Two new genera and six new species of benthic amphipods from the soft sediments of the Perdido Fold Belt region, western Gulf of Mexico, are described. Morphological comparisons of the new species with description of their congeners resulted in the determination of one new genus and one new species of the family Melitidae as Dentimelita lecroyae gen. nov., sp. nov., one new genus and four new species of the family Pardaliscidae as Pardaliscella perdido sp. nov., Paraeperopeus longirostris gen. nov., sp. nov., Pardaliscoides ecosur sp. nov. and Tosilus cigomensis sp. nov., and one new species of the family Unciolidae as Neohela winfieldi sp. nov. The occurrence of the newly described amphipods in the Perdido Fold Belt region represented new geographic range extensions for the genera, including new records of Neohela in the Gulf of Mexico, Pardaliscella and Pardaliscoides in the western Atlantic and Tosilus in the Atlantic.

Exposed sandy beaches are widespread coastal habitats with temporal and spatial variability. O Rostro beach (Galicia, north-west Spain) was the most severely affected beach in the ‘Prestige’ oil spill (November 2002). Monitoring sampling was conducted to study macroinfaunal composition and structure after the oil spill episode. The purpose of this survey was to characterize macroinfaunal variations on the beach over a yearly scale (2003–2007) and determine the recovery period. These data are compared with the only available data collected before the spill (1995). Two zones where identified with different recovery trends: (1) supralittoral, occupied either by talitrid amphipods, oniscoidean isopods and insects; and (2) intertidal, where marine crustaceans prevailed. Beach morphodynamics partially buried the oil, which gradually reappeared and was dragged to the coast. Negative ecological effects were observed in the short term (six months after the 2002 spill) but macroinfauna apparently recovered in the following years (2004–2007), showing that macroinfaunal assemblages of this beach are resilient enough to recover after severe stress.

The interest in the knowledge of the ecology of soft-sediment communities is increasing due to the importance that these environments pose to ecologists and environmentalists. However, the ecology of Argentinean sandy beaches is almost unknown, in spite of being relatively common landscapes. In this work we describe and compare the macroinfaunal assemblages in the two largest sandy beaches within the Monte León National Park, the first marine-coastal park of Argentina. Macrobenthic samples were collected and environmental descriptions were performed by quantifying and comparing the organic matter content, grain size distribution and depth of the substratum available for macroinfaunal colonization. Results show that polychaetes and crustaceans are the dominant taxa and that the two beaches differ in the physicochemical characteristics, suggesting that a relation between the benthic fauna and physicochemical factors exists. Although they appeared similar at the landscape scale in preliminary visual surveys, the geomorphological differences between habitats are likely to drive strong differences in the structure of the macroinfaunal assemblages. The monitoring of visible landscape features is likely to undermine the efficiency of protection and managing strategies if not complemented by geomorphological and ecological surveys of less visible ecosystem variables.

Fixed-point and probabilistic sampling designs were compared to investigate which design best detected known contamination gradients in the marine ecosystem adjacent to McMurdo Station, Antarctica. The fixed-point sampling design included transects along historical contamination and physical disturbance gradients. The probabilistic sampling design used randomly selected hexagons spaced at 50 m intervals. In both designs, 15 stations were sampled over a small area (~1 km2) that extended from Winter Quarters Bay to Cape Armitage. Sediment quality triad components (sediment chemical contaminants, sediment toxicity, and a benthic index of biotic integrity) were measured to indicate chemical, toxicological, and biological effects. There were higher correlations between sediment quality triad components for the fixed-point sampling design than for the probabilistic design. The fixed-point design was better at detecting the intensity of alteration because disturbance of the marine ecosystem at McMurdo Station is localized within a small area. Based on these results, a limited fixed-point design with nine stations detected no significant change in macrofaunal community structure over a four year period from 2000–2004. However, the macrofaunal assemblages present in the contaminated portions of Winter Quarters Bay are indicative of a disturbed benthic community that has been subject to organic enrichment and toxic chemical exposure.

The macroinfauna at depths 30–115 m was sampled in March–April 1989, c. two months after an oil spill that resulted from the grounding of the Bahia Paraiso. Stations consisted of the oil-spill site and a comparable control location, and two historical sites previously sampled in 1971. The historical sites were located at two distinct points along a known continuum of increasing physical stability with depth, attributed to disturbances from glacial calving. Macroinfaunal assemblages at most stations were characterized by very high densities and numbers of taxa. There were no significant differences (P<0.05) between the oil-spill and control sites in numbers of individuals, species, or families; nor were there any major differences in dominant fauna or overall community composition. The absence of a detectable impact on the fauna is consistent with results of hydrocarbon analyses, which showed that subtidal sediments were nearly devoid of contamination emanating from the Bahia Paraiso. The assemblage at the shallower of the two historical sites, however, showed a substantial change over the 18-yr period between studies. This change consisted of a shift toward a more species-rich and abundant macroinfauna characteristic of the more physically stable parts of the harbour. This change may be related to the fact that the glacier face near this site has retreated c. 250 m over the last 20 yrs, resulting in less physical disturbance of the adjacent seafloor.