Review of recent trends in ecological studies of deep-sea meiofauna, with focus on patterns and processes at small to regional spatial scales

Abstract

Meiofauna are an important component of deep-sea benthic communities because they are highly abundant and play an important role in the sediment. This review describes trends in the ecology of deep-sea meiofauna based on results from studies published since the review by Soltwedel (2000), with a focus on spatial distribution patterns of deep-sea meiofauna communities at regional (~100–10,000 km), habitat (~0.1–100 km), local (~0.1–100 m), and small scales (~0.1–10 cm), and with reference to the effects of environmental variables and disturbance (biological and human) that influence these patterns. The focus of deep-sea meiofauna studies has shifted from investigations of patterns related to water depth, regions, and vertical gradients in the sediment to the effect of deep-sea habitats on meiofauna communities, the relative importance of different spatial scales, and the relative impacts of disturbance on meiofauna communities. Although deep-sea meiofauna community attributes (abundance, diversity, and community structure) are shown to vary across all spatial scales, the greatest variability is generally observed at regional and sediment depth scales. However, generalisations are difficult to make due to the limited number of studies that allow direct comparisons across multiple scales. At the regional scale, variation in meiofaunal communities appears mostly related to differences in surface productivity, other food proxies, and physical disturbance; however, geological history, oceanographic boundaries and ocean current flows may also contribute to regional patterns. At the small sediment depth scale, meiofauna communities are typically influenced by food proxies, oxygen availability, sediment characteristics, seafloor topography proxies, microhabitat heterogeneity, and bioturbation by larger fauna. Overall, there have been a limited number of studies of small horizontal scale patterns, at seamounts, and in certain geographic regions such as the Indian Ocean and Antarctica. Fewer studies have been conducted in deep ocean basins compared to continental margin. Most studies have focused on nematodes, while other meiofauna taxa such as harpacticoid copepods have not been investigated as often in deep-sea ecological studies. The findings of this review provide a new perspective on the state of knowledge of the factors influencing meiofauna in the deep-sea ecosystem, and highlights the need for future meiofauna studies to provide information that can assist the management of human activities in vulnerable deep-sea areas.