The impacts of metalliferous drainage on aquatic communities in streams and rivers - Ecology of Industrial Pollution - page 73

General responses of macroinvertebrates to metal pollution
On the whole, macroinvertebrate communities tend to show a reduction in
biodiversity and abundance in metal-polluted sites (Schultheis et al. 1997 ;
Garc´a Criado et al. 1999 ; Gray 1998 ; Watanabe et al. 2008 ), with an increase
in the numbers of tolerant taxa (Kelly 1988 ). In one example in the UK, rivers
affected by mining and industry were found to contain severely reduced inver-
tebrate communities with only 12 taxonomic families, dominated by pollution-
tolerant species (Amisah & Cowx 2000 ). Ephemeroptera (mayflies), Trichoptera
(caddisflies) and Plecoptera (stoneflies) are often reduced in terms of abundance
and richness in metal-contaminated streams (Rutherford & Mellow 1994 ; Gray
1996a ; Beltman et al. 1999 ; Malmqvist & Hoffstein 1999 ; Courtney & Clements
2002 ;DeNicol&Stapleton 2002 ;Sol ` et al. 2004 ;Woodcock&Huryn 2005 ;Tripole
et al. 2006 ;Doiet al. 2007 ; Merricks et al. 2007 ). This observation is supported
by experimental studies in artificial streams where mayflies and stoneflies were
shown to be most sensitive to Cu and Zn and caddisflies and chironomids were
least sensitive (Hickey & Golding 2002 ). Although there is often a decrease in
species richness, abundance or density is not always affected (Beltman et al.
1999 ). This is because a reduction in diversity can allow an increase in the
numbers of tolerant taxa such as chironomids. Chironomids are known for their
resistance to high concentrations of metals (e.g., Rousch et al. 1997 ).
Studies of urban runoff identified metal-tolerant (Zn and Ni) families
as including Hydrophilidae, Asellidae, Ephemerellidae, Philoptamidae and
Chloroperlidae with metal-sensitive families being Leptophlebiidae, Ephemer-
idae, Leuctridae and Hydrobiidae (Beasley & Kneale 2003 ). Chloroperlidae,
however, were reported to be absent in the presence of Acid Mine Drainage
(AMD) in rivers in the Iberian Peninsula (Garc´a Criado et al. 1999 ), although
Leptophlebiidae were also absent. This variation in response is sometimes
noted in the literature and may be due to added effects of different metals
and acidity (see later section on metal toxicity). In addition, many authors have
identified the high degree of variation in the response of families and genera to
metals and acidity (Gower et al. 1994 ; Hickey & Golding 2002 ; Hirst et al. 2002 ;
Beasley & Kneale 2003 ; Gray & Delaney 2008 ), which makes it extremely
important to identify to species level when monitoring responses of macro-
invertebrate communities to industrial discharges.
In some isolated cases, no response has been measured in community compos-
ition and ecological function to the presence of industrial discharges such as coal
ash (Reash 2004 ), which may be due to circum-neutral pH and the low bioavail-
ability of metals (the importance of acidity is discussed later). Downstream of
discharges, there may be some evidence of recovery as dilution and removal of
metals through precipitation improves water quality, although in many cases the
entire community does not fully recover (Gray 1998 ) (see later section on recovery).