scholarly journals Bottom-trawling along submarine canyons impacts deep sedimentary regimes

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Sarah Paradis ◽  
Pere Puig ◽  
Pere Masqué ◽  
Xènia Juan-Díaz ◽  
Jacobo Martín ◽  
...  
Keyword(s):  
Continental Margin ◽  
Trophic Status ◽  
Surface Sediments ◽  
Benthic Communities ◽  
Ecological Impacts ◽  
Sedimentation Rates ◽  
Submarine Canyons ◽  
Bottom Trawling ◽  
Sedimentary Environments

Abstract Many studies highlight that fish trawling activities cause seafloor erosion, but the assessment of the remobilization of surface sediments and its relocation is still not well documented. These impacts were examined along the flanks and axes of three headless submarine canyons incised on the Barcelona continental margin, where trawling fleets have been operating for decades. Trawled grounds along canyon flanks presented eroded and highly reworked surface sediments resulting from the passage of heavy trawling gear. Sedimentation rates on the upper canyon axes tripled and quadrupled its natural (i.e. pre-industrialization) values after a substantial increase in total horsepower of the operating trawling fleets between 1960 s and 1970 s. These impacts affected the upper canyon reaches next to fishing grounds, where sediment resuspended by trawling can be transported towards the canyon axes. This study highlights that bottom trawling has the capacity to alter natural sedimentary environments by promoting sediment-starved canyon flanks, and by enhancing sedimentation rates along the contiguous axes, independently of canyons’ morphology. Considering the global mechanisation and offshore expansion of bottom trawling fisheries since the mid-20th century, these sedimentary alterations may occur in many trawled canyons worldwide, with further ecological impacts on the trophic status of these non-resilient benthic communities.

scholarly journals Impacts of bottom trawling on benthic trophic status and meiofauna in a deep-sea sedimentary environment (Gulf of Castellammare, southwestern Mediterranean Sea)

2020 ◽  
Author(s):  
Antonio Pusceddu ◽  
Sarah Paradis ◽  
Davide Moccia ◽  
Pere Puig ◽  
Pere Masque ◽  
...  
Keyword(s):  
Community Composition ◽  
Deep Sea ◽  
Biochemical Composition ◽  
Benthic Communities ◽  
Sedimentary Environment ◽  
Sediment Cores ◽  
Organic Detritus ◽  
Bottom Trawling ◽  
Sedimentary Environments ◽  
The Impact

<p>The impacts of bottom trawling on the structure of benthic communities can be relatively non-selective, hitting biodiversity as a whole. This holds true also in the deep sea, where the impacts of trawling can be more severe and long-lasting than in shallow-waters, due to the reduced capacity for recovery and greater vulnerability of deep-sea organisms. For years, our knowledge of the impact of trawling on deep-water ecosystems has remained limited and has focused mainly on fish stocks and hard bottom systems. More recently, a number of studies have addressed the impacts of bottom trawling in the deep-sea sedimentary environments, and very few of them have focused on the impacts on meiofauna, though it is a key faunal component of deep-sea ecosystems.</p><p>We investigated the impact of bottom trawling on the quantity, biochemical composition and nutritional value of sedimentary organic matter and meiofauna along the Sicilian Margin (Gulf of Castellammare, southwestern Mediterranean) at ca. 550 m depth, during the summer of 2016. Amount, biochemical composition and freshness of sedimentary OM, as well as the abundance and community composition of meiofauna were determined in sediment cores taken at both trawled and untrawled grounds. The continuous erosive processes in the trawled site have led, generally, to the depletion of OM contents (20-60% lower than those in the untrawled site), as well as to statistically significant differences from the untrawled site in its biochemical composition. Nevertheless, the upper 2 cm of the trawled site consisted of recently accumulated sediments, enriched in phytopigments, and bulk OM contents similar to those in the untrawled one, interpreted as a very recent input of fresh OM from the upper water column. The abundance of meiofauna in trawled grounds was significantly higher than that in untrawled ones, whereas no differences were observed between trawled and untrawled grounds deeper in the sediment. Differences in the meiofaunal community composition among sediment layers in each site were larger than those among sites.</p><p>As previously reported, deep bottom trawling in the Gulf of Castellammare erodes large volumes of sediment, exposing old compacted sediment that is depleted in OM. This erosive action generally prevents the accumulation of fresh sediment. However, the episodic short-lived deposition of fresh organic detritus between hauls can lead to a temporary accumulation of fresh and bioavailable OM which, in turn, can induce a positive response in meiofauna abundance.</p><p>These results pinpoint the need of considering the impacts of bottom trawling on the benthic communities of deep-sea sedimentary environments at temporal scales shorter than previously done.</p>

