Abstract
AbstractAimTo understand spatial‐temporal changes (beta‐diversity) in coastal communities and their drivers in the context of climate change. Coastal ecosystems are extremely exposed and dynamic, where changes in seaweed assemblages have been associated with changing water temperatures. However, at local scale, the effects of changes in the upwelling events and related stressors seek further exploration.LocationGalicia rías, North West of the Iberian Peninsula.MethodsUsing data collected in 42 sampling localities in Galicia rias and over two time periods (1998 and 2014), we analysed changes in the seaweed community's composition through time and space. We calculated the temporal beta‐diversity index and spatial beta‐diversity as the pairwise composition differences between sampling localities. We use generalized dissimilarity models, to identify local environmental drivers of spatial and temporal beta‐diversity.ResultsWe found a significant change in seaweed communities of Galicia rias, between 1998 and 2014 (temporal beta‐diversity). They were mostly related to species loss rather than to species replacement. The dissimilarity among localities (spatial beta‐diversity) was significantly higher in 2014 than in 1998. Nitrate concentration was consistently predicted as the main driver of both temporal and spatial beta‐diversity patterns.Main conclusionsUnlike other studies in marine ecosystems, our results suggest that observed changes in the structure of perennial seaweed assemblages in Galicia Rias might lead to a local biotic heterogenization, indirectly linked to climate change through changes in nutrients availability and the upwelling intensity. Changes in Galicia seaweed communities call scientific attention to the importance of local stressors in climate change studies.
Highlights
Unprecedented climate changes are globally altering every ecosystem on Earth
Using data collected in 42 sampling localities over two time periods (1998 and 2014) (Piñeiro-Corbeira et al, 2016), we tested whether the observed decrease in species frequency was accompanied by changes in the community structure and, if so, whether they could be linked to sea surface temperature changes (Piñeiro-Corbeira et al, 2016)
Nitrate concentration is consistently predicted as the variable that best predicts the spatial beta-diversity, and our data show that the sites within the rias tend to have higher nutrient concentrations and those sites usually are less exposed to the waves
Summary
Unprecedented climate changes are globally altering every ecosystem on Earth. Climate fluctuations are pointed as important driving forces of complex and unanticipated changes in biodiversity (Burrows et al, 2014; Parmesan & Yohe, 2003). Using data collected in 42 sampling localities over two time periods (1998 and 2014) (Piñeiro-Corbeira et al, 2016), we tested whether the observed decrease in species frequency was accompanied by changes in the community structure (as temporal beta-diversity) and, if so, whether they could be linked to sea surface temperature changes (Piñeiro-Corbeira et al, 2016). In situ environmental variables were used to investigate the drivers of both temporal and spatial beta-diversity patterns in Galicia Rías (Figure S1) weekly water column recording of seawater temperature, and nitrate and phosphate concentrations. Changes in nitrate concentrations and water temperature from 1998 to 2014 were the major drivers of the observed patterns of FIGURE 2 Boxplots of species richness and spatial beta-diversity (Sorensen dissimilarity index) each year (1998 and 2014) for all seaweeds and with seaweeds grouped by thermal affinity. Geographic distance and phosphate concentration were the most important drivers of species loss among localities for all species and for species with warm affinity (Table 1, Figure S1, Figure S4)
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