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A central problem in relating disturbance to community structure lies in determining how community structure is affected by the size of disturbance events. In soft-bottom habitats, recovery rate and patterns of macrobenthic community are usually affected by the spatial scale of disturbance. Thus far, no studies have explicitly addressed these issues for meiobenthic copepods. To test the effects of the size of hypoxia/anoxia disturbance on the recovery of meiobenthic copepod communities in a vegetated (Ruppia cirrhosa) sediment, a field experiment was set up in Valle Smarlacca, a brackish lagoon on the northern Adriatic coast of Italy. Plots of three different sizes—small (40×40 cm), medium (80×80 cm) and large (160×160 cm)—were exposed to experimentally induced hypoxia/anoxia for 5 days. Control plots of 40×40 cm were added, for comparison with ambient abundance. Recolonisation and community recovery were then observed for 12 days, with samplings on days 0, 1, 3, 5, 7, 9 and 12. Sampling was designed to focus on the distance from source pools of colonists. The induced anoxia had a severe impact on the copepods, but the impact of the disturbance was independent of plot size. Copepod abundance increased linearly over time, and no differences in recolonisation rate among the differently sized plots were observed. Recolonisation comprised two phases: until day 3, abundances were low and very similar in all plot sizes; from day 5 onwards, abundances of the dominant species (which were the same in control and disturbed plots) increased, and a more diversified pattern among disturbance sizes was observed. Multivariate analyses showed a gradual response of community structure to disturbance size: copepod assemblages in small plots attained the same structure of the control plots at day 5, while for larger-sized plots this occurred later and was observed on the following sampling date. However, clear differences among the three disturbance sizes were never detected. Variability in community structure seemed to respond more to the overall impact of disturbance than to the size of the disturbed area. In the seagrass meadows of the Valle Smarlacca, several factors seem to influence the structural organisation of meiobenthic copepod communities during recolonisation processes. Among others, the recovery of the vegetated habitat to suitable conditions seems to play a much more relevant role than the size of the disturbed patches.

Offshore drilling raises the issue of disposal of platforms at the end of their productive cycle and re-use as artificial reefs has been proposed. The wreck of the "Paguro" drilling platform, which sank in the northern Adriatic Sea in 1965, offers the opportunity to study the performance of offshore structures as artificial reefs in a region where this solution has not been explored before. We provide a description of the macrobenthic assemblages present at the wreck at different sites and at different depths, based on destructive and photographic sampling. Results show that the wreck has been colonized by a rich and diversified fauna. Primary space has been dominated by mussels and oysters, which provide suitable habitats for a variety of benthic invertebrates. Assemblages vary among sites, species richness is greatest at those sites facing prevailing currents. Distribution patterns vary vertically, evenness (Hill's N10) decreasing significantly with depth. It is argued that the results contribute to the background knowledge required in rigs-to-reefs programmes. © 2002 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved.

Sandy shores on the West coast of the North Adriatic Sea are extensively protected by different types of defence structures to prevent coastal erosion. Coastal defence schemes modify the hydrodynamic regime, the sediment structure and composition thus affecting the benthic assemblages. This study examines the effectiveness in detecting changes in soft bottom assemblages caused by coastal defence structures by using different levels of taxonomic resolution, polychaetes and/or bivalves as surrogates and different data transformations. A synoptic analyses of three datasets of subtidal benthic macrofauna used in studies aimed at assessing the impact of breakwaters along the North Adriatic coast has been done. Analyses of similarities and correlations between distance matrices were done using matrices with different levels of taxonomic resolution, and with polychaetes or bivalves data alone. Lentidium mediterraneum was the most abundant species in all datasets. Its abundance was not consistently related to the presence of defence structures. Moreover, distribution patterns of L. mediterraneum were masking the structure of the whole macrofaunal assemblages. Removal of L. mediterraneum from the datasets allowed the detection of changes in benthic assemblages due to coastal defences. Analyses on different levels of taxonomic resolution showed that the level of family maintained sufficient information to detect the impacts of coastal defence structures on benthic assemblages. Moreover, the outcomes depended on the transformation used. Patterns of distribution of bivalves, used as surrogates, showed low correlations with the patterns of the total macrofaunal species assemblages. Patterns of polychaetes, if identified to the species or genus level showed higher correlations with the whole dataset. However, the identification of polychaetes to species and genus level is as costly as the identification of all macrobenthic taxa at family level. This study provided additional evidences that taxonomic sufficiency is a useful tool in environmental monitoring, also in investigations on the impacts of coastal defence structures on subtidal macrofauna. The use of coarser taxonomic level, being time-efficient, would allow improving sampling designs of monitoring programs by increasing replication in space and time and by allowing long term monitoring studies.