Mark A. Shields

Does Presence of a Mid-Ocean Ridge Enhance Biomass and Biodiversity?

In contrast to generally sparse biological communities in open-ocean settings, seamounts and ridges are perceived as areas of elevated productivity and biodiversity capable of supporting commercial fisheries. We investigated the origin of this apparent biological enhancement over a segment of the North Mid-Atlantic Ridge (MAR) using sonar, corers, trawls, traps, and a remotely operated vehicle to survey habitat, biomass, and biodiversity. Satellite remote sensing provided information on flow patterns, thermal fronts, and primary production, while sediment traps measured export flux during 2007–2010. The MAR, 3,704,404 km2 in area, accounts for 44.7% lower bathyal habitat (800–3500 m depth) in the North Atlantic and is dominated by fine soft sediment substrate (95% of area) on a series of flat terraces with intervening slopes either side of the ridge axis contributing to habitat heterogeneity. The MAR fauna comprises mainly species known from continental margins with no evidence of greater biodiversity. Primary production and export flux over the MAR were not enhanced compared with a nearby reference station over the Porcupine Abyssal Plain. Biomasses of benthic macrofauna and megafauna were similar to global averages at the same depths totalling an estimated 258.9 kt C over the entire lower bathyal north MAR. A hypothetical flat plain at 3500 m depth in place of the MAR would contain 85.6 kt C, implying an increase of 173.3 kt C attributable to the presence of the Ridge. This is approximately equal to 167 kt C of estimated pelagic biomass displaced by the volume of the MAR. There is no enhancement of biological productivity over the MAR; oceanic bathypelagic species are replaced by benthic fauna otherwise unable to survive in the mid ocean. We propose that globally sea floor elevation has no effect on deep sea biomass; pelagic plus benthic biomass is constant within a given surface productivity regime.

Polynoid polychaetes of the Mid-Atlantic Ridge and a new holothurian association

Abstract Presented here is a new deep-sea association between the polynoid, Eunoe bathydomus (Ditlevsen, 1917) and the holothurian Deima validum validum Théel, 1879 from the Mid-Atlantic Ridge, North Atlantic. For the first time in the deep-sea two polynoid specimens have been found on a single holothurian host. Genetic data in this study show that E. bathydomus has a distribution ranging across the Mid-Atlantic Ridge over a distance of 72 km, which could have been facilitated by hitchhiking on holothurians, although the main ecological benefits for being associated with a host remain unclear. Additional taxonomic records of polynoid species recovered during remotely operated vehicle Isis sampling during the RRS James Cook cruise JC48 in summer of 2010 are also presented.

An Introduction to Marine Renewable Energy

It is now widely recognized that there is a need for long-term secure and suitable sustainable forms of energy. Renewable energy from the marine environment, in particular renewable energy from tidal currents, wave and wind, can help achieve a sustainable energy future. Our understanding of environmental impacts and suitable mitigation methods associated with extracting renewable energy from the marine environment is improving all the time and it is essential that we distinguish between natural and anthropocentric drivers and impacts.

On the deep-sea Nephasoma species in the Eastern North Atlantic – a taxonomic guide

Abstract Sipuncula is a relatively species-poor phylum that can play a considerable role in soft sediment benthic ecosystems. The ecological and geochemical influence of sipunculans can vary between species. However, identification of sipunculan species is often problematic. This article focuses on sipunculans collected in the Nordic Seas belonging to the genus Nephasoma, a common genus in deep-water collections. A review of Nephasoma taxonomic descriptions in eastern North Atlantic waters and a key to identifying sipunculans found in the region of deep Nordic Seas is provided.