Anthropogenic impacts: Man's effects on the deep sea

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.

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Deep-Sea Ecosystems: Biodiversity and Anthropogenic Impacts

The Law of the Seabed ◽

10.1163/9789004391567_004 ◽

2020 ◽

pp. 36-60

Keyword(s):

Deep Sea ◽

Anthropogenic Impacts

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Species variability and connectivity in the deep sea: evaluating effects of spatial heterogeneity and hydrodynamics

10.5194/bg-2016-134 ◽

2016 ◽

Cited By ~ 2

Author(s):

Lidia Lins ◽

Frederik Leliaert ◽

Torben Riehl ◽

Sofia Pinto Ramalho ◽

Eliana Alfaro Cordova ◽

...

Keyword(s):

Spatial Heterogeneity ◽

Deep Sea ◽

Beta Diversity ◽

Species Coexistence ◽

Anthropogenic Impacts ◽

Alpha Diversity ◽

Continental Margins ◽

Alpha And Beta Diversity ◽

Different Depths ◽

Hydrodynamic Effects

Abstract. Understanding processes responsible for shaping biodiversity patterns on continental margins is an important requirement for comprehending anthropogenic impacts in these environments. Continental margins perform crucial functions which are mainly structured by hydrodynamic effects and surface primary productivity. However, to what extent these processes control benthic local and regional biodiversity remains unclear. In this study, we focused on two isobathic parallel transects to test if food resources arriving at the seafloor and hydrodynamic effects affect alpha and beta diversity at different depths in similar ways. We also examined the potential role of connectivity between both depths as a result of dispersal. This is the first study applying integrative approaches using molecular and morphological techniques in combination with environmental factors to unravel spatial variability and connectivity in relation to depth in the deep sea. Results revealed that high variability in resource availability is directly linked to high alpha diversity and spatial heterogeneity, and that communities dwelling in deeper regions are able to use resources complementarily promoting species coexistence. Our study also demonstrated that higher hydrodynamics at the shallower habitats near the shelf break, as inferred from the high sediment heterogeneity, promoted variation in community structure across stations (higher beta diversity) compared to the deeper area. In addition, phylogenetic relationships revealed no evidence for depth-endemic lineages or isolation per habitat, indicating regular species interchanges across different depths.

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From sea surface to seafloor: a benthic allochthonous eDNA survey for the abyssal ocean

10.1101/2020.05.07.082602 ◽

2020 ◽

Cited By ~ 1

Author(s):

Olivier Laroche ◽

Oliver Kersten ◽

Craig R. Smith ◽

Erica Goetze

Keyword(s):

Water Column ◽

Deep Sea ◽

Anthropogenic Impacts ◽

Spatial Scales ◽

Deep Ocean ◽

Environmental Dna ◽

Benthic Boundary Layer ◽

Large Sample Size ◽

Polymetallic Nodule ◽

Nodule Mining

AbstractDiverse and remote deep-sea communities are critically under-sampled and increasingly threatened by anthropogenic impacts. Environmental DNA (eDNA) metabarcoding could facilitate rapid and comprehensive biotic surveys in the deep ocean, yet many aspects of the sources and distribution of eDNA in the deep sea are still poorly understood. In order to examine the influence of the water column on benthic eDNA surveys in regions targeted for deep-sea polymetallic nodule mining, we investigated the occurrence of pelagic eDNA across: (1) two different deep-sea habitat types, abyssal plains and seamounts, (2) benthic sample types, including nodules, sediment, and seawater within the benthic boundary layer (BBL), and (3) sediment depth horizons (0-2 cm, 3-5 cm). Little difference was observed between seamounts and the adjacent abyssal plains in the proportion of legacy pelagic eDNA sampled in the benthos, despite an > 1000 m depth difference for these habitats. In terms of both reads and amplicon sequence variants (ASVs), pelagic eDNA was minimal within sediment and nodule samples (< 2%), and is unlikely to affect benthic surveys that monitor resident organisms at the deep seafloor. However, pelagic eDNA was substantial within the BBL (up to 13 % ASVs, 86% reads), deriving both from the high biomass upper ocean as well as deep pelagic residents. While most pelagic eDNA found in sediments and on nodules could be sourced from the epipelagic for metazoans, protist legacy eDNA sampled on these substrates appeared to originate across a range of depths in the water column. Some evidence of eDNA degradation across a vertical sediment profile was observed for protists, with higher diversity in the 0-2 cm layer and a significantly lower proportion of legacy pelagic eDNA in deeper sediments (3-5 cm). Study-wide, our estimated metazoan sampling coverage ranged from 40% to 74%, despite relatively large sample size. Future deep-sea eDNA surveys should examine oceanographic influences on eDNA transport and residence times, consider habitat heterogeneity at a range of spatial scales in the abyss, and aim to process large amounts of material per sample (with replication) in order to increase the sampling coverage in these diverse deep ocean communities.

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Natural Variability Versus Anthropogenic Impacts on Deep-Sea Ecosystems of Importance for Deep-Sea Mining

Perspectives on Deep-Sea Mining ◽

10.1007/978-3-030-87982-2_11 ◽

2022 ◽

pp. 281-311

Author(s):

Teresa Radziejewska ◽

Kamila Mianowicz ◽

Tomasz Abramowski

Keyword(s):

Deep Sea ◽

Anthropogenic Impacts ◽

Natural Variability

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Identifying Priorities for the Protection of Deep Mediterranean Sea Ecosystems Through an Integrated Approach

Frontiers in Marine Science ◽

10.3389/fmars.2021.698890 ◽

2021 ◽

Vol 8 ◽

Author(s):

Emanuela Fanelli ◽

Silvia Bianchelli ◽

Federica Foglini ◽

Miquel Canals ◽

Giorgio Castellan ◽

...

Keyword(s):

Mediterranean Sea ◽

Deep Sea ◽

Oil And Gas ◽

Anthropogenic Impacts ◽

Integrated Approach ◽

Conservation Strategy ◽

Oil And Gas Exploration ◽

Shelf Slope ◽

Key Species ◽

The Status

Benthic habitats of the deep Mediterranean Sea and the biodiversity they host are increasingly jeopardized by increasing human pressures, both direct and indirect, which encompass fisheries, chemical and acoustic pollution, littering, oil and gas exploration and production and marine infrastructures (i.e., cable and pipeline laying), and bioprospecting. To this, is added the pervasive and growing effects of human-induced perturbations of the climate system. International frameworks provide foundations for the protection of deep-sea ecosystems, but the lack of standardized criteria for the identification of areas deserving protection, insufficient legislative instruments and poor implementation hinder an efficient set up in practical terms. Here, we discuss the international legal frameworks and management measures in relation to the status of habitats and key species in the deep Mediterranean Basin. By comparing the results of a multi-criteria decision analysis (MCDA) and of expert evaluation (EE), we identify priority deep-sea areas for conservation and select five criteria for the designation of future protected areas in the deep Mediterranean Sea. Our results indicate that areas (1) with high ecological relevance (e.g., hosting endemic and locally endangered species and rare habitats),(2) ensuring shelf-slope connectivity (e.g., submarine canyons), and (3) subject to current and foreseeable intense anthropogenic impacts, should be prioritized for conservation. The results presented here provide an ecosystem-based conservation strategy for designating priority areas for protection in the deep Mediterranean Sea.

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