Dr Michael Jackson has studied many different aspects of shallow lake ecosystems and in particular the macroinvertebrate communities that inhabit the littoral margins of lakes.
Dr Jackson is the joint-leader of an international research team studying the effects of antifoulant paints in freshwater systems, in particular the effects of tributyltin on shallow lake ecosystems. These studies focus on the theory of Alternative Stable States and the work is being carried out in association with Dr Carl Sayer at the Environmental Change Research Centre (ECRC) at University College London, Dr Mike Waldock at the Centre for Environment, Fisheries and Aquaculture Science (CEFAS) and Dr John Boyle at the University of Liverpool. This research began with his PhD (view PDF version) studies at The University of East Anglia in southern England studying The Role of Littoral Macroinvertebrates in the Management of the Shallow Lakes of The Norfolk Broads.
Dr Jackson has also worked on lake restoration with Dr Martin Perrow and the staff of ECON, based at the University of East Anglia, in a study of the feeding habits of Eurasian perch (Perca fluviatilis) in relation to the establishment of artificial refuges in Alderfen Broad in the Norfolk Broads.
 
Alderfen Broad Artificial Refuge Experiment
Rationale:
 In healthy shallow lakes there is commonly a profusion of aquatic life with a rich diversity of aquatic plants, macroinvertebrates, fish and waterbirds. The water is usually clear for most of the year and the efficient light penetration allows a thick 'forest' of underwater vegetation to grow and flourish - this has been termed the 'vegetation-dominated clear state' (Scheffer 1989) and it is this state in which most of the Norfolk broads were found at the turn of the nineteenth century. The broads are known to have harboured at least one-sixth of the macroinvertebrate fauna of the British Isles at this time (Jackson 1997). However, during the fifties and sixties the broads were exposed to exceptionally high levels of nutrients and other pollutants that caused major changes to occur in the biota of the lakes. The water became turbid and the submersed plants were lost, the fish and bird populations decreased in diversity and the majority of the macroinvertebrates disappeared - culminating in the so-called 'non-vegetated turbid state' (Scheffer 1989).
In the turbid state the fish community consists mainly of planktivores and benthivores (e.g. cyprinids) that selectively 'hoover-up' the larger herbivorous zooplankton resulting in a dominance of cyanobacteria, characterised by frequent phytoplankton blooms. Conversely, in the clear-water state, the fish community is more diverse with a variety of piscivorous species (e.g. percids) consuming mainly planktivores and thereby releasing large zooplankton from predation and allowing phytoplankton to be kept in check (Perrow and Jowitt 1999).
Research so far has resulted in a number of large-scale management prescriptions to try to restore some of the broads to their former diversity (Moss et al 1996). These have included major changes to sewage treatment works; suction dredging of polluted sediments and biomanipulation of fish populations. Together these restoration attempts have led to clear water being achieved in a number of broads that were formerly turbid. However, a return to the highly diverse communities of the past has yet to be realised and biomanipulation has mostly failed to sustain a diverse plant, macroinvertebrate or fish community (Perrow et al 1999).
Until recently, little attention has been paid to macroinvertebrates in these restoration efforts, but new evidence suggests that their role in lake eutrophication processes may have been seriously underestimated. There is now thought to be a commensual relationship between invertebrate grazers and submerged macrophytes - the plants acting as templates for the attachment of periphyton, thus indirectly providing an important food supply for many macroinvertebrates whose grazing activities in turn prevent the plants from being shaded out (Brönmark and Vermaat 1998). In addition, there are crucial predator-prey interactions that rely to some extent on the structural complexity of the habitat. Without the structure provided by the plants, the macroinvertebrates have nowhere to shelter from predators or wave action, to feed or to reproduce. Generalised predators, such as perch, need sufficient macroinvertebrate prey to enable them to grow fast enough to complete ontogenetic dietary changes (Diehl and Kornijów 1998).
If they do not pass through these ontogenetic 'bottlenecks' the perch remain stunted and may never become piscivorous (Persson and Greenberg 1990). Without piscivorous predators such as perch the recruitment of young cyprinids is left uncontrolled and leads back to high water turbidity. Lakes with healthy perch populations had often been reported to have high water clarity with stable diverse submerged plant communities and there was growing circumstantial evidence that there was a positive correlation between the abundance of littoral vegetation and the abundance of piscivorous perch (Persson et al. 1991, 1992). Trophic cascade theory (see Carpenter & Kitchell 1993) predicted that a range of size classes of piscivorous perch acted as an effective top-down control on cyprinid fish recruitment, the effects of which would cascade down the food chain to contribute to a reduction in phytoplankton biomass. In other words, the presence of a healthy macroinvertebrates community may act as a feedback mechanism to biomanipulation and help to stabilise the system.
One problem with lake restoration attempts to date has been that a suitable macrophyte structure for macroinvertebrate colonisation may not immediately follow from biomanipulation. By providing a temporary artificial refuge for macroinvertebrate husbandry this problem ought to be partly overcome.
The Artificial Refuge:
 
Results:
Zooplankton
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Macroinvertebrates
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Conclusions:
Installation of the artificial refuge into Alderfen Broad has been highly successful in terms of zooplankton colonisation and productivity in the initial year, with a total of 15 species and 3 taxa being recorded.
The perceived role of secondary, especially zooplankton, productivity within the littoral zone of shallow lakes has generally fallen behind that of the pelagic (Lim & Fernando 1978). The larger grazing Cladocerans, Daphnia spp, can have a significant effect on phytoplankton populations, but this often depends on the nature of the fish community and the presence of macrophyte cover (Stansfield et al 1997).
In shallow lakes with perch present, the littoral zone becomes a more important feature in restoration attempts, due to the feeding behaviour and eventual top-down, regulatory function of the perch.
Increasing the area of submerged macrophyte structure, before natural colonisation happens, is one way of reversing the mechanisms that allow phytoplankton to dominate. The zooplankton community associated with the refuge in this study offer positive feedback into a reversal of poor environmental conditions.
Further monitoring for several years is clearly required of zooplankton, macroinvertebrates and the perch population, if the validity of such relationships are to be adequately concluded.
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