Sponges are a common sight on tropical reefs where light is abundant and temperatures range from temperate to sub-tropical, yet sponge communities have been noted to thrive at extraordinary depths of up to 1300m (OSPAR, 2010). The temperature at this depth ranges from 4-10 degrees Celsius and the pressure can be up to 129 atm (Bett and Rice, 1992). How these sponges survive in such a harsh environment is one of the many topics that will be researched as this blog develops.
Two main classes of sponge are found in these dark depths; the glass sponge (Hexactinellidae) and the giant sponge (Demospongia). Studies have shown that despite the extreme location of these sponges, the communities show biological diversity that sometimes equals that of communities studied on tropical reefs (Konnecker, 2002). Some of these sponges, particularly stalks of glass sponge, can provide hard substrata to which other species of deep sea fauna can attach (Beaulieu, 2001b). This can increase biodiversity in the immediate area. This is similar to the positive affects shown by the presence of an oyster bed or coral reef in other environments.
Although deep-sea sponges are adapted to cope with the extreme conditions of the depths, they are particularly vulnerable to human activities. Bottom trawling, cable trenching and mineral extraction can destroy sponge communities and recovery from these disruptions can take a very very long time (Cook et al., 2008). It is no surprise then that these sponge communities are listed as a UK priority habitat in the UK Biodiversity Action Plan (BAP). The upcoming tranches of Marine Conservation Zones (MCZs) are currently being assessed with sponge communities in mind (OSPAR, 2010). Restrictions on human activity shall be placed upon these zones depending upon the type of habitat present and the economic impact of restricting such an activity.
This sponge blog aims to start by outlining the biology of sponges and the role they play in the deep sea as ecosystem engineers, before focusing on the glass sponges (Hexactinellidae). Finally, for a summary of all the topics researched within this blog, a conclusions page has been produced.