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  • 1
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    Elsevier
    In:  Journal of Experimental Marine Biology and Ecology, 191 (2). pp. 239-255.
    Publication Date: 2017-07-10
    Description: Interactions between epibiotic bacteria and organisms possibly play a central role in marine ecology. Despite its potential significance, this held has long time been neglected. For most aquatic taxa nothing is known about presence/absence of bacteria on their. surface, much less about specific associations or potential interactions between epibiotically associated micro- and macroorganisms. Bahamian and Pacific ascidians, most of them colonial, were screened for the presence, abundance and diversity of epibiotic bacteria and macroepibionts. Only one species, Polyclinum planum, occasionally carried macroepibionts. All ascidian species exhibited varying densities of epibiotic bacteria on their surfaces. Average epibacterial abundance as assessed by plate counts on the 29 species ranged from 60 to 1.2X10(7)/cm(2). Significant differences in bacterial abundances were observed between species, families and geographical regions. On the family level, Polyclinidae were the most densely colonized. Bahamian species exhibited less dense epibacterial communities than Pacific species, a difference that may partly be caused by the absence of the heavily fouled Polyclinidae from the Bahamian collection. Diversity of culturable strains, evaluated for the Bahamian species only, was uniformly high on most species. I did not find any evidence for specific associations (as reflected by dominance of single strains) between culturable bacteria and ascidian species. Contrarily, direct observation by epifluorescence revealed the presence of an apparently dominant photosynthetic symbiont on several didemnid species. The presence of this symbiont correlated negatively with abundance and diversity of culturable epibionts. This negative correlation could reflect properties of the host's surface which selectively favor proliferation of the symbiont or antagonistic interactions between the symbionts and other potential bacterial colonizers.
    Type: Article , PeerReviewed
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  • 2
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    Elsevier
    In:  Journal of Experimental Marine Biology and Ecology (203). pp. 245-258.
    Publication Date: 2014-01-23
    Description: The investigations focused on defence (antifouling) adaptations of seven brachyuran species from the Gulf of Thailand against epibionts (bacteria, diatoms, protozoans, macroorganisms). The species were Calappa philargius (Calappidae), Scylla serrata, Charybdis anisodon, Podophthalmus vigil (Portunidae), Hexapus anfractatus (Goneplacidae), Etisus c.f. laevimanus (Xanthidae) and Metapograpsus quadridentatus (Grapsidae). Carapaces of free living crabs were less densely colonized by organisms than other submerged living and inanimate hard substrata in the same region. The significance of potential mechanical (moulting or sloughing, grooming), physical (surface tension), chemical (surface pH, bioactive compounds), behavioural (hiding, burying, night activity) and ecological (grazing by gastropods) mechanisms was assessed. No evidence was found for an antifouling role of surface pH, toxins, surface tension or carapace grazing by gastropods. Intermoult duration was too long to explain low infestation rates although moulting eventually interrupted the colonization process. The present results indicate that behaviour patterns of the crabs are most effective mechanisms for restricting epibiont colonization. These behaviour patterns include burying in the sediment, hiding in rock crevices or below stones, night-time activity and exposure to air (intertidal species). Burying impedes epibiont access to the body surface and may cause mechanical abrasion. Nocturnal activity, as well as preference for shaded habitats reduces algal growth. Intertidal crabs are protected against the settling stages when foraging above the water line. During emersion, epibionts are also subjected to desiccation stress.
    Type: Article , PeerReviewed
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  • 3
    Publication Date: 2023-02-08
    Description: Coralline algae, a major calcifying component of coastal shallow water communities, have been shown to be one of the more vulnerable taxonomic groups to ocean acidification (OA). Under OA, the interaction between corallines and epiphytes was previously described as both positive and negative. We hypothesized that the photosynthetic activity and the complex structure of non-calcifying epiphytic algae that grow on corallines ameliorate the chemical microenvironmental conditions around them, providing protection from OA. Using mesocosm and microsensor experiments, we showed that the widespread coralline Ellisolandia elongata is less susceptible to the detrimental effects of OA when covered with non-calcifying epiphytic algae, and its diffusive boundary layer is thicker than when not covered by epiphytes. By modifying the microenvironmental carbonate chemistry, epiphytes, facilitated by OA, create micro-scale shield (and refuge) with more basic conditions that may allow the persistence of corallines associated with them during acidified conditions. Such ecological refugia could also assist corallines under near-future anthropogenic OA conditions
    Type: Article , PeerReviewed
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  • 4
    Publication Date: 2024-02-07
