Climate change can cause complex responses in Baltic Sea macroalgae: A systematic review

Abstract

Estuarine macroalgae are important primary producers in aquatic ecosystems, and often foundation species providing structurally complex habitat. Climate change alters many abiotic factors that affect their long-term persistence and distribution. Here, we review the existing scientific literature on the tolerance of key macroalgal species in the Baltic Sea, the world's largest brackish water body. Elevated temperature is expected to intensify coastal eutrophication, further promoting growth of opportunistic, filamentous species, especially green algae, which are often species associated with intensive filamentous algal blooms. Declining salinities will push the distributions of marine species towards south, which may alter the Baltic Sea community compositions towards a more limnic state. Together with increasing eutrophication trends this may cause losses in marine-originating foundation species such as Fucus, causing severe biodiversity impacts. Experimental results on ocean acidification effects on macroalgae are mixed, with only few studies conducted in the Baltic

Population growth correlates with increased fecundity in three-spined stickleback populations in a human-disturbed environment

“…Data are pooled means and 95% confidence intervals for sites and dates within periods Wootton 1995;Wootton and Fletcher 2009). An increase in fecundity during the last decades is possible, as the availability of food has increased at the spawning sites when eutrophication and climate change have promoted the growth of filamentous algae (Andersen et al 2017;Takolander et al 2017), as algae biomass correlates with the abundance of benthic prey Kraufvelin et al 2006;Salovius and Kraufvelin 2004). In addition, climate change could have prolonged the spawning season, while the rise in water temperature (BACC II Author Team 2015) could have increased the feeding rate of the stickleback (Lefebure et al 2014).…”

Season affects strength and direction of the interactive impacts of ocean warming and biotic stress in a coastal seaweed ecosystem

“…At the same time, it may benefit less from acidification (having CCM) or from nutrient enrichment than its epiphytes because it can accumulate storage products in replete periods (Kawamitsu and Boyer ; Lehvo et al ; Hemmi et al ). In contrast, both factors (plus warming) may indirectly affect Fucus by benefitting its fast‐growing competitors (filamentous benthic algae, epiphytes, phytoplankton) (Provost et al ; Takolander et al ). Depending on the temporal occurrence of these drivers, they may amplify or buffer each other's impact (Gunderson et al ; Rugiu et al ).…”

“…By now, significant progress toward more realistic assessments has been achieved in multifactorial (several drivers) and multivariate (several responses) long‐term mesocosm studies (Sommer ; Jokiel et al ; Nagelkerken and Connell ; Riebesell and Gattuso ; Boyd et al ). Several studies show the capacity of biotic interactions—or the shift of such—to modulate or even mask the direct impact at the organism level of global‐change‐driven abiotic environmental pressures, for instance, for parasite‐host interactions (e.g., Kirk et al ), pathogen‐host interaction (e.g., Kiesecker and Blaustein ; Campbell et al ), epibiont‐host interaction (e.g., Werner et al ; Takolander et al ), competition, and predation (e.g., Alsterberg et al ; Falkenberg et al ; Goldenberg et al ; Provost et al ). The amplification or buffering of environmental impacts by biotic interactions should be particularly pronounced where foundational, that is, habitat‐forming, species are involved (Doney et al ).…”

Tolerance to climate change of the clonally reproducing endemic Baltic seaweed, Fucus radicans: is phenotypic plasticity enough?

“…), photosynthetic activity (Russell , Takolander et al. ), and induced resistance to herbivory (Jormalainen and Ramsay , Haavisto et al. ).…”

“…This has been proposed as an example of the so-called plasticity-first scenario for the establishment of a population in marginal habitats ). Furthermore, Baltic Sea fucoids have been shown to be phenotypically plastic for a number of other traits, such as phlorotannin production (Koivikko 2008), morphology (Sideman andMathieson 1983, Scott et al 2001), photosynthetic activity (Russell 1987, Takolander et al 2017, and induced resistance to herbivory Ramsay 2009, Haavisto et al 2017). Together, this indicates that plasticity represents a major part of the adaptive response of these algae to the highly variable littoral environment.…”