Decadal losses of canopy-forming algae along the warm temperate coastline of Brazil.

The loss of canopy-forming seaweeds from urbanized coasts has intensified in response to warming seas and non-climatic pressures such as population growth and declining water quality. Surprisingly, there has been little information on the extent of historical losses in the South-western Atlantic, which limits our ability to place this large marine ecosystem in a global context. Here, we use meta-analysis to examine long-term (1969-2017) changes to the cover and biomass of Sargassum spp. and structurally simple algal turfs along more than 1,000 kilometres of Brazil's warm temperate coastline. Analysis revealed major declines in canopy cover that were independent of season (i.e., displaying similar trends for both summer and winter) but varied with coastal environmental setting, whereby sheltered bays experienced greater losses than coastal locations. On average, covers of Sargassum spp. declined by 2.6% per year, to show overall losses of 52% since records began (ranging from 20% to 89%). This contrasted with increases in the cover of filamentous turfs (24% over the last 27 years) which are known to proliferate along human-impacted coasts. To test the relative influence of climatic versus non-climatic factors as drivers of this apparent canopy-to-turf shift, we examined how well regional warming trends (decadal changes to sea surface temperature) and local proxies of coastal urbanization (population density, thermal pollution, turbidity and nutrient inputs) were able to predict the changes in seaweed communities. Our results revealed that the most pronounced canopy losses over the past 50 years were at sites exhibiting the greatest degree of coastal warming, the highest population growth and those located in semi-enclosed sheltered bays. These findings contribute knowledge on the drivers of canopy loss in the South-western Atlantic and join with global efforts to understand and mitigate declines of marine keystone species.

Environmental drivers of rhodolith beds and epiphytes community along the South Western Atlantic coast.

Environmental conditions shape the occurrence and abundance of habitat-building organisms at global scales. Rhodolith beds structure important hard substrate habitats for a large number of marine benthic organisms. These organisms can benefit local biodiversity levels, but also compete with rhodoliths for essential resources. Therefore, understanding the factors shaping the distribution of rhodoliths and their associated communities along entire distributional ranges is of much relevance for conservational biology, particularly in the scope of future environmental changes. Here we predict suitable habitat areas and identify the main environmental drivers of rhodoliths' variability and of associated epiphytes along a large-scale latitudinal gradient. Occurrence and abundance data were collected throughout the South-western Atlantic coast (SWA) and modelled against high resolution environmental predictors extracted from Bio-Oracle. The main drivers for rhodolith occurrence were light availability and temperature at the bottom of the ocean, while abundance was explained by nitrate, temperature and current velocity. Tropical regions showed the highest abundance of rhodoliths. No latitudinal pattern was detected in the variability of epiphytes abundance. However, significant differences were found between sampled sites regarding the composition of predominant taxa. The predictors influencing such differences were temperature and nitrate. The Tropical region is abundant in species with warm-water affinities, decreasing toward warm temperate region. The expressive occurrence of tropical species not referred before for warm temperate beds indicate a plausible tropicalization event.

The influence of environmental features in the content of mycosporine-like amino acids in red marine algae along the Brazilian coast.

Mycosporine-like amino acids (MAA) are ultraviolet screen substances synthesized by marine algae. The physiological function of these substances is related to cellular protection against UV radiation and as a protective mechanism against oxidative stress. These substances can be found mainly in the ocean, among red seaweeds. Its concentration in organisms has been related to ultraviolet radiation and availability of inorganic nitrogen in the environment. We start our study of MAA content in different species to understand if environmental conditions influence the concentration of MAAs in red seaweeds. The Brazilian coast presents abiotic factors that interact to create different physical-chemical features in the environment. We collected 441 samples from 39 species of red seaweed easily found in the intertidal zone, in low tide, during the summer of 2015. The sampling encompassed a latitudinal gradient (3° S to 28°5' S) at 23 points along the coast. We quantified and identified the content of MAAs in species through the method of high performance liquid chromatography. We detected for the first time the occurrence of MAAs in certain species of red algae that have not been reported to contain MAAs before. We confirmed that some environmental factors influenced the content of MAAs. Enhanced MAA contents, for example, were found in environments with a basic pH, a high ultraviolet index, and high concentrations of phosphate and nitrate. Salinity, dissolved oxygen and variations of sea surface temperature also influenced, in a secondary way, MAA content in algae in their natural environments.

Evaluation of impacts of climate change and local stressors on the biotechnological potential of marine macroalgae: a brief theoretical discussion of likely scenarios

Climate change can be associated with variations in the frequency and intensity of extreme temperatures and precipitation events on the local and regional scales. Along coastal areas, flooding associated with increased occupation has seriously impacted products and services generated by marine life, in particular the biotechnological potential that macroalgae hold. Therefore, this paper analyzes the available information on the taxonomy, ecology and physiology of macroalgae and discusses the impacts of climate change and local stress on the biotechnological potential of Brazilian macroalgae. Based on data compiled from a series of floristic and ecological works, we note the disappearance in some Brazilian regions of major groups of biotechnological interest. In some cases, the introduction of exotic species has been documented, as well as expansion of the distribution range of economically important species. We also verify an increase in the similarities between the Brazilian phycogeographic provinces, although they still remain different. It is possible that these changes have resulted from the warming of South Atlantic water, as observed for its surface in southeastern Brazilian, mainly during the winter. However, unplanned urbanization of coastal areas can also produce similar biodiversity losses, which requires efforts to generate long-term temporal data on the composition, community structure and physiology of macroalgae.

The impact of coastal urbanization on the structure of phytobenthic communities in southern Brazil.

The anthropogenic pressures on coastal areas represent important factors affecting local, regional, and even global patterns of distribution and abundance of benthic organisms. This report undertakes a comparative analysis of the community structure of rocky shore intertidal phytobenthos in both pristine like environments (PLE) and urbanized environments (UBE) in southern Brazil, characterizing variations on different spatial scales. Multivariate analysis of variance indicated that the PLE is characterized by a larger number of taxa and an increased occurrence of Rhodophyta species in relation to UBE. In contrast, UBE were dominated by opportunistic algae, such as Cladophora and Ulva spp. Significance tests further indicated higher species richness and Shannon-Wiener diversity on the PLE in relation to UBE. Here we provide data showing the magnitude of seaweed biodiversity loss and discuss direct and indirect consequences of unplanned urbanization on these communities.