Defining the role of floating periphyton mats in shaping food-web dynamics in the Florida Everglades

Expansive periphyton mats are a striking characteristic of the Florida Everglades. Floating periphyton mats are home to a diverse macroinvertebrate community dominated by chironomid and ceratopogonid larvae and amphipods that use the mat as both a food resource and refuge from predation. While this periphyton complex functions as a self-organizing system, it also serves as a base for trophic interactions with larger organisms. The purpose of my research was to quantify variation in the macroinvertebrate community inhabiting floating periphyton mats, describe the role of mats in shaping food-web dynamics, and describe how these trophic interactions change with eutrophication. ^ I characterized the macroinvertebrate community inhabiting periphyton through a wet-season by describing spatial variation on scales from 0.2 m to 3 km. Floating periphyton mats contained a diverse macroinvertebrate community, with greater taxonomic richness and higher densities of many taxa than adjacent microhabitats. Macroinvertebrate density increased through the wet season as periphyton mats developed. While some variation was noted among sites, spatial patterns were not observed on smaller scales. I also sampled ten sites representing gradients of hydroperiod and nutrient (P) levels. The density of macroinvertebrates inhabiting periphyton mats increased with increasing P availability; however, short-hydroperiod P-enriched sites had the highest macroinvertebrate density. This pattern suggests a synergistic interaction of top-down and bottom-up effects. In contrast, macroinvertebrate density was lower in benthic floc, where it was negatively correlated with hydroperiod. ^ I used two types of mesocosms (field cages and tanks) to manipulate large consumers (fish and grass shrimp) with inclusion/exclusion cages over an experimental P gradient. In most cases, periphyton mats served as an effective predation refuge. Macroinvertebrates were consumed more frequently in P-enriched treatments, where mats were also heavily grazed. Macroinvertebrate densities decreased with increasing P in benthic floc, but increased with enrichment in periphyton mats until levels were reached that caused disassociation of the mat. ^ This research documents several indirect trophic interactions that can occur in complex habitats, and emphasizes the need to characterize dynamics of all microhabitats to fully describe the dynamics of an ecosystem. ^

Landscape shaping the economy of small coastal villages

Some years ago visitors and natives had a different way of enjoying the landscape of the coastal villages located in Santa Elena Province, in Ecuador. Nowadays natives of those towns are concerned about the emergent tourist industry, which is not just offering lodging but also it is increasing the construction of vacation homes or second homes. This development is showing notorious social and spatial changes in those coastal towns. Since 80's, the real-estate investments in vacation homes have not stopped. In addition, it has been increasing year in year out, to the north of the Province. Nowadays there are not just homes but also luxury complex of buildings attracting more and more seasonal tourists. This real estate growing has been constantly changing the landscape and shaping the economy of those towns. The authorities in this province are aware of those effects citing in the Province's Master Plan of Development the lack of land use policies. This study aims to describe the socioeconomic activity of coastal villages located in Santa Elena Province, which - during many years - have a resource-based economy: agriculture and fishing economy; but during this last years they have been trying to switch it to tourism. The analysis of spatial changes of the landscape and its effects as a consequence of the land use is another goal of this work. Finally, this study describes the quest of new natural tourist attractions that villagers and stakeholders have taken recently. Key words: Nature and society, sociospatial, rural landscape, coastal landscape, tourism.