Impact of depositional regimes on biogeochemical cycling of iron and stable Fe signatures in sediments from the Argentina Continental Margin

2020 ◽  
Author(s):  
Anne-Christin Melcher ◽  
Susann Henkel ◽  
Thomas Pape ◽  
Anette Meixner ◽  
Simone A. Kasemann ◽  
...  
Keyword(s):  
Continental Margin ◽  
Water Depth ◽  
Surface Sediments ◽  
Depositional Environments ◽  
Anaerobic Oxidation Of Methane ◽  
Sedimentation Rates ◽  
Biogeochemical Processes ◽  
High Sedimentation ◽  
Terrace Site ◽  
Fe Reduction

<p>The Argentina Continental Margin represents a unique geologic setting where fundamental interactions between bottom currents and sediment deposition as well as their impact on biogeochemical processes and element cycling, in particular iron, can be studied. The aims of this study were to investigate 1) the consequences of different depositional conditions on biogeochemical processes and 2) diagenetic cycling of Fe mineral phases in surface sediments. Furthermore, it was 3) studied how sedimentary stable Fe isotope signatures (δ<sup>56</sup>Fe) are affected during early diagenesis and finally 4) evaluated, under which conditions δ<sup>56</sup>Fe might be used as proxy for microbial Fe reduction in methanic sediments. During RV SONNE expedition SO260, carried out in the framework of the DFG-funded Cluster of Excellence “The Ocean in the Earth System”, surface sediments from two depositional environments were sampled each using gravity corer and multi corer. One study site is located on the lower continental slope at 3605 m water depth (Biogeochemistry Site), while the other site is situated in a contourite system on the Northern Ewing Terrace at 1078 m water depth (Contourite Terrace Site). Sequential Fe extractions were performed on the collected sediments to determine four operationally defined reactive Fe phases targeting Fe carbonates, (easily) reducible Fe (oxyhydr)oxides and hardly reducible Fe oxides [1]. Purification of extracts for δ<sup>56</sup>Fe analysis of the Fe carbonates and easily reducible Fe (oxyhydr)oxide fractions followed [2]. The dataset was combined with pore-water data obtained during the cruise and complemented by concentrations and stable carbon isotope signatures of dissolved methane determined post-cruise. The extent of the redox zonation and depth of the sulfate-methane-transition (SMT) differ between the two sites. It is suggested that sedimentation rates at the Biogeochemistry Site are low and that steady state conditions prevail, leading to a strong diagenetic overprint of sedimentary Fe phases. In contrast the Contourite Terrace Site is characterized by high sedimentation rates and a lack of pronounced diagenetic overprint [3]. Reactive Fe phases are subject to reductive dissolution at the SMT. Nevertheless, significant amounts of reactive Fe phases are preserved below the SMT as evidenced by the presence of dissolved Fe in the methanic sediments, and are available for deep Fe reduction possibly through Fe-mediated anaerobic oxidation of methane [4]. In this study, δ<sup>56</sup>Fe signatures of reactive Fe phases in methanic sediments were determined for the first time. These data suggest significant microbial fractionation of Fe isotopes during deep Fe reduction at the Biogeochemistry Site, whereas at the Contourite Terrace Site the δ<sup>56</sup>Fe signatures do not indicate remarkable microbial Fe isotope fractionation. It is concluded that the applicability of δ<sup>56</sup>Fe signatures as tracer for microbial Fe reduction might be sensitive to the depositional regime, and thus may be limited in high sedimentation areas.</p><p>References:<br>Poulton, SW. and Canfield, DE., 2005. <em>Chemical Geology</em> 214: 209-221.<br>Henkel, S. et al., 2016. <em>Chemical Geology</em> 421: 93-102.<br>Riedinger, N. et al., 2005. <em>Geochimica et Cosmochimica Acta</em> 69: 4117-4126.<br>Riedinger, N. et al., 2014. <em>Geobiology</em> 12: 172-181.</p>

scholarly journals Distribution and sources of organic matter in surface sediments of the eastern continental margin of India

2013 ◽  
Vol 118 (4) ◽  
pp. 1484-1494 ◽  
Author(s):  
M. S. Krishna ◽  
S. A. Naidu ◽  
Ch. V. Subbaiah ◽  
V. V. S. S. Sarma ◽  
N. P. C. Reddy
Keyword(s):  
Organic Matter ◽  
Continental Margin ◽  
Surface Sediments