    Description: Highlights: • Trematodes can affect gastropods' biochemical condition and grazing rates • L. littorea fed more on invasive G. vermiculophylla than on native F. vesiculosus • Trematode-infected snails fed on average 18 % more than uninfected snails • An increase in temperature induced the mobilization of energy reserves • Trematode-induced glycogen decrease might reduce gastropod heat stress tolerance Abstract: Marine bioinvasions are of increasing attention due to their potential of causing ecological and economic loss. The seaweed Gracilaria vermiculophylla has recently invaded the Baltic Sea, where, under certain conditions, it was found to outcompete the native alga Fucus vesiculosus. Parasites of grazers and temperature are among the potential factors which might indirectly modulate the interactions between these co-occurring algae through their single and combined effects on grazing rates. We tested the temperature and parasitism effects on the feeding of the gastropod Littorina littorea on F. vesiculosus vs. G. vermiculophylla. Uninfected and trematode-infected gastropods were exposed to 10, 16, 22, and 28 center dot C for 4 days while fed with either algae. Faeces production was determined as a proxy for grazing rate, and HSP70 expression, glycogen and lipid concentrations were used to assess the gastropod's biochemical condition. Gracilaria vermiculophylla was grazed more than F. vesiculosus. Trematode infection significantly enhanced faeces production, decreased glycogen concentrations, and increased lipid concentrations in the gastropod. Warming significantly affected glycogen and lipid concentrations, with glycogen peaking at 16 center dot C and lipids at 22 center dot C. Although not significant, warming and trematode infection increased HSP70 levels. Increased faeces production in infected snails and higher faeces production by L. littorea fed with G. vermiculophylla compared to those which fed on F. vesiculosus, suggest parasitism as an important indirect modulator of the interaction between these algae. The changes in the gastropod's biochemical condition indicate that thermal stress induced the mobilization of energy reserves, suggesting a possible onset of compensatory metabolism. Finally, glycogen decrease in infected snails compared to uninfected ones might make them more susceptible to thermal stress.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 5
    Publication Date: 2024-02-07
    Description: Although parasitism is one of the most common species interactions in nature, the role of parasites in their hosts' thermal tolerance is often neglected. This study examined the ability of the trematode Podocotyle atomon to modulate the feeding and stress response of Gammarus locusta towards temperature. To accomplish this, infected and uninfected females and males of Gammarus locusta were exposed to temperatures (2, 6, 10, 14, 18, 22, 26, 30 °C) for six days. Shredding (change in food biomass) and defecation rates (as complementary measure to shredding rate) were measured as proxies for feeding activity. Lipid and glycogen concentrations (energy reserves), catalase (oxidative stress indicator), and phenoloxidase (an immunological response in invertebrates) were additionally measured. Gammarid survival was optimal at 10 °C as estimated by the linear model and was unaffected by trematode infection. Both temperature and sex influenced the direction of infection effect on phenoloxidase. Infected females presented lower phenoloxidase activity than uninfected females at 14 and 18 °C, while males remained unaffected by infection. Catalase activity increased at warmer temperatures for infected males and uninfected females. Higher activity of this enzyme at colder temperatures occurred only for infected females. Infection decreased lipid content in gammarids by 14 %. Infected males had significantly less glycogen than uninfected, while infected females showed the opposite trend. The largest infection effects were observed for catalase and phenoloxidase activity. An exacerbation of catalase activity in infected males at warmer temperatures might indicate (in the long-term) unsustainable, overwhelming, and perhaps lethal conditions in a warming sea. A decrease in phenoloxidase activity in infected females at warmer temperatures might indicate a reduction in the potential for fighting opportunistic infections. Results highlight the relevance of parasites and host sex in organismal homeostasis and provide useful insights into the organismal stability of a widespread amphipod in a warming sea.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 6
    Publication Date: 2024-03-04
    Description: Climate change is driving compositional shifts in ecological communities directly by affecting species and indirectly through changes in species interactions. For example, competitive hierarchies can be inversed when competitive dominants are more susceptible to climate change. The brown seaweed Fucus vesiculosus is a foundation species in the Baltic Sea, experiencing novel interactions with the invasive red seaweed Gracilaria vermiculophylla, which is known for its high tolerance to environmental stress. We investigated the direct and interactive effects of warming and co-occurrence of the two algal species on their performance, by applying four climate change-relevant temperature scenarios: 1) cooling ) 2 °C below ambient – representing past conditions), 2) ambient summer temperature (18 °C), 3) IPCC RCP2.6 warming scenario (1 °C above ambient), and 4) RCP8.5 warming (3 °C above ambient) for 30 days and two compositional levels (mono and co-cultured algae) in a fully-crossed design. The RCP8.5 warming scenario increased photosynthesis, respiration, and nutrients' uptake rates of mono- and co-cultured G. vermiculophylla while growth was reduced. An increase in photosynthesis and essential nutrients' uptake and, at the same time, a growth reduction might result from increasing stress and energy demand of G. vermiculophylla under warming. In contrast, the growth of mono-cultured F. vesiculosus significantly increased in the highest warming treatment (+3 °C). The cooling treatment (−2 °C) exerted a slight negative effect only on co-cultured F. vesiculosus photosynthesis, compared to the ambient treatment. Interestingly, at ambient and warming (RCP2.6 and RCP8.5 scenarios) treatments, both F. vesiculosus and G. vermiculophylla appear to benefit from the presence of each other. Our results suggest that short exposure of F. vesiculosus to moderate or severe global warming scenarios may not directly affect or even slightly enhance its performance, while G. vermiculophylla net performance (growth) could be directly hampered by warming.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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