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Primary production hotspots in the marine environment occur where the combination of light, turbulence, temperature and nutrients makes the proliferation of phytoplankton possible. Satellite-derived surface chlorophyll-a distributions indicate that these conditions are frequently associated with sharp water mass transitions named ''marine fronts''. Given the link between primary production, consumers and ecosystem functions, marine fronts could play a key role in the production of ecosystem services (ES). Using the shelf break front in the Argentine Sea as a study case, we show that the high primary production found in the front is the main ecological feature that supports the production of tangible (fisheries) and intangible (recreation, regulation of atmospheric gases) marine ES and the reason why the provision of ES in the Argentine Sea concentrates there. This information provides support to satellite chlorophyll as a good indicator of multiple marine ES. We suggest that marine fronts could be considered as marine ES hot spots.

Although age-specific habitat use has received much attention in recent years, the mechanisms that underlie ecological separation are not well known. This study examined the age-specific feeding site selection and its ecological mechanism in free-ranging Rock doves (Columba livia; referred to as pigeons). The distribution of age-classes at the feeding sites adjusted to a partially truncated distribution as follows: adults were consistently found more often than expected in the most rewarding feeding site, while juveniles were more often found in suboptimal sites. A removal experiment was conducted to determine whether competition accounted for the niche segregation between juvenile and adult pigeons. The reduction in intraspecific competition following removal was accompanied by an increased use of the preferred feeding site by juveniles. However, when the population recovered its initial size through immigration, juveniles were once again more frequently found in the suboptimal site. The proportion of juveniles feeding in each site was related to the total number of birds present; the higher the total number of birds, the higher the percentage of juveniles feeding in the less preferred site. These results support the idea that segregation between age-classes is due to competition by which adults displace juveniles from the richer foraging sites.

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