Academic journal article Estonian Journal of Ecology

Scale-Specific Effects of Environmental Variables on Benthic Macrophyte and Invertebrate Communities in the Vaindloo Area, the Central Gulf of Finland/Abiootilise Keskkonna Moju Pohjataimestiku Ja -Loomastiku Koosluste Ruumimustritele Soome Lahe Keskosas Vaindloo Madalal

Academic journal article Estonian Journal of Ecology

Scale-Specific Effects of Environmental Variables on Benthic Macrophyte and Invertebrate Communities in the Vaindloo Area, the Central Gulf of Finland/Abiootilise Keskkonna Moju Pohjataimestiku Ja -Loomastiku Koosluste Ruumimustritele Soome Lahe Keskosas Vaindloo Madalal

Article excerpt

INTRODUCTION

The majority of information on environmental conditions, biodiversity, and functioning of aquatic ecosystems has been derived from studies conducted at small spatial scales such as site or habitat scales whereas those performed at landscape or regional scales are much rarer. It has been suggested that at small spatial scales ecosystems are influenced by both abiotic forcing and biotic controls (Tilman et al., 1997; Loreau et al., 2001) while at large spatial scales abiotic forcing is considered a major force affecting the ecosystems (Steele & Henderson, 1994). However, there is no generic consensus among experts about the scale-specific effects of environmental variables on biota.

There may be situations in which the same variable has a negative, neutral, or positive effect on biota depending on the scale considered. For example, it is known that in marine ecosystems the coverage of boulder field may be inversely related to the presence of drift algae at the site scale whereas at the landscape scale it is positively related to drift algae (Kotta et al., 2008). Besides, relationships between abiotic and biotic factors that are evident at broad scales may disappear at finer scales and be replaced by the effects of biological processes (Greig-Smith, 1979; Woodward, 1987). Other studies, however, indicated a scale-independent relationship between environmental and biotic variables (e.g. Thrush et al., 2005). This points to the need for an assessment of scale-specific variability of biotic patterns and linkage of abiotic environment and associated biota.

Scaling in space and time is a central challenge in ecology. Earlier analyses suggest that variability in marine communities increases with scale (Platt & Denman, 1975); however, the theoretical expectation is inconsistent with many field observations (Hewitt & Thrush, 2009; Kotta & Moller, 2009). Some experimental studies investigating the relationship between environmental and species variability across different spatial scales found the lack of scale dependence to markedly different responses at different scales (Thrush et al., 2005). The degree of interaction between broad-scale factors with smaller scale variability varies among regions and is expected to determine the consistency of responses over large spatial scales. It is commonly thought, though, that local communities assemble from the macro- to the microscale, i.e. regional scale variability governs local variability rather than the other way round (Whittaker et al., 2001; Kotta & Witman, 2009). Nevertheless, small-scale processes can also generate large-scale patterns (Wootton, 2001). The knowledge on such species interaction, however, is poor and no generic scale-specific theories exist.

In the Baltic Sea the species diversity is low due to the low salinity and short evolutionary history of the sea (Russell, 1985; Wallentinus, 1991). Biotic interactions are commonly thought to have minor importance in controlling rocky shore (Waern, 1952; Kautsky & van der Maarel, 1990) and soft bottom communities (Herkul et al., 2006) whereas physical control is common (Kotta et al., 2004; Pollumae & Kotta, 2007). Large-scale distribution patterns in the Baltic Sea display a high predictability related with the scale-specific effect of abiotic factors such as salinity and depth on the community structure (Kautsky, 1993; Middelboe et al., 1997; Bonsdorff & Pearson, 1999). Locally, light availability is the major environmental factor determining the species distribution of macrophytes and benthic invertebrates associated to the plants (Kautsky & van der Maarel, 1990). In addition, geological and topological conditions may affect the availability of substrates appropriate to the species present in the region (Kautsky et al., 1999). Benthic invertebrates are locally governed by the levels of primary production in shallow areas and intensity of hypoxia in deep areas (Bonsdorff & Pearson, 1999; Kotta et al. …

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