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Patterns of succession in Lau Basin hydrothermal vent communities determined with high-resolution imagery and in situ physico--chemical data collected over 4 yr and analyzed within a Geographic Information System show that Alviniconcha snails are a pioneering group, the snail Ifremeria nautilei is a mid-successional species, and the heat-intolerant mussel Bathymodiolus brevior dominates when venting declines. The associated fauna also changes as communities progress through the successional stages, and eventually non-vent--endemic deep-sea species appear when venting has mostly subsided. This is a unique example of primary succession in which the primary producers form symbiotic associations with mobile animals, resulting in successional patterns not observed in other systems. I. nautilei dominates newly formed substrates or venting sources where both I. nautilei and Alviniconcha spp. are already established (e.g., by migration), while Alviniconcha spp. seem to be better at colonizing newly active vents (e.g., by settlement) that are remote from colonized vents. Thus, on the scale of a 5--39 m² diffuse flow area or a single edifice, the mid-successional species dominates new substrates instead of the pioneering group. These communities are remarkably stable over long time periods relative to other hydrothermal vent regions. In addition to the sequential replacements of species as sites age and overa conditions change, Lau vent animals track changes in vent fluids and relocate themselves when local hydrothermal plumbing changes over small spatial scales. [ABSTRACT FROM AUTHOR]

A pattern of succession has been demonstrated at Gulf of Mexico cold seeps proceeding from a high-biomass endemic community dominated by grazers to a diverse community of endemic and nonendemic species in multiple trophic levels to a low-biomass community comprising primarily nonendemic predatory species. We test the hypothesis that these shifts in community structure are due to a decline in the availability and reliance on local chemosynthetic productivity. Isotopic signatures were measured in 134 individuals from 34 different species in three tubeworm aggregations in different stages of succession. The average stable isotope delta values of the fauna were more positive in the older aggregations, suggesting a decreased reliance on local chemosynthetic productivity. These trends were also apparent in the species that were present in all three aggregations and for the grazer trophic group as a whole. The proportion of biomass in the lower trophic levels declined in the older aggregation. Food webs were reconstructed on the basis of variable trophic shifts and included the error in stable isotope measurements. The majority of potential trophic links supported by carbon and nitrogen isotopes alone were rejected when sulfur stable isotope values were included. Food webs consisted of relatively few trophic links overall, with the most complex food web in the more diverse community of the middle aggregation. These results suggest that many of the species in the tubeworm aggregations are generalists, and these species may feed on prey outside the aggregation, especially in the older aggregation, where few trophic links could be detected. [ABSTRACT FROM AUTHOR]