Biodiversity, community structure and ecosystem function on kelp and wood falls in the Norwegian deep sea

Abstract

Fjordic systems in temperate and Arctic regions often feature extensive kelp forests at their shallow coastal margins as well as extensive terrestrial forests. Detrital export from these shallow-water and terrestrial ecosystems is an important source of carbon for deep-sea communities in the form of kelp and wood falls. Benthic landers with experimental substrates (wood blocks and kelp parcels) were deployed for 10 mo at a depth of 530 m in a deep Norwegian fjord to investigate and compare macro- and megabenthic community structure, biodiversity and ecosystem functioning on kelp and wood falls. Results revealed that while wood and kelp falls can support a similar number of species and abundance of fauna, they support significantly different faunal communities. Biomass and secondary production on both wood and kelp substrates were significantly greater than in the control samples. Secondary production estimates were similar or higher than those reported from soft-sediment ecosystems at shallower European marine sites. Biological trait analysis showed that macrofaunal assemblages were distinct between the kelp and wood, providing evidence for differences in ecosystem function between the substrates. This case study from a deep-sea fjord in Norway provides clear evidence that while wood and kelp organic falls can support similar abundances of fauna, the associated benthic biodiversity, community structure and ecosystem functioning can be dramatically different between these substrates. The work presented here aims to provide information that is useful in assessing the extent of anthropogenic impacts on deep fjord ecosystems with respect to informing future conservation and management strategies.

Depth and substrate type influence community structure and diversity of wood and whale-bone habitats on the deep NE Pacific margin

“…S1 in the Supplement at www.int-res.com/articles/suppl/m687p023_supp.xlsx), and first deployed on the Washington−Oregon margin (this study). Similar landers using the BoWLs design were subsequently deployed in collaborative projects in the SW Atlantic (Saeedi et al 2019 and in a Norwegian fjord (Harbour et al 2021).…”

“…Ophryotrocha spp. in side xylophagaid-bored wood blocks are likely omnivorous, deriving nutrition from the labile faecal material produced by the xylophagaid bivalves, which also may include sulphur-oxidising bacteria (Harbour et al 2021). Xylophagaid faecal material could also be a food source for surface deposit-feeding ampharetids living in the wood borings made by xylophagaids.…”

“…This mass effect very likely inflated community densities, species richness, and dominance in control assemblages. Mass effects can generally increase the abundance and diversity of assemblages in areas near organic falls which should be considered in interpretations of similar organic-fall experiments involving different habitat types in close proximity (Jones et al 2008, Rouse et al 2011, Saeedi et al 2019, Harbour et al 2021. Other than organic-rich species present due to mass effects, control assemblages were dominated by taxa such as mobile crustaceans (Eury copinae sp.…”

Dispersal and Deposition of Detritus From Kelp Cultivation

“…How this POM is dispersed, transported and deposited, depends on a number of factors, including the position and exposure level of the farm site. On the seafloor, kelp POM is a food source for the benthic community (Renaud et al, 2015;Queirs et al, 2019) and/or potentially impacts the fauna community negatively (Campbell et al, 2019;Harbour et al, 2021b). A fraction of the carbon in the POM escapes faunal digestion and microbial degradation and is consequently buried in the seafloor.…”

The frequent occurrence and metabolic versatility of Marinifilaceae bacteria involved in organic matter mineralization as a key member in global deep sea

“…In comparison, little was known about the microbial-mediated mineralization of the large and fast sinking particles, such as oceanic or terrestrial animal and plant tissues like well-known ecosystems of wood-fall, kelp-fall, and whale-fall (15)(16)(17)(18)(19).…”