Patterns in the epilithic community of a lake littoral

Abstract

1. The algae and sedentary macroinvertebrates on the upper surface of stones from the littoral of Crosemere were investigated over 13 months. This lake is one of a series of eutrophic meres of glacial origin in the English Midlands. 2. Stones were taken from shallow and deep areas in the littoral and from areas shaded by bankside trees and those away from trees. This gave four habitat types: open/shallow; open/deep; shade/shallow; shade/deep. Epilithic algae and sedentary macroinvertebrates from the upper surfaces of the stones were quantified monthly for each habitat type. 3. Chlorophyll a and ash‐free dry mass both showed a strong seasonal pattern common to all habitat types, with a spring peak declining to a summer minimum, followed by a small autumn recovery, and a winter minimum. 4. In terms of percentage cover, Cladophora glomerata showed a markedly different pattern. There were strong differences between habitat types, with shaded stones from the shallows, in particular, having very sparse Cladophora cover. In the open, Cladophora cover was high in summer and low at other times. 5. The invertebrate community was dominated by retreat‐dwelling larvae of the psychomyiid caddis, Tinodes waeneri, and four species of chironomids with tube‐building larvae, Cricotopus sylvestris, Microtendipes pedellus, Glyptotendipes pallens and Endochironomus albipennis. For Tinodes, Cricotopus and Microtendipes, peaks of density occurred chiefly beneath trees in spring and summer. 6. The seasonal pattern of algal abundance showed little relationship with that of invertebrate biomass. The ratio of chlorophyll a to ash‐free dry mass also declined in summer, despite the higher invertebrate biomass. This indicated that grazing was not the dominant factor diminishing algal abundance seasonally. It seems likely that algae were limited chiefly by physical factors, such as light and temperature, and by nutrients, particularly nitrates, which decline in summer in the epilimnion of the lake. 7. Grazing may have contributed to spatial patchiness of algae in summer, however, particularly that of Cladophora. The scarcity of Cladophora on shallow, shaded stones coincided with a high abundance of Tinodes on these stones in early summer. Riparian trees could thus have affected epilithic algae, not only by shading but also indirectly through the supply of grazers.

The use of littoral mesohabitats and their macroinvertebrate assemblages in the ecological assessment of lakes

“…This study did not support suggestions that the littoral zone of lakes is too heterogeneous for the collection of meaningful macroinvertebrate samples (Rasmussen, 1988;Johnes et al, 1996;Harrison and Hildrew, 1998;Koskenniemi, 2000). This does not mean that habitat heterogeneity within the littoral zone of lakes is not important, but that, at least across the lakes studied, overall variation of macroinvertebrate communities was greater among than within lakes.…”

“…The lack of understanding of fundamental relationships in the littoral zones of lakes is striking, and surprising, given the vast literature on macroinvertebrate communities in rivers. It has been argued (Rasmussen, 1988;Johnes et al, 1996;Harrison and Hildrew, 1998;Koskenniemi, 2000) that the inherent heterogeneity of habitats in the littoral of lakes prevents meaningful use of invertebrate communities for ecological assessment.…”

A test of the association between Lake Habitat Quality Assessment and macroinvertebrate community structure

“…Disturbance of the riparian zone, caused by erosion, deposition, inundation and desiccation, contribute, furthermore, to spatial heterogeneity of the ecotone (Giudicelli and Bournaud, 1997). Bankside vegetation has been found to be important for distribution and abundance both of macroinvertebrate larvae and their adult terrestrial phase in streams and rivers (Harrison and Hildrew, 1998). The more structurally complex marginal macrophytes may also provide numerous sites for insect pupation, emergence and oviposition, leading to a greater supply of recruits to all habitats (Harrison and Harris, 2002).…”

Colonisation of temporary macrophyte substratum by midges (Chironomidae: Diptera)

“…The second most abundant species was E. albipennis. This bivoltine species is phytophylous and commonly found in eutrophic lakes (Harrison and Hildrew, 1998;Brodersen et al, 2001;Kumari et al, 2007). E. albipennis is known to be feeding on detritus or macrophyte tissue (Armitage et al, 1995;Kornijo´w et al, 1995) while Walsh (1951) determined it's ability to filter-feed even when oxygen concentration is low.…”