Benthic Mesocosm Research Articles

Effects of biological disturbance on diversity and structure of meiobenthic nematode communities

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 174:233-246 (1998) - doi:10.3354/meps174233 Effects of biological disturbance on diversity and structure of meiobenthic nematode communities Melanie C. Austen*, Stephen Widdicombe, Nicoletta Villano-Pitacco Centre for Coastal and Marine Sciences, Plymouth Marine Laboratory, Prospect Place, West Hoe, Plymouth PL1 3DH, United Kingdom *E-mail: m.austen@pml.ac.uk ABSTRACT: Benthic mesocosm experiments have shown that subtidal macrofauna species with contrasting feeding behaviour and mobility can alter the structure of natural subtidal meiobenthic nematode assemblages. Test macrofauna species were the bivalves Nuculoma tenuis (subsurface-deposit feeder) and Abra alba (surface-deposit/suspension feeder) at 3 different densities and the heart urchin Brissopsis lyrifera (subsurface burrowing deposit feeder) at a single density. α and β nematode diversity were affected by disturbance of different intensities in the bivalve treatments in a way that is consistent with the intermediate disturbance hypothesis regardless of type of disturbance. These measures of community structure did not differentiate between contrasting types of disturbance. Multivariate community analysis indicated that the species response in the assemblage was more sensitive to the type of disturbance than the intensity of disturbance. Differential responses of the nematode species did not reflect their depth distribution in natural field sediment and the likely depth at which the test macrofauna species were active. Nor was the response simply a predator-prey interaction with certain species targeted by the predator; the interactions appear to be more complex. Our experimental results suggest that patches of sediment which are dominated by high abundances or biomass of one or a few species, a situation which is encountered in the field, are important in maintaining regional diversity. These patches will create a heterogeneous mosaic of communities with different diversities and different species compositions. KEY WORDS: Meiofauna · Nematode · Diversity · Community structure · Predation · Disturbance · Abra alba · Nuculoma tenuis · Brissopsis lyrifera Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 174. Publication date: November 26, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.

A benthic mesocosm facility for maintaining soft-bottom sediments

Closed-circulation, water jacket-insulated laboratory basins (benthic mesocosms) of 1 m 2 surface area preserved the abundance and species composition of the principal benthic macrofauna of the 350-m-deep Laurentian Trough for periods exceeding a year. Abundance of meiofauna, and bacterial numbers and activity were also sustained. Although the overlying water was permitted to equilibrate with the atmosphere, oxygen penetration depths in the sediment stabilized at about twice the thickness of the in situ aerobic layer, while whole-sediment respiration rates remained within the range observed for freshly obtained sediment cores. Build-up of metabolic by-products in the overlying water was controlled by bi-monthly replacement of a third of the bottom water. The study demonstrated that close observation of organism behaviour and biogeochemical processes within deep coastal sediments can be carried out in laboratory mesocosms.

Field experiments on the fate of lead and chromium in an intertidal benthic mesocosm, the Bremerhaven Caisson

The Bremerhaven Caisson, a benthic mesocosm enclosing a 13 m2 sediment area and 13 m3 trapped water column at high tide, was used for field experiments on the fate of lead and chromium at the isle of Norderney, Southern German Bight. The caisson, made from seawater resistant aluminium, settled on fine sand (mean grain size: 0.2 mm) at an experimental site with about 0.9-m tidal height and 4.5 h of water coverage. During 38 consecutive tides a constant amount of lead was administered to the inflowing water, resulting in a nominal concentration of 0.1 mg l-1 at high tide. A second caisson was taken for chromium using the same procedure. The compartments analysed (water, seston, sediment, and infauna) showed distinct differences for lead and chromium. The particle-reactive element Pb adsorbed by 50–70% onto seston particles, the soluble element Cr-VI by less than 2%. Only a moderate enrichment was measured in the sediment, about 3–4% of the total Pb and Cr added accumulated in the top 3 cm. The fauna attained much higher accumulation factors than the sediment. The lead uptake rates of 15 species and 2 taxa can be placed in order according to the feeding type: filter feeder > deposit feeder (surface) > opportunistic feeder (deposit feeder or predator) > deposit feeder (depth). Chromium was accumulated about 10 times lower than lead, the uptake seems to be more related to the systematic position of the animal (calcareous shell versus chitinous cuticle). In the total mass balance only 0.2% of the lead added and 0.02% of the chromium added were fixed by the fauna.