Aquatic invertebrate diversity and distribution at the Aammiq wetland

Invertebrates are fundamental to the ecology of wetlands, as they provide a critical link between the primary producers and the higher consumers, and are essential in recycling dead plant material. They are also sensitive indicators of the health of a marsh.

The Aammiq Wetland

A survey of aquatic invertebrates was conducted at the Aammiq Wetland, Bekaa Valley, Lebanon from April to June 2002, with some additional sampling during December 2003. The main aim of the survey was to compile as complete a list as possible of the aquatic invertebrates, in order to assess aquatic biodiversity in different marsh habitats and determine the presence of any endangered, rare or endemic species. The survey had the further aim of assisting in the development of A Rocha Lebanon’s overall management plan for the wetland by identifying aquatic habitats of high invertebrate diversity and abundance.

Habitats surveyed included aquatic plant (macrophyte) beds, submerged grasses around the marsh shoreline, the edges and interior of Phragmites reed beds, isolated pools near the main marsh, and meadows that were flooded for only 2-4 weeks after winter rains. Also surveyed were macrophyte, reed edge and inner reed habitats in a nearby permanent pool. Overall, 78 invertebrate taxa were recorded, with species-level identifications possible for most of the Coleoptera (beetles) and Odonata (dragonflies and damselflies). The Coleoptera comprised 18 genera and 22 identified species, of which 9 were new records for Lebanon.

Aquatic invertebrates reached higher densities in the macrophyte, submerged grass, reed edge and isolated pools habitats than in the wet meadows, inner reeds and permanent pool habitats. Invertebrate diversity and taxonomic richness showed a very similar pattern to invertebrate density among the habitat types, except that richness in the isolated pools was lower than in the submerged grass and macrophyte habitats. This probably reflects the variety of the latter habitats in terms of width and depth, vegetation, dissolved oxygen, temperature regimes and the presence and abundance of fish predators.

Taxonomic richness per sample at each aquatic habitat type

It was clear that a diversity of habitats in the marsh leads to a diversity in the invertebrate fauna. Thus the Aammiq Wetland can be considered as a habitat mosaic, and maximum invertebrate diversity will be maintained when the marsh is managed to preserve a range of different aquatic vegetation types and hydrological characteristics. However, since some habitat types support a greater diversity and density of invertebrates than others, if maximum invertebrate productivity for the benefit of birds or other vertebrates is a management goal, then efforts may need to be directed to maximising the abundance of these habitat types.

This study provided baseline data on aquatic invertebrates of the Aammiq Wetland, and future surveys using similar techniques is strongly recommended as a way of monitoring the health of the wetland and the effects of any management practices in the Aammiq and wider Bekaa, such as an increase in water abstraction for crop irrigation.

Project leaders: Richard Storey and Andre Niewenhuijzen. Field and laboratory assistance provided by Brian Cousins.