A soft-bottom sublittoral mesocosm by the Oslofjord: Description, performance and examples of application

Most marine benthic macrofaunal species are buried in the sediment but feed on the sediment surface. We measured benthic faunal activity on the sediment surface in 0.25 m 2 box-cores from a 75 m depth in a Swedish fjord. The techniques used were video numeric tracking and electronic intelligent sensors, where the activity pattern was continuously recorded. During a 4 h recording, 24% of the examined surface area showed infaunal activity. When phytodetritus was added to the same surfaces, the areas searched by the fauna almost doubled over the next 4 h. Thus, the main part of the sediment surface is most probably covered daily by infaunal activity, particularly when food is available. Arms of Amphiura filiformis and A. chiajei contributed to 40-80% of the total surface area covered by faunal activity, which was >15 times that of tentaculate feeding activity of Melinna cristata. Time frequency recordings showed that the response of the Amphiura species to food supply was strong during the first 25 min, followed by a decline, which probably was related to processing and storage of food in the sediment.

Section: Discussionmentioning

confidence: 99%

Marine benthic faunal activity patterns on a sediment surface assessed by video numerical tracking

Duchêne¹,

Rosenberg²

2001

“…The mesocosm used is a 5 × 7 m indoor, epoxy-resin-coated concrete basin in which a constant depth of 100 cm is maintained with a continuous flow of water pumped from 60 m depth from the Oslofjord. The system has been described in detail by Berge et al (1986).…”

Section: Methodsmentioning

confidence: 99%

Importance of bioturbators for biodiversity maintenance: indirect effects of fishing disturbance

Widdicombe¹,

Austen²,

Kendall³

et al. 2004

The relative impact on macrofaunal diversity of 7 naturally co-occurring bioturbators has been examined in a benthic mesocosm experiment. The bioturbators chosen were selected because of their potential vulnerability to the disturbances associated with demersal trawling. The experiment was conducted at the Solbergstrand mesocosm (Norwegian Institute for Water Research) using subtidal sediment collected from Bjørnehodebukta, a small sheltered bay in the Oslofjord. For 3 of the bioturbating species (Brissopsis lyrifera, Aphrodita aculeata and Amphiura chiajei) a positive, linear relationship was demonstrated between bioturbator abundance and measures of species richness (number of species and Margalef species richness). It was suggested that the presence of these bioturbating species increased oxygen penetration into the sediment, leading to an enhancement in the ability of benthic systems to process organic material. This had a beneficial effect on the associated fauna in terms of maintaining levels of diversity. For Nephtys caeca, highest species diversity was seen in the low abundance treatments. Predation by N. caeca on small polychaetes is proposed as a possible explanation of the lower diversity in high-density treatments. It is concluded that B. lyrifera, A. aculeata, A. chiajei and N. caeca are functionally similar with respect to setting the diversity of the associated macrobenthic community and may therefore fulfill the same role within the benthic ecosystem. The presence of Calocaris macandreae, Nuculana minuta and Astarte sulcata had no detectable effect on diversity. Trawling has been shown to reduce the abundance of bioturbating species, and the current study demonstrates important implications of this loss on the maintenance of diversity. In addition, the interactions between bioturbation, diversity and organic enrichment highlight the need for management of anthropogenic impacts within the coastal environment in a holistic way rather than by isolation.

“…The experiment was carried out in the soft bottom mesocosm of the NIVA Marine Research station at Solbergstrand, south of Drwbak, on the eastern shore of Oslofjord, Norway. The mesocosm has been described in detail by Berge et al (1986). The 4.9 X 7 m indoor, epoxy resin coated concrete basin used for this experiment had a water depth of 100 cm.…”

Section: Methodsmentioning

confidence: 99%

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

Austen¹,

Widdicombe²,

Villano-Pitacco³

1998

Benthic mesocosm experiments have shown that subtidal macrofauna species with contrasting feedlng 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-deposiWsuspension feeder) at 3 different densities and the heart urchin Brissopsis lyrifera (subsurface burrowing deposit feeder) at a single density. a and P 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 hlgh abundances or biomass of one or a few species, a situat~on 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