THE ROLE OF HABITAT COUPLING BY ZOOPLANKTON DRIVING POPULATION DYNAMICS AND STABILITY IN SHALLOW LAKES

Studies of population stability in shallow lakes are yet to explain how fishless ponds, with high algae productivity, can have stable zooplankton-algae populations throughout the year. These studies have traditionally overlooked the role of benthic-pelagic coupling, a phenomenon that has noticeable effects on population stability in aquatic environments. We analyzed a simple model to show that benthic-pelagic habitat coupling can explain discrepancies between the behavior of classical predator-prey models and the patterns observed in natural aquatic systems. We used a Lotka-Volterra type model of zooplankton and algae, explicitly modeled as phytoplankton and periphyton. Zooplankton could eat in both algal compartments, presenting a multi-chain omnivore configuration, whereas phytoplankton and periphyton engage in exploitative competition as system support capacity increases. We also modeled the algal exchange among compartments. Our model results show that (1) zooplankton—algae systems tend to be stable up to high nutrient values at intermediate degrees of omnivory, that (2) algae exchange among compartments may dampen stability and that (3) exploratory competition between phytoplankton and the periphyton can also decrease stability. The model results are supported by empirical results available in the literature. Despite the limitations of the modeling approach, our results emphasize the role of habitat coupling and contribute to deepening the understanding of the processes and mechanisms capable of promoting the stability of population dynamics in shallow lakes

Salvador e os sentidos: estratégias de comunicação na web para a construção da marca-cidade

En este artículo analizamos el fenómeno de la marca-lugar en la web. Para ello, examinamos dos videos de propaganda elaborados por el Ayuntamiento de la ciudad de Salvador de Bahía, como una estrategia para atraer a los turistas. En este estudio, buscamos identificar los atributos y valores de la “marca-lugar” de la ciudad de Salvador por intermedio de sus estrategias de comunicación y marketing elaboradas por el órgano de turismo municipal llamado Saltur, en el ambiente propuesto por las redes sociales online, en particular su canal de YouTube.In this article we analyze the phenomenon of place brand in the web environment. Therefore, we present the analysis of two promotional videos developed by Salvador’s town hall, as a strategy to attract tourists. In this study, we identify the attributes and values of Salvador’s place brand through its communication and marketing strategies elaborated by the municipal tourism organ, entitled Saltur, in the environment proposed by online social networks, in particular its Youtube channel.Neste artigo analisamos o fenômeno da marca-lugar no ambiente da web. Para tanto, trazemos a análise de dois vídeos promocionais elaborados pela Prefeitura da cidade de Salvador como estratégia para atração de turistas. Neste estudo, buscamos identificar os atributos e valores da “marca-lugar”, no referido município, por intermédio das estratégias de comunicação e marketing elaboradas pelo órgão de turismo municipal, intitulado Saltur, no ambiente proposto pelas redes sociais on-line, em particular em seu canal do YouTube

PRECIPITATION DEFICITS AND HIGH TEMPERATURE INCREASE LEAF LITTERFALL IN OPEN RESTINGA VEGETATION, IN SOUTHERN BRAZIL

Climate is an important driver of litterfall along different ecosystems. However, little is known about how climate affects litter production in plant communities of Restinga. The aim of this study is to characterize the temporal variation in leaf litter production in an Open Clusia Formation in Restinga de Jurubatiba National Park, from 2001 to 2018, and assess how local variability in litter production reflects the local climatic conditions and its variability. We tested the hypothesis that monthly leaf litterfall increases in dry months and in drier and warmer than average months; we also evaluated if annual leaf litterfall increases in wetter and warmer years following leaf production patterns, that increases in these conditions. We found that litterfall peaks in the drier months. This pattern is consistent for many tropical ecosystems, even evergreen ecosystems, and may have evolved as a strategy that result in reduced water stress by plants, during drier and warmer periods, or may simply be a stress symptom. However, we also found that decreases in monthly rainfall and increases in monthly ∆Temperature (temperature observed minus estimated based on 1970-2000 interval) stimulate leaf litter production. Hot and warmer than average years also seem to stimulate leaf litterfall. It suggests that annual leaf litterfall and leaf production are less affected by precipitation regimes than variations in temperature (or radiation, which is directly related to temperature). It may result from the fact that Clusia hilariana, the dominant species in this ecosystem which accounts to 80 % of leaf litterfall, is a CAM photosynthesis species, a characteristic commonly associated with avoidance of water stress by plants. Although leaf litterfall seems to be predominantly driven by climate at annual scale, only 15 % of its variation was associated to climate at seasonal scale, suggesting that local factors control litterfall at lower temporal scales in Open Clusia Formation

LEAF LITTER WITH CONTRASTING CHEMICAL TRAITS AND DECOMPOSITION PROMOTE SIMILAR BENTHIC MACROINVERTEBRATES COMMUNITIES

In aquatic ecosystems, allochthonous inputs of leaf litter are common substrates for the invertebrates communities. The quality and physical structure of these substrates are expected to strongly determine benthic invertebrates structure and functioning. Therefore, we carried out an experiment to evaluate the association between these organisms and the chemical traits of leaf litter from 16 restinga plant species in Jurubatiba lagoon, a coastal aquatic ecosystem at Restinga de Jurubatiba National Park. After 123 days, litter mass loss varied from 14 - 30%, indicating that decomposition was in the initial stage for most species. Litter converged to have a similar nutritional quality after this time submerged. Initial K concentration positively affected, whereas initial lignin and C concentration negatively affected species richness and diversity. It indicates that nutrients attract whereas structural compounds limit benthic species colonization. Chemical compounds such as C, nutrients (N, P, K and Na), lignin and cellulose tended to be positively associated with the dominant taxa (Chironominae n.i. and Heleobia australis) and functional feeding groups (scrapers and collector-gatherers). However, no significant associations were detected by the redundancy analyses. We may conclude that litter quality affect benthic structure, but not community composition nor FFG distribution at Jurubatiba lagoon. The benthic composition and FFG may be randomly distributed among litter substrates or may be better explained by some other litter aspect(s) different from those considered in this study. Future studies may also consider the temporal dynamic of litter colonization to better elucidate the relationship between litter traits and invertebrate community

Latitude dictates plant diversity effects on instream decomposition

Running waters contribute substantially to global carbon fluxes through decomposition of terrestrial plant litter by aquatic microorganisms and detritivores. Diversity of this litter may influence instream decomposition globally in ways that are not yet understood. We investigated latitudinal differences in decomposition of litter mixtures of low and high functional diversity in 40 streams on 6 continents and spanning 113 degrees of latitude. Despite important variability in our dataset, we found latitudinal differences in the effect of litter functional diversity on decomposition, which we explained as evolutionary adaptations of litter-consuming detritivores to resource availability. Specifically, a balanced diet effect appears to operate at lower latitudes versus a resource concentration effect at higher latitudes. The latitudinal pattern indicates that loss of plant functional diversity will have different consequences on carbon fluxes across the globe, with greater repercussions likely at low latitudes