Littoral zones as sources of biodegradable dissolved organic carbon in lakes

2008 ◽  
Vol 65 (11) ◽  
pp. 2454-2460 ◽  
Author(s):  
E. G. Stets ◽  
J. B. Cotner
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Aquatic Macrophytes ◽  
Trophic Status ◽  
Surface Sediments ◽  
Decay Curve ◽  
Lake Area ◽  
Lake Trophic Status ◽  
Littoral Zones ◽  
Biodegradable Dissolved Organic Carbon

A survey of 12 lakes in Minnesota, USA, was conducted to examine the factors controlling variability in biodegradable dissolved organic carbon (BDOC) concentration. The principal question addressed was whether BDOC concentration was more strongly related to lake trophic status or morphometric parameters. BDOC concentration was determined by incubating filtered lake water for a period of 15 months and fitting an exponential decay curve to measured DOC concentrations. BDOC concentrations varied from 73 to 427 µmol C·L–1 and composed 15%–63% of the total DOC pool. There were no significant correlations between BDOC and measures of lake trophic status. Instead, BDOC was most closely associated with the percentage of lake area covered by littoral zone, suggesting a significant source of BDOC from aquatic macrophytes and lake surface sediments.

scholarly journals Evaluating impacts of bottom trawling and hypoxia on benthic communities at the local, habitat, and regional scale using a modelling approach

2019 ◽  
Vol 77 (1) ◽  
pp. 278-289 ◽  
Author(s):  
P D van Denderen ◽  
S G Bolam ◽  
R Friedland ◽  
J G Hiddink ◽  
K Norén ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Spatial Scales ◽  
Benthic Communities ◽  
Regional Scale ◽  
The Baltic Sea ◽  
Benthic Habitats ◽  
Bottom Trawling ◽  
Management Actions ◽  
The Baltic ◽  
Local Habitat

Abstract Bottom trawling disturbance and hypoxia are affecting marine benthic habitats worldwide. We present an approach to predict their effects on benthic communities, and use the approach to estimate the state, the biomass relative to carrying capacity, of the Baltic Sea at the local, habitat, and regional scale. Responses to both pressures are expected to depend on the longevity of fauna, which is predicted from benthic data from 1558 locations. We find that communities in low-salinity regions mostly consist of short-lived species, which are, in our model, more resilient than those of the saline areas. The model predicts that in 14% of the Baltic Sea region benthic biomass is reduced by at least 50%, whereas an additional 8% of the region has reductions of 10–50%. The effects of hypoxia occur over larger spatial scales and lead to a low state of especially deep habitats. The approach is based on a simple characterization of the benthic community, which comes with high uncertainty, but allows for the identification of benthic habitats that are at greatest risk and prioritization of management actions at the regional scale. This information supports the development of sustainable approaches to manage impact of human activities on benthic ecosystems.

Global correlation of the radiolarian faunal change across the Triassic–Jurassic boundary

2005 ◽  
Vol 42 (5) ◽  
pp. 777-790 ◽  
Author(s):  
Elizabeth S Carter ◽  
Rie S Hori
Keyword(s):  
Global Changes ◽  
Sedimentation Rates ◽  
Sedimentary Environments ◽  
Faunal Change ◽  
Queen Charlotte Islands ◽  
Global Correlation ◽  
Compensation Depth ◽  
Low Diversity ◽  
Upper Slope ◽  
Carbonate Compensation Depth

Precise comparison of the change in radiolarian faunas 3.5 m above a U–Pb zircon dated 199.6 ± 0.3 Ma tuff and approximately coincident with a negative δ13C anomaly in the Queen Charlotte Islands, B.C. (Canada) with Inuyama (Japan) sequences indicates that major global changes occurred across the Triassic–Jurassic (T–J) boundary. Nearly 20 genera and over 130 Rhaetian species disappeared at the end of the Triassic. The index genera Betraccium and Risella disappear and the final appearance of Globolaxtorum tozeri, Livarella valida, and Pseudohagiastrum giganteum sp. nov. are also diagnostic for the end of the Triassic. The low-diversity Hettangian survival fauna immediately above the boundary is composed mainly of small, primitive spumellarians with spongy or irregularly latticed meshwork and rod-like spines, and new genera Charlottea, Udalia, and Parahsuum s.l. first appear in the lowest Hettangian in both localities. Irrespective of different sedimentation rates and sedimentary environments, such as shelf to upper slope (Queen Charlotte Islands) and deep sea below carbonate compensation depth (CCD; Inuyama), radiolarians show a similar turnover pattern at the T–J boundary.

Sign in / Sign up

Export Citation Format

Share Document