Exploring the Relationship between Macrofaunal Biodiversity and Ecosystem Functioning in the Deep Sea

Abstract

The global scale of the biodiversity crisis has stimulated research into the relationship between biodiversity and ecosystem functioning (BEF). Even though the deep sea is the largest biome on Earth, BEF studies in deep-sea benthic ecosystems are scant. Moreover, the small number of recent studies, which mostly focus on meiobenthic nematodes, report conflicting results that range from a very clear positive relationship to none at all. In this BEF study, the deep-sea macrofauna were used as a model to investigate the structural and functional diversity of macrofauna assemblages at three depths (1,200, 1,900, and 3,000 m) in seven open-slope systems from the North-Eastern Atlantic Ocean to the Central-Eastern Mediterranean Sea. The presence and nature of BEF relationships were studied considering two spatial scales, the large and the basin scale, in different environmental settings. Total benthic biomass and macrofaunal predator biomass were used as proxies to assess ecosystem functioning. Ecosystem efficiency was expressed as macrofaunal biomass to biopolymeric carbon content ratio, macrofaunal biomass to prokaryotic biomass ratio, macrofaunal biomass to meiofaunal biomass ratio, and meiofaunal biomass to prokaryotic biomass ratio. On both large and basin spatial scales, some significant relationships between macrofaunal diversity and ecosystem functioning and efficiency were reported. When significant, the nature of BEF relations was positive and exponential or linear supporting the general idea that a higher diversity can enhance ecosystem functioning. Other BEF relationships were explained by the effect of environmental variables. More data from different deep-sea systems are needed, to better elucidate the consequences of biodiversity loss on the ocean floor.

In Search of a Field-Based Relationship Between Benthic Macrofauna and Biogeochemistry in a Modern Brackish Coastal Sea

“…The significant positive relationship between biogenic mixing depth sensu Solan et al (2004) and sulfide appearance depth found in our study is in agreement with findings of Sturdivant and Shimizu (2017) who showed a match between the burrow depth and the aRPD values (apparent color redox-potential discontinuity). Our results also support the conclusions of the previous studies that found BPc to be a good proxy for ecosystem efficiency (e.g., Baldrighi et al, 2017). According to Cozzoli (2016), metabolic energy will be spent on sediment reworking independent of the type of bioturbation, in order to obtain food, resulting in sediment mixing and the exposure of fine particles to the surface, where they can be resuspended.…”

Relationships between biodiversity and ecosystem functioning proxies strengthen when approaching chemosynthetic deep-sea methane seeps

“…That we did not find evidence for increasingly positive relationships between biodiversity and proxies for ecosystem functioning in background deep-sea habitats ( figure 2 ) is in contrast with our predictions and the findings of several studies [ 18 , 22 , 23 , 53 , 54 ]. Many of these studies emphasize the importance of facilitation in structuring deep-sea ecosystems [ 4 , 18 , 21 ].…”

“…The shape of BEF relationships has been shown to vary even within photosynthesis-based ecosystems and taxonomic groups [ 20 ]. For example, positive BEF relationships in deep-sea nematode assemblages have variously been reported to be linear, asymptotic (saturating) or exponential (accelerating) in form [ 18 , 21 – 23 ]. Understanding the drivers of this variability is key to determining how rapidly ecosystem functioning may be lost with declining biodiversity as a result of natural or anthropogenic changes ( figure 1 ; electronic supplementary material, figure S1), with important implications for the effective management of natural environments

Figure 1 Hypotheses for the form of BEF relationships in contrasting deep-sea environments; lower resource photosynthetically dependent background habitat: grey line, accelerating form; transitional ‘chemotone’ habitat: orange line, linear form; higher resource chemosynthetically dependent methane seep habitat: red line, saturating form.

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How to Promote University Students to Innovative Use Renewable Energy? An Inquiry-Based Learning Course Model

“…In the process of dynamic social change, the role of teachers should also be re-positioned. For university RES courses, teachers should not only be the translators of knowledge but also guiders to promote the development of the world's RES research [48][49][50][51][52]. Due to the limited teaching experience and professional cognition of teachers in RES courses, in practice, there are obvious problems such as incorrect role positioning, backward teaching methods, and insufficient attention.…”