Modeling the effects of abiotic and biotic factors on the depth distribution of Fucus vesiculosus in the Baltic Sea

Abstract

The conspicuous retreat of the key species Fucus vesiculosus from the deeper parts of its former distribution area in the Baltic Sea has triggered extensive research on the factors that control its growth. Based on recently obtained knowledge on a large number of potential drivers, we developed a numerical model incorporating effects of abiotic factors on the physiological functions of photosynthesis, respiration, and reproduction and the ecological processes of competition, grazing, and epibiosis. For all input combinations, the model delivers the monthly net growth rate near the bladder wrack's depth limit and the maximum depth of its vertical distribution. The use of data corresponding to conditions presently observed in the western Baltic Sea sets the year's maximum algal net growth rate in late spring and 2 minima in early spring and autumn. The depth limit of the wrack's distribution is set at ~9 m. Light and its absorption by phytoplankton represent by far the most important factors controlling the modeled net growth rate and depth penetration, with the role of epibiosis requiring further investigation. Lacking findings on population dynamics and biotic interactions restrict the generated model to an exploratory rather than a predictive tool. KEY WORDS: Depth limit · Benthic ecology · Eutrophication · Ecological modeling · Bladder wrack · Biotic interactions · Fucus physiology Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 463: [59][60][61][62][63][64][65][66][67][68][69][70][71][72] 2012 of its distribution during the second half of the last century (e.g. Kautsky et al. 1986, Vogt & Schramm 1991, Eriksson et al. 1998. Although partial recovery has been observed at some sites in recent years (Nilsson et al. 2004), the general pattern of restricted depth penetration of F. vesiculosus in the Baltic Sea seems to persist (Torn et al. 2006). Among other factors, such as direct habitat destruction or increased grazing due to overfishing of the mesograzers' predators, eutrophication is considered to play the most prominent role in this change (Kautsky et al. 1986, Eriksson et al. 1998, Torn et al. 2006. The ways in which high nutrient levels can hinder the propagation and growth of F. vesiculosus are manifold, the most commonly reported being increased water turbidity (Kautsky et al. 1986), increased sedimentation rates (Eriksson & Johansson 2003), increased grazing pressure (Kangas et al. 1982), direct inhibition of spore settlement and development (Bergström et al. 2003), increased epibiotic load (Wahl 1989), and increased competition with ephemeral algae and the blue mussel Mytilus edulis (Vogt & Schramm 1991).Considering all these possible effects of eutrophication on Fucus vesiculosus, one might be tempted to consider the question of its reduced depth penetration as answered. However, the fact that so many mechanisms and functional groups of organisms are involved, some of them, like epibionts, even having been credited with possibly positive eff...

Survival in low light: photosynthesis and growth of a red alga in relation to measured in situ irradiance

“…Although there are insufficient data to link this state change to anthropogenically driven changes in benthic photon flux alone (Alexandridis et al. ), such an effect is well‐documented in communities dominated by seagrasses (Onuf , Preen et al. , Longstaff and Dennison , Ralph et al.…”

“…In temperate rocky reef systems throughout the world, there has been a documented decline in the dominance of large fucoid and laminarian macroalgae, which is often accompanied by an alternate ecosystem state dominated by small, turf-forming rhodophyte species (Airoldi and Beck 2007). Although there are insufficient data to link this state change to anthropogenically driven changes in benthic photon flux alone (Alexandridis et al 2012), such an effect is well-documented in communities dominated by seagrasses (Onuf 1994, Preen et al 1995, Longstaff and Dennison 1999, Ralph et al 2006) and direct links between (natural) increases in turbidity and reductions in the productivity of benthic macroalgae (Smith and Jones 1971, Dunton 1990, Airoldi 2003, Anthony et al 2004) are well established. In light of the predicted increases in anthropogenic modification to coastal seas (Airoldi 2003, Harley et al 2006, Gorman et al 2009), the minimum light requirement for growth and survival of macroalgae near their maximum depth limit warrants further analysis.…”

Metagenomics unveils the attributes of the alginolytic guilds of sediments from four distant cold coastal environments

“…Despite this potential, algal biomass decomposition is a slow process at the sampling location in Potter Cove, where insufficient mechanical break‐down and low temperatures could be limiting the macroalgae degradation rate (Quartino et al ., ; Quartino et al ., ). The overall abundance of AL genes in sediments from the Baltic Sea was 0.66 ± 0.04 copies per single‐copy gene, suggesting a lesser prevalence of microorganisms with alginolytic potential in sediments of this brackish environment, possibly due to a lower biomass of brown algae (Alexandridis et al ., ; Supporting Information). Homologues of AL genes could remain undetected in this analysis if they are divergent from those used to define the Pfam domains.…”

Model simulation of seasonal growth of Fucus vesiculosus in its benthic community

“…Without separately describing the difference in uptakes between carbon and nutrients, the application of such models to a wide range of environmental systems would be compromised, particularly in coastal systems where environmental conditions vary widely. In this respect, the present model also represents an advance on the previously published single-species model by Alexandridis et al (2012) on Fucus growth, primarily in its inclusion of the functional responses of carbon and nitrogen uptakes.…”

“…Saunders were dynamically modeled by Broch and Slagstad () for aquaculture, but without considering biotic interactions. Alexandridis et al () developed a first single‐species model on growth and depth distribution of Fucus in its natural environment and under various environmental conditions.…”