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  • 1
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    Patterns of diversity along experimental gradients of disturbance and nutrient supply - the confounding assumptions of the Intermediate Disturbance Hypothesis (2010)
    Taylor & Francis
    In:  African Journal of Marine Science, 32 (1). pp. 127-135.
    Details
    Publication Date: 2019-01-21
    Description: A model of the interactive effects of disturbance and productivity on diversity predicts peak diversity to shift towards higher disturbance regimes as productivity increases, confining the Intermediate Disturbance Hypothesis to intermediate productivity levels. We conducted a two-factorial (disturbance, nutrients) field experiment to test the validity of this model for two subtropical intertidal rocky shores. Treatment responses varied between distinct community types at two sites. Intensified disturbance increased evenness, and under high nutrient enrichment decreased species richness of communities dominated by encrusting algae, whereas turf-dominated communities remained unaffected. Nutrient additions increased biomass and modulated community composition at both sites, in addition to increasing species richness in encrusting-algal and decreasing evenness of turf-forming assemblages. Thus, only highly enriched encrusting-algal communities followed the model predictions. Different mechanisms appear to control species coexistence in different types of communities, some violating the assumptions of the tested model, i.e. resource limitation and competitive exclusion.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.2989/18142321003714856
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Decreased depth distribution of Fucus vesiculosus (Phaeophyceae) in the Western Baltic: effects of light deficiency and epibionts on growth and photosynthesis (2008)
    Taylor & Francis
    In:  European Journal of Phycology, 43 (2). pp. 143-150.
    Details
    Publication Date: 2017-01-04
    Description: For many coastal areas of the world, a decrease in abundance and depth penetration of perennial macroalgae and seagrasses has been documented and attributed to eutrophication. A surplus of nutrients impairs perennial seaweeds in at least two ways: increased phytoplankton densities reduce the depth penetration of light and in addition filamentous seaweeds and microalgae growing epiphytically shade their perennial hosts. A reduction of depth limit and total abundance has also been observed for the brown seaweed Fucus vesiculosus at many sites in the Baltic Sea. However, in most cases the mechanistic reason for the loss of Fucus has been deduced from observations rather than from experimental evidence. Here, we present results of a two-factorial (water depth/light supply and epibionts) experiment that was run in the Kiel Fjord, western Baltic, from August to October 2005. Performance of F. vesiculosus was recorded by growth and chlorophyll measurements, PI-curves and in situ measurements of the photosynthetic activity as the relative rate of electron transport (rETR). rETR and growth decreased with water depth. Chlorophyll a concentrations increased with reduced light intensities, but this apparently could not compensate for the light deficiency. Epibionts enhanced the negative effect of reduced light conditions on growth. According to these findings we estimated the physiological depth limit of F. vesiculosus in the Kiel Fjord to lie between 4 and 6 m water depth.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1080/09670260801901018
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Salinity Driven Selection and Local Adaptation in Baltic Sea Mytilid Mussels (2021)
    Frontiers
    Details
    Publication Date: 2024-02-07
    Description: Baltic blue mussels can colonise and dominate habitats with far lower salinity (〈 10 psu) than other Mytilus congeners. Pervasive gene flow was observed between Western Baltic Mytilus edulis living at high salinity conditions and Eastern Baltic M. trossulus living at lower salinites, with highest admixture proportions within a genetic transition zone located at intermediate salinities (Darss Sill area). Yet, we do not understand the impacts of low salinity on larval performance, and how salinity may act as an early selective pressure during passive larval drift across salinity gradients. This study tested whether larvae originating from two different populations along the natural salinity cline in the Baltic Sea have highest fitness at their native salinities. Our results suggest that Eastern Baltic M. trossulus (Usedom, 7 psu) and Western Baltic M. edulis (Kiel, 16 psu) larvae display better performance (fitness components: growth, mortality, settlement success) when reared at their respective native salinities. This suggests that these populations are adapted to their local environment. Additionally, species diagnostic markers were used for genetic analyses of transition zone (Ahrenshoop, 11 psu) mussel larvae exposed to low salinity. This revealed that low salinity selection resulted in a shift towards allele frequencies more typical for Eastern Baltic M. trossulus. Thus, salinity acts as a selective pressure during the pre-settlement phase and can shape the genetic composition of Baltic mussel populations driving local adaptation to low salinity. Future climate change driven desalination, therefore, has the potential to shift the Baltic Sea hybrid gradient westward with consequences for benthic ecosystem structure.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Capacity for Cellular Osmoregulation Defines Critical Salinity of Marine Invertebrates at Low Salinity (2022)
    Frontiers
    Details
    Publication Date: 2024-02-07
    Description: Low-salinity stress can severely affect the fitness of marine organisms. As desalination has been predicted for many coastal areas with ongoing climate change, it is crucial to gain more insight in mechanisms that constrain salinity acclimation ability. Low-salinity induced depletion of the organic osmolyte pool has been suggested to set a critical boundary in osmoconforming marine invertebrates. Whether inorganic ions also play a persistent role during low-salinity acclimation processes is currently inconclusive. We investigated the salinity tolerance of six marine invertebrate species following a four-week acclimation period around their low-salinity tolerance threshold. To obtain complete osmolyte budgets, we quantified organic and inorganic osmolytes and determined fitness proxies. Our experiments corroborated the importance of the organic osmolyte pool during low-salinity acclimation. Methylamines constituted a large portion of the organic osmolyte pool in molluscs, whereas echinoderms exclusively utilized free amino acids. Inorganic osmolytes were involved in long-term cellular osmoregulation in most species, thus are not just modulated with acute salinity stress. The organic osmolyte pool was not depleted at low salinities, whilst fitness was severely impacted. Instead, organic and inorganic osmolytes often stabilized at low-salinity. These findings suggest that low-salinity acclimation capacity cannot be simply predicted from organic osmolyte pool size. Rather, multiple parameters (i.e. osmolyte pools, net growth, water content and survival) are necessary to establish critical salinity ranges. However, a quantitative knowledge of cellular osmolyte systems is key to understand the evolution of euryhalinity and to characterize targets of selection during rapid adaptation to ongoing desalination.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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