Meiobenthic Assemblages Research Articles

The specificity of meiobenthic community responses to different pollutants: Results from microcosm experiments

In preliminary microcosm experiments we have been able to demonstrate a clear differential response of meiobenthic assemblages to zinc, copper and cadmium contamination. Sediment and natural meiobenthic communities were collected from two estuaries, the Lynher (mud with a high organic content) and Exe (sand with a low organic content). The sediments were dosed separately with zinc, copper and cadmium at three different dose levels. The meiobenthic community structure from both sites was unaffected by cadmium at any of the dose levels. The communities in the zinc and copper treatments were significantly different (ANOSIM p < 0.05) from each other and from the controls (and cadmium treatments). Although the differential response occurred in both sediment types, its intensity was greater in the sand than the mud. The Exe sand communities were much more strongly affected by the contaminants, even at the lowest dose, copper having a more severe effect than zinc. The Lynher mud meiobenthos was most strongly affected by the zinc treatment and there was a graded response to both zinc and copper with significant differences in the communities at different doses (ANOSIM p < 0.05). These differences between sediments could be due to the binding of metals onto organic material, thus reducing their availability to the fauna.

Distribution of meiobenthic copepods from various habitats in Pauatahanui Inlet, New Zealand

Abstract The composition of meiobenthic copepod assemblages at two locations in Pauatahanui Inlet was determined for different substrata. In Ration Creek the density of copepods tended to increase from the creekside (which is covered with sea rush), to the bare mud of the creek bed. Brianola sp., though abundant, was restricted to the creek bed. On Mana Bank, which is an intertidal fine silty sand bank partially covered with eelgrass, Zostera capricorni, and the green alga Enteromorpha spp., there was little resemblance between the copepod assemblages at seven sites. The sediments of Mana Bank can apparently support a variety of copepod assemblages as a result of the increased spatial heterogeneity caused by vegetation and tidal exposure.

Effects of the deposit-feeding benthic bivalve Macoma balthica on meiobenthos.

To evaluate the effects of a deposit-feeding bivalve on meiobenthic assemblage structure in muddy habitats, a laboratory experiment was performed at the Askö Laboratory in the northwestern Baltic proper. Microcosms, surface area 104 cm2, containing a c. 7-cm thick layer of sieved (0.5 mm) sublittoral mud were established in June 1990. Two months later the tellinid bivalve Macoma balthica was added in quantities varying from 0 to 40 individuals per microcosm. After 5 months the effects of the bivalves on the meiofauna were surprisingly small. The density of harpacticoid copepods was lowest (P <0.05) in microcosms containing a high density of M. balthica. It is suggested that competition for food resources was responsible for this pattern. For all other meiofaunal groups, including nematodes which were the most abundant taxon (99%), no significant differences (P>0.05) were observed among treatments. The assemblage structure of the nematodes was similar between treatments. The vertical distribution of both major taxa and nematode species appeared to be unaffected by the presence of the bivalve.

Distribustion of the macro- and meiobenthic assemblages in the littoral soft-bottoms of the Gulf of Aqaba (Jordan)

Distribustion of the macro- and meiobenthic assemblages in the littoral soft-bottoms of the Gulf of Aqaba (Jordan)

The effect of crude oil on the colonization of meiofauna into salt marsh sediments

The effect of an oil spill on estuarine meiofauna was examined in a controlled colonization experiment. Forty-five replicate azoic sediment chambers treated with 0,133 or 381 mg hydrocarbons: 100 g dry sediment of South Louisiana crude oil were each quantitatively sampled with three replicate cores for colonizing meiofauna. Chambers were sampled on days 2, 5, 10, 30 and 60 postplacement in a Louisiana Spartina alterniflora (Loisel) salt marsh. Polychaetes showed a delayed colonization and reduced densities in oiled relative to non-oiled sediments. Nematode numbers were significantly depressed in the high oil treatment but no delay in colonization was identified. Only one species of meiobenthic copepods, Enhydrosoma woodini, displayed a reaction to the presence of the oil but only in the top centimeter of sediment. This species showed significantly decreased densities due to the heavily oiled treatment throughout the study until day 60 when numbers in the heavily oiled chambers were significantly higher than those in the non-oiled chambers. Species diversity (H') was calculated on the meiobenthic copepod assemblage and showed that diversity in the high oil treatment was generally lower than that in other treatments through day 30. Fewer species colonized the heavily oiled chambers before day 30. Principle Components Ordination conducted on the copepod assemblage could not identify an oil effect separate from a chamber effect for copepod community structure.