Geographic variation in fitness‐related traits of the bladderwrack Fucus vesiculosus along the Baltic Sea‐North Sea salinity gradient

Abstract

In the course of the ongoing global intensification and diversification of human pressures, the study of variation patterns of biological traits along environmental gradients can provide relevant information on the performance of species under shifting conditions. The pronounced salinity gradient, co‐occurrence of multiple stressors, and accelerated rates of change make the Baltic Sea and its transition to North Sea a suitable region for this type of study. Focusing on the bladderwrack Fucus vesiculosus, one of the main foundation species on hard‐bottoms of the Baltic Sea, we analyzed the phenotypic variation among populations occurring along 2,000 km of coasts subjected to salinities from 4 to >30 and a variety of other stressors. Morphological and biochemical traits, including palatability for grazers, were recorded at 20 stations along the Baltic Sea and four stations in the North Sea. We evaluated in a common modeling framework the relative contribution of multiple environmental drivers to the observed trait patterns. Salinity was the main and, in some cases, the only environmental driver of the geographic trait variation in F. vesiculosus. The decrease in salinity from North Sea to Baltic Sea stations was accompanied by a decline in thallus size, photosynthetic pigments, and energy storage compounds, and affected the interaction of the alga with herbivores and epibiota. For some traits, drivers that vary locally such as wave exposure, light availability or nutrient enrichment were also important. The strong genetic population structure in this macroalgae might play a role in the generation and maintenance of phenotypic patterns across geographic scales. In light of our results, the desalination process projected for the Baltic Sea could have detrimental impacts on F. vesiculosus in areas close to its tolerance limit, affecting ecosystem functions such as habitat formation, primary production, and food supply.

Pulsed pressure: Fluctuating impacts of multifactorial environmental change on a temperate macroalgal community

“…Grazing pressure on particular macroalgal species may have changed not only due to the general decrease in mesograzer numbers but also to the restructuring of the mesograzer community, since the different consumer species differ with regard to their feeding preferences. Such preferences may (Nejrup et al 2012) or may not (Barboza et al 2019) differ among populations. The Kiel Bight population of F. vesiculosus is preferred over co-occurring A. vermiculophylla by the isopod I. balthica (Weinberger et al 2008), while A. vermiculophylla seems to be the preferred feed of the snail Littorina littorea relative to F. vesiculosus and F. serratus (C. Bommarito, GEOMAR, pers.…”

“…are among the most diverse and ecologically valuable (Kautsky et al 1992). These communities are exposed to increasing environmental stress in the course of global change (Werner et al 2016; Barboza et al 2019), as are many productive and diverse macroalgae‐based communities worldwide (Koch et al 2013; Wahl et al 2015b).…”

“…The broad tolerance range with regard to most physicochemical water conditions allowed these species to persist in the extreme and highly fluctuating environmental conditions of this marginal sea (Pansch et al 2014; Paalme et al 2019), but with decreasing performance rates when environmental parameters lie below or above their optima (Wahl et al 2020; Vajedsamiei et al 2021). For Fucus vesiculosus , and most other organisms interacting with it, the physiological optima are found (with considerable variation) in a temperature range between 10°C and 20°C, a salinity range between 20 and 33, a pH range between 7.5 and 9, and an oxygen range between 6 and 10 mg L −1 (Barboza et al 2019; Wahl et al 2020) (more information on species‐specific requirements are presented in Supporting Information Table S1).…”

How Do Geological Structure and Biological Diversity Relate? Benthic Communities in Boulder Fields of the Southwestern Baltic Sea

“…In the specific case of the Baltic Sea, strong environmental gradients further exacerbate the definition of reference values. For example, Barboza et al (2019) showed how fitness-related traits of the habitat-forming macroalga Fucus vesiculosus vary in response to the prevailing salinity gradient as well as other local environmental drivers (e.g., loads of nutrients), potentially affecting the functioning of associated communities. Thus, in hard-bottom habitats of the Baltic Sea, the analysis of the main processes shaping the structure of communities and functioning is especially important to disentangle natural drivers of biodiversity from factors caused by human activities.…”

Gene regulatory response to hyposalinity in the brown seaweed Fucus vesiculosus

“…Furthermore, both Atlantic and Baltic Sea populations are locally adapted to salinity; a reciprocal transplant experiment in a common garden found that populations grew better in their local salinity compared to the foreign salinity (24 and 4 PSU, respectively [28];). Despite such adaptation the Baltic Sea salinity gradient remains as a major factor affecting size, morphology and chemical contents of F. vesiculosus [29].…”