Quantitative distribution of plant and animal communities of the phytobenthic zone in the Baltic Sea

Source: OAI

ABSTRACT Contributions from the Askö laboratory ; 35 Pages: 80 p. : ill., graphs This paper quantitatively describes flora and fauna communities in the central and northern Baltic Sea, on vegetation covered substrate down to maximum 25 m depth, investigated by SCUBA-technique. In the Holmö area, on the sill between the Bothnian Bay and the Bothnian Sea, biomass was characterized by annual, mainly freshwater algae (e.g. Cladophora spp.) growing on the predominantly hard substrate of boulders, stones and pebbles. Muddy substrate, occurring in the shallow bays, had low biomass of freshwater phanerogams. The fauna biomass was dominated by freshwater molluscs (mainly Theodoxus fluviatilis L.) and the isopod Mesidothea entomon L.. Occasionally, Macoma balthica L. was abundant on sand and mud bottoms. Insect larvae were common but contributed little to total animal biomass.

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    • "In Kronören, samples were taken at a depth of approximately 4 m and in Askö at 0.4 m. The greater sampling depth in Kronören was used due to the lack of perennial species in shallow areas, which is a result of the 4 months of ice cover every year (Kautsky, 1989), when ice scrapes off the large perennial fucoids. Hence, it is only at greater depths (3e4 m) that Fucus radicans is belt forming, reaching a cover of 25e75%. "
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    ABSTRACT: Anthropogenic activities worldwide have contributed to vegetation changes in many coastal areas, changes that may in turn affect faunal and algal assemblages in the involved ecosystems. In the northernmost part of the Baltic Sea the salinity is extremely low (3–4) and the only structurally complex alga present is Fucus radicans. Since in this area F. radicans is living at its salinity tolerance limit, it is potentially very sensitive to environmental changes. Any change in salinity could thus alter the overall algal community, changing it to one dominated solely by filamentous algae. To determine the importance of F. radicans to the associated faunal community, we examined differences between the 2 main vegetation types present, i.e., F. radicans and filamentous algae, in the Kronören marine reserve in the northernmost part of the Baltic Sea. A similar study was conducted in the Askö area in the northern Baltic Proper, where the more-investigated Fucus vesiculosus is the only large fucoid present. The biomass of associated fauna was significantly higher in both the F. radicans and F. vesiculosus than in the filamentous algal vegetation at some, but not all, sites. The F. radicans community also displayed a greater diversity of associated fauna in 3 of 5 investigated Kronören sites, whereas no difference in diversity was detected between F. vesiculosus and the filamentous algal vegetations in the Askö sites. Furthermore, the F. radicans community displayed a different faunal community, being the only investigated algal community with a faunal community dominated by K-strategy species, according to abundance–biomass comparison curves. This pattern may be due to the low epiphytic load on these Fucus plants. In contrast, the F. vesiculosus community, as well as the algal communities with no Fucus in both areas, had high biomasses of filamentous algae and an invertebrate fauna dominated by Chironomidae, occurring in great abundance but only with a low biomass. ANOSIM analyses of faunal composition demonstrated a significant difference between the 2 vegetation types in both areas, largely due to greater abundance of Gammarus spp. and Theodoxus fluviatilis in the fucoid vegetation. Differences observed between the F. radicans and filamentous algal vegetation types were generally more pronounced than those between F. vesiculosus and nearby filamentous algal vegetation. These observations may be due to abiotic factors that differ between the 2 investigated areas, factors such as depth distribution, wave action and eutrophication level. This study has demonstrated that the less-investigated F. radicans may be as important as the larger F. vesiculosus for the associated faunal assemblages. At the same time, the limited extent of F. radicans at shallower depths makes F. radicans vegetation potentially more vulnerable to anthropogenic changes, as declines in fucoid vegetation are usually first manifested in populations at their lower depth limits, whereas shallow populations are less affected.
    Estuarine Coastal and Shelf Science 06/2007; 73(1):249-258. DOI:10.1016/j.ecss.2007.01.005 · 2.06 Impact Factor
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    • "Pooling primarily improved the fit of ephemeral algae to the CCA model, while the fit of perennials was already generally high. Ephemeral algae are probably more stochastic in their occurrence than perennial algae (Kautsky, 1989; Kiirikki and Blomster, 1996; Kiirikki and Lehvo, 1997), but the results may also reflect possible physical interference from Fucus vesiculosus on its surrounding. Although F. vesiculosus Table 5 Correlation between environmental variables and the two first ordination axes obtained by redundancy analyses of community structure at four separate depths (inter-set correlation coefficients) "
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    ABSTRACT: The relationship between macroalgal assemblages and abiotic factors was quantified by gradient analyses in an area where long-term changes in macroalgal depth distributions have previously been documented. Biomass data from 4, 6, 8 and 10 m depth in an area of similar salinity (5) and substrate (rock) in the northern Baltic Proper was constrained by a set of environmental variables defining different aspects of abiotic control of species distributions (sediment cover, effective fetch, clarity index, the curvature and slope of the bottom, and direction of exposure) in multivariate analyses at different scales. Fucus vesiculosus dominated the biomass at 4, 6 and 8 m depth, and Furcellaria lumbricalis at 10 m. The applied models explained 30.7–53.3% of the total variance in community structure, and 49.3–60.9% when analysed separately for each depth. A separate analysis of species depth distributions demonstrated that effective fetch was most strongly related to upper limits of the algal belts, sediment cover to the lower limit and density of the F. vesiculosus belt, and clarity index to the lower limits of F. vesiculosus, perennial red algae, and of the red algal and Sphacelaria spp. belts. The results show a strong correlation between environmental variables and vegetation structure even on a small, local scale in the northern Baltic Proper, indicating a high suitability of the phytobenthic zone for environmental monitoring. The results add to previous studies that show a strong importance of abiotic factors on large-scale variation in phytobentic community composition in the Baltic Sea.
    Estuarine Coastal and Shelf Science 01/2005; 62(1-62):109-117. DOI:10.1016/j.ecss.2004.08.009 · 2.06 Impact Factor
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