Browsing by Author "Almeida Saa, Antonella C."
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- Multi-level phenotypic plasticity and the persistence of seagrasses along environmental gradients in a subtropical lagoonPublication . Bercovich, Manuel Vivanco; Schubert, Nadine; Almeida Saa, Antonella C.; Silva, Joao; Horta, Paulo A.As seagrasses decline worldwide, determining their phenotypic variability in response to human altered environmental factors becomes important to better understand their acclimation strategies. Many studies have reported seagrass responses to environmental gradients of single parameters, using either single or multiple metrics. However, studies of species' phenotypic variations along environmental gradients that include several environmental factors are rather scarce. In this study, we evaluated and compared the responses of Halodule wrightii and Ruppia maritima at different organizational levels (meadow/shoot, leaf and biochemical level) to key environmental factors, such as urbanization, light availability, salinity and sediment characteristics in a subtropical Brazilian coastal lagoon. Both species tolerated the variable environmental conditions across the lagoon, but showed species-specific differences in the adjustments at certain organizational levels. Halodule wrightii, an opportunistic species, expressed phenotypic responses mostly at the meadows/shoot and biochemical level, while the colonizer R. maritima exhibited phenotypic variability mostly constrained to the biochemical level. Also, determinations on a few selected meadows showed species-specific photosynthetic responses to environmental conditions. These differences might be related to the species' life history, with R. maritima performing adjustments at organizational levels with a fast response time, while the longer life span of H. wrightii makes also investments in modifications at the shoot and meadow level useful. Thus, this study demonstrates differences in seagrass acclimation strategies in response to environmental variability and, as a first study in this region, it also provides useful baseline data that will allow detecting potential changes and/or deterioration of the habitat.
- Unraveling interactions: do temperature and competition with native species affect the performance of the non-indigenous sun coral Tubastraea coccinea?Publication . Almeida Saa, Antonella C.; Crivellaro, Marcelo S.; Winter, Bruna B.; Pereira, Grazyelle R.; Bercovich, Manuel Vivanco; Horta, Paulo A.; Bastos, Eduardo O.; Schubert, NadineThe impact of invasive species has been increasing in recent decades due to globalization, threatening marine biodiversity. Tubastraea spp. (sun corals) have been spreading worldwide, showing rapid increases in abundance and/or spatial occupancy and adverse effects on recipient native ecosystems. In Brazil, they have become major invaders, extending discontinuously for more than 3000 km along the coast. Despite increased research efforts on sun coral ecology/biology over the last decade, information about the species' environmental tolerance and interactions with native species is still scarce. In this context, temperature may be an important driver, as it affects species interactions, primarily through its influence on organismal physiology. Thus, in the present study we assessed the effects of temperature in the invasive T. coccinea and the native zoanthid Palythoa caribaeorum, as well as on their interactions, via a 3-week mesocosm experiment, exposing the species (individually and grafted together) to a temperature range of 16-31 degrees C. This was accompanied by measuring key physiological traits (metabolism, growth, feeding rates and competitive behavior) that underlie species performance, and hence, competitive strength. The results showed that at Arvoredo Island, Brazil, currently the southern distribution limit of both species, (1) T. coccinea exhibited limited capacity to adjust to sudden temperature changes, (2) T. coccinea's physical attacks did not affect P. caribaeorum, but induced increased metabolic costs in the former, while triggering increased growth in the latter, leading to eventual overgrowth of the sun coral and (3) that temperature interacted synergistically with the presence of the competitor in both species under high-temperature stress. These findings suggest that T. coccinea's successful invasion is mainly associated with r-selected life-history traits, rather than competitive strength or a high plasticity to temperature changes, and thus, communities with specific native competitors and/or a variable thermal regime may be more resistant to sun coral invasion.