and functioning of canyon communities as well as affect nutrient supply to the deep-ocean ecosystem. This review not only identifies the ecological status of canyons, and current and future issues for canyon conservation, but also highlights the need for a better understanding of anthropogenic impacts on canyon ecosystems and proposes other research required to inform management measures to protect canyon ecosystems.

Cold-Water Coral Habitats in Submarine Canyons of the Bay of Biscay

The topographical and hydrological complexity of submarine canyons, coupled with high substratum heterogeneity, make them ideal environments for cold-water coral (CWC) habitats. These habitats, including reefs, are thought to provide important functions for many organisms. The canyons incising the continental slope of the Bay of Biscay have distinct morphological differences from the north to the south. CWCs have been reported from this basin in the late 19th century; however, little is known about their present-day distribution, diversity and environmental drivers in the canyons. In this study, the characteristics and distribution of CWC habitats in the submarine canyons of the Bay of Biscay are investigated. Twenty-four canyons and three locations between adjacent canyons were sampled using a Remotely Operated Vehicle (ROV) or a towed camera system. Acquired images were annotated for habitat type (using the CoralFISH classification system), substrate cover and coral identification. Furthermore, the influence of hydrological factors and geomorphology on the CWC distribution was investigated. Eleven coral habitats, formed by 62 morphotypes of scleractinians, gorgonians, antipatharians and seapens, inhabiting hard and/or soft substrate, were observed. The distribution patterns were heterogenous at regional and local scales; the south Bay of Biscay and the southeastern flank favored soft substrate habitats. Biogenic and hard substrate habitats supported higher coral diversities than soft substrate habitats and had similar species compositions. A higher coral species turnover characterized soft substrate habitats. Substrate type was the most important driver of the patterns in both distribution and composition. Observations of coral reefs on steeper areas in the canyons and coral rubble on flatter areas on the interfluve/upper slope, support the hypothesis that canyons serve as refuges, being less accessible to trawling, although natural causes may also contribute to the explanation of this distribution pattern. The results of this study fed into a proposal of a Natura 2000 network in the Bay of Biscay where management plans are rare.

The Impact of Anthropogenic Activity on Cold-Water Corals

Various human activities can have an impact on cold-water coral (CWC) habitats. Bottom trawling has been shown to degrade these habitats and, in some cases, to cause extensive damage. Among static fishing gears, bottom longlines and gillnets can be set directly on coral grounds. Intensive fishing with these gears, while having much less impacts compared to bottom trawls, may over time cause damage to CWC habitats. Current plans to begin mineral mining activities in the deep sea will pose a risk to CWC habitats due to substrate removal and smothering by toxic particulate waste material. The by-products of oil exploitation, including drill cuttings, drill mud, and wastewater discharge, can impact CWC habitats, for example, causing reduced polyp activity and growth. Effects of accidental oil spills, if occurring in the vicinity of CWC habitats, include partial tissue loss and ultimately death. Litter may affect CWC colonies in a variety of ways, e.g. smothering and entanglement in discarded plastic and lost fishing gear. Submarine cables can exert localized impacts on CWC habitats particularly during their installation, repair, and removal. Potential impacts of CWC exposure to radioactive waste are unknown, but leakages in their vicinity would represent a threat. The impact of increasing CO2-induced global warming and ocean acidification is species-specific. While accurately predicting future effects is difficult, reduced availability of suitable habitats and weaker skeletal strength of reefforming species are to be expected. Evaluating the risk posed by human activities to CWCs remains a challenge, given the remoteness of these habitats.

A further record of the rare hippolytid shrimp Leontocaris lar Kemp, 1906 (Decapoda, Caridea) from the Celtic Sea, off north-western France

Members of the deep-sea caridean shrimp genus Leontocaris Stebbing, 1905 (family Hippolytidae Spence Bate, 1888) have a very peculiar major second cheliped with a massive palm bearing a tympanum and a blade-like dactylus, probably related to an as yet unknown predatory behaviour (Taylor & Poore, 1998; Fransen, 2001; Poore, 2009). Currently nine species are known in the genus (De Grave & Fransen, 2011; Cardoso & Fransen, 2012). In North Atlantic waters only one species, Leontocaris lar Kemp, 1906 has been reported and up to now, remains only known from three specimens collected off Ireland more than a century ago (Kemp, 1906, 1910; d’Udekem d’Acoz, 1999). The rarity of this species, and indeed all known species in the genus, is likely due to these shrimps inhabiting deep-sea coralline habitats, which are very difficult to sample by conventional means (Kemp, 1906, 1910; Taylor & Poore, 1998; Fransen, 2001; Poore, 2009; Ahyong, 2010; Cardoso & Fransen, 2012). In 2011, during a ROV “Victor6000” dive of the “BobEco” cruise carried out on board the RV “Pourquoi Pas?” (chief scientist: S. Arnaud-Haond, Ifremer), a further specimen was collected in the Celtic Sea off north-western France, allowing for a better understanding on the characteristics and ecology of this rare species. In situ observation of L. lar confirms for the first time its association with antipatharian corals. A close examination of the present specimen reveals that the recently described Leontocaris smarensis Cardoso & Fransen, 2012, from the South MidAtlantic Ridge is extremely similar to L. lar, potentially being a synonym of L. lar.