Ancient deep-sea sponge grounds on the Flemish Cap and Grand Bank, northwest Atlantic

Abstract

Recent studies on deep-sea sponges have focused on mapping contemporary distributions while little work has been done to map historical distributions; historical distributions can provide valuable information on the time frame over which species have co-evolved and may provide insight into the reasons for their persistence or decline. Members of the sponge family Geodiidae are dominant members of deep-sea sponge assemblages in the northwestern Atlantic. They possess unique spicules called sterrasters, which undergo little transport in sediment and can therefore indicate the Geodiidae sponge historical presence when found in sediment cores. This study focuses on the slopes of Flemish Cap and Grand Bank, important fishing grounds off the coast of Newfoundland, Canada, in international waters. Sediment cores collected in 2009 and 2010 were visually inspected for sponge spicules. Cores containing spicules were sub-sampled and examined under a light microscope for the presence of sterrasters. These cores were also dated using X-radiographs and grouped into five time categories based on known sediment horizons, ranging from 17,000 years BP to the present. Chronological groupings identified Geodiidae sponges in four persistent sponge grounds. The oldest sterrasters were concentrated in the eastern region of the Flemish Cap and on the southeastern slope of the Grand Bank. Opportunistic sampling of a long core in the southeastern region of the Flemish Cap showed the continuous presence of sponge spicules to more than 130 ka BP. Our results indicate that the geodiids underwent a significant range expansion following deglaciation, and support a contemporary distribution that is not shaped by recent fishing activity.

Marine epibenthic functional diversity on Flemish Cap (north‐west Atlantic)—Identifying trait responses to the environment and mapping ecosystem functions

“…Functional redundancy is an important factor for maintaining ecosystem conditions when faced with environmental disturbances (Standish et al, 2014). In the present study, the high functional redundancy observed in the deep-sea sponge communities (assemblage III.c) could have enabled the persistence of the sponge grounds in the area for more than 17,000 years (Murillo, Kenchington, Lawson, Li, & Piper, 2016)…”

“…Functional redundancy is an important factor for maintaining ecosystem conditions when faced with environmental disturbances (Standish et al, ). In the present study, the high functional redundancy observed in the deep‐sea sponge communities (assemblage III.c) could have enabled the persistence of the sponge grounds in the area for more than 17,000 years (Murillo, Kenchington, Lawson, Li, & Piper, ) and could help ensure their survival under future climate change conditions. However, this community and others with high redundancy in the Flemish Cap have biological traits such as large size, long life span and/or no mobility (sessile), that are very vulnerable (sensu FAO, ) to bottom‐contact fishing activities.…”

Distribution and diversity of deep-sea sponge grounds on the Rosemary Bank Seamount, NE Atlantic

“…Sponge grounds are thus recognised as important drivers of biodiversity and ecological function in deep-sea ecosystems (Hogg et al 2010). Deep-sea sponge grounds may take millennia to form (Murillo et al 2016), and individual sponges may take decades to grow (Pusceddu et al 2014). Consequently, they are vulnerable to chronic disturbance from human activities such as bottom trawling.…”

Influence of Water Masses on the Biodiversity and Biogeography of Deep-Sea Benthic Ecosystems in the North Atlantic

“…One of the first reports of these habitats was by Rice et al (1990), who observed dense aggregations (density values ∼1.5 ind•m −2 ) of the hexactinellid Pheronema carpenteri (Figure 2) in the Porcupine Seabight (NE Atlantic). Subsequently, records of sponge grounds came both from the eastern (e.g., Klitgaard and Tendal, 2004;Howell et al, 2016;Roberts et al, 2018;Kazanidis et al, 2019) and western deep North Atlantic (e.g., Murillo et al, 2012Murillo et al, , 2016aMurillo et al, , 2018Knudby et al, 2013;Kenchington et al, 2014;Beazley et al, 2018). These included records not only of hexactinellids, but also of demosponges and especially those from the family Geodidae (Order Astrophorida, commonly known as ostur; Figure 2).…”

“…As the NAC and Irminger Currents (Figure 1) are integral to the AMOC (Cuny et al, 2002), any changes in this circulation may impact the distribution of deep-water sponges. Interestingly, geodiid sponge grounds off the Flemish Cap and Grand Banks have persisted for the last 130 kya (Murillo et al, 2016a), despite large shifts in water mass structure alternating between the warmer Atlantic waters and the cooler Labrador Current. Murillo et al, 2018 further noted that the structureforming Geodia species were found in areas with high primary production and fast currents that would provide the high food supply needed to reach their large biomasses.